MMC中压电机驱动系统全转速范围电容轻量化研究

Research on Capacitor Lightweight in Full Speed Range of MMC Medium Voltage Motor Drive System

模块化多电平换流器(modular multilevel converter,MMC)应用于中压电机驱动系统时存在子模块电容尺寸过大的问题,在电机低速运行时尤其明显。文中提出一种基于横向子模块互联的低容值MMC(low capacitance MMC,LC-MMC)电机驱动系统,利用拓扑特点实现了系统在电机全转速范围内的电容轻量化。LC-MMC基于横向子模块输入波动电流的三相对称性,在互联通道中实现了他们的相互抵消,从而大幅减小了子模块电容尺寸,并且不受电机运行频率的影响。文中从传统MMC电机驱动系统出发,分析其对子模块电容的具体需求;对所提LC-MMC实现全转速范围内的电容轻量化方案进行详细介绍;然后,对两种MMC电机驱动系统进行对比评估,并分析LC-MMC的共模电压自然抑制特性;最后,对所提LC-MMC方案进行仿真与实验验证。

When modular multilevel converter(MMC)is used as a medium voltage motor drive system,it has the problem of oversized submodule capacitor,which is more obvious when the motor is running at low speed.This paper proposes a low capacitance MMC(LC-MMC)motor drive system based on horizontal submodule interconnection.It makes use of topological characteristics to realize the capacitor lightweighting in the full speed range of the motor.Based on the three-phase symmetry of the input fluctuating current of the transverse submodule,LC-MMC realizes the cancellation of the fluctuating current in the interconnection channel.Thus,the size of the submodule capacitor is greatly reduced,and its implementation is not affected by the motor operating frequency.This paper first analyzes the specific requirements of the submodule capacitance of the traditional MMC motor drive system.Secondly,the proposed LC-MMC capacitor lightweighting scheme in the full speed range is introduced in detail.Then,two kinds of MMC motor drive systems are compared and evaluated,and the common mode voltage natural suppression characteristics of LC-MMC are analyzed.Finally,the proposed LC-MMC scheme is verified through simulation and experimentation.