A Single-Magnetic Bidirectional Integrated Equalizer Using Multi-Winding Transformer and Voltage Multiplier for Hybrid Energy Storage System

Abstract

A single-magnetic bidirectional integrated equalizer using the multi-winding transformer and voltage multiplier for the hybrid energy storage system is proposed. The multi-winding transformer and voltage multiplier, driven by the current ripple of the inductor in the bidirectional buck-boost converter, are used for the battery string and supercapacitor string voltage balance, respectively. Compared to the previous balance circuits, for the schedule of the proposed equalizer, only one winding and one diode are used for each battery. Meanwhile, one capacitor and two diodes are used for each supercapacitor, simplifying the balance circuit. This method has the advantages of low cost, suitable for cells with different voltage levels, multiplexed converter switches, and extremely simple structure. It does not have any active switch for the voltage balancing function. A prototype for four supercapacitor cells and four batteries is set up. The results show that the proposed circuit balances the HESS when the DC-DC converter works, which verifies the theoretical analysis.