In the application of rail transit vehicles, when using typical wireless power transfer (WPT) systems with series–series (SS) compensation supply power for supercapacitors, the output current is in an approximately inverse relationship with the duty cycle in a wide range. This renders the typical buck circuit control inappropriate. In order to help resolve the above issues, this paper designs inductor/capacitor/capacitor (LCC) compensation with new compensation parameters, which can achieve an adjustable quasi-constant voltage from the input of the inverter to the output of the rectifier. In addition, the two-port network method is used to analyze the resonant compensation circuit. The analysis shows that LCC compensation is more suitable for the WPT system using the supercapacitor as the energy storage device. In the case of LCC compensation topology combined with the charging characteristics of the supercapacitor, an efficient charging strategy is designed, namely first constant current charging, followed by constant power charging. Based on the analysis of LCC compensation, the system has an optimal load, by which the system works at the maximum efficiency point. Combined with the characteristics of the constant voltage output, the system can maintain high efficiency in the constant power stage by making constant output power the same as the optimal power point. Finally, the above design is verified through experiments.

Dynamic wireless power transfer (DWPT) can solve the limitation of battery capacity of electric vehicles, and has a good application prospect. In order to solve the problem of weak coupling power supply in a DWPT system with segmented coil mode, an improved real-time strong coupling coil arrangement mode is proposed in this paper. First, the characteristics of the typical coil arrangement mode is analyzed by establishing a DWPT model, in which the mutual inductance decreases sharply in a certain range. In order to ensure the stability of mutual inductance, an improved long receiving coil arrangement mode is proposed, and its advantage of the low coil cost is analyzed theoretically. Further, the optimal process of the improved coil mode is designed based on the genetic algorithm, and an application case of the electric bus is given. Finally, the feasibility of the coil design process is verified by simulation, and the performance advantages of the proposed scheme are verified by a 30 kW WPT platform.

Supercapacitors (SCs) are widely used as energy storage devices in many practical applications of wireless power transfer. However, the modeling and analysis of a wireless power transfer system are seldom based on SC load; thus, the effects of the charging process on the wireless power transfer system cannot be analyzed clearly. In this paper, a variable-resistance-based method is proposed for the modeling and analysis of the process of constant current charging. First, how to make an SC equivalent in variable resistance is described, and the relationship between SC and variable resistance is considered. Next, the charging process, including charging current, voltage, power and transfer efficiency, is analyzed in detail. Furthermore, the effects of transmitting side voltage and frequency offset on this system are studied, and the optimal design method for an SC-load WPT system is provided on a preliminary basis. Finally, the theoretical derivation and analysis are verified by means of simulations and experiments.

So far, analysis of wireless power transfer system is usually based on the constant pure resistive loads. Meanwhile, in real applications, there are many types of different loads. This paper studies a WPT system using super-capacitor as its load. In order to simplify the analysis, the equivalent model of the WPT system is derived based on the principle of power conservation. During the charging of the super-capacitor, the variations in primary, secondary currents and system efficiency are analytically derived. Considering the possible variation of the coupling coils, the influences of coupling coefficient and quality factor on the voltage and current gain are also analyzed. Finally, the theoretical derivation and analysis are verified by simulation and experiments.

The significant constraint for the applications of wireless power transfer is the low efficiency, compared to the traditional electric wired connection. In order to improve the transfer efficiency, a variety of compensation networks are proposed to reduce the reactive power transfer but parameter selection is only based on coupling coils and ignores the inverter loss. In this paper, compensation capacitor is designed and optimized to improve the efficiency of both the inverter and coupling coils. Based on the series-series resonant compensation network, the influence of resonant capacitor parameters on the efficiency of the system is analyzed. At the same time, the optimal values of capacitors are given considering super-capacitor constant current charging. Finally, the simulation results verify the analysis results.