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

A low-voltage current limiting and commutation failure technology, which is applied to emergency protection circuit devices for limiting overcurrent/overvoltage, AC network circuits, power transmission AC networks, etc., can solve the problem of aggravated commutation failure and current bus voltage maintenance Capability weakening, increasing the reactive power demand level of the converter station, etc., to achieve the effect of suppressing commutation failure, taking into account sensitivity and precision, and improving commutation margin

Active Publication Date: 2021-07-23
HUAZHONG UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, existing studies have shown that reducing the firing angle in advance will increase the reactive power demand level of the converter station, causing the reactive power of the AC grid to flow to the converter station, weakening the current bus voltage maintenance capability, or exacerbating commutation failure
The inherent contradiction between firing angle advance and AC bus voltage maintenance is difficult to resolve

Method used

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

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Embodiment 1

[0044] refer to figure 1 with figure 2 , the present invention provides a low-voltage current-limiting control method for suppressing commutation failure, including:

[0045] S1: Detect the DC current I on the inverter side dc , DC voltage U dc , AC voltage effective value E aci ; When it is determined that the AC system at the receiving end fails, start the low-voltage current limiting controller;

[0046] Specifically, the startup criterion of the low-voltage current limiting controller is one of the following:

[0047] (1) Single-phase fault detection: If the zero-sequence voltage component U of the voltage bus connected to the converter station 0 The amplitude is greater than the first preset value U levelI , the controller is started.

[0048] Among them, 3U 0 =U a + U b + U c , U a , U b , U c Respectively A, B, C three-phase voltage vector.

[0049] (2) Three-phase fault detection: If the AC voltage on the inverter side detected before and after the faul...

Embodiment 2

[0067] In order to verify the technical effect of the control method provided by the present invention, the simulation experiment is carried out with the CIGRE-HVDC standard test system model carried in PSCAD / EMTDC, the model is as follows Figure 4 As shown in , the system parameters all follow its own parameters without modification.

[0068] Compare the three control methods:

[0069] Method 1: The control strategy is exactly the same as the CIGRE standard test model;

[0070] Method 2: On the basis of method 1, add the present invention, but set the prediction time constant Δt of the present invention 1 with Δt 2 are all 0, that is, ΔI dcp = 0, only keep ΔI dca , then the voltage compensation ΔU dc =ΔI dca R*.

[0071] Method 3: on the basis of method 1, the present invention is added.

[0072] Comparing the effects of different suppression strategies on commutation failure under three-phase faults, the simulation settings are: at 0.8s, the AC bus on the inverter s...

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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...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02J3/36H02H9/02
CPCH02J3/36H02H9/02H02J2003/365Y02E60/60
Inventor 姚伟周泓宇艾小猛文劲宇
Owner HUAZHONG UNIV OF SCI & TECH
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