Frequency Domain Analysis of a Wireless Power Transfer System Operating in a Wide Load and Coupling Range Using Frequency Modulation of Inverter for Voltage Regulation

An accurate frequency domain analysis in the steady state has been introduced for a Wireless Power Transfer (WPT) system which maintains output voltage regulation by frequency modulation of inverter switches. The modelling has been shown for both continuous (CCM) and discontinuous (DCM) modes of operation considering harmonics on both sides of the resonant tank. This accurate analysis can be used for proper design and selection of system components such as the resonant capacitors, WPT coils and semiconductor devices. Two different characteristics of the system are identified based on the coupling coefficient between the transmitter and receiver coils and output load resistance range. Characteristic I, in which the inverter switches can be operated below the resonant frequency of the system to achieve zero-voltage switching (ZVS), is demonstrated in this paper for the first time. Experimental results on a 5W WPT system demonstrate the two different characteristics of the system and validate the accuracy of the analysis presented in this paper.