Novel Three-Port Bidirectional DC/DC Converter with Three-Winding Coupled Inductor for Photovoltaic System

Abstract

This study proposes a novel three-port bidirectional converter with a three-winding coupled inductor and applies it to a photovoltaic (PV) system to step up the PV system output to a dc bus or dc load while charging the battery. When the PV output is insufficient, battery voltage is stepped up to the dc bus voltage, and when the dc bus has excess energy, it is stepped down to charge the battery. Thus, a three-port bidirectional high step-up/step-down converter is achieved. A three-winding common core coupled inductor is designed and implemented in the converter, and a full-wave doubler circuit is used on the high-voltage side to achieve a high step-up effect. Power switches and diodes in the circuit are shared to achieve bidirectional operation. The output capacitors recover secondary-side leakage inductance energy in the step-up mode, and the third winding can be used to recover primary-side leakage inductance energy to reduce the voltage spike on switching in order to improve the converter’s conversion efficiency. A 500-W three-port bidirectional converter is implemented to verify the feasibility and practicability of the proposed topology. According to the measurement results, the highest efficiency of the PV step-up mode is 95.3%, the highest efficiency of the battery step-up mode is 94.1%, and the highest efficiency of the step-down mode is 94.8%.

Novel High-Step-Up/Step-Down Three-Port Bidirectional DC/DC Converter for Photovoltaic Systems

“…The number of components is too many to increase the cost, and the efficiency of the proposed converter is better than that of [29]. The performance index of [30] is moderate.…”

“…Furthermore, the efficiency in [21] obviously declined when the system operated at heavy power, and thus, the system can only operate at a maximum power of 200 W. As for [22], although the system could operate at 1 kW, its efficiency did not even reach 90% when operated above 500 W. In addition, switch controlling was very complicated. Table 2 presents a comparison between the proposed converter and those described in [24,25,[28][29][30], all of which are three-port converters. The highest conversion efficiency shown in Table 2 is the calculated efficiency for energy conversion from PV modules to the DC bus, and the proposed converter has an obvious superiority in conversion efficiency.…”

“…However, the count of components in [29] is higher than that of the proposed converter and the voltage gain in [28] is lower than that of the proposed converter. As proposed in [30], a three-winding common core coupled inductor was designed and implemented in the converter. If a topology can combine the advantages of bidirectional and three-port converters, the system's size and cost can be further reduced, and this was the main purpose of the present study.…”

Analysis and Design of a New Non-Isolated Three-Port Converter With High Voltage Gain for Renewable Energy Applications

“…The TPC topologies can be classified into three types: fully-isolated TPCs (FITPCs) [4], [5], partly-isolated TPCs (PITPCs) [6]- [8], and non-isolated TPCs (NITPCs) [9]- [23]. PITPCs and FITPCs suffer from topology complexity and low efficiency; the NITPCs are widely adopted in the ESS resulting in compact size and high efficiency.…”