Development of an Advanced Motor Control System for Electric Vehicles

Abstract

Electric vehicles are considered as one of the most popular way to decrease the consumption of petroleum resources and reduce environmental pollutions. Motor control system is one of the most important part of electric vehicles. It includes power supply module, IGBT driver, digital signal processing (DSP) controller, protection adjustment module, and resolver to digital convertor. To implement the control strategies on motor control system, a lot of practical aspects need to be taken into accounts. It includes setup of the initial excitation current, consistency of current between motor and program code, over-modulation, field weakening control, current protection, and so on. In this paper, an induction motor control system for electric vehicles is developed based on DSP. The control strategy is based on the field-oriented control (FOC) and space vector pulse width modulation (SVPWM). Speed calculation, over-modulation, field weakening control, PI controller, and fault diagnosis are also applied in this DSP algorithm. As an industry product running on a real electric bus with a 100kW induction motor, communication with vehicle control unit (VCU) by CAN bus, control system safety and PC software designed for lab experiments are also discussed. This paper focused on how to develop the advanced motor control system for electric vehicles for industrial application. The steady-state and transient performances of this motor control system are analyzed by both test-bench experiments and road experiments. Its performance is satisfactory when applied to the real electric vehicle.

Implementation of an Improved Motor Control for Electric Vehicles

“…It decides the transient and steady-state performance of the motor control. The current module works as the system observer for the rotor flux and electrical angle [11]. The input variables of this module are the rotor speed and stator current in the rotating frame I d and I q .…”

“…The driver instructions, such as starts and stops, speed acceleration or deceleration and changing gears, are all sent by CAN in these tasks. PWM_ISR contains the main algorithm for FOC and MPC, while FAULT_ISR works for fault diagnose [11]. The MPC program flow diagram in the PWM interrupt service function is shown in Figure 8.…”

“…The motor control is implemented for real electric vehicles. Not only do the FOC and MPC algorithms need to be considered, but also some practical problems, such as initializing the excitation current [6], the current consistency of program and motor [11], field weakening control, over modulation, etc. Some of these issues are listed in this part.…”

“…The comparison of classic FOC, DTC and MPC are shown in Table 1. For the motor control of electric vehicles, the FOC appears to be the most popular control approach [9][10][11]. However, MPC on motor drives has been widely studied recently and promoted as an improved approach for the motor controller [12][13][14].…”