Research On Wheel-Side PMSM Drive System For Electric Vehicles

Due to the progress of battery technology,the energy density of EV battery has been greatly improved.And the BEV and HEV are currently becoming a hot research area in the field of transportation.Permanent magnet synchronous motor is widely used in EV because of its high power factor,high efficiency,excellent control performance.The main research contents in this paper are control strategy design,hardware circuit design,water-cooling structure design of wheel-side PMSM drive system.Firstly,the mathematical model of PMSM is converted to rotating reference frame.At the frame of vector control strategy,several implementation method of maximum torque per ampere control and field weakening control by look-up table are fully analyzed and introduced.Methods are compared using the parameter of the chosen PMSM,their advantages and disadvantages are analyzed.The simulation test environment for the PMSM system is configured after above steps.Secondly,the design concept of the mechanical structure are described detailly.The components of mechanical structure and the function of each component are illuminated.The reason and the pattern of mechanical structure partition are written in detailed description.In order to satisfy the requirement of mechanical structure thermal analysis,several simplified step are proposed.And this paper presents a simplified method to reduce the order of the IGBT module Foster thermal impedence provided by datasheet for accelerating the convergence velocity of junction temperature and reducing the occupation of computer memory resource in the process of the electric thermal union simulation.Then,the thermal parameters of mechanical structure are derived by Heat Transfer Theory and corrected by results of finite element analysis.On the basis of simulation test environment for the PMSM system,thermal parameters of mechanical structure and thermal parameters of IGBT power module,Union simulation environment of electric and thermal is configured.The junction temperature of IGBT power module can be calculated in case of PMSM working state changing.The temperature rise target of vector transducer shell and the cooling pump lift target are checked simultaneously.The work of heat dissipation design of mechanical structure in this paper solves the following problems below: I:When using finite element analysis method to anlyze the thermal characteristics of the inverter’s mechanical structure,it’s hard to divide the IGBT power module inner structure accurately because of no structure and material parameters provided by manufacturers.And the computing resources are hard to meet when accurate chip temperature change imformations are needed to be acquired and the FEM model is set to run on the time step of power module switching time;II:The designers of inverter electrical part always have limited capability at designing or choosing appropriate heat sink or cooling channel circuit.For example,too much margin are set in low power level applications and the power density is reduced as result.In high power level,too low or not enough margin are set.Insufficient wind pressure at wind cooling or insufficient flow at liquid cooling lead to the incapability of cooling channel circuit to satisfy the power module’s long term operation with high load.And causing the reproduce of the mechanical part and the waste of funds.The main value of heat dissipation design of mechanical structure in this paper is taking the mechanical structure of motor inverters at wheel-side PMSM drive system as a sample to arrange and conclude the heat design work of electrical equipment at each power class.Offering an idea and method to divide and transform the FEM model or 3D CAD model to a lumped heat circuit and to calculate the parameter value of heat circuit.Using the calculated lumped heat circuit and taking the operation condition of cooling circuit as a changing forced convection thermal resistor.Using the lumped circuit to evaluate the cooling channel of electrical equipment at each power class before actual manufacturing can increase the power density at low power level or avoid the remake of mechanical structure and the waste of fundsFinally,the design concept and prototype of the transducer hardware circuit are introduced.the experimental platform of the wheel-side PMSM drive system is built,and the experimental results verify the feasibility of the hardware design.