Design Tools for Power Electronics: Trends and Innovations Uwe DROFENIK * , Didier COTTET ** , Andreas MÜSING * and Johann W. KOLAR * * Power Electronic Systems Laboratory, ETH Zurich, ETH-Zentrum / ETL H13, CH-8092 Zurich, Switzerland Phone: +41-1-632-4267, Fax: +41-1-632-1212, E-mail: drofenik@lem.ee.ethz.ch ** ABB Switzerland Ltd, Corporate Research, CH-5405 Baden-Dättwil, Switzerland Abstract: Numerical simulation is a standard procedure in the design of power electronic systems. With simulation, one can test new concepts immediately without the need to order components and assembling which might be time-consuming and expensive. If something fails, there is no destruction but information about too high voltages and/or currents. Critical operating states just before failure can be exactly reproduced, and currents, voltages and junction temperatures can be easily monitored in simulation which makes it comparably easy to identify problematic designs. Expensive equipment for measurement, power supply and load which is essential for testing prototypes is not needed in a first design stage. Further advantages of simulation are the ability to easily visualize fields, flows and distributions of physical properties, and the ability of automated parameter optimization and/or statistical analysis with Monte Carlo techniques. Due to these advantages it would be desirable to replace designing and testing prototypes by numerical simulations as far as possible in order to reduce development time, save development cost and detect reliability problems. Unfortunately, practical simulation will never fully map reality. The power electronic system under investigation has to be simplified in order to be able to handle the model with a computer. Numerical simulation will always give a result, but it is up to experience and knowledge of the design engineer to verify the usefulness and/or accuracy of the result. In the paper we discuss what can be numerically simulated, what limits are given to modelling by scaling laws and what kind of developments we might experience in the future. Emphasis is on the numerical simulation of converter systems. Keywords: Numerical simulation, multi-disciplinary simulation, PEEC, thermal, EMI, reliability 2. Introduction 1.1 Trends and Requirements What do we want to simulate in power electronics? • Circuits: The design engineer wants to calculate current- and voltage-waveforms of a converter under different operating conditions verifying functionality. All component voltage- and current-levels have to remain within safe value ranges. • Thermal Design / Cooling System: The design engineer is interested in transient semiconductor junction temperatures under different operating conditions (e.g. temporary overload condition), transformer and inductor temperatures, and the performance of different possible cooling systems employing water- or air cooling and/or heat pipes. • EMI-Filter Design: It would be desirable to be able to calculate CM- and DM-noise of the converter system based on the PCB design and simplified models of the semiconductor switches before building and testing an EMI-filter. • Inductive Components: Inductors and transformers are key components in power electronic systems. They significantly contribute to the system losses, system volume and weight. With increasing emphasis on converter optimization, there is a growing desire to employ more realistic non-idealized inductor models in circuit simulations considering iron losses, eddy-currents, skin- and proximity-effects, and thermal behavior. • Optimization: Depending on application, power electronic systems have to be optimized in terms of costs, volume, and/or weight. As example, a design task might be to minimize the heat-sink volume, to minimize the EMI filter weight, to maximize the reliability of the power module, or to maximize the converter’s robustness for a given range of operating conditions. • Reliability / Life Time: According to a study in the electronics industry [1], a significant percentage of all failures in electronic systems are related to temperature issues. Therefore, calculating module and/or converter system reliability based on transient temperatures will become an important feature of power electronics simulation software. What do we demand from simulation software? • Fast processing: Typically, the simulation time should be limited to a couple of hours, because often a large number of simulations is needed to investigate and verify a design before building a prototype. The faster the simulation, the more effective the simulation- based design phase. • High accuracy: Simulators will always give results in terms of time-dependent values, but in case of poor modelling the simulated results will have nothing in common with reality which makes them useless. The design engineer needs experience and good knowledge in modelling and simulation in order to guarantee a certain accuracy of the results. If the simulation software is augmenting the task of setting up realistic models, or provides warnings in case the model and/or the simulation results look faulty, this will significantly improve the quality of this design phase, and will help preventing non-working experimental prototypes. • Multi-Disciplinary: Power electronic applications cover a wide range of frequencies (DC to GHz), dimensions (um to km), temperatures (-55°C to 275°C) and power (mW to MW), and therefore require design tools with extremely broad numerical capabilities. Power electronics is located at the intersection of