Wireless Power Transfer (WPT) technology is widely used in many fields due to its secure, flexible, and convenient characteristics. However, the inherent uncertainty of the coupling area between the receiving coil and the transmitting coil has become an obstacle to its further development. Therefore, applying coupled mode theory to analyze wireless power transfer systems that satisfy Parity-Time (PT) symmetry characteristics is a feasible perspective for understanding the energy transmission process. Coupled mode theory analyzes the coupling coefficient range where it can achieve constant load power and system transmission efficiency with changing the coupling area of the transmitting and receiving coils. In general, a self-excited oscillation control circuit is used to generate a two-level inverter square wave voltage. Correspondingly, it leads to insufficient utilization of DC voltage and Total Harmonic Distortion (THD). Therefore, the transistors have to suffer high voltage stress and loss. Besides, the delay from the sampling circuit cannot be adaptively compensated. More unfortunately, the self-excited oscillation control with a fixed 50% duty cycle cannot be regulated. Hence, a three-level inverter voltage control scheme based on digital control is proposed in this article, which can not only improve the utilization of DC voltage and reduce switching loss and conduction loss, but also modulate duty cycle and compensate for sampling circuit delay using digital control.