CN110581564A - A Method and System for Determining an UHV DC Commutation Failure Acceleration Protection Strategy - Google Patents

Abstract

The invention discloses a method and system for determining an accelerated protection strategy for UHV DC commutation failure acceleration, including: determining the operation mode of an AC-DC hybrid power grid, and setting the current DC commutation times as the first preset times threshold; The AC/DC hybrid power grid checks the stability of the AC/DC hybrid power grid when the number of consecutive commutation failures is the current DC commutation number and no blockage occurs after the last commutation failure, to Obtain a first check result; when the first check result indicates that the power grid is unstable, when the number of consecutive commutation failures in the AC/DC hybrid power grid is the current number of DC commutation times and after the last commutation failure When blocking occurs, the second checking result; when the current second checking result indicates that the power grid is stable, determine the protection strategy corresponding to the current DC power. The method of the invention is simple and easy, can significantly improve the calculation efficiency in the calculation of DC commutation failure, and save costs such as manpower and material resources.

Description

A Method and System for Determining an UHV DC Commutation Failure Acceleration Protection Strategy

technical field

The present invention relates to the field of safe and stable operation of a large-scale AC-DC hybrid power grid, and more specifically, to a method and system for determining an accelerated protection strategy for UHV DC commutation failure.

Background technique

Compared with traditional AC transmission, High Voltage Direct Current transmission (HVDC) has the advantages of occupying less line corridors and the transmission distance is not subject to static stability constraints. In order to optimize the allocation of energy resources in my country and meet the economic growth needs of the eastern region, large-capacity UHV DC transmission projects have been put into operation one after another. As of the end of December 2018, my country has 9 UHV (±800kV and above) DC transmission projects and 9 EHV (±800kV and below) long-distance DC transmission projects in operation. In addition, the system commissioning of the ±1100kV Changji-Guquan and ±800kV Shanghai Temple-Shandong UHVDC transmission projects will be completed in early 2019. By then, the cumulative number of UHVDC transmission projects put into operation will reach 11. UHVDC projects and traditional AC grids The interconnection of my country's large-scale AC-DC hybrid transmission pattern has formed.

The current HVDC transmission technology is based on thyristor-based line voltage commutation converters, which has a natural commutation failure problem at the inverter side of the receiving end. For a large-scale DC asynchronous interconnection system, the interactive influence of the sending and receiving end systems is more and more significant due to the "conduction" effect of the large-scale DC dynamic response characteristics. The large-scale instantaneous power impact generated during the continuous DC commutation failure process will lead to problems such as overvoltage and transient power angle instability in the sending and receiving end grids, which seriously affect the safe and stable operation of large-scale AC-DC hybrid grids. Especially during the failure of multiple DC simultaneous commutation at the sending and receiving ends, the surplus power generated by the instantaneous interruption of high-power transmission will be transferred to the AC system, which is likely to cause a huge energy impact on the weak section of the AC system and induce a series of Safety and stability issues, and even lead to major blackouts. This has become an unavoidable and urgent problem under the current large-scale AC-DC hybrid transmission pattern in my country.

With the increase in the number of DC continuous commutation failures, the power impact of commutation failures in the DC system on the AC power grid at the sending and receiving ends will become greater and greater, making it more difficult to arrange the operation mode of the power grid. Under the current grid pattern of "strong DC and weak AC", in order to ensure the safe and stable operation of my country's large-scale AC-DC hybrid power grid, it is necessary to check and calculate the accelerated protection of commutation failure for each DC to determine the maximum tolerable commutation of each DC The number of failures, and configure the corresponding protection strategy.

In the simulation calculation process of the safe and stable operation of large-scale AC-DC hybrid power grid, the commutation failure acceleration protection strategy mainly refers to the dc at a certain power level P ₀ , which withstands i consecutive commutation failures, and after the i+1th blocking , both the sending and receiving end AC-DC hybrid power grids can maintain safe and stable operation. The verification process of the protection strategy for DC commutation failure to ensure the safe and stable operation of large-scale AC-DC hybrid power grid is shown in Figure 1.

The bipolar power change after two consecutive commutation failures in DC is shown in Figure 2(a); the bipolar power change when the third block occurs after two consecutive DC commutation failures is shown in Figure 2(b) Show. Taking DC with 2 consecutive commutation failures (hereinafter referred to as "commutation failure 2 times") and 2 consecutive commutation failures to block DC for the third time (hereinafter referred to as "commutation failure 2+1") as an example, the process is as follows : Fault I (2 consecutive commutation failures), the first commutation failure occurred at the fault time of 1s, and the second commutation failure occurred at 1.2s; Fault II (2 consecutive commutation failures and the third blocking DC) , The first commutation failure occurred at the fault time of 1s, the second commutation failure occurred at 1.2s, the third commutation failure occurred at 1.4s, DC blocking occurred at 1.43s, all filters were cut off at 1.63s, and all filters were cut off at 1.73s Supporting power supply.

In order to compare the impact of different DC commutation failures on system stability at the same DC power level, Figure 3(a) and Figure 3(b) respectively show the DC commutation failures after 2 and 3 consecutive commutation failures. DC unipolar power variation curve. Among them, the area enclosed by the dotted line can represent the magnitude of the active power impact on the AC system during the commutation failure of the DC system. Obviously, at the same power level, compared with i consecutive commutation failures, i+1 consecutive commutation failures will cause a greater impact on the active power of the system.

However, the existing standards do not have a unified specification for the calculation method of DC commutation failure acceleration protection, and it is concluded after traversing and calculating various possible methods, the calculation amount is large and the calculation efficiency is low.

Therefore, there is a need for a method that can determine a reasonable commutation failure acceleration protection strategy based on simple calculations to ensure the safe and stable operation of large-scale AC-DC hybrid power grids.

Contents of the invention

The present invention proposes a method and system for determining an accelerated protection strategy for UHV DC commutation failure to solve the problem of how to determine the accelerated protection strategy for UHV DC commutation failure in an AC-DC hybrid power grid.

In order to solve the above problems, according to one aspect of the present invention, a method for determining an accelerated protection strategy for UHV DC commutation failure is provided, said method comprising:

Step 1, determine the operation mode of the AC-DC hybrid grid, and set the current DC commutation times;

Step 2, when the number of consecutive commutation failures of the AC/DC hybrid grid is the current DC commutation number and no blockage occurs after the last commutation failure, the stability of the AC/DC hybrid grid is checked checking, to obtain the first checking result;

Step 3, when the first check result indicates that the power grid is unstable, when the number of consecutive commutation failures in the AC/DC hybrid power grid is the current DC commutation number and a block occurs after the last commutation failure, Checking the stability of the AC/DC hybrid power grid to obtain a second checking result;

Step 4, when the current second verification result indicates that the power grid is stable, determine the protection strategy corresponding to the current DC power; wherein, the protection strategy corresponding to the current DC power is: the number of consecutive commutation failures that the current DC power can withstand The maximum value is the difference between the current DC commutation times and the first preset threshold, and when the number of consecutive commutation failures is the current DC commutation times, a block occurs. After the block occurs, the AC-DC hybrid grid can maintain safe and stable operation .

Preferably, wherein said method further comprises:

When the first check result indicates that the power grid is stable, if the current number of consecutive commutation failures is less than the second preset threshold, then update the number of consecutive commutation failures, and compare the current number of consecutive commutation failures with The sum of the third preset thresholds is used as the updated DC commutation times, and returns to step 2.

Preferably, wherein said method further comprises:

When the first checking result indicates that the power grid is stable, if the current number of consecutive commutation failures is equal to the second preset threshold, the protection strategy corresponding to the current DC power is directly determined.

Preferably, wherein said method further comprises:

When the current second checking result indicates that the power grid is unstable, and the difference between the current DC commutation times and the fourth preset threshold is greater than the fifth preset threshold, the current consecutive commutation failure times and the fourth preset The difference of the threshold is set as the updated DC commutation times, and the number of consecutive commutation failures of the AC-DC hybrid power grid is the current DC commutation times, and when a block occurs after the last commutation failure The grid stability is checked to re-obtain the second check result.

Preferably, wherein said method further comprises:

When the second check result indicates that the power grid is unstable, and the difference between the current DC commutation times and the fourth preset threshold is less than or equal to the fifth preset threshold, directly reduce the current DC commutation times according to the preset power adjustment strategy. power, and return to step 1.

Preferably, wherein said method further comprises:

When the first check result indicates that the power grid is unstable and the set current DC commutation times are the fifth preset threshold, adjust the operation mode of the AC-DC hybrid power grid, and return to step 1.

Preferably, the determination of the operation mode of the AC/DC/AC/DC hybrid power grid includes:

Determine the DC power level of the AC-DC hybrid grid, the AC section power of the sending end grid, the AC section power of the receiving end grid, and the generation load.

According to another aspect of the present invention, a system for determining the UHV DC commutation failure accelerated protection strategy is provided, the system comprising:

The setting unit is used to determine the operation mode of the AC-DC hybrid grid and set the current DC commutation times;

The first check result acquisition unit is used to perform a check on the AC/DC power grid when the number of consecutive commutation failures in the AC/DC hybrid power grid is the current DC commutation number and no blocking occurs after the last commutation failure. Check the stability of the hybrid power grid to obtain the first check result;

The second verification result acquisition unit is configured to: when the first verification result indicates that the power grid is unstable, when the number of consecutive commutation failures in the AC/DC hybrid power grid is the current number of DC commutation times and the last When a block occurs after commutation fails, check the stability of the AC/DC hybrid power grid to obtain a second check result;

A protection strategy determination unit, configured to determine a protection strategy corresponding to the current DC power when the current second verification result indicates that the power grid is stable; wherein, the protection strategy corresponding to the current DC power is: the current DC power can bear the continuous The maximum value of the number of commutation failures is the difference between the current number of DC commutations and the first preset threshold, and when the number of consecutive commutation failures is the current number of DC commutations, a block occurs. After the block occurs, the AC-DC hybrid grid Able to maintain safe and stable operation.

Preferably, wherein said system also includes:

A DC commutation times updating unit, configured to update the consecutive times of commutation failures if the current number of consecutive commutation failures is less than a second preset threshold when the first check result indicates that the power grid is stable, and set The sum of the current consecutive commutation failure times and the third preset threshold is used as the updated DC commutation times, and enters into the first verification result acquisition unit.

Preferably, the protection strategy determining unit is further configured to:

When the first checking result indicates that the power grid is stable, if the current number of consecutive commutation failures is equal to the second preset threshold, the protection strategy corresponding to the current DC power is directly determined.

Preferably, the second verification result acquisition unit further includes:

When the current second checking result indicates that the power grid is unstable, and the difference between the current DC commutation times and the fourth preset threshold is greater than the fifth preset threshold, the current consecutive commutation failure times and the fourth preset The difference of the threshold is set as the updated DC commutation times, and the number of consecutive commutation failures of the AC-DC hybrid power grid is the current DC commutation times, and when a block occurs after the last commutation failure The grid stability is checked to re-obtain the second check result.

Preferably, wherein said system also includes:

A DC power adjustment unit, configured to adjust the AC/DC power grid when the second check result indicates that the power grid is unstable, and the difference between the current DC commutation times and the fourth preset threshold is less than or equal to the fifth preset threshold. The operation mode of the hybrid power grid, and enter the setting unit.

Preferably, wherein said system also includes:

a DC power adjustment unit, configured to directly reduce the current DC power according to a preset power adjustment strategy when the first check result indicates that the grid is unstable and the current number of DC commutation times is the fifth preset threshold, and enter the setup unit.

Preferably, the setting unit determines the operation mode of the AC/DC/AC/DC hybrid power grid, including:

Determine the DC power level of the AC-DC hybrid grid, the AC section power of the sending end grid, the AC section power of the receiving end grid, and the generation load.

The present invention provides a method and system for determining an accelerated protection strategy for UHV DC commutation failure, including: determining the operation mode of the AC-DC hybrid power grid, and setting the current DC commutation times as the first preset number threshold; The AC/DC hybrid power grid checks the stability of the AC/DC hybrid power grid when the number of consecutive commutation failures is the current DC commutation number and no blockage occurs after the last commutation failure, to Obtain a first check result; when the first check result indicates that the power grid is unstable, when the number of consecutive commutation failures in the AC/DC hybrid power grid is the current number of DC commutation times and after the last commutation failure When a block occurs, check the stability of the AC/DC hybrid grid to obtain a second check result; when the current second check result indicates that the grid is stable, determine that the protection strategy corresponding to the current DC power is the current The maximum number of consecutive commutation failures that can be tolerated by the DC power is the difference between the current DC commutation times and the first preset threshold, and when the number of continuous commutation failures is the current DC commutation times, blocking occurs, and After the blockage, the AC-DC hybrid power grid can maintain safe and stable operation. The method for determining the DC commutation failure protection strategy of the large-scale AC-DC hybrid power grid of the present invention is simple and easy, can significantly improve the calculation efficiency in the DC commutation failure calculation, and save manpower and material resources and other costs.

Description of drawings

A more complete understanding of the exemplary embodiments of the present invention can be had by referring to the following drawings:

Figure 1 is a schematic diagram of the verification process of the protection strategy for DC commutation failure to ensure the safe and stable operation of large-scale AC-DC hybrid power grid;

Figure 2(a) is the bipolar power change diagram after two consecutive commutation failures in DC;

Figure 2(b) is the bipolar power change diagram when the third block occurs after two consecutive DC commutation failures;

Fig. 3(a) is a curve diagram of DC unipolar power change after two consecutive commutation failures in DC;

Fig. 3(b) is the DC unipolar power change curve after three consecutive DC commutation failures;

Fig. 4 is a flow chart of a determination method 400 of an UHV DC commutation failure acceleration protection strategy according to an embodiment of the present invention;

Fig. 5 is an example diagram of a method for determining the DC commutation failure acceleration protection strategy of an AC-DC hybrid power grid according to an embodiment of the present invention; and

Fig. 6 is a schematic structural diagram of a system 600 for determining an accelerated protection strategy for UHV DC commutation failure according to an embodiment of the present invention.

Detailed ways

Exemplary embodiments of the present invention will now be described with reference to the drawings; however, the present invention may be embodied in many different forms and are not limited to the embodiments described herein, which are provided for the purpose of exhaustively and completely disclosing the present invention. invention and fully convey the scope of the invention to those skilled in the art. The terms used in the exemplary embodiments shown in the drawings are not limiting of the present invention. In the figures, the same units/elements are given the same reference numerals.

Unless otherwise stated, the terms (including scientific and technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it can be understood that the terms defined by commonly used dictionaries should be understood as having consistent meanings in the context of their related fields, and should not be understood as idealized or overly formal meanings.

Fig. 4 is a flowchart of a method 400 for determining an accelerated protection strategy for UHV DC commutation failure according to an embodiment of the present invention. As shown in Figure 4, the method for determining the DC commutation failure protection strategy for a large-scale AC-DC hybrid power grid provided by the embodiment of the present invention is simple and easy, and can significantly improve the calculation efficiency in the calculation of DC commutation failure, saving manpower and material resources and other costs . The method 400 for determining the acceleration protection strategy for UHV DC commutation failure provided by the embodiment of the present invention starts at step 401. In step 401, the operation mode of the AC/DC hybrid power grid is determined, and the current number of DC commutation times is set.

Preferably, the determination of the operation mode of the AC/DC/AC/DC hybrid power grid includes:

Determine the DC power level of the AC-DC hybrid grid, the AC section power of the sending end grid, the AC section power of the receiving end grid, and the generation load.

In the embodiment of the present invention, when calculating the DC commutation failure, it is necessary to determine the DC power level P0, the AC section power of the sending end grid, the AC section power of the receiving end grid, and the power generation load, so that the AC/DC hybrid grid is at Operating status.

For the setting of the number of DC commutation times, the minimum value of the current DC commutation times can be 2, generally 3, because at least 2 times of commutation failures are checked.

In step 402, when the number of consecutive commutation failures of the AC/DC hybrid grid is the current DC commutation number and no lockout occurs after the last commutation failure, the stability of the AC/DC hybrid grid Checking is performed to obtain a first checking result.

In step 403, when the first verification result indicates that the power grid is unstable, when the number of consecutive commutation failures in the AC/DC hybrid power grid is the current number of DC commutations and a block occurs after the last commutation failure , checking the stability of the AC/DC hybrid power grid to obtain a second checking result.

Preferably, wherein said method further comprises:

When the first check result indicates that the power grid is stable, if the current number of consecutive commutation failures is less than the second preset threshold, then update the number of consecutive commutation failures, and compare the current number of consecutive commutation failures with The sum of the third preset thresholds is used as the updated DC commutation times, and the process returns to step 402 .

Preferably, wherein said method further comprises:

When the first checking result indicates that the power grid is stable, if the current number of consecutive commutation failures is equal to the second preset threshold, the protection strategy corresponding to the current DC power is directly determined.

For the existing AC/DC power grid, at most 12 commutation failures are checked, at least 2 commutation failures are checked, and each check is performed in sequence according to the number of commutation failures. Therefore, in the embodiment of the present invention, the first preset threshold value is set to 1, the second preset threshold value is 12, the third preset threshold value is 1, the fourth preset threshold value is 1, and the fifth preset threshold value is 2 .

In the embodiment of the present invention, "commutation failure N+1" indicates that lockup occurs after N+1 commutation failures occur.

For example, if the current number of DC commutation is set to 3, first obtain the first check result when 3 commutation failures occur and no blockage occurs after the last commutation failure, and then perform the first check result judge. Wherein, if the first check result indicates that the AC-DC hybrid power grid is unstable, then for the AC-DC hybrid power grid, when DC commutation failures occur three times in a row, and when a block occurs after the third commutation failure The stability of the power grid is checked, that is, the "commutation failure 2+1" check, and the second check result is obtained.

If the first check result indicates that the AC/DC hybrid power grid is stable, and since the current number of consecutive commutation failures 3 is less than the second preset threshold value 12, the current consecutive commutation failure times are updated, and the current consecutive commutation failures are updated Add 1 to the failure times 3 to get 4 as the updated DC commutation times, and return to step 402 .

For example, if the current DC commutation times are set to 12. Then at first obtain the first verification result when 12 commutation failures and no blockage occurs after the last commutation failure, and then judge the first verification result.

Wherein, if the first check result indicates that the AC/DC hybrid power grid is unstable, the “commutation failure 11+1” check is performed, that is, the DC is blocked when the 12th commutation failure occurs after 11 consecutive commutation failures. , and obtain the second verification result.

If the first check result indicates that the AC/DC hybrid power grid is stable, and since the current number of consecutive commutation failures 12 is equal to the second preset threshold 12, it means that the current number of commutation failures has reached the maximum value, so directly determine the current The protection strategy corresponding to the DC power.

Preferably, wherein said method further comprises:

When the first check result indicates that the power grid is unstable and the current DC commutation times set is the fifth preset threshold, the current DC power is directly reduced according to the preset power regulation strategy, and the process returns to step 401.

For example, if the current DC commutation times are set to 2, and the first check result at this time indicates that the power grid is unstable, then directly reduce the current DC power according to the preset power regulation strategy, and return to step 401 to reduce The commutation failure check is performed on the reduced DC power, so as to determine the protection strategy corresponding to the reduced DC power.

In step 404, when the current second verification result indicates that the power grid is stable, determine the protection strategy corresponding to the current DC power; wherein, the protection strategy corresponding to the current DC power is: the number of consecutive commutation failures that the current DC power can withstand The maximum value of is the difference between the current DC commutation times and the first preset threshold, and when the number of consecutive commutation failures is the current DC commutation times, a block occurs, and the AC-DC hybrid grid can remain safe and stable after the block occurs run.

For example, when the first preset threshold is 1, if the current number of DC commutation is 11, after performing "commutation failure 10+1" on the AC-DC hybrid grid, it is determined that the second check result indicates that the grid is stable , then it is determined that the protection strategy corresponding to the current DC power is: the maximum number of consecutive commutation failures that the current DC power can withstand is 10, and a block occurs when the number of consecutive commutation failures is the 11th, and the AC The DC hybrid grid can maintain safe and stable operation.

Preferably, wherein said method further comprises:

When the current second checking result indicates that the power grid is unstable, and the difference between the current DC commutation times and the fourth preset threshold is greater than the fifth preset threshold, the current consecutive commutation failure times and the fourth preset The difference of the threshold is set as the updated DC commutation times, and the number of consecutive commutation failures of the AC-DC hybrid power grid is the current DC commutation times, and when a block occurs after the last commutation failure The grid stability is checked to re-obtain the second check result.

Preferably, wherein said method further comprises:

When the second checking result indicates that the grid is unstable, and the difference between the current DC commutation times and the fourth preset threshold is less than or equal to the fifth preset threshold, adjusting the operation mode of the AC/DC hybrid grid, And return to step 401.

For example, if the current number of DC commutations is 11, after performing "commutation failure 10+1" on the AC/DC hybrid power grid, it is determined that the second check result indicates that the power grid is unstable, and the current DC commutation times decrease If the value 10 of 1 is greater than 2, the current number of consecutive commutation failures minus 1 will be used as the updated DC commutation number, and the number of consecutive commutation failures in the AC/DC hybrid power grid will be 9, And check the stability of the power grid when the blockage occurs after the tenth commutation failure to re-obtain the second check result; and determine whether to continue the check or directly check according to the grid stability indicated by the second check result Determine protection strategies or reduce current DC power.

Wherein, when the second checking result indicates that the grid stability is stable, the protection strategy is directly determined.

Wherein, when the second check result indicates that the grid stability is unstable, and the difference between the current DC commutation times and the fourth preset threshold is larger than the fifth preset threshold, the current consecutive commutation failure times and The difference between the fourth preset threshold is used as the updated DC commutation times, and the number of consecutive commutation failures for the AC-DC hybrid power grid is the current DC commutation times minus 1, and after another commutation failure Check the stability of the power grid when the blockage occurs, so as to obtain the second check result again, and continue to check.

Wherein, when the second checking result indicates that the grid stability is unstable, and the value of the current DC commutation number minus 1 is less than or equal to 2, that is, when the current DC commutation number is 3, it indicates that the second checking result is the first 2 phase commutation failures, and the stability of the power grid is unstable when locking occurs after the third failure, and the current DC power is reduced.

Fig. 5 is an example diagram of a method for determining an accelerated protection strategy for DC commutation failure in an AC/DC hybrid power grid according to an embodiment of the present invention. As shown in Figure 5, in the real-time mode of the present invention, the first preset threshold value is set to 2, and the second preset threshold value is set to 12. The steps of the grid DC commutation failure acceleration protection strategy include the following steps:

Step 1: Select the basic operation mode of the power grid, determine the DC power level P0, the AC section power of the sending end grid, the AC section power of the receiving end grid, and the power generation load, and calculate the number of DC commutation according to the first preset frequency threshold 3 Initialize settings.

Step 2, check the DC commutation failure.

Specifically, this step includes 10 small steps, and the power grid stability check process in each step includes the stability check of the sending end power grid and the receiving end power grid shown in Figure 1. Specific steps include:

(1) Check the stability of the large-scale AC-DC hybrid power grid after the DC commutation fails twice.

If the power grid is unstable after the DC secondary commutation fails, directly follow the preset power adjustment strategy to reduce the DC power and continue the calibration;

If the power grid is stable after 2 commutation failures of DC, perform 3 commutation failure checks;

If the power grid is unstable after 3 DC commutation failures, then check "commutation failure 2+1", that is, when the third commutation failure occurs after 2 consecutive commutation failures, the DC will be blocked. If "commutation failure 2+ If the power grid is stable after 1", go to step 3. If the power grid is unstable after "commutation failure 2+1", reduce the DC power according to the preset power adjustment strategy and continue to check;

If the power grid is stable after 3 DC commutation failures, check the stability of the large AC-DC hybrid power grid after 4 DC commutation failures.

(2) Check the stability of the large-scale AC-DC hybrid power grid after four DC commutation failures.

If the power grid is stable after four commutation failures of the DC, proceed to step (3);

If the power grid is unstable after 4 DC commutation failures, then check "commutation failure 3+1", if the power grid is stable after "commutation failure 3+1", go to step 3; After ", the power grid is unstable, then continue to check "commutation failure 2+1", and the check process after "commutation failure 2+1" is shown in step (1).

(3) Check the stability of the large-scale AC-DC hybrid power grid after 5 DC commutation failures.

If the grid is stable after 5 DC phase commutation failures, proceed to step (4);

If the power grid is unstable after 5 DC commutation failures, check "commutation failure 4+1", if the power grid is stable after "commutation failure 4+1", go to step 3; if "commutation failure 4+1 After ", the power grid is unstable, then continue to check "commutation failure 3+1", and the check process after "commutation failure 3+1" is shown in step (2).

(4) Check the stability of the large-scale AC-DC hybrid power grid after six DC commutation failures.

If the power grid is stable after 6 phase commutation failures of the DC, proceed to step (5);

If the power grid is unstable after 6 DC commutation failures, check "commutation failure 5+1". If the power grid is stable after "commutation failure 5+1", go to step 3; if "commutation failure 5+1 After ", the power grid is unstable, then continue to check "commutation failure 4+1", and the check process after "commutation failure 4+1" is shown in step (3).

(5) Check the stability of the large-scale AC-DC hybrid power grid after 7 DC commutation failures.

If the grid is stable after 7 times of DC commutation fails, enter step (6);

If the power grid is unstable after 7 DC commutation failures, then check "commutation failure 6+1", if the power grid is stable after "commutation failure 6+1", go to step 3; if "commutation failure 6+1 After ", the power grid is unstable, then continue to check "commutation failure 5+1", and the check process after "commutation failure 5+1" is shown in step (4).

(6) Check the stability of the large-scale AC-DC hybrid power grid after 8 DC commutation failures.

If the power grid is stable after 8 times of DC commutation fails, then enter step (7);

If the power grid is unstable after 8 DC commutation failures, then check "commutation failure 7+1", if the power grid is stable after "commutation failure 7+1", go to step 3; if "commutation failure 7+1 After ", the power grid is unstable, then continue to check "commutation failure 6+1", and the check process after "commutation failure 6+1" is shown in step (5).

(7) Check the stability of the large-scale AC-DC hybrid power grid after 9 DC commutation failures.

If the power grid is stable after 9 times of DC commutation fails, then enter step (8);

If the power grid is unstable after 9 DC commutation failures, then check "commutation failure 8+1", if the power grid is stable after "commutation failure 8+1", go to step 3; if "commutation failure 8+1 After ", the power grid is unstable, then continue to check "commutation failure 7+1", and the check process after "commutation failure 7+1" is shown in step (6).

(8) Check the stability of the large-scale AC-DC hybrid power grid after 10 DC commutation failures.

If the power grid is stable after 10 times of DC commutation fails, then enter step (9);

If the power grid is unstable after 10 DC commutation failures, then check "commutation failure 9+1", if the power grid is stable after "commutation failure 9+1", go to step 3; if "commutation failure 9+1 After ", the power grid is unstable, then continue to check "commutation failure 8+1", and the check process after "commutation failure 8+1" is shown in step (7).

(9) Check the stability of the large-scale AC-DC hybrid power grid after 11 DC commutation failures.

If the grid is stable after 11 DC commutation failures, proceed to step (10);

If the power grid is unstable after 11 DC commutation failures, then check "commutation failure 10+1", if the power grid is stable after "commutation failure 10+1", go to step 3; if "commutation failure 10+1 After ", the power grid is unstable, then continue to check "commutation failure 9+1", and the checking process after "commutation failure 9+1" is shown in step (8).

(10) Check the stability of the large-scale AC-DC hybrid power grid after 12 DC commutation failures.

If the power grid is stable after 12 DC commutation failures, go to step 3; if the grid is unstable after 12 DC commutation failures, check "commutation failure 11+1", if "commutation failure 11+1" If the power grid is stable, go to step 3; if the power grid is unstable after "commutation failure 11+1", continue to check "commutation failure 10+1", see steps for the verification process after "commutation failure 10+1" (9);

Step 3, determine the commutation failure protection strategy corresponding to the current DC power.

In the embodiment of the present invention, if the grid is stable after the DC "commutation failure i+1", the DC limit takes a given DC power. Within the range of the DC limit, the DC can withstand a maximum of i commutation failures, and the DC The protection strategy is defined as: the DC maximum withstands i consecutive commutation failures, and the i+1th block is blocked; if the DC is stable after the number of commutation failures i = 12, the DC limit is a given DC power, within the range of the DC limit Inside, the DC can withstand a maximum of 12 commutation failures, and the DC protection strategy is defined as: DC can withstand a maximum of 11 consecutive commutation failures, and the 12th time is blocked.

Fig. 6 is a schematic structural diagram of a system 600 for determining an accelerated protection strategy for UHV DC commutation failure according to an embodiment of the present invention. As shown in Figure 6, the system 600 for determining the DC commutation failure acceleration protection strategy of the AC/DC hybrid power grid provided by the embodiment of the present invention includes: a setting unit 601, a first check result acquisition unit 602, a second check result An acquisition unit 603 and a protection policy determination unit 604 .

Preferably, the setting unit 601 is configured to determine the operation mode of the AC/DC hybrid power grid, and set the current DC commutation times as the first preset times threshold.

Preferably, the setting unit 601 determines the operation mode of the AC/DC/AC/DC hybrid grid, including:

Determine the DC power level of the AC-DC hybrid grid, the AC section power of the sending end grid, the AC section power of the receiving end grid, and the generation load.

Preferably, the first verification result acquisition unit 602 is used for when the number of consecutive commutation failures in the AC/DC hybrid power grid is the current DC commutation times and no blocking occurs after the last commutation failure , checking the stability of the AC/DC hybrid power grid to obtain a first checking result.

Preferably, the second verification result acquisition unit 603 is configured to: when the first verification result indicates that the power grid is unstable, when the number of consecutive commutation failures in the AC/DC hybrid power grid is the current DC commutation Phase times and when a lockout occurs after the last phase commutation fails, the stability of the AC/DC hybrid power grid is checked to obtain a second check result.

Preferably, the second checking result acquisition unit further includes: when the current second checking result indicates that the power grid is unstable, and the difference between the current DC commutation times and the fourth preset threshold is greater than the fifth preset threshold When setting the threshold, the difference between the current number of consecutive commutation failures and the fourth preset threshold is used as the updated DC commutation number, and the current number of consecutive commutation failures for the AC/DC hybrid power grid is the current The number of DC commutation times is reduced by 1, and the stability of the power grid when a blockage occurs after another commutation failure is checked, so as to obtain the second check result again.

Preferably, the protection strategy determination unit 604 is configured to determine the protection strategy corresponding to the current DC power when the current second checking result indicates that the power grid is stable; wherein, the protection strategy corresponding to the current DC power is: the current The maximum number of consecutive commutation failures that the DC power can withstand is the difference between the current DC commutation times and the first preset threshold, and when the number of continuous commutation failures is the current DC commutation times, a blocking occurs, and a blocking occurs The post-AC/DC hybrid power grid can maintain safe and stable operation.

Preferably, the protection strategy determining unit 604 is further configured to: when the first checking result indicates that the power grid is stable, if the current number of consecutive commutation failures is equal to the second preset threshold, directly determine the current Protection strategy corresponding to DC power.

Preferably, the system further includes: a DC commutation times updating unit, configured to: when the first check result indicates that the power grid is stable, if the current number of consecutive commutation failures is less than a second preset threshold, then The number of consecutive commutation failures is updated, and the sum of the current consecutive number of commutation failures and the third preset threshold is used as the updated DC commutation number, and enters the first verification result acquisition unit 602 .

Preferably, the system further includes: a DC power adjustment unit, configured to be used when the second check result indicates that the power grid is unstable, and the difference between the current DC commutation times and the fourth preset threshold is less than or equal to the fifth When the threshold is preset, the current DC power is directly reduced according to the preset power adjustment strategy, and enters the setting unit.

Preferably, the system further includes: a DC power adjustment unit, configured to adjust the AC power when the first checking result indicates that the power grid is unstable and the current number of DC commutation is the fifth preset threshold. The operation mode of the DC hybrid grid, and enter the setting unit.

The UHV DC commutation failure acceleration protection strategy determination system 600 in the embodiment of the present invention corresponds to the UHV DC commutation failure acceleration protection strategy determination method 400 in another embodiment of the present invention, and will not be repeated here.

The invention has been described with reference to a small number of embodiments. However, it is clear to a person skilled in the art that other embodiments than the invention disclosed above are equally within the scope of the invention, as defined by the appended patent claims.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise therein. All references to "a/the/the [means, component, etc.]" are to be construed openly as at least one instance of said means, component, etc., unless expressly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

Those skilled in the art should understand that the embodiments of the present application may be provided as methods, systems, or computer program products. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It should be understood that each process and/or block in the flowchart and/or block diagrams, and a combination of processes and/or blocks in the flowchart and/or block diagrams can be realized by computer program instructions. These computer program instructions may be provided to a general purpose computer, special purpose computer, embedded processor, or processor of other programmable data processing equipment to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing equipment produce a An apparatus for realizing the functions specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to operate in a specific manner, such that the instructions stored in the computer-readable memory produce an article of manufacture comprising instruction means, the instructions The device realizes the function specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions can also be loaded onto a computer or other programmable data processing device, causing a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process, thereby The instructions provide steps for implementing the functions specified in the flow chart or blocks of the flowchart and/or the block or blocks of the block diagrams.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the present invention can still be Any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention shall fall within the protection scope of the claims of the present invention.

Claims (14)

1. A method for determining the UHV DC commutation failure accelerated protection strategy, characterized in that the method comprises: Step 1, determine the operation mode of the AC-DC hybrid power grid, and set the current DC commutation times; Step 2, when the number of consecutive commutation failures of the AC/DC hybrid grid is the current DC commutation number and no blockage occurs after the last commutation failure, the stability of the AC/DC hybrid grid is checked checking, to obtain the first checking result; Step 3, when the first check result indicates that the power grid is unstable, when the number of consecutive commutation failures in the AC/DC hybrid power grid is the current DC commutation number and a block occurs after the last commutation failure, Checking the stability of the AC/DC hybrid power grid to obtain a second checking result; Step 4, when the current second verification result indicates that the power grid is stable, determine the protection strategy corresponding to the current DC power; wherein, the protection strategy corresponding to the current DC power is: the number of consecutive commutation failures that the current DC power can withstand The maximum value is the difference between the current DC commutation times and the first preset threshold, and when the number of consecutive commutation failures is the current DC commutation times, a block occurs. After the block occurs, the AC-DC hybrid grid can maintain safe and stable operation . 2. The method according to claim 1, characterized in that the method further comprises: When the first check result indicates that the power grid is stable, if the current number of consecutive commutation failures is less than the second preset threshold, then update the number of consecutive commutation failures, and compare the current number of consecutive commutation failures with The sum of the third preset thresholds is used as the updated DC commutation times, and returns to step 2. 3. The method according to claim 1, characterized in that the method further comprises: When the first checking result indicates that the power grid is stable, if the current number of consecutive commutation failures is equal to the second preset threshold, the protection strategy corresponding to the current DC power is directly determined. 4. The method according to claim 1, wherein the method further comprises: When the current second checking result indicates that the power grid is unstable, and the difference between the current DC commutation times and the fourth preset threshold is greater than the fifth preset threshold, the current consecutive commutation failure times and the fourth preset The difference of the threshold is set as the updated DC commutation times, and the number of consecutive commutation failures of the AC-DC hybrid power grid is the current DC commutation times, and when a block occurs after the last commutation failure The grid stability is checked to re-obtain the second check result. 5. The method according to claim 1, wherein the method further comprises: When the second check result indicates that the power grid is unstable, and the difference between the current DC commutation times and the fourth preset threshold is less than or equal to the fifth preset threshold, directly reduce the current DC commutation times according to the preset power adjustment strategy. power, and return to step 1. 6. The method according to claim 1, further comprising: When the first checking result indicates that the power grid is unstable and the set current DC commutation times are the fifth preset threshold, adjust the operation mode of the AC-DC hybrid power grid, and return to step 1. 7. The method according to claim 1, wherein said determining the operation mode of the AC/DC hybrid power grid comprises: Determine the DC power level of the AC-DC hybrid grid, the AC section power of the sending end grid, the AC section power of the receiving end grid, and the generation load. 8. A determination system for UHV DC commutation failure acceleration protection strategy, characterized in that the system includes: The setting unit is used to determine the operation mode of the AC-DC hybrid grid and set the current DC commutation times; The first check result acquisition unit is used to perform a check on the AC/DC power grid when the number of consecutive commutation failures in the AC/DC hybrid power grid is the current DC commutation number and no blocking occurs after the last commutation failure. Check the stability of the hybrid power grid to obtain the first check result; The second check result acquisition unit is configured to: when the first check result indicates that the power grid is unstable, when the number of consecutive commutation failures in the AC/DC hybrid power grid is the current number of DC commutation times and the last When a block occurs after commutation fails, check the stability of the AC/DC hybrid power grid to obtain a second check result; A protection strategy determination unit, configured to determine a protection strategy corresponding to the current DC power when the current second verification result indicates that the power grid is stable; wherein, the protection strategy corresponding to the current DC power is: the current DC power can bear the continuous The maximum value of the number of commutation failures is the difference between the current number of DC commutations and the first preset threshold, and when the number of consecutive commutation failures is the current number of DC commutations, a block occurs. After the block occurs, the AC-DC hybrid grid Able to maintain safe and stable operation. 9. The system according to claim 8, further comprising: A DC commutation times updating unit, configured to update the consecutive times of commutation failures if the current number of consecutive commutation failures is less than a second preset threshold when the first check result indicates that the power grid is stable, and set The sum of the current consecutive commutation failure times and the third preset threshold is used as the updated DC commutation times, and enters into the first verification result acquisition unit. 10. The system according to claim 8, wherein the protection policy determining unit is further configured to: When the first checking result indicates that the power grid is stable, if the current number of consecutive commutation failures is equal to the second preset threshold, the protection strategy corresponding to the current DC power is directly determined. 11. The system according to claim 8, wherein the second verification result acquisition unit further comprises: When the current second checking result indicates that the power grid is unstable, and the difference between the current DC commutation times and the fourth preset threshold is greater than the fifth preset threshold, the current consecutive commutation failure times and the fourth preset The difference of the threshold is set as the updated DC commutation times, and the number of consecutive commutation failures of the AC-DC hybrid power grid is the current DC commutation times, and when a block occurs after the last commutation failure The grid stability is checked to re-obtain the second check result. 12. The system according to claim 8, further comprising: a DC power regulating unit, configured to directly follow the preset power grid when the second check result indicates that the power grid is unstable, and the difference between the current DC commutation times and the fourth preset threshold is less than or equal to the fifth preset threshold. The power regulation strategy reduces the current DC power and enters the setup unit. 13. The system according to claim 8, further comprising: a DC power adjustment unit, configured to adjust the operation mode of the AC/DC hybrid grid when the first check result indicates that the grid is unstable and the current number of DC commutation times is the fifth preset threshold, and enter Set up the unit. 14. The system according to claim 8, wherein the setting unit determines the operation mode of the AC/DC/AC/DC hybrid power grid, comprising: Determine the DC power level of the AC-DC hybrid grid, the AC section power of the sending end grid, the AC section power of the receiving end grid, and the generation load.