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586 KiB

Open AccessArticle

Three-Phase Primary Control for Unbalance Sharing between Distributed Generation Units in a Microgrid

by Tine L. Vandoorn, Jeroen D. M. De Kooning, Jan Van de Vyver and Lieven Vandevelde

Energies 2013, 6(12), 6586-6607; https://doi.org/10.3390/en6126586 - 18 Dec 2013

Cited by 4 | Viewed by 5328

Abstract

For islanded microgrids, droop-based control concepts have been developed both in single and three-phase variants. The three-phase controllers often assume a balanced network; hence, unbalance sharing and/or mitigation remains a challenging issue. Therefore, in this paper, unbalance is considered in a three-phase islanded [...] Read more.

For islanded microgrids, droop-based control concepts have been developed both in single and three-phase variants. The three-phase controllers often assume a balanced network; hence, unbalance sharing and/or mitigation remains a challenging issue. Therefore, in this paper, unbalance is considered in a three-phase islanded microgrid in which the distributed generation (DG) units are operated by the voltage-based droop (VBD) control. For this purpose, the VBD control, which has been developed for single-phase systems, is extended for a three-phase application and an additional control loop is added for unbalance mitigation and sharing. The method is based on an unbalance mitigation scheme by DG units in grid-connected systems, which is altered for usage in grid-forming DG units with droop control. The reaction of the DG units to unbalance is determined by the main parameter of the additional control loop, viz., the distortion damping resistance, R_d. The effect of R_d on the unbalance mitigation is studied in this paper, i.e., dependent on _Rd, the DG units can be resistive for unbalance (RU) or they can contribute in the weakest phase (CW). The paper shows that the RU method decreases the line losses in the system and achieves better power equalization between the DG unit’s phases. However, it leads to a larger voltage unbalance near the loads. The CW method leads to a more uneven power between the DG unit’s phases and larger line losses, but a better voltage quality near the load. However, it can negatively affect the stability of the system. In microgrids with multiple DG units, the distortion damping resistance is set such that the unbalanced load can be shared between multiple DG units in an actively controlled manner rather than being determined by the microgrid configuration solely. The unit with the lowest distortion damping resistance provides relatively more of the unbalanced currents. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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645 KiB

Open AccessArticle

Decentralized and Real-Time Power Dispatch Control for an Islanded Microgrid Supported by Distributed Power Sources

by Changsun Ahn and Huei Peng

Energies 2013, 6(12), 6439-6454; https://doi.org/10.3390/en6126439 - 13 Dec 2013

Cited by 27 | Viewed by 6059

Abstract

Microgrids can deploy traditional and/or renewable power sources to support remote sites. Utilizing renewable power sources requires more complicated control strategies to achieve acceptable power quality and maintain grid stability. In this research, we assume that the grid stability problem is already solved. [...] Read more.

Microgrids can deploy traditional and/or renewable power sources to support remote sites. Utilizing renewable power sources requires more complicated control strategies to achieve acceptable power quality and maintain grid stability. In this research, we assume that the grid stability problem is already solved. As a next step, we focus on how the power can be dispatched from multiple power sources for improved grid efficiency. Isolated microgrids frequently require reconfigurations because of the grid expansion or component failures. Therefore, the control strategies ideally should be implemented in a plug-and-play fashion. Moreover, these strategies ideally require no pre-knowledge of the grid structure, and as little communication with neighboring power sources as possible. The control objective is to minimize a cost function that can be adjusted to reflect the desire to minimize energy cost and/or losses. An algorithm is designed to satisfy a derived necessary condition of function optimality. Such conditions are obtained by formulating Lagrange functions. An equivalent grid model approximates the grid structure which was later confirmed to represent the grid behavior adequately. For decentralized operations, we execute the distributed control sequentially using a simple token communication protocol. The performance of the combined system identification-Lagrange function minimization algorithm is demonstrated through simulations. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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961 KiB

Open AccessArticle

Hour-Ahead Wind Speed and Power Forecasting Using Empirical Mode Decomposition

by Ying-Yi Hong, Ti-Hsuan Yu and Ching-Yun Liu

Energies 2013, 6(12), 6137-6152; https://doi.org/10.3390/en6126137 - 25 Nov 2013

Cited by 48 | Viewed by 6703

Abstract

Operation of wind power generation in a large farm is quite challenging in a smart grid owing to uncertain weather conditions. Consequently, operators must accurately forecast wind speed/power in the dispatch center to carry out unit commitment, real power scheduling and economic dispatch. [...] Read more.

Operation of wind power generation in a large farm is quite challenging in a smart grid owing to uncertain weather conditions. Consequently, operators must accurately forecast wind speed/power in the dispatch center to carry out unit commitment, real power scheduling and economic dispatch. This work presents a novel method based on the integration of empirical mode decomposition (EMD) with artificial neural networks (ANN) to forecast the short-term (1 h ahead) wind speed/power. First, significant parameters for training the ANN are identified using the correlation coefficients. These significant parameters serve as inputs of the ANN. Owing to the volatile and intermittent wind speed/power, the historical time series of wind speed/power is decomposed into several intrinsic mode functions (IMFs) and a residual function through EMD. Each IMF becomes less volatile and therefore increases the accuracy of the neural network. The final forecasting results are achieved by aggregating all individual forecasting results from all IMFs and their corresponding residual functions. Real data related to the wind speed and wind power measured at a wind-turbine generator in Taiwan are used for simulation. The wind speed forecasting and wind power forecasting for the four seasons are studied. Comparative studies between the proposed method and traditional methods (i.e., artificial neural network without EMD, autoregressive integrated moving average (ARIMA), and persistence method) are also introduced. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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1724 KiB

Open AccessArticle

Energy Management and Smart Grids

by Rosario Miceli

Energies 2013, 6(4), 2262-2290; https://doi.org/10.3390/en6042262 - 22 Apr 2013

Cited by 103 | Viewed by 13436

Abstract

The paper outlines energy management concepts and the smart grid evolution. The necessity of considering energy management as a crucial innovation in load supplying to permit a more powerful penetration of renewable energy usage at the building and city level and to perform [...] Read more.

The paper outlines energy management concepts and the smart grid evolution. The necessity of considering energy management as a crucial innovation in load supplying to permit a more powerful penetration of renewable energy usage at the building and city level and to perform energy savings and CO2 emissions reduction is pointed out. The driving factors to enhance the current power distribution are presented, and the benefits concerning smart grids are underlined. In the paper, a specific energy management analysis is reported by considering all the electric value chain, and the demand-side management and distributed on site control actions are described. To verify the benefit of energy management control actions, a house simulator and a grid simulator are here presented and the results discussed in three different scenarios. Moreover, in the paper, the evaluation of ecological benefits are reported, and a cost benefit analysis of the energy management system is performed. Results pointed out that with the standard control actions, the system is not economic for the end user, and only by using energy management systems with renewable energy, in site production remunerative energy savings can be reached. Finally the evolution of smart grids is presented, focusing on potential benefits and technical problems. The active grids, microgrids and virtual utility are described, and final consideration on hypothetical scenarios is presented in the conclusion. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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515 KiB

Open AccessArticle

Mitigation of Asymmetrical Grid Faults in Induction Generator-Based Wind Turbines Using Constant Power Load

by Nadeem Jelani and Marta Molinas

Energies 2013, 6(3), 1700-1717; https://doi.org/10.3390/en6031700 - 12 Mar 2013

Cited by 3 | Viewed by 7497

Abstract

Constant power loads (CPLs), interfaced through active rectifiers can be used for improving the stability of induction generator (IG)-based wind turbines under balanced grid voltage dips by providing the reactive power. Under asymmetrical grid faults, the negative sequence voltage produces additional generator torque [...] Read more.

Constant power loads (CPLs), interfaced through active rectifiers can be used for improving the stability of induction generator (IG)-based wind turbines under balanced grid voltage dips by providing the reactive power. Under asymmetrical grid faults, the negative sequence voltage produces additional generator torque oscillations and reduces the lifetime of the installed equipment. This article explores the possibility of using a CPL for mitigation of unbalanced voltage dips in an AC distribution system in addition to consuming a constant active power. Unbalanced fault mitigation as an ancillary service by the load itself could greatly increase the stability and performance of the overall power system. A CPL control structure, capable of controlling the positive and negative sequence of the grid voltage is suggested. The simulation results clearly indicate the effects of compensating the positive and negative sequence of the grid voltage on the performance of IG based wind turbines. The maximum Fault Ride Through (FRT) enhancement has been given priority and is done by the compensation of positive sequence voltage. The remaining CPL current capacity is used to compensate the negative sequence voltage in order to reduce the additional torque ripples in the IG. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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481 KiB

Open AccessArticle

A Novel Routing Algorithm for Power Line Communication over a Low-voltage Distribution Network in a Smart Grid

by Liang Zhang, Xiaosheng Liu, Yan Zhou and Dianguo Xu

Energies 2013, 6(3), 1421-1438; https://doi.org/10.3390/en6031421 - 5 Mar 2013

Cited by 19 | Viewed by 6526

Abstract

A novel artificial cobweb routing algorithm (ACRA) for routing the tree-type physical topology of a low-voltage distribution network in a smart grid is proposed and analyzed in this paper. The establishment, maintenance and reconstruction of the route are presented. The artificial cobweb routing [...] Read more.

A novel artificial cobweb routing algorithm (ACRA) for routing the tree-type physical topology of a low-voltage distribution network in a smart grid is proposed and analyzed in this paper. The establishment, maintenance and reconstruction of the route are presented. The artificial cobweb routing algorithm is shown to have broad general applicability for power line communication. To provide a theoretical foundation for further research, the communication delay of the network is calculated accurately. Simulation analysis of the communication delay and throughputs, which were based on Opnet14.5, demonstrate the accuracy of the theoretical calculation. For the performance evaluation of ACRA, a test-bed that includes PLC nodes with the ACRA is set up in a noisy environment. Experimental results show the feasibility of the ACRA algorithm. These indicate that ACRA is effective for guaranteeing Quality of Service (QoS) and reliability in power line communication. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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647 KiB

Open AccessArticle

Modeling Supermarket Refrigeration Systems for Demand-Side Management

by S. Ehsan Shafiei, Henrik Rasmussen and Jakob Stoustrup

Energies 2013, 6(2), 900-920; https://doi.org/10.3390/en6020900 - 8 Feb 2013

Cited by 47 | Viewed by 10499

Abstract

Modeling of supermarket refrigeration systems for supervisory control in the smart grid is presented in this paper. A modular modeling approach is proposed in which each module is modeled and identified separately. The focus of the work is on estimating the power consumption [...] Read more.

Modeling of supermarket refrigeration systems for supervisory control in the smart grid is presented in this paper. A modular modeling approach is proposed in which each module is modeled and identified separately. The focus of the work is on estimating the power consumption of the system while estimating the cold reservoir temperatures as well. The models developed for each module as well as for the overall integrated system are validated by real data collected from a supermarket in Denmark. The results show that the model is able to estimate the actual electrical power consumption with a high fidelity. Moreover a simulation benchmark is introduced based on the produced model for demand-side management in smart grid. Finally, a potential application of the proposed benchmark in direct control of the power/energy consumption is presented by a simple simulation example. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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1457 KiB

Open AccessArticle

Enhanced Operation of Electricity Distribution Grids Through Smart Metering PLC Network Monitoring, Analysis and Grid Conditioning

by Alberto Sendin, Iñigo Berganza, Aitor Arzuaga, Xabier Osorio, Iker Urrutia and Pablo Angueira

Energies 2013, 6(1), 539-556; https://doi.org/10.3390/en6010539 - 21 Jan 2013

Cited by 37 | Viewed by 9109

Abstract

Low Voltage (LV) electricity distribution grid operations can be improved through a combination of new smart metering systems’ capabilities based on real time Power Line Communications (PLC) and LV grid topology mapping. This paper presents two novel contributions. The first one is a [...] Read more.

Low Voltage (LV) electricity distribution grid operations can be improved through a combination of new smart metering systems’ capabilities based on real time Power Line Communications (PLC) and LV grid topology mapping. This paper presents two novel contributions. The first one is a new methodology developed for smart metering PLC network monitoring and analysis. It can be used to obtain relevant information from the grid, thus adding value to existing smart metering deployments and facilitating utility operational activities. A second contribution describes grid conditioning used to obtain LV feeder and phase identification of all connected smart electric meters. Real time availability of such information may help utilities with grid planning, fault location and a more accurate point of supply management. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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668 KiB

Open AccessArticle

Decisions on Energy Demand Response Option Contracts in Smart Grids Based on Activity-Based Costing and Stochastic Programming

by Seog-Chan Oh and Alfred J. Hildreth

Energies 2013, 6(1), 425-443; https://doi.org/10.3390/en6010425 - 17 Jan 2013

Cited by 23 | Viewed by 6756

Abstract

Smart grids enable a two-way energy demand response capability through which a utility company offers its industrial customers various call options for energy load curtailment. If a customer has the capability to accurately determine whether to accept an offer or not, then in [...] Read more.

Smart grids enable a two-way energy demand response capability through which a utility company offers its industrial customers various call options for energy load curtailment. If a customer has the capability to accurately determine whether to accept an offer or not, then in the case of accepting an offer, the customer can earn both an option premium to participate, and a strike price for load curtailments if requested. However, today most manufacturing companies lack the capability to make the correct contract decisions for given offers. This paper proposes a novel decision model based on activity-based costing (ABC) and stochastic programming, developed to accurately evaluate the impact of load curtailments and determine as to whether or not to accept an energy load curtailment offer. The proposed model specifically targets state-transition flexible and Quality-of-Service (QoS) flexible energy use activities to reduce the peak energy demand rate. An illustrative example with the proposed decision model under a call-option based energy demand response scenario is presented. As shown from the example results, the proposed decision model can be used with emerging smart grid opportunities to provide a competitive advantage to the manufacturing industry. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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1956 KiB

Open AccessArticle

An Efficiency-Optimized Isolated Bidirectional DC-DC Converter with Extended Power Range for Energy Storage Systems in Microgrids

by Xiaolong Shi, Jiuchun Jiang and Xintao Guo

Energies 2013, 6(1), 27-44; https://doi.org/10.3390/en6010027 - 24 Dec 2012

Cited by 39 | Viewed by 8417

Abstract

This paper proposes a novel extended-single-phase shift (ESPS) control strategy of isolated bidirectional full-bridge DC-DC converters (IBDCs) which are a promising alternative as a power electronic interface in microgrids with an additional function of galvanic isolation. Based on the mathematical models of ESPS [...] Read more.

This paper proposes a novel extended-single-phase shift (ESPS) control strategy of isolated bidirectional full-bridge DC-DC converters (IBDCs) which are a promising alternative as a power electronic interface in microgrids with an additional function of galvanic isolation. Based on the mathematical models of ESPS control under steady-state conditions, detailed theoretical and experimental analyses of IBDC under ESPS control are presented. Compared with conventional single-phase-shift (CSPS) control, ESPS control can greatly improve the efficiency of IBDCs in microgrids through decreasing current stress and backflow power considerably over a wide input and output voltage range under light and medium loads. In addition, ESPS control only needs to adjust one single phase-shift angel to control transmission power, thus it retains implementation simplicity in comparison with dual-phase-shift (DPS) control for microgrid applications. Furthermore, an efficiency-optimized modulation scheme based on ESPS and CSPS control is developed in the whole power range of IBDC for power distribution in microgrids. A 10 kW IBDC prototype is constructed and the experimental results validate the effectiveness of the proposed control strategy, showing that the proposed strategy can enhance the overall efficiency up to 30%. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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706 KiB

Open AccessArticle

Operation and Power Flow Control of Multi-Terminal DC Networks for Grid Integration of Offshore Wind Farms Using Genetic Algorithms

by Rodrigo Teixeira Pinto, Sílvio Fragoso Rodrigues, Edwin Wiggelinkhuizen, Ricardo Scherrer, Pavol Bauer and Jan Pierik

Energies 2013, 6(1), 1-26; https://doi.org/10.3390/en6010001 - 24 Dec 2012

Cited by 41 | Viewed by 8873

Abstract

For achieving the European renewable electricity targets, a significant contribution is foreseen to come from offshore wind energy. Considering the large scale of the future planned offshore wind farms and the increasing distances to shore, grid integration through a transnational DC network is [...] Read more.

For achieving the European renewable electricity targets, a significant contribution is foreseen to come from offshore wind energy. Considering the large scale of the future planned offshore wind farms and the increasing distances to shore, grid integration through a transnational DC network is desirable for several reasons. This article investigates a nine-node DC grid connecting three northern European countries — namely UK, The Netherlands and Germany. The power-flow control inside the multi-terminal DC grid based on voltage-source converters is achieved through a novel method, called distributed voltage control (DVC). In this method, an optimal power flow (OPF) is solved in order to minimize the transmission losses in the network. The main contribution of the paper is the utilization of a genetic algorithm (GA) to solve the OPF problem while maintaining an N-1 security constraint. After describing main DC network component models, several case studies illustrate the dynamic behavior of the proposed control method. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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1530 KiB

Open AccessArticle

Power Quality and Harmonic Analysis of End User Devices

by Alberto Dolara and Sonia Leva

Energies 2012, 5(12), 5453-5466; https://doi.org/10.3390/en5125453 - 19 Dec 2012

Cited by 71 | Viewed by 8161

Abstract

Among the non-linear loads used in household, Compact Fluorescent Lamps (CFLs) and LED lamps are becoming more widespread, while incandescent lamps are intended to be replaced by these types of lighting devices. LEDs and CFLs are significantly more efficient and economical than incandescent [...] Read more.

Among the non-linear loads used in household, Compact Fluorescent Lamps (CFLs) and LED lamps are becoming more widespread, while incandescent lamps are intended to be replaced by these types of lighting devices. LEDs and CFLs are significantly more efficient and economical than incandescent lamps, and are expected to be used in 100% of residential lighting in the future. As nonlinear loads, LEDs and CFLs produce highly distorted currents. A large number of customers using LEDs or CFLs for domestic, commercial and industrial lighting could determine important Power Quality problems. The paper reports experimental measurement results regarding Power Quality in indoor lighting systems. The harmonic absorptions of several types of luminaries are analyzed, highlighting the impact behavior of different lamps function of used luminaries’ technologies. The recorded harmonic absorption allows characterizing the harmonic spectrum variability of the investigated lamps. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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3304 KiB

Open AccessArticle

Classification and Clustering of Electricity Demand Patterns in Industrial Parks

by Luis Hernández, Carlos Baladrón, Javier M. Aguiar, Belén Carro and Antonio Sánchez-Esguevillas

Energies 2012, 5(12), 5215-5228; https://doi.org/10.3390/en5125215 - 12 Dec 2012

Cited by 99 | Viewed by 8587

Abstract

Understanding of energy consumption patterns is extremely important for optimization of resources and application of green trends. Traditionally, analyses were performed for large environments like regions and nations. However, with the advent of Smart Grids, the study of the behavior of smaller environments [...] Read more.

Understanding of energy consumption patterns is extremely important for optimization of resources and application of green trends. Traditionally, analyses were performed for large environments like regions and nations. However, with the advent of Smart Grids, the study of the behavior of smaller environments has become a necessity to allow a deeper micromanagement of the energy grid. This paper presents a data processing system to analyze energy consumption patterns in industrial parks, based on the cascade application of a Self-Organizing Map (SOM) and the clustering k-means algorithm. The system is validated with real load data from an industrial park in Spain. The validation results show that the system adequately finds different behavior patterns which are meaningful, and is capable of doing so without supervision, and without any prior knowledge about the data. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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265 KiB

Open AccessArticle

Fault Location in Power Electrical Traction Line System

by Yimin Zhou, Guoqing Xu and Yanfeng Chen

Energies 2012, 5(12), 5002-5018; https://doi.org/10.3390/en5125002 - 26 Nov 2012

Cited by 16 | Viewed by 7466

Abstract

In this paper, methods of fault location are discussed in electrical traction single-end direct power supply network systems. Based on the distributed parameter model of the system, the position of the short-circuit fault can be located with the aid of the current and [...] Read more.

In this paper, methods of fault location are discussed in electrical traction single-end direct power supply network systems. Based on the distributed parameter model of the system, the position of the short-circuit fault can be located with the aid of the current and voltage value at the measurement end of the electrical traction line. Furthermore, the influence of the transient resistance, the position of the locomotive, locomotive load for fault location are also discussed. MATLAB simulation tool is used for the simulation experiments. Simulation results are proved the effectiveness of the proposed algorithms. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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672 KiB

Open AccessArticle

Distributed Semantic Architecture for Smart Grids

by Yoseba K. Penya, Juan Carlos Nieves, Angelina Espinoza, Cruz E. Borges, Aitor Peña and Mariano Ortega

Energies 2012, 5(11), 4824-4843; https://doi.org/10.3390/en5114824 - 20 Nov 2012

Cited by 17 | Viewed by 8276

Abstract

The smart grid revolution demands a huge effort in redesigning and enhancing current power networks, as well as integrating emerging scenarios such as distributed generation, renewable energies or the electric vehicle. This novel situation will cause a huge flood of data that can [...] Read more.

The smart grid revolution demands a huge effort in redesigning and enhancing current power networks, as well as integrating emerging scenarios such as distributed generation, renewable energies or the electric vehicle. This novel situation will cause a huge flood of data that can only be handled, processed and exploited in real-time with the help of cutting-edge ICT (Information and Communication Technologies). We present here a new architecture that, contrary to the previous centralised and static model, distributes the intelligence all over the grid by means of individual intelligent nodes controlling a number of electric assets. The nodes own a profile of the standard smart grid ontology stored in the knowledge base with the inferred information about their environment in RDF triples. Since the system does not have a central registry or a service directory, the connectivity emerges from the view of the world semantically encoded by each individual intelligent node (i.e., profile + inferred information). We have described a use-case both with and without real-time requirements to illustrate and validate this novel approach. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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781 KiB

Open AccessArticle

A PEV Charging Service Model for Smart Grids

by Khaled Shuaib, Liren Zhang, Ahmed Gaouda and Mohammed Abdel-Hafez

Energies 2012, 5(11), 4665-4682; https://doi.org/10.3390/en5114665 - 16 Nov 2012

Cited by 15 | Viewed by 6364

Abstract

Plug-in Electric Vehicles (PEVs) are envisioned to be more popular during the next decade as part of Smart Grid implementations. Charging multiple PEVs at the same time within a power distribution area constitutes a major challenge for energy service providers. This paper discusses [...] Read more.

Plug-in Electric Vehicles (PEVs) are envisioned to be more popular during the next decade as part of Smart Grid implementations. Charging multiple PEVs at the same time within a power distribution area constitutes a major challenge for energy service providers. This paper discusses a priority-based approach for charging PEVs in a Smart Grid environment. In this work, ideas from the communication network paradigm are being utilized and tailored toward achieving the desired objective of monitoring and controlling PEVs electric load in Smart Grid. A detailed example is given to show how uncontrolled penetration of PEVs can impact distribution transformer reliability. The paper introduces the concept of Charging Quality of Service (CQoS) as a smart electric vehicle charging scheme and models it using a priority-controlled leaky bucket approach. The performance of such a model is investigated under the umbrella of a Smart Grid environment. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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2020 KiB

Open AccessArticle

Non-Intrusive Demand Monitoring and Load Identification for Energy Management Systems Based on Transient Feature Analyses

by Hsueh-Hsien Chang

Energies 2012, 5(11), 4569-4589; https://doi.org/10.3390/en5114569 - 14 Nov 2012

Cited by 141 | Viewed by 9874

Abstract

Energy management systems strive to use energy resources efficiently, save energy, and reduce carbon output. This study proposes transient feature analyses of the transient response time and transient energy on the power signatures of non-intrusive demand monitoring and load identification to detect the [...] Read more.

Energy management systems strive to use energy resources efficiently, save energy, and reduce carbon output. This study proposes transient feature analyses of the transient response time and transient energy on the power signatures of non-intrusive demand monitoring and load identification to detect the power demand and load operation. This study uses the wavelet transform (WT) of the time-frequency domain to analyze and detect the transient physical behavior of loads during the load identification. The experimental results show the transient response time and transient energy are better than the steady-state features to improve the recognition accuracy and reduces computation requirements in non-intrusive load monitoring (NILM) systems. The discrete wavelet transform (DWT) is more suitable than short-time Fourier transform (STFT) for transient load analyses. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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462 KiB

Open AccessArticle

Supplementary Controller Design for SSR Damping in a Series-Compensated DFIG-Based Wind Farm

by Zaijun Wu, Chanxia Zhu and Minqiang Hu

Energies 2012, 5(11), 4481-4496; https://doi.org/10.3390/en5114481 - 13 Nov 2012

Cited by 6 | Viewed by 5907

Abstract

The increasing presence of wind power in power systems will likely drive the integration of large wind farms with electrical networks that are series-compensated to sustain large power flows. This may potentially lead to subsynchronous resonance (SSR) issues. In this paper, a supplementary [...] Read more.

The increasing presence of wind power in power systems will likely drive the integration of large wind farms with electrical networks that are series-compensated to sustain large power flows. This may potentially lead to subsynchronous resonance (SSR) issues. In this paper, a supplementary controller on the grid-side converter (GSC) control loop is designed to mitigate SSR for wind power systems based on doubly fed induction generators (DFIGs) with back-to-back converters. Different supplementary controller feedback signals and modulated-voltage injecting points are proposed and compared based on modal analysis and verified through root locus analysis to identify the optimal feedback signal and the most effective control location for SSR damping. The validity and effectiveness of the proposed supplemental control are demonstrated on the IEEE first benchmark model for computer simulations of SSR by means of time domain simulation analysis using Matlab/Simulink. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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661 KiB

Open AccessArticle

Intrusion Detection of NSM Based DoS Attacks Using Data Mining in Smart Grid

by Kyung Choi, Xinyi Chen, Shi Li, Mihui Kim, Kijoon Chae and JungChan Na

Energies 2012, 5(10), 4091-4109; https://doi.org/10.3390/en5104091 - 19 Oct 2012

Cited by 33 | Viewed by 9146

Abstract

In this paper, we analyze the Network and System Management (NSM) requirements and NSM data objects for the intrusion detection of power systems; NSM is an IEC 62351-7 standard. We analyze a SYN flood attack and a buffer overflow attack to cause the [...] Read more.

In this paper, we analyze the Network and System Management (NSM) requirements and NSM data objects for the intrusion detection of power systems; NSM is an IEC 62351-7 standard. We analyze a SYN flood attack and a buffer overflow attack to cause the Denial of Service (DoS) attack described in NSM. After mounting the attack in our attack testbed, we collect a data set, which is based on attributes for the attack. We then run several data mining methods with the data set using the Waikato Environment for Knowledge Analysis (WEKA). In the results, we select the decision tree algorithms with high detection rates, and choose key attributes in high level components of the trees. When we run several data mining methods again with the data set of chosen key attributes, the detection rates of most data mining methods are higher than before. We prove that our selected attack attributes, and the proposed detection process, are efficient and suitable for intrusion detection in the smart grid environment. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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4199 KiB

Open AccessArticle

Visions, Scenarios and Action Plans Towards Next Generation Tanzania Power System

by Santos Kihwele, Kyeon Hur and Alex Kyaruzi

Energies 2012, 5(10), 3908-3927; https://doi.org/10.3390/en5103908 - 16 Oct 2012

Cited by 21 | Viewed by 9613

Abstract

This paper presents strategic visions, scenarios and action plans for enhancing Tanzania Power Systems towards next generation Smart Power Grid. It first introduces the present Tanzanian power grid and the challenges ahead in terms of generation capacity, financial aspect, technical and non-technical losses, [...] Read more.

This paper presents strategic visions, scenarios and action plans for enhancing Tanzania Power Systems towards next generation Smart Power Grid. It first introduces the present Tanzanian power grid and the challenges ahead in terms of generation capacity, financial aspect, technical and non-technical losses, revenue loss, high tariff, aging infrastructure, environmental impact and the interconnection with the neighboring countries. Then, the current initiatives undertaken by the Tanzania government in response to the present challenges and the expected roles of smart grid in overcoming these challenges in the future with respect to the scenarios presented are discussed. The developed scenarios along with visions and recommended action plans towards the future Tanzanian power system can be exploited at all governmental levels to achieve public policy goals and help develop business opportunities by motivating domestic and international investments in modernizing the nation’s electric power infrastructure. In return, it should help build the green energy economy. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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1555 KiB

Open AccessArticle

Minimization of Losses in Smart Grids Using Coordinated Voltage Control

by Marko Kolenc, Igor Papič and Boštjan Blažič

Energies 2012, 5(10), 3768-3787; https://doi.org/10.3390/en5103768 - 27 Sep 2012

Cited by 16 | Viewed by 6952

Abstract

This article deals with the influence of distributed generation (DG) on distribution line losses with respect to voltage profile. The article focuses on the development of a control strategy to minimize the grid losses and assure fairness regarding reactive power contributions. As retail [...] Read more.

This article deals with the influence of distributed generation (DG) on distribution line losses with respect to voltage profile. The article focuses on the development of a control strategy to minimize the grid losses and assure fairness regarding reactive power contributions. As retail customers typically have no choice where they are located along a feeder, it seems unfair that only some of them bear all the burden and responsibility for the voltage rise. On the basis of new technologies, which are capable of fast communication and data processing, a new control system has been proposed that combines classical centralized and local control. The heart of the control system is a load‑flow algorithm, which estimates the voltage drop using a modeled network. Different control solutions were evaluated by means of computer simulations. The simulated network is an actual Slovenian medium-voltage distribution network which covers a large area with diverse feeders and thus gives relatively general results. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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574 KiB

Open AccessArticle

An Innovative Reconfigurable Integrated Converter Topology Suitable for Distributed Generation

by Renato Rizzo, Pietro Tricoli and Ivan Spina

Energies 2012, 5(9), 3640-3654; https://doi.org/10.3390/en5093640 - 18 Sep 2012

Cited by 26 | Viewed by 6494

Abstract

The electricity market and environmental concerns, with wide utilization of renewable sources, have improved the diffusion of distributed generation units changing the operations of distribution grids from passive networks to microgrids. A microgrid includes a cluster of electrical loads, energy storage devices and [...] Read more.

The electricity market and environmental concerns, with wide utilization of renewable sources, have improved the diffusion of distributed generation units changing the operations of distribution grids from passive networks to microgrids. A microgrid includes a cluster of electrical loads, energy storage devices and microsources, which provide both power and heat to their local area. A microgrid has usually one connection point to the utility grid through power electronic converters placed at customers’ sites. This paper analyses a Reconfigurable Integrated Converter (RIC) used for a domestic microgrid with inputs from the AC mains and photovoltaic arrays, and two DC outputs at different voltage levels. A RIC as a dual-boost DC-DC converter is proposed, modelled and analysed in the paper. The advantages of such a topology in comparison with traditional boost converters are outlined. Reported simulations results give evidence on the controllability of this converter and the capability of achieving the desired voltage outputs with reduced ripple. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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3051 KiB

Open AccessArticle

A Practical Protection Coordination Strategy Applied to Secondary and Facility Microgrids

by Dae-Geun Jin, Jong-Chan Choi, Dong-Jun Won, Hak-Ju Lee, Woo-Kyu Chae and Jung-Sung Park

Energies 2012, 5(9), 3248-3265; https://doi.org/10.3390/en5093248 - 30 Aug 2012

Cited by 12 | Viewed by 5798

Abstract

In a conventional distribution system, protection algorithms are designed to operate on a unidirectional high fault-current level. In a microgrid, a fault current from distributed generation (DG) may bring about a relay malfunction because of the bidirectional and relatively small fault current. Therefore, [...] Read more.

In a conventional distribution system, protection algorithms are designed to operate on a unidirectional high fault-current level. In a microgrid, a fault current from distributed generation (DG) may bring about a relay malfunction because of the bidirectional and relatively small fault current. Therefore, the conventional protection scheme is not applicable to microgrids and a new protection method must be developed. In this paper, two protection coordination algorithms which can be applied for facility and secondary microgrids are proposed, respectively. The proposed protection algorithms eliminate faults not by the EMS signal but by directional relays. Moreover, this makes the algorithms flexible regardless of the types and numbers of DG. The proposed protection algorithms were simulated at the KEPCO RI Microgrid Demonstration Site. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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945 KiB

Open AccessArticle

Nonintrusive Energy Monitoring for Microgrids Using Hybrid Self-Organizing Feature-Mapping Networks

by Ying-Yi Hong and Jing-Han Chou

Energies 2012, 5(7), 2578-2593; https://doi.org/10.3390/en5072578 - 18 Jul 2012

Cited by 24 | Viewed by 6402

Abstract

Microgrids can increase power penetration from distributed generation (DG) in the power system. The interface (i.e., the point of common coupling, PCC) between the microgrid and the power utility must satisfy certain standards, such as IEEE Sd. 1547. Energy monitoring of [...] Read more.

Microgrids can increase power penetration from distributed generation (DG) in the power system. The interface (i.e., the point of common coupling, PCC) between the microgrid and the power utility must satisfy certain standards, such as IEEE Sd. 1547. Energy monitoring of the microgrid at the PCC by the power utility is crucial if the utility cannot install advanced meters at different locations in the microgrid (e.g., a factory). This paper presents a new nonintrusive energy monitoring method using a hybrid self-organizing feature-mapping neural network (SOFMNN). The components of the FFT spectra for voltage, current, kW and kVAR, measured at the PCC, serve as the signatures for the hybrid SOFMNN inputs. The nonintrusive energy monitoring at the PCC identifies different load levels for individual linear/nonlinear loads and output levels for wind power generators in the microgrid. Using this energy monitoring result, the power utility can establish an energy management policy. The simulation results from a microgrid, consisting of a diesel generator, a wind-turbine-generator, a rectifier and a cyclo-converter, show the practicability of the proposed method. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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Review

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348 KiB

Open AccessReview

A Generic Framework for the Evaluation of the Benefits Expected from the Smart Grid

by Spiros Livieratos, Vasiliki-Emmanouela Vogiatzaki and Panayotis G. Cottis

Energies 2013, 6(2), 988-1008; https://doi.org/10.3390/en6020988 - 13 Feb 2013

Cited by 27 | Viewed by 8401

Abstract

The Smart Grid has the potential to bring significant value to the various stakeholders of the electricity market. A methodology for the evaluation of the smart grid benefits is required to facilitate the decision making by quantifying the benefits expected from a smart [...] Read more.

The Smart Grid has the potential to bring significant value to the various stakeholders of the electricity market. A methodology for the evaluation of the smart grid benefits is required to facilitate the decision making by quantifying the benefits expected from a smart grid project. The present paper proposes a generic framework to assess these expected benefits taking into account the regulatory, business and technical challenges focusing particularly on Distributed Systems Operators (DSOs) and end users. An indicative study case is presented where the proposed cost-benefit approach assesses the expected value of DSOs from the Smart Grid and determines whether and under what conditions such an investment should be initiated. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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2226 KiB

Open AccessReview

Smart Grid Technologies in Europe: An Overview

by Luca Ardito, Giuseppe Procaccianti, Giuseppe Menga and Maurizio Morisio

Energies 2013, 6(1), 251-281; https://doi.org/10.3390/en6010251 - 9 Jan 2013

Cited by 88 | Viewed by 12775

Abstract

The old electricity network infrastructure has proven to be inadequate, with respect to modern challenges such as alternative energy sources, electricity demand and energy saving policies. Moreover, Information and Communication Technologies (ICT) seem to have reached an adequate level of reliability and flexibility [...] Read more.

The old electricity network infrastructure has proven to be inadequate, with respect to modern challenges such as alternative energy sources, electricity demand and energy saving policies. Moreover, Information and Communication Technologies (ICT) seem to have reached an adequate level of reliability and flexibility in order to support a new concept of electricity network — the smart grid. In this work, we will analyse the state-of-the-art of smart grids, in their technical, management, security, and optimization aspects. We will also provide a brief overview of the regulatory aspects involved in the development of a smart grid, mainly from the viewpoint of the European Union. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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