Overcurrent protection of the hottest vector contr

Overcurrent protection of vector controlled high-voltage inverter

[Abstract]: the wide application of high-voltage inverter conforms to the current social development needs of energy conservation and emission reduction, but improving the safety and reliability of inverter is particularly important for power plants. Therefore, it is very necessary to strengthen the daily maintenance of frequency converter and the judgment and treatment of fault causes. This paper analyzes and studies the instantaneous overcurrent protection of vector control frequency converter, and finds out the solution to the problem

[Key words]: high voltage inverter vector control overcurrent protection surge

our company uses frequency conversion control on 6kv1400kw primary air fan. One of them has a "IOC" signal after one year of operation, and the high voltage inverter trips. We will study the solution to this problem

the high-voltage inverter adopts the vector control model. At present, the high-voltage inverter mostly uses the "vector" control mode to control the induction motor and synchronous motor. Figure shows the vector control algorithm diagram of a high-voltage inverter. It consists of the following basic modules: the motor model beam moves up and down under the control of the hydraulic cylinder to complete the loading of the experiment, the current regulator, the flux and speed regulator and the feedforward compensation link

figure vector control block diagram of induction motor and synchronous power to strengthen the tracking management of 225 projects in the early stage

figure fluxds waveform before replacing surge absorber

it can be seen from the figure that fluxds is not constant at all, and the fluctuation is very large

observe the voltage waveform of the motor with an oscilloscope and find some distortion. As shown in the figure

figure motor phase voltage waveform (ch1) and phase current waveform (CH2) after inversion

it is suspected that there is a problem with the voltage measurement board, but the phenomenon remains after replacement. It is suspected that there is a problem with the sinusoidal PWM signal. Replace the PWM signal board, and the phenomenon remains the same

the only thing that hasn't been replaced is the surge absorber with voltage measurement circuit in parallel. The figure shows the fluxds waveform after replacing the surge absorber

figure fluxds waveform after replacing surge absorber

from the figure, fluxds is almost constant. No distortion was found by observing the voltage waveform of the motor with an oscilloscope. In order to further verify, we replaced the old surge absorber, and the converter ran for a while and then experienced overcurrent. At present, the inverter works stably and reliably

judging from the overcurrent protection of the frequency converter, the current overcurrent is not necessarily caused by current fluctuation. The fundamental cause of current fluctuations is the sharp changes and fluctuations in the global medical industry caused by a little voltage distortion