Tristan Evans

Bio: Tristan Evans is an academic researcher from University of Arkansas. The author has contributed to research in topics: Power module & High voltage. The author has an hindex of 8, co-authored 16 publications receiving 188 citations. Previous affiliations of Tristan Evans include Rohm.

Three-Phase LLC Series Resonant DC/DC Converter Using SiC MOSFETs to Realize High-Voltage and High-Frequency Operation

Abstract: SiC MOSFETs are applied to constitute a three-phase, 5-kW LLC series resonant dc/dc converter with isolation transformers. A switching frequency of around 200 kHz for the transistors successfully reduces the volume of these isolation transformers, whereas insulated-gate bipolar transistors (IGBTs) are not capable of achieving such a high switching speed. The high-voltage tolerance of SiC MOSFETs, 1200 V, enables increasing the input voltage up to 600 V. High-voltage tolerance, on the other hand, is not compatible with low on-resistance for Si MOSFETs. A three-phase circuit topology is used to achieve up to 5 kW of power capacity for the converter and reduce per-phase current at the same time. Current-balancing transformers among these three phases effectively suppress a maximum peak current from arising in the circuit, a technique that miniaturizes the input and output capacitances. The conversion efficiency of the converter reaches 97.6% at 5-kW operation.

PowerSynth: A Power Module Layout Generation Tool

Abstract: PowerSynth is a multiobjective optimization tool for rapid design and verification of power semiconductor modules. By using reduced order models for the calculation of electrical parasitics of the layout and thermal coupling between devices, optimal trace layout and die placement can be simultaneously achieved orders of magnitude faster than conventional finite element analysis (FEA) techniques. An overview of the tool, its modeling methods, model validation, and module layout optimization are presented. The electrical and thermal models are validated against FEA simulations and physical measurements of built modules generated from the tool. The FEA comparisons are performed with FastHenry and ANSYS Icepak to evaluate electrical parasitics and thermal behavior, respectively. A sample hardware prototype based on a half-bridge circuit topology is chosen for testing. Excellent agreement between the FEA simulations, experimental measurements, and PowerSynth predictions are demonstrated. Additionally, when compared with conventional simulation runtime and workflow, PowerSynth takes considerably less computation and user time to produce several candidate layout solutions from which a designer may easily balance selected tradeoffs.

Emerging trends in silicon carbide power electronics design

Abstract: The emergence of wide bandgap power semiconductor devices has opened the possibilities of improved electrical performance and power density. Advanced research into wide bandgap power electronics also includes advances in integrated circuit design, semiconductor device modeling, 3D electronic packaging, and computer-aided design of wide bandgap based electronics. These emerging trends are described along with some early results indicating the additional improvements possible in power density. Operation at extreme temperatures also becomes more feasible.

PowerSynth Design Automation Flow for Hierarchical and Heterogeneous 2.5-D Multichip Power Modules

Abstract: As a critical energy-conversion system component, power semiconductor modules and their layout optimization has been identified as a crucial step in achieving the maximum performance and density for wide bandgap technologies (i.e., GaN and SiC). New packaging technologies are also introduced to produce reliable and efficient multichip power module (MCPM) designs to push the current limits. The complexity of the MCPM layout is surpassing the capability of a manual, iterative design process to produce an optimum design with agile development requirements. An electronic design automation tool called PowerSynth has been introduced with on-going research toward enhanced capabilities to speed up the optimized MCPM layout design process. As a part of this continuing research, in PowerSynth v1.9, a constraint-aware layout engine has been developed, which enables integrating heterogeneous components, handling complex geometry, exploring a larger solution space, improved success rate, and providing options for multiobjective optimization algorithms. The layout engine is generic, scalable, and efficient in performing electro-thermal optimizations on both 2-D and 2.5-D power modules. To validate these enhanced design capabilities, a 2.5-D full-bridge power module layout is designed, optimized, fabricated, and tested with measurement results matching closely with model prediction. This result closes the loop in the power electronics design process with an experimentally validated module design automation flow.

Toward Partial Discharge Reduction by Corner Correction in Power Module Layouts

Abstract: As spacing between traces in power modules is reduced to meet increasing power density requirements, partial discharge (PD) starts becoming a threat that can cause insulation breakdown, if not checked. For high voltage applications, PD awareness is particularly important, and this paper describes how various trace shapes play a critical role in the electrical reliability of modules with regard to electrical breakdown. Sharp corners of traces must be avoided, as is generally done for mechanical stability reasons, by filleting the corners. High voltage experiments were performed to confirm the detrimental electrical effects of sharp corners. The degree of improvement by completely avoiding sharp corners was quantified for various trace gaps. Simulations were performed to predict the improvement in terms of E-field concentration with respect to the radius of fillets. Preliminary fillets were implemented in a stand-alone in-house tool called PowerSynth, which is used for electrical and thermal optimization.

Extreme Fast Charging of Electric Vehicles: A Technology Overview

Abstract: With the number of electric vehicles (EVs) on the rise, there is a need for an adequate charging infrastructure to serve these vehicles. The emerging extreme fast-charging (XFC) technology has the potential to provide a refueling experience similar to that of gasoline vehicles. In this article, we review the state-of-the-art EV charging infrastructure and focus on the XFC technology, which will be necessary to support the current and future EV refueling needs. We present the design considerations of the XFC stations and review the typical power electronics converter topologies suitable to deliver XFC. We consider the benefits of using the solid-state transformers (SSTs) in the XFC stations to replace the conventional line-frequency transformers and further provide a comprehensive review of the medium-voltage SST designs for the XFC application.

Energy storage system: Current studies on batteries and power condition system

Abstract: To maximize the introduction of renewable energy, introducing grid energy storage systems are essential. Electrochemical energy storage system, i.e., battery system, exhibits high potential for grid energy storage application. A battery energy storage system is comprised of a battery module and a power conversion module. This paper starts by reviewing several potential battery systems, as well as an advanced aluminum-ion battery that currently has promising prospects in the electrochemical energy storage system. The characteristics of the batteries are reviewed and compared, including the materials, electrochemistry, performance and costs. The application prospect of the batteries is discussed. The paper summarizes the features of current and future grid energy storage battery, lists the advantages and disadvantages of different types of batteries, and points out that the performance and capacity of large-scale battery energy storage system depend on battery and power condition system (PCS). The power conversion system determines the operational condition of the entire energy storage system. The new generation wide bandgap semiconductor for power electronic technology is discussed from the perspective of performance, topology, model and non-linearity and is compared to the traditional silicon-based semiconductor. Finally, the application prospect of the new generation semiconductor technology in the energy storage system is indicated. This paper concludes the application status of the energy storage system in the renewable energy power generation and indicates the critical problems that need to be addressed during the construction and operation of the storage system.

Power Electronic Transformer-Based Railway Traction Systems: Challenges and Opportunities

Abstract: In this paper, power electronic transformer (PET)-based railway traction systems are comprehensively reviewed according to the unique application features and requirements. By comparing PET and conventional line frequency transformer (LFT)-based systems, their pros and cons are summarized. By further reviewing all kinds of PET-based designs from the early concepts to the latest ones in the order of their publication dates, the developing trends are highlighted. By synthetically considering the requirements and the state of the art, the key challenges and opportunities are identified and discussed. It shows that although PET-based systems are still developing and far from mature, they are already superior to LFT-based systems in terms of system weight, efficiency, and functionalities especially for 15-kV/16.7-Hz applications. With the advancements on wide bandgap power devices, medium frequency transformers, and converters, PET systems will be even more promising and available for all types of railway tractions in the near future.

Evaluation of Switching Performance of SiC Devices in PWM Inverter-Fed Induction Motor Drives

Abstract: Double pulse test (DPT) is a widely accepted method to evaluate the switching characteristics of semiconductor switches, including SiC devices However, the observed switching performance of SiC devices in a PWM inverter for induction motor drives is almost always worse than the DPT characterization, with slower switching speed, more switching losses, and more serious parasitic ringing This paper systematically investigates the factors that limit the SiC switching performance from both the motor side and inverter side, including the load characteristics of induction motor and power cable, two more phase legs for the three-phase PWM inverter in comparison with the DPT, and the parasitic capacitive coupling effect between power devices and heat sink Based on a three-phase PWM inverter with 1200 V SiC MOSFETs, test results show that the induction motor, especially with a relatively long power cable, will significantly impact the switching performance, leading to a switching time increase by a factor of 2, switching loss increase up to 30% in comparison with that yielded from DPT, and serious parasitic ringing with 15 μs duration, which is more than 50 times of the corresponding switching time In addition, the interactions among the three phase legs cannot be ignored unless the decoupling capacitors are mounted close to each phase leg to support the dc bus voltage during switching transients Also, the coupling capacitance due to the heat sink equivalently increases the junction capacitance of power devices; however, its influence on the switching behavior in the motor drives is small considering the relatively large capacitance of the motor load