Control Design of a Dual-Input LLC Converter for PV-Battery Applications

This paper proposes a control technique for a three-port resonant-based dc/dc converter. A dual-input LLC resonant converter that interfaces with a PV and an energy storage source is studied. The topology is a dual half-bridge LLC circuit with four active switches. This topology allows the two sources to share the same resonant tank for transferring energy to the load without the need for additional circuit components. In the proposed controller, four operation scenarios are taken into account; PV to load, battery to load, PV and battery to load, and PV to battery and load. Three control variables; switching frequency, duty cycle, and phase shift are employed in the controller to implement maximum power point tracking (MPPT) and power flow control among the three ports in each scenario. A 500-W prototype was built to demonstrate the performance of the proposed controller. The PV input voltage range is selected to be 25 V to 50 V, and the battery voltage is 60 V, with an output voltage regulated at 400 V DC. Experimental results validate the proposed controller's performance in implementing MPPT and power flow control for the three ports in four operation scenarios using the three control degrees of freedom.