A Simple and Fast Online Parameter Estimation Method for Wireless Power Transfer Systems Considering Compensation Capacitance Deviations

Accurate online parameter estimation is crucial for effective system control, monitoring and maintenance for wireless power transfer (WPT) systems. However, unavoidable and unpredictable deviations in compensation capacitances, caused by factors such as tolerance, environmental conditions, and aging, complicate the parameter estimation process. To address this issue, this paper proposes a simple and fast online parameter estimation method based on a frequency adjustment strategy. This method alternates between secondary resonance and non-resonance states, allowing simultaneous estimation of mutual inductance, load resistance, and compensation capacitances using only additional two voltage sensors and three current sensors. Only DC and RMS values are utilized, without the need for high-bandwidth communication, switches or complex algorithms. Experiments demonstrated that the method could simultaneously estimate multiple parameters over a wide power range, with errors below 10% in 7.0 ms. The maximum average errors were 7.0% for mutual inductance, 6.7% for load resistance, and 2.8% for compensation capacitances when combined with efficiency optimization strategies. Furthermore, the frequency adjustment selection principles were outlined. Both analysis and experiments confirmed that the brief detuning duration and a 2% frequency deviation had minimal impacts on WPT systems, thus enabling a cost-effective and fast solution for practical applications.