ZSCC suppression method for parallel three-level inverters based on model predictive control with virtual location vector

Parallel three-level neutral point clamped (3L-NPC) inverters are widely used in power conversion applications, such as new energy generation and high voltage inverters. However, the zero-sequence circulating current (ZSCC) between two inverters degrades the whole performance of the system. To suppress the ZSCC in parallel inverters and improve the quality of output current, this study proposes an MPC strategy based on the virtual location vector. First, to reduce the computational burden of MPC, the virtual location vector is constructed by the output current of two inverters so that the control of the parallel inverters is similar to that of a single inverter. Then, the virtual location vector is obtained by using the direct power control method. Finally, the sets of candidate voltage vectors for MPC are determined on the basis of this reference voltage vector and the magnitude of ZSCC. Moreover, the optimal vectors calculated by MPC are assigned to the two inverters. Compared with the traditional MPC strategy, the MPC strategy proposed in this study has better steady state and transient performance with less computational burden. The proposed method is validated in simulation and experimental platforms.