Velocity sensorless vector control method for single bus current detection of three-phase alternating-current motor

Abstract

The invention discloses a unique velocity sensorless vector control method for single bus current detection of a three-phase alternating-current motor. The velocity sensorless vector control method comprises the steps of detecting the bus current by a shunt resistor mounted on the bus low voltage side of a frequency changer, determining the trigger time adopted by the bus current according to the pulse width modulation PWM duty ratio of a control switch, and correspondingly reconstructing three-phase current of the motor. According to the motor current reconstruction method, a motor current direct detection hardware circuit is detected, so that the hardware cost is saved, and the same performance as the vector control of the motor three-phase current direct detection can be achieved. The velocity sensorless vector control method is suitable for a space vector PWM mode and is favorable for solving the problems of sector boundary and low modulation region in a vector method based on space switching. Analysis of experimental results shows that the motor current reconstruction method is also suitable for other any switch modulation mode and is higher in commonality and practicality. Particularly in small current and low modulation regions, the three-phase current of the motor also can be precisely reconstructed.

Description

Technical field: [0001] The invention relates to a speed sensorless vector control (SVC) three-phase permanent magnet synchronous motor (PMSM), in particular to a single bus current detection sensorless vector control method by reconstructing a three-phase AC motor current. Background technique: [0002] Vector control is currently the most popular high-performance motor control method. Through coordinate vector transformation, the three-phase current of the motor is decomposed into two mutually perpendicular dq axis currents: the flux component and the torque component, and then the flux and torque of the motor are directly controlled like a DC motor to achieve fast dynamics Responsive and precise control. [0003] The speed sensorless vector control eliminates the speed sensor (usually an encoder) of the motor, and observes the speed and position of the motor through the current of the motor. This not only reduces the cost of the motor control hardware, but also improves the re...

AI Technical Summary

Problems solved by technology

However, there is a problem with this method of motor current reconstruction, Space Vector Pulse Width Modulation (SVPWM) at the sector boundary and low modulation region of the space vector, if the active vector lasts less than the current sampling time, it will go wrong

For this reason, some public schemes take a compensation method, which is to insert an effective vector when adjacent to the boundary, but inserting an effective vector will bring distortion to the current waveform

At the same time, this method is only limited to the space vector pulse width modulation mode. For other pulse width modulation modes, the phase current of the motor is directly equal to the bus current method and cannot be used.

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