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[editor's recommendation] "new technology of reactive power compensation and control for UHV AC-DC hybrid power grid"

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Special editor
Brief introduction of editor in chief
Wei Zhinong, male, 1962, professor and doctoral supervisor of Hehai University, now director of the Institute of integrated energy system planning and operation. Presided over more than 60 projects, including 1 key project of NSFC, 3 general projects and major special projects of State Grid Corporation of China. He has won 1 National Science and Technology Progress Award and 5 provincial and ministerial science and technology progress awards. He has published more than 200 EI retrieval papers, more than 70 SCI retrieval papers (19 IEEE Transactions Series), and more than 60 national invention patents.
//Special editor's note on "new technology of reactive power compensation control for UHV AC-DC hybrid power grid"//
In recent years, with the gradual increase of new energy penetration, the intermittence and fluctuation of power supply bring difficulties to the reactive power control of power grid. At the same time, in order to realize cross regional power grid mutual supply and promote clean energy consumption, China has carried out the construction of large-scale AC-DC hybrid power grid. If the reactive power level at the sending end is insufficient, a large-scale new energy off grid accident may occur under large disturbance; if the structure of the receiving end grid is weak and the reactive power support capacity is insufficient, UHVDC may fail to change phase or even lock up due to AC fault, resulting in grid collapse and other serious consequences. In order to improve the fault tolerance ability of large-scale AC / DC hybrid power grid and ensure the safe and stable operation of power grid, various new reactive power compensation and control technologies have been widely concerned, and become the research hotspot of academia and industry.
In order to show the latest research results of the academic and engineering circles in reactive power compensation control theory and advanced equipment technology, the editorial department of power engineering technology has set up the special topic of "new technology of reactive power compensation control for UHV AC-DC hybrid power grid", and I am honored to be invited as the special editor. A large number of contributions from universities, scientific research institutions, equipment manufacturers and the first line of power production have been received. After peer review and expert selection, six papers have been selected to form a special topic, covering the following aspects: new synchronous condenser, Southeast University Professor Cheng Ming elaborated the principle of the new synchronous condenser, and analyzed the key influencing factors of its reactive power control ability Jiang Mengyao of Hehai University and others improved the traditional phase angle difference time function to solve the problem of low success rate of large-scale synchronous camera grid connection, which provides a basis for the operation of the new synchronous camera. In terms of other dynamic reactive power compensation devices, LV Guangqiang of Nanjing University of science and technology improved the traditional SVG control strategy. Based on the internal loop decoupling control, the fuzzy control was introduced to adjust the PI parameters adaptively, which improved the compensation accuracy of SVG. Qiu Guanxin of Guangdong Power Grid Co., Ltd. proposed the MMC based STATCOM topology and designed the relevant control strategy, which realized Voltage compensation under unbalanced load. In the aspect of optimal control of traditional reactive power compensation equipment, fan Shixiong et al. Of China Electric Power Research Institute proposed a method of reactive power and voltage regulation based on agent group reinforcement learning, which included capacitor switching into the description of grid operation state, and optimized the action behavior of capacitor under extreme operation conditions by introducing state improvement incentive mechanism. In the aspect of reactive power support of new energy power station, Wang Qiang, etc. of State Grid Hebei company, etc. put forward the evaluation method and index system of reactive power support capacity based on dynamic time bending algorithm, elaborated the photovoltaic output prediction method and index system based on the depth confidence network model, and realized the prediction of reactive power support capacity of power grid in the future.
The purpose of this topic is to show the latest achievements and progress in the field of reactive power compensation control of UHV AC-DC hybrid power grid. Due to the limitation of the number of special papers and the arrangement of publication time, many high-level papers are not included in this topic, hoping to be understood by all authors and readers.
I sincerely thank the experts and scholars for their great support for this topic, and the editorial department of power engineering technology for their extensive and meticulous work in planning, organizing and publishing this topic. Finally, I sincerely hope that this topic can provide experts and scholars in related fields with an AC flow platform and provide useful reference for the safe and stable operation and control of UHV AC-DC hybrid power grid Test.
An overview of the paper
Paper: key technologies and research progress of new synchronous condenser
Author: Cheng Ming1, Tian Weijie 1, Wang Wei1, Wei Chao 2
Setting: 1. Southeast University
2. Electric Power Research Institute of State Grid Jiangsu Electric Power Co., Ltd
Abstract: with the development of HVDC transmission system, large capacity new synchronous condenser becomes the best choice to meet the dynamic demand of reactive power, and becomes one of the research focuses. Based on this, this paper systematically summarizes and summarizes the research status of the new synchronous condenser. Firstly, the paper introduces the operation principle of the new synchronous condenser from three aspects: mathematical model, operation state and control strategy. Secondly, compared with the power electronic reactive power compensation equipment, this paper expounds the superior dynamic reactive power output characteristics of the new synchronous condenser, and studies the influencing factors of its reactive power output characteristics. Finally, the research status of the state monitoring technology of the new synchronous condenser is summarized from two aspects: the existing fault diagnosis technology and parameter identification technology. In this paper, the mathematical model, control strategy and operation state monitoring of the new synchronous condenser are summarized, which can provide reference for the further research of the new synchronous condenser.
Paper: reactive power and voltage regulation method based on agent group reinforcement learning
Authors: Fan Shixiong 1, Liu Xingwei 1, Wei Zhizhi 2, Liu Ruiye 2, Wang Songyan 2, Yu Jilai 2
Unit: 1. China Electric Power Research Institute Co., Ltd
2. Department of electrical engineering, Harbin University of Technology
Abstract: reactive voltage regulation is an important measure to ensure the regional voltage stability of power grid. There are many problems in the current single agent design based on reinforcement learning, such as unreasonable architecture design. In this paper, a method of describing the comprehensive operation state of Power Grid Considering the voltage amplitude of node and the switching state of capacitor is proposed, and a group architecture of reinforcement learning agent for reactive power and voltage regulation of power grid is designed. The Group determines the agent members according to the current comprehensive operation state of the power grid, and gives corresponding reactive power regulation actions. Each agent member takes the improvement degree of the power grid state in the adjacent period as the reward mechanism. The example shows that this method can be applied to the reactive voltage control environment of power grid. Compared with the single agent design method, it can effectively reduce the number of action sets, and can better cope with various reactive voltage control conditions.
Paper: Based on the time function of phase angle difference, the prediction of the closing time of the grid connected condenser
Authors: Jiang Mengyao 1, Tang Xiaozheng 2, Liu Yidan 2, Zhao Hongfei 2, Ma Hongzhong 1, Chen Ming 1
Setting: 1. School of energy and electricity, Hehai University
2. State Grid Jiangsu Electric Power Co., Ltd. maintenance branch
Abstract: in view of the problems of poor connection conditions and low success rate of large-scale synchronous condenser, the traditional phase angle difference time function is improved. The improved curve can reflect the change rule of phase angle difference between 0 and 2 π, and intuitively show whether there are synchronization points and their number in a certain range of slip speed and the corresponding closing time range in a certain range of phase angle difference It is convenient to predict the time when the closing pulse is sent. The number of synchronization points within the maximum allowable slip range and the allowable closing time range of the condenser are analyzed by an example when the inert deceleration starting time is 0 and the acceleration is - 0.167r/s2. The correctness of the analysis result is verified by Matlab / Simulink simulation software. At the same time, taking the impact current of the condenser as the setting basis of the maximum allowable phase angle difference effectively reduces the impact on the condenser during grid connection, and improves the success rate of grid connection.
Paper: an improved fuzzy adaptive PI control strategy for static var generator
Author: LV Guangqiang, Liu Xiaoyi
Setting: Nanjing University of Technology
Absrtact: in view of the problem that the traditional control strategy of static var generator (SVG) has insufficient self-adaptive regulation ability, the traditional control strategy is improved. On the basis of internal loop decoupling control, fuzzy control is introduced to adjust PI parameters adaptively to improve the compensation accuracy of static var generator. And the traditional fuzzy PI control takes the PI initial parameter as the center to adjust up and down, and the adjustment range is limited. To solve this problem, the paper proposes to adjust the PI parameter in the way of accumulation to increase the adjustment range. The simulation results show that, compared with the existing control strategy, the compensation accuracy is further improved and the anti disturbance of the system is enhanced.
Paper: assessment of reactive power support capacity of photovoltaic power station considering output fluctuation
Authors: Wang Qiang 1, Gu qiaogen 2, sun Zhongmin 2, Geng Shaobo 1, Ren Jiangbo 1
Unit: 1. State Grid Hebei Electric Power Co., Ltd
2. Nanjing Nanrui Jibao Power Co., Ltd
Abstract: on the premise of satisfying the stable operation of the distribution network, giving full play to the rated capacity of the grid connected inverter of the photovoltaic power station and excavating the reactive power support capacity of the photovoltaic power station can promote the economic operation of the distribution network, so it has a strong practical significance to carry out the assessment of the reactive power support capacity of the photovoltaic power station. First of all, the assessment method and index system of reactive power support capacity based on dynamic time bending algorithm are proposed, and the assessment of real-time reactive power support capacity is also proposed; then, the photovoltaic output prediction method and index system based on the depth confidence network model are proposed, and the prediction of future reactive power support capacity is realized by combining the prediction data. The example shows that the predicted reactive power support capacity of photovoltaic power station in the future state is consistent with the actual assessment results in the future state, which verifies the effectiveness of the proposed assessment and prediction method.
Thesis: Research on mmc-statcom compensation strategy under unbalanced load
Authors: Qiu Guanxin 1, Zhu Pengyu 2, Wang can2, Yang Ruixiong 1, Ling Huabao 1, Lin Guihui 1
Unit: 1. Zhuhai Power Supply Bureau of Guangdong Power Grid Company
2. Shenzhen Institute of mechanical and electrical engineering and automation, Harbin University of Technology
Abstract: This paper introduces the principle of reactive power compensation and voltage compensation of static synchronous compensator (STATCOM) in power grid. Aiming at the difficulty of traditional STATCOM topology level number promotion, modular multilevel converter is adopted, MMC) topology compensates the voltage under unbalanced load. In view of the poor control effect of the traditional control strategy under the condition of load imbalance, this paper analyzes the reactive compensator under the positive and negative sequence model, and proposes the sequence control strategy that divides the voltage and current into positive sequence and negative sequence respectively, uses the phase-locked loop technology of decoupling double synchronous reference frame to lock the voltage at the common connection point, and at the same time, the MMC submodule is analyzed Finally, a five-level static var compensator is built in the electromagnetic transient simulation software PSCAD / EMTDC. The effectiveness of the sequence control strategy and the sub module capacitor voltage distributed control strategy is verified by simulation.
Journal of power engineering technology
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