A Frequency Control Method for Regulating Wireless Power Transfer System with Wide Coupling and Load Ranges

As a promising charging technology, wireless power transfer (WPT) has been increasingly applied for electric vehicles (EV). Among the various topologies, the Series-Series (SS) topology is widely used due to its simple structure and high efficiency. However, addressing coil misalignment and load variations to deliver the required power with a simple method remains a challenge. In this article, the output voltage and output current curves of the WPT system are derived with the Thevenin equivalent circuit, indicating that within a specific frequency range, the curves change monotonically and zero voltage switching (ZVS) can also be achieved. Based on this finding, a frequency control method is proposed to achieve the desired power in both constant current (CC) and constant voltage (CV) mode by continuously and monotonically adjusting the system operating frequency. The constraints of this method have also been identified. Based on this, the system parameters were designed. Finally, a 3.3 kW simulation model is designed to verify the theory, covering a coupling coefficient range of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$[0.1,0.3$</tex>] and a load range of [24.24 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\Omega, 242.4 \Omega$</tex>.