A MPC and Novel 3D-SVPWM Modulation Coordinated Strategy for Zero-Sequence Circulating Current Suppression in Three-Phase Four-Leg Parallel-Inverter Systems

The three-phase four-leg (3P4L) parallel-inverter system has been increasingly applied in the field of new energy power generation due to its capability of feeding single-phase loads. However, zero-sequence circulating current (ZSCC) can jeopardize the stable operation of the parallel-inverter system. To address this issue, this paper proposes a ZSCC suppression strategy based on the coordination of Model Predictive Control (MPC) and an improved 3D-SVPWM technique. Firstly, an overall methodology is established by introducing a regulation factor into each switching cycle of the inverter modulation. This introduction enables flexible adjustment of the zero-sequence duty cycle difference between the two inverters, laying the foundation for ZSCC suppression. Secondly, the MPC algorithm is applied to construct a transfer function model of the parallel system incorporating the regulation factor. Closed-loop feedback of ZSCC is introduced, using the deviation between the actual ZSCC and zero as the cost function, and the zero-vector duty cycle adjustment margin as the constraint. The optimal regulation factor is calculated and injected into the improved 3D-SVPWM. Through receding horizon optimization within MPC, disturbances are actively predicted and compensated, achieving precise ZSCC suppression. Finally, simulation results based on Matlab and hardware-in-the-loop (HIL) verify the effectiveness of the proposed strategy.