Transient Power Angle Instability Mechanism and Stability Margin Analysis of Synchronous Condenser Co-Located with Renewable Energy Base Based on Equivalent Synchronous Generator
Shan Yongpeng1, Liu Xinyu2, Wang Ying3, Zheng Di4, Xin Huanhai1,2,5
1. Polytechnic Institute Zhejiang University Hangzhou 310015 China; 2. College of Electrical Engineering Zhejiang University Hangzhou 310027 China; 3. Northwest Branch of State Grid Cooperation of China Xi'an 710048 China; 4. College of Mechanical and Electrical Engineering China Jiliang University Hangzhou 310018 China; 5. Zhejiang Key Laboratory of Renewable Energy Electrical Technology and System Hangzhou 310027 China
Abstract：Configuring synchronous condensers (SCs) in large renewable energy base is an effective technical solution to improve the carrying capacity of renewable energy. However, there is a risk of transient power angle instability of the SC in this scheme. Existing literatures have analyzed the transient instability of the SC under specific operating conditions, but they have not comprehensively considered the influence of system parameters on the power angle characteristics of the SC, resulting in a lack of systematic understanding of the transient instability mechanism of the SC under different instability forms. In order to solve the above problems, this paper intends to summarize and analyze the transient instability mechanism behind the different instability forms of the SC based on the equivalent synchronous generator model, quantify the change boundary of the instability forms of the SC and the transient stability margin of the system under the different instability forms by drawing on the analysis methods of transient stability of the traditional synchronous generator. Firstly, the power angle characteristics of the SC are analyzed based on the equivalent model of the associated system of a renewable energy base co-located with a SC and the Thévenin equivalent method. Subsequently, the active power transfer relationship between the equipment and the grid is analyzed, and the equivalent synchronous generator modeling method is provided. Secondly, the energy function of the associated system is developed based on the equivalent synchronous generator model and the energy function of the traditional synchronous generator. The energy conversion process of the system during the transient period is analyzed, and at the same time, the transient instability forms and mechanisms of the SC are summarized and revealed. Thirdly, based on the unbalanced power borne by the rotor during the fault period, the boundary conditions leading to changes in the instability forms of the SC are quantified. The transient stability margin of the system under different instability forms are derived based on the energy function and the critical clearance time (CCT), and the influence of the system parameters on the instability forms and transient stability margin of the SC is analyzed. Finally, the correctness of the proposed instability mechanisms and the analysis of the influencing factors are verified through electromagnetic transient simulations. The following conclusions can be drawn: (1) Under different operating conditions, there are two types of instability forms of the SC: first-swing accelerated instability and first-swing decelerated and second-swing accelerated instability. The former is similar to the transient instability process of the traditional synchronous generator. The latter accumulates potential energy in the first swing stage and converts the potential energy into kinetic energy in the second swing stage. (2) The transient stability boundaries of the SC under the two types of instability forms are different. In the first-swing instability form, there is one CCT, and the system is unstable when the fault clearance time is larger than the CCT. In the second-swing instability form, there are two CCTs, and the system is unstable when the fault clearance time is in the middle of the two CCTs. (3) Since reducing the unbalanced power borne by the SC during the fault helps improve the transient stability of the system, renewable energy should adjust its power output by reducing active power and increasing reactive power under the first-swing instability form, while increasing active power and reducing reactive power under the second-swing instability form. In addition, increasing the capacity proportion of the SC or improving system strength will help improve the transient stability of the SC.
单永鹏, 刘昕宇, 汪莹, 郑迪, 辛焕海. 基于等效同步机的新能源基地同步调相机暂态功角失稳机理和稳定裕度分析[J]. 电工技术学报, 2025, 40(17): 5448-5463.
Shan Yongpeng, Liu Xinyu, Wang Ying, Zheng Di, Xin Huanhai. Transient Power Angle Instability Mechanism and Stability Margin Analysis of Synchronous Condenser Co-Located with Renewable Energy Base Based on Equivalent Synchronous Generator. Transactions of China Electrotechnical Society, 2025, 40(17): 5448-5463.
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