基于电流型多电平变流器的单相光伏并网系统

摘要

To adopt the multilevel current source inverter as the circuit interface of the photovoltaic grid connected power system can not only reduce the switching frequency and current stress of switching devices, but also make the grid side current get better harmonic characteristics. In order to get better harmonic perfor-mance, POD-PWM modulation is adopted for the multilevel cur-rent source inverter, in order to realize the balancing control of shunt inductor current through the DC side current feedback. Fi-nally, through PLL control, the current output by the multilevel current-source inverter is made to track the grid voltage, thus re-alizing grid connection. Single-phase five-level current photo-voltaic grid connected inverter system is designed based on PSIM simulation environment, in order to validate the correctness and feasibility of the above scheme.%采用单相电流型多电平变流器作为光伏并网发电系统的电路接口，可以降低开关器件的开关频率和电流应力，同时可以使电网侧电流获得更好的谐波特性。为获取更好的谐波性能，电流型多电平逆变器部分采用POD-PWM调制，并通过直流侧电流反馈实现分流电感电流的均衡控制。最后，通过锁相环控制，使多电平逆变器输出的电流跟踪电网电压，实现并网。基于PSIM仿真环境，设计了单相五电平电流型光伏并网逆变系统，对上述方案的正确性和可行性进行了验证。