IGBT modules for HEV/EV market based on Ansoft simulation-EEWORLD

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Faced with the highly competitive hybrid and electric vehicle (HEV/EV) market, power integration R&D engineers are challenging themselves to achieve higher system efficiency, stability and reliability. The power inverter is crucial in the power integration system and is usually composed of six 4×6-inch packaged IGBT modules. These IGBT modules output AC power to the motor, control the electronic system and other systems by quickly switching hundreds of amperes of current on and off. The switching frequency of IGBT ranges from tens of kHz to hundreds of kHz, and the turn-on rise time and turn-off fall time are 50~100ns. The high switching speed makes IGBT very suitable for power inverter systems, but it also brings two major electromagnetic problems: conducted radiation (through current-carrying structural parts) is usually less than 30MHz, which may cause power integrity problems or cause energy reflection waves that are potentially harmful to the inverter and motor; radiated electromagnetic fields (through air) are usually higher than 30MHz, which may affect other electronic systems on the vehicle. In order to meet government and international vehicle electromagnetic radiation standards, the above two types of interference problems must be fully considered in the design. Therefore, responsible engineers must design the electromagnetic compatibility and electromagnetic interference of the basic structural parts of the system. To complete the EMC and EMI design of power inverter systems, engineers must first address the underlying physical factors that determine EMC and EMI, and then complete the design with the help of circuits and systems. This simulation-driven approach facilitates handling other electromagnetic issues that must be considered, including current quality, power consumption, and overall system efficiency. These calculations, which are usually performed using linear circuit elements and simplified circuit solvers, require a lot of rough approximations and overly simplified assumptions. Skipping the simulation of these critical basic physical mechanisms, the simulation results will no longer be correct, and hardware prototype testing - multiple iterations of redesign may be required before performance requirements are met. In most cases, these test cycles cannot be performed until the late stage of the design process, which will seriously increase costs and miss market opportunities. To be able to predict electromagnetic effects in the early stages of development before the power inverter is manufactured, it is impossible without simulation of multi-physics domain problems. Ansoft software packages provide full-frequency domain multi-physics problem analysis tools for electromagnetic performance research of devices such as IGBTs. Ansoft software specializes in electromagnetic field simulation, and can also simulate circuits and systems. Ansoft tools available for power inverter development include: Simplorer: A multi-domain circuit and system simulator that easily integrates multi-physics domain simulation components such as electrical, thermal, mechanical, magnetic and fluid. Q3D Extractor: A quasi-static electromagnetic field solver that can be used to calculate frequency-dependent resistance, inductance, capacitance and conductivity parameters in current-carrying structures. HFSS: A finite element-based full-wave solver that can be used to extract parasitic parameters and display three-dimensional electromagnetic fields. To accurately describe the performance of switching devices such as IGBTs, engineers usually start with a parameterized wizard that can import IGBT performance curves and tabular data from performance sheets provided by suppliers. The data processing program automatically extracts the required parameters (about 140) to generate the semiconductor circuit model of the IGBT without manual work. Then, the design layout of the power converter can be directly imported from CAD software or layout design tools into the Q3D Extractor tool. Q3D Extractor calculates the frequency-dependent resistance, partial inductance and capacitance of the conductive path from the design layout. Engineers then use the tool to generate an equivalent circuit model in preparation for system simulation in Simplorer. Once the model is built, it can be combined with the semiconductor circuit model to form an electrical integrity model of the IGBT. The electrical integrity model can be used for conducted radiation analysis of the power supply, control system and load. The results of this simulation can be used by HFSS to verify radiated emissions - a type of radiation that is of particular concern given the frequency domain harmonics caused by fast switching time series. To determine this effect, the results of Simplorer can be used as input to the HFSS full-wave electromagnetic solver. Engineers can then fully understand its radiated electromagnetic field and can calculate the electromagnetic field strength at any given point in space and determine whether the inverter package meets the relevant standards. In this way, engineers can use the tools provided by Ansoft to design the electromagnetic compatibility and electromagnetic interference of the inverter system and trace its electromagnetic performance back to the layout design of the inverter. From this, parameter changes are made to the design and a series of simulation results are obtained until the conducted radiation and radiated electromagnetic emission levels are within acceptable limits. The value of this approach is that once the model is completed, the design can be modified by changing a few key parameters, which allows engineers to study various parameter options and explore a wide range of what-if analysis. This approach can provide a fully optimized design that meets performance requirements before any hardware is built. Compared to the prototype-prototype test model, the multi-physics simulation method can save time and money and enable companies to compete in the market with better designed products.

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