A Two-Stage Three-Phase Integrated Charger for Electric Vehicles With Dual Cascaded Control Strategy

A new three-phase integrated onboard charger and derivative control strategy are proposed and implemented in this paper. The integrated charger is composed of a three-phase interface and the traction propulsion system of the vehicle. The three-phase interface is derived based on the traditional three-phase three-switch buck ac-dc converter and is integrated with the propulsion system to construct an integrated buck-boost charger, in which the inverter is reconfigured to operate as an interleaved converter. The motor windings are used as the inductors of the integrated buck-boost charger. A dual cascaded control strategy is designed for the two-stage charger. The first cascaded control regulates the battery voltage and the motor-winding currents, while the second cascaded control modulates the input filter inductor current and the input filter capacitor voltage. The integrated charger is modeled and analyzed to design the controllers, considering the sensitivities of duty cycle to the input filter inductor current and to the input filter capacitor voltage, and the sensitivity of the modulation index to the motor-winding currents. A 1.5-kW prototype is designed and developed to verify the feasibility of the proposed integrated charger and the control strategy.