Renewable energy systems have gained continuous attention for achieving “carbon peak” and “carbon neutrality”, especially DC conversion technologies for renewable energy conversions. Multi-port converter (MPC) has been widely applied in renewable energy systems and electric vehicles due to the characteristics of low cost, high efficiency, and high power density. The non-isolated MPC suffers poor stability due to insufficient electrical isolation between ports. In contrast, isolated converters are often more complex and less flexible. Wireless power transfer (WPT) technology offers convenience, safety, flexibility, and the ability to charge multiple devices, effectively achieving electrical isolation between input and load ports. Thus, combined with WPT and MPC technologies, this paper proposes a three-port DC-DC converter with integrated wireless power transfer capability. The proposed topology facilitates DC power transfer between multiple DC sources with the same or different voltage levels. It enables wireless power transfer between DC sources and load by introducing WPT coupling technologies. The system achieves non-contact hot plug & play between DC loads and the power grid side, which indirectly isolates the impact of the load on the power grid.

The system employs a hybrid power flow control method, with dual half-bridge micro-inverters providing the dual input ports. The load port is wirelessly coupled through an LCL-LCL-type resonant coupling network connected to a full-bridge rectifier. This three-port topology is simple and highly flexible, allowing free power transmission between dual input sources, with the two sources sharing one LCL resonant tank for power transmission to the load without any additional circuit components. System control strategies can be divided into two phases: Phase1: pulse width modulation (PWM) controls the power flow between two DC sources by controlling the average DC offset current in the LCL resonant tank, enabling bidirectional power transmission; Phase 2: phase shift modulation (PSM) control method adjusts the wireless output power for DC load. These two control loops can operate independently or be combined for comprehensive control. The absence of coupling between these methods enhances the stability and effectiveness of each control function. Additionally, the system allows for dual input ports with unbalanced voltage levels.

Firstly, a dual-sided LCL resonant coupling network model is established based on the AC impedance method to analyze its frequency limitations under constant voltage and constant current output characteristics. Secondly, the system topology’s various operating states are analyzed based on switching modes. The overall system model is developed using time-domain analysis, and a small-signal model of the resonant coupling network is established to determine the primary-side PWM control and secondary-side PSM control strategies. Thirdly, a simulation model is built in PSIM to verify the system’s functionality. Matlab/Simulink is used to optimize the parameters of the compensation network. Finally, an experimental platform is set up in a microgrid and energy storage interconnected system to evaluate the system's dynamic characteristics under different voltage levels and load conditions, efficiency variations, steady-state control performance of the closed-loop controller, and dynamic response characteristics.

Experimental results show that under dual inputs of DC 36 V with only wireless output, the system achieves a peak efficiency of 93.6% and load-independent constant current output performance. The system effectively controls the power flow direction and magnitude between the primary-side energy ports, and the designed controller maintains stable load power even under sudden changes in load resistance and voltage levels at the dual half-bridge energy ports. The controller also demonstrates good robustness and dynamic response performance.