## 1 Introduction  
The emergence of inductive power transfer (IPT) technology using magnetic-field coupling has provided a feasible alternative to battery charging based on physical connections. Owing to the advantages of isolation, high transfer efficiencies, and convenience, IPT has potential for various battery-charging applications, such as low-power portable electronic devices [1], high-power electric vehicles (EVs) [2, 3], and automated guided vehicles [4]. Additionally, IPT technology could be applied to charge underwater equipment and biomedical implants, in addition to improving the vehicle-to-grid connection success rate. As shown in Figure 1, a typical IPT system consists of a power supply, a power factor correction (PFC) converter, an inverter, a compensation resonant network, a loosely coupled transformer (LCT), a rectifier, and a battery load. The modules in the IPT system have different functions. The PFC converter is mainly responsible for providing different levels of DC-link voltage. The inverter converts DC into high-frequency AC and transmits it to the resonant network on the primary side. The AC generates a high-frequency magnetic field through the transmitting coil and transmits it to the aligned receiver coil through a large air gap with the primary and secondary side compensation networks, which are used to decrease each coil's reactive current. In the coupled magnetic field, the alignment of the coils directly affects the system's performance. [PERSON] et al. [5] proposed a mesh-based coil precise positioning strategy using the voltage principle induced by the detection coil installed on the secondary coil. This system could be applied in automatic parking scenariosto help align the coils and improve electrical transmission performance. Finally, the battery is charged after rectification and filtering. Generally, the battery's main charging modes are the constant current (CC) and constant voltage (CV) modes [6], which form the classic charging curves shown in Figure 2. As shown, the battery is charged by an initial constant charging current \(I_{\text{b}}\). However, to avoid battery overcharge, when the charging voltage reaches the preset threshold voltage \(U_{\text{b}}\), the IPT charger switches to the CV mode, which helps extend battery life. The battery's equivalent resistance exhibits a nonlinear trend, making it difficult for the IPT charging system to obtain high-efficiency CC/CV outputs. To design a stable, reliable, and load-independent IPT charger with CC and CV outputs, researchers have proposed four types of control schemes: frequency-modulation (FM) control, frequency-switching control, phase-shift (PS) control, and additional DC/DC converters. [PERSON] et al. [7] proposed an IPT system with high-efficiency CC/CV output capabilities based on the FM control method. However, [PERSON] et al. [8] pointed out that the frequency-division phenomenon caused by the wide range of frequency changes detunes the system. Additionally, the large amount of generated reactive power reduces the system's efficiency. Moreover, [PERSON] et al. [9] analyzed that the frequency bifurcation phenomenon can cause stability problems; however, if a controllable operation is achieved in the bifurcation region, the system's power transfer capability could be significantly improved. [PERSON] et al. [10] proposed an optimal frequency tracking method to ensure that the link operates at the resonant point and maximizes the output voltage when frequency splitting phenomena occur around the resonant frequency of 5 MHz. [PERSON] et al. [11] proposed a frequency-switching control scheme that can realize the CC/CV charging mode under the ZPA condition without causing a frequency-division phenomenon and without any additional switches. However, this method is realized in a wide frequency range, increasing the design difficulty and reducing its freedom because the CV mode's output characteristics are limited  
Figure 1: A typical IPT EV charging system. Figure 2: A battery’s typical charging curve.