Saber Simulations Research Articles

Parasitic-Based Active Gate Driver Improving the Turn-On Process of 1.7 kV SiC Power MOSFET

This article discusses an active gate driver for a 1.7 kV/325 A SiC MOSFET module. The main purpose of the driver is to adjust the gate voltage in specified moments to speed up the turn-on cycle and reduce the amount of dissipated energy. Moreover, an adequate manipulation of the gate voltage is necessary as the gate current should be reduced during the rise of the drain current to avoid overshoots and oscillations. The gate voltage is switched at the right moments on the basis of the feedback signal provided from a measurement of the voltage across the parasitic source inductance of the module. This approach simplifies the circuit and provides no additional power losses in the measuring circuit. The paper contains the theoretical background and detailed description of the active gate driver design. The model of the parasitic-based active gate driver was verified using the double-pulse procedure both in Saber simulations and laboratory experiments. The active gate driver decreases the turn-on energy of a 1.7 kV/325 A SiC MOSFET by 7% comparing to a conventional gate driver (VDS = 900 V, ID = 270 A, RG = 20 Ω). Furthermore, the proposed active gate driver lowered the turn-on cycle time from 478 to 390 ns without any serious oscillations in the main circuit.

Emulator Based on Switching Functions for a Dual Interleaved Buck-Boost Converter

Under the unavailability of some components of a complex system, the Hardware In the Loop (HIL) tool allows the emulation of other subsystems. When these devices are not available, a customized emulator can be developed based on the Piecewise Linear Model (PWLM) and a numerical method for solving the differential equations system. However, these implementations require the use of a Field Programmable Gate Array (FPGA) with extensive hardware resources. In this article we propose the use of switching functions for the modeling of power converters of a Hybrid Power System (HPS), allowing the reduction of hardware resources of the FPGA, and the number of steps per switching cycle is increased. The results are compared with SABER simulations and a PWLM evaluated with the Euler method.

Zero-Voltage Switching Operation of Transformer Class-E Inverter at Any Coupling Coefficient

This paper presents a complete design methodology of a Class-E inverter with a loosely coupled transformer under zero-voltage switching conditions. At a selected maximum coupling coefficient, the inverter satisfies both zero-voltage switching (ZVS) and zero-derivative switching (ZDS) conditions to achieve a high efficiency. As the coupling coefficient is decreased from its maximum value to zero, the inverter satisfies the ZVS condition over a wide range of load resistance. The proposed method absorbs the magnetizing inductance and the leakage inductance into the inverter topology. The closed-form expressions for all the Class-E inverter parameters are derived in terms of the coupling coefficient, including: 1) input impedance of the transformer with a complex load impedance; 2) equivalent phase of the resonant circuit for both nominal and suboptimum operations; and 3) slope of the switch voltage waveform. The relationship between the voltage slope and the coupling coefficient is introduced, which indicates the proximity of the operating point from ZVS and ZDS conditions. A design example of the Class-E inverter is presented to achieve both ZVS and ZDS, at an optimum coupling coefficient of 0.77, and ZVS condition for any coupling coefficient lower than 0.77 and over a wide range of load resistance. Saber simulations and experimental results are given to validate the soft-switching capabilities over a wide range of the coupling coefficient and load resistance. The theoretical results were in good agreement with Saber simulations and experiments.

A Novel Step-Up Converter with an Ultrahigh Voltage Conversion Ratio

A new step-up converter with an ultrahigh voltage conversion ratio is proposed in this paper. Two power switches of such a converter, which conduct synchronically, and its output voltage, which has common ground and common polarity with its input voltage, lead to the simple control circuit. No abrupt changes in the capacitor voltage and the inductor current of the proposed step-up converter mean that it does not suffer from infinite capacitor current and inductor voltage. Two input inductors with different values can still allow the proposed step-up converter to work appropriately. An averaged model of the proposed step-up converter was built and one could see that it was still fourth-order even with its five storage elements. Some theoretical derivations, theoretical analysis, Saber simulations, and circuit experiments are provided to validate the effectiveness of the proposed step-up converter.

Analysis of quasi-square-wave operation of DAB DC–DC converter

This work makes a novel contribution to the analysis of quasi-square-wave operation of dual-active bridge (DAB) converter by deriving equations for root mean square (RMS) and average device currents and RMS and peak inductor/transformer currents – these equations are useful in predicting device and passive component losses. Quasi-square-wave operation of the DAB converter is verified through Saber simulations and experimentation, validating the mathematical analysis. It is observed that quasi-square-wave mode improves average power transfer and the converter efficiency besides enhancing its soft-switching region without introducing additional passive components. The effect of quasi-square-wave on RMS and peak currents of devices and transformer/inductor is also discussed.

High Temperature Stability and the Performance Degradation of SiC MOSFETs

SiC MOSFET devices have great potentials in future high temperature power electronics applications due to their possible higher thermal runaway temperature compared with other SiC power semiconductor devices. In this paper, the high temperature stability of SiC MOSFETs is investigated by experiments and Saber simulations. The maximum steady-state junction temperature of the SiC MOSFET is measured to exceed 250 °C and saber simulations based on experimental model estimate that the thermal runaway temperatures are close to 300 °C. In addition, performance degradation of SiC MOSFETs during high-temperature operation is observed and discussed. Experimental results show that the degradation happens during both the high temperature storage (maximum 5% RON increment) and high temperature operation process (maximum 15% RON increment). The degradations are found to recover to a close-to-initial level after 1 h recovery time at the room temperature.

Arctan Power–Frequency Droop for Improved Microgrid Stability

The term microgrid is usually reserved for a modest sized, local distributed generation network that will largely operate standalone (i.e., without a grid connection.) The most common power flow control method utilized in a standalone microgrid is a technique known as power-frequency droop. This paper introduces the concept of utilizing an arctan function for the power-frequency droop profile. The use of this arctan function improves the small signal stability of the two-inverter microgrid, provides natural frequency bounding, and is flexible in its application. SABER simulations are performed to obtain the operating points about which the system is linearized for the stability analysis. Experimental results obtained from a dSPACE-controlled, low-voltage, two-inverter hardware system are presented to verify the theoretical and simulation results.

A Simplified Prediction Method for EMI Generated by Three-Phase PWM Rectifier

A simplified method for the calculation of Common-mode (CM) electromagnetic interference (EMI) caused by Three-phase PWM rectifier is presented. EMI analysis in time domain presents particular problems due to complex geometry and the wide range of time constants involved. This makes the simulation of EMI a complex matter. The method presented here is based on a “Matrix representation” process and is specially designed to simplify the mentioned problems. In this paper, quick and robust simulations were preferred rather than very accurate results. Once the disturbances sources are calculated parameters of the propagation path can be changed giving a new prediction immediately. To evaluate the performances of this analytical approach the frequency-domain model is compared with Saber simulations.

Advanced common control method for shunt and series active compensators used in power quality improvement

An advanced common control method for shunt and series active conditioners, which compensate for the main types of disturbances in electrical power systems, is considered. If shunt and series actives conditioners are already well known as good compensation solutions for power quality improvement, it is also admitted that they generate some undesired components at switching frequency. To avoid these propagation problems, conditioner designers proposed a high-order output filter associated to a specific controller based on the RST control method. However, by applying this controller, it can be observed that a phase lag between the reference and the injected signal appears in the current and voltage control loop, which damages harmonic compensation. Therefore, a new RST controller is proposed, called RSTimp, to overcome the phase lag effects over the entire bandwidth for both active conditioners. The RSTimp proposed control method is validated through SABER simulations. These simulations show very good active conditioner performance in terms of rapidity, tracking and robustness for both current and voltage compensation.

Pull-in time–energy product of electrostatic actuators: comparison of experiments with simulation

Measurements of voltage and current transients of a scaled model of an electrostatic microactuator have been performed. Experiments were made at a variety of values of the actuation source resistance, and the effects on the pull-in time and on the energy consumed in a switching event were analysed. It is concluded that the pull-in time remains sensibly constant until source resistance values are reached corresponding more closely to current-controlled than to voltage-controlled actuation. Furthermore, the energy consumed per switching event monotonically decreases with increasing source resistance. There is an optimum source resistance at which a minimum can be found for the product of pull-in time and energy in agreement with earlier theoretical predictions. The experimental results are quantitatively compared with Saber simulations incorporating an analog hardware description language model for the actuator.

One-dimensional analytical modeling of the VDMOS transistor taking into account the thermoelectrical interactions

We have modeled the influence of temperature on power Mosfet transistor behavior (vdmos transistor) in transient and static modes. The model we have developed is able to take into account temperature effects. Temperature is an interactive variable during the Saber simulations. With it, the designer knows the silicon chip temperature for a given application, and its influence on circuit performance or on the trend of a model parameter.