Multivariate Optimization Using PWM-Controlled Switched Capacitors for Cross-Coupling Compensation in Multiple Receiver WPT

The coupling between receiver (RX) coils i.e., cross-coupling is one of the main challenges in multiple-RX wireless power transfer (WPT). Previous studies showed that the cross-coupling can be compensated by adjusting the additional reactances of each RX to their optimal values. However, the phase difference between the transmitter (TX) and RX currents is required in previous control methods, which remains to be a practical issue. This article converts the problem of cross-coupling compensation to a multivariate optimization problem and proposes a unique control method for pulsewidth-modulation-controlled switched capacitors. The proposed method compensates for the cross-coupling by searching for the maximum input power point with the switched capacitors, thus eliminating the need to directly compare the TX and RX current phases. The experimental results using two and three RXs show that the proposed method can effectively compensate for the cross-coupling and mitigate the deviation of the output power from the desired value.