Motor zero-frequency crossing method based on variable exciting current

Abstract

The invention provides a variable excitation current-based motor zero-frequency crossing method, which comprises the following steps of: constructing a motor speed sensorless vector control system, acquiring a limit value of stator current frequency corresponding to an unstable boundary of the vector control system, and if the stator current frequency of the motor is equal to the limit value of the stator current frequency, determining that the motor is in a zero-frequency crossing state; increasing the exciting current of the motor, and reducing the absolute value of the slip rotation speed of the motor, so that the stator current frequency of the motor is greater than the limit value of the stator current frequency; the excitation current of the induction motor is greatly changed at a proper crossing working condition point, so that the operation working condition point of the induction motor rapidly crosses a stator current zero-frequency region, the motor actively crosses the stator current zero-frequency region, and the stator current frequency of the induction motor is ensured to be greater than a limit value of the stator current frequency. Therefore, the problems that the rotor rotating speed cannot be observed and the system is unstable due to the fact that the stator current frequency is close to zero frequency when the rotor rotating speed of the induction motor is constant and the load torque is changed are solved.

Description

technical field [0001] The invention relates to the technical field of motor control, in particular to a zero-frequency ride-through method of a motor based on variable excitation current. Background technique [0002] With the continuous promotion of induction motor, its speed sensorless control technology has gained wide attention and application due to its advantages of low manufacturing cost and high reliability. The speed sensorless vector control system of the induction motor performs well in the middle and high speed range of the rotor speed, but it does not perform well in the low rotor speed range. The reason is that the speed sensorless vector control technology of the induction motor is a control method based on the mathematical model of the motor; when the rotor speed of the induction motor is low and it is in the power generation condition due to the reverse load, the stator current of the induction motor is close to zero frequency. , resulting in the unobserva...

AI Technical Summary

Problems solved by technology

[0006] The invention provides a motor zero-frequency ride-through method based on variable excitation current, which is used to solve the problem that the sensorless vector control system with a feedback matrix fails to observe the speed near zero synchronous speed, and the rotor speed when the stator current is close to zero frequency The observability and the stability of the system in the full speed range have defects. When the stator current of the induction motor reaches the limit value, the excitation current command of the induction motor is changed so that the stator current frequency of the induction motor is always greater than or equal to its limit value. , and quickly change the excitation current command of the induction motor at a suitable working point, so that the induction motor can quickly pass through the zero frequency region of the stator current, and ensure the observability of the rotor speed of the sensorless vector control system of the induction motor at the zero frequency of the stator current

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