Accurate Transfer-Power Measurement for Wireless Charging of Electric Vehicles Under Misalignment

Transfer-power measurement (TPM) provides fair metering for wireless power transfer (WPT) in electric vehicles (EVs). TPM employs sense coils between the transmitter coils (Tx) and receiver coils (Rx) to estimate the transferred power from the magnetic field. Two sense coils are enough for power estimation when the transmitter and receiver positions are always fixed. However, misalignment of coils leads to errors which can be corrected by using more sense coils. In this paper, TPM under misalignment using multiple sense coils is introduced, which give implicit information about the misalignment. A quadratic approximation of coupling coefficients under misalignment is used to correct the errors. Numerical models from precise theory confirm the fidelity of the approximation and experimental results concur.