CN111398765B - Thyristor triggering abnormity protection method for direct current transmission system - Google Patents
Thyristor triggering abnormity protection method for direct current transmission system Download PDFInfo
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The invention discloses a method for protecting the triggering abnormity of a thyristor of a direct-current transmission system, which comprises the following steps: detecting a thyristor trigger pulse; intercepting T after trigger pulse of thyristor appears1Thyristor voltage recording data U in time1(t); judging whether U is satisfied1_max>kset_1*Uv_max(ii) a Judging whether | U exists1(t)|≤kset_2*U1_max(ii) a Intercepting T after trigger pulse of thyristor appears1To T1+T2Thyristor voltage recording data U in time2(t); judging whether | U exists2(t)|≥kset_3*U2_min(ii) a Judging whether the abnormal times reach a set value NSET(ii) a And determining whether the protected thyristor equipment has abnormal triggering according to the judgment result. The invention adopts a voltage comparison method to identify the phenomena of abnormal triggering, abnormal turn-off and the like of the thyristor, reminds operators of potential safety hazards when the thyristor is frequently abnormal, and directly locks the converter valve when a plurality of thyristors are abnormal.
Description
Technical Field
The invention relates to a thyristor fault detection technology, in particular to a method for protecting abnormal triggering of a thyristor of a direct-current transmission system.
Background
The direct current transmission technology in China is developed earlier, direct current projects in Zhoushan and Kudzuvine have been built in 80 s, direct current projects in Tianguang, Sanchang, Gaokao, Xingan and the like have been built in the beginning of 21 st century, the construction speed of the direct current projects is further accelerated in recent years, and more than 30 direct current projects are built or put into production.
However, with the increase of the operation life of part of direct current projects, the direct current transmission equipment has an aging phenomenon, so that the operation loss of the equipment is increased, the performance of the equipment is reduced, and serious potential safety hazards are caused to the safe and stable operation of direct current. The thyristor converter valve is a core device of a direct current transmission project, wherein a thyristor can be triggered as required to convert three-phase alternating current voltage into direct current voltage, if the thyristor is abnormal in direct current operation, direct current blocking or shutdown is directly caused, and if 7, 14 days in 2017, month and 14 days due to breakdown of multiple high-level direct current thyristors, a single-pole shutdown accident is directly caused. After the occurrence of the accident, the voltage-resistant performance of the thyristors is reduced by detecting and finding the converter valve, the voltage-resistant performance of a plurality of thyristors is only 2-3kV, the requirement of phase change cannot be met, but the abnormality is not found in the direct current operation.
At present, the protection method for the trigger abnormity of the thyristor is deficient. In practical engineering, a signal (return inspection signal) established by detecting positive voltage or negative voltage of the thyristors is used for judging the thyristor level fault, if the thyristors have no return inspection phenomenon, direct current is directly locked, but if the voltage resistance of a certain thyristor is reduced, after the thyristor is struck in the positive voltage bearing period, and a certain blocking characteristic is recovered in the reverse voltage bearing period, the return inspection signal cannot identify the phenomenon. In addition, the pole control is provided with commutation failure protection, which identifies commutation failure by using the characteristic that the current at the side of the converter valve is different from the direct current after commutation failure, but the protection only aims at the triggering or commutation process of the whole bridge arm of the converter valve and cannot protect the triggering abnormity of a single thyristor.
Therefore, aiming at the problems faced by the current thyristor triggering abnormity protection, the thyristor triggering abnormity is identified as a research object, and the thyristor triggering abnormity protection method suitable for the direct-current power transmission system is one of the current research directions.
Disclosure of Invention
In order to find the problems of early conduction, non-conduction or non-recovery blocking of the thyristor and the like in time, clarify the performance reduction phenomenon of the thyristor and improve the direct current running reliability and stability, the invention provides a method for protecting the abnormal triggering of the thyristor of a direct current transmission system.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a method for protecting the trigger abnormity of a thyristor of a direct-current transmission system comprises the following steps:
step 1, detecting trigger pulse of a thyristor;
A. if detecting the trigger pulse of the thyristor, entering the step 2;
B. if the thyristor trigger pulse is not detected, continuing to perform the step 1;
step 2, intercepting T after the trigger pulse of the thyristor appears1Thyristor voltage recording data U in time1(t)；
Step 3, judging whether U is satisfied1_max>kset_1*Uv_max(ii) a Wherein, U1_maxIs U1Maximum value of absolute value of (t), Uv_maxThe maximum voltage value, k, born by thyristor theory in stable DC operationset_1Is a constant value proportionality coefficient;
A. if yes, entering step 4;
B. if not, the thyristor is triggered in advance, and the step 5 is entered;
step 4, judging whether | U exists1(t)|≤kset_2*U1_max(ii) a Wherein k isset_2Is a constant value proportionality coefficient;
A. if yes, entering step 6;
B. if not, the thyristor is not normally triggered, and the step 5 is entered;
step 5, adding 1 to the abnormal times;
step 6, intercepting T after the trigger pulse of the thyristor appears1To T1+T2Thyristor voltage recording data U in time2(t)；
A. if yes, entering step 9;
B. if not, the thyristor is not restored to be blocked, and the step 8 is carried out;
step 8, adding 1 to the abnormal times;
step 9, judging whether the abnormal times reach a set value NSET；
A. If not, entering step 10;
B. if yes, go to step 12;
step 10, judging the past T3Whether the abnormal times change within the time and whether the abnormal times are 0;
A. if the change or abnormal times are 0, entering the step 1;
B. if the change does not occur and the abnormal times are not 0, the step 11 is entered;
step 11, subtracting 1 from the abnormal times, entering the step 1, and continuously detecting the trigger pulse of the next period;
and step 12, obviously triggering abnormity occurs in the protected thyristor equipment, and protecting the action.
Furthermore, the calculation and sampling frequency of the method is more than or equal to 10kHZ。
Further, in step 2: when the frequency of an alternating current system connected with the direct current transmission project is 50Hz, T14.5-5.5 ms; when the frequency of an alternating current system connected with the direct current transmission project is 60Hz, T1＝3.7～4.7ms。
Further, in step 3: k is a radical ofset_1To constant scale factor, kset_1＝5～50％。
Further, in step 4: k is a radical ofset_2To constant scale factor, kset_2＝5～50％。
Further, in step 6: when the frequency of an alternating current system connected with the direct current transmission project is 50Hz, T29.5-10.5 ms; when the frequency of an alternating current system connected with the direct current transmission project is 60Hz, T2＝8～9ms。
Further, in step 7: k is a radical ofset_3To constant scale factor, kset_3＝150～200％。
Further, in step 9: n is a radical ofSET＝10。
Further, in step 10: t is a unit of3＝1min。
Further, the initial value of the number of abnormal times is 0.
The invention has the beneficial effects that:
1. the method adopts a voltage comparison method to identify the phenomena of abnormal triggering, abnormal turn-off and the like of the thyristor, reminds operators of potential safety hazards when the thyristor is frequently abnormal, and directly locks the converter valve when a plurality of thyristors are abnormal.
2. The method has the advantages that on one hand, the requirement on the calculation frequency is low, the calculation capacity of the existing control and protection equipment is not exceeded, and the practicability of the method is improved, and on the other hand, only the voltage information of the thyristor is utilized, and the current detection and the current measuring point of the thyristor are not required to be detected.
Drawings
Fig. 1 is a flowchart of a method for protecting a thyristor trigger anomaly of a direct-current transmission system according to the present invention.
FIG. 2 is a PSCAD/EMTDC DC simulation model.
FIG. 3 shows the trigger pulse and voltage U of the thyristor in the arm Y1 of the YY valve triggered at a certain time in the Tianguang DC simulation model1(t)。
FIG. 4 shows the trigger pulse and voltage U of the thyristor in the arm Y1 of the YY valve triggered at a certain time in the Tianguang DC simulation model2(t)。
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, the present invention is described in detail with reference to the accompanying drawings and the detailed description thereof.
Example (b):
as shown in fig. 1, the present embodiment provides a method for protecting a thyristor triggered exception in a dc power transmission system, where the system frequency is 50Hz, and the method includes the following steps:
step 1, detecting trigger pulse of a thyristor;
A. if detecting the trigger pulse of the thyristor, entering the step 2;
B. if the thyristor trigger pulse is not detected, continuing to perform the step 1;
step 2, intercepting thyristor voltage recording data U within 5ms after the thyristor trigger pulse appears1(t)；
Step 3, judging whether U is satisfied1_max>kset_1*Uv_max；
A. If yes, entering step 4;
B. if not, the thyristor is triggered in advance, and the step 5 is entered;
wherein, U1_maxIs U1Maximum value of absolute value of (t), U1_max＝max(|U1(t)|)；Uv_maxFor the maximum voltage value, U, to which the thyristor theory is subjected in stable DC operationv_max＝√2*UvN, wherein UvThe voltage is the theoretical line voltage of a valve side winding, and N is the number of single bridge arm thyristors of the converter valve; k is a radical ofset_3To constant scale factor, kset_3＝10％；
Step 4, judging whether | U exists1(t)|≤kset_2*U1_maxThe case (1);
A. if yes, entering step 6;
B. if not, the thyristor is not normally triggered, and the step 5 is entered;
wherein, U1_maxIs U1Maximum value of absolute value of (t), U1_max＝max(|U1(t)|)；kset_2To constant scale factor, kset_2＝10％；
Step 5, adding 1 to the abnormal times;
step 6, intercepting thyristor voltage recording data U within 5ms to 10ms after the occurrence of thyristor trigger pulse2(t)；
A. if yes, entering step 7;
B. if not, the thyristor is not restored to be blocked, and the step 8 is carried out;
wherein, U2_minIs U2Minimum value of absolute value of (t), U2_min＝min(|U2(t)|)；kset_3To constant scale factor, kset_3＝150％；
And 8, adding 1 to the abnormal times.
Step 9, judging whether the abnormal times reach a set value NSET＝10；
A. If not, entering step 10;
B. if so, go to step 12;
step 10, judging whether the abnormal times change within the past 1min and whether the abnormal times are 0;
A. if the change or abnormal times are 0, entering the step 1;
B. if the change does not occur and the abnormal times are not 0, the step 11 is entered;
step 11, subtracting 1 from the abnormal frequency, and entering the step 1;
and step 12, obviously triggering abnormity occurs in the protected thyristor equipment, and protecting and starting.
The consequences of the protection actions of step 12 of the present invention are: the abnormal triggering protection action of a single thyristor has no special influence, but when the number of the thyristors with abnormal triggering of one bridge arm exceeds the redundant number of the thyristors of the bridge arm, the converter is directly locked. The redundant number of the bridge arm thyristors is determined in the direct current engineering design stage, and is generally 3.
In order to verify the accuracy of the method, as shown in fig. 2, a wide direct current simulation model of +/-500 kV days is established based on the PSCAD/EMTDC, and simulation verification is performed by taking a thyristor in a Y1 bridge arm of a rectifying side electrode 2 (positive electrode) YY converter valve as a protection object. The total length of the Tianguang direct current line is 980km, the rated transmission power is 1800MW, the alternating current voltage at the rectifier valve side is 208.6kV, the system frequency is 50Hz, one bridge arm comprises 78 thyristors, and the redundancy quantity of the single-bridge arm thyristors is 3.
The protection algorithm is described by taking the case that the thyristor in the Y1 bridge arm of the YY converter valve can be normally triggered as an example, and before the example, the thyristor has no abnormal times. At a certain time, triggering of thyristors in a Y1 bridge arm of the YY converter valvePulse and voltage as shown in FIG. 3, the voltage wave between the X and O marked lines is U1(t)。
Then judging whether U is satisfied1_max>kset_1*Uv_max. Sort data to obtain U1_max＝0.865kV，Uv_max＝1.414*208.6/78≈3.78kV，kset_1*Uv_max0.378 kV. Therefore, this formula is satisfied.
Then, whether the | U exists or not is continuously judged1(t)|≤kset_2*U1_max. Collate data to get | U1The minimum value of (t) | is 0kV, kset_2*U1_max0.0865 kV. Therefore, the formula is satisfied, and the thyristor is normally triggered.
Intercepting thyristor voltage recording data U within 5ms to 10ms according to the flow of the method2(t) as shown in FIG. 4. Judging whether | U exists2(t)|≥kset_3*U2_min，|U2(t) | maximum 3.766kV, kset_3*U2_min0kV, so this equation is satisfied and the thyristor turns off normally.
After the abnormal times are judged to be not equal to the fixed value and 0, the thyristor abnormal recognition in the next trigger period can be continuously carried out.
Therefore, the method for protecting the abnormal triggering of the thyristor of the direct-current transmission system can correctly identify whether the thyristor has the phenomena of abnormal triggering, abnormal turn-off and the like, and reminds operators of potential safety hazards when the thyristor frequently has the abnormality.
The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention accordingly, and not to limit the protection scope of the present invention accordingly. All equivalent changes or modifications made in accordance with the spirit of the present disclosure are intended to be covered by the scope of the present disclosure.
Claims (10)
1. A method for protecting abnormal triggering of a thyristor of a direct-current transmission system is characterized by comprising the following steps: the method comprises the following steps:
step 1, detecting thyristor trigger pulses;
A. if detecting the trigger pulse of the thyristor, entering the step 2;
B. if the thyristor trigger pulse is not detected, continuing to perform the step 1;
step 2, intercepting T after the trigger pulse of the thyristor appears1Thyristor voltage recording data U in time1(t)；
Step 3, judging whether U is satisfied1_max>kset_1*Uv_max(ii) a Wherein, U1_maxIs U1Maximum value of absolute value of (t), Uv_maxThe maximum voltage value, k, born by thyristor theory in stable DC operationset_1Is a constant value proportionality coefficient;
A. if yes, entering step 4;
B. if not, the thyristor is triggered in advance, and the step 5 is entered;
step 4, judging whether | U exists1(t)|≤kset_2*U1_max(ii) a Wherein k isset_2Is a constant value proportionality coefficient;
A. if yes, entering step 6;
B. if not, the thyristor is not normally triggered, and the step 5 is entered;
step 5, adding 1 to the abnormal times;
step 6, intercepting T after the trigger pulse of the thyristor appears1To T1+T2Thyristor voltage recording data U in time2(t)；
Step 7, judging whether | U exists or not2(t)|≥kset_3*U2_min(ii) a Wherein, U2_minIs U2Minimum value of absolute value of (t), kset_3Is a constant value proportionality coefficient;
A. if yes, entering step 9;
B. if not, the thyristor is not restored to be blocked, and the step 8 is carried out;
step 8, adding 1 to the abnormal times;
step 9, judging whether the abnormal times reach a set value NSET；
A. If not, entering step 10;
B. if yes, go to step 12;
step 10, judging the past T3Whether the abnormal times change within the time and whether the abnormal times are 0;
A. if the change or abnormal times are 0, entering the step 1;
B. if the change does not occur and the abnormal times are not 0, the step 11 is entered;
step 11, subtracting 1 from the abnormal times, entering the step 1, and continuously detecting the trigger pulse of the next period;
and step 12, obviously triggering abnormity occurs in the protected thyristor equipment, and protecting the action.
2. The method for protecting the thyristor triggered abnormity of the direct-current transmission system according to claim 1, characterized by comprising the following steps: the calculation and sampling frequency of the method is more than or equal to 10kHZ。
3. The method for protecting the thyristor triggered abnormity of the direct-current transmission system according to claim 1, characterized by comprising the following steps: in the step 2: when the frequency of an alternating current system connected with the direct current transmission project is 50Hz, T14.5-5.5 ms; when the frequency of an alternating current system connected with the direct current transmission project is 60Hz, T1＝3.7～4.7ms。
4. The method for protecting the thyristor triggered abnormity of the direct-current transmission system according to claim 1, characterized by comprising the following steps: in the step 3: k is a radical ofset_1＝5～50％。
5. The method for protecting the thyristor triggered abnormality of the direct-current transmission system according to claim 1, characterized in that: in the step 4: k is a radical ofset_2＝5～50％。
6. The method for protecting the thyristor triggered abnormity of the direct-current transmission system according to claim 1, characterized by comprising the following steps: in the step 6: when the frequency of an alternating current system connected with the direct current transmission project is 50Hz, T29.5-10.5 ms; when the frequency of an alternating current system connected with the direct current transmission project is 60Hz, T2＝8～9ms。
7. The method for protecting the thyristor triggered abnormity of the direct-current transmission system according to claim 1, characterized by comprising the following steps: in step 7: k is a radical ofset_3＝150～200％。
8. The method for protecting the thyristor triggered abnormity of the direct-current transmission system according to claim 1, characterized by comprising the following steps: in step 9: n is a radical ofSET＝10。
9. The method for protecting the thyristor triggered abnormity of the direct-current transmission system according to claim 1, characterized by comprising the following steps: in the step 10: t is3＝1min。
10. The method for protecting the thyristor triggered abnormality of the direct-current transmission system according to claim 1, characterized in that: the initial value of the abnormal times is 0.
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