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.

Aimed at the problems of a traditional dual-active-bridge (DAB) converter such as large switching loss, large circulating current, narrow range of load variation and low operating efficiency, a novel power control method for DAB converter based on variable inductance and phase shift (PS) angle is proposed, in which the variable inductance and PS angle are taken as the main control parameters to improve the operating efficiency of the DAB converter in a wider range of load variations. In addition, the transfer function of the DAB converter is linearized to improve the practicality and convenience of the controller. Because the device saturation is controllable in the proposed method, the core size can be reduced to optimize the converter size. Finally, the effectiveness and superiority of the proposed method were verified by experiments. Results show that under the condition of maximum PS angle, the inductance variation significantly affected the power transmission of the DAB converter, and its overall operating efficiency was about 5% higher than that of the traditional DAB converter under both the light and heavy load conditions.

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 dual-active-bridge (DAB) converter is a key device in a bidirectional power transmission system. In this paper, its fundamental operation principle and topologies are reviewed at first. Then, four basic modulation strategies for the DAB converter are introduced, including single-phase-shifted, dual-phase-shifted, extended-phase-shifted and triple-phase-shifted strategies. Moreover, the modeling and optimization methods based on these four modulation strategies are compared and analyzed. Finally, some problems faced by practical applications and the corresponding solutions are discussed. Along with the development of DC power distribution, energy storage and distributed energy resources, DAB converters will have broad application prospects.

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.

At present, the transmitting coil in a dynamic wireless charging system for electric vehicles usually adopts a segmented guide rail structure to realize the relay dynamic wireless charging. However, the problem of mutual inductance drop will occur at the switching of the guide rail and result in the reduction of the system transmission efficiency, and this is more prominent at the corner. A corner dynamic wireless charging model was established, and the relationship between the mutual inductance of primary and secondary coils and the deflection angle was deduced through theoretical analysis. An improved structure of the guide rail transmitting coil at the corner was proposed and simulated, and a corner dynamic wireless charging platform based on resonance magnetic coupling was built. Simulation and experimental results show that by using the improved guide rail transmitting coil structure, the mutual inductance drop of the wireless charging system was significantly reduced, and the system transmission efficiency was improved by 8.66% at the maximum deflection angle, thereby verifying the effectiveness of the improved coil structure.

Aimed at uncertainties in the output from grid-connected wind turbine, the scenario analysis method based on probability occurrence is adopted to transform the uncertainty model into a multi-scenario problem with different occurrence probabilities, and a reactive power optimization model with the goal of minimizing the active power loss and voltage deviation is established. In view of the poor diversity of Pareto frontiers obtained using the traditional methods, an adaptive grid multi-objective particle swarm optimization (AG-MOPSO) algorithm is proposed, which uses adaptive grids to obtain the density of particles in external archives, selects the global optimal particles and maintains the scale of the external storage library according to the density information as well as the betting mechanism, thus effectively ensuring the uniformity and diversity of the Pareto frontier distribution. This algorithm is used to perform reactive power optimization calculations on an IEEE 33-bus system with wind power, and it is also compared with the existing NSGA-II algorithm. Results show that the Pareto frontier obtained using this algorithm is better, which verifies the feasibility of the proposed model and algorithm.

Aimed at the high harmonic content of a model predictive controller (MPC) without modulation modules, a novel model-based variable sampling period MPC strategy is proposed and applied to a five-phase induction motor drive system. The problem caused by the fixed-discretization of time in the MPC is analyzed, but the introduction of modulation or modulation substitution to solve this problem will increase the complexity of the control system. Therefore, a simpler and more natural idea is adopted. Specifically, the sampling interval is changed based on the pursuit algorithm, and the optimal control action and implementation time are determined by combining with the MPC, thus realizing the variable sampling period MPC strategy. Experiments were carried out using the five-phase induction motor drive system, and experimental results verified the excellent reference tracking and current harmonic performance of the novel variable sampling period MPC.

Aimed at the problems in the existing nine-level inverter such as many devices and a complex modulation strategy, a novel switched capacitor nine-level inverter is proposed. The topology of this inverter is composed of only one single DC power supply, nine switches, two capacitors and two diodes, and it can output nine levels and double the boost at the same time. The voltages of capacitors are self-balancing, and the complex control algorithm and external voltage sharing circuit are not required. The phase disposition PWM strategy is adopted to modulate the inverter. The working states of four pairs of switches in the inverter are complementary, and the NOT gate logic circuit can be used to reduce the complexity of the modulation strategy. First, the topology and working principle of the inverter are analysed theoretically. Second, the modulation strategy is introduced in detail, and the advantages of this topology are introduced by comparing it with other nine-level inverters. Finally, the feasibility and effectiveness of the proposed topology and modulation strategy were verified based on the established simulation circuit and experimental platform.

A rapid solution method for the thyristor electro-thermal coupling model based on the conjugate gradient method is developed to address the limitations of traditional solution techniques in terms of processing efficiency and computational cost. By optimizing the iteration process and convergence criteria, the solution efficiency and accuracy are significantly improved. A novel parameter selection strategy is introduced to automatically adjust the algorithm's iteration step size, thus accelerating the convergence speed and reducing the computational resource consumption. Compared with the traditional solution methods, the optimization approach achieves an average reduction of 10% in solution time and an 8% increase in solution accuracy. This progress demonstrates the effectiveness of the adaptive conjugate gradient method in the rapid solution of electro-thermal coupling models, providing an efficient and reliable computational tool for the thermal management of power electronic devices. The proposed method exhibits significant efficiency improvement and good accuracy under various test conditions, offering an innovative solution for efficiently solving the thyristor electro-thermal coupling models. This method is also of practical significance for related research in the field of power electronics.