Research On Driving Control System For Electric Vehicle

Developing electric vehicle is a very important way to release the pressure from energy and environmental in today's auto industry. Merits and demerits of driving system for electric vehicle have direct impact on vehicle's dynamic property and economy. This thesis is mainly researched from the aspects of improving driving system dynamic response, expanding flux-weakening growth and reducing torque ripple by dead-time effect compensation, which can improve performance of driving control system for electric vehicle.This article outlines the basic principle about the driving IPMSM for electric vehicle adopting direct torque control with space vector modulator (DTC-SVM) control and analyses stable operating conditions of DTC-SVM control method. For meeting condition as possible the article designs torque PI regulator with the feedback of difference angle, which is not only capable of detecting and suppressing controller voltage saturation, enabling the system to operate on linear characteristics of operation and improving control accuracy, at the same time, compared with ordinary PI regulator , it improves the torque response of entire system. Based on parameters of the driving IPMSM for electric vehicle, this article respectively deduces and fits the functional relation between the electromagnetic torque and the amplitude of stator flux linkage according to principle of both maximum torque or speed control below the base speed and stator current phase-shifted control along the current limit above the base speed, besides gives the flux-weakening speed-expansion algorithm based on stator flux oriented. The algorithm can make electric vehicle driving motor from constant torque smooth transition to constant power operation, giving full play to flux-weakening speed-expansion of motor, besides having big starting torque and so on. In addition, the article analyses current distortion phenomena and increased harmonic content caused by the dead-time and voltage drop of power switch component. Online feedback compensation method is derived form above theoretical analysis, which suppresses effectively harmonic content and reduces Total Harmonic Distortion of current and torque ripple of driving system for electric vehicle. At last, 7.5kW interior permanent magnet synchronous motor is implemented as driving motor for electric vehicle. A resolver is applied to detect position/speed information. Building experimental platform and finishing the experiment. Simulation and experiment results show that when adopting the DTC-SVM algorithm, driving motor for electric vehicle has fast torque and speed response. Flux-weakening speed-expansion performance of the driving IPMSM for electric vehicle is fully paid out by flux-weakening growth algorithm provided. Dead-time compensation algorithm can effectively suppress output current harmonics of frequency converter and reduce torque ripple of motor.