Research on Fast Charging Control Strategy Based on Three-level DC / DC Converter

Aiming at the current problems of low charging efficiency and slow charging speed of electric vehicles, this paper uses a half-bridge three-level LLC resonant converter as the main circuit, and uses the positive pulse charging with stop charging method. The switching stress on the primary side of the topology is only half of the input voltage, and it is easy to achieve soft switching, and the secondary side is an uncontrolled rectifier composed of diodes. A hybrid control strategy combined with phase shift control is proposed in order to solve the problem that the voltage can be adjusted in a small range when the frequency modulation control strategy is adopted in this topology. Using the model of a half-bridge three-level LLC resonant converter, the positive pulse charging and stop charging are compared with constant current charging through Simulink, the correctness and effectiveness of positive pulse charging with stop charging were verified. The system efficiency and charging speed were improved.