Secondary Side Voltage and Current Estimation of Wireless Power Transfer Systems

This article presents a secondary side voltage and current estimation method in the wireless power transfer (WPT) systems on the basis of load parameter identification. In the application of limited space and weight, it is difficult to arrange sensors to monitor the high-frequency voltages and currents in the WPT secondary side. Compared with the conventional methods, joint estimation of several secondary side voltages and currents is achieved in this article to monitor WPT electrical stress, based on only the RMS value of one primary side measured voltage. First, an equivalent circuit model of the WPT system with the dual-side LCC compensation networks and rectifier load is established. Then, T-type equivalent circuit of the coils and compensation capacitors is adopted to simplify the model. Moreover, the relationship between the RMS value of the primary side measured voltage and system equivalent load resistance is obtained and simplified for the load parameter identification. Furthermore, the secondary side voltage and current estimation method are proposed based on the identified system equivalent load resistance. Finally, a WPT prototype is developed and the experimental results indicate that the proposed method can achieve high estimation accuracy under the conditions of battery load voltage change, inverter phase-shift angle variation, and coil misalignment.