In the current automotive electric propulsion system, the thermal design of power modules relies heavily on empirical knowledge, and it is difficult to effectively optimize the irregularly arranged PinFin structure, which limits its performance. In order to give full play to the advantages of SiC devices, this paper classifies and reviews the advantages and disadvantages of various PinFin layouts, thermal simulation methods, and co-design with capacitors and motors in motor drive systems. The research results will provide the necessary support for the development of high-power-density motor drives for future vehicles.
bright spot
1 PinFin Layout and Design Methodology
(1) Rule PinFin layout design
The main principle of PIN design is to improve heat dissipation efficiency by increasing the surface area available for heat transfer. However, while increasing the radius to increase the heat dissipation area, it also increases the flow resistance of the cooling medium.
In practical applications, cooling circulation devices, such as water pumps, do not provide infinite fluid pressure. The dense PinFin design will greatly reduce the flow rate and reduce the effectiveness of convective heat dissipation, and the design needs to balance the heat dissipation area and the differential pressure of the coolant.
(2) Irregular PinFin layout design
In most power module products, the PinFin is arranged irregularly, while the chips are arranged irregularly. SiC chips are smaller in size than silicon chips. The number of PinFin under each chip can vary greatly. The relative position of the pin and the mold is also different. This will significantly affect the temperature uniformity of the parallel chip.
2. Thermal performance evaluation method
(1) Computational fluid dynamics
At present, the thermal design of motor drive systems is mainly based on computational fluid dynamics (CFD), and the overall thermal performance of motor drive systems can be evaluated through manual design. The main advantages of CFD simulation are high calculation accuracy, easy parameter modification, and suitable for manual design.
The main disadvantages of CFD are the long simulation time, frequent convergence problems, and the difficulty of applying automatic optimization algorithms. The number of candidate designs that can be compared in manual design iterations is often limited. It usually doesn't have more than 30 options. In many cases, the design results only meet very basic requirements, which makes it challenging to achieve global optimization.
(2) Faster assessment methods
In order to solve the problem of long solution time, some literatures use analytical and empirical methods to meet the needs of genetic algorithms. Equation-based calculations are fast (< 1us) but have large errors (> 35%).
（3）格子玻尔兹曼方法（Lattice Boltzmann Method, LBM）
Straight LBM is a numerical method for simulating complex fluid states, using the LBGK (Lattice Bhatnagar-Gross-Krook) model to solve the incompressible Navier-Stokes equations. This method does not directly solve the matrix, which is conducive to parallel computing. It can reduce simulation time by 30-60% compared to CFD and has a small simulation error (< 6%).
3. Co-simulation with bus capacitors and motors
(1) Co-simulation with bus capacitor
In a typical motor drive system, there are many components that are spatially independent, but are interconnected in terms of power, heat dissipation, and mechanics. A reduction in the volume of individual components does not directly equate to a decrease in the volume of the entire system. In order to maximize the space utility of the motor drive, co-optimization between components is necessary.
The bus capacitor is the second largest component in the motor controller, and it is a hot topic of research in recent years. Its capacity utilization rate is constantly improving. As the operating frequency increases, it is important to increase the total heat dissipation capacity.
(2) Co-simulation with motors
At present, the mainstream integration methods of motors and controllers in automotive electric drive systems include three methods: up-connecting, side-connected and embedded. In the case of both top-up and side-wire, there is usually a three-phase power module and an integrated DC bus capacitor. In embedded mode, there are multiple low-power modules (> 2) and multiple distributed capacitors around the shaft.
Researchers must precisely control the temperature distribution of motors and drives through collaborative thermal design. It should meet the requirements of various operating conditions and have the potential to improve the utilization of materials.
conclusion
In this paper, in order to better design the thermal management system of power modules in electric vehicle applications, it is necessary to establish an optimization method for irregularly arranged PinFins. The main bottlenecks include the quantitative expression and automatic generation of PinFin layout schemes, efficient evaluation methods, and collaborative thermal design. The main design goals are to reduce the thermal resistance of the crusts, as well as to reduce the temperature difference between the modules. In order to get the most out of the power device through the optimization algorithm, a simplified thermal model needs to be built to maintain relatively small errors and fast speeds.
In the field of PinFin optimization of power modules, cost-effectiveness and manufacturability are key considerations and are often closely tied to the company's expertise. Because the specific cost parameters and manufacturing process are strictly confidential trade secrets, they are rarely disclosed in the public technical literature.
Meet the team
Founded in 1997, the High Power Density Electric Drive and Electric Vehicle Technology Research Department of the Institute of Electrical Engineering of the Chinese Academy of Sciences is an important part of the "Key Laboratory of Power Electronics and Electric Drive" of the Chinese Academy of Sciences.
The research department has undertaken and completed dozens of national and local important scientific and technological research tasks related to electric vehicles, and is in a leading position in the field of motor drive research for new energy vehicles in mainland China, and has an important influence at home and abroad.
Since the "Ninth Five-Year Plan", it has taken the lead in the development of basic theories and key technologies for high-power density motor drives in China, presided over the research and development of the mainland's first digital AC motor drive system for electric cars, the first set of electricity-electric hybrid energy power system for fuel cell light buses, and the key technologies of high-performance permanent magnet motors and drive systems developed have been applied to the 2008 Beijing Olympic Demonstration, the 2010 Shanghai World Expo Demonstration, the "Ten Cities and Thousand Vehicles" demonstration and the promotion of new energy vehicles. It has produced good social and economic benefits, published more than 400 articles, applied for 71 patents, and won the first prize of science and technology of China Electrotechnical Society in 2012 and the first prize of technology invention award of China Power Supply Society.
The R&D department has grown in tandem with the new energy vehicle industry and has played a leading role in the development of electric drive technology for electric vehicles. During the "13th Five-Year Plan" period, the research department led the cooperation teams of domestic first-class universities and leading enterprises to obtain the support of the national key R&D program to carry out multidisciplinary joint research on SiC devices and their applications in electric vehicles.
Representative achievements include: the establishment of the "High-frequency Field Control Power Device and Device Product Quality Inspection Center", which is currently the first testing institution in China that can test high-power semiconductor products and obtain CNAS certification; The "Beijing Engineering Laboratory for High-power Power Electronic Device Packaging Technology for Electric Drive System" was established, and it was evaluated as "excellent" in 2016. After ten years of hard work, the flywheel generator and controller products have participated in the celebration of the 70th anniversary of the National Day. The prototype of the all-SiC motor drive controller (37kW/L) with the highest power density in China has been developed, and it was rated as one of the top ten cutting-edge technologies of new energy vehicles in the world at the 2019 World New Energy Vehicle Conference.
About the Author:
Ning Puqi, doctoral supervisor, researcher of Institute of Electrical Engineering, Chinese Academy of Sciences. He graduated from the Department of Electrical Engineering of Tsinghua University in 2004 with a bachelor's degree in engineering, graduated from the Department of Electrical Engineering of Tsinghua University with a master's degree in engineering in 2006, and received a doctorate degree in electrical and computer engineering from the Department of Electrical and Computer Engineering of Virginia Tech University in United States in 2010. From 2010 to 2013, he worked as an associate researcher at Oak Ridge National Laboratory in United States. In 2013, he joined the Institute of Electrical Engineering, Chinese Academy of Sciences as a researcher. It is mainly engaged in the packaging development of high-temperature silicon carbide devices and high-power density all-silicon carbide.
Xiaoshuang Hui is a Ph.D. candidate at the University of Chinese Academy of Sciences. Since 2021, he has been studying for a Ph.D. in the High Power Density Electric Drive and Electric Vehicle Technology Research Department of the Institute of Electrical Engineering, Chinese Academy of Sciences, focusing on multiphysics modeling and integrated optimization of high power density silicon carbide motor controllers.
Kang Yuhui graduated from Shijiazhuang Railway University in China in 2015 with a bachelor's degree in electrical engineering and automation. He received a master's degree from the Institute of Electrical Engineering, Chinese Academy of Sciences in 2019. His main research direction is power electronic device packaging technology.
Dongrun Li received his bachelor's degree from the School of Electronic, Electrical and Communication Engineering of the University of Chinese Academy of Sciences in 2022 and is currently pursuing a master's degree at the Institute of Electrical Engineering, Chinese Academy of Sciences. His research interests are the automatic optimization of motor controllers for electric vehicles.
Yang Jiajun, received a bachelor's degree from the School of Electrical and Information Engineering of Changsha University of Science and Technology in 2023, served in a unit of the Eastern Theater Air Force from 2018 to 2020, and is currently studying for a master's degree at the Institute of Electrical Engineering, Chinese Academy of Sciences. His research interests are the evaluation of the heat dissipation performance of electric vehicle motor controllers.
Zhaohui Liu received his bachelor's degree in automation from North University of China in Taiyuan, China in 2006, his master's degree in mechanical engineering from Beihang University, China in 2011, and his Ph.D. in electronic and electrical engineering from the University of Sheffield, United Kingdom in 2017. From 2017 to 2020, he worked in the research, design and development department of Malmesbury Dyson Technologies Ltd., United Kingdom, as a senior engineer in 2017 and a senior engineer in 2018. He is currently the Chief Engineer and Head of Powertrain at the National New Energy Vehicle Technology Innovation Center in Beijing, China.