基于频率耦合阻抗的直驱风电机组次同步振荡关键影响因素分析及抑制措施  

Analysis of Key Factors and Suppression Measures for Sub-synchronous Oscillation of Direct-drive PMSG Based on Frequency Coupled Impedance

作　　者：肖仕武[1] 徐立光 XIAO Shiwu;XU Liguang(School of Electrical and Electronics Engineering,North China Electrical Power University,Changping District,Beijing 102206,China;Chengxi Power Supply Branch of State Grid Tianjin Electric Power Company,Nankai District,Tianjin 300110,China)

机构地区：[1]华北电力大学电气与电子工程学院,北京市昌平区102206 [2]国网天津市电力公司城西供电分公司,天津市南开区300110

出　　处：《电网技术》2023年第4期1641-1652,共12页Power System Technology

基　　金：国家自然科学基金重点项目(52130709)。

摘　　要：直驱风电机组与弱交流电网的动态交互导致次同步振荡现象时有发生,计及频率耦合效应的阻抗分析法是研究该现象的有效方法之一。首先,建立了计及锁相环、直流电容电压及LC滤波器动态的频率耦合序阻抗模型,并结合阻抗扫频验证了模型的正确性;其次,基于修正的序阻抗伯德图判据对并网系统进行稳定判别得出风险频段的负电阻是导致系统失稳的主要原因;进一步,鉴于电压环、锁相环主要影响次/超频带的阻抗特性,采用灵敏度分析法从带宽和阻尼比角度量化了电压环、锁相环参数对风机阻抗的影响,得出初始参数下的电压环阻尼比是造成阻抗在风险频段呈现负电阻的关键原因;最后,设计了串联超前相位校正的改进控制方案,方案可通过阻抗重塑削弱风险频段的负电阻特性,进而使得并网系统的稳定性提升。结合时域仿真验证了灵敏度分析的正确性和改进控制方案对振荡抑制的有效性。Sub-synchronous oscillations(SSO)always occur when the direct-drive permanent magnet synchronous generator(PMSG)is connected to the weak grid.The impedance modeling method considering the frequency coupling effect is an effective approach to study this phenomenon.Firstly,considering the dynamics of the phase-locked loop,the DC capacitor voltage and the LC-filter,the frequency-coupled impedance model of the PSMG is established,and its correctness is verified by frequency scanning.Secondly,combined with a modified sequence impedance Bode diagram criterion,the stability of the grid-connected system is discriminated,and the negative resistance of impedance in the risky frequency band is found to be the main cause of the system instability.Further,given that the voltage loop and the phase-locked loop mainly affect the impedance in sub/super-synchronous band,the influence of the bandwidth and the damping ratio of the voltage loop and the phase-locked loop on the impedance is quantified by using the sensitivity analysis.It is found that the damping ratio of the voltage loop at the initial parameters is the key reason for the negative resistance of the impedance.Finally,an improved control scheme for a series overrun phase correction link is designed.The control scheme can weaken the negative resistance of impedance in the risky frequency band by impedance reshaping,improving the stability of grid-connected system.Time domain simulation verifies the correctness of the sensitivity analysis and the effectiveness of the improved control scheme in suppressing the SSO.

关 键 词：次同步振荡 频率耦合 负电阻 改进控制方案 

分 类 号：TM614[电气工程—电力系统及自动化]