An Equalization Current Ripple Cancellation (ECRC) Converter-Based Centralized Equalization System for Series-Connected Battery Strings

Battery equalization management is a key technology to ensure the high-performance and safe operation of electrified transportation such as electric vehicles and electric aircraft. In this article, an equalization current ripple cancellation (ECRC) converter for centralized equalization system is presented. Compared with traditional methods, the ECRC converter-based equalization system achieves a zero-ripple equalization current, so that the unfavorable influence of larger current pulsation on battery cells is eliminated. Meanwhile, under a phase-shifted PWM modulation strategy, the ECRC converter not only implements zero-voltage switching (ZVS) of all switches to reduce switching loss, but also decreases the peak current of the transformer to reduce transformer loss, so that the efficiency of the equalization system is significantly improved. Besides, the value of each power element in the converter is comparatively small, which is conducive to improving the power density of the centralized equalization system. To confirm the theory analysis, an experimental prototype based on a battery string containing 13 cells is built for experimental verification, and a systematic comparison is implemented with existing centralized equalization methods. The experimental and comparison results verify the design of the proposed equalization system and reflect the obvious performance improvement over traditional methods.