In view of the problems of dual-stator winding induction machines (DSWIMs) under traditional direct torque and flux control such as large torque, large flux and large current ripple, and considering that it is difficult to control the flux at low speed and the corresponding noise level is high, a novel direct control method for speed and flux based on super twisting sliding mode controller (STSMC) is proposed for DSWIMs. A nonlinear controller with zero convergence error in finite time is designed, which meets the Lyapunov stability condition. On this basis, a novel torque allocation algorithm for DSWIMS is put forward, which can make the DSWIMs run in a wider speed range, including zero speed. The electromagnetic torque is provided by two sets of winding according to its rated power. In addition, a full-order observer based on sliding mode control is designed for DSWIMs, which can accurately estimate the winding flux, flux angle and rotor speed to achieve the optimal flux state. Finally, an experimental test was carried out on a 3.3 kW DSWIM drive system to evaluate the performance of the proposed DSWIM control scheme. Experimental results show that the proposed control method, torque allocation algorithm and full-order observer were effective in different speed regions.

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 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.

The design of DC-DC converters which are applied to vehicle auxiliary power modules (APMs) is taken as a research object, the topology of a two-stage DC-DC converter consisting of a three-level Boost (TL-Boost) topology and a half-bridge LLC resonant topology is proposed, and its working principle is analyzed. The front-stage TL-Boost topology converts a wide range of input voltage into a stable voltage, ensuring the high-efficiency operation of the back-stage half-bridge LLC resonant topology. The feasibility and correctness of the proposed DC-DC converter were verified by establishing an experimental platform and carrying out relevant experiments.

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.

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.

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.

To improve the metal object detection performance for an electric vehicle wireless charging system, a sensitivity optimization method for the detection coil was proposed. The equivalent electromagnetic model of a rectangular detection coil with a metal object approaching was established. The changing mechanism of the physical parameters of the coil was studied, and a theoretical formula for changes in the parameters of the detection coil which were caused by metal objects of different sizes was obtained. The influence of several configuration parameters on the sensitivity of the detection coil was analyzed, and the configuration of the detection coil was optimized by combining the actual operating conditions of wireless charging. Through the electromagnetic field simulation and experimental verification, the accuracy of the theoretical model was proved. Finally, a metal object detection experiment was carried out in a 3 kW wireless charging system, which verified that the metal object detection system built on the basis of the optimized detection coil can detect metal objects with a size of 25 mm and above. In addition, it had anti-interference capability.

The light-emitting diode (LED) driver usually needs a large electrolytic capacitor to reduce its low-frequency current ripple. Therefore, the short life of the electrolytic capacitor is an important factor restricting the life of LED driver, and eliminating the electrolytic capacitor is a key to the long-life LED driver. Under this background, a two-switch electrolytic capacitor-less LED drive circuit topology based on flyback converter is proposed. The auxiliary power balance circuit and flyback converter are integrated, and a balance between the instantaneous input power and output power is realized through two switches. The electrolytic capacitor is eliminated, the low-frequency ripple of output current is suppressed, and a high power factor is realized. The working principle of this topology is analyzed in detail, and a control strategy for its circuit topology is put forward. Finally, a 30 W prototype was built, and experimental results verified the feasibility of the proposed topology.

The wide applications of insulated gate bipolar transistors (IGBTs) pose high requirements for their switching performance. However, the conventional gate drive(CGD) has limited regulation effect on voltage and current overshoots in the switching process of IGBTs, because it always sacrifices the switching time and switching loss while reducing overshoots. A novel active gate drive(AGD) control method is proposed to suppress the current and voltage overshoots generated in the switching process of IGBTs, i.e., the driving voltage at the high di/dt and dv/dt stages of IGBTs is adjusted to reduce the changing rates of current and voltage, so as to suppress the current and voltage overshoots. Experimental results show that compared with the conventional driving methods, the proposed method can significantly reduce the current and voltage overshoots in the switching processes of IGBTs without reducing the switching speed or increasing the switching loss.