Abstract
This paper proposes an algorithm for the extraction of primary-side first harmonic voltage and current components for inductive wireless power transfer (WPT) links by employing quadrature demodulation. Such information allows for the accurate estimation of corresponding receiver-side components and hence permits the monitoring of the output voltage and resistance necessary for protection and/or control without using either sensors or feedback communication. It is shown that precision estimation is held as long as the parameter values of the system are known and the phasor-domain equivalent circuit is valid (i.e., in continuous conduction mode). On the other hand, upon light load operation (i.e., in discontinuous conduction mode), the proposed technique may still be employed if suitable nonlinear correction is employed. The methodology is applied to a 400 V, 1 kW inductive WPT link operating at a load-independent-voltage-output frequency and is well-verified both by simulations and experiments.
Highlights
The wireless power transfer (WPT) system has the potential to become a practical solution for power delivery in the future due to its flexibility, movability, and cordless nature
With PO denoting the power absorbed by RO, PO,B signifying the power level corresponding to the diode rectifier operation on the bound between conduction mode (CCM) and discontinuous current mode (DCM), PO,MIN indicating the minimum allowed loading of the inductive WPT link [36] and
When parasitics are brought into the model, with the aim of improving the accuracy of the output voltage and resistance estimation with the aim of improving the accuracy of the output voltage resistance estimation the results generally look much more similar—see
Summary
The WPT system has the potential to become a practical solution for power delivery in the future due to its flexibility, movability, and cordless nature. In order to overcome this issue, the paper suggests utilizing the quadrature demodulation (QD) algorithm [27], typically employed in communication systems engineering This technique accurately reveals the Cartesian components of first harmonic phasors while taking advantage of the fact that non-sinusoidal periodic signal harmonics are orthogonal. It must be emphasized that fundamental harmonic-based approximations are insufficient for a WPT link operating under light loads [32] This is due to the fact that when the receiving-side diode rectifier operates in discontinuous current mode (DCM), the harmonic content of primary and secondary currents rises significantly [33], and the relation between the secondary-side AC variables of the equivalent phasor-domain circuit and the output. In order to overcome this obstacle, it is proposed to utilize a nonlinear correction function that allows for the adjustment of the output of the QD-assisted phasor-domain solution to yield an accurate estimation of WPT output voltage and load resistance under light loading.
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