Power calculation based slip estimation system and power calculation based slip estimation method

Abstract

The invention provides a power calculation based slip estimation system. The power calculation based slip estimation system comprises a current sampling unit, a current conversion unit, a current regulation unit and a slip calculation unit, wherein the current sampling unit is used for sampling three-phase current of an asynchronous motor, the current conversion unit is used for obtaining feedback current D-axis component and Q-axis component, the current regulation unit is used for obtaining D-axis stator voltage and Q-axis stator voltage, and the slip calculation unit is used for obtaining slip according to the D-axis stator voltage, the Q-axis stator voltage, the feedback current D-axis component, the Q-axis component and a rotor time constant. The invention further provides a corresponding method. The system and the method have the advantages that the slip is estimated according to the ratio of active power to reactive power to enable rotor field orientation error caused by the rotor time constant Tr during speed regulation to become smaller, so that rotor field orientation effect of the asynchronous motor is improved effectively, and torque control precision is improved.

Description

technical field [0001] The invention relates to the field of asynchronous motor control, more specifically, to a slip estimation system and method based on power calculation. Background technique [0002] In order to realize the field-oriented control of the rotor of the asynchronous motor, it is necessary to obtain the actual speed of the rotor and the slip for control. At present, the slip of the rotor is obtained through the following methods: first, the rotor inductance Lr and the rotor resistance Rr of the motor are measured with high precision through offline identification; then the rotor time constant Tr is calculated by using the formula (1); and then the known The rotor time constant Tr and the torque current command Isq* and excitation current command Isd* used in the control, use the formula (2) to calculate the slip Wsl. Therefore, the rotor field-oriented control of the asynchronous machine is realized through the obtained slip. [0003] Tr=Lr / Rr (1) [0004...

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Problems solved by technology

[0010] In this scheme, the theoretical feedback current Isq and Isd are used to calculate slip, but when the time constant Tr used for slip calculation in formula (1) is inaccurate, the motor rotor orientation control angle will also deviate

Therefore, the feedback current Isq and Isd obtained by the control angle decomposition are inconsistent with the feedback current obtained by the angle decomposition of the actual magnetic field, and the slip obtained by calculation will also deviate from the theoretical value

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