Ⅱ型不对称三单元CHB逆变器的改进型调制策略

Improved modulation strategy for typeⅡasymmetric three cell CHB inverter

与对称型级联H桥逆变器相比,混合级联H桥逆变器具有使用较少级联H桥单元输出较多电平数的优点,但混合级联H桥逆变器在传统调制策略下存在电流倒灌及其导致的能量反馈问题,针对Ⅱ型不对称三单元混合级联H桥逆变器存在的此类问题,提出一种开关状态函数优化的调制策略,并对调制波进行二次优化,同时对所得脉冲进行逻辑运算及组合。所提策略剔除了存在电流倒灌的开关状态函数,解决了Ⅱ型不对称三单元逆变器在传统调制策略下存在的电流倒灌及能量反馈问题,降低了调制实现的难度,同时保证了输出电能质量。最后通过搭建直流电压比为1∶2∶4的Ⅱ型不对称三单元逆变器仿真模型及实验平台,分析并验证了所提调制策略的可行性及有效性。

Compared with the symmetrical cascaded H-bridge inverter,the hybrid cascaded H-bridge inverter has the advantage of using fewer cascaded H-bridge units to output more voltage levels,but the traditional modulation strategy of the hybrid cascaded inverter has the problems of current backflow and energy feedback.In order to solve the problem of current backflow and energy feedback in the traditional modulation strategy of TypeⅡasymmetric three-unit hybrid cascade H-bridge inverter,a modulation strategy of switching state function optimization was proposed,and on this basis,the modulation wave was optimized twice,and the pulse was logically calculated and combined.The proposed strategy eliminates the switching state function with current backflow,solves the current backflow and energy feedback problems existing in the traditional modulation strategy of typeⅡasymmetric three-unit inverter,reduces the difficulty of modulation realization,and ensures the output power quality.Finally,the feasibility and effectiveness of the proposed modulation strategy were analyzed and verified by setting up the simulation model and experimental platform of TypeⅡasymmetric three-unit inverter with a DC voltage ratio of 1∶2∶4.