Reactive Balancing Circuit for Paralleled Battery Modules Employing Dynamic Capacitance Modulation

Battery systems consist of multiple parallel-connected modules to ensure reliability and expand the capacity. However, inconsistency between battery modules causes non-uniform current distribution among branches and results in over-charge or over-discharge issue. To overcome the inconsistency issue, conventional switch-based sequencing or dynamic resistance equalizer regulates the branch current, but it causes increased power losses both in the circuit and inside the battery. This paper proposes a dynamic capacitance modulation scheme that balances the module voltages in the idle mode and regulates the branch currents during the non-idle mode in an efficient way. The operation principle is discussed theoretically and verified by hardware-in-the-loop tests for 4 parallel-connected battery modules. The results show that SOCs are equalized within 1% in the idle mode and the inconsistency is eliminated during the non-idle mode.