级联多电平光伏并网逆变器研究

摘要

Cascaded H-bridge is used as the main circuit topology of a photovoltaic inverter.Using carrier phase-shift sinusoidal pulse-width modulation (CPS-SPWM) technology, it can increase the number of output voltage level and reduce the output voltage harmonics.Applying a double-loop(outer voltage loop,inner power loop) grid-connected control strategy,voltage loop can independently control the DC side voltage of each unit,making an independent maximum power point tracking,power loop can not only control the power factor of the output current,and can balance the power output of each unit.Finally, simulation and experiment verify the correctness of the theory.%介绍了采用级联H桥的光伏并网逆变器拓扑结构.调制方式上选择载波相移正弦脉宽调制技术(CPSSPWM),该技术可增加输出电压电平数并使其谐波含量更小.采用电压外环、功率内环的双闭环并网控制策略,电压环可独立控制各单元的直流侧电压,使得每个单元都可跟踪各自的最大功率点(MPP)；功率环不仅可控制输出电流的功率因数,而且可平衡各单元的功率输出.最后通过仿真和实验验证了理论的正确性.