This paper proposes a new control technique, which only employs the primary-side controller and load identification approach to adjust the charging voltage/current for both series-series (SS) and series-parallel (SP) compensated wireless power transfer (WPT) systems. The advantage is that dual-side wireless communication for real-time charging current/voltage adjustment is avoided as well as it is suitable for different charging modes, e.g. constant voltage (CV) and constant current (CC) charging defined by the battery charging profile. The load identification approach, which utilizes the reflected impedance theory and quadrature transformation algorithm for calculating the active power, is proposed to estimate the equivalent load resistance. Then, the CV/CC charging for both SS and SP compensation are achieved by PI controlled phase shift H-bridge inverter. The simulation and experimental results validate the feasibility of the proposed method. During the CC charging, the 3.01A and 3.03 A for SS and SP compensation with the error of 1.2% and 1.4% are achieved. During the CV charging, the 25.8 V and 25.7 V for SS and SP compensation with the error of 1.1% and 1.3% are realized. The proposed method improves the performance of both SS and SP compensated WPT systems to be more suitable for the applications that require compact and light weight receiver.

Charging current and efficiency of a wireless power transfer (WPT) system depend on the equivalent load resistance of supercapacitor load, which varies during charging. To achieve constant current (CC) charging and maximized efficiency under variable loads, control method that uses primary-side phase shifted H-bridge inverter and secondary-side semi-active rectifier are proposed. The secondary-side control method not only achieves CC charging, but also ensures no reactive impedance seen into the semi-active rectifier. On the other hand, the maximum efficiency tracking is based on searching the minimum system dc input current for any given output power and realized by the phase shifted H-bridge inverter controlled by the perturbation and observation algorithm. Experiments are performed to validate the feasibility of the proposed control method. During CC charging of 3 A, the maximum efficiency is 81% and the largest efficiency improvement is 15.2% at light load. The proposed method improves the system performance and is suitable for practical applications that require compact receiver and no wireless communication link between the transmitter and the receiver.

Wireless power transfer (WPT) systems have attracted much attention because of their safety, convenience and environmental friendliness. For wireless supercapacitor charging, the system efficiency and charging current are highly dependent on the load that varies over a wide range. In this paper, a simultaneous maximum system efficiency (MSE) tracking and constant current (CC) charging control scheme for a supercapacitor is proposed. For CC charging, a double-sided LCC (DS-LCC) topology is chosen due to its characteristic of providing a load-independent output current. Furthermore, the impact of the coil internal resistance on the system characteristics (especially the charging current) is investigated, so a semi-active rectifier is introduced on the secondary side to achieve accurate CC charging and improve the system robustness. Based on the variable-step perturbation and observation (VS-P&O) algorithm, the MSE is tracked by searching for the minimum system input DC current using a primary-side Buck converter on the premise that the charging current reaches its target value. The above two control loops are independent, and the mutual communication is unnecessary when they cooperate; thus, the system is simplified. The simulation and experimental results show great consistency with the theoretical analysis. The experimental system maintains the MSE of 86% during charging the supercapacitor from 20V to 50V with 2 A.

To realize the misalignment insensitivity and stable constant current/voltage (CC/CV) charging without using the extra dc-dc converter, composite compensation topology, and wireless communication modules, a primary-side control method based on the phase-shift full-bridge inverter and the laminated magnetic coupler (LMC) is proposed for the wireless charging system. First, the load-independent output current and voltage characteristics for the series-series compensation are analyzed. The equations for estimating the charging current and voltage are deduced by only using the primary-side parameters. Second, the excellent antimisalignment capability of the LMC with the primary-side integrated auxiliary coil is verified. As a result, the influence of horizontal misalignment on the estimation precision is reduced; the controllability of the charging current is ensured. Third, the dual-loop cascade PI controller is designed, and CC/CV charging is realized by adjusting the phase-shift angle. Finally, both the simulation and experimental results show that the primary-side control method realizes CC/CV charging with high precision within the reasonable horizontal misalignment range. Compared to the conventional primary-side control methods, the proposed one avoids both the load resistance estimation and mutual inductance identification. Meanwhile, the compact and lightweight receiver module is ensured.

Although the wireless charging system (WCS) achieves flexible power transmission, high system operating performance needs strong anti-misalignment capability and excellent charging controllability. Hence, this article proposes a mistuned WCS that features dual transmission channels using half-bridge inverters, magnetic flux controlled inductors (MFCIs), magnetic couplers with hybrid coils (HMCs), and the series–series compensation. Then, high misalignment tolerance and high-efficient constant power (CP) charging are achieved. First, the interrelation among the mutual inductance, adjustable inductance, load resistance, charging power, and system efficiency is analyzed based on the optimally designed system structure. Second, the circuit structure and working principle of the MFCI are illustrated. Third, the anti-misalignment capability of the optimized HMC is verified by analyzing its coupling characteristics. Then, the relative spatial position between the two HMCs is determined to ensure the negligible cross-coupling influence. In addition, the closed-loop controller's working principle and design method is analyzed to achieve high-efficient and high-controllable CP charging within a wide range of misalignment distance and load resistance. Finally, the experimental results validate the feasibility of the proposed WCS. For CP charging of 150 W, x - and y -direction misalignment ranges reach ±95% and ±47%, and system efficiency exceeds 90%, superior to the commonly used anti-misalignment methods.

This article proposes a wireless charging system (WCS) with two reconfigurable transmission channels to achieve constant current/voltage (CC/CV) charging, anti-misalignment solid ability, and zero voltage switching (ZVS) operation. First, the structure design and working principle of the orthogonal magnetic coupler (OMC) are given. The OMC's parameters are optimized using the orthogonal experimental design. Then, the coupling performance of OMC is illustrated by Ansys simulations. Second, the topology and principle of the designed WCS are analyzed. The relationship between charging controllability, misalignment performance, and system parameters is presented. The design method and working principle of the magnetic flux controllable inductor (MFCI) used as the power adjustment circuit and auxiliary improvement of anti-misalignment ability are provided. Third, the schematic diagram and hardware of the closed-loop controller are given. The PLECS simulations verify the feasibility of using the MFCI to realize the above design goals. Finally, an experimental prototype of an unmanned aerial vehicle (UAV) is built to validate the method's feasibility. When the maximum charging power is 126 W, the maximum system efficiency is 91.6%. Besides, assuming system efficiency decreases by 5% from the maximum value, the maximum horizontal misalignment ratio is 42%, corresponding to a desired approximately circular charging region.