Efficiency Optimization Method for Cascaded Two-Stage Boost Converter

Abstract

A method of optimal intermediate voltage tracking (OIVT) is proposed in this paper to improve efficiency for the cascade boost converter. The intermediate voltage can be adjusted by regulating the duty cycle of front stage and rear stage converters. To improve the control speed of the algorithm, the intermediate voltage range is determined by calculating the overall system loss. In addition, with the input-output relationship maintained, the root-mean-square (rms) current of the intermediate capacitor can be reduced by changing the phase difference between front and rear side PWM signals. On this basis, a method of optimal phase-shift angle tracking (OPAT) is proposed to further improve efficiency for the system and extend service life for the capacitor through relatively simple implantation. Besides, the proposed OIVT and OPAT method is applicable to other cascade topologies. A 1-KW prototype is constructed in the laboratory to verify the proposed control method. As confirmed by the experimental results, the maximum efficiency reaches 95.23% when the proposed control method is adopted, which is 2% higher than under the uncontrolled condition. It is demonstrated that the proposed OIVT and OPAT method is effective in improving efficiency for the system without needing any additional components.

Keywords

• Capacitor current ripple
• dc/dc power conversion
• optimal phase-shift angle tracking
• optimal intermediate voltage tracking
• two-stage converters