Research On Motor Control System And Its Temperature Characteristic In Extended Range EV

In order to solve the problem of short driving range, a range extender is added tothe electric vehicle, which makes up the extended range electric vehicle(EREV). InEREV, there are two motors, the drive motor and the range-extender generator. Theywork in different ways, which need special control methods. Ambient temperature inElectric vehicles is very poor, especially in high latitude and high altitude areas, whichwill lead to some certain change in properties of motor controllers and affect thesystem’s normal operation. Therefore, research on motor control system and itstemperature characteristic in extended range EV has important practical significance.This research was based on the design idea to ensure driving range and reduce fuelconsumption. To implement this concept, the foundation is a platform with good powerperformance and the key is control strategy. This paper gave the matching schemewhich meets power performance and constructed the thermostat and power followingcontrol strategy. According to the proposed comprehensive fuel consumption evaluationmethod, thermostat strategy has lower fuel consumption in the same range, which is inaccordance with the design concept.Because of the addition of range-extenders, EREVs have variety of energy supplymodes in theory, which meet the needs of the vehicle control strategy. To some extent, itdepends on the generator control system. In this paper, a power system circuit modelwas presented, based on which, the power flow of power control, current control andvoltage control were analyzed. Analysis holds the conclusion that under voltage controlpower supply mode is limited, power control and current control can meet the require-ment of power supply mode. But considering the power control is not conducive to real-ize accurate output control and the problem of large output current fluctuation, the cur-rent control was more suitable.In this paper, the similarities and differences between control systems of drive mo-tors and range-extender generators were discussed, and pointed out that they wereversatile in hardware. Drive motor control system is focused on torque output capacityand response, and it is mainly in torque control mode, sometimes in speed control mode.So a set of universal hardware platform was built. Based on this platform, the experi-mental debugging of torque control and speed control were completed.In order to know the possible influence of high and low temperature environmenton the electric vehicle motor control system, an temperature characteristic testing plat-form for motor controllers was built. Test results showed that under normal temperaturerange, the motor controller’s efficiency increased as temperature rised, and the outputcapacity was reduce at low temperature. An speculative explanation was proposed thatthe output capacity’s fall at low temperature was caused by dc bus capacitors’ degenera- tion. In addition，it was deduced that the falls of motor and its controller’s efficiencywith temperature’s falling could lead to a loss of up to5.6%driving distance in theory.Research on temperature characteristic on dc bus capacitors, current sensors,IGBTs and their driver circuits was made. Research showed that film capacitors had anexcellent temperature characteristic compared with electrolytic capacitors, so it wasvery suitable for electric vehicles as dc bus capacitors. Based on the AC circuit model ofdc bus capacitor, this paper analyzed the influence of dc bus capacitor parameters on theability of shunting and sustaining to high frequency current ripple, thus verified theprevious conjecture about the motor controller output ability’s fall at low temperature.The test results on two kinds of current sensors showed that the closed loop sensorsshowed more excellent temperature characteristic on the basic error and zero outputerror compared with the open loop sensors, and was suitable for the application in elec-tric vehicles. Test results showed IGBTs and their driver circuits were affected bytemperature little. At last, this paper put forward some compensation measures forimprovement because of the temperature characteristic of the parts.