To improve the transient-and steady-state performance indexes for an active power filter (APF) and reduce the steady-state switching loss, an APF event triggering control based on a switching model is proposed. By establishing the dynamic model of the APF system and combining with the Lyapunov function, the constraint conditions satisfying the system stability are obtained, according to which the design range of parameters when the system reaches its steady state is analyzed and the switch vector selection method in a normal operation mode is obtained. On this basis, the switching principle for the controller is formulated, so that the APF system can quickly track the target current and reduce the number of switching tube actions on the premise of ensuring the control accuracy when it reaches the steady state. Finally, the correctness and superiority of the proposed design method were proved by simulation and experimental results.

To improve the transmission efficiency of a wireless power transfer (WPT) system, its structural parameters were optimized. Considering the low efficiency and poor comprehensiveness of the traditional optimization methods when designing the WPT system’s structural parameters, a parameter optimization model for an SS-type WPT system was established to determine the optimization parameters. On this basis, a structural parameter optimization method for the WPT system was proposed, which integrated orthogonal experiments, finite element simulation and improved particle swarm optimization-backpropagation neural network algorithm. Experimental results show that the average error between the predicted and experimental values was 4.3%, indicating that the proposed optimization method is reasonable, feasible and of reference significance for the structural parameter optimization of WPT systems.

The wireless charging technology for electric vehicles can overcome the shortcomings of traditional wired charging methods such as low convenience and high safety risk, but the magnetic flux leakage in its transmission process may lead to electromagnetic interference and even pose a threat to human health. To solve the magnetic flux leakage problem in wireless charging, the magnetic field distribution around a high-power DD coil is studied, and a novel active shielding design is proposed, i.e., the active shielding coil is directly connected in series with the primary coil to reduce the leakage magnetic field. At the same time, the additional coupling between the shielding coil and the receiving coil of the wireless charging system is eliminated. In addition, multi-objective optimization is performed to determine the optimal parameters of the shielding coil with the maximum magnetic flux density of the target surface, the output power of system load and the system transmission efficiency as the objective functions. Finally, a 5 kW experimental prototype was built to verify the analysis results and investigate the effect of the shielding coil on the system parameters. Results show that the optimized shielding design reduces the magnetic field intensity in the target region by 33.5%, while the power and efficiency of the wireless charging system are not significantly reduced.

In the multi-load wireless charging field, it is often necessary to provide constant voltage (CV) or constant current (CC) output for charging the receiving equipment. However, in the existing research on the multi-load wireless power transfer (WPT) system, there is usually just one mode, i.e., CV or CC, and the work in which both the CV output and CC output are provided is seldom reported. A coplanar two-branch WPT system was proposed, which can provide two branches of load-independent output, i.e., one CC output and another CV output. The two branches can be designed independently without affecting each other. By switching control or moving away one branch, three kinds of power supply modes can be provided, i.e., both the CC and CV branches, only the CV branch, and only the CC branch. First, the topological structure of the two-branch WPT system was introduced, and the principle of load-independent and two branches operating independently was explained in detail. Second, the influence of loss on the system performance and the estimation method for the dynamic range of load were revealed. Finally, a two-branch experimental platform consisting of five resonators was built, and the experimental and theoretical results were in good agreement. By inserting ferrite plates to the junctions of coplanar adjacent coils, the magnetic coupling between adjacent coils was enhanced significantly, and the system transmission efficiency was improved as a result. In the three operating modes (i.e., charging only the CC load, only the CV load, or both the CC and CV loads simultaneously), the measured maximum transmission efficiency reached 89.2%, 93.5% and 91.6%, respectively.

Charging efficiency is an important index for evaluating the performance of a wireless charging system. A dual-loop control method based on current proportion is proposed to improve the charging efficiency of a layered magnetic coupling wireless charging system with dual transmitting coils, which can achieve constant voltage and constant current output while improving the system efficiency by approximately 4%. First, the working principle for the dual-transmitter wireless charging system based on LCC-S compensation network is introduced, a mutual inductance model is established, and the relationship between output voltage and current is deduced. Then, the coupling relationship between the changes in mutual inductance and system efficiency is studied, and a double closed-loop control method based on the optimal current proportion is proposed to achieve constant current and constant voltage output by outer-loop control and efficiency optimization by inner-loop control current distribution. Finally, the feasibility of the double closed-loop control strategy with optimal efficiency was verified by simulations and an experimental platform with 250 W.

The navigation safety of UAV depends on the normal operation of its electronic equipment and sensors. Electromagnetic interference may lead to errors or failures of flight control systems, affecting the flight path and stability. The use of metal materials can effectively shield the electromagnetic field, but the introduction of metal will change the magnetic field characteristics of the system, resulting in the detuning of the compensation network and leading to the power supply system output power deviation and low efficiency. To study the electromagnetic shielding effect of aluminum-ferrite and the influence of the shielding structure on the electrical parameters of a magnetically coupled resonant wireless power supply system, the influence of the aluminum plate on the spatial magnetic field is studied at first, and the variations of the coil self-inductance, mutual inductance and the magnetic induction intensity in the non-working area are analyzed. Then, ferrite is added to improve the electrical parameters, so that the self-inductance and mutual inductance of the coil are close to the initial values. Finally, simulation results verified that the electromagnetic radiation in the non-working area met the safety standards. In addition, an experimental platform was built to analyze the characteristics of output parameters and verify the effectiveness of the shielding structure.

Aimed at the problem of lateral offset in the magnetic coupling device of a wireless charging system for rotorcraft unmanned aerial vehicles (UAVs), a self-alignment method of coils is proposed by collecting the output voltage while moving the transmitting coil and adjusting its position according to the value of the collected output voltage. First, a mutual-induction model is established to analyze the electrical and magnetic characteristics of the wireless charging system, thereby deriving the expression of the relationship between the output voltage and the lateral distance between the transmitting and receiving coils. Then, the size of a magnetic coupler is designed based on the size of the alignment region, and the alignment regionis divided. Additionally, a specific alignment process is outlined. Finally, an experimental platform was established to conduct self-alignment experiments on the transmitting and receiving coils. Based on the experimental results, it is evident that the proposed method can effectively achieve self-alignment of coils with an alignment accuracy of less than 1.5 cm, meeting the requirements for efficient wireless charging of UAVs.

The battery charging process typically consists two stages, i.e., constant current (CC) followed by constant voltage (CV). However, the existing wireless power transfer (WPT) technology still encounters several challenges during the transition from the CC mode to CV mode, including battery state monitoring, requirement for bilateral communication and cross-coupling among multiple coils. To address these problems, a novel quasi-CLC-LCC topology is proposed, which can realize the smooth transition from the CC mode to CV mode without the need for additional control. A CLC compensation network is employed by the transmitter circuit, enabling the transmitting coil current to be considered as a CC source. On the secondary side, two series compensation circuits are connected in parallel, and two branches collaboratively achieve CC charging for the battery at the initial charging stage. As the charging process progresses, owing to the unidirectional conductivity of diodes, one of the branches is clamped and disconnected, enabling the WPT system to enter into CV output. Finally, an experimental platform with 2.6 A charging current and 105 V charging voltage was constructed to validate the feasibility of the proposed wireless charging topology.

To realize the fault-tolerant control without adding extra hardware, a residual vector reconstruction strategy is proposed for an open-end winding motor drive system with isolated DC buses under the open-circuit fault of one switch. Meanwhile, the maximum utilization of residual voltage vectors is achieved, so that the operation performance of the drive system in its fault-tolerant operation is improved to a great extent. Furthermore, a phase duty cycle method is used to optimize the switching sequence in order to solve the problem of imbalanced switching action during the vector synthesis process. As a result, the switching action is balanced. Finally, the operation result under the proposed fault-tolerant strategy was analyzed in depth, and the operation performance of the system after fault was validated through a hardware-in-the-loop experiment.

To improve the accuracy of state-of-charge (SOC) estimation for lithium-ion batteries, an SOC estimation method based on an improved sparrow search algorithm optimized extreme learning machine is proposed. In response to the problem of unsatisfactory estimation accuracy caused by the improper number of neurons in the hidden layer of the extreme learning machine, the sparrow search algorithm is selected to optimize the number of neurons in the hidden layer of the extreme learning machine. To avoid the problems of poor diversity of randomly generated populations and the tendency to fall into local optima at the later stage of the sparrow search algorithm, Tent chaotic mapping and the Metropolis criterion in a simulated annealing algorithm are introduced to improve the sparrow search algorithm’s global search capability. The advantages of the proposed algorithm in terms of accuracy and efficiency compared with the traditional extreme learning machine and long short-term memory networks were verified through simulation experiments under FUDS operating conditions at room temperatures. Finally, a dSPACE hardware-in-the-loop experimental platform was established and further used for online verification under UDDS conditions at 0 ℃ and 25 ℃. Results showed that the proposed algorithm maintained SOC estimation errors within 1.3% at both the environmental temperatures, and the root mean square error decreased by 46.7% and 51.8% compared with the traditional extreme learning machine, respectively, thereby verifying its feasibility and superiority.