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This paper proposes and implements autonomous control of a multiple-receiver wireless charging system. The charging control problem is challenging due to the decentralized nature of the system, possible changing numbers and types of energy storage devices as loads of the receivers, and complexity in wireless power distribution mechanism. The game-theory-based control is developed that fully respects the unique characteristics of the transmitter (i.e., charger) and receivers. The preferences of the individual devices are first quantified using utility functions. Then, the charging control problem is formulated as a generalized Stackelberg game considering the leader–follower relationship between the transmitter and receivers, and the limited total charging power. At each control instant, the generalized Nash equilibrium among the receivers, i.e., charging power distribution here, is reached by searching the Lagrange multiplier while the total charging power from the transmitter is updated in a step-by-step manner. Both simulation and experimental results show that the proposed charging control autonomously manages and updates the power distribution in the cases where the receivers with different energy storage devices quit or join the wireless charging. [ABSTRACT FROM PUBLISHER]

This paper develops a novel voltage equalizer by combining wireless power transfer (WPT) and a voltage multiplier (VM) for series-connected energy storage cells. The physical isolation achieved by WPT can offer several unique benefits that traditional equalizers can hardly provide. In this paper, the characteristics of a multiple-output VM are analytically discussed and used to develop an equivalent one-output VM model. Based on this model, parameters of the WPT system are properly designed. The proposed design methodology can achieve a single-switch voltage equalizer without feedback control, which dramatically decreases the circuit complexity and cost. Moreover, this methodology can naturally ensure a robust system under small coil misalignment. In the experiment, the proposed system is built to balance four series-connected ultracapacitor modules. The system efficiency is 72.8% at a load power level of 10 W. [ABSTRACT FROM PUBLISHER]

In this paper, the loading effect of a Class E power amplifier (PA) driven 6.78 megahertz (MHz) wireless power transfer (WPT) system is analyzed at both circuit and system levels. A buck converter is introduced and controlled to track an optimal equivalent load that maximizes the system efficiency under uncertainties in the relative position of coils and the final load. For power control, an additional degree of freedom is provided by adding an ultracapacitor bank. A control strategy is proposed to track the maximum efficiency and charge/discharge the ultracapacitor bank through the on/off control of the Class E PA. Thus, high system efficiency can be maintained under various uncertainties and load power demands. Finally, the theoretical analysis and the control scheme are validated in experiments. The results show that the proposed Class E PA-driven MHz WPT system can stably achieve a high efficiency under different coil distances and various constant/pulsed power profiles. The measured highest system efficiency can reach 72.1% at a load power level of 10 W. [ABSTRACT FROM AUTHOR]