Switching Transient Process Research Articles

Field Stop (FS) Type IGBT Transient Temperature Characteristics: E-Thermal Simulation Approach

This research presents an electro-thermal simulation method for analyzing the transient temperature characteristics of Field Stop (FS) type Insulated Gate Bipolar Transistors (IGBTs). The method combines IGBT working principles and semiconductor physical principles to investigate the influence of internal excess carrier lifetime on the IGBT's transient temperature behavior. By conducting actual tests on an FS type IGBT switching transient working process, the research establishes an electro-thermal simulation method with improved accuracy and simplified parameter calculation.

Analysis of time‐frequency characteristic parameters of electromagnetic interference sources in the basic commutation unit

Establishing accurate electromagnetic interference (EMI) sources of the basic commutation unit is the key to accurately predicting the EMI of the converter equipment. To compensate for the insufficiency of the reported works, that is to use asymmetric trapezoidal waveforms (ATW) as common mode (CM) and differential mode (DM) EMI sources, this paper analyzed the switching transient process of insulated gate bipolar transistor (IGBT) device in the basic commutation unit, and then proposed the equivalent waveform of EMI sources with multi-polylines-damped oscillation waveform (MP-DOW). The spectrum envelop characteristic parameters of MP-DOW were obtained by the frequency domain analysis method, and its correctness was experimentally verified. Comparison with the reported works shows that the proposed spectrum envelope of MP-DOW can take into account the voltage and current overshoot during the switching transients of IGBT devices, and the spectrum characteristic parameters are more accurate. This paper is beneficial to the prediction of EMI for the converter already in operation, and can also provide theoretical guidance for the converter to be designed in conjunction with the analytical formula of the EMI source.

A Periodic-Steady-State Analysis Model in Time Domain for Dual Active Bridge Converter

This article forms a multitime-scale modeling method through a time-domain analysis, using both ideal steady-state processes and finite switching transient processes for increased accuracy of dual active bridge (DAB) converters. All possible operating modes and the corresponding state equations are derived from the switching transient process for a five-degrees-of-freedom-modulated DAB converter based on the unified equivalent circuit. The nonlinear parasitic capacitors are considered in this process. A periodic-steady-state analysis model is established to accurately predict the residual voltage under incomplete zero-voltage switching. This method is applicable for all phase-shift-modulated DAB converters, and the calculation time is reduced 28–61 times compared with LTspice simulation. Finally, the simulation and experimental results are compared to validate the effectiveness of the model.

A novel multi-physics field optimization method for GaN HEMT circuit design

A device modeling and topology design method suitable for high-power-density and high-temperature applicationare important to develop with the development of devices. A novel multi-physics analysis model based on GaN high electron mobility transistor (HEMT) is proposed in this paper. The coupled electromagnetic and electrothermal model for GaN HEMT is beneficial to simulate a device’s external characteristic waveform affected by different stray parameters in the surrounding. In addition, the proposed method can accurately reflect the switching loss and transient switching process of GaN HEMT.

Motor-Oriented Discrete State Event-Driven Method for Multitime-Scale Simulation of Power Traction Systems

With the development of electric vehicles and high-speed train, the demand for power traction system (PTS) is on the rise. Its stability greatly relies on the performance of power traction converters, whose faults are mainly due to the microsecond- or nanosecond-level switching transient process. To avoid overheat or overvoltage failures, researchers should consider this ultrafast dynamics in power switches during the design phase, preanalyzing transient features such as voltage peak and power loss. Nevertheless, the simultaneous simulation of system dynamics and switching transient, namely multitime-scale simulation, is not easily achievable with current software because of their low efficiency and convergence issue. While the discrete state event-driven (DSED) approach can realize efficient multitime-scale simulation for converters, it is incapable of solving circuits connected with nonlinear elements, e.g., motors. This article demonstrates a motor-oriented interfacing derivative (MID) method for connecting motors with power electronic circuits based on DSED. With this method, a multitime-scale platform capable of simulating large-scale PTSs while providing detailed information such as switching transients is built, which is potentially an accurate and efficient tool for system design. Using this platform, the simulation of modular multilevel converter traction system could be finished 200 times faster than the existing commercial multitime-scale simulation software while being capable of capturing switching transient. The proposed MID method enables an efficient multitime-scale numerical platform for PTSs, which facilitates the overall and iterative design for traction systems, especially those of large scale.

Field analysis of switching transient process on the 35 kV side of a substation connecting to PV plant

To reveal the real causes of two explosion faults of potential transformer (PT) on a substation connecting to PV plant, an on-line monitoring equipment with a sampling rate of 40 MS/s for the transient voltage was installed on the secondary side of the PT. By switching the 35kV bus bar onto the main transformer, the switching transient processes on the PT were obtained. The field measured transient process indicated that the switching transient voltage caused by switch operation induced the resonance between the charging circuit and the PT and the resonance may be the direct cause of the PT explosion. The effective measures to suppress resonance in this substation are proposed.

Analysis of DC bus bar dominant stray parameters based on equivalent calculation models

PurposeThis paper aims to analyze the dominant stray parameters of the DC bus bar and focus on weakening the influence of the stray parameters instead of reducing the value of the stray parameters in DC bus bar while switching. By finding the mechanisms to reduce the effects of stray parameters on switching transient, the simple and straightforward optimization methods could be given for the engineering designer.Design/methodology/approachThe investigations are focused on the equivalent circuit by segmented impedance evaluation in the low-frequency band and the energy propagation by wave impedance evaluation in the high frequency band. This paper proposes an equivalent impedance calculation model to locate the dominant stray parameters in the DC bus bar and takes the energy propagation characteristics using wave impedance into consideration, which can simplify the optimization design of DC bus bar.FindingsAccording to the equivalent circuit and electromagnetic field analysis, this paper proves the existence of the dominant stray parameters in DC bus bar that is widely used on high-power converters and certifies that not all the stray parameters in different areas of DC bus bar have the same effects on switching process, which can give a good guidance for the optimization design of DC bus bar.Originality/valueThe positions of DC-link capacitors, resulting in only part of stray parameters in DC bus bar has more impact during switching, are significant to the DC bus bar optimization design. These stray parameters named dominant stray parameters in this paper play a leading role in the switching transient process. The area of DC bus bar, which is close to IGBTs and far from DC-link capacitors, contains the dominant stray parameters in the switching transient process. Therefore, the distance between DC-link capacitors and IGBTs should be shortened as much as possible. Based on the results, the efficiency for the DC bus bar optimization design could be improved by weakening the influence of the stray parameters, such as reducing the dominant stray parameters only. Therefore, it can save the cost and time of DC bus bar optimization design.

Prediction of Electromagnetic Interference Noise in SiC MOSFET Module

Silicon carbide (SiC) metal oxide semiconductor field effect transistors (MOSFETs) are new generation of power semiconductor devices with higher slew rates. During switching transient process, undesirable switching oscillations occurs in SiC MOSFET modules due to the parasitic elements, such as stray inductances and parasitic capacitances. Based on equivalent circuit models, this brief derives the spectrum of the switching waveform with ringing, and investigates the spectral bounds and the influence of ringing on the spectral content. Through LTSPICE simulation, the spectrum comparison between numerical calculation and the circuit simulation reveals that parasitic elements of SiC MOSFET have significant effect on the high-frequency spectral content. In addition, the experiments are carried out to verify the theoretical analysis.

Analysis of Switching Transient Process in Hybrid Energy Storage System

This paper has introduced two important indexes, turn-off surge voltage (TSV) on power switch and peak positive pole potential (PPPP) of storage batteries, which can be used to evaluate switching transient process of high-voltage energy storage system. Research on them is of great significance to power switch choice and high-voltage isolation design in engineering applications. Power switch response process at the turning off moment and transient process in freewheel stage have been analyzed by the established small-signal model of single power switch; then, a power switch test platform for hybrid energy storage system was built to verify it. Taking pulsed-power supply charging device with a novel inductor of low resistance and high inductance as a research object, this paper has analyzed dynamic process of the TSV and the PPPP at the turning off moment through establishing state space model of the whole system. Comparison shows that the numerical curves match the simulated curves well. Finally, the exactness of the employed model has been further verified in two pulse capacitor charging experiments.

Switching Performance Improvement Based on Model-Predictive Control for Wind Turbine Covering the Whole Wind Speed Range

A wind energy conversion system is mainly operated in a partial-load region and a full-load region. In the partial-load region, the primary objective is to maximize energy conversion efficiency, whereas the main goal is maintaining the output power at the rated level in the full-load region. The two control regions are switched in accordance with prevailing wind speed. However, steep and large changes of generator power, as well as mechanical loads, may be experienced during switching transient, which bring about negative impacts on power system reliability and turbine lifetime. This paper presented an advanced model-predictive control considering switching performance improvement. The proposed method not only achieved the control objectives in both two control regions, but also mitigated uncertain power fluctuations and mechanical loads during control mode switching. This high switching performance benefited from the presented dynamic switching transient process driven by the defined wind speed crossing events. During switching transient, system operating states were transferred along with the proposed dynamic vector. Small-signal analysis was employed to prove the good stability and dynamic performance of the system in switching transients. Simulation and hardware-in-the-loop experimental studies verified the effectiveness of the proposed method.

Modeling and Mitigation for High Frequency Switching Transients Due to Energization in Offshore Wind Farms

This paper presents a comprehensive investigation on high frequency (HF) switching transients due to energization of vacuum circuit breakers (VCBs) in offshore wind farms (OWFs). This research not only concerns the modeling of main components in collector grids of an OWF for transient analysis (including VCBs, wind turbine transformers (WTTs), submarine cables), but also compares the effectiveness between several mainstream switching overvoltage (SOV) protection methods and a new mitigation method called smart choke. In order to accurately reproduce such HF switching transients considering the current chopping, dielectric strength (DS) recovery capability and HF quenching capability of VCBs, three models are developed, i.e., a user–defined VCB model, a HF transformer terminal model and a three-core (TC) frequency dependent model of submarine cables, which are validated through simulations and compared with measurements. Based on the above models and a real OWF configuration, a simulation model is built and several typical switching transient cases are investigated to analyze the switching transient process and phenomena. Subsequently, according to the characteristics of overvoltages, appropriate parameters of SOV mitigation methods are determined to improve their effectiveness. Simulation results indicate that the user–defined VCB model can satisfactorily simulate prestrikes and the proposed component models display HF characteristics, which are consistent with onsite measurement behaviors. Moreover, the employed protection methods can suppress induced SOVs, which have a steep front, a high oscillation frequency and a high amplitude, among which the smart choke presents a preferable HF damping effect.