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.

In a closed-loop control system, the aging monitoring method for power devices based on electrical parameters is one of the difficulties in the field of power electronics reliability. The direct torque control (DTC) system of a permanent magnet synchronous motor (PMSM) is taken as an example, and an on-line monitoring method for the aged state of power devices in a power inverter is studied based on the phase diagram of flux linkage and current. First, the aged characteristics of power devices are analyzed, and it is concluded that the on-state resistance will increase due to the aging of bond wires. Second, the relationship between power device bond wires aging and the phase diagram of flux linkage and the relationship between aging and direct axis current and three-phase current peak value are studied, and the aging monitoring methods are proposed accordingly. Finally, through several groups of simulation experiments, it is verified that both the monitoring method based on the phase diagram of flux linkage and the monitoring method based on current can realize on-line monitoring of the aged state of power device bond wires in the power inverter. The monitoring method based on the phase diagram of flux linkage is easy to observe when there are some fluctuations in the system flux, so it is not desirable considering that the power device has already been in a failure state at the same time. In comparison, the monitoring method based on three-phase current can more accurately monitor the aged state of power devices, and its effect is more advantageous.

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.

Under certain parameters, a permanent magnet synchronous motor (PMSM) will exhibit nonlinear chaotic behavior, which is mainly manifested in torque and speed oscillation, resulting in unstable system performance. Under this background, a sliding mode control (SMC) experiment was carried out on an actual motor platform. After a reasonable process of data, the corresponding system phase diagram was drawn, and it was compared with that without SMC, thereby verifying the chaotic phenomenon from another point of view. Based on the analysis model of chaotic motion of PMSM, the chaotic dynamic behavior of PMSM was studied theoretically by using the stability theory and equilibrium point properties. It was found that the experimental results were consistent with the numerical simulation, which verifies the existence of chaos and the correctness of theoretical analysis and shows that SMC has a better inhibitory effect on the chaotic phenomenon.

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.

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.

Owing to its obvious advantages such as high control flexibility, no commutation failure and strong dy-namic reactive power support capability, the voltage sourced converter based high-voltage direct-current (VSC-HVDC) transmission technology has been widely applied in scenarios including point-to-point transmission, back-to-back inter-connections and DC grids. As a core piece of equipment in VSC-HVDC transmission engineering, the VSC valve achieves AC/DC energy conversion through frequent switching of power electronic devices. In this paper, the key design requirements for VSC valves in different application scenarios are systematically summarized by combining with practical experiences accumulated in engineering, the commonly used power devices and VSC valve topologies in VSC-HVDC transmission engineering are compared and analyzed, and their development trends are projected. In addition, different schemes for two typical application scenarios in the future are also compared, providing reference for the applications of VSC-HVDC transmission technology in high-voltage, large-capacity and long-distance transmission scenarios.

The advancements in research on automotive power device packaging have significantly improved the dynamic performance and driving range of electric vehicles, making them more efficient and reliable. With the continuous optimization of automotive power device packaging, the electric vehicle industry is expected to embrace a broader market prospect and development space. In recent years, power device packaging modeling, packaging structure and optimization, thermal management and junction temperature monitoring, gate drive and applications, reliability analysis, and online monitoring have become current research hotspots and have received sustained attention from both the academic and industrial sectors. To promote discussions on the challenges and hot issues related to automotive power devices packaging and their applications, a special issue titled "High Reliability Power Device Packaging and Assistant Technology in EV Application" has been launched in the Journal of Power Supply.

Accurately obtaining the electromagnetic characteristics of high-voltage and high-power switching devices is crucial for predicting the electromagnetic interference in a system in which the devices are located. Research is focused on an equivalent method of switch waveforms for analyzing the electromagnetic characteristics of high-voltage and high-power switching devices. Aimed at the problem that the existing equivalent waveforms are too ideal to reflect the complex spectral components in the switching transients of devices, an analytical model for the electromagnetic characteristics of devices considering their switching processes is proposed. Starting from the time-domain analytical formula for the analytical model and based on the Fourier transform theory, the frequency-domain analytical formula for the analytical model is derived, and the spectral envelope characteristic parameters are analyzed to obtain the spectral characteristics of the analytical model. The theoretical analysis was verified by using the measured switching waveforms of Si IGBT and SiC MOSFET devices.

With the widespread applications of insulated gate bipolar transistors (IGBTs) in power electronic systems, the accurate acquisition of junction temperature which affects their reliability has become crucial. However, one of the main forms of module failure is the aging of the solder layer, which can have a significant impact on the junction temperature. To accurately estimate the junction temperature, the advantages of two traditional thermal network models (i.e., Cauer and Foster) are combined in this paper, and an interface method for the two models is studied, so that the combination is completed. The aging of the chip solder layer is taken into account, and a hybrid thermal network model is proposed. Finally, through the comparison of finite element simulation and experimental test with the calculation results of the hybrid thermal network model, it is verified that the hybrid thermal network model can achieve an accurate junction temperature estimation, providing a basis for monitoring the operating status of the module.