A Pulse Density Modulation Based Receiver Reactance Identification Method for Wireless Power Transfer System

Tuning the receiver to match the resonant frequency with the working frequency plays an important role in improving the efficiency. One of the crucial steps in tuning is to determine the value or degree of detuning. In order to obtain the receiver reactance used to determine the detuning value, this article proposes a pulse density modulation (PDM)-based receiver reactance identification method. The parameter identification is performed as follows: implementing PDM technology on the active single-phase rectifier (ASPR) to bring in interharmonics and through Fast Fourier Transformation and least-square approximation, values of inductor and capacitor of the receiver can be identified. This estimation method only requires the magnitudes of voltage and current into ASPR for estimation. No extra hardware, no need to synchronize with the transmitter. In the experimental verification, four cases of resonant, inductive, and capacitive receivers are designed. Results show the maximum relative errors for estimation are within 5%, based on which the ASPR can tune the receiver as resonant. The situation that parameter deviates from the nominal value is also considered, even with deviations of mutual inductance and transmitter-side reactance, the estimation accuracy of receiver-side reactance is still at an average level.