基于虚拟输出阻抗分析的并联三相四桥臂逆变器环流抑制

Output Impedance Analysis for Circulating Current Minimization of Paralleled Three Phase Four Leg Inverter

三相四桥臂(3P4L)逆变器在三相三桥臂逆变器的基础上引入第四桥臂,使得三相能够解耦控制并具备带不对称负载能力。多个逆变单元共输入、输出方式并联,能够实现功率扩容,但同时也带来并联单元之间的环流问题。而3P4L由于其独特的拓扑结构,其并联控制策略较单相或三相三桥臂逆变器并联更为复杂。在基于双闭环平均电流均流控制的并联3P4L逆变器控制策略基础上,建立并联系统的小信号模型,并由此获得并联桥臂的虚拟输出阻抗模型。分析控制环路以及主电路参数与虚拟输出阻抗的关系,根据分析结果指导环路与主功率器件的参数设计,达到抑制并联桥臂环流、提高并联单元均流性能的目的,最后提出基于虚拟输出阻抗分析法的并联环流抑制方法,通过仿真和实验验证了该方法的正确性。

Compared to three-phase three-leg inverter, the control of three-phase four-leg（3P4L） inverter could be decoupled to be able to work with unbalanced load. In recent years, parallel inverter has been widely used in power electronic converter system. If current is out of control in parallel inverters connected with the same input and output buses, circulating current will exist in four legs of parallel 3P4 L inverters, which may damage converter seriously. Based on dual closed loop control strategy, output impedance modeling is created in this paper by using small signal modeling method. Thereby, output impedance analysis about the relationships between control loop parameters, main circuit and output impedance is accomplished. Accordingly, a design method is proposed to minimize circulating current. Finally, simulation and experimental results verify the analysis method.