Design of current controller with circulation current reduction for parallel three phase voltage inverter

A circulating current is a major problem introduced by directly connecting voltage source inverter (VSI) in parallel. This circulating current occurs as a zero-sequence current between the inverters by specic switch states. Its alternatives were presented by hardware and software methods in many papers. When coupled inductor (CI) are employed for the high frequency circulating current, a circulating current controller is required to avoid the saturation of the CIs by the low frequency circulating current. In this chapter, the zero sequence circulating current (ZSCC) and its alternatives are investigated by the hardware and mathematical descriptions. A high performance circulating current controller is proposed by applying are repetitive controller (RC) to the zero-sequence current control loop. The proposed controller can effectively minimize the low frequency circulating current without any data sharing between the inverters in unfavorable conditions. Furthermore, this can be applicable to modular congurations of parallel three-phase VSIs. The performance of the proposed controller is veried by the simulations and experiments.