Self-Balancing Virtual Impedance for Multiple-Pickup Wireless Power Transfer

Being different from one-to-one power transmission, the multiple-pickup wireless power transfer (WPT) system should take into account the large-scale variation of the equivalent system impedance due to the varying number of loads, cross-coupled pickup coils, multiple-channel power control, etc., which inevitably results in the active regulation or passive shifting of the operating frequency and thus significantly deteriorates the transmission performance. Accordingly, this article proposes and implements an autonomous current compensation scheme, namely the self-balancing virtual impedance, which can be taken as an impedance buffer to ensure the resonant state for the expected operating frequency. The proposed scheme allows for an enhanced primary exciting current and transmission power in multiple-pickup WPT system, even under the consideration of the cross-coupling effect. Simulated and experimental results are both given to verify the feasibility of the proposed method. In the experiment, the primary exciting current can improve about 11.6%, meanwhile, the total load power boost about 7% under the three-pickup condition with the dc-load efficiency of 76.9%.