Static frequency converter system and switching method from intermittent commutation to natural commutation

Abstract

The invention provides a static frequency converter system and a switching method from intermittent commutation to natural commutation. The switching method comprises the following steps of: when themotor stator frequency reaches a set switching frequency threshold, locking a machine side inverter module in a frequency converter, and controlling the work of a network side rectifier module in an inversion state; detecting a current of a motor stator, when the current of the motor stator in a set time quantum is still smaller than or equal to a set current lower threshold, locking the network side rectifier module until a thyristor in the network side rectifier module to be switched off; controlling the network side rectifier module to be worked in a rectification state to control the machine side inversion module to be worked in a natural commutation mode. According to the technical scheme of the invention, the motor is smoothly converted from an intermittent commutation phase to a natural commutation phase, and the phenomenon of commutation failure does not occur during the switching process.

Description

technical field [0001] The invention belongs to the technical field of static frequency converter start-up process control, and in particular relates to a static frequency converter system and a switching method from intermittent commutation to natural commutation. Background technique [0002] The motor (that is, the unit) is divided into two stages during the entire start-up process, one of which is the intermittent commutation stage and the other is the natural commutation stage. [0003] After determining the initial position of the motor rotor, trigger the specific thyristor of the inverter on the machine side to make the rotor rotate under the action of the magnetic field force. When the motor speed is low, the stator voltage of the motor is also very small, so it is impossible to rely on the stator terminal voltage to make the motor rotate. The side converter completes the commutation. At this time, the discontinuous commutation method is used to start. The start-up p...

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Problems solved by technology

[0006] The purpose of the present invention is to provide a static frequency converter system and a switching method from intermittent commutation to natural commutation, which are used to solve the problem caused by the failure of the switching operation when switching from the intermittent commutation stage to the natural commutation stage during the starting process of the motor. Motor start failure problem

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