Frequency conversion soft start policy based on torque control

Abstract

The invention relates to a variable frequency soft startup strategy based on torque control. The strategy comprises sampling motor stator three-phase voltage, and converting voltage value in a three-phase stationary coordinate system to a two-phase stationary coordinate system; sampling motor stator three-phase current, and converting current value in the three-phase stationary coordinate system to the two-phase stationary coordinate system; perform integral operation based on the DC voltage of a DC converter and the switch state, and observing magnetic linkage with a magnetic linkage observer without voltage detection; observing torque with a torque observer; performing soft startup semiconductor switch algorithm based on magnetic flux control and torque control; performing space vector pulse width modulation (SVPWM) algorithm; and performing algorithm to distinguish the startup state. The invention solves large startup current problem when the open-loop converter is subjected to large load inertia, reduces the startup current of large inertia load and the preserved allowance of front end power supply design, and improves the reliability of the converter.

Description

technical field [0001] The invention relates to electric drive technology, in particular to an asynchronous motor control technology. The utility model belongs to the technical field of motors and electric drives. Background technique [0002] The application of the frequency converter has the function of reducing the starting current of the asynchronous motor to realize the soft start function. The normal starting current of an ordinary asynchronous motor is 7-8 times the rated current, and when driven by a general-purpose frequency converter, the starting current can be reduced to 1-2 times the rated current. However, for loads with particularly large inertia, such as heavy fans, heavy lifting and other loads, the current of the open-loop general-purpose inverter driving the motor is still large when starting, even exceeding twice the rated current value, resulting in frequency conversion. device overcurrent protection. Therefore, it can be concluded that the starting c...

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Problems solved by technology

However, for loads with particularly large inertia, such as heavy fans, heavy lifting and other loads, the current of the open-loop general-purpose inverter driving the motor is still large when starting, even exceeding twice the rated current value, resulting in frequency conversion. overcurrent protection of the

Therefore, it can be concluded that the starting characteristics of general-purpose inverters are still not ideal when the load inertia is large.

The specific performance is that the protection action is frequent when starting, and the capacity of the front-end transformer must exceed the rated capacity of the inverter and the motor, resulting in waste of equipment resources

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