模块化多电平环流抑制与载波调制策略研究

Research on Circulating Current Suppressing and Carrier Modulation Strategy of Modular Multilevel Converter

为抑制模块化多电平变换器(MMC)的内部环流,提出了两种环流抑制方案:方案1只抑制环流中的交流分量,方案2采用既抑制交流分量同时控制直流分量的控制策略;方案2与方案1相比具有较快的动态响应特性。对各种多电平脉宽调制(PWM)技术进行了比较分析,并重点研究了上、下桥臂分别采用载波交错PWM和非交错PWM时对桥臂电流、子模块电容电压和输出电压、电流的影响,研究结果表明:采用载波交错PWM可改善输出电压、电流波形,但会增加桥臂电流纹波。最后通过Matlab/Simulink仿真和实验验证了理论分析的正确性和所提控制策略的有效性。

In order to suppress the inner circulating current in modular multilevel converter（MMC）,this paper proposes two suppressing technical schemes：technique 1 is aimed at elimination of the ac component in the circulating current, and technique 1 is aimed at suppressing the ac component and control the DC component of the circulating current.Technique 2 has fast dynamic response characters compared with technique 1.Then, analysis and comparison of various kinds of multilevel pulse width modulation （PWM） is given.The performance of interleaving and non-interleaving the carrier waveforms between the upper and the lower arms is presented.The study result shows that the interleaving modulation can improve the output voltages and currents,but increases the ripple in the arm currents.Finally, both the simulation by Matlab/Simulink and experimental results demonstrate the correctness of the theoretical derivation and the effectiveness of the proposed control scheme.