A Soft-Switched Three-Phase Inductor Coupling Quasi-Z-Source Integrated Charger With Reduced Output Current Ripple for Electric Vehicles

This paper proposes a three-phase inductor coupling quasi-Z-source integrated charger (qZIC) to realize zero current switching (ZCS) and zero voltage switching (ZVS) operation with low current ripple. The conventional qZIC, applying a modified modulation based on modified ZSVM3 (three-segment Z-source Space Vector Modulation), has been proposed due to its capability to achieve fully soft switching without any additional circuits. However, the inductor operates with discontinuous conduction mode (DCM), resulting in significant output charging current ripple. To figure it out, the proposed qZIC substitutes a coupled inductor for the two inductors of quasi-Z-source network. The output current is continuous and ripples are suppressed. In addition, all power switches can still realize ZVS or ZCS by designing the coupled inductor according to the operation principle. The operation principle is analyzed in detail and design considerations are provided. A 6-kW prototype is built to verify the effectiveness of the proposed inductor coupling qZIC. Experimental results demonstrate the elimination of output current ripples, and all switches operate with soft switching.