Digital Three‐Port Resonant Converter Applied to Microphotovoltaic Power Generation Systems

ABSTRACT In this study, a digital triple‐port resonant converter (DTRC) is proposed for the voltage regulation of a system comprising a microphotovoltaic power generation system (MPVPGS), a lithium‐ion battery pack, and a DC bus. To enhance power generation, the maximum power point tracking perturb and observe (MPPT‐P&O) was applied. The circuit comprised a dual active bridge converter, a CLLLC resonant tank, a dual boost converter, and isolated and nonisolated 3P2Z controllers. For battery pack charging by the MPVPGS, symmetrical pulse‐width modulation (PWM) and synchronous switching were used to increase the output voltage and reduce current stress on the switches. For power supply to the DC bus, asymmetrical PWM and interleaved switching were used to achieve zero‐voltage and zero‐current switching, reducing input current ripple; this solution is a simpler method of output voltage control than conventional variable frequency control (VFC) by resonant converters. For battery discharging to the DC bus, VFC was used to adjust the output voltage, and zero‐voltage and zero‐current switching was achieved. This paper presents the operating principles, characteristics, design considerations, and control strategies of the 3P2Z controllers for DTRC. Moreover, a 2‐kW prototype circuit was constructed, and the operating characteristics were confirmed in the battery charging, battery discharging, and DC power supply scenarios.