Circuit Configurable Bidirectional DC-DC Converter for Retired Batteries

Due to the rapid development and widespread usage of Electric Vehicles (EVs), there will be more and more retired batteries in the future. These retired batteries can be used in energy storage systems to stabilize smart grid operation with high penetration of renewable energy. The battery modules used in EVs are equipped with dedicated bidirectional converters. However, if a dedicated bidirectional converter is required for a retired battery, it will cause resource waste and increase the difficulty of reuse. Therefore, it is vital to design and develop a bidirectional DC-DC converter with a wide-range voltage conversion ratio due to the various voltage levels of retired batteries. Especially, the designed converter should have the bidirectional voltage boost and buck abilities to change the different voltage levels of retired batteries for different application scenarios. A circuit configurable bidirectional DC-DC converter for retired batteries is proposed in this paper. The proposed converter is constituted by cascading a two-phase interleaved half-bridge circuit and a voltage-doubler circuit and can be operated in the interleaved boost/buck mode, single boost/buck mode, cascaded-buck-boost mode, or single buck/boost mode concerning the voltage levels at the terminals of the proposed converter. Due to the circuit configurable design of the proposed converter, a wide-range voltage conversion ratio and bidirectional buck and boost abilities can be achieved. A prototype circuit for the proposed bidirectional DC-DC converter with a rated voltage of 150V at the terminal of two-phase interleaved half-bridge circuit, a rated voltage between 25V and 1050V at the terminal of voltage-doubler circuit, and a rated power of 1100W is designed and implemented. Experimental results show that the proposed converter can be configured into the diverse operating modes for different voltage levels and above 98% of the maximum conversion efficiency can be realized.