A Multiport Bidirectional DC-DC Converter for Hybrid Renewable Energy System Integration

The bidirectional power flow in most of the existing four-port converters is achieved on the battery port located on the low voltage side, i.e., the battery is charged by the energy sources and discharged to the dc link on the high voltage side. The lack of the bidirectional power flow at the dc link prevents them from managing the power at the system level. In this article, a bidirectional four-port dc-dc converter is proposed for the integration of the hybrid renewable energy system to a dc microgrid. The proposed converter uses the least number of devices compared with the existing bidirectional multiport converters. The bidirectional battery and the dc-link ports make it a good candidate for the dc-microgrid application in which the system-level power management is desired. The working principle of the converter is first analyzed, and the power transferred by the transformer and the zero-voltage switching (ZVS) conditions are derived. Then, the converter is designed to meet the requirements of the power rating and soft switching. The proposed converter is used to interface a wind turbine, a photovoltaic panel, a battery bank, and the dc microgrid. The experiments are carried to testify the performance in both steady state and the transient. The steady-state waveforms have validated the power relationship as well as the critical ZVS conditions while maintaining relatively high efficiency. The transient testing results show that the converter can switch from one scenario to another under the different conditions. This article is accompanied by a video demonstrating the converter in the real-time operation.