10.2 A digitally controlled 94.8-peak-efficiency hybrid switched-capacitor converter for bidirectional balancing and impedance-based diagnostics of lithium-ion battery arrays

摘要

With the growing adoption of electrified transportation and need for active storage in the electrical grid, electrochemical energy storage has become increasingly important. Past electrochemical management systems have suffered from low efficiency, limited functionality, and extreme cost sensitivity in storage applications [1]. Most battery management systems used for state-of-charge (SOC) equalization in large arrays use resistive shunts, which have low efficiency and lack bidirectionality. Efficient solutions are known, but have not been widely adopted in part due to the size and cost of magnetic components [2]. Resonant/hybrid switched-capacitor (SC) approaches are particularly attractive for electrochemical balancing/equalization, as the voltage ratio between series-connected cells or modules is typically 1∶1 with only minor variation due to cell impedance and state-of-charge (SOC) levels. Compared to pure SC approaches, they can achieve higher efficiency due to soft-charging and expanded capabilities for variable regulation. Compared to traditional buck-boost converters, the needed inductor volume can be 10 to 100× lower due to the reduced volt-second product (flux linkage) provided by the SC stage [3].