Wireless Charging of Large-Scale Energy Storage Systems: A Hybridized Ad-Hoc Approach for High Efficiency

This article presents a solution to the challenges faced by wireless power transfer (WPT)-based equalizers in supporting high-voltage large-scale energy storage systems while improving efficiency. The proposed solution is an efficient hybridized ad-hoc wireless charger that balances cascaded energy storage modules without imposing high current stress on each cell. Unlike multiple-coil solutions, the proposed solution requires only one receiving coil, eliminating the impact of parameter inconsistency. An algorithm is also proposed to switch the balancing and charging modes, reducing conduction loss compared to conventional WPT-based equalizers with only a balancing mode. The proposed algorithm enables ad-hoc balancing for targeted cells instead of balancing the entire cell string at all times. A scaled-down prototype with 12 cells was fabricated, and experimental results show that the proposed system achieves both charging and balancing functions for the energy storage system. During the balancing process, the system can achieve up to 76.1% efficiency for 25-W balancing, whereas, during the charging process, it can achieve up to 88.6% efficiency for 65-W charging. The proposed WPT-based equalizer provides an efficient hybridized ad-hoc wireless charging/balancing approach that supports large-scale energy storage systems.