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This article proposes and implements a continuously adjustable capacitor for multiple-pickup wireless power transfer (WPT), aiming to enhance the energy security performance under single-power-induced energy field. With the accelerated development and commercialization of WPT, the energy security issue shows the increasing significance for multiple-pickup WPT systems, where the induced open radial electromagnetic field facilitates all involved pickup coils to access the wirelessly transferred energy. If utilizing no appropriate protection strategy, the energy privacy is inevitably jeopardized, especially for the single-power-induced energy field where the auxiliary technique, such as the radio-frequency identification, cannot identify the multiple pickups. Accordingly, this article proposes a continuously adjustable capacitor that enhances the security/transmission performance for multiple-pickup WPT systems. Differing from impedance adjusting schemes reported in previous studies, the continuously adjustable capacitor can continuously adjust the impedance to match the encrypted switching frequency dynamically and continuously. In such ways, it can effectively enhance the flexibility of the WPT hardware platform for the cryptographic algorithm, thus significantly reduce the possibility of power being hacked. Finally, the simulated and experimental results are provided to verify the feasibility of the proposed continuously adjustable capacitor for the energy encryption of multiple-pickup WPT systems.

This paper proposes a quadrature-shaped pickup coil, which can realize an angular-misalignment insensitive omnidirectional wireless charging system. Recently, the three-dimensional wireless charging has shown promising prospects for removing the performance deterioration caused by the positional misalignment, which can transfer power to arbitrary spatial objectives. In the conventional design, the strength and the direction of the induced magnetic field can be adjusted by controlling the excitation currents of transmitting coils. However, the existence of angular misalignment caused by the self-rotation of the pickup unit still can result in a sharp decrease of the transmitted power. Accordingly, this paper proposes and implements a novel pickup coil topology to compensate such huge fluctuations in power transfer, which aims to ensure an angular misalignment insensitive omnidirectional wireless charging. Simulated and experimental results are both given to verify the feasibility of the proposed quadrature-shaped topology.

Bidirectional inductive power transfer (IPT) systems are attractive for applications such as electric vehicles and vehicle-to-grid systems which preferably require “contactless” and two-way power transfer. However, in contrast to unidirectional IPT systems, bidirectional IPT systems require more sophisticated control strategies to control the power flow. An indispensible component of such control strategies is the robust and accurate synchronization between the primary- and pickup-side converters, without which the transfer of real power in any direction cannot be guaranteed. This paper proposes a novel technique that synchronizes converters on both the primary and pickup sides of bidirectional IPT systems. The technique uses an auxiliary winding, located on the pickup side, to produce a synchronizing signal which, in turn, can be utilized to regulate the real power flow. This paper also presents a mathematical model for the proposed technique and investigates its sensitivity for component tolerances. The viability of the technique, which is applicable to both single- and multiple-pickup IPT systems, is demonstrated through both simulations and experimental results of a 1-kW prototype bidirectional IPT system.

Capacitively coupled power transfer (CCPT) technology has been proposed and investigated recently as an alternative contactless power transfer method. A CCPT system has the advantage of being able to transfer power across metal barriers with low standing power losses, so it is potentially good for charging consumer electronics such as mobile phones, laptops, lamps, etc. However, a big challenge in designing a CCPT charging platform is the output voltage of a CCPT power supply varies greatly with the positioning and alignment of the pickup on a charging pad due to the change in power flow. This paper proposes a CCPT charging platform with a matrix charging pad and a dynamically soft switched transformer to control the power flow and regulate the output voltage under variable coupling conditions. The proposed charging platform is verified by simulation and experimental results.

Polyphase inductive power transfer systems have been proposed as a method of increasing the tolerance of roadway-based vehicular systems to the lateral movement of pickups. However, the design of the power supply is challenging due to the changing nature of the load presented by mobile pickups. An inverter driving a traditional single-phase system must be designed with only the peak power in mind, as the reactive load of the pickups is essentially constant due to the relatively constrained pickup movement and will normally be compensated when the system is designed. This is not possible for an inverter driving a polyphase track, as the reactive load will vary with the lateral position of the pickup, just as a portion of the real load that must be supplied by each phase will also vary. This paper presents a simple but accurate method of determining the real and reactive load on each phase of the track as the pickup moves, allowing the inverter to be correctly designed with appropriate component ratings.

The majority of commercial contactless power-transfer systems used in manufacturing applications can only tolerate limited movement of the power pickup relative to the track to which it is magnetically coupled. This paper describes a new multiphase (quadrature) pickup that significantly improves the tolerance of the power receiver to such relative movement, enabling expanded applications such as continuously powered automatic guided vehicles, robots, and other vehicles to be considered. The advantage gained is largely independent of the track type, so that single-phase or multiphase tracks can be used as desired to improve both the power transfer and lateral tolerance as required. The improvement is achieved by capturing both vertical and horizontal components of magnetic flux around any track.

This paper describes the design of a new unity-power-factor inductive-power-transfer (IPT) pickup using an LCL tuned network for application in high-power systems. This new topology has the potential to increase the efficiency and reduce the cost of high-power pickups by minimizing the reactive currents in the pickup coil and the reflected VAR loading on the power supply. In a practical system, the rectifier and associated processing circuitry distorts the current waveforms, adding an effective inductive loading to the pickup circuit. A series compensation capacitor is added to correct this loading. A design strategy is developed for the new topology, and two example circuits are constructed and compared experimentally with a traditional parallel-tuned (LC) pickup operating on a monorail-based IPT system.

This paper proposes a novel inductor-capacitor-inductor wireless power pickup with directional tuning control (DTC) for a magnetic amplifier. The proposed technique allows the power pickup to achieve full-range tuning/detuning operation to regulate power flow and maintain the output voltage to be constant. The method eliminates the tedious fine-tuning process associated with traditional fixed power pickup tuning methods and eases the component selection. Moreover, it can overcome the online circuit parameter variations and automatically achieve the maximum power transfer capacity when required. In order to meet dynamic load demands, a magnetic amplifier is used as a variable inductor and is controlled by a novel DTC algorithm to change the tuning condition of the power pickup. The effectiveness of the proposed power pickup and its applicability to general wireless power transfer applications have been demonstrated by both simulation and experimental results.

Roadway powered electric vehicles with minimal or no onboard energy storage have been proposed for many years, but the concept has only recently become feasible via three-phase inductive power transfer (IPT) systems. A wide zone can be created over which power transfer is relatively constant. This gives good tolerance to the alignment of the pickup relative to the track allowing simple low-cost pickup structures to be used. While three-phase IPT tracks make the vehicle pickup and power transfer simpler, they are difficult for the power supply to drive due to the presence of mutual coupling between the track phases resulting from the physical layout of the track. These mutual inductances induce voltages within each track phase that, because of the inductor-capacitor-inductor network, cause large currents within the power supply inverter and imbalances within the system. This paper presents an analytical assessment of the problems caused by the interphase mutual inductance, and three possible solutions. Two of the methods involve modifications to the track layout to alter or remove the mutual inductances, while the third and preferred technique requires additional ferrite cores between the various phases to compensate this adverse mutual inductance without affecting the power transfer to the pickup loads.

This paper describes a new scheme for continuous monitoring of torque angle and speed of a 3-kVA laboratory synchronous machine. The proposed scheme does not require mounting of an optical disc or a magnetic pickup on the shaft of the machine. Use is made of a 400-Hz 32-pole tacho generator mounted on the machine shaft. Intel's 8085A microprocessor is employed for the measurement and calculations of torque angle and percentage slip. The testing and evaluation of the scheme, for various operating conditions, have been carried out in the laboratory.