A Modularized Voltage Equalizer Based on Phase-Shift Modulation for Series-Connected Battery Strings

The modular design can effectively improve the circuit extensibility and control flexibility of equalizers for long series-connected battery strings. This article proposes a modular battery equalizer based on phase-shift modulation. The LC resonant converters with synchronous rectification are employed as the automatic cell-level equalizer to realize any-cells-to-any-cells (AC2AC) equalization and soft-switching operation, which enhances the balancing speed and efficiency. Different cell-level equalizers are connected with auxiliary windings. The fast equalization between modules is achieved by adjusting the phase shift of driving signals applying for the cell-level equalizers. A prototype with three modules, each consisting of three series cells, is built and tested. Experimental and comparative results confirm the validity and characteristics of the proposed modular equalizer.