A Low-Harmonic Control Method of Bidirectional Three-Phase <i>Z</i>-Source Converters for Vehicle-to-Grid Applications
Wenzheng Xu, Ka Wing Chan, Siu Wing Or, S. L. Ho, Ming Liu
Abstract
Three-phase <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Z$ </tex-math></inline-formula> -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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Z$ </tex-math></inline-formula> -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.