Circulating zero-sequence current control of parallel three-phase inverters

A novel circulating zero-sequence current-control method for common DC-source parallel inverter systems is proposed and implemented in FPGA. The follower inverter can closely track the three-phase discontinuous PWM modulation waveforms of the master inverter and the circulating current caused by asynchronous modulation waveforms can be reduced. The controller is implemented in FPGA, and the requirement of high-speed control and measurement can be satisfied without any extra burden added to the processor of the drive system. The theoretical analysis of the experimental results verifies the performance of the proposed circulating-currentcontrol method.