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2726 KiB

Open AccessArticle

Control Strategies to Smooth Short-Term Power Fluctuations in Large Photovoltaic Plants Using Battery Storage Systems

by Javier Marcos, Iñigo De la Parra, Miguel García and Luis Marroyo

Energies 2014, 7(10), 6593-6619; https://doi.org/10.3390/en7106593 - 16 Oct 2014

Cited by 116 | Viewed by 11029

Abstract

The variations in irradiance produced by changes in cloud cover can cause rapid fluctuations in the power generated by large photovoltaic (PV) plants. As the PV power share in the grid increases, such fluctuations may adversely affect power quality and reliability. Thus, energy [...] Read more.

The variations in irradiance produced by changes in cloud cover can cause rapid fluctuations in the power generated by large photovoltaic (PV) plants. As the PV power share in the grid increases, such fluctuations may adversely affect power quality and reliability. Thus, energy storage systems (ESS) are necessary in order to smooth power fluctuations below the maximum allowable. This article first proposes a new control strategy (step-control), to improve the results in relation to two state-of-the-art strategies, ramp-rate control and moving average. It also presents a method to quantify the storage capacity requirements according to the three different smoothing strategies and for different PV plant sizes. Finally, simulations shows that, although the moving-average (MA) strategy requires the smallest capacity, it presents more losses (2–3 times more) and produces a much higher number of cycles over the ESS (around 10 times more), making it unsuitable with storage technologies as lithium-ion. The step-control shown as a better option in scenery with exigent ramp restrictions (around 2%/min) and distributed generation against the ramp-rate control in all ESS key aspects: 20% less of capacity, up to 30% less of losses and a 40% less of ageing. All the simulations were based on real PV production data, taken every 5 s in the course of one year (2012) from a number of systems with power outputs ranging from 550 kW to 40 MW. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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1794 KiB

Open AccessArticle

Multi-Faceted Assessment of a Wireless Communications Infrastructure for the Green Neighborhoods of the Smart Grid

by Gregorio López, Pedro Moura, José Ignacio Moreno and José Manuel Camacho

Energies 2014, 7(5), 3453-3483; https://doi.org/10.3390/en7053453 - 22 May 2014

Cited by 24 | Viewed by 10236

Abstract

Reducing electricity consumption and integrating renewable power generation sources represent two of the main drivers of the so-called Smart Grid. Machine-to-Machine (M2M) communications will play a key role on making such a Smart Grid a reality, since they will enable the required bidirectional [...] Read more.

Reducing electricity consumption and integrating renewable power generation sources represent two of the main drivers of the so-called Smart Grid. Machine-to-Machine (M2M) communications will play a key role on making such a Smart Grid a reality, since they will enable the required bidirectional real-time bulk information exchange. However, communications for the Smart Grid present specific requirements from both technical and economic perspectives, so it is crucial to evaluate how existing communication architectures and technologies meet them before undertaking the important investments needed to deploy this kind of infrastructure on a large scale. The main goal of this paper is to evaluate, from different perspectives, the core M2M communications infrastructure of a platform designed to reduce electricity consumption and integrate renewable generation at residential level. Such a communications infrastructure is fully based on widely deployed wireless communications technologies such as IEEE 802.11 and General Packet Radio Service (GPRS). Notably, the paper assesses the operational costs of using different security solutions in the GPRS segment and the performance of the selected communications technologies based on different metrics (goodput, in the case of IEEE 802.11, and transmission time, in the case of GPRS). Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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590 KiB

Open AccessArticle

Valuation of Wind Energy Projects: A Real Options Approach

by Luis M. Abadie and José M. Chamorro

Energies 2014, 7(5), 3218-3255; https://doi.org/10.3390/en7053218 - 19 May 2014

Cited by 43 | Viewed by 9021

Abstract

We address the valuation of an operating wind farm and the finite-lived option to invest in it under different reward/support schemes: a constant feed-in tariff, a premium on top of the electricity market price (either a fixed premium or a variable subsidy such [...] Read more.

We address the valuation of an operating wind farm and the finite-lived option to invest in it under different reward/support schemes: a constant feed-in tariff, a premium on top of the electricity market price (either a fixed premium or a variable subsidy such as a renewable obligation certificate or ROC), and a transitory subsidy, among others. Futures contracts on electricity with ever longer maturities enable market-based valuations to be undertaken. The model considers up to three sources of uncertainty: the electricity price, the level of wind generation, and the certificate (ROC) price where appropriate. When analytical solutions are lacking, we resort to a trinomial lattice combined with Monte Carlo simulation; we also use a two-dimensional binomial lattice when uncertainty in the ROC price is considered. Our data set refers to the UK. The numerical results show the impact of several factors involved in the decision to invest: the subsidy per MWh generated, the initial lump-sum subsidy, the maturity of the investment option, and electricity price volatility. Different combinations of variables can help bring forward investments in wind generation. One-off policies, e.g., a transitory initial subsidy, seem to have a stronger effect than a fixed premium per MWh produced. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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2077 KiB

Open AccessArticle

Autoregressive with Exogenous Variables and Neural Network Short-Term Load Forecast Models for Residential Low Voltage Distribution Networks

by Christopher Bennett, Rodney A. Stewart and Junwei Lu

Energies 2014, 7(5), 2938-2960; https://doi.org/10.3390/en7052938 - 30 Apr 2014

Cited by 67 | Viewed by 9448

Abstract

This paper set out to identify the significant variables which affect residential low voltage (LV) network demand and develop next day total energy use (NDTEU) and next day peak demand (NDPD) forecast models for each phase. The models were developed using both autoregressive [...] Read more.

This paper set out to identify the significant variables which affect residential low voltage (LV) network demand and develop next day total energy use (NDTEU) and next day peak demand (NDPD) forecast models for each phase. The models were developed using both autoregressive integrated moving average with exogenous variables (ARIMAX) and neural network (NN) techniques. The data used for this research was collected from a LV transformer serving 128 residential customers. It was observed that temperature accounted for half of the residential LV network demand. The inclusion of the double exponential smoothing algorithm, autoregressive terms, relative humidity and day of the week dummy variables increased model accuracy. In terms of R² and for each modelling technique and phase, NDTEU hindcast accuracy ranged from 0.77 to 0.87 and forecast accuracy ranged from 0.74 to 0.84. NDPD hindcast accuracy ranged from 0.68 to 0.74 and forecast accuracy ranged from 0.56 to 0.67. The NDTEU models were more accurate than the NDPD models due to the peak demand time series being more variable in nature. The NN models had slight accuracy gains over the ARIMAX models. A hybrid model was developed which combined the best traits of the ARIMAX and NN techniques, resulting in improved hindcast and forecast fits across the all three phases. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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746 KiB

Open AccessArticle

Enabling Privacy in Vehicle-to-Grid Interactions for Battery Recharging

by Cristina Rottondi, Simone Fontana and Giacomo Verticale

Energies 2014, 7(5), 2780-2798; https://doi.org/10.3390/en7052780 - 25 Apr 2014

Cited by 26 | Viewed by 8052

Abstract

The diffusion of Electric Vehicles (EV) fostered by the evolution of the power system towards the new concept of Smart Grid introduces several technological challenges related to the synergy among electricity-propelled vehicle fleets and the energy grid ecosystem. EVs promise to reduce carbon [...] Read more.

The diffusion of Electric Vehicles (EV) fostered by the evolution of the power system towards the new concept of Smart Grid introduces several technological challenges related to the synergy among electricity-propelled vehicle fleets and the energy grid ecosystem. EVs promise to reduce carbon emissions by exploiting Renewable Energy Sources (RESes) for battery recharge, and could potentially serve as storage bank to flatten the fluctuations of power generation caused by the intermittent nature of RESes by relying on a load aggregator, which intelligently schedules the battery charge/discharge of a fleet of vehicles according to the users’ requests and grid’s needs. However, the introduction of such vehicle-to-grid (V2G) infrastructure rises also privacy concerns: plugging the vehicles in the recharging infrastructures may expose private information regarding the user’s locations and travelling habits. Therefore, this paper proposes a privacy-preserving V2G infrastructure which does not disclose to the aggregator the current battery charge level, the amount of refilled energy, nor the time periods in which the vehicles are actually plugged in. The communication protocol relies on the Shamir Secret Sharing threshold cryptosystem. We evaluate the security properties of our solution and compare its performance to the optimal scheduling achievable by means of an Integer Linear Program (ILP) aimed at maximizing the ratio of the amount of charged/discharged energy to/from the EV’s batteries to the grid power availability/request. This way, we quantify the reduction in the effectiveness of the scheduling strategy due to the preservation of data privacy. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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493 KiB

Open AccessArticle

Fast Cut Back Thermal Power Plant Load Rejection and Black Start Field Test Analysis

by Kaiwen Zeng, Jinyu Wen, Longpeng Ma, Shijie Cheng, En Lu and Ning Wang

Energies 2014, 7(5), 2740-2760; https://doi.org/10.3390/en7052740 - 25 Apr 2014

Cited by 11 | Viewed by 12179

Abstract

Fast and reliable black start plays a key role in improving the ability of the power system to resist the risk of large-scale blackouts. For a black start with high voltage and long-distance transmission lines, it is much easier to cause phenomena such [...] Read more.

Fast and reliable black start plays a key role in improving the ability of the power system to resist the risk of large-scale blackouts. For a black start with high voltage and long-distance transmission lines, it is much easier to cause phenomena such as self-excitation and power frequency/operating overvoltage, which may lead to black start failure and impact the reliability of the system’s restoration. Meanwhile, the long time needed to crank up the non-black start units will impact the speed of the restoration. This paper addresses the advantages of using a thermal power unit with a fast cut back (FCB) function as a black start unit, and studies the transient process of the FCB unit during the restoration. Firstly, key problems in the power system black start process are analyzed and a practical engineering criterion of self-excitation is proposed. Secondly, the dynamic model of the FCB unit is presented. Thirdly, the field test of the FCB unit load rejection and black start is introduced, which is the first successful field test of black start with 500 kV long-distance lines in China Southern Power Grid (CSG). Finally, the transient process of this test is simulated using the PSCAD/EMTDC software, and the simulation results accord well with the field test results, which verifies the correctness of the FCB model and the self-excitation engineering criterion proposed. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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660 KiB

Open AccessArticle

Fault Detection and Location by Static Switches in Microgrids Using Wavelet Transform and Adaptive Network-Based Fuzzy Inference System

by Ying-Yi Hong, Yan-Hung Wei, Yung-Ruei Chang, Yih-Der Lee and Pang-Wei Liu

Energies 2014, 7(4), 2658-2675; https://doi.org/10.3390/en7042658 - 23 Apr 2014

Cited by 38 | Viewed by 10379

Abstract

Microgrids are a highly efficient means of embedding distributed generation sources in a power system. However, if a fault occurs inside or outside the microgrid, the microgrid should be immediately disconnected from the main grid using a static switch installed at the secondary [...] Read more.

Microgrids are a highly efficient means of embedding distributed generation sources in a power system. However, if a fault occurs inside or outside the microgrid, the microgrid should be immediately disconnected from the main grid using a static switch installed at the secondary side of the main transformer near the point of common coupling (PCC). The static switch should have a reliable module implemented in a chip to detect/locate the fault and activate the breaker to open the circuit immediately. This paper proposes a novel approach to design this module in a static switch using the discrete wavelet transform (DWT) and adaptive network-based fuzzy inference system (ANFIS). The wavelet coefficient of the fault voltage and the inference results of ANFIS with the wavelet energy of the fault current at the secondary side of the main transformer determine the control action (open or close) of a static switch. The ANFIS identifies the faulty zones inside or outside the microgrid. The proposed method is applied to the first outdoor microgrid test bed in Taiwan, with a generation capacity of 360.5 kW. This microgrid test bed is studied using the real-time simulator eMegaSim developed by Opal-RT Technology Inc. (Montreal, QC, Canada). The proposed method based on DWT and ANFIS is implemented in a field programmable gate array (FPGA) by using the Xilinx System Generator. Simulation results reveal that the proposed method is efficient and applicable in the real-time control environment of a power system. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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1183 KiB

Open AccessArticle

A Wide-Area Measurement Systems-Based Adaptive Strategy for Controlled Islanding in Bulk Power Systems

by Honglei Song, Junyong Wu and Kui Wu

Energies 2014, 7(4), 2631-2657; https://doi.org/10.3390/en7042631 - 23 Apr 2014

Cited by 17 | Viewed by 8790

Abstract

Controlled islanding is the last countermeasure for a bulk power system when it suffers from severe cascading contingencies. The objective of controlled islanding is to maintain the stability of each island and to keep the total loss of loads of the whole system [...] Read more.

Controlled islanding is the last countermeasure for a bulk power system when it suffers from severe cascading contingencies. The objective of controlled islanding is to maintain the stability of each island and to keep the total loss of loads of the whole system to a minimum. This paper presents a novel integrated wide-area measurement systems (WAMS)-based adaptive controlled islanding strategy, which depends on the dynamic post-fault trajectories under different failure modes. We first utilize an improved Laplacian eigenmap algorithm (ILEA) to identify the coherent generators and use the slow coherency grouping algorithm to guarantee coherent stability within an island. Using the identification result, we then define the minimum coherent generator virtual nodes to reduce the searching space in a graph and utilize the k-way partitioning (KWP) algorithm to obtain a preliminary partition of the simplified graph. Based on the preliminary partition, we consider the direction of power flow and propose a variable neighborhood heuristic searching algorithm to search the optimal separation surfaces so that the net imbalanced power of islands is minimized. Finally, the bidirectional power flow tracing algorithm and PQ decomposition power flow analysis are utilized to determine the corrective controls within each island. The test results with the New England 39-bus system and the IEEE 118-bus system show that the proposed integrated controlled islanding strategy can automatically adapt to different fault modes through generator coherency identification and effectively group the different coherent generators into different islands. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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1076 KiB

Open AccessArticle

Design of a Control Scheme for Distribution Static Synchronous Compensators with Power-Quality Improvement Capability

by Pedro Roncero-Sànchez and Enrique Acha

Energies 2014, 7(4), 2476-2497; https://doi.org/10.3390/en7042476 - 22 Apr 2014

Cited by 13 | Viewed by 9362

Abstract

Electric power systems are among the greatest achievements of the last century. Today, important issues, such as an ever-increasing demand, the flexible and reliable integration of distributed generation or a growth in disturbing loads, must be borne in mind. In this context, smart [...] Read more.

Electric power systems are among the greatest achievements of the last century. Today, important issues, such as an ever-increasing demand, the flexible and reliable integration of distributed generation or a growth in disturbing loads, must be borne in mind. In this context, smart grids play a key role, allowing better efficiency of power systems. Power electronics provides solutions to the aforementioned matters, since it allows various energy sources to be integrated into smart grids. Nevertheless, the design of the various control schemes that are necessary for the correct operation of the power-electronic interface is a very important issue that must always be taken into consideration. This paper deals with the design of the control system of a distribution static synchronous compensator (DSTATCOM) based on flying-capacitor multilevel converters. The control system is tailored to compensate for both voltage sags by means of reactive-power injection and voltage imbalances caused by unbalanced loads. The design of the overall control is carried out by using the root-locus and frequency-response techniques, improving both the transient response and the steady-state error of the closed-loop system. Simulation results obtained using PSCADTM/EMTDCTM (Manitoba Hydro International Ltd., Commerce Drive, Winnipeg, MB, Canada) show the resultant voltage regulation. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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6358 KiB

Open AccessArticle

Priority-Based Hierarchical Operational Management for Multiagent-Based Microgrids

by Takumi Kato, Hideyuki Takahashi, Kazuto Sasai, Gen Kitagata, Hak-Man Kim and Tetsuo Kinoshita

Energies 2014, 7(4), 2051-2078; https://doi.org/10.3390/en7042051 - 31 Mar 2014

Cited by 12 | Viewed by 8451

Abstract

Electricity consumption in the world is constantly increasing, making our lives become more and more dependent on electricity. There are several new paradigms proposed in the field of power grids. In Japan, especially after the Great East Japan Earthquake in March 2011, the [...] Read more.

Electricity consumption in the world is constantly increasing, making our lives become more and more dependent on electricity. There are several new paradigms proposed in the field of power grids. In Japan, especially after the Great East Japan Earthquake in March 2011, the new power grid paradigms are expected to be more resilient to survive several difficulties during disasters. In this paper, we focus on microgrids and propose priority-based hierarchical operational management for multiagent-based microgrids. The proposed management is a new multiagent-based load shedding scheme and multiagent-based hierarchical architecture to realize such resilient microgrids. We developed a prototype system and performed an evaluation of the proposed management using the developed system. The result of the evaluation shows the effectiveness of our proposal in power shortage situations, such as disasters. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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565 KiB

Open AccessArticle

Stochastic Modeling and Optimization in a Microgrid: A Survey

by Hao Liang and Weihua Zhuang

Energies 2014, 7(4), 2027-2050; https://doi.org/10.3390/en7042027 - 31 Mar 2014

Cited by 170 | Viewed by 14790

Abstract

The future smart grid is expected to be an interconnected network of small-scale and self-contained microgrids, in addition to a large-scale electric power backbone. By utilizing microsources, such as renewable energy sources and combined heat and power plants, microgrids can supply electrical and [...] Read more.

The future smart grid is expected to be an interconnected network of small-scale and self-contained microgrids, in addition to a large-scale electric power backbone. By utilizing microsources, such as renewable energy sources and combined heat and power plants, microgrids can supply electrical and heat loads in local areas in an economic and environment friendly way. To better adopt the intermittent and weather-dependent renewable power generation, energy storage devices, such as batteries, heat buffers and plug-in electric vehicles (PEVs) with vehicle-to-grid systems can be integrated in microgrids. However, significant technical challenges arise in the planning, operation and control of microgrids, due to the randomness in renewable power generation, the buffering effect of energy storage devices and the high mobility of PEVs. The two-way communication functionalities of the future smart grid provide an opportunity to address these challenges, by offering the communication links for microgrid status information collection. However, how to utilize stochastic modeling and optimization tools for efficient, reliable and economic planning, operation and control of microgrids remains an open issue. In this paper, we investigate the key features of microgrids and provide a comprehensive literature survey on the stochastic modeling and optimization tools for a microgrid. Future research directions are also identified. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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303 KiB

Open AccessArticle

Economic Scheduling of Residential Plug-In (Hybrid) Electric Vehicle (PHEV) Charging

by Maigha and Mariesa L. Crow

Energies 2014, 7(4), 1876-1898; https://doi.org/10.3390/en7041876 - 25 Mar 2014

Cited by 27 | Viewed by 7648

Abstract

In the past decade, plug-in (hybrid) electric vehicles (PHEVs) have been widely proposed as a viable alternative to internal combustion vehicles to reduce fossil fuel emissions and dependence on petroleum. Off-peak vehicle charging is frequently proposed to reduce the stress on the electric [...] Read more.

In the past decade, plug-in (hybrid) electric vehicles (PHEVs) have been widely proposed as a viable alternative to internal combustion vehicles to reduce fossil fuel emissions and dependence on petroleum. Off-peak vehicle charging is frequently proposed to reduce the stress on the electric power grid by shaping the load curve. Time of use (TOU) rates have been recommended to incentivize PHEV owners to shift their charging patterns. Many utilities are not currently equipped to provide real-time use rates to their customers, but can provide two or three staggered rate levels. To date, an analysis of the optimal number of levels and rate-duration of TOU rates for a given consumer demographic versus utility generation mix has not been performed. In this paper, we propose to use the U.S. National Household Travel Survey (NHTS) database as a basis to analyze typical PHEV energy requirements. We use Monte Carlo methods to model the uncertainty inherent in battery state-of-charge and trip duration. We conclude the paper with an analysis of a different TOU rate schedule proposed by a mix of U.S. utilities. We introduce a centralized scheduling strategy for PHEV charging using a genetic algorithm to accommodate the size and complexity of the optimization. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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2918 KiB

Open AccessArticle

Development and Field Test of a Real-Time Database in the Korean Smart Distribution Management System

by Sang-Yun Yun and Joon-Ho Choi

Energies 2014, 7(4), 1852-1875; https://doi.org/10.3390/en7041852 - 25 Mar 2014

Cited by 3 | Viewed by 7612

Abstract

Recently, a distribution management system (DMS) that can conduct periodical system analysis and control by mounting various applications programs has been actively developed. In this paper, we summarize the development and demonstration of a database structure that can perform real-time system analysis and [...] Read more.

Recently, a distribution management system (DMS) that can conduct periodical system analysis and control by mounting various applications programs has been actively developed. In this paper, we summarize the development and demonstration of a database structure that can perform real-time system analysis and control of the Korean smart distribution management system (KSDMS). The developed database structure consists of a common information model (CIM)-based off-line database (DB), a physical DB (PDB) for DB establishment of the operating server, a real-time DB (RTDB) for real-time server operation and remote terminal unit data interconnection, and an application common model (ACM) DB for running application programs. The ACM DB for real-time system analysis and control of the application programs was developed by using a parallel table structure and a link list model, thereby providing fast input and output as well as high execution speed of application programs. Furthermore, the ACM DB was configured with hierarchical and non-hierarchical data models to reflect the system models that increase the DB size and operation speed through the reduction of the system, of which elements were unnecessary for analysis and control. The proposed database model was implemented and tested at the Gochaing and Jeju offices using a real system. Through data measurement of the remote terminal units, and through the operation and control of the application programs using the measurement, the performance, speed, and integrity of the proposed database model were validated, thereby demonstrating that this model can be applied to real systems. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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323 KiB

Open AccessArticle

DVP: A Novel High-Availability Seamless Redundancy (HSR) Protocol Traffic-Reduction Algorithm for a Substation Automation System Network

by Saad Nsaif and Jong-Myung Rhee

Energies 2014, 7(3), 1792-1810; https://doi.org/10.3390/en7031792 - 24 Mar 2014

Cited by 22 | Viewed by 7815

Abstract

The high-availability seamless redundancy (HSR) protocol, a potential candidate for substation automation system (SAS) networks, provides duplicated frame copies of each sent frame, with zero fault-recovery time. This means that even in the case of node or link failure, the destination node will [...] Read more.

The high-availability seamless redundancy (HSR) protocol, a potential candidate for substation automation system (SAS) networks, provides duplicated frame copies of each sent frame, with zero fault-recovery time. This means that even in the case of node or link failure, the destination node will receive at least one copy of the sent frame. Consequently, there is no network operation down time. However, the forwarding process of the QuadBox node in HSR is not smart and relies solely on duplication and random forwarding of all received frames. Thus, if a unicast frame is sent in any closed-loop network, the frame copies will be spread through most of all the links in both directions until they reach the destination node, which inevitably results in significant, unnecessary network traffic. In this paper, we present an algorithm called the dual virtual paths (DVP) algorithm to solve such an HSR excessive traffic issue. The idea behind our DVP algorithm is to establish automatic DVP between each HSR node and all the other nodes in the network, except for the QuadBox node. These virtual paths will be used for DVP unicast traffic transmission, rather than using the standard HSR transmission process. Therefore, the DVP algorithm results in less traffic, because there is no duplication or random forwarding, contrary to standard HSR. For the sample networks selected in this paper, the DVP algorithm shows more than a 70% reduction in network traffic and about an 80% reduction in the discarded traffic compared to the standard HSR protocol. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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756 KiB

Open AccessArticle

Comparison between Underground Cable and Overhead Line for a Low-Voltage Direct Current Distribution Network Serving Communication Repeater

by Jae-Han Kim, Ju-Yong Kim, Jin-Tae Cho, Il-Keun Song, Bo-Min Kweon, Il-Yop Chung and Joon-Ho Choi

Energies 2014, 7(3), 1656-1672; https://doi.org/10.3390/en7031656 - 20 Mar 2014

Cited by 12 | Viewed by 11852

Abstract

This paper compares the differences in economic feasibility and dynamic characteristics between underground (U/G) cable and overhead (O/H) line for low-voltage direct current (LVDC) distribution. Numerous low loaded long-distance distribution networks served by medium-voltage alternative current (MVAC) distribution lines exist in the Korean [...] Read more.

This paper compares the differences in economic feasibility and dynamic characteristics between underground (U/G) cable and overhead (O/H) line for low-voltage direct current (LVDC) distribution. Numerous low loaded long-distance distribution networks served by medium-voltage alternative current (MVAC) distribution lines exist in the Korean distribution network. This is an unavoidable choice to compensate voltage drop, therefore, excessive cost is expended for the amount of electrical power load. The Korean Electric Power Corporation (KEPCO) is consequently seeking a solution to replace the MVAC distribution line with a LVDC distribution line, reducing costs and providing better quality direct current (DC) electricity. A LVDC distribution network can be installed with U/G cables or O/H lines. In this paper, a realistic MVAC distribution network in a mountainous area was selected as the target model to replace with LVDC. A 30 year net present value (NPV) analysis of the economic feasibility was conducted to compare the cost of the two types of distribution line. A simulation study compared the results of the DC line fault with the power system computer aided design/electro-magnetic transient direct current (PSCAD/EMTDC). The economic feasibility evaluation and simulation study results will be used to select the applicable type of LVDC distribution network. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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491 KiB

Open AccessArticle

Coordinated Control of Distributed and Bulk Energy Storage for Alleviation of Post-Contingency Overloads

by Yunfeng Wen, Chuangxin Guo and Shufeng Dong

Energies 2014, 7(3), 1599-1620; https://doi.org/10.3390/en7031599 - 17 Mar 2014

Cited by 14 | Viewed by 7597

Abstract

This paper presents a novel corrective control strategy that can effectively coordinate distributed and bulk energy storage to relieve post-contingency overloads. Immediately following a contingency, distributed batteries are implemented to provide fast corrective actions to reduce power flows below their short-term emergency ratings. [...] Read more.

This paper presents a novel corrective control strategy that can effectively coordinate distributed and bulk energy storage to relieve post-contingency overloads. Immediately following a contingency, distributed batteries are implemented to provide fast corrective actions to reduce power flows below their short-term emergency ratings. During the long-term period, Pumped Hydro Storage units work in pumping or generation mode to aid conventional generating units keep line flows below the normal ratings. This problem is formulated as a multi-stage Corrective Security-constrained OPF (CSCOPF). An algorithm based on Benders decomposition was proposed to find the optimal base case solution and seek feasible corrective actions to handle all contingencies. Case studies based on a modified RTS-96 system demonstrate the performance and effectiveness of the proposed control strategy. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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2249 KiB

Open AccessArticle

Artificial Neural Network for Short-Term Load Forecasting in Distribution Systems

by Luis Hernández, Carlos Baladrón, Javier M. Aguiar, Lorena Calavia, Belén Carro, Antonio Sánchez-Esguevillas, Francisco Pérez, Ángel Fernández and Jaime Lloret

Energies 2014, 7(3), 1576-1598; https://doi.org/10.3390/en7031576 - 17 Mar 2014

Cited by 103 | Viewed by 10788

Abstract

The new paradigms and latest developments in the Electrical Grid are based on the introduction of distributed intelligence at several stages of its physical layer, giving birth to concepts such as Smart Grids, Virtual Power Plants, microgrids, Smart Buildings and [...] Read more.

The new paradigms and latest developments in the Electrical Grid are based on the introduction of distributed intelligence at several stages of its physical layer, giving birth to concepts such as Smart Grids, Virtual Power Plants, microgrids, Smart Buildings and Smart Environments. Distributed Generation (DG) is a philosophy in which energy is no longer produced exclusively in huge centralized plants, but also in smaller premises which take advantage of local conditions in order to minimize transmission losses and optimize production and consumption. This represents a new opportunity for renewable energy, because small elements such as solar panels and wind turbines are expected to be scattered along the grid, feeding local installations or selling energy to the grid depending on their local generation/consumption conditions. The introduction of these highly dynamic elements will lead to a substantial change in the curves of demanded energy. The aim of this paper is to apply Short-Term Load Forecasting (STLF) in microgrid environments with curves and similar behaviours, using two different data sets: the first one packing electricity consumption information during four years and six months in a microgrid along with calendar data, while the second one will be just four months of the previous parameters along with the solar radiation from the site. For the first set of data different STLF models will be discussed, studying the effect of each variable, in order to identify the best one. That model will be employed with the second set of data, in order to make a comparison with a new model that takes into account the solar radiation, since the photovoltaic installations of the microgrid will cause the power demand to fluctuate depending on the solar radiation. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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492 KiB

Open AccessArticle

Extended Distributed State Estimation: A Detection Method against Tolerable False Data Injection Attacks in Smart Grids

by Dai Wang, Xiaohong Guan, Ting Liu, Yun Gu, Chao Shen and Zhanbo Xu

Energies 2014, 7(3), 1517-1538; https://doi.org/10.3390/en7031517 - 12 Mar 2014

Cited by 77 | Viewed by 10415

Abstract

False data injection (FDI) is considered to be one of the most dangerous cyber-attacks in smart grids, as it may lead to energy theft from end users, false dispatch in the distribution process, and device breakdown during power generation. In this paper, a [...] Read more.

False data injection (FDI) is considered to be one of the most dangerous cyber-attacks in smart grids, as it may lead to energy theft from end users, false dispatch in the distribution process, and device breakdown during power generation. In this paper, a novel kind of FDI attack, named tolerable false data injection (TFDI), is constructed. Such attacks exploit the traditional detector’s tolerance of observation errors to bypass the traditional bad data detection. Then, a method based on extended distributed state estimation (EDSE) is proposed to detect TFDI in smart grids. The smart grid is decomposed into several subsystems, exploiting graph partition algorithms. Each subsystem is extended outward to include the adjacent buses and tie lines, and generate the extended subsystem. The Chi-squares test is applied to detect the false data in each extended subsystem. Through decomposition, the false data stands out distinctively from normal observation errors and the detection sensitivity is increased. Extensive TFDI attack cases are simulated in the Institute of Electrical and Electronics Engineers (IEEE) 14-, 39-, 118- and 300-bus systems. Simulation results show that the detection precision of the EDSE-based method is much higher than that of the traditional method, while the proposed method significantly reduces the associated computational costs. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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Open AccessArticle

The Development and Empirical Evaluation of the Korean Smart Distribution Management System

by Sang-Yun Yun, Chul-Min Chu, Seong-Chul Kwon, Il-Keun Song and Joon-Ho Choi

Energies 2014, 7(3), 1332-1362; https://doi.org/10.3390/en7031332 - 5 Mar 2014

Cited by 15 | Viewed by 8188

Abstract

This paper introduces the development and actual test results of the Korean Smart Distribution Management System (KSDMS). The KSDMS has been designed and developed to cope with the lack of interconnection capability of the Dispersed Energy Resource (DER), to provide standardization and compatibility, [...] Read more.

This paper introduces the development and actual test results of the Korean Smart Distribution Management System (KSDMS). The KSDMS has been designed and developed to cope with the lack of interconnection capability of the Dispersed Energy Resource (DER), to provide standardization and compatibility, and to implement automatic processing of service restoration, in the existing Distribution Automation System (DAS) in Korea. First, real-time system analysis and control application programs were developed, to solve the problems of the existing DAS; and the Distribution Management System (DMS) platform was developed, to run the developed application programs. Second, international standard-based communication, platform, and database structures were adopted, for standardization and compatibility. Third, a platform and application program functions were developed to process faults automatically; and a communication device and an intelligent electronic device (IED) were developed to automate fault restoration, through communication between devices. The KSDMS was evaluated by three tests: unit function test, platform and application program integration test, and empirical test. The first two were conducted on both small and large demonstration systems. The empirical test was performed at the Power Testing Center (PTC) in Gochang, and on a real system, at the Korea Electric Power Corporation (KEPCO), on Jeju Island. The test results verified that the KSDMS can actively resolve the problems of the existing DAS. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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Open AccessArticle

Development and Improvement of an Intelligent Cable Monitoring System for Underground Distribution Networks Using Distributed Temperature Sensing

by Jintae Cho, Jae-Han Kim, Hak-Ju Lee, Ju-Yong Kim, Il-Keun Song and Joon-Ho Choi

Energies 2014, 7(2), 1076-1094; https://doi.org/10.3390/en7021076 - 24 Feb 2014

Cited by 26 | Viewed by 9288

Abstract

With power systems switching to smart grids, real-time and on-line monitoring technologies for underground distribution power cables have become a priority. Most distribution components have been developed with self-diagnostic sensors to realize self-healing, one of the smart grid functions in a distribution network. [...] Read more.

With power systems switching to smart grids, real-time and on-line monitoring technologies for underground distribution power cables have become a priority. Most distribution components have been developed with self-diagnostic sensors to realize self-healing, one of the smart grid functions in a distribution network. Nonetheless, implementing a real-time and on-line monitoring system for underground distribution cables has been difficult because of high cost and low sensitivity. Nowadays, optical fiber composite power cables (OFCPCs) are being considered for communication and power delivery to cope with the increasing communication load in a distribution network. Therefore, the application of distributed temperature sensing (DTS) technology on OFCPCs used as underground distribution lines is studied for the real-time and on-line monitoring of the underground distribution power cables. Faults can be reduced and operating ampacity of the underground distribution system can be increased. This paper presents the development and improvement of an intelligent cable monitoring system for the underground distribution power system, using DTS technology and OFCPCs as the underground distribution lines in the field. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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647 KiB

Open AccessArticle

Voltage Support Provided by STATCOM in Unbalanced Power Systems

by Ana Rodríguez, Emilio J. Bueno, Álvar Mayor, Francisco J. Rodríguez and Aurelio García-Cerrada

Energies 2014, 7(2), 1003-1026; https://doi.org/10.3390/en7021003 - 24 Feb 2014

Cited by 18 | Viewed by 9157

Abstract

The presence of an unbalanced voltage at the point of common coupling (PCC) results in the appearance of a negative sequence current component that deteriorates the control performance. Static synchronous compensators (STATCOMs) are well-known to be a power application capable of carrying out [...] Read more.

The presence of an unbalanced voltage at the point of common coupling (PCC) results in the appearance of a negative sequence current component that deteriorates the control performance. Static synchronous compensators (STATCOMs) are well-known to be a power application capable of carrying out the regulation of the PCC voltage in distribution lines that can suffer from grid disturbances. This article proposes a novel PCC voltage controller in synchronous reference frame to compensate an unbalanced PCC voltage by means of a STATCOM, allowing an independent control of both positive and negative voltage sequences. Several works have been proposed in this line but they were not able to compensate an unbalance in the PCC voltage. Furthermore, this controller includes aspects as antiwindup and droop control to improve the control system performance. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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Open AccessArticle

Development and Field Test of Voltage VAR Optimization in the Korean Smart Distribution Management System

by Sang-Yun Yun, Pyeong-Ik Hwang, Seung-Il Moon, Seong-Chul Kwon, Il-Keun Song and Joon-Ho Choi

Energies 2014, 7(2), 643-669; https://doi.org/10.3390/en7020643 - 10 Feb 2014

Cited by 7 | Viewed by 7613

Abstract

This paper is a summary of the development and demonstration of an optimization program, voltage VAR optimization (VVO), in the Korean Smart Distribution Management System (KSDMS). KSDMS was developed to address the lack of receptivity of distributed generators (DGs), standardization and compatibility, and [...] Read more.

This paper is a summary of the development and demonstration of an optimization program, voltage VAR optimization (VVO), in the Korean Smart Distribution Management System (KSDMS). KSDMS was developed to address the lack of receptivity of distributed generators (DGs), standardization and compatibility, and manual failure recovery in the existing Korean automated distribution system. Focusing on the lack of receptivity of DGs, we developed a real-time system analysis and control program. The KSDMS VVO enhances manual system operation of the existing distribution system and provides a solution with all control equipment operated at a system level. The developed VVO is an optimal power flow (OPF) method that resolves violations, minimizes switching costs, and minimizes loss, and its function can vary depending on the operator’s command. The sequential mixed integer linear programming (SMILP) method was adopted to find the solution of the OPF. We tested the precision of the proposed VVO on selected simulated systems and its applicability to actual systems at two substations on the Jeju Island. Running the KSDMS VVO on a regular basis improved system stability, and it also raised no issues regarding its applicability to actual systems. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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576 KiB

Open AccessArticle

Distributed Load-Shedding System for Agent-Based Autonomous Microgrid Operations

by Yujin Lim, Hak-Man Kim and Tetsuo Kinoshita

Energies 2014, 7(1), 385-401; https://doi.org/10.3390/en7010385 - 20 Jan 2014

Cited by 37 | Viewed by 8205

Abstract

A microgrid is an eco-friendly power system because renewable sources are used as main power sources. In the islanded operation mode of a microgrid, maintaining the balance between power supply and power demand is a very important problem. In the case of surplus [...] Read more.

A microgrid is an eco-friendly power system because renewable sources are used as main power sources. In the islanded operation mode of a microgrid, maintaining the balance between power supply and power demand is a very important problem. In the case of surplus supply, decreased generation output and/or charge of distributed storages can be applied to solve the imbalance between power supply and demand. In the case of supply shortages, increased generation output and/or discharge of distributed storages can be applied. Especially in the case of critical supply shortages, load shedding should be applied. In a distributed load-shedding approach, microgrid components need to make decisions autonomously. For autonomous microgrid operation, a multi-agent system has been investigated. In this paper, a distributed load-shedding system for agent-based autonomous operation of a microgrid is designed. The designed system is implemented and tested to show the functionality and feasibility of the proposed system. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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430 KiB

Open AccessArticle

Analysis of the Dynamic Performance of Self-Excited Induction Generators Employed in Renewable Energy Generation

by Mohamed E. A. Farrag and Ghanim A. Putrus

Energies 2014, 7(1), 278-294; https://doi.org/10.3390/en7010278 - 10 Jan 2014

Cited by 12 | Viewed by 6946

Abstract

Incentives, such as the Feed-in-tariff are expected to lead to continuous increase in the deployment of Small Scale Embedded Generation (SSEG) in the distribution network. Self-Excited Induction Generators (SEIG) represent a significant segment of potential SSEG. The quality of SEIG output voltage magnitude [...] Read more.

Incentives, such as the Feed-in-tariff are expected to lead to continuous increase in the deployment of Small Scale Embedded Generation (SSEG) in the distribution network. Self-Excited Induction Generators (SEIG) represent a significant segment of potential SSEG. The quality of SEIG output voltage magnitude and frequency is investigated in this paper to support the SEIG operation for different network operating conditions. The dynamic behaviour of the SEIG resulting from disconnection, reconnection from/to the grid and potential operation in islanding mode is studied in detail. The local load and reactive power supply are the key factors that determine the SEIG performance, as they have significant influence on the voltage and frequency change after disconnection from the grid. Hence, the aim of this work is to identify the optimum combination of the reactive power supply (essential for self excitation of the SEIG) and the active load (essential for balancing power generation and demand). This is required in order to support the SEIG operation after disconnection from the grid, during islanding and reconnection to the grid. The results show that the generator voltage and speed (frequency) can be controlled and maintained within the statuary limits. This will enable safe disconnection and reconnection of the SEIG from/to the grid and makes it easier to operate in islanding mode. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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509 KiB

Open AccessArticle

Implementation and Control of a Residential Electrothermal Microgrid Based on Renewable Energies, a Hybrid Storage System and Demand Side Management

by Julio Pascual, Pablo Sanchis and Luis Marroyo

Energies 2014, 7(1), 210-237; https://doi.org/10.3390/en7010210 - 8 Jan 2014

Cited by 55 | Viewed by 9626

Abstract

This paper proposes an energy management strategy for a residential electrothermal microgrid, based on renewable energy sources. While grid connected, it makes use of a hybrid electrothermal storage system, formed by a battery and a hot water tank along with an electrical water [...] Read more.

This paper proposes an energy management strategy for a residential electrothermal microgrid, based on renewable energy sources. While grid connected, it makes use of a hybrid electrothermal storage system, formed by a battery and a hot water tank along with an electrical water heater as a controllable load, which make possible the energy management within the microgrid. The microgrid emulates the operation of a single family home with domestic hot water (DHW) consumption, a heating, ventilation and air conditioning (HVAC) system as well as the typical electric loads. An energy management strategy has been designed which optimizes the power exchanged with the grid profile in terms of peaks and fluctuations, in applications with high penetration levels of renewables. The proposed energy management strategy has been evaluated and validated experimentally in a full scale residential microgrid built in our Renewable Energy Laboratory, by means of continuous operation under real conditions. The results show that the combination of electric and thermal storage systems with controllable loads is a promising technology that could maximize the penetration level of renewable energies in the electric system. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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331 KiB

Open AccessArticle

Optimal Sizing of Battery Storage Systems for Industrial Applications when Uncertainties Exist

by Guido Carpinelli, Anna Rita Di Fazio, Shahab Khormali and Fabio Mottola

Energies 2014, 7(1), 130-149; https://doi.org/10.3390/en7010130 - 3 Jan 2014

Cited by 33 | Viewed by 7671

Abstract

Demand response (DR) can be very useful for an industrial facility, since it allows noticeable reductions in the electricity bill due to the significant value of energy demand. Although most industrial processes have stringent constraints in terms of hourly active power, DR only [...] Read more.

Demand response (DR) can be very useful for an industrial facility, since it allows noticeable reductions in the electricity bill due to the significant value of energy demand. Although most industrial processes have stringent constraints in terms of hourly active power, DR only becomes attractive when performed with the contemporaneous use of battery energy storage systems (BESSs). When this option is used, an optimal sizing of BESSs is desirable, because the investment costs can be significant. This paper deals with the optimal sizing of a BESS installed in an industrial facility to reduce electricity costs. A four-step procedure, based on Decision Theory, was used to obtain a good solution for the sizing problem, even when facing uncertainties; in fact, we think that the sizing procedure must properly take into account the unavoidable uncertainties introduced by the cost of electricity and the load demands of industrial facilities. Three approaches provided by Decision Theory were applied, and they were based on: (1) the minimization of expected cost; (2) the regret felt by the sizing engineer; and (3) a mix of (1) and (2). The numerical applications performed on an actual industrial facility provided evidence of the effectiveness of the proposed procedure. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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957 KiB

Open AccessArticle

A Load Fluctuation Characteristic Index and Its Application to Pilot Node Selection

by Huaichang Ge, Qinglai Guo, Hongbin Sun, Bin Wang, Boming Zhang and Wenchuan Wu

Energies 2014, 7(1), 115-129; https://doi.org/10.3390/en7010115 - 3 Jan 2014

Cited by 10 | Viewed by 7267

Abstract

The operation of power systems has been complicated by the rapid diversification of loads. Analyzing load characteristics becomes necessary to different utilities in energy management systems to ensure the reliability of power systems. Here, we describe a method of analyzing and quantifying the [...] Read more.

The operation of power systems has been complicated by the rapid diversification of loads. Analyzing load characteristics becomes necessary to different utilities in energy management systems to ensure the reliability of power systems. Here, we describe a method of analyzing and quantifying the load characteristics and introduce its application to pilot nodes selection for zone based voltage control. We propose a new index, the Q-fluctuation (QF), to quantify the load characteristic of reactive power based on an analysis of historical data. A second index, the V-fluctuation (VF), which is a combination of the QF and the Q–V sensitivity that reflects structural information for the grid describes the voltage deviation at each node. These indices are used to construct the voltage fluctuation space, which is then used to select the pilot node for each zone. Simulation studies using IEEE 14-bus and 118-bus systems are described, and used to demonstrate the advantages of the proposed method. The method was able to improve the secondary voltage control and enhance the grid reliability in response to structural changes. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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5209 KiB

Open AccessArticle

Impact of Scheduling Flexibility on Demand Profile Flatness and User Inconvenience in Residential Smart Grid System

by Naveed Ul Hassan, Muhammad Adeel Pasha, Chau Yuen, Shisheng Huang and Xiumin Wang

Energies 2013, 6(12), 6608-6635; https://doi.org/10.3390/en6126608 - 18 Dec 2013

Cited by 47 | Viewed by 7481

Abstract

The objective of this paper is to study the impact of scheduling flexibility on both demand profile flatness and user inconvenience in residential smart grid systems. Temporal variations in energy consumption by end users result in peaks and troughs in the aggregated demand [...] Read more.

The objective of this paper is to study the impact of scheduling flexibility on both demand profile flatness and user inconvenience in residential smart grid systems. Temporal variations in energy consumption by end users result in peaks and troughs in the aggregated demand profile. In a residential smart grid, some of these peaks and troughs can be eliminated through appropriate load balancing algorithms. However, load balancing requires user participation by allowing the grid to re-schedule some of their loads. In general, more scheduling flexibility can result in more demand profile flatness, however the resulting inconvenience to users would also increase. In this paper, our objective is to help the grid determine an appropriate amount of scheduling flexibility that it should demand from users, based on which, proper incentives can be designed. We consider three different types of scheduling flexibility (delay, advance scheduling and flexible re-scheduling) in flexible loads and develop both optimal and sub-optimal scheduling algorithms. We discuss their implementation in centralized and distributed manners. We also identify the existence of a saturation point. Beyond this saturation point, any increase in scheduling flexibility does not significantly affect the flatness of the demand profile while user inconvenience continues to increase. Moreover, full participation of all the households is not required since increasing user participation only marginally increases demand profile flatness. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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1167 KiB

Open AccessArticle

Optimal Scheduling for the Complementary Energy Storage System Operation Based on Smart Metering Data in the DC Distribution System

by Bokyung Ko, Nugroho Prananto Utomo, Gilsoo Jang, Jaehan Kim and Jintae Cho

Energies 2013, 6(12), 6569-6585; https://doi.org/10.3390/en6126569 - 18 Dec 2013

Cited by 7 | Viewed by 6095

Abstract

The increasing penetration of distributed generation (DG) sources in low-voltage grid feeders causes problems concerning voltage regulation. The penetration of DG sources such as photovoltaics (PVs) in the distribution system can significantly impact the power flow and voltage conditions on the customer side. [...] Read more.

The increasing penetration of distributed generation (DG) sources in low-voltage grid feeders causes problems concerning voltage regulation. The penetration of DG sources such as photovoltaics (PVs) in the distribution system can significantly impact the power flow and voltage conditions on the customer side. As the DG sources are more commonly connected to low-voltage distribution systems, voltage fluctuations in the distribution system are experienced because of the DG fluctuation and uncertainty. Therefore, the penetration of DGs in distribution systems is often limited by the required operating voltage ranges. By using an energy storage system (ESS), voltage fluctuation can be compensated for, thus satisfying the voltage regulation requirements. This paper presents an ESS scheduling algorithm based on the power injection data obtained from a smart metering system. The proposed ESS scheduling algorithm is designed for use within a direct current (DC) distribution grid, which comprises customers, each with a PV and an ESS system. The purpose of this ESS scheduling algorithm is to optimize the ESS scheduling by considering the complementary operation among all the ESSs. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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545 KiB

Open AccessArticle

Operation Optimization Based on the Power Supply and Storage Capacity of an Active Distribution Network

by Wenpeng Yu, Dong Liu and Yuhui Huang

Energies 2013, 6(12), 6423-6438; https://doi.org/10.3390/en6126423 - 11 Dec 2013

Cited by 29 | Viewed by 6732

Abstract

Due to the interconnection and active management of Distributed Generation (DG) and Energy Storage Systems (ESSs), the traditional electrical distribution network has become an Active Distribution Network (ADN), posing challenges to the operation optimization of the network. The power supply and storage capacity [...] Read more.

Due to the interconnection and active management of Distributed Generation (DG) and Energy Storage Systems (ESSs), the traditional electrical distribution network has become an Active Distribution Network (ADN), posing challenges to the operation optimization of the network. The power supply and storage capacity indexes of a Local Autonomy Control Region (LACR), which consists of DGs, ESSs and the network, are proposed in this paper to quantify the power regulating range of a LACR. DG/ESS and the network are considered as a whole in the model of the indexes, considering both network constraints and power constraints of the DG/ESS. The index quantifies the maximum LACR power supplied to or received from ADN lines. Similarly, power supply and storage capacity indexes of the ADN line are also proposed to quantify the maximum power exchanged between ADN lines. Then a practical algorithm to calculate the indexes is presented, and an operation optimization model is proposed based on the indexes to maximum the economic benefit of DG/ESS. In the optimization model, the power supply reliability of the ADN line is also considered. Finally, the indexes of power supply and storage capacity and the optimization are demonstrated in a case study. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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353 KiB

Open AccessArticle

Evaluation of the Effects of Nationwide Conservation Voltage Reduction on Peak-Load Shaving Using SOMAS Data

by Soon-Ryul Nam, Sang-Hee Kang, Joo-Ho Lee, Seon-Ju Ahn and Joon-Ho Choi

Energies 2013, 6(12), 6322-6334; https://doi.org/10.3390/en6126322 - 3 Dec 2013

Cited by 10 | Viewed by 5887

Abstract

In this paper we propose a new method to evaluate the effects of nationwide conservation voltage reduction (CVR) on peak-load shaving, using substation operating results management system (SOMAS) data. Its evaluation is based on a national CVR factor, which is defined as the [...] Read more.

In this paper we propose a new method to evaluate the effects of nationwide conservation voltage reduction (CVR) on peak-load shaving, using substation operating results management system (SOMAS) data. Its evaluation is based on a national CVR factor, which is defined as the weighted average of CVR factors associated with all transformer banks and weighting coefficients are determined by the reconstructed loads corresponding to each transformer bank. To make use of the data resulting from nationwide CVR without installing additional measuring devices, we adopt a linearized static-load model with a linearizing parameter. SOMAS data are used to evaluate the effects of nationwide CVR on peak-load shaving in the Korean power system. Evaluation results show that the national CVR factor of the Korean power system has small values in the summer season and large values in the winter season. This means that the effect of nationwide CVR on peak-load shaving in the Korean power system presents stronger benefits during winter months. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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Open AccessArticle

AC Power Local Network with Multiple Power Routers

by Ryo Takahashi, Yutaro Kitamori and Takashi Hikihara

Energies 2013, 6(12), 6293-6303; https://doi.org/10.3390/en6126293 - 2 Dec 2013

Cited by 17 | Viewed by 7244

Abstract

Controlling power flow and achieving appropriate matching between power sources and loads according to the quality of energy is expected to be one of the approaches to reduce wasted energy consumption. A power router, proposed recently, has the capability of realizing circuit switching [...] Read more.

Controlling power flow and achieving appropriate matching between power sources and loads according to the quality of energy is expected to be one of the approaches to reduce wasted energy consumption. A power router, proposed recently, has the capability of realizing circuit switching in a power distribution network. This study focuses on the feasibility of an AC power routing network system composed of multiple power routers. To evaluate the feasibility, we experimentally confirm the circuit switching operation of the parallel and series configurations of the power routers, so that the network system can be designed by the combination of parallel and series configurations. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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6159 KiB

Open AccessArticle

Design and Implementation of Real-Time Intelligent Control and Structure Based on Multi-Agent Systems in Microgrids

by Ming-Tse Kuo and Shiue-Der Lu

Energies 2013, 6(11), 6045-6059; https://doi.org/10.3390/en6116045 - 19 Nov 2013

Cited by 31 | Viewed by 9711

Abstract

By consulting various worldwide definitions of microgrids and distributed energy, this study presents a microgrid-structured multi-agent system and uses Matlab/Simulink to construct a circuit with microgrid features, which enables the changes in each electrical source and load in the microgrid to be monitored [...] Read more.

By consulting various worldwide definitions of microgrids and distributed energy, this study presents a microgrid-structured multi-agent system and uses Matlab/Simulink to construct a circuit with microgrid features, which enables the changes in each electrical source and load in the microgrid to be monitored and controlled. This multi-agent system adheres to the Java Agent Development Framework (JADE) platform specifications of the Foundation for Intelligent Physical Agents (FIPA), facilitating communication, information transfers, and the receipt of real-time information regarding the microgrid and each component in the microgrid. Furthermore, the real-time state in the microgrid can be correspondingly controlled, achieving the most efficient real-time monitoring and control for electrical sources and load management in the microgrid. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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550 KiB

Open AccessArticle

Price Forecasting in the Day-Ahead Energy Market by an Iterative Method with Separate Normal Price and Price Spike Frameworks

by Sergey Voronin and Jarmo Partanen

Energies 2013, 6(11), 5897-5920; https://doi.org/10.3390/en6115897 - 12 Nov 2013

Cited by 49 | Viewed by 8615

Abstract

A forecasting methodology for prediction of both normal prices and price spikes in the day-ahead energy market is proposed. The method is based on an iterative strategy implemented as a combination of two modules separately applied for normal price and price spike predictions. [...] Read more.

A forecasting methodology for prediction of both normal prices and price spikes in the day-ahead energy market is proposed. The method is based on an iterative strategy implemented as a combination of two modules separately applied for normal price and price spike predictions. The normal price module is a mixture of wavelet transform, linear AutoRegressive Integrated Moving Average (ARIMA) and nonlinear neural network models. The probability of a price spike occurrence is produced by a compound classifier in which three single classification techniques are used jointly to make a decision. Combined with the spike value prediction technique, the output from the price spike module aims to provide a comprehensive price spike forecast. The overall electricity price forecast is formed as combined normal price and price spike forecasts. The forecast accuracy of the proposed method is evaluated with real data from the Finnish Nord Pool Spot day-ahead energy market. The proposed method provides significant improvement in both normal price and price spike prediction accuracy compared with some of the most popular forecast techniques applied for case studies of energy markets. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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Open AccessArticle

Output Current Ripple Reduction Algorithms for Home Energy Storage Systems

by Jin-Hyuk Park, Hae-Gwang Jeong and Kyo-Beum Lee

Energies 2013, 6(10), 5552-5569; https://doi.org/10.3390/en6105552 - 22 Oct 2013

Cited by 18 | Viewed by 7786

Abstract

This paper proposes an output current ripple reduction algorithm using a proportional-integral (PI) controller for an energy storage system (ESS). In single-phase systems, the DC/AC inverter has a second-order harmonic at twice the grid frequency of a DC-link voltage caused by pulsation of [...] Read more.

This paper proposes an output current ripple reduction algorithm using a proportional-integral (PI) controller for an energy storage system (ESS). In single-phase systems, the DC/AC inverter has a second-order harmonic at twice the grid frequency of a DC-link voltage caused by pulsation of the DC-link voltage. The output current of a DC/DC converter has a ripple component because of the ripple of the DC-link voltage. The second-order harmonic adversely affects the battery lifetime. The proposed algorithm has an advantage of reducing the second-order harmonic of the output current in the variable frequency system. The proposed algorithm is verified from the PSIM simulation and experiment with the 3 kW ESS model. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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677 KiB

Open AccessArticle

Design and Implementation of a High Quality Power Supply Scheme for Distributed Generation in a Micro-Grid

by Mingchao Xia and Xiaoliang Li

Energies 2013, 6(9), 4924-4944; https://doi.org/10.3390/en6094924 - 23 Sep 2013

Cited by 18 | Viewed by 6938

Abstract

A low carbon, high efficiency and high quality power supply scheme for Distributed Generation (DG) in a micro-grid is presented. A three-phase, four-leg DG grid-interfacing converter based on the improved structure of a Unified Power Quality Conditioner (UPQC, including a series converter and [...] Read more.

A low carbon, high efficiency and high quality power supply scheme for Distributed Generation (DG) in a micro-grid is presented. A three-phase, four-leg DG grid-interfacing converter based on the improved structure of a Unified Power Quality Conditioner (UPQC, including a series converter and a parallel converter) is adopted, and improved indirect and direct control strategies are proposed. It can be observed that these strategies effectively compensate for voltage sags, voltage swells and voltage distortion, as well as voltage power quality problems resulting from the nonlinear and unbalanced loads in a micro-grid. While solving the coupling interference from series–parallel, the grid-interfacing converter can achieve proper load power sharing in a micro-grid. In particular, an improved minimum-energy compensation method is proposed that can overcome the conventional compensation algorithm defects, ensure the load voltage’s phase angle stability, improve the voltage compensating ability and range, reduce the capacity and cost of converters, and reduce the shock of micro-grid switching between grid-connected mode and islanded mode. Moreover, the advantages/disadvantages and application situation of the two improved control strategies are analyzed. Finally, the performance of the proposed control strategies has been verified through a MATLAB/Simulink simulation under various operating conditions. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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459 KiB

Open AccessArticle

Adaptive Wide-Area Damping Control Scheme for Smart Grids with Consideration of Signal Time Delay

by Guowei Cai, Deyou Yang and Cheng Liu

Energies 2013, 6(9), 4841-4858; https://doi.org/10.3390/en6094841 - 13 Sep 2013

Cited by 15 | Viewed by 7429

Abstract

As an important part of the smart grid, a wide-area measurement system (WAMS) provides the key technical support for power system monitoring, protection and control. But 20 uncertainties in system parameters and signal transmission time delay could worsen the damping effect and deteriorate [...] Read more.

As an important part of the smart grid, a wide-area measurement system (WAMS) provides the key technical support for power system monitoring, protection and control. But 20 uncertainties in system parameters and signal transmission time delay could worsen the damping effect and deteriorate the system stability. In the presented study, the subspace system identification technique (SIT) is used to firstly derive a low-order linear model of a power system from the measurements. Then, a novel adaptive wide-area damping control scheme for online tuning of the wide-area damping controller (WADC) parameters using the residue method is proposed. In order to eliminate the effects of the time delay to the signal transmission, a simple and practical time delay compensation algorithm is proposed to compensate the time delay in each wide-area control signal. Detailed examples, inspired by the IEEE test system under various disturbance scenarios, have been used to verify the effectiveness of the proposed adaptive wide-area damping control scheme. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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723 KiB

Open AccessArticle

General and Simple Decision Method for DG Penetration Level in View of Voltage Regulation at Distribution Substation Transformers

by Il-Keun Song, Won-Wook Jung, Chul-Min Chu, Seong-Soo Cho, Hyun-Koo Kang and Joon-Ho Choi

Energies 2013, 6(9), 4786-4798; https://doi.org/10.3390/en6094786 - 10 Sep 2013

Cited by 11 | Viewed by 7993

Abstract

A distribution system was designed and operated by considering unidirectional power flow from a utility source to end-use loads. The large penetrations of distributed generation (DG) into the existing distribution system causes a variety of technical problems, such as frequent tap changing problems [...] Read more.

A distribution system was designed and operated by considering unidirectional power flow from a utility source to end-use loads. The large penetrations of distributed generation (DG) into the existing distribution system causes a variety of technical problems, such as frequent tap changing problems of the on-load tap changer (OLTC) transformer, local voltage rise, protection coordination, exceeding short-circuit capacity, and harmonic distortion. In view of voltage regulation, the intermittent fluctuation of the DG output power results in frequent tap changing operations of the OLTC transformer. Thus, many utilities limit the penetration level of DG and are eager to find the reasonable penetration limits of DG in the distribution system. To overcome this technical problem, utilities have developed a new voltage regulation method in the distribution system with a large DG penetration level. In this paper, the impact of DG on the OLTC operations controlled by the line drop compensation (LDC) method is analyzed. In addition, a generalized determination methodology for the DG penetration limits in a distribution substation transformer is proposed. The proposed DG penetration limits could be adopted for a simplified interconnection process in DG interconnection guidelines. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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631 KiB

Open AccessArticle

Recursive Pyramid Algorithm-Based Discrete Wavelet Transform for Reactive Power Measurement in Smart Meters

by Najam Ul Hasan, Waleed Ejaz, Mahin K. Atiq and Hyung Seok Kim

Energies 2013, 6(9), 4721-4738; https://doi.org/10.3390/en6094721 - 9 Sep 2013

Cited by 3 | Viewed by 8043

Abstract

Measurement of the active, reactive, and apparent power is one of the most fundamental tasks of smart meters in energy systems. Recently, a number of studies have employed the discrete wavelet transform (DWT) for power measurement in smart meters. The most common way [...] Read more.

Measurement of the active, reactive, and apparent power is one of the most fundamental tasks of smart meters in energy systems. Recently, a number of studies have employed the discrete wavelet transform (DWT) for power measurement in smart meters. The most common way to implement DWT is the pyramid algorithm; however, this is not feasible for practical DWT computation because it requires either a log N cascaded filter or O (N) word size memory storage for an input signal of the N-point. Both solutions are too expensive for practical applications of smart meters. It is proposed that the recursive pyramid algorithm is more suitable for smart meter implementation because it requires only word size storage of L × Log (N-L), where L is the length of filter. We also investigated the effect of varying different system parameters, such as the sampling rate, dc offset, phase offset, linearity error in current and voltage sensors, analog to digital converter resolution, and number of harmonics in a non-sinusoidal system, on the reactive energy measurement using DWT. The error analysis is depicted in the form of the absolute difference between the measured and the true value of the reactive energy. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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1159 KiB

Open AccessArticle

Improved Short-Term Load Forecasting Based on Two-Stage Predictions with Artificial Neural Networks in a Microgrid Environment

by Luis Hernández, Carlos Baladrón, Javier M. Aguiar, Lorena Calavia, Belén Carro, Antonio Sánchez-Esguevillas, Javier Sanjuán, Álvaro González and Jaime Lloret

Energies 2013, 6(9), 4489-4507; https://doi.org/10.3390/en6094489 - 29 Aug 2013

Cited by 40 | Viewed by 7907

Abstract

Short-Term Load Forecasting plays a significant role in energy generation planning, and is specially gaining momentum in the emerging Smart Grids environment, which usually presents highly disaggregated scenarios where detailed real-time information is available thanks to Communications and Information Technologies, as it happens [...] Read more.

Short-Term Load Forecasting plays a significant role in energy generation planning, and is specially gaining momentum in the emerging Smart Grids environment, which usually presents highly disaggregated scenarios where detailed real-time information is available thanks to Communications and Information Technologies, as it happens for example in the case of microgrids. This paper presents a two stage prediction model based on an Artificial Neural Network in order to allow Short-Term Load Forecasting of the following day in microgrid environment, which first estimates peak and valley values of the demand curve of the day to be forecasted. Those, together with other variables, will make the second stage, forecast of the entire demand curve, more precise than a direct, single-stage forecast. The whole architecture of the model will be presented and the results compared with recent work on the same set of data, and on the same location, obtaining a Mean Absolute Percentage Error of 1.62% against the original 2.47% of the single stage model. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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1245 KiB

Open AccessArticle

Analysis and Simulation of Fault Characteristics of Power Switch Failures in Distribution Electronic Power Transformers

by Zixia Sang, Chengxiong Mao, Jiming Lu and Dan Wang

Energies 2013, 6(8), 4246-4268; https://doi.org/10.3390/en6084246 - 19 Aug 2013

Cited by 32 | Viewed by 7826

Abstract

This paper presents research on the voltage and current distortion in the input stage, isolation stage and output stage of Distribution Electronic Power transformer (D-EPT) after the open-circuit and short-circuit faults of its power switches. In this paper, the operational principles and the [...] Read more.

This paper presents research on the voltage and current distortion in the input stage, isolation stage and output stage of Distribution Electronic Power transformer (D-EPT) after the open-circuit and short-circuit faults of its power switches. In this paper, the operational principles and the control methods for input stage, isolation stage and output stage of D-EPT, which work as a cascaded H-bridge rectifier, DC-DC converter and inverter, respectively, are introduced. Based on conclusions derived from the performance analysis of D-EPT after the faults, this paper comes up with the effects from its topology design and control scheme on the current and voltage distortion. According to the EPT fault characteristics, since the waveforms of relevant components heavily depend on the location of the faulty switch, it is very easy to locate the exact position of the faulty switch. Finally, the fault characteristics peculiar to D-EPT are analyzed, and further discussed with simulation on the Saber platform, as well as a fault location diagnosis algorithm. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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Review

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1524 KiB

Open AccessReview

Reviewing Microgrids from a Multi-Agent Systems Perspective

by Jorge J. Gomez-Sanz, Sandra Garcia-Rodriguez, Nuria Cuartero-Soler and Luis Hernandez-Callejo

Energies 2014, 7(5), 3355-3382; https://doi.org/10.3390/en7053355 - 22 May 2014

Cited by 51 | Viewed by 8335

Abstract

The construction of Smart Grids leads to the main question of what kind of intelligence such grids require and how to build it. Some authors choose an agent based solution to realize this intelligence. However, there may be some misunderstandings in the way [...] Read more.

The construction of Smart Grids leads to the main question of what kind of intelligence such grids require and how to build it. Some authors choose an agent based solution to realize this intelligence. However, there may be some misunderstandings in the way this technology is being applied. This paper exposes some considerations of this subject, focusing on the Microgrid level, and shows a practical example through INGENIAS methodology, which is a methodology for the development of Agent Oriented systems that applies Model Driven Development techniques to produce fully functional Multi-Agent Systems. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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775 KiB

Open AccessReview

Strategies for Power Line Communications Smart Metering Network Deployment

by Alberto Sendin, Ivan Peña and Pablo Angueira

Energies 2014, 7(4), 2377-2420; https://doi.org/10.3390/en7042377 - 15 Apr 2014

Cited by 64 | Viewed by 15644

Abstract

Smart Grids are becoming a reality all over the world. Nowadays, the research efforts for the introduction and deployment of these grids are mainly focused on the development of the field of Smart Metering. This emerging application requires the use of technologies to [...] Read more.

Smart Grids are becoming a reality all over the world. Nowadays, the research efforts for the introduction and deployment of these grids are mainly focused on the development of the field of Smart Metering. This emerging application requires the use of technologies to access the significant number of points of supply (PoS) existing in the grid, covering the Low Voltage (LV) segment with the lowest possible costs. Power Line Communications (PLC) have been extensively used in electricity grids for a variety of purposes and, of late, have been the focus of renewed interest. PLC are really well suited for quick and inexpensive pervasive deployments. However, no LV grid is the same in any electricity company (utility), and the particularities of each grid evolution, architecture, circumstances and materials, makes it a challenge to deploy Smart Metering networks with PLC technologies, with the Smart Grid as an ultimate goal. This paper covers the evolution of Smart Metering networks, together with the evolution of PLC technologies until both worlds have converged to project PLC-enabled Smart Metering networks towards Smart Grid. This paper develops guidelines over a set of strategic aspects of PLC Smart Metering network deployment based on the knowledge gathered on real field; and introduces the future challenges of these networks in their evolution towards the Smart Grid. Full article

(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)

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