An Accurate Modeling and Suppression Method for Current Imbalance in Dual-Receiver WPT Systems for Low-Voltage and High-Current Applications

Wireless power transfer (WPT) technology is a convenient charging method for automated guided vehicles (AGVs) without manual operation. To satisfy the low-voltage and high-current requirement for charging AGVs, the dual-receiver WPT system is used to improve the current capacity and to decrease the current stress in coils and devices. However, the dual-receiver system suffers from current imbalance or even current clamping issues when the coupler misalignment occurs with different mutual inductances on each receiver channel. The current imbalance defeats the original purpose of the design and causes receiver overload and device overstress. Therefore, this article presents an accurate model to describe the dual-receiver currents under coupler misalignment. The key factors and reason for the current imbalance are studied accordingly and then guide the design of the coupler and the circuit of the dual-receiver system. Moreover, according to the practical demand, a comprehensive control strategy is proposed to achieve current balance and constant voltage output simultaneously. Finally, an experimental prototype of 48 V/30 A is built to validate the proposed method. The experimental results show that with the control strategy, the current difference can be decreased from 29.31 to 0.26 A under various misalignment conditions, while the efficiency increases by 1.8%.