级联型多电平逆变器输出电压循环分配的功率均衡控制及优化

Power Balance Control and Optimization Methods With Output Voltage Rotation for Cascaded Multilevel Inverter

在载波层叠脉宽调制（level-shifted pulse width modulation,LS-PWM）策略下,级联H桥型（cascaded H-bridge,CHB）逆变器期望输出电压由多种基本电压波形叠加而成,且在不同的基本电压波形作用下,级联单元的输出功率存在一定的差异。因此要实现级联单元间功率均衡,必须控制级联单元输出电压在一定时间内包含所有使级联单元输出功率不等的基本电压波形。为了实现这一目标,该文结合逆变器输出电平合成方式冗余特性及LS-PWM策略控制自由度思想,提出基于1/4输出周期载波循环的功率均衡控制方法及其优化方案。所提功率均衡控制方法可在不改变逆变器输出电压谐波特性的前提下,在最短的时间内实现级联单元间功率均衡。以三单元CHB型逆变器为例进行理论分析,并通过仿真和实验结果验证理论分析的正确性。

Under the level-shifted pulse width modulation（LS-PWM） strategy,the expected output voltage of the cascaded H-bridge（CHB） inverter is superimposed by a variety of basic voltage waveforms,and the output power of every cell may be different with the different basic voltage waveforms.Therefore,to achieve the power balance among the cascaded cells,the output voltage of every cascaded cell must include all the basic voltage waveforms which have different output power in a certain time.In order to achieve this goal,a power balance control method and its optimization method based on carrier rotation in 1/4 output period were proposed in this paper,which combine the redundancy characteristics of the synthesis methods for the inverter＇s output levels and LS-PWM strategy control degree of freedom.The proposed power balance control method can realize the power balance among the cascaded cells in the shortest time without changing the harmonic characteristics of the output voltage of the inverter.Three cells cascaded multilevel inverter was taking as the example in this paper for the theoretical analysis,and simulation and experimental results were given to verify the correctness of the theoretical analysis.