Voltage Control by Transmitter-Side Measurements for On-board Wireless EV Battery Charger

Abstract

Wireless charging for electric vehicles (EVs) requires a high precision control scheme to maintain desired charging voltage across the battery. The receiver-end voltage of an on-board charger can vary dramatically with the change in the mutual inductance developed in between the transmitter-end coil and the receiver-end coil. The receiver-end coil is set inside the electric vehicle, and therefore, accurate alignment between the transmitter-receiver coils is crucial for efficient charging. In this paper, strategy for a receiver-end charging voltage control for a wireless EV battery charger by measuring the transmitter-side voltage and current parameters has been proposed. Mathematical models to estimate the mutual inductance and the output voltages have been developed. The proposed strategy is able to estimate the mutual inductance between the two coils by utilizing the transmitter-side measurements and estimate the output voltage at the receiver end. The estimated voltage is then utilized in a closed-loop controller at the transmitter-side to control the output voltage at the desired level. The major contribution of this paper lies in the achievement of accurate voltage control of wireless EV charger, without physically accessing the measurement parameters inside the vehicle and thus ensuring efficient wireless charging, which is straight forward, does not rely on the sensors from the electric vehicle, and easy to implement. The efficacy of the proposed strategy is verified through simulation results in MATLAB/Simulink.