模块化多电平换流器(modular multilevel converter,MMC)近年来得到了广泛的发展与应用.电容器是MMC中子模块(sub-module,SM)的重要组成部分与关键元件,承担直流支撑与储能工作.为保证MMC系统的安全可靠运行,有必要对子模块电容器状态监测方法展开研究.基于MMC系统运行特性,提出一种在工频周期内对子模块电压进行多相位点采样,并结合系统控制侧开关信号、调制比与交流侧电流电压幅值、相位等信息构建电压电流状态方程,以求解电容值与等效串联电阻(equivalent series resistance,ESR)值等状态特征参量的子模块电容器状态监测方法.随后搭建单相七电平MMC系统仿真平台与半实物仿真平台,对上述方法的可行性与准确性进行验证.仿真结果表明子模块电容器C值监测误差绝对值小于0.03％,ESR值监测误差绝对值小于0.5％.实验结果表明C值监测误差绝对值小于1.5％,ESR值监测误差小于10％,满足子模块电容器状态监测要求.
Condition Monitoring Method for Sub-module Capacitance and ESR in Modular Multilevel Con-verter Based on Multi-point Sampling of Capacitor Voltage
Modular multilevel converter(MMC)has been widely developed and used in recent years.As an important part in sub-modules(SMs)of MMCs,capacitors play the role of DC support and energy storage.Thus,it is necessary to carry out the research on the sub-module capacitor condition monitoring to ensure the safe and reliable operation of MMC sys-tems.In this paper,an online condition monitoring method was proposed.Firstly,by utilizing this method,multi-point sampling was performed on the voltage of sub-modules within the power frequency cycle,and then information including the IGBT switching signals,modulation ratio,AC side current and voltage,amplitude,and phase is combined to construct voltage and current state equations.Finally,the capacitance value and equivalent series resistance(ESR)value can be ob-tained by solving the equations.The accuracy and effectiveness of the proposed method are verified by the simulation of the single-phase seven-level MMC system and the hardware-in-the-loop experiment.The simulation results indicate that the maximum absolute errors for the C value and the ESR value are 0.03％and 0.5％.The experimental results show that the maximum absolute errors of C value and the ESR value are 1.5％and 10％,which meets the requirements of submod-ule capacitor status monitoring.
modular multilevel converter(MMC)sub-module(SM)capacitorequivalent series resistance(ESR)condi-tion monitoring(CM)
万方数据
维普
