Dynamic Suppression Method for Circulating Current in Multi-Parallel Two-Level Inverters Based on MPC

Circulating current (CC) is a disadvantageous factor that must be eliminated in parallel two-level inverters, which will degrade the quality of the output current or even cause a system crash. Common mode voltage (CMV) is the main factor that generates CC. Conventional model predictive control (MPC) can achieve circulating current suppression by synthesizing zero CMV voltage vectors, but this type of method usually relies on the rich vector selection of three-level inverters and is difjicult to apply in two-level inverters. The current control methods have low current tracking accuracy and cannot suppress the fluctuation of the CC caused by the random variation of the CMV during the dead period. In this article, a multi-vector MPC method is proposed, which constructs a zero CMV combination vector to achieve CC suppression without changing the current tracking accuracy of the conventional three-vector MPC at all. Moreover, dynamic CC suppression according to the magnitude of CC amplitude is proposed, which can further reduce the CC and regulate the CC offset. Finally, the effectiveness of the proposed method is verified with comprehensive simulation.