Power-Matched Harmonic Current Analysis of a Detuned S–S Compensated Wireless Power Transfer System Across CCM and DCM Operation

This paper presents a power-matched third-harmonic current analysis for a detuned series–series (S–S) compensated wireless power transfer (WPT) system operating across continuous conduction mode (CCM) and discontinuous conduction mode (DCM). In practical S–S WPT systems, the transmitter-side resonant frequency is often intentionally detuned from the switching frequency to satisfy the desired switching condition, which leaves a residual transmitter reactance and changes the harmonic current behavior. In addition, the rectifier conduction mode affects the receiver-side voltage waveform and its harmonic components. To analyze this behavior, the fundamental power-transfer path is modeled using the equivalent rectifier input resistance, whereas the harmonic path is formulated using the inverter and rectifier harmonic voltage sources coupled through the transmitter and receiver resonant tanks. Although the formulation is applicable to arbitrary odd harmonics, the third-harmonic current is selected as the main EMI-oriented comparison quantity because it is the dominant low-order harmonic in the considered operating range. Simulation and experimental results show that output power alone is not sufficient to determine the harmonic current level. When power-matched operating points exist across the CCM/DCM boundary, the CCM-side load point is generally more favorable, especially from the receiver-side third-harmonic viewpoint. When both power-matched points are in DCM, the load point closer to the CCM/DCM boundary is generally more favorable than the deeper DCM point.