Transmitter Side Voltage Based Mutual Inductances and Load Tracking for Two-Transmitter LCC-S Compensated Wireless Power Transfer Systems

Tracking mutual inductances and load is essential for monitoring and control of wireless power transfer (WPT) systems. This paper proposes an estimation method to identify the mutual inductances and load for a two-transmitter-one-receiver (2TX-1RX) LCC-S compensated WPT system. It only needs voltage measurements at the transmitter side, without requiring current sensors and information from the receiver side. The paper first proposes a mathematical model that systematically describes the physical laws at the fundamental frequency and the third harmonic of the WPT system, where the rectifier and the load at the receiver side are equivalently modeled as a square wave source. The paper also rigorously derives the reason why mutual inductances and load cannot be estimated simultaneously at the resonant frequency using conventional equivalent resistor load model. In comparison, the proposed methodology ensures unique solutions of estimated parameters. Afterward, a state estimation method is applied to solve the unknown states of the system including mutual inductances and load information. Further controls such as maximum efficiency and constant output voltage/current controls can be implemented based on accurate tracking of system parameters using the transmitter side information only. Hardware experiments on a prototype 2TX-1RX LCC-S WPT system validate the effectiveness of the proposed method.