Synthesis and Control of a Three-port LCL Resonant Wireless Power Transfer System for DC Energy Conversion Applications

This paper proposes a three-port LCL resonant wireless power transfer system with hybrid power flow control methods for DC-DC energy conversion applications. The proposed topology is suitable for interfaced DC energy storage, PVBattery, and DC microgrid with active load application conditions. Two half-bridge micro inverters provide the dual input ports for the DC energy sources while the load port is connected by an LCL-LCL type wireless coupling tank with a full bridge rectifier. This three-port topology allows free power transfer between dual input sources while the two sources share one LCL resonant tank to transfer energy to the load without additional circuit components. The control function of this proposed system can be divided into two phases: Phase 1 Pulse width modulation (PWM) method is employed to implement bidirectional power transfer between dual input sources by controlling the average DC offset current in the LCL resonant tank. Phase 2 Phase shift modulation method (PSM) is applied to regulate the wireless output power in the load port. In addition, the proposed system allows the dual input port sources to have unbalanced voltage levels. The theoretical time domain analysis of the proposed topology and LCL coupling tank is presented in detail. The simulation model is built up in the PSIM environment, open loop simulation is carried out to obtain the power transfer characteristics between the multiple ports and closed loop simulation is done to verify the efficiency of the designed control method. A 200W prototype was configured to demonstrate the performance of the proposed topology. Experimental results show that the proposed system can achieve a peak efficiency of 93.6% (under the condition of dual inputs 36V DC with only wireless power output) with the load-independent constant current performance achieved