A Low-Harmonic Control Method of Bidirectional Three-Phase Z-Source Converters for Vehicle-to-Grid Applications

Three-phase Z-source inverters provide a solution of voltage boosting by a single-stage topology. They are also capable of bidirectional operation as rectifiers, thus have great potential for applications in the field of transportation electrification such as vehicle-to-grid (V2G) chargers. In this article, three new modulation schemes for three-phase Z-source converters are proposed and investigated. The best performed one is further developed to a closed-loop proportional-integral (PI) control method. Although the voltage conversion ratio is flexible, the output voltage total harmonics distortion (THD) is below 3% within the voltage ratio range 0.5-2.5. The effectiveness of the proposed method has been fully validated in MATLAB/Simulink simulations and RT-Lab hardware-in-loop (HIL) experiments based on the real-time simulator OPAL-RT OP4510. Compared to existing control methods, the proposed one performs better with reduced harmonics, flexible voltage gain, and simpler control algorithm.