基于谐波线性化的模块化多电平换流器阻抗建模

摘要

模块化多电平换流器(MMC)的小信号阻抗建模是分析含MMC的电力系统谐振及稳定性的关键.MMC是一个多频率、非线性、周期性时变的系统,具有复杂的内部动态特性,传统的小信号建模方法无法直接用于MMC.采用谐波线性化法对MMC的交流侧小信号阻抗进行建模,计及谐波环流和电容电压稳态纹波的影响,并揭示了环流控制对MMC交流侧阻抗的作用机理.利用MATLAB/Simulink搭建三相MMC详细时域仿真模型,仿真测量结果验证了解析模型的正确性.%The small-signal impedance modeling of modular multilevel converters (MMCs) is the key for the resonance and stability analysis of MMC-based power systems.MMC is a converter system featuring multi-frequency,nonlinearity and periodically time-varying operation trajectory due to its complex internal dynamics.Hence,traditional small-signal methods cannot be directly applied to MMC.The AC-side small-signal impedance of MMC is modeled by the harmonic linearization method,which has taken into consideration the harmonic circulating current and capacitor voltage steady-state ripples.Furthermore,the influence of the circulating current control on the AC-side impedance of MMC is analyzed.A detailed timedomain simulation model of a three-phase MMC is built by using MATLAB/Simulink and the analytical models are validated by simulation results.