| Traditional vehicles which use internal combustion engine bring transporting convenience to people, at the same time; they also lead to three serious problems of energy, environment and safety. Electric vehicle (EV) has many advantages, such as non-pollution and high efficiency. It is an effective way to solve the global energy crisis and environmental issues by developing electric vehicle. So it has become a research focus of many governments and research institutes. It is the key sections of electric vehicle technology that how to make use of power to drive the vehicle efficiently, non-pollution and intelligently. It is very important for us to know how to develop the whole performance of the driving control system, which is the core part of the electric vehicle. Permanent magnet synchronous motor (PMSM) is an ideal driving motor for electric vehicle because it has the advantages such as large power factor, high reliability and good control performance. As for the drive of the control system in the electric vehicle, if the power of the inverter was supplied by a constant DC-link voltage, when it run slowly, there were some disadvantages in the system, such as large torque ripple, big current harmonic distortion of the motor windings and large stress of the switch. This paper proposed a new strategy for vector control of permanent magnet synchronous motor with variable DC-link voltage; it was suitable for the electric vehicle.Firstly, this paper introduces the development of the electric vehicle and analysis the advantages and disadvantages of the drive of the control system with different kinds of motors, then select the PMSM as the driving motor for the drive of the control system in the EV. Also, vector control of PMSM is studied; the technology of space voltage pulse width modulation (SVPWM) is introduced; the relationship between harmonic distortion of the output voltage with modulation index of the inverter by SVPWM; mathematical model of vector control of PMSM fed by two-level inverter is established. At last, vector control of PMSM with variable dc-link voltage is proposed. The whole control system is simulated with Matlab/Simulink software. The simulation results verify the effectiveness and feasibility of the new strategy.Secondly, the hardware of the whole control system is designed including the power drive board, main board and signal processing board. The whole design based on the TMS320F2812 DSP as the control core. Programs of signal processing, generation of SVPWM wave, speed calculation and vector control algorithm are developed and tested under the DSP environment CCS3.1.The simulation and experimental results show that vector control of permanent magnet synchronous motor with variable dc-link voltage can stratify the requirement of drive of the control system in the electric vehicle. Because the new control strategy can decrease torque ripple, improve current waveform effectively and decrease the total harmonic distortion of the current of the motor. It also has good static and dynamic characteristics. The results of this paper have some practical significance for electric vehicle technology. |
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