A Current-Sharing Compensation Method for High-Power-Medium-Frequency Coils Composed of Multiple Branches Connected in Parallel

Abstract

In inductive power transfer (IPT) systems, the coils with paralleled multiple branches are commonly used in high power applications where the frequency range is between 20 and 90 kHz. The traditional compensation method takes multiple branches as a whole and the compensation capacitors are connected outside the coils, which suffers from current unbalance among multiple branches, but currently few researchers analyze it. Therefore, this article illustrates the current-unbalance mechanism and proposes a current-sharing compensation method for IPT coils. The current-unbalance characteristics of coils with paralleled multiple branches are illustrated to prove the current-sharing necessity. Then, based on the relation between the impedance of branch and current unbalance, a compensation capacitor with a specially designed value is connected in each branch, so that the current unbalance can be suppressed by the increased branch impedance. Besides, the cost, volume, and weight of IPT systems remain unchanged approximately. Finally, a 30-kW IPT prototype is built up to verify the availability of the proposed method, and the currents and temperatures of multiple branches are equally distributed within wide power range with this method.