A bi-directional AC-DC converter for electric vehicle with no electrolytic capacitor

An isolated single-stage bi-directional AC-DC converter with no electrolytic capacitor for electric vehicle battery charger application is proposed. The topology utilizes a single-stage series resonant dual Half-bridge AC-DC converter to transfer the power and an active-shunt filter on the DC-side to absorb the 100/120Hz current ripple and prevent it from going to the battery. Diverting the low frequency ripple to the active filter prevents extra heat production in the battery and increases of the lifespan of the battery. Also film capacitors, instead of electrolytic capacitors with a lower lifetime, can be used on the DC-side filter. The reliability of the system is increased by not using an electrolytic capacitor in the circuit. To control the circuit for a wide range of power and power angle under soft switching, a four-part controller is proposed. The controller obtains ZVS for all the active switches while it optimizes the performance of the system in terms of conduction losses. ZVS operation of the circuit, enables the switching frequency to increase without increasing the switching losses. Increased switching frequency will result in smaller reactive components and smaller transformer size. The proposed controller obtains the best performance from the circuit. Simulation results with PSIM and experimental results to verify the theory have been carried out.