A Highly Scalable Integrated Voltage Equalizer Based on Parallel-Transformers for High-Voltage Energy Storage Systems

In a high-voltage energy storage system (HV-ESS), the voltage equalizer faces two challenges: 1) improving the extensibility and 2) reducing the number of switches. Therefore, an integrated voltage equalizer based on parallel transformers is proposed, which uses one mosfet to balance the HV-ESS. All the bottom-layer transformers (BLT) are paralleled, and the input voltages of BLTs are identical. Moreover, the top-layer transformer (TLT) drives parallel-BLTs, directly transforming balanced energy to each battery cell. Whatever the number of the BLT, the TLT uses one secondary winding to drive. Thus, the proposed voltage equalizer is highly scalable. The experimental results show that the proposed circuit effectively balances nine series-connected battery cells. It provides a highly scalable integrated voltage equalizer for the HV-ESS.