With the number of electric vehicles (EVs) on the rise, there is a need for an adequate charging infrastructure to serve these vehicles. The emerging extreme fast charging (XFC) technology has the potential to provide a refueling experience similar to that of gasoline vehicles. In this paper, we review the state-of-the-art EV charging infrastructure, and focus on the XFC technology which will be necessary to support current and future EV refueling needs. We present the design considerations of the XFC stations, and review the typical power electronics converter topologies suitable to deliver XFC. We consider the benefits of using the solid-state transformers (SSTs) in XFC stations to replace the conventional line-frequency transformers and further provide a comprehensive review of medium voltage SST designs for the XFC application.

Wireless charging systems are foreseen as an effective solution to improve the convenience and safety of conventional conductive chargers. As this technology has matured, recent broad applications of wireless chargers to electrified transportation have indicated a trend toward higher power, power density, modularity, as well as scalability of designs. In this paper, commercial systems and laboratory prototypes are reviewed, focusing mostly on the advances in high-power wireless charging systems. The recent endeavors in magnetic pad designs, compensation networks, power electronics converters, control strategies, and communication protocols are illustrated. Both stationary and dynamic (in-motion) wireless charging systems are discussed, and critical differences in their designs and applications are emphasized. On that basis, the comparison among different solutions and design considerations are summarized to present the essential elements and technology roadmap that will be necessary to support large-scale deployment of high-power wireless charging systems. The review is concluded with the discussion of several fundamental challenges and prospects of high-power wireless power transfer (WPT) systems. Foreseen challenges include utilization of advanced materials, electric and electromagnetic field measurement and mitigation, customization, communications, power metering, and cybersecurity.

The efficiency of bidirectional inductive power transfer (BIPT) systems is strongly dependent on the load. Besides, soft switching operation of power switches is critical to high frequency converter in BIPT systems. In this paper, a triple-phase-shift (TPS) control strategy is proposed to achieve load matching while realizing zero voltage switching (ZVS) for all power switches within entire power range. The load matching condition of bidirectional inductive power transfer system with double-sided LCC compensation network is analyzed. And a dual side phase shift control is proposed to adjust power flow while realizing load matching. To realize ZVS operation, the third phase shift between primary and secondary side is introduced as an extra control variable. A time domain model of double-sided LCC compensation network is established to analyze the ZVS range. With the proposed TPS control, wide ZVS operation range of system can be achieved while maintaining load matching. At last, a scale down prototype of 1kW BIPT system is developed. The experimental results show good agreement with theoretical analysis, all switches realize ZVS within entire power range and a peak efficiency of 94.83% is achieved.

Wireless power transfer (WPT) system usually suffers from wide range of coupling condition. This causes deep impact on the transferred power level, which further limits the mobility of receiver. In this paper, a dual-side-detuned series-series (SS) compensation method is proposed to provide stable power transfer over wide geometric area. The primary and secondary tuning methods are classified into three categories, respectively, namely fully tuned, inductively tuned, and capacitively tuned. Then, the general power transfer characteristic against coupling factor is identified and it is found that the primary inductively and secondary capacitively tuned (PISC) system is advantageous over other candidates in performance, especially the resistance to variation of coupling factor. Compared to conventional fully tuned SS system, the PISC-type WPT system provides much wider stable power transfer region, which enables higher mobility for the receiver side. The design consideration and principle of the detuned resonant tank is developed, based on which the iteration approach is proposed to guide parameter design procedure. Finally, the validity of the proposed dual-side-detuned SS topology is experimentally verified. Under coupling variation from 0.08 to 0.2, the power transfer is maintained above 80% of its nominal power level with agreeable efficiency.

In Inductive power transfer (IPT) systems, zero-voltage-switching (ZVS) operation within wide power range is an urgent requirement to improve system efficiency and reduce electromagnetic interference. The combination of phase shift (PS) control and variable frequency control is usually adopted to realize ZVS operation. However, in Inductor-Capacitor-Capacitor-Series (LCC-S) systems, the above-mentioned hybrid strategy cannot be used directly due to non-negligible harmonics, which result in detection difficulties or imprecise calculation of turn-off current. To solve this problem, this paper proposes an optimal variable frequency phase shift (VFPS) control strategy for LCC-S systems to realize ZVS operation within wide power range. The universal harmonic-considered time-domain model of LCC-S system is deduced, and thus the switching-moment current of power switches can be calculated accurately. Based on this value, an optimal working trajectory for ZVS operation with minimum frequency variation is presented. Finally, a 2.2kW IPT prototype is built up to verify the universality of the deduced model and the validity of the proposed optimal VFPS control. Compared with PS control and the VFPS control based on fundamental-harmonic-approximation method, the systems realizes ZVS operation under wide power range with efficiency increase of 2.6%-6.9% and 0.8%-8.8% respectively, and a peak efficiency of 96.4% is achieved.