Dynamic wireless power transfer (WPT) for charging electric vehicles (EVs) overcomes some of the problems associated with EVs battery size and weight as well as distance range limitation and long charging duration. High efficiency and fixed output voltage of WPT systems are of great importance for reducing operating cost and facilitating battery charging, respectively. On the other hand, utilizing the maximum power transfer capability of a WPT system leads to a capital cost saving of the system. In this article, the product of transferred power efficiency and input power factor (η·PF) is regarded as a criterion to make near full usage of the system power transfer capacity as well as reduce the capital and operating cost of the system. An optimal frequency-tracking method is proposed to maximize η·PF of the system taking into account possible abrupt changes in the coupling coefficient of the WPT system due to deviations of EV from alignment with the track along the road. In addition, the output voltage of the system is regulated simultaneously by an on-line adjustment of the primary inverter duty ratio. The optimal frequency-tracking method and voltage regulation are validated by extensive simulation and experimental results.

A high efficiency and a constant voltage at the output stage are among the major concerns in wireless charging of dynamic electric vehicles. They are usually achieved by additional converters or asymmetric switching which suffer from high cost and hard switching. To overcome these drawbacks, a variable-frequency retuning approach is proposed in this paper with LCL-Series compensation. As opposed to conventional control methods with resonance frequency as target operating frequency, this approach uses a new optimum frequency which enables ZVS. Also, it minimizes the conduction loss of the inverter switches in a wide range of load and coupling coefficients. In addition, it improves the total system efficiency up to 6% together with an increase in the power transfer capability. Using the proposed method, both sides' currents increases up to 45% depending on the load. To find the optimum frequency in a system without resonant parameter information, an on-line maximum efficiency search method based on Perturb and Observe is employed. Extensive simulation results using PLECS, together with experimental results from a laboratory setup are presented to confirm the effectiveness of the proposed method under varying load and coupling.

In motor drives supplied through wireless power transfer (WPT) systems, a high frequency inverter and a low frequency one are commonly used in the primary and secondary sides of the system, respectively. This arrangement causes reduced reliability and efficiency, and high cost. Besides, using an electrolyte isolator like big dc capacitor, shorten the system lifetime. This capacitor is usually located in parallel with the motor drive system. So, the capacitor fail leads to a total system failure. In this paper, a multi-functional single inverter used in the primary side dispatch as the high-frequency ac power via a magnetic link as well as driving an induction motor without any extra inverter in the secondary side. This is obtained by using a simple AC/AC chopper in the secondary side as a wave shaping convertor. In this way, the desirable ac power can efficiently be injected to the motor. The modeling and mathematical analysis of the proposed wireless drive are presented. Also, the performance of the drive under an open-loop V/F control system is verified by simulation and experimental results.

On-road dynamic charging of electric vehicles by wireless power transfer systems has emerged recently as a cost-saving means for modern transportation. Thus, maximizing power transfer efficiency is essential in the system design stage as well as during the operation. In addition, the voltage regulation of EV power bus, supplied by the power transfer system and battery, is needed for a long life of the battery. In this paper, these two requirements are fulfilled under varying EV driving conditions by a single control system applied to a wireless power transfer system. The control system simultaneously tunes the switching frequency of the primary side inverter and the conversion ratio of the secondary side converter to achieve the maximum possible efficiency. In addition, the system adjusts the duty cycle of the primary side inverter to regulate the output voltage. Furthermore, an allowable range for the optimal frequency is determined and imposed to the primary inverter to compensate the power factor reduction according to IEEE std-1547.1. The system needs just one dc/dc converter instead of two as reported in the literature, without any restriction in zero state and start-up conditions. The control system does not need any information of the coupling coefficient and compensating circuit elements. The system is applied to a 180 W experimental wireless power transfer setup. Extensive simulation and experimental results are presented to validate the proposed control system.

Maintaining high efficiency and controlling output voltage with variable load is challenging for inductive power transfer (IPT) based battery charging systems. In addition, choosing the proper charging scenarios simultaneously with the battery's equivalent load variation significantly improves the charging rate. This paper proposes a semi-active rectifier (SAR) battery charging system on the basis of a series-series resonant IPT system using constant-power (CP) and constant-voltage (CV) charging modes. A novel control approach based on the adaptive selection of the operating frequency of IPT and the conduction angle of the SAR is used to achieve high efficiency in CP-CV modes. The inverter and the SAR are both capable of soft switching. Furthermore, considering the same maximum power in CP and constant-current (CC) modes, the CP mode offers more charging rate with less destructive effects. The proposed control strategy has been simulated, and a prototype system is implemented to show the high-efficiency performance of the system during CP-CV modes.