Low-voltage current-limiting control method for suppressing commutation failure

Abstract

The invention discloses a low-voltage current-limiting control method for suppressing commutation failure, and belongs to the technical field of high-voltage direct-current transmission. The method comprises the steps: detecting a direct current, a direct-current voltage and an alternating-current voltage of an inverter side, and starting a low-voltage current-limiting controller after determining that a fault occurs; calculating a direct current variable quantity, and multiplying the direct current variable quantity by virtual resistance to obtain a voltage compensation quantity, wherein the direct current variable quantity is obtained by superposing an actual variable quantity and a predicted variable quantity, and the predicted variable quantity is the sum of multi-order differential terms of the direct current; and inputting a difference value between the direct-current voltage value before the fault and the voltage compensation amount to a low-voltage current-limiting controller, so that the low-voltage current-limiting controller changes a direct-current instruction value according to the difference value so as to limit the direct current. According to the invention, after an alternating current fault occurs, direct current can be reduced in advance and commutation conditions can be improved by combining direct current prediction and the virtual resistance, so that commutation failure is inhibited, current impact during an alternating current system fault is reduced, and system recovery after the fault is promoted.

Description

technical field

[0001] The invention belongs to the technical field of high-voltage direct current transmission, and more specifically relates to a low-voltage current-limiting control method for suppressing commutation failure. Background technique

[0002] Due to its advantages of large transmission capacity and long transmission distance, HVDC transmission using grid commutation converters has become the main means to solve the problem of reverse distribution of energy centers and load centers in my country. However, since it uses a thyristor without self-shutoff capability as a commutation element, it is easy to cause commutation failure when the AC system at the receiving end fails. Failure of phase commutation will lead to sharp increase of DC current, sudden drop of DC voltage, and in serious cases, DC blocking and interruption of transmission power. As the number of DC transmission lines fed into the AC grid at the receiving end gradually increases, the AC-DC coupli...

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