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Analysis Method of Piecewise Linear Model for Frequency Oscillation in Asynchronous Power Grid of Yunnan in China

1.Power Dispatching and Control Center of China Southern Power Grid, Guangzhou 510623, China;2.School of Electrical Engineering, Xi’an Jiaotong University, Xi’an 710049, China

Fund Project:

This work is supported by China Southern Power Grid Company Limited (No. ZDKJXM20160001).

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    Some frequency oscillations occurred near the governor dead band in the test of asynchronous interconnection in Yunnan in China. To analyze this issue, a piecewise linear system model considering governor dead band is established. The effect of governor dead band on frequency stability is clarified through steady-state and dynamic behavior analysis. Research results show that the system may have no equilibrium point with step-response dead band and it will cause frequency oscillations near the dead band. Meanwhile, the stability of piecewise linear system is determined by the eigenvalue of the linear system corresponding to each frequency range, and the negative damping effect can also cause system frequency instability. Different frequency oscillations in the test are simulated by both the simplified system model and the actual model of Yunnan power grid.

    表 2 交流负载和相应的频率Table 2 AC loads and corresponding frequencies
    图1 不同发电厂的频率Fig.1 Frequencies of different power plants
    图2 典型PID型调速系统框图Fig.2 Block diagram of a typical PID governor system
    图3 分段线性控制示意图Fig.3 Schematic diagram of piecewise linear control
    图4 有增强型调速器时的系统稳态频率响应Fig.4 Steady-state frequency response of system with step-response governor
    图5 有无平衡点时频率响应的仿真结果Fig.5 Simulation results of frequency response with or without equilibrium point
    图6 系统阻尼特性改变时的频率振荡波形Fig.6 Frequency oscillation waveform when system damping changes
    图 增强型调速器导致频率在死区附近往复振荡Fig. Frequency oscillation caused by dead band of step response
    图 阻尼不足导致振荡发散Fig. Oscillation divergence caused by Insufficient damping
    表 1 测试系统的相关参数Table 1 Relevant parameters of testing system
    图 普通型调速器和增强型调速器的死区Fig. Dead band of no-step response and step response
    图 一个简化的测试系统Fig. A simplified testing system
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CHEN Yiping,LI Chongtao,YANG Ruopu,et al.Analysis Method of Piecewise Linear Model for Frequency Oscillation in Asynchronous Power Grid of Yunnan in China[J].Automation of Electric Power Systems,2020,44(6):186-193.DOI:10.7500/AEPS20190729004

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  • Received:July 29,2019
  • Revised:November 01,2019
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  • Online: March 21,2020
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