The electric-field coupled wireless power transfer (ECPT) system possesses several advantages, including lightweight coupling pole plates, cross-metal power transmission and negligible eddy current losses. Specifically, the par-ity-time symmetric ECPT(PT-ECPT) system characterized by its capability to maintain a constant output under variations in the coupling pole plate spacing exhibits promising application prospects. Consequently, the electric-field radiation distribution of the PT-ECPT system was studied. The theoretical analysis, simulations and experimental results indicate that compared with those of the conventional resonant ECPT systems, the electric-field distribution of the PT-ECPT sys-tem is more concentrated in the regions of strong coupling while maintaining identical output power. This concentration is particularly pronounced when the coupling coefficient is small, which makes the PT-ECPT system more secure under conditions of reduced coupling coefficients.

The electromagnetic radiation emitted by an AC/DC telecommunication power supply is prone to exceeding the limit standards, so the researches on its electromagnetic radiation mechanism and prediction methods can improve the corresponding electromagnetic compatibility (EMC) design. First, after the analysis of the source and propagation path of common-mode(CM) electromagnetic interference in an AC/DC telecommunication power supply module, it is suggested that its far-field electromagnetic radiation can be decomposed into two types, which are driven by input-port and output-port CM voltages, respectively. Then, a novel method of far-field electromagnetic radiation prediction is proposed by combining the CM voltage-driven sources with the radiation transfer functions of parasitic radiators. The spectrum measurement of each CM voltage-driven source is realized by designing a spectrum analyzer and a resistor attenuator, and the radiation transfer functions of each parasitic radiator is numerically calculated using an electromagnetic simulation software FEKO. Finally, the radiation prediction of a 4 kW AC/DC telecommunication power supply module was achieved, and the effectiveness of the proposed prediction method was verified by test results.

The lithium-ion battery equalizer based on switched inductor is still of strong practical value in low-power portable electrical equipment. However, the switching devices in the equalizer operate in a hard-switching state under traditional control strategies. A soft-switching implementation algorithm for battery equalizer based on switched inductor in continuous current mode is proposed. The determinants of the inductor current of the equalizer and the charging and discharging current of a battery cell are analyzed. Then, a soft-switching implementation algorithm for the switching devices in the equalizer is proposed, and its control accuracy is analyzed. The equivalent impedance and open-circuit voltage of the battery cell can be obtained in real time by detecting the change rate of battery cell voltage and charging current, which further ensures the accuracy of the algorithm. Experimental results show that the proposed soft-switching control algorithm has a good performance.

The triple active bridge(TAB) DC-DC converter based on the phase-shifting plus duty cycle control strategy has advantages such as a high efficiency and an expandable soft switching range. However, its small signal modeling process is complex, and the parameter setting of closed-loop control loop is difficult. To solve these problems, a full-orer continuous generalized state space average modeling and PI controller design method for TAB converter under phase-shifting plus duty cycle control is proposed. First, the operation principle and Y-type equivalent structure of the TAB converter are analyzed. Second, combined with the characteristics of phase-shifting plus duty cycle control and the equivalent method of AC square wave source, the generalized state space average model of the TAB converter is derived. Third, based on the derived model, the transfer function from input to output is obtained, and the parameters of PI controller are designed. Finally, the correctness and effectiveness of the proposed method were verified by digital simulations and prototype tests.

In the design of switching power supply inductors, the calculation of magnetic circuit parameters is of significance. For inductors with an open air gap in the column of EE-type iron cores, the total magnetic flux is divided into seven equivalent magnetic fluxes by using the method of magnetic field division through finite element simulation and theoretical analysis. The concept of invalid number of turns is proposed, and the analytical expression for equivalent area of air gap permeability is obtained on the basis of fully considering the influences of diffusion magnetic flux, bypass magnetic flux and uneven distribution of magnetic flux in the core. In addition, according to the equivalent magnetic circuit model, the analytical expression for inductance factor A₁ is obtained. The concept of inhomogeneity coefficient of magnetic flux density distribution is also proposed, and based on the maximum magnetic flux density per unit current, the analytic expression for saturation current I₁ is obtained. Afterwards, the magnetic circuit parameters are accurately calculated using Excel. Finally, the accuracy of the proposed formulas was verified by experimental measurements, providing a useful reference for designers.

To obtain the state-of-charge (SOC) estimation value well, a second-order equivalent circuit model is selected as the research object. Aimed at the disadvantage that the recursive least squares method with a forgetting factor is easy to be disturbed by environmental factors such as noises in the parameter identification, a bias compensation recursive least squares method is proposed to realize the accurate identification of model parameters, and the SOC is estimated combined with the unscented Kalman filter algorithm. In view of the disadvantages of the unscented Kalman filter algorithm such as poor stability, the weight vectors are used to update the Kalman filter gain in the filter algorithm. Experimental results show that the total error of the proposed algorithm in estimating SOC was controlled within 2.7%, which verified the robustness and effectiveness of the algorithm.

Silicon carbide metal-oxide-semiconductor field effect transistor (SiC MOSFET) has attracted attention from the industry owing to its excellent characteristics such as high voltage, high frequency and low conduction loss. However, compared with the silicon-based IGBT, the problem of gate oxide reliability caused by the high defect density at the SiC/SiO2 gate oxide interface has become a key bottleneck restricting the large-scale applications of SiC MOSFET devices. By sorting out and analyzing the research results of the gate oxide reliability of SiC MOSFET at home and abroad in recent years, the causes of the gate oxide reliability problems at present were elaborated upon, and various commonly-used gate oxide reliability evaluation methods were summarized and compared. Finally, the gate oxide reliability of SiC MOSFET under extreme operating conditions and the development status of technologies for improving its performance were discussed.

In a certain environment where regional wind farms distribute irregularly, the traditional convolutional neural network prediction method cannot reflect the distribution states or influence relationship of regional wind farms, and it is difficult to accurately predict the wind speed. First, to solve this problem, the technology of graph convolutional networks is used for feature modeling, and the connected graph and weight matrix are established according to the topology of multiple wind farms and the cross-correlation coefficient of wind speed in each region. Second, depending on the time dynamic characteristics of wind speed at wind farms, an improved parallel convolution structure is used to obtain the correlation between wind speed series in multiple time periods at the same wind farm. Third, based on the spatial correlation and delay effect of wind speed at wind farms, the spatio-temporal characteristics of wind speed in different regions are aggregated by using a second-order aggregation method. Finally, the verification of data from one regional wind farm shows that the proposed method can extract the spatio-temporal characteristics and improve the performance of ultra short-term wind speed prediction for multiple wind farms on 0-4 h prediction scale.

Aimed at the current imbalance problem in parallel connected multiple light-emitting diode (LED) strings, an efficient multi-output LED driver is proposed to achieve current sharing among different LED strings and improve the efficiency of the circuit. A Boost converter and a series-resonant converter are cascaded to achieve current sharing and a high voltage gain. The transformer leakage inductance suppresses the switch's current rising rate in the turn-on period, which provides the zero-current-switch (ZCS) condition. Moreover, a lossless snubber circuit is added to slow down the switch's voltage rising rate in the turn-off period to significantly reduce the switching loss, and a large magnetizing inductance of transformer is selected to reduce the transformer loss. Meanwhile, only one active switch is used, which reduces the circuit cost and simplifies the control. Therefore, current sharing, high efficiency and high voltage gain are obtained, and the cost is low. The circuit operational principle and operating characteristics together with the specific procedure of parameter design are analyzed and presented in detail. Finally, a 7.9 W two-output prototype with 12 V input voltage was built to verify the effectiveness of the proposed LED driver.

In the application of wide output voltage range, some problems exist in an LLC resonant converter under the traditional frequency control, such as a wide switching frequency regulation range, a large circulation current and difficulty in high-efficiency operation. To solve these problems, a dual-full-bridge LLC resonant converter under a fixed-frequency phase-shift and fixed-frequency PWM hybrid control strategy is proposed, which is suitable for the wide range of output voltage. This converter is composed of two full-bridge LLC resonant converters sharing one bridge arm, and the output voltage is modulated by the hybrid control, so that a quadruple voltage gain and a wider output voltage range of the resonant converter can be realized. Meanwhile, the problems that the large circulation current exists under the traditional frequency control and the soft switching cannot be realized at a small phase shift angle are solved, thus improving the system efficiency. The switching frequency of the converter is always equal to the resonance frequency, and the voltage gain is independent of load, which is helpful for the design of the magnetic element. At the same time, the soft switching can be realized in the full load range. Finally, a detailed analysis of the circuit principle was given, which was further verified by simulations. An experimental platform was also established to validate the feasibility and effectiveness of the proposed converter.