Electricity

2024

Jump to: 2023, 2022, 2021

22 pages, 3927 KiB

Open AccessArticle

Increasing Renewable Energy Penetration on Low-Voltage Networks: An Expert Knowledge Approach

by Lohan A. Jansen, Mel G. Botha, George van Schoor and Kenneth R. Uren

Electricity 2024, 5(4), 804-825; https://doi.org/10.3390/electricity5040040 - 31 Oct 2024

Viewed by 478

Abstract

While South Africa is deemed one of the countries with the highest irradiation levels, it still utilises coal as its primary energy source due to its abundance. Due to the world-wide drive towards carbon neutrality, residential, commercial, agricultural, and industrial consumers are considering [...] Read more.

While South Africa is deemed one of the countries with the highest irradiation levels, it still utilises coal as its primary energy source due to its abundance. Due to the world-wide drive towards carbon neutrality, residential, commercial, agricultural, and industrial consumers are considering small-scale embedded generation systems. The National Rationalised Specifications 097-2-3 document specifies the scale of the embedded generation capacity a consumer is allowed to install. However, specifications do not yet make the required provisions for the addition of energy storage. The effective collective management of the grouped small-scale embedded generation systems could provide a high level of energy security and increase the percentage of renewable energy generation in the total energy mix. Potential challenges come into play when considering the stochastic nature of photovoltaic generation and its effect on the storage capacity and the dispersion in load profiles of the residential units typically present on a low-voltage network. This paper contributes by investigating the utilisation of photovoltaic generation in conjunction with storage as the basis for virtual power plant control, with the aim to safely increase renewable energy penetration and improve energy security, all while remaining within the South African low-voltage regulatory limits. A two-level virtual power plant controller is proposed with the dispersed energy storage units as the primary controllable resources and the dispersed photovoltaic generation as the secondary controllable resources. The objective of the controller is to achieve nodal energy management, energy sharing, and ancillary service provision and finally to increase renewable energy penetration. A representative single-feeder low-voltage network is simulated, and test cases of 50% and 75% renewable energy penetration are investigated as the basis for evaluation. The proposed controller architecture proved to maintain network integrity for both test cases. The adaptability of the controller architecture was also confirmed for a changed feeder topology; in this case, it was a multi-feeder topology. Future work is warranted to inform policy on the allowed levels of renewable energy penetration to be based not only on demand but also on the level of energy storage present in a network. Full article

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37 pages, 25724 KiB

Open AccessArticle

Development of a New Modelling Concept for Power Flow Calculations across Voltage Levels

by Tobias Riedlinger, Patrick Wintzek and Markus Zdrallek

Electricity 2024, 5(2), 174-210; https://doi.org/10.3390/electricity5020010 - 1 Apr 2024

Viewed by 1359

Abstract

In the context of the energy transition, the share of new loads such as charging infrastructure for electromobility and electric heat pumps as well as feed-ins such as photovoltaic systems will steadily increase. This results in an increased degree of complexity for strategic [...] Read more.

In the context of the energy transition, the share of new loads such as charging infrastructure for electromobility and electric heat pumps as well as feed-ins such as photovoltaic systems will steadily increase. This results in an increased degree of complexity for strategic network planning. In particular, the power flow analyses for the dimensioning of transformers and lines per network level currently still require different methods for the correct dimensioning of these equipment. They need to be carried out in separate data sets. For the dimensioning of the equipment simultaneity factors are predominantly used for realistic load assumptions in strategic network planning. These simultaneity factors and resulting load assumptions are determined from the planning perspective of the transformers and from the planning perspective of the lines per network level to be able to dimension the corresponding equipment. This results in different power flow results for the analysis and evaluation of different network levels in particular. This contribution presents a new concept for network modelling in which the simultaneity of the different planning perspectives of the different network levels results from a single power flow calculation in a coherent data set. Full article

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20 pages, 9241 KiB

Open AccessArticle

Decentralised Voltage Regulation through Optimal Reactive Power Flow in Distribution Networks with Dispersed Generation

by Edoardo Daccò, Davide Falabretti, Valentin Ilea, Marco Merlo, Riccardo Nebuloni and Matteo Spiller

Electricity 2024, 5(1), 134-153; https://doi.org/10.3390/electricity5010008 - 12 Mar 2024

Cited by 5 | Viewed by 2120

Abstract

The global capacity for renewable electricity generation has surged, with distributed photovoltaic generation being the primary driver. The increasing penetration of non-programmable renewable Distributed Energy Resources (DERs) presents challenges for properly managing distribution networks, requiring advanced voltage regulation techniques. This paper proposes an [...] Read more.

The global capacity for renewable electricity generation has surged, with distributed photovoltaic generation being the primary driver. The increasing penetration of non-programmable renewable Distributed Energy Resources (DERs) presents challenges for properly managing distribution networks, requiring advanced voltage regulation techniques. This paper proposes an innovative decentralised voltage strategy that considers DERs, particularly inverter-based ones, as autonomous regulators in compliance with the state-of-the-art European technical standards and grid codes. The proposed method uses an optimal reactive power flow that minimises voltage deviations along all the medium voltage nodes; to check the algorithm’s performance, it has been applied to a small-scale test network and on a real Italian medium-voltage distribution network, and compared with a fully centralised ORPF. The results show that the proposed decentralised autonomous strategy effectively improves voltage profiles in both case studies, reducing voltage deviation by a few percentage points; these results are further confirmed through an analysis conducted over several days to observe how seasons affect the results. Full article

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2023

Jump to: 2024, 2022, 2021

17 pages, 618 KiB

Open AccessArticle

Events Classification in Power Systems with Distributed Generation Sources Using an LSTM-Based Method with Multi-Input Tensor Approach

by Oswaldo Cortes-Robles, Emilio Barocio, Ernesto Beltran and Ramon Daniel Rodríguez-Soto

Electricity 2023, 4(4), 410-426; https://doi.org/10.3390/electricity4040022 - 5 Dec 2023

Cited by 2 | Viewed by 1499

Abstract

In this paper, a long short-term memory (LSTM)-based method with a multi-input tensor approach is used for the classification of events that affect the power quality (PQ) in power systems with distributed generation sources. The considered events are line faults (one line, two [...] Read more.

In this paper, a long short-term memory (LSTM)-based method with a multi-input tensor approach is used for the classification of events that affect the power quality (PQ) in power systems with distributed generation sources. The considered events are line faults (one line, two lines, and three lines faulted), islanding events, sudden load variations, and generation tripping. The proposed LSTM-based method was trained and tested using the signals produced by the events simulated in a study system with distributed generation sources via PSCAD^®. Then, noise with different levels was added to the testing set for a thorough assessment, and the results were compared with other well-known methods such as convolutional and simple recurrent neuronal networks. The LSTM-based method with multi-input proved to be effective for event classification, achieving remarkable classification performance even in noisy conditions. Full article

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18 pages, 1823 KiB

Open AccessArticle

Incremental Phase-Current Based Fault Passage Indication for Earth Faults in Resonant Earthed Networks

by Md Zakaria Habib and Nathaniel Taylor

Electricity 2023, 4(2), 96-113; https://doi.org/10.3390/electricity4020007 - 24 Mar 2023

Cited by 1 | Viewed by 2561

Abstract

We propose a method for the fault passage indication of earth faults in resonant-earthed networks, based on phase current measurements alone. This is particularly relevant for electricity distribution systems at medium-voltage levels. The method is based on the relative magnitudes of the phasor [...] Read more.

We propose a method for the fault passage indication of earth faults in resonant-earthed networks, based on phase current measurements alone. This is particularly relevant for electricity distribution systems at medium-voltage levels. The method is based on the relative magnitudes of the phasor changes in the phase currents due to the fault. It is tested for various network types and operation configurations by simulating the network in pscad and using the simulated currents as the input for an implementation of the method in matlab. In over-compensated networks, the method shows reliable detection of the fault passage, with good selectivity and sensitivity for both homogeneous and mixed (cable and overhead line) feeders. However, for the less common under-compensated systems, it has limitations that are described further in this study. The method has good potential for being cost effective since it requires only current measurements, from a single location, at a moderate sampling rate. Full article

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18 pages, 15530 KiB

Open AccessArticle

Achieving Optimal Reactive Power Compensation in Distribution Grids by Using Industrial Compensation Systems

by Johannes Rauch and Oliver Brückl

Electricity 2023, 4(1), 78-95; https://doi.org/10.3390/electricity4010006 - 2 Mar 2023

Cited by 4 | Viewed by 3534

Abstract

This paper presents a method for integrating industrial consumers owning compensation systems as alternative reactive power sources into grid operating processes. In remuneration, they receive a market-based provision of reactive power. The aim is to analyze the potential of reactive power compensation systems [...] Read more.

This paper presents a method for integrating industrial consumers owning compensation systems as alternative reactive power sources into grid operating processes. In remuneration, they receive a market-based provision of reactive power. The aim is to analyze the potential of reactive power compensation systems of industrial companies connected to medium-voltage (10 kV–30 kV) AC grids in order to increase the reactive power ability of distribution grids. Measurement methods and reactive power potential results of six industrial companies are presented to characterize the amount and temporal availability of their reactive power potential. The presented approach for using the decentralized reactive power potential is a centralized reactive power control method and is based on optimal power flow (OPF) calculations. An optimization algorithm based on linear programming is used to coordinate a reactive power retrieval tuned to the actual demand. The influencing quantities are the current grid status (voltage and load flow capacity reserves at grid nodes and power lines) and the current reactive power potential of the reactive power sources. The compensation impact of six measured industrial companies on an exemplary medium-voltage grid is shown by an application example. Full article

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2022

Jump to: 2024, 2023, 2021

37 pages, 4545 KiB

Open AccessArticle

Deduction of Strategic Planning Guidelines for Urban Medium Voltage Grids with Consideration of Electromobility and Heat Pumps

by Shawki Ali, Patrick Wintzek, Markus Zdrallek, Julian Monscheidt, Ben Gemsjäger and Adam Slupinski

Electricity 2022, 3(4), 505-541; https://doi.org/10.3390/electricity3040026 - 9 Oct 2022

Cited by 1 | Viewed by 2600

Abstract

With the evolution of electromobility and heat pumps in urban areas, distribution system operators find themselves facing new challenges in reinforcing their grids. With this evolution, the power demand is developing rapidly and grid reinforcement is urgently needed. The electromobility and heat pump [...] Read more.

With the evolution of electromobility and heat pumps in urban areas, distribution system operators find themselves facing new challenges in reinforcing their grids. With this evolution, the power demand is developing rapidly and grid reinforcement is urgently needed. The electromobility and heat pump loads are introduced by giving the assumed development scenarios in Germany and their corresponding nominal power assumptions. Furthermore, a method for load modeling in grid planning is explained. Subsequently, several grid planning approaches are presented while dividing them into conventional and innovative planning strategies. Among the investigated innovative planning strategies are three variants of load management that regulate different load types. By analyzing several urban medium voltage grids, this contribution deduces a solid basis for distribution system operators in the form of planning guidelines. The implemented grid planning method leading to the planning guidelines is presented in detail along the contribution. Full article

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19 pages, 1947 KiB

Open AccessArticle

Optimal Coordinated Control of DC Microgrid Based on Hybrid PSO–GWO Algorithm

by Zaid Hamid Abdulabbas Al-Tameemi, Tek Tjing Lie, Gilbert Foo and Frede Blaabjerg

Electricity 2022, 3(3), 346-364; https://doi.org/10.3390/electricity3030019 - 8 Aug 2022

Cited by 20 | Viewed by 3027

Abstract

Microgrids (MGs) are capable of playing an important role in the future of intelligent energy systems. This can be achieved by allowing the effective and seamless integration of distributed energy resources (DERs) loads, besides energy-storage systems (ESS) in the local area, so they [...] Read more.

Microgrids (MGs) are capable of playing an important role in the future of intelligent energy systems. This can be achieved by allowing the effective and seamless integration of distributed energy resources (DERs) loads, besides energy-storage systems (ESS) in the local area, so they are gaining attraction worldwide. In this regard, a DC MG is an economical, flexible, and dependable solution requiring a trustworthy control structure such as a hierarchical control strategy to be appropriately coordinated and used to electrify remote areas. Two control layers are involved in the hierarchy control strategy, including local- and global-control levels. However, this research focuses mainly on the issues of DC MG’s local control layer under various load interruptions and power-production fluctuations, including inaccurate power-sharing among sources and unregulated DC-bus voltage of the microgrid, along with a high ripple of battery current. Therefore, this work suggests developing local control levels for the DC MG based on the hybrid particle swarm optimization/grey wolf optimizer (HPSO–GWO) algorithm to address these problems. The key results of the simulation studies reveal that the proposed control scheme has achieved significant improvement in terms of voltage adjustment and power distribution between photovoltaic (PV) and battery technologies accompanied by a supercapacitor, in comparison to the existing control scheme. Moreover, the settling time and overshoot/undershoot are minimized despite the tremendous load and generation variations, which proves the proposed method’s efficiency. Full article

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16 pages, 2326 KiB

Open AccessFeature PaperArticle

Impact of Increased Penetration of Low-Carbon Technologies on Cable Lifetime Estimations

by Xu Jiang, Edward Corr, Bruce Stephen and Brian G. Stewart

Electricity 2022, 3(2), 220-235; https://doi.org/10.3390/electricity3020013 - 27 May 2022

Cited by 1 | Viewed by 3090

Abstract

Cables are the largest assets by volume on power distribution networks and the assets with the least health information routinely gathered. Projections over the next 8 years suggest increased penetration of low-carbon technology (LCT) at the distribution level with higher loads resulting from [...] Read more.

Cables are the largest assets by volume on power distribution networks and the assets with the least health information routinely gathered. Projections over the next 8 years suggest increased penetration of low-carbon technology (LCT) at the distribution level with higher loads resulting from electric vehicle (EV) and heat pump uptake. Over this period, increased cable loading will directly influence their lifetimes and may mean that existing asset management practices need to be revised to understand the specific impact on end-of-life assessment. Accordingly, this paper uses a physics-based thermal lifetime model based on projected uptake trends for LCTs to evaluate the impact on distribution cable lifetime. Two case studies are presented considering portions of network and the ultimate impact on asset life over the next decade. Two commonly used cables are considered to quantify the lifetime reduction caused by LCT for asset fleets. The paper shows that the projected uptake of EVs and heat pumps will have a detrimental effect on cable life with a 30% reduction in cable lifetime possible. Full article

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20 pages, 4661 KiB

Open AccessArticle

Determination of Dynamic Characteristics for Predicting Electrical Load Curves of Mining Enterprises

by Denis Anatolievich Ustinov and Konstantin Alekseevich Khomiakov

Electricity 2022, 3(2), 162-181; https://doi.org/10.3390/electricity3020010 - 8 Apr 2022

Cited by 3 | Viewed by 3725

Abstract

The calculation of electrical loads is the first and most significant stage in the design of the power supply system. It is essential to make the right choice when choosing the power electrical equipment: transformers, power lines, and switching devices. Underestimation or overestimation [...] Read more.

The calculation of electrical loads is the first and most significant stage in the design of the power supply system. It is essential to make the right choice when choosing the power electrical equipment: transformers, power lines, and switching devices. Underestimation or overestimation of the calculated values can lead to large losses and an increase in capital costs. Therefore, the reliability of the results plays a key role. The use of energy-saving technologies and energy-efficient electrical equipment leads to a change in the nature and level of power consumption, which must be taken into account when determining the electrical loads. The existing methods leave out dynamic characteristics of electrical load curves, so the calculated values are overestimated by up to 40%. This study shows a load calculation method with the normalized correlation functions and its parameters at the level of the individual and group electricity consumers. As a result, the difference between the calculated and experimental values does not exceed 5%. Full article

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18 pages, 692 KiB

Open AccessArticle

Model Predictive Operation Control of Islanded Microgrids under Nonlinear Conversion Losses of Storage Units

by Milad Gholami and Alessandro Pisano

Electricity 2022, 3(1), 33-50; https://doi.org/10.3390/electricity3010003 - 26 Jan 2022

Cited by 6 | Viewed by 3192

Abstract

This paper proposes a certainty equivalence model predictive control (MPC) approach for the operation of islanded microgrids with a very high share of renewable energy sources. First, to make the MG model more realistic, the conversion losses of the storage units and the [...] Read more.

This paper proposes a certainty equivalence model predictive control (MPC) approach for the operation of islanded microgrids with a very high share of renewable energy sources. First, to make the MG model more realistic, the conversion losses of the storage units and the conversion losses of the power electronic devices are considered by the quadratic functions in the dynamic of units. Then, to mitigate the effect of errors in the storage units’ state of charge prediction, the conversion loss functions are reformulated by the mixed-integer linear inequality functions and included in the proposed scheme. Finally, the effectiveness of the proposed certainty MPC is verified by a numerical case study. Full article

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2021

Jump to: 2024, 2023, 2022

15 pages, 7584 KiB

Open AccessArticle

Conception of High-Frequency Power Planar Transformer Prototypes Based on FabLab Platform

by Simon Thomy, Xavier Margueron, Jean-Sylvio Ngoua Teu Magambo, Reda Bakri and Philippe Le Moigne

Electricity 2022, 3(1), 1-15; https://doi.org/10.3390/electricity3010001 - 21 Dec 2021

Cited by 1 | Viewed by 8214

Abstract

Conceiving planar magnetic components for power electronic converters is very constraining, especially in the case of prototype development. Indeed, such making requires skills, specific appliances as well as human time for setting up the machine tools and the fabrication process. With the emergence [...] Read more.

Conceiving planar magnetic components for power electronic converters is very constraining, especially in the case of prototype development. Indeed, such making requires skills, specific appliances as well as human time for setting up the machine tools and the fabrication process. With the emergence of Fabrication Laboratory (FabLab), conceiving of planar copper foil prototypes becomes more feasible in a shortened time process for engineers and researchers. This paper presents a methodology and process for conceiving power planar transformers with the help of machines and tools that can be found in the usual FabLab. Full article

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39 pages, 52160 KiB

Open AccessArticle

Development of Planning and Operation Guidelines for Strategic Grid Planning of Urban Low-Voltage Grids with a New Supply Task

by Patrick Wintzek, Shawki Alsayed Ali, Markus Zdrallek, Julian Monscheidt, Ben Gemsjäger and Adam Slupinski

Electricity 2021, 2(4), 614-652; https://doi.org/10.3390/electricity2040035 - 16 Dec 2021

Cited by 11 | Viewed by 4484

Abstract

In contrast to rural distribution grids, which are mostly “feed-in oriented” in terms of electrical power, urban distribution grids are “load oriented”, as the number of customer connections and density of loads in urban areas is significantly higher than in rural areas. Taking [...] Read more.

In contrast to rural distribution grids, which are mostly “feed-in oriented” in terms of electrical power, urban distribution grids are “load oriented”, as the number of customer connections and density of loads in urban areas is significantly higher than in rural areas. Taking into account the progressive electrification of the transport and heating sector, it is necessary to assess the required grid optimization or expansion measures from a conventional, as well as an innovative point of view. This is necessary in order to be able to contain the enormous investment volumes needed for transforming the energy system and aligning the infrastructures to their future requirements in time. Therefore, this article first explains the methodological approach of allocating scenarios of the development of electric mobility and heat pumps to analyzed grids. The article continues with describing which power values need to be applied and which conventional and innovative planning measures are available for avoiding voltage band violations and equipment overloads within the framework of strategic grid planning. Subsequently, the results of grid planning studies are outlined and evaluated with an assessment model that evaluates capital as well as operational costs. On this basis, planning and operation guidelines for urban low-voltage grids are derived. The main result is that low-voltage grids can accommodate charging infrastructure for electric mobility, as well as heat pumps to a certain degree. In addition, it is concluded that conventional planning measures are not completely avoidable, but can be partially avoided or deferred through dynamic load management. Full article

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16 pages, 3927 KiB

Open AccessArticle

Adapted Stochastic PV Hosting Capacity Approach for Electric Vehicle Charging Considering Undervoltage

by Enock Mulenga, Math H. J. Bollen and Nicholas Etherden

Electricity 2021, 2(3), 387-402; https://doi.org/10.3390/electricity2030023 - 17 Sep 2021

Cited by 17 | Viewed by 3057

Abstract

This paper presents a stochastic approach to single-phase and three-phase EV charge hosting capacity for distribution networks. The method includes the two types of uncertainties, aleatory and epistemic, and is developed from an equivalent method that was applied to solar PV hosting capacity [...] Read more.

This paper presents a stochastic approach to single-phase and three-phase EV charge hosting capacity for distribution networks. The method includes the two types of uncertainties, aleatory and epistemic, and is developed from an equivalent method that was applied to solar PV hosting capacity estimation. The method is applied to two existing low-voltage networks in Northern Sweden, with six and 83 customers. The lowest background voltage and highest consumption per customer are obtained from measurements. It is shown that both have a big impact on the hosting capacity. The hosting capacity also depends strongly on the charging size, within the range of charging size expected in the near future. The large range in hosting capacity found from this study—between 0% and 100% of customers can simultaneously charge their EV car—means that such hosting capacity studies are needed for each individual distribution network. The highest hosting capacity for the illustrative distribution networks was obtained for the 3.7 kW single-phase and 11 kW three-phase EV charging power. Full article

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15 pages, 20223 KiB

Open AccessArticle

Assessment of the Visual Impact of Existing High-Voltage Lines in Urban Areas

by Andreas Sumper, Oriol Boix-Aragones, Joan Rull-Duran, Joan Amat-Algaba and Joachim Wagner

Electricity 2021, 2(3), 285-299; https://doi.org/10.3390/electricity2030017 - 29 Jul 2021

Cited by 4 | Viewed by 4240

Abstract

This article proposes a novel methodology to evaluate the visual impact of high-voltage lines in urban areas based on photographic images. The use of photographs allows for calculating the overall aesthetic impact while eliminating the subjective factors of the observer. To apply the [...] Read more.

This article proposes a novel methodology to evaluate the visual impact of high-voltage lines in urban areas based on photographic images. The use of photographs allows for calculating the overall aesthetic impact while eliminating the subjective factors of the observer. To apply the proposed methodology based on photographs, the impact of the position and angle where the photograph was taken was analyzed, and a sensibility analysis was carried out. Moreover, it was applied to an application case, and a comparison with results from a previous study of a visual impact was performed. The methodology shows good performance and a better resolution of the indicator. Full article

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27 pages, 9242 KiB

Open AccessReview

Comparison of DSOGI-Based PLL for Phase Estimation in Three-Phase Weak Grids

by Jorge Pinto, Adriano Carvalho, Agostinho Rocha and Armando Araújo

Electricity 2021, 2(3), 244-270; https://doi.org/10.3390/electricity2030015 - 8 Jul 2021

Cited by 13 | Viewed by 5757

Abstract

The paper presents a summary of different double second-order generalized integrator (DSOGI)-based phase-locked loop (PLL) algorithms for synchronization with three-phase weak grids. The different methods are compared through simulation under a variety of grid conditions, such as unbalanced phase voltages, high low-order harmonics [...] Read more.

The paper presents a summary of different double second-order generalized integrator (DSOGI)-based phase-locked loop (PLL) algorithms for synchronization with three-phase weak grids. The different methods are compared through simulation under a variety of grid conditions, such as unbalanced phase voltages, high low-order harmonics distortion, frequency steps, phase jumps, and voltage sags. Following the simulation results, the three methods that have shown the overall best results are compared through an experimental setup for further results validation under operation with a voltage-source converter. Based on the obtained results, a benchmark table is presented that allows ranking the performance of the tested methods for different expected grid conditions. Full article

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