Symmetry/Asymmetry Studies in Modern Power Systems

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Engineering and Materials".

Deadline for manuscript submissions: 31 December 2024 | Viewed by 4824

Special Issue Editors

Associate Professor, School of Automation, Nanjing University of Science and Technology, Nanjing 210094, China
Interests: high-power power electronic conversion systems; new energy generation and grid integration; distributed control of AC/DC microgrids; the application of artificial intelligence in power electronic conversion

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Guest Editor
Researcher, School of Electrical Engineering, Southeast University, Nanjing 210096, China
Interests: power system planning, operation and control; application of artificial intelligence in power system; intelligent dispatching and intelligent operation and maintenance of power grid; electric vehicles and energy Internet intelligent interaction

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Guest Editor
Associate Professor, Department of Electrical Engineering, Tsinghua University, Beijing 100084, China
Interests: power system stability; dynamic analysis; control of power systems
Assistant Professor, School of Automation, Nanjing University of Science and Technology, Nanjing 210094, China
Interests: power system operation and control; the application of artificial intelligence in power systems; small disturbance stability; frequency stability of new power systems; new energy grid-connected control; flexible DC transmission

Special Issue Information

Dear Colleagues,

Symmetry and asymmetry concepts play a fundamental role in the design, operation, and stability of modern power systems. This Special Issue provides a platform for in-depth exploration of the relationship between symmetry and power systems, aiming to enhance our understanding of the impact of symmetry on system performance, reliability, and efficiency. This Special Issue will delve into various aspects of symmetry in power systems, including its application in fault diagnosis, system planning, and design. It will also highlight the role of symmetry in improving operational efficiency, enhancing system stability, and ensuring the reliable delivery of electricity. By exploring the intricate connections between symmetry and power systems, this Special Issue aims to foster a deeper understanding of the complexities involved and to provide valuable insights to improve power system design and operations.

This Special Issue invites researchers to contribute original research articles and reviews that explore various aspects related to symmetry and asymmetry in modern power systems. Applied case studies are especially welcome. Topics of interest for this Special Issue include, but are not limited to, the following:

  • Basic theory and practice of symmetry and asymmetry in power systems;
  • Fault diagnosis and prevention of symmetry and asymmetry in power systems;
  • Optimization, design, and planning of symmetry and asymmetry in power systems;
  • Energy efficiency management of symmetry and asymmetry in power systems;
  • Symmetry/asymmetry of power flow and transmission;
  • Symmetry/asymmetry of power system topology;
  • Symmetry/asymmetry in multiphase power systems;
  • Active symmetry and balance of power systems;
  • Reactive symmetry and balance of power systems;
  • Symmetry/asymmetry in power electronics devices and renewable energy components;
  • Algorithms for studying symmetry in power systems;
  • Influence of symmetry on power system operation, renewable energy integration, and smart grid technologies;
  • Symmetry/asymmetry of power system transients and influence on system stability;
  • Symmetry/asymmetry of power electronic-based power systems;
  • Grid-forming/grid-following control of multiple converters with asymmetries.

Dr. Cheng Wang
Dr. Zhong Chen
Dr. Lei Chen
Dr. Tao Zhou
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Symmetry is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • power systems
  • power electronics
  • symmetrical faults
  • asymmetrical faults
  • power system stability
  • balanced conditions
  • grid-forming converters

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Published Papers (4 papers)

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Research

25 pages, 8256 KiB  
Article
Small-Signal Modeling and Frequency Support Capacity Analysis of Power Load Considering Voltage Variation Effect
by Tao Zhou, Yuxin Zheng, Cheng Wang, Lei Chen, Bo Liu and Zhong Chen
Symmetry 2024, 16(7), 918; https://doi.org/10.3390/sym16070918 - 18 Jul 2024
Viewed by 802
Abstract
The frequency support capacity of power loads is essential for maintaining active power symmetry and balance between the generation and demand sides of power systems. As the proportion of renewable energy sources and power electronic equipment increases, the inertia on the power generation [...] Read more.
The frequency support capacity of power loads is essential for maintaining active power symmetry and balance between the generation and demand sides of power systems. As the proportion of renewable energy sources and power electronic equipment increases, the inertia on the power generation side decreases, highlighting the growing importance of frequency support on the load side. As it is generally believed that the active power balance of power systems determines the frequency stability, few studies have considered the effect of voltage variation on the frequency response dynamics. It is important to note that the node voltage keeps fluctuating throughout the frequency dynamic process, which affects the active power of loads and should not be neglected. Based on the aforementioned rationales, this paper endeavors to investigate the modeling of power load frequency response and analyze its support capability considering the voltage variation effect. This paper initially establishes the small-signal model of dynamic load under frequency dynamics, derives the transfer function relating active power to system frequency deviation, and subsequently develops its frequency response model. Subsequently, commencing with the ZIP model of static load, the power fluctuation of load nodes is derived from the influence of preceding nodes, and the frequency response model of the static load is formulated and its frequency support capacity is scrutinized. Based on this foundation, a comprehensive aggregation model of the complex load is constructed, and its frequency support capability is assessed using actual data. Finally, the proposed model and analysis results are validated through simulation, confirming their correctness and effectiveness. Full article
(This article belongs to the Special Issue Symmetry/Asymmetry Studies in Modern Power Systems)
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25 pages, 4811 KiB  
Article
Power Transformer On-Load Capacity-Regulating Control and Optimization Based on Load Forecasting and Hesitant Fuzzy Control
by Dexu Zou, Xinyu Sun, Hao Quan, Jianhua Yin, Qingjun Peng, Shan Wang, Weiju Dai and Zhihu Hong
Symmetry 2024, 16(6), 679; https://doi.org/10.3390/sym16060679 - 1 Jun 2024
Viewed by 380
Abstract
The operational stability of a power transformer exerts an extremely important impact on the power symmetry, balance, and security of power systems. When the grid load fluctuates greatly, if the load factor of the transformer cannot be maintained within a reasonable range, it [...] Read more.
The operational stability of a power transformer exerts an extremely important impact on the power symmetry, balance, and security of power systems. When the grid load fluctuates greatly, if the load factor of the transformer cannot be maintained within a reasonable range, it leads to increased instability in grid operation. Adjusting the transformer capacity based on load changes is of great significance. The existing control methods for on-load capacity-regulating (OLCR) transformers have low timeliness, and the daily switching frequency of the capacity-regulating switch is not controlled. To ensure the safe and stable operation of transformers, this paper proposes a control method for OLCR transformers based on load prediction and fuzzy control. Firstly, the operating principle of OLCR transformers is analyzed, and a multi-strategy enhanced dung beetle optimizer (MSDBO) combined with a CNN−LSTM model is proposed for load forecasting. On this basis, the daily switching frequency of the capacity-regulating transformer is introduced, and hesitant fuzzy control is used to select the optimal capacity-regulating strategy relying on three factors: loss, economy, and switching frequency. Finally, simulation models are constructed using the MATLAB/SIMULINK platform and simulation analysis is conducted to verify the effectiveness and superiority of the proposed control method. For the three scenarios in this paper, the method reduces daily power loss by 28.5% to 56.3% and daily operating costs by 25.4% to 50.8%. The method used in this paper can sacrifice 3.5% to 9.2% of the loss reduction capability in exchange for reducing the number of switch operations by 28.6% to 57.1%, significantly extending the lifespan of the switches and thereby increasing the operational lifespan of the transformer. Full article
(This article belongs to the Special Issue Symmetry/Asymmetry Studies in Modern Power Systems)
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19 pages, 3140 KiB  
Article
A Coordinated Control Strategy of Multi-Type Flexible Resources and Under-Frequency Load Shedding for Active Power Balance
by Jian Zhang, Jiaying Wang, Yongji Cao, Baoliang Li and Changgang Li
Symmetry 2024, 16(4), 479; https://doi.org/10.3390/sym16040479 - 15 Apr 2024
Cited by 2 | Viewed by 1048
Abstract
With the increasing expansion of power systems, there is a growing trend towards active distribution networks for decentralized power generation and energy management. However, the instability of distributed renewable energy introduces complexity to power system operation. The active symmetry and balance of power [...] Read more.
With the increasing expansion of power systems, there is a growing trend towards active distribution networks for decentralized power generation and energy management. However, the instability of distributed renewable energy introduces complexity to power system operation. The active symmetry and balance of power systems are becoming increasingly important. This paper focuses on the characteristics of distributed resources and under-frequency load shedding, and a coordinated operation and control strategy based on the rapid adjustment of energy storage power is proposed. The characteristics of various controllable resources are analyzed to explore the rapid response capabilities of energy storage. The energy storage types are categorized based on the support time, and the final decision is achieved with power allocation and adjustment control of the energy storage system. Additionally, a comprehensive control strategy for under-frequency load shedding and hierarchical systems is provided for scenarios with insufficient active support. The feasibility of the proposed model and methods is verified via a multi-energy system case. Full article
(This article belongs to the Special Issue Symmetry/Asymmetry Studies in Modern Power Systems)
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15 pages, 1124 KiB  
Article
Deep Reinforcement Learning for Load Frequency Control in Isolated Microgrids: A Knowledge Aggregation Approach with Emphasis on Power Symmetry and Balance
by Min Wu, Dakui Ma, Kaiqing Xiong and Linkun Yuan
Symmetry 2024, 16(3), 322; https://doi.org/10.3390/sym16030322 - 7 Mar 2024
Cited by 2 | Viewed by 1259
Abstract
To address the issues of instability and inefficiency that the fluctuating and uncertain characteristics of renewable energy sources impose on low-carbon microgrids, this research introduces a novel Knowledge-Data-Driven Load Frequency Control (KDD-LFC) approach. This advanced strategy seamlessly combines pre-existing knowledge frameworks with the [...] Read more.
To address the issues of instability and inefficiency that the fluctuating and uncertain characteristics of renewable energy sources impose on low-carbon microgrids, this research introduces a novel Knowledge-Data-Driven Load Frequency Control (KDD-LFC) approach. This advanced strategy seamlessly combines pre-existing knowledge frameworks with the capabilities of deep learning neural networks, enabling the adaptive management and multi-faceted optimization of microgrid functionalities, with a keen emphasis on the symmetry and equilibrium of active power. Initially, the process involves the cultivation of foundational knowledge through established methodologies to augment the reservoir of experience. Following this, a Knowledge-Aggregation-based Proximal Policy Optimization (KA-PPO) technique is employed, which proficiently acquires an understanding of the microgrid’s state representations and operational tactics. This strategy meticulously navigates the delicate balance between the exploration of new strategies and the exploitation of known efficacies, ensuring the harmonization of frequency stability, precision in tracking, and the optimization of control expenditures through the strategic formulation of the reward function. The empirical validation of the KDD-LFC method’s effectiveness and its superiority are demonstrated via simulation tests conducted on the load frequency control (LFC) framework of the Sansha isolated island microgrid, which is under the administration of the China Southern Grid. Full article
(This article belongs to the Special Issue Symmetry/Asymmetry Studies in Modern Power Systems)
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