DESIGN OF A SOFT SWITCHING BIDIRECTIONAL DC-DC POWER CONVERTER FOR ULTRACAPACITOR-BATTERY INTERFACES |
Z. W. WU, Z. L. ZHANG, C. L. YIN, Z. ZHAO |
Shanghai Jiao Tong University |
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ABSTRACT |
One solution to the low specific power of hybrid electric vehicular batteries is a hybrid energy storage system (HESS) that takes advantage of the high specific power performance of ultra-capacitors. The design of a type of zero current transition (ZCT) soft switching bidirectional direct current-direct current (DC-DC) power converter that can be used as an ultra-capacitor-battery interface in an active parallel schema of a HESS is described. The circuit operation of the ZCT DC-DC power converter is depicted in detail. The HESS controller is designed as a two-layered hierarchical control structure: the first layer is responsible for working mode control of the HESS, and the second layer is responsible for DC-DC power converter control in which a fuzzy logic PID algorithmis employed. Simulation results indicate that this design is a potential solution to the problem of the low specific power of batteries, especially for regenerative braking and electric motor assist. The proposed active parallel schema with ZCT exhibits a significant advantage in power and energy decoupling. HESS with ZCT achieves better efficiency compared to the battery only operation. The experimental results validates the idea that the ultra-capacitor cooperates with the battery in acceleration mode. |
Key Words:
Hybrid energy storage system, Zero current transition soft switching, Bidirectional DC-DC, Hybrid electric vehicle, Fuzzy logic PID |
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