Direct-current pre-excitation starting method for VVVF control of asynchronous motor under flux linkage control

Abstract

The invention discloses a direct-current pre-excitation starting method for the VVVF (Variable Voltage Variable Frequency) control of an asynchronous motor under flux linkage control, belonging to the technical field of the starting control of asynchronous motors. The direct-current pre-excitation starting method for the VVVF control of the asynchronous motor under the flux linkage control is characterized in that an included angle for synthesizing an excitation current vector and a starting voltage vector in a starting process is 90 degrees; a current is decomposed according to a known voltage vector direction for the VVVF control to obtain a reactive current feedback value; and the reactive current feedback value is converted into a voltage regulation value by gain amplification to control the flux linkage. In the invention, the direct-current pre-excitation and the starting process are controlled sequentially by using a DSP (Digital Signal Processor) chip. The method has an inhibition effect on the peak current subsequently appearing in the starting process.

Description

technical field The invention mainly relates to increasing the starting torque of the frequency conversion speed regulation system, reducing the starting current so as to improve the starting performance of the frequency converter-asynchronous motor system, and belongs to the technical field of power electronics application. Background technique Starting performance is one of the important indicators to measure the frequency converter-asynchronous motor speed control system. The closed-loop control method based on vector control theory can improve the starting performance, but in the closed-loop speed regulation system with medium and large capacity, due to factors such as low switching frequency, minimum pulse width limitation of switching devices, and difficulties in motor parameter identification and dead zone compensation, the performance is weakened. The effect of closed-loop control. Due to the difficulty in observing the flux linkage during the low-speed stage of the...

AI Technical Summary

Problems solved by technology

For frequency converters with devices in parallel structure, the volume of the frequency converter and the manufacturing cost of the radiator will be increased while increasing the cost of the components

(2) Although the inrush current generated is large, the output torque is not large, so when the motor starts from a static state with a large torque load, it often fails to start

(3) Excessive starting current will not only cause damage to its own equipment, but may also lower the grid voltage and affect the normal operation of other electrical equipment on the same grid

That is, the current suppression effect that formula (6) can achieve can only work in the first few switching cycles of the starting process. As the stator flux linkage starts to rotate, the orthogonal relationship in formula (6) will be difficult to guarantee, so predict The excitation effect will also diminish rapidly

Therefore, this method has a limited effect on the subsequent peak current suppression during the starting process.

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