三电平H桥级联逆变器载波移相脉宽调制方式

在三电平H桥级联（3-LHC）多电平主电路中，传统的载波层叠脉宽调制难以实现各级联单元的功率平衡，而基于两电平级联的载波移相脉宽调制又不能直接运用.中点箝位（NPC）三电平桥臂内只能采用载波层叠脉宽调制，而H桥的桥臂间和各H桥之间则既可以采用载波层叠脉宽调制也可以采用载波移相脉宽调制.基于这一原理，提出了2种适合3-LHC多电平的载波移相脉宽调制方式，分别为基于五电平、三电平载波层叠的载波移相脉宽调制.前者仅在级联单元间使用载波移相，而后者在级联单元间和桥臂间均采用载波移相.仿真对比分析结果表明，基于五电平载波层叠的载波移相脉宽调制是该拓扑中较理想的调制方式.实验结果证实该方法具有很好的效果

Carrier phase shift PWM techniques of three-level H-bridge cascaded multilevel inverter

The conventional carrier disposition pulse width modulation(PWM) in the three-level H-bridge cascaded(3-LHC) multilevel inverter cannot balance the power of each H-bridge,and the two-level based carrier phase shift PWM cannot be used directly.The neutral-point clamped(NPC) three-level leg can only adopt the carrier disposition PWM,while three-level legs and H-bridges can select either carrier disposition PWM or carrier phase shift PWM.This work proposed two new types of carrier PWM: five-level based phase shift carrier PWM which uses phase shift only in H-bridges,and three-level based phase shift carrier PWM which uses phase shift both in H-bridges and three-level legs.Comparison of these two new methods by simulation shows that the former is better for the multilevel inverter,and the experimental study shows that it is effective.