Transient Current Overshoot Research Articles

Design of a Paralleled SiC MOSFET Half-Bridge Unit With Distributed Arrangement of DC Capacitors

Discrete silicon carbide (SiC) mosfet s are usually connected in parallel to increase their current carrying capacity. However, unequal switching losses and unequal transient current overshoot can limit the maximum switching frequency and maximum current carrying capacity of the paralleled unit. In this article, a paralleled half-bridge unit is proposed to improve the transient current sharing performance, which is characterized by a distributed arrangement of dc capacitors. First, the main causes of the transient current imbalance in traditional power layout are analyzed theoretically for the first time. Then, the traditional power layout is optimized by the ANSYSEM cosimulation techniques to improve the transient current sharing performance. The layout of the gate driver is also optimized to reduce the transmission delay of the gate drive signal. The double pulse tests are carried out to verify the current sharing performance under normal and short-circuit operating conditions. Compared with traditional power layout, the difference in a transient current overshoot of the low-side paralleled SiC mosfet s is decreased significantly from 10.22% to 2.78% and the difference in switching losses is also reduced. A boost converter is constructed based on the paralleled half-bridge unit. A more uniform temperature distribution indicates the improved current sharing performance by optimizing the power layout.

An improved Dynamic Voltage Restorer for power quality improvement

The capacity of the voltage source inverter (VSI) and the values for the link filter connected between the injection transformer and the inverter play a crucial in the design of the DVR. In this research paper, new Dynamic Voltage Restorer (DVR) topology has been proposed. The capacity of the voltage source inverter (VSI) and values of the link filter is small that will improve the compensation capabilities for voltage harmonic, swell and voltage sag mitigation under various fault conditions. The new RLC filter is able to eliminate the switching harmonics. The capacity of the dc supply voltage is reduced when the value of inductance is small. The new DVR topology has high efficiency and the ability to improve the quality of voltage. An outline architecture of the RLC filter parameters for the specific model has been presented. The new DVR topology is modeled and simulated using the PSCAD/EMTDC. The control scheme has good control dynamics with minimum transient current overshoot. The simulation results under transient performance are good.

Prediction and Control of Transformer Inrush Currents

In this paper, we propose a dynamic model of the electrical transformer suitable for the numerical prediction of the inrush currents due to the arbitrary initial excitation of a transformer after a switch-OFF. In particular, the proposed model can be helpful to control strategies to avoid a transient current overshoot, based on the prediction of the residual magnetic flux.

Transient photoresponse and incident power dependence of high-efficiency germanium quantum dot photodetectors

We report a systematic study of time-resolved and power-dependent photoresponse in high-efficiency germanium quantum dot photodetectors (Ge-QD PDs), with internal quantum efficiencies greater than 100% over a broad wavelength, reverse bias, and incident power range. Turn-on and turn-off response times (τon and τoff) are shown to depend on series resistance, bias, optical power, and thickness (WQD) of the Ge-QD layer, with measured τoff values down to ∼40 ns. Two different photoconduction regimes are observed at low and high reverse bias, with a transition around −3 V. A transient current overshoot phenomenon is also observed, which depends on bias and illumination power.

Transient current overshoot to electrostatic probes in continuum, slightly ionized plasmas

A spherical probe is subjected to a potential ramp with rise time of the order of the electron diffusion time, after which, the final potential is maintained constant. The electron current overshoots its final value by an amount proportional to the electron conductivity.