Three-phase Z-source inverters provide a solution of voltage boosting by a single-stage topology. They are also capable of bi-directional operation as rectifiers, thus have great potential for applications in the field of transportation electrification such as Vehicle-to-Grid (V2G) chargers. In this paper, 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 PI control method. While the voltage conversion ratio is flexible, the output voltage Total Harmonics Distortion (THD) is below 3% within the voltage ratio range of 0.5 to 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 realtime simulator OPAL-RT OP4510. Compared to existing control methods, the proposed one performs better with reduced harmonics, flexible voltage gain, and simpler control algorithm.