次同步扰动下并网电压源换流器电气量的频率分布及其幅值特性

针对并网电压源换流器在次同步电压扰动下输出多频率分量的现象,采用动态响应分析法和二阶近似,推导并分析了相应的输出电气量近似解的频率分布特性及其幅值大小。具体地,在次同步电压扰动下,保留二阶扰动量,逐步分析推导了锁相环、电流控制部分电气量的多频率分布及其幅值特性,得到了各频率分量幅值的近似计算公式;进一步地,分析了所提方法和传统小信号分析方法的区别和联系。通过仿真结果表明,次同步扰动下电压源换流器并网端口会出现互补的次/超同步分量,并伴有幅值较小的多频率分量产生,且其与次同步扰动频率互补的电压分量幅值与积分参数有关,与其他控制参数基本无关。仿真结果与理论推导结果基本一致。

Frequency distribution and amplitude characteristic of electric flux for grid-connected voltage source converter under subsynchronous disturbance

In view of the case that multi-frequency components exists in the voltage response of the converter under subsynchronous voltage disturbances, the characteristics of the frequency distribution and the magnitude in the response are theoretically derived based on the method of the dynamic response analysis with two-order approximation. More specifically, with the two-order perturbation, the frequency distribution and amplitude characteristics of the response for PLL(Phase-Locked Loop) and current inner-loop controller under the subsynchronous voltage disturbance are firstly derived. Subsequently, the difference and similarity of the proposed method with respect to the traditional small signal analysis are discussed. Simulative results indicate that, under the subsynchronous voltage disturbance, the voltage response of the converter at the terminal of PCC(Point of Common Coupling) that is connected to the external power grid includes not only a pair of complementary sub/supersynchronous frequency components, but also a series of complementary small amplitude frequency components. Besides, the amplitude of the largest complementary sub/supersynchronous frequency components is directly related to integral parameters, while is insensitive to other parameters. Simulative results generally coincide with theoretical results.