Electric vehicle permanent magnet synchronous motor torque control method

Abstract

The invention discloses an electric vehicle permanent magnet synchronous motor torque control method combining calibration table look-up with voltage control closed-loop compensation flux-weakening current. The method comprises the steps: reducing the given Q-axis current through a D-axis current compensation value outputted by a voltage loop so as to guarantee that the output torque remains unchanged under the condition that the voltage loop works. According to the method, the torque control precision can be improved, the control stability of the permanent magnet synchronous motor of the electric vehicle is ensured, and information of flux weakening control, maximum torque-to-current ratio control and maximum torque-to-voltage ratio control is already contained in the calibration look-uptable so that the method is a high-efficiency control method.

Description

technical field [0001] The invention belongs to the field of permanent magnet synchronous motor control, and in particular relates to a control method for permanent magnet synchronous motors in new energy electric vehicles, electric boats and the like. Background technique [0002] In recent years, with the development of new energy and the continuous improvement of permanent magnet materials, permanent magnet synchronous motors have gradually become the main propulsion motors on new energy electric vehicles and electric boats, and have been more and more widely used. At present, electric vehicles are equipped with rotary encoders to detect position signals, and then use field-oriented control to control the output torque and speed of permanent magnet synchronous motors. [0003] Motor torque control mode and speed control mode are usually used in electric vehicles. In torque control mode, it is generally necessary to quickly track the target given torque to achieve the rapi...

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Problems solved by technology

[0005] This method can not only optimize the efficiency, but also solve the problems of system stability and magnetic field weakening, but there is a defect, the table regards the DC bus voltage as a fixed voltage and the speed as a fixed speed in the look-up table , but in the actual process, the DC bus voltage is the battery voltage. The battery voltage changes during the running of the car, and the speed also changes. When the torque is quickly responded to, it may cause the speed to rise rapidly and the battery voltage to drop. It is easy to appear that the voltage is saturated during the dynamic adjustment process and the look-up table method cannot keep up with it in time, because the look-up table method filters the signal, and there must be errors in the DC bus voltage detection, which will cause the motor to be saturated in voltage. Then it lost control. Considering this problem, on the basis of the look-up table method, the voltage loop field weakening control is added. The output of the voltage loop is superimposed on the D-axis current given by the look-up table, so that when the voltage is saturated or the dynamic adjustment process , can also ensure the stability of the system. The problem is that after the output of this voltage loop is superimposed on the given current of the D-axis, for a salient pole motor, if the D-axis current increases and the Q-axis current remains the original value, then the output torque will increase. increase, which violates the accuracy requirement of following the target given torque, the output torque of the motor will be greater than the target given torque, and it is easy to cause the output current to exceed the maximum current limit

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