Dynamic Response Improvements of Parallel-Connected Bidirectional DC-DC Converters for Electrical Drive Powered by Low-Voltage Battery Employing Optimized Feedforward Control

Parallel-connected modular current-fed bidirectional dc-dc converters are used for the AC motor drive system powered by batteries with low voltage and wide voltage range. The input current ripple can be reduced significantly by employing interleaving technology not only for individual module but also for all the modules. A current sharing control strategy is applied for the constituent modules. Double pulse width modulation plus double phase shifted control with equal duty cycles for one module can minimize the circulation loss and avoid nonactive power issue. Factors affecting dynamic performance are investigated based on the small-signal modeling. The leakage inductance value is optimized in view of system reliability and better dynamic performance. Besides, to improve the dynamic performance further, feedforward control employing optimized feedforward coefficient based on the small-signal analysis is implemented. A 4-kw prototype composed of two bidirectional dc-dc converters is built to verify the effectiveness for the proposed control strategy in AC motor drive application with fast regenerative braking.