连接弱交流电网的柔性直流换流站外环控制器参数解析计算及其限制因素分析

Analytical Calculation Method of Outer Loop Controller Parameters ofHVDC Converter Station Connected to Weak AC Grid and Analysis of Limiting Factors

柔直换流站连接弱交流电网的交流电压动态响应速度与交流电压控制器参数、短路比、稳态点和公共耦合接入点并联等效电容有关。针对柔直换流站连接弱交流电网外环控制器参数解析计算及其限制因素分析研究欠缺问题,该文在建立整个系统详细模型的基础之上,根据外环闭环传递函数零极点分布情况,分析影响系统动态响应速度和稳定性相关特征根的关键变量及其参与程度。其次,基于交流系统准稳态模型,推导外环控制器参数解析计算表达式,并对其选择范围进行了初步分析。再次,研究外环控制器参数、电流内环带宽、锁相环参数以及短路比对稳定性的影响,结果表明,外环带宽与锁相环带宽接近并不一定是诱导系统发生谐振失稳的因素,降低交流电压控制器和锁相环参数有利于提升柔直换流站运行于逆变状态下的稳定性。最后,通过电磁暂态仿真验证了参数计算与稳定性分析的正确性。

The dynamic response speed of AC voltage of flexible high voltage direct current(HVDC)converter connected to weak AC grid is manly related to the parameters of AC voltage controller,SCR,steady state operating points and equivalent capacitance paralleled at point of common coupling(PCC).Firstly,due to the lack of analytical calculation of the parameters of AC voltage controller and analysis of their limiting factors,the key influence variables and participations of eigenvalues related to dynamic response and stability have been analyzed according to the distribution of zeros and poles based on the detailed analytical model of whole system.Secondly,based on the quasi steady state model of AC system,the analytical calculation expressions of outer loop controller parameters are derived,and their selection ranges are preliminarily analyzed.Thirdly,the effects of outer loop controller parameters,bandwidth of current inner loop,PLL parameters and SCR on stability are studied.The results show that bandwidth of PLL closed to that of AC voltage loop may not be the factor inducing resonance of system.Reducing the parameters of AC voltage controller and PLL can improve the stability of converter station running in inverter mode.Finally,the correctness of parameter calculation and stability analysis is verified by electromagnetic transient simulations.