Method for realizing stable operation of frequency converter under V/F (voltage/frequency) control

Abstract

The invention relates to a method for realizing the stable operation of a frequency converter under V / F (voltage / frequency) control. The method comprises the steps of sampling, coordinate conversion, power calculation, one-order low-pass filtering, P (power) regulator regulation, amplitude limitation and integration processing. The method concretely comprises the steps that the motor three-phase current is sampled and filtered, and the motor input voltage is sampled; the three-phase current and the voltage are converted into two-phase current and voltage, and the current and the voltage on the alpha axis and the beta axis are calculated; the active power P and the apparent power S input into a motor are calculated; the efficiency error is subjected to P regulation and is multiplied by the rated frequency to obtain the compensation frequency; the compensation frequency is subjected to amplitude limitation; and for the integration processing, a rotating angle theta is obtained through the integration operation on the angle frequency omega. The active power change is controlled, the rotating angle can be dynamically regulated through adopting a frequency compensation method in the magnetic chain vector coordinate system, the current oscillation is inhibited, and the stability of the system is maintained. In the application, the stability of the system can be regulated through regulating the KP values according to the actual conditions.

Description

technical field [0001] The invention relates to the field of motor control, in particular to a method for a frequency converter to run stably under V / F control. Background technique [0002] In recent years, frequency converters have made considerable progress as key equipment for energy conservation, and are widely used in fans and pump drives. This type of inverter mainly adopts open-loop V / F control. The open-loop V / F control system is based on the steady-state model of the AC motor. It does not depend on the motor parameters and their changes. Therefore, the control is simple and easy to implement, and it is widely used in industrial control. [0003] The instability of the V / F control system is a very complicated problem, which is related to many factors. Such as stator resistance, rotor inertia, dead time, carrier frequency, system resonance, etc. When the switching frequency of the frequency converter is relatively high, the dead zone effect will cause the distorti...

AI Technical Summary

Problems solved by technology

This fluctuation leads to torque fluctuations and motor speed fluctuations. Under no-load or light-load conditions, the motor speed continues to oscillate, and the output current of the inverter oscillates sharply, which in turn causes system protection.

[0004] There is inherent instability in the V / F open-loop control system of the induction motor, and the continuous oscillation of the current is prone to occur in certain operating frequency bands. In severe cases, it will cause the overcurrent protection of the inverter or even burn the power module

This problem is particularly prominent in the case of no-load or light-load operation, which limits the operating speed regulation range of the V / F open-loop control system

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