As the main components of electric vehicles, motors, drives and motor controllers play a very important role in the complete system of electric vehicles. The research in related fields has important theoretical and practical significance.
Principle of motor controller:
As the control center of the entire braking system, the motor controller is composed of an inverter and a controller. The inverter receives the direct current power delivered by the battery and inverts it into a three-phase alternating current to provide power to the car motor. The controller receives signals such as the motor speed and feeds it back to the instrument. When braking or acceleration occurs, the controller controls the frequency of the inverter to increase and decrease, so as to achieve the purpose of acceleration or deceleration.
Classification of motor controllers:
1. DC motor drive system
Motor controllers generally use pulse-width modulation (PWM) chopping control, which has simple, mature, and low-cost control technology, but has shortcomings such as low efficiency and large size.
2. AC induction motor drive system
The motor controller adopts PWM mode to realize the power conversion from high-voltage DC to three-phase AC, adopts variable frequency speed regulation to realize motor speed regulation, and adopts vector control or direct torque control strategy to realize the fast response of motor torque control.
3. AC permanent magnet motor drive system
Including sine wave permanent magnet synchronous motor drive system and trapezoidal wave brushless DC motor drive system. The sine wave permanent magnet synchronous motor controller adopts PWM mode to realize the power conversion from high voltage DC to three-phase AC, and adopts variable frequency speed regulation to realize motor regulation. Speed; Trapezoidal wave brushless DC motor control usually adopts the "weak field speed regulation" method to achieve motor control. Since the low-speed torque ripple of the sine wave permanent magnet synchronous motor drive system is small and the speed regulation in the high-speed constant power zone is more stable, it has a better application prospect than the trapezoidal wave brushless DC motor gallop system.
4. Switched reluctance motor drive system
The motor control of the switched reluctance motor drive system generally adopts the fuzzy sliding mode control method. At present, the motors used in pure electric vehicles are all permanent magnet synchronous motors. AC permanent magnet motors use rare-earth permanent magnets for excitation. Compared with induction motors, no excitation circuit is required. It has high efficiency, high power density, high control accuracy, and small torque ripple. Features.
Fourth, the relevant terms of the electric controller
1. Rated power: the output power under rated conditions.
2. Peak power: the maximum output power allowed by the motor within the specified duration.
3. Rated speed: the speed of the motor under rated power.
4. Maximum working speed: the motor speed corresponding to the highest design speed of the electric vehicle.
5. Rated torque: the output torque of the motor at rated power and rated speed.
6. Peak torque: the maximum torque that the motor is allowed to output within the specified duration.
7. The overall efficiency of the motor and the controller: the output power of the motor shaft is divided by the input power of the controller and then multiplied by 100%.