Non-isolated high step-up three-port DC-DC converter

Aiming at the problems of low output voltage and poor power supply reliability of solar-storage combined power supply system, a non-isolated high step-up three-port DC-DC converter with multiple working modes is proposed. The three ports of the converter share the ground, which are respectively connected to the photovoltaic power generation unit, the energy storage unit and the load. The improved quadratic structure improves the voltage gain and reduces the stress of the switching device. The converter has five working modes, which can meet the requirements of various operating conditions of the off-grid solar-storage power generation systems. In addition, the converter has no voltage constraints between the photovoltaic port and the energy storage port, and is suitable for more occasions. The working principle and steady-state characteristics of the converter in each working mode were analyzed in detail, and the working characteristics were compared with the existing similar converters. According to the control requirements of the solar-storage combined power supply system and the power flow of the converter under different working conditions, the corresponding mode operation and switching control strategies were studied. Finally, a 300 W experimental prototype was built for verification. © 2023 Editorial Department of Electric Machines and Control. All rights reserved.