三相CHB多电平光伏并网逆变器功率平衡控制策略研究

Research on Power Balance Control Strategy for Three-phase Cascaded H-bridge Multi-level Photovoltaic Grid-connected Inverter

针对级联H桥多电平光伏并网逆变器因光照和温度等因素影响而产生的功率不平衡问题,提出了一种双最小-最大零序注入法的功率平衡控制策略。根据逆变器的电压电流矢量图,明确了功率不平衡问题的产生机理,并分析对比了不同零序注入法的构成方式及实现方法。双最小-最大零序注入法可以增大逆变器的功率调节范围,在功率严重不平衡的条件下依然能够输出三相平衡电流,具有良好的动态和稳态特性。仿真算例验证了所提出的方法的有效性和可行性。

To solve the power imbalance problem of a cascaded H-bridge multi-level photovoltaic grid-connected inverter,which may be caused by factors such as uneven illumination and temperature,a double min-max zero-sequence injection(DMMZSI)method is proposed in this paper.By establishing and analyzing the vector diagrams of voltage and current in the inverter,the mechanism of interphase power imbalance is clarified.In addition,the composition and implementation of different zero-sequence injection methods are analyzed and compared.The DMMZSI method can increase the adjustment range of the inverter power and output the three-phase balanced current even under the condition of severe power imbalance,showing excellent dynamic and steady-state characteristics.Finally,the simulation results of an example verify the effectiveness and feasibility of the proposed method.