## 1 Introduction  
Wireless power transfer has gained popularity over the years as this technology can charge electric vehicles (EVs) without requiring a power cable and a plug-in connector. In recent years, inductive power transfer by a DC/DC resonant converter has become an effective wireless charging method [1]. For EV wireless charging applications, the considerable variation of wireless transformer parameters exists practically due to the significant magnetic coupling factor change caused by air-gap distance variation, the misalignment between the transmitter and the receiver pads, and the receiver coil parameter vehicle-to-vehicle variation. For the basic series-series (S-S), series-parallel (S-P), parallel-series (P-S), and parallel-parallel (P-P) resonant circuit topologies, the resonant frequency is sensitive to the magnetic coupling factor variation and the receiver coil parameter variation. The high-order LCC resonant circuit is a more appealing topology for its robustness to the resonant circuit parameter variation and battery operation condition variation [2; 3; 4]. The resonant frequency selection is an important design decision for a wireless charging system. High resonant frequency improves the magnetic coupling and reduces the size of the wireless charging transformer. Therefore, increased resonant frequency reduces winding loss, core loss, and shield loss. The cost for high frequency is increased power device switching loss [5]. SiC MOSFET in the market's 600 V-1700 V voltage range opens the opportunity to implement high resonant frequency for EV wireless charging systems. Compared to SI MOSFET devices, SIC MOSFET has the advantage of much smaller and thermal-stable On-resistance Rds, which leads to low conduction loss. The intrinsic fast diode in SIC MOSFET has a much lower reverse recovery charge (Qrr) (low switching-off loss). SIC MOSFET is an ideal choice for wireless charging DC/DC resonant converter, which runs at hard-switching control with acceptable power device loss in low current at CV battery charging mode [5]. The switching loss of Sic MOSFET is estimated to reduce to around 50% with ZVS switching. The ZVS switching can be realized by introducing a phase shift between inverter/rectifier AC voltage and current so that the turn-off current at MOSFET switching ON transition is large enough to discharge the MOSFETs junction capacitors within dead time [6; 7]. For a conventional unidirectional wireless charging system, the battery current or voltage feedback control is implemented in the transmitter side high-frequency DC/AC inverter, and the receiver side AC/DC converter is an uncontrolled diode rectifier bridge. The loss distribution of a unidirectional 8 kW wireless charging MOSFET DC/DC LCC resonant converter is estimated as 52.3% from transmitter and receiver coils, 16.7% from LCC compensation network, 11.9% from power MOSFETs, 16.8% from rectifier diodes, and 2.2% from output filter [2]. Similar power loss distributions are reported in [8] in CC mode charging operation. For wireless charging systems, the loosely coupled transmitter and receiver coils dissipate most of the power loss because of a relatively larger resonant current [2; 8]. In LCC resonant compensation parameter design calculation, inverter AC circuit zero-phase-angle (ZPA) constraint is imposed to minimize reactive power flow into AC resonant circuit and maximize LCC resonant circuit efficiency [2; 9; 10; 11] The resonant compensation circuit design with inverter ZPA operation constraint is critical for achieving high-efficiency operation of the wireless charger at CC charging mode with low battery equivalent resistance. However, resonate circuit efficiency significantly degrades in CV charging mode operation when battery equivalent load resistance is significantly increased [12; 13; 14]. Intensive research efforts are published to minimize the efficiency degradation caused by battery equivalent resistance variation in CV battery charging mode.