Di Han

Comprehensive Efficiency, Weight, and Volume Comparison of SiC- and Si-Based Bidirectional DC–DC Converters for Hybrid Electric Vehicles

Silicon carbide (SiC)-based switching devices provide significant performance improvements in many aspects, including lower power dissipation, higher operating temperatures, and faster switching, compared with conventional Si devices. However, tradeoffs in efficiency, size, and weight between Si- and SiC-based converters are still unclear in the literature. In this paper, a bidirectional dc-dc converter that is suitable for hybrid or electric vehicle application is studied based on three sets of device combinations, e.g., all-silicon [conventional silicon insulated-gate bipolar transistors (IGBTs) and silicon PN diodes], hybrid (silicon IGBTs with SiC Schottky diodes), and all-SiC (SiC metal-oxide-semiconductor field-effect transistors with SiC Schottky diodes). At the switching frequency of 20 kHz, comparative analyses regarding the power loss reduction of power devices and efficiency improvements are carried out for the converters. Possible size and weight reduction is also investigated by increasing the operating frequencies of hybrid and all-SiC converters while reducing the capacitance and inductance values.

Analysis of a SiC three-phase voltage source inverter under various current and power factor operations

Due to the superior physical properties of Silicon Carbide (SiC) material, SiC MOSFETs and Schottky diodes are becoming available for voltages higher than 600 V, which has been dominated by conventional silicon (Si) IGBTs and P-N diodes. Compared to the Si devices, SiC devices excel in many areas such as faster switching speed, lower conduction and switching losses, and higher temperature capability. This paper thoroughly investigates the performance of a 12 kVA SiC-based three-phase voltage source inverter in simulation. The proposed inverter is first compared with a conventional Si inverter of the same rating under given loading conditions. In addition, high frequency operations up to 100 kHz are investigated. Finally, the SiC inverter is evaluated for different load currents and power factor angles. Loss and efficiency values for each case are calculated and reported.

Deadtime Effect on GaN-Based Synchronous Boost Converter and Analytical Model for Optimal Deadtime Selection

It is widely acknowledged that gallium nitride (GaN)-based power switching devices are superior to conventional silicon (Si) devices in terms of lower semiconductor loss and faster switching speed. However, the deadtime related losses in GaN HEMT-based converters can be detrimental if not optimized, especially when operating at very high switching frequencies. This paper proposes an original analytical model for deadtime optimization for the GaN converters. The proposed model is more accurate than conventional deadtime optimization methods used in Si converters. A GaN-based synchronous boost converter is used as a case study. Circuit simulation and experimental tests are successfully performed to verify the analysis and proposed model.

Efficiency comparison of SiC and Si-based bidirectional DC-DC converters

With the advancement of technology on wide bandgap materials such as silicon-carbide (SiC), there are now better choices of SiC power devices available than ever before. It is widely known that SiC-based switching devices provide significant performance improvements on many aspects including lower power dissipation, higher operating temperatures, and faster switching frequencies compared to conventional Si devices. However, the tremendous benefits of SiC devices have not yet been fully explored by researchers. In this paper, a popular topology of bidirectional DC-DC converter that is suitable for hybrid vehicle or electric vehicle applications is considered. Comparative analyses regarding the power loss reductions of power devices and efficiency improvements are carried out for the converter based on three sets of device combinations, e.g. all-silicon (conventional silicon IGBTs and diodes), hybrid (silicon IGBTs with SiC Schottky diodes), and all-SiC (SiC MOSFETs with SiC Schottky diodes).

Efficiency characterization and thermal study of GaN based 1 kW inverter

Rapid advancement of gallium nitride (GaN) based device technologies enables the possibility to design inverters that have superior performance capabilities compared to Si-based inverters. It is prevalently acknowledged that GaN-based switching devices outperform the Si-based counterparts in many aspects such as lower power consumption, and faster switching frequencies. GaN devices will benefit many applications such as hybrid and plug-in electric vehicles, solar power inverters, industrial motor drives, and aerospace. Nevertheless, the superiorities of GaN devices in inverter design have not been fully explored by researchers, and the purpose of this paper is to evaluate the high-efficiency capabilities of inverters that can be achieved using these new devices and the resulting benefits on the thermal aspect. As a case study, 1 kW GaN FETs inverter is considered. Loss and efficiency analysis is performed under various load conditions, and the requirements on heat sink for various ambient temperatures are specified according to the loss values obtained. Analysis results are compared with conventional Si-based inverters.

Analysis of SiC based power electronic inverters for high speed machines

Silicon carbide (SiC) based power switching devices have been extensively studied by researchers and engineers in recent years because of their superior physical properties compared to silicon. However, the benefits of using SiC devices have yet to be fully explored, especially for high-speed or high-fundamental frequency motor drive applications. Hence, this paper contributes to the understanding of the benefits of SiC inverters as applied to high-speed or high-fundamental frequency drives. This research investigates the high switching frequency capabilities of SiC inverter to improve the performance of high-speed machines or high fundamental frequency operation and achieve lower weight and volume of the both motor and inverter.

Analysis of High-Speed PCB With SiC Devices by Investigating Turn-Off Overvoltage and Interconnection Inductance Influence

The purpose of this paper is to analyze the impact of interconnection inductances to overvoltage during turn-off transient of silicon carbide (SiC) devices. To understand the switching behavior of the SiC devices, the ringing and overshoots of the voltage caused by the device capacitance and interconnection inductances are considered. Parametric studies are conducted to compare the influences of printed circuit board (PCB) and packaging inductances on the peak turn-off overvoltage under various operating conditions. A prototype half-bridge buck converter with SiC MOSFETs is constructed for the experiments. Experimental results are shown to validate the simulation results.

Reduction of Common Mode Voltage and Conducted EMI Through Three-Phase Inverter Topology

This letter presents a three-phase voltage source inverter (VSI) topology to reduce the common mode (CM) voltage and electromagnetic interference (EMI) of electric motor drives. Instead of using filters, active or passive, or specific pulse width modulated (PWM) techniques to reduce the CM voltage, the proposed topology has inherently less CM voltage generation. With the addition of two switches placed in series on the dc lines, this topology effectively reduces the CM voltage during zero switching states by “floating” the inverter from the dc source. This topology can be implemented with any PWM method and does not add any additional complexity to the standard control techniques. The operation and CM reduction capability of the topology is first demonstrated in simulation and then verified with experimental results. A comparison of both common mode voltage and EMI is made to a conventional three-phase VSI to demonstrate the effectiveness of the proposed topology.

Common-Mode Voltage Cancellation in PWM Motor Drives With Balanced Inverter Topology

This paper proposes a novel inverter topology for canceling the common mode voltage of motor drives, and thus reducing or eliminating the ground leakage current, bearing current, and common mode electromagnetic interference. The proposed topology splits one of the switches on each phase-leg of a conventional inverter into two half-voltage rated switches, and creates two complementary sets of balanced three phase output voltages, whose common mode voltages cancel each other in the driven motor, and is named as “balanced inverter”. The balanced inverter topology does not involve additional passive components, modification of the modulation strategy, or increase of the total device rating. Theoretical analysis, simulation, and testing results are presented to verify this concept.

Comprehensive Study of the Performance of SiC MOSFET-Based Automotive DC–DC Converter Under the Influence of Parasitic Inductance

With low loss, fast switching speed, and high-temperature capabilities, silicon carbide (SiC)-based devices are beneficial to automotive power converters in terms of efficiency increase and size reduction. Nevertheless, as a result of fast switching transitions and low on-state resistance of SiC devices, SiC-based converters are prone to overshoots and oscillations on switching waveforms, with the presence of parasitic inductances in the circuit. The overshoots and oscillations further contribute to increased converter loss and EMI emissions. This paper aims to study the influence of parasitic inductances on the performance of SiC MOSFETs for automotive dc-dc converters from the loss and electromagnetic interference perspective.