Fully Decoupled Branch Energy Balancing Control Method for Modular Multilevel Matrix Converter Based on Sequence Circulating Components

The modular multilevel matrix converter(M3C)is a potential frequency converter for low-frequency AC transmission.However,capacitor voltage control of high-voltage and largecapacity M3C is more difficult,especially for voltage balancing between branches.To solve this problem,this paper defines sequence circulating components and theoretically analyzes the influence mechanism of different sequence circulating components on branch capacitor voltage.A fully decoupled branch energy balancing control method based on four groups of sequence circulating components is proposed.This method can control capacitor voltages of nine branches in horizontal,vertical and diagonal directions.Considering influences of both circulating current and voltage,a cross decoupled control is designed to improve control precision.Simulation results are taken from a low-frequency transmission system based on PSCAD/EMTDC,and effectiveness and precision of the proposed branch energy balancing control method are verified in the case of nonuniform parameters and an unbalanced power system.

基于子模块瞬时功率跟随模块化多电平矩阵变换器控制策略

通过特殊矩阵结构下各桥臂级联子模块的瞬时功率特性分析,提出了一种基于子模块瞬时功率跟随的三相六桥臂模块化多电平矩阵变换器控制策略。桥臂间电容电压均衡控制环采用电容电压直流量偏差值及差频纹波的混合反馈,实时跟随瞬时功率幅值包络线注入高频共模电流,经由同一闭环实现二者的整体控制,可解决桥臂间无功分配差异和差频电压波动对变换器应用范围的限制;在单一环流路径约束下,叠加输出频率环流调节桥臂间非零序有功偏差,叠加输入频率环流调节相间平衡,环流闭环合成方式不影响控制独立性且易于实现。桥臂电流控制环可实现交流两侧端口电流及内部环流的解耦控制,无需复杂的矢量变换。最后通过不同工况实验验证了该方法的有效性。