Single-stage isolated AC-DC hybrid converter for low-power distributed power supply systems

Abstract

Photovoltaic power sources are widely used in smart devices that operate independently of the grid yet require a long-term, stable power supply. Due to the intermittent, fluctuating, and cyclical nature of photovoltaic power generation, power supply systems for these devices often incorporate energy storage components to buffer power fluctuations. However, the integration of energy storage introduces additional power conversion devices, thereby increasing both the overall cost and weight of the power supply system. To this end, this paper proposes a three-port converter that integrates two DC ports and one AC port. This converter can simultaneously connect photovoltaic panels, batteries, and AC loads, enabling flexible control over power flow among the three ports. Compared with existing three-port converters, the topology proposed in this paper features the ability to directly connect to an AC load, while the high-voltage and low-voltage sides are isolated via a high-frequency transformer, making it particularly suitable for low-power distributed applications. In the proposed topology, power transfer among the three ports requires only a single-stage conversion, resulting in high efficiency. Moreover, this topology does not require large-capacitance DC-link capacitors, which enhances the power density and reliability of the converter. Simulation studies based on MATLAB/SIMULINK have verified the feasibility of this proposed topology.