Optimal frequency estimation for wireless power transfer systems with an active rectifier

Wireless power transfer (WPT) technology, renowned for its reliability and flexibility, is utilized in numerous fields. This article addresses the synchronization of the active rectifier in WPT systems. Traditional methods for synchronization, such as auxiliary coil-based techniques, current sampling approaches, and perturbation observation methods, often suffer from limitations such as communication delays and sensitivity to noise. Meanwhile, they also assume the switch frequency is known. To overcome these flaws, this article proposes a frequency estimation method based on the sampled values of the rectifier bridge's input current. The method accurately estimates the frequency and initial phase angle, thus improving the synchronization performance. Additionally, dynamic clock interpolation technology is introduced to improve synchronization accuracy by compensating for quantization errors in pulse width modulation frequency generation. Simulation and experimental results demonstrate that the proposed method enhances both synchronization performance and stability, even if the realistic frequency is unknown.