Suppression of Receiver Harmonic Currents in Wireless Power Transfer Systems

Harmonic currents in a receiver in wireless power transfer (WPT) systems can degrade performance of the receiver device by corrupting the DC power plane. The DC plane at the receiver serves as a constant reference that allows for dependent, sensitive electronics to operate with acceptable precision. However, if that reference is corrupted by noise, then the functions of the system, such as sensing and wireless communication, can degrade significantly. To reduce the harmonic current content in the receiver, and thereby improve the DC supply constancy, the optimal arbitrary voltage transmitter excitation is derived. To physically generate the derived arbitrary voltage, the signal is converted to a multilevel voltage using a phase-shifted carrier modulation. This multilevel voltage is then realized via the design of a full-bridge flying capacitor multilevel inverter and circuit simulations demonstrated the reduction of the harmonic currents in the receiver. By comparison to using a square-wave input voltage, circuit simulations demonstrate that a 5-level multilevel inverter reduces the total harmonic distortion (THD) of the received current from 6.79 % to 0.69 %, effectively reducing the harmonic currents in the receiver by 90 %.