A control method and system for variable flux of a permanent magnet synchronous motor

Abstract

The invention relates to a control method and a system for variable flux of a permanent magnet synchronous motor. The control method comprises the following steps: obtaining motor speed and current value of the permanent magnet synchronous motor; the magnetization direction of each magnetic steel is obtained according to the current value and the rotational speed of the motor; according to the motor speed of the permanent magnet synchronous motor and the magnetization direction of each magnet steel, whether to charge and demagnetize the demagnetized magnet steel is confirmed. As that demagnetize steel is demagnetized, the demagnetize steel is demagnetized according to the direct-axis pulse current generated according to the rotational speed and the current value of the motor. As that motorspeed and the current value of the permanent magnet synchronous motor are obtained, and the magnetization direction of each magnetic steel of the permanent magnet synchronous motor is confirmed according to the rotational speed and the current value of the motor, according to the motor speed and magnetization direction, whether demagnetization is needed is confirmed. When demagnetization is needed, a direct-axis pulse current is generated to demagnetize the magnet steel, and the strength of the internal magnetic field of the motor is changed in real time, so that the speed range of the motorcan be expanded without flux weakening current.

Description

technical field [0001] The invention relates to the technical field of permanent magnet synchronous motors, in particular to a control method and system for changing magnetic flux of permanent magnet synchronous motors. Background technique [0002] In recent years, drive motors for new energy vehicles mostly use built-in permanent magnet synchronous motors (IPMSM), which have the advantages of high power density, good mechanical characteristics, and high speed range, and have received extensive attention and attention in electric vehicle drive systems. application. However, the direct-axis inductance of the built-in permanent magnet synchronous motor is usually smaller than the quadrature-axis inductance. In order to use the reluctance torque and realize the field weakening control, the current trajectory is located in the second quadrant, and the current always contains a field weakening component, which increases the loss and the utilization of the magnet. The rate is lo...

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Problems solved by technology

However, the direct-axis inductance of the built-in permanent magnet synchronous motor is usually smaller than the quadrature-axis inductance. In order to use the reluctance torque and realize the field weakening control, the current trajectory is located in the second quadrant, and the current always contains a field weakening component, which increases the loss and the utilization of the magnet. low rate

In addition, after the motor enters the high-speed stage, it is necessary to weaken the motor by increasing the direct-axis demagnetization current component to control the motor terminal voltage not to exceed the limit value of the inverter voltage. At this time, the large field-weakening current makes The copper loss of the motor increases, resulting in a decrease in the efficiency of the motor, and due to the limitation of the power level of the inverter, the current also has a limited value, resulting in a limitation in the degree of field weakening of the motor and a narrow range of speed adjustment

[0003] In the prior art, a mechanical magnetic modulation type permanent magnet synchronous motor is proposed. The mechanical magnetic modulation device is used to change the strength of the internal magnetic field of the motor, thereby reducing the weak magnetic current at high speed and improving the working efficiency of the motor. However, the mechanical magnetic modulation type permanent magnet motor The magnetic adjustment device is relatively complicated, and increases the volume and weight of the entire motor to a certain extent, so it is not conducive to improving the power density and efficiency of the motor

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