Output Voltage Ripple Suppression Strategy for Light DC-link Capacitor DC-Type EV Charger

In DC-Type electric vehicle (EV) chargers, the implementation of a two-phase clamped discontinuous pulse width modulation strategy has effectively reduced the switching losses in the front AC/DC converter and decreased the required capacitance of the DC-link. However, reduced DC-link capacitance can cause fluctuations in the DC-link voltage, which, in turn, result in output voltage fluctuations. In order to address such issues, this paper proposes an output voltage ripple suppression strategy based on the time-domain analysis of the back-stage LLC resonant converters. With the proposed control method, the theoretical feedforward coefficients can be calculated by fitting the three-dimensional time-domain analysis curve. Finally, the 10 kW prototype is built to validate the feasibility and effectiveness of the proposed control strategy.