Circulating current control method for inductive power transfer system
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Abstract:
Inductive power transfer (IPT)technology allows electrical energy to be transferred between two loosely coupled inductors over relatively large air gaps based on electromagnetic induction. In current-fed IPT systems,resonant capacitor voltage distortions and current spikes on the semiconductor switches are easily caused when switches isn’t switched at zero crossing point of resonant voltage. As a result,the EMI level of the system and the switching loss are increased and thus the system transmission stability and efficiency decrease. The article analyzes the production mechanism of circulating current in load resonant high frequency inverter and points out that the resonant frequency change is the real cause. By analyzing the characters of circulating current before and after the zero-crossing points of resonant voltage and relationship between switching frequency and resonant frequency,this paper proposes a method of real-time detection for the direction of circulating current,and regulating the switching frequency in accordance with resonant frequency dynamically to ensure the switching of switch tubes at the zero-crossing points of the resonant capacitor voltage,and thus to inhibit circulating current. An experiental system with the platform of FPGA is set up to verify the effectiveness of this control method.
