Development Of EV Converter

The successful development of the third generation rare earth permanent magnet materialNd-Fe-B(Nd-Fe-B), which impetus to the development of permanent magnet synchronousmotor and control system. With the decline in the price of permanent magnet materials andimprovement of magnetic materials, which has been widely used in small and medium-power, high-precision, high reliability and wide speed range of the speed and positioncontrol system, especially get a lot of attention of numerous research and developmentpersonnel in rail vehicles. Control strategy of permanent magnet synchronous motor controlsystem have two main types: the vector control strategies and direct torque control strategy.In this paper, There are a larger series of questions that the control period will be longer,the motor stator inductance is small, the process of the motor starts and load changes, theimpact of large motor current, flux and torque ripple and so on in direct torque control forpermanent magnet synchronous motor. Vector control use SVPWM modulation method,which has superior system performance, anti-interference characteristics, start brakingcharacteristics, steady speed characteristics meet or exceed the DC motor speed controlsystem.Meanwhile, since the vehicle power capacity limit, the maximum torque currentvector control strategy than has been extensively studied and adopted. Compared with id=0vector control strategies, the maximum torque current torque in the same conditions, theoutput current is small, reducing the loss ratio of permanent magnet synchronous motorvector control strategies, making at the same power level, the motor can get more ratedspeed.However, in the actual control system, when the reference torque is known, through therelationship between current and torque to the size of the current anti-solution is very difficult,very large amount of computation, aiming for maximum torque current ratio controlequations were first pu, re-fitting, get a precise fit curve, simplifying its control function,the simulation results demonstrate its feasibility. At the same time, the text on the interiorpermanent magnet synchronous motor running state analysis, elaborated on the state ofmaximum torque current ratio control, constant torque weakening control state and status ofthis three constant power control modes, and for its operational status propose an optimizedcontrol strategy.Meanwhile, the medium for the stator flux permanent magnet synchronous motor directtorque control strategy is analyzed in detail, classified as a direct calculation method, basedon observer-based method and the counter electromotive force method. One for theback-EMF-based method elaborated non-orthogonal flux feedback and synovial algorithmobtained using a permanent magnet synchronous motor stator flux observer to achieve speedsensorless speed control strategy.The motor speed based AD2S1210circuit, draw precise speed, and the use of synovialadaptive stator flux observer inverse operation to obtain precise interior permanent magnetsynchronous motor parameters to optimize interior permanent magnet synchronous motorrunning.