Search

In this article, a front-end monitoring method is proposed to estimate the coupling coefficient and receiver resonant frequency in the series–series compensated wireless power transfer systems. The proposal requires no prior knowledge of the receiver circuit parameters, such as the self-inductance of the coil, compensated capacitor, load resistance, and resonant frequency. Hence, it is suitable for the development of universal wireless charging systems and is immune against parameter tolerances and aging effects. It uses a sensing coil, which is decoupled from the transmitter coil but coupled with the receiver coil, to detect the phase information of the current on the receiver side. Only one zero-crossing sensor is required to detect the voltage information in the sensing coil. Two frequency sweeping processes are included to find the frequency points where the ac output voltage is in phase or out of phase with the ac input voltage. In the experiment, the estimation errors are less than 4.91% for the coupling coefficients and 1.33% for the receiver resonant frequencies. In addition, the estimation is extremely fast. The estimation time is within 5–9 ms.

This article proposes a fast and accurate front-end monitoring method to estimate the coupling coefficient and receiver resonant frequency of wireless power transfer (WPT) systems. The proposed method is developed for universal WPT systems with a series-compensated transmitter. The receiver parameters can be unknown and different from those on the transmitter side. This method is applicable to a range of receivers with first- or second-order compensation (i.e., series, parallel, and none-compensation). It can be extended to the systems with magnetic shielding, and has a strong immunity to the harmonics. Furthermore, a hardware-based identification approach is proposed for receiver compensation without any additional cost. The detection algorithms are analyzed in detail. The proposed scheme requires one additional phase detection sensor of the transmitter current. The zero-phase-angle frequencies of the WPT systems can be determined by fast frequency-sweeping processes with the receiver's active rectifier kept momentarily either short-circuited or open-circuited. Experimental results have been obtained to verify the proposed method, which can accurately estimate both coupling coefficients and receiver resonant frequencies within 2.5–8 ms.

This letter proposes a conditional pulse density modulation (PDM) method for inductive power transfer (IPT) systems, which can automatically adapt the generated output patterns to effectively suppress current/power ripples. The proposed conditional PDM introduces a sending current limitation as an additional condition to skip pulses, which modifies the output patterns generated by conventional delta-sigma-based PDM. Thus, the PDM pulse pattern is continuously adapted to attenuate any excited current/power oscillations. The presented modulator is simple to implement and well-suited for IPT systems with poorly damped constant voltage load characteristics. Simulations and experiments demonstrate the effectiveness of the proposed modulation method.

Nonpolarized and polarized coils are utilized in an electric vehicles wireless charging system. These coils are decoupled from each other at the central position, leading to interoperability issues. This letter proposes a new decoupling method and a quadrupole receiving coil with series-connected diode rectifiers for interoperability purposes. Decoupling windings are added to achieve decoupling of the four receiving poles. The total mutual inductance between the transmitting coil and the quadrupole receiving coil is the summation of the absolute values of the mutual inductances between the transmitting coil and the four receiving poles. In this way, the proposed quadrupole coil can be tolerant with not only the nonpolarized transmitting coil, but also with the polarized transmitting coils along two perpendicular directions. The experimental results confirm that a large coupling and efficient power transfer can be achieved with the nonpolarized coil and the polarized coil placed at two perpendicular directions with good misalignment tolerance.