Bipolar DC Bus Fluctuation Suppression of Electrolytic Capacitorless Vienna Rectifier for EV-Charging Stations

Due to varying charging power and rates, electric vehicle (EV) charging stations require Vienna rectifiers to supply different DC-link voltages, and the reduction of capacitance leads to the increased bipolar DC bus voltage fluctuation and affects the grid-side power quality. A weighting fuzzy adaptive model predictive control (WFA-MPC) strategy is proposed to achieve synergistic suppression of the bipolar voltage fluctuations and the input current harmonics. The extreme components of the neutral point (NP) current are analyzed in conjunction with the clamping modes to characterize the voltage vector restricted areas of the conventional finite control set model predictive control (FCS-MPC) under the unbalanced DC voltage. To suppress input current distortion and the bipolar voltage fluctuations, the NP current control capability is increased by optimizing the finite set of voltage vectors in the restricted areas. Furthermore, a weighting fuzzy adaptive strategy is utilized to adjust the weight factor online according to the input current and unbalanced DC voltage errors, and the precise weight factor range is determined by the Pareto optimality. Finally, the effectiveness of the proposed strategy is verified on an electrolytic capacitorless Vienna rectifier platform.