Method for determining rotating speed of restarted asynchronous motor

Abstract

The invention discloses a method for determining a motor rotating speed of a restarted asynchronous motor, which comprises the following two steps of: 1, generating an appropriate voltage vector by using a frequency converter, applying the voltage vector to a motor stator side, and estimating a rough value of the motor rotating speed in a stator current space vector directional coordinate system; and 2, starting searching a real motor rotating speed by using the motor rotating speed estimated in the step 1 as an initial rotating speed, wherein a current error rate function is taken as the main basis of rotating speed searching and can be calculated according to an included angle between a voltage vector on the input side of the frequency converter and a current vector on the input side of the motor, a stator current reference value extracted from a motor model and a real motor stator current value. The current rotating speed of the motor can be accurately determined when the asynchronous motor freely rotates, so that the asynchronous motor is directly started at the current speed; and the implemented scheme does not need a speed sensor and related peripheral circuits and is clear in physical significance and easy to implement, and a rotating speed estimation algorithm is simple and reliable.

Description

technical field [0001] The invention relates to a motor speed estimation method, in particular to a method for determining the motor speed when an asynchronous motor is restarted. Background technique [0002] In the high-performance asynchronous motor vector control system, the speed closed loop is essential. Since the speed sensor affects the simplicity, cheapness and system reliability of many asynchronous motor speed control systems in terms of installation, maintenance, and cost, people have proposed a speed sensorless closed-loop control scheme for speed. The core problem is the estimation of the rotor speed. So far, there are more than a dozen methods for speed estimation algorithm. The basic starting point is to use direct calculation, observer, self-adaptive and other means to measure voltage and current from the stator side and then extract the quantity related to the speed. [0003] However, before the inverter drives the motor to run, the motor rotor may be in ...

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Problems solved by technology

Although the physical concept of this idea is clear, it is difficult to implement. Generally, there is no DC bus current detection in the inverter device, and it is difficult to judge the minimum DC bus current and the change trend of the DC bus capacitance in the actual system. Therefore, it is generally not adopt this scheme

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