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Applying the recycled power battery to automatic guided vehicles can greatly reduce system cost and prolong the life cycle of the battery. However, the consistency of recycled power batteries is poor, and the imbalance of battery voltage will occur during the charging or discharging process. Therefore, a double-switch single-transformer integrated equalizer is proposed to balance automatic guided vehicles in both charging and discharging operations. The equalizer's multiwinding transformer shares the dc–dc converter's inductor, and the secondary side generates current by utilizing the current ripple on the primary windings. The battery string is balanced by the multiwinding transformer, without extra switches, when the circuit works in charging and discharging mode. A prototype for four battery cells is built to verify the proposed equalizer and its dynamic balance conditions, and a comparison with existing equalizers is presented. The results show that the system in both modes can realize the automatic balance without affecting the function of the dc–dc converter. The proposed circuit requires fewer components than the existing bidirectional integrated equalizer. [ABSTRACT FROM AUTHOR]

In the hybrid energy storage system (HESS), the voltages between the battery cell and the supercapacitor cell are different, increasing the circuit and control complexity of the balance system. Therefore, a bidirectional integrated equalizer based on the Sepic–Zeta converter is proposed for the HESS, which realizes both battery string and supercapacitor string balance during the energy exchange. The inductors in the Sepic–Zeta converter are used as the primary side of the balanced multiwinding transformer. The Sepic–Zeta converter generates the current ripples to drive the multiwinding transformer. The secondary side generates currents to balance the HESS, and hence, the equalizer itself is essentially switchless. Therefore, the proposed circuit can reduce the complexity of the HESS. Experimental and comparative results show that the proposed equalizer achieves the balance of the HESS. [ABSTRACT FROM AUTHOR]

The domino-resonator wireless power transfer system is designed in this work to harvest energy from the magnetic field around a 110-kV high voltage transmission line and supply power to the online monitoring device continuously over 1.1 meters insulation distance. Each domino resonator is evenly spaced and is embedded inside sealed insulation discs. The theoretical analysis shows that the constant voltage (CV) mode and the constant current (CC) mode can be realized by adjusting the receiver's switch state, which can meet the battery's CV and CC charging requirements. Such a method cancels the communication between the transmitter and the receiver. The finite-element simulation results show that the influence on the electric and magnetic field intensity distribution near the insulator can be negligible. Finally, a 30 W prototype with an output voltage of 7 V is built. The experimental results show that the fluctuation of output voltage (CV mode) and output current (CC mode) is less than 6% and 7%, respectively. The maximum efficiency is higher than 40% when the transmission distance is 1.1 m, and the number of coils is 12. [ABSTRACT FROM AUTHOR]

Multitransmitter wireless power transfer system gets more and more applications as it can maintain high efficiency in a large space range. This article focuses on modeling the multitransmitter system, and proposes an impedance matching method to improve efficiency under lateral-misalignment conditions. The theoretical analysis shows that the maximum transfer efficiency can be achieved as long as the equivalent input impedance of the transmitters is regulated to be the same under misalignment condition. Hence, a double closed-loop control strategy is proposed to realize maximum efficiency point tracking, where the primary control loop adjusts the input impedance of the transmitters through pulsewidth modulation, while the second control loop maintains constant output power by a dc–dc converter. A 500-W prototype is built to validate the feasibility of the proposed method. The efficiency is always higher than 90% with an improvement of up to 20.3% compared to that without such a method when the lateral misalignment increases from 0 to 10 cm (0%–41% of maximum coil size). [ABSTRACT FROM AUTHOR]

In general, misalignment in a wireless power transfer system is inevitable, which decreases the efficiency of the system. In this paper, a full-bridge dual resonant tank (FBDRT) topology is proposed to improve the system efficiency under the lateral-misalignment condition of a wireless power transfer system. The topology with two transmitters connected with two separate half bridges is employed to deliver power to the load. Operating principle, efficiency, current, power, and soft-switching region of the proposed method are analyzed in detail, and a comparison is drawn in with the traditional series–series topology. Theoretical analysis shows that the equivalent impedance of the transmitters can be adjusted, utilizing the phase-shift modulation. The proposed method holds a higher efficiency and a wider soft-switching region when the phase is selected reasonably. A 100 W prototype is built to validate the feasibility of the proposed topology. The efficiency of FBDRT is always higher than 88.3% with an improvement of 6.8%, compared with that of the traditional SS topology when the lateral misalignment increases from 0 to 200 mm (0%–50% of maximum coil size). [ABSTRACT FROM AUTHOR]

Due to the complexity of driving conditions and the increase of the driving range of electric two-wheelers and three-wheelers vehicles, the power battery string is in a long-period unbalanced discharge state, which affects the power output and even causes certain safety risks. A compact-size multi-winding transformer-based discharge equalizer is proposed to solve these problems and minimize the impact on the system volume by sharing the primary inductor with a boost discharger. When the boost converter is powering a load, the multi-winding transformer equalizer is driven by utilizing the square wave voltage generated on the inductor in the boost converter and produces multiple identical voltage levels to achieve voltage balance. Thus, the automatic balance can be achieved with only one winding and one diode for each module. An experimental prototype containing four batteries was established to verify the feasibility of the proposed method. Moreover, a quantitative comparison shows the proposed method obtain a more compact-size equalizer because of no need for a separate transformer, compared with the traditional equalization method based on the transformer. [ABSTRACT FROM AUTHOR]

The traditional balance circuit is employed to balance the retired battery string. It will occupy some space for the extra switches, inductors, or/and capacitors of the energy storage system. This letter is trying to share the inductor of the dc–dc converter with the balance system by utilizing the current ripple on the inductor of the multiwinding transformer. The balance circuit does not require additional switches and control logic. The results of dynamic charging conditions show that the circuit is appropriate for balancing the battery string, and the system efficiency with the proposed approach reaches 94.1% at rated 28-W input power. The balance system only increases one diode and one inductor for each cell, which reduces the cost by 60% and 66% separately compared with the traditional resistance equalizer and transformer-based equalizer. [ABSTRACT FROM AUTHOR]

For inductive power transfer (IPT) systems, loads and system input voltages are subject to change, which affects system efficiency and stability. This article presents a perturbation and observation (P&O) method for maximum energy efficiency tracking (MEET) with a model predictive control (MPC) scheme for improving the dynamic performance of series–series compensated IPT systems. In the IPT system, the inverter at the primary side incorporates the P&O method and phase shift modulation (PSM) to minimize system input power. Meanwhile, the rectifier at the secondary side is controlled by MPC control based PSM to improve the dynamic response of the output voltage. Simulated and experimental results show that, compared to the PI controller, the MPC controller, based on a simple but accurate mathematical model, has a better dynamic response to load and input voltage variations. With the MPC controller, the settling time of the output voltage is reduced by 85.7%, which indicates a particularly stable power supply to the load. Furthermore, MEET adopting the P&O method in the IPT system can promote the system efficiency by 1.85% on average when the output voltage is regulated by the MPC controller. [ABSTRACT FROM AUTHOR]

This letter presents an inductive power transfer system based on a new variable coil structure to achieve load-independent constant current (CC) and constant voltage (CV) outputs for charging electric bicycles (EBs), without involving complex control strategies. The new variable coil structure consists of three-layer coils, i.e., two bipolar coils and one unipolar coil, on the transmitter side and one unipolar coil on the receiver side. The compact and portable receiver with series compensation is installed in the EB, while two switches on the transmitter side at the power charging station are utilized to reconfigure the transmitter coil structure to select the charging mode, i.e., CC mode or CV mode. The proposed system can achieve zero phase angle operation, fixed operating frequency, and zero-voltage switching, which will lower the power rating of power switches and improve the efficiency. A laboratory prototype is built to verify the feasibility of the proposed method. [ABSTRACT FROM AUTHOR]