Power Quality Enhancement of Unbalanced Vehicle Microgrids by T-Type Converters Using Dual-Flexible Model Predictive Control

Power quality of a vehicle microgrid is seriously affected by an unbalanced load. The operation of single-phase loads (unbalanced loads) will incur an imbalance problem in such a system. The power fluctuation caused by voltage imbalance endangers the system’s reliability and shortens its service life. Existing control methods for such problems often focus on suppressing power fluctuations. To maintain the high-quality ac-bus voltage of the microgrid while ensuring power output, this article investigated a flexible model predictive control (F-MPC). First, based on the traditional flexible power control, the control layer based on MPC is optimized, and the selection of adaptive coefficients is improved. Second, a new voltage vector selection method based on dual-flexible MPC (DF-MPC) control is designed to preferentially select the optimal vector for voltage drop compensation. The method is tested on a prototype hardware platform with a rated power of 10-kW. Experimental results show that the proposed DF-MPC method can effectively reduce the imbalance of grid voltage while maintaining high power quality.