A dc transmission line asynchronous protection method and system based on voltage short window relay

Abstract

The application discloses a DC transmission line asynchronous protection method and system based on a voltage short window relay, and comprises the following steps: calculating a voltage differential value of a rectifier side of a DC transmission line; determining a positive rate of change voltage differential value of the rectifier side of the DC transmission line according to the voltage differential value; constructing a first criterion of DC transmission line asynchronous protection according to the positive rate of change voltage differential value and a voltage short window relay setting value; calculating current differential values of the rectifier side and an inverter side of the DC transmission line; constructing a second criterion of DC transmission line asynchronous protection according to the current differential values of the rectifier side and the inverter side and a sudden change asynchronous differential relay setting value; and when the first criterion and the second criterion are simultaneously satisfied, the whole protection is operated. The method can greatly improve the sensitivity of high-resistance fault protection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of relay protection, in particular to a DC transmission line asynchronous protection method and system based on a voltage short window relay. BACKGROUND

[0002] Since wind energy, solar energy and other renewable energy are intermittent energy, the traditional power equipment, power grid structure and operation technology have limited capacity for their consumption, and most of the renewable energy cannot be effectively utilized. With more and more large-scale renewable energy connected to the power grid, new technologies, new equipment and new power grid structures must be adopted to meet the profound changes in the energy pattern. Flexible DC power grid is one of the effective technical means to solve the grid connection of intermittent new energy.

[0003] At present, the existing flexible DC transmission line protection takes the traveling wave protection and the differential under-voltage protection as the main protection, which can quickly respond to the DC line fault (within 2ms), but has poor transition resistance tolerance. The current differential protection can respond to the high resistance fault of the flexible DC line, but the delay is relatively long (hundreds of milliseconds or even seconds). In order to further accelerate the action speed of the metallic fault protection and greatly improve the action speed of the high resistance fault protection, a full-line fast-acting high-reliability high-speed flexible DC transmission line protection must be configured. SUMMARY

[0004] In view of the above technical problems, the present application provides a DC transmission line asynchronous protection method based on a voltage short window relay, comprising:

[0005] calculating a voltage differential value of a rectifier side of a DC transmission line, and determining a positive rate of change voltage differential value of the rectifier side of the DC transmission line according to the voltage differential value;

[0006] constructing a first criterion of DC transmission line asynchronous protection according to the positive rate of change voltage differential value and a voltage short window relay setting value;

[0007] calculating current differential values of the rectifier side and the inverter side of the DC transmission line;

[0008] constructing a second criterion of DC transmission line asynchronous protection according to the current differential values of the rectifier side and the inverter side, and a sudden change asynchronous differential relay setting value;

[0009] the whole protection acts when the first criterion and the second criterion are met at the same time.

[0010] Further, calculating a voltage differential value of a rectifier side of a DC transmission line, and determining a positive rate of change voltage differential value of the rectifier side of the DC transmission line according to the voltage differential value, comprises:

[0011] collecting a voltage value of the rectifier side of the DC transmission line at time k and Voltage value at time Where k represents the current time of the protection calculation. This is the sampling interval time;

[0012] According to the voltage value and Calculate the voltage difference value on the rectifier side of the DC transmission line at time k. , ;

[0013] The positive rate of change voltage difference value on the rectifier side is determined based on the voltage difference value on the rectifier side. When the voltage difference is positive, the positive rate of change voltage difference at time k is equal to the voltage difference at the same time; when the voltage difference is negative or zero, the positive rate of change voltage difference at time k is equal to 0.

[0014] Furthermore, based on the positive rate of change voltage difference value and voltage short window relay setting The first criterion for constructing asynchronous protection for DC transmission lines ,

[0015] Where t0 is the protection start time, Calculate the window length for the floating threshold.

[0016] Furthermore, the current difference between the rectifier and inverter sides of the DC transmission line is calculated, including:

[0017] Collect the current value at time k on the rectifier side of the DC transmission line. and Current value at time And according to the current value and Calculate the current difference on the rectifier side of the DC transmission line at time k. , Where, k represents the current time of the protection calculation, This is the sampling interval time;

[0018] Data collection from the inverter side of DC transmission lines Current value at time and Current value at time And based on the current value and ,calculate The current difference value on the inverter side of the DC transmission line at time [time]. , ;in, Delay the transmission channel of the DC transmission line.

[0019] Further, according to the current difference value of the rectifier side and the inverter side and the sudden change asynchronous differential relay setting value, a second criterion of the HVDC line asynchronous protection is constructed, comprising:

[0020] The second criterion is

[0021] Wherein, is the sudden change asynchronous differential relay setting value, is the sampling point number between t0 and t, is the current difference value of the HVDC line rectifier side at k moment, is the current difference value of the HVDC line inverter side at k moment, is the transmission channel delay of the HVDC line.

[0022] The application also provides a HVDC line asynchronous protection system based on the voltage short window relay, comprising:

[0023] A voltage difference value calculation module is configured to calculate the voltage difference value of the HVDC line rectifier side, and determine the positive rate voltage difference value of the HVDC line rectifier side according to the voltage difference value.

[0024] A first criterion construction module is configured to construct the first criterion of the HVDC line asynchronous protection according to the positive rate voltage difference value and the voltage short window relay setting value.

[0025] A current difference value calculation module is configured to calculate the current difference value of the HVDC line rectifier side and the inverter side.

[0026] A second criterion construction module is configured to construct the second criterion of the HVDC line asynchronous protection according to the current difference value of the rectifier side and the inverter side and the sudden change asynchronous differential relay setting value.

[0027] A protection module is configured to act when the first criterion and the second criterion are met simultaneously.

[0028] Further, the voltage difference value calculation module comprises:

[0029] A voltage value acquisition submodule is configured to acquire the voltage value of the HVDC line rectifier side at k moment and the voltage value at k moment .

[0030] A voltage difference value calculation submodule is configured to calculate the voltage difference value of the HVDC line rectifier side at k moment according to the voltage value and .

[0031] The rate-of-change voltage difference calculation submodule is used to determine the positive rate-of-change voltage difference value on the rectifier side based on the rectifier side voltage difference value. When the voltage difference is positive, the positive rate of change voltage difference at time k is equal to the voltage difference at the same time; when the voltage difference is negative or zero, the positive rate of change voltage difference at time k is equal to 0.

[0032] Furthermore, the current difference calculation module includes:

[0033] The current differential acquisition submodule is used to acquire the current value at time k on the rectifier side of the DC transmission line. and Current value at time And according to the current value and Calculate the current difference on the rectifier side of the DC transmission line at time k. ;in, This is the sampling interval time;

[0034] The current differential value calculation submodule is used to collect data from the inverter side of a DC transmission line. Current value at time and Current value at time And based on the current value and ,calculate The current difference value on the inverter side of the DC transmission line at time [time]. ;in, Delay the transmission channel of the DC transmission line.

[0035] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor.

[0036] The present invention also provides a readable storage medium on which a computer program is stored.

[0037] This invention provides an asynchronous protection method and system for DC transmission lines based on a voltage short-window relay. In the event of a metallic fault or high-resistance fault along the entire flexible DC transmission line, it can operate solely based on a single-ended quantity from the M side, without requiring fault current from the N side. This invention reliably operates within 2ms after startup. In the event of an F3 fault outside the flexible DC transmission line area, this invention reliably does not operate. This protection method significantly improves the operating speed of high-resistance fault protection, achieving rapid operation across the entire line. Attached Figure Description

[0038] Figure 1This is a flowchart illustrating an asynchronous protection method for DC transmission lines based on a voltage short-window relay provided by the present invention.

[0039] Figure 2 This is a schematic diagram of the DC system involved in the present invention;

[0040] Figure 3 This invention relates to an asynchronous differential protection timing diagram;

[0041] Figure 4 This is the asynchronous protection logic involved in this invention example;

[0042] Figure 5 This is a schematic diagram of the structure of an asynchronous protection system for DC transmission lines based on a voltage short-window relay provided by the present invention. Detailed Implementation

[0043] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0044] A schematic diagram of the DC system involved in this invention is attached. Figure 2 As shown. The rectifier side is the M side, and the inverter side is the N side. The DC protection on the M side of pole I line is taken as the research object. This represents the current value on the M side of the DC line. This represents the current value on the N side of the DC line, with the positive direction of the current always pointing from the pole bus to the line.

[0045] Based on the aforementioned DC system, this invention provides an asynchronous protection method for DC transmission lines based on a voltage short-window relay, the process of which is as follows: Figure 1 As shown, it includes the following steps:

[0046] Step S101: Calculate the voltage difference value on the rectifier side of the DC transmission line, and determine the positive rate of change voltage difference value on the rectifier side of the DC transmission line based on the voltage difference value.

[0047] Collect the voltage value at time k on the rectifier side of the DC transmission line. and Voltage value at time Where k represents the current time of the protection calculation. This is the sampling interval time;

[0048] According to the voltage value and Calculate the voltage difference value on the rectifier side of the DC transmission line at time k. , ;

[0049] The positive rate of change voltage difference value on the rectifier side is determined based on the voltage difference value on the rectifier side. When the voltage difference is positive, the voltage difference with positive rate of change at time k is equal to the voltage difference at the same time; when the voltage difference is negative or zero, the voltage difference with positive rate of change at time k is equal to 0. Its application scenarios are... Figure 2 The protective installation location of the flexible DC transmission line is shown.

[0050]

[0051] When calculating the window length for the floating threshold, it is recommended that T < 3ms.

[0052] The voltage short-window relay setting is configured to avoid metallic short circuits outside the zone.

[0053] Step S102: Based on the positive rate of change voltage differential value and the voltage short window relay setting, construct the first criterion for asynchronous protection of DC transmission lines.

[0054] The first criterion is

[0055] Where t0 is the protection start time, Calculate the window length for the floating threshold. Set the voltage short-window relay value.

[0056] Step S103: Calculate the current difference between the rectifier side and the inverter side of the DC transmission line.

[0057] Collect the current value at time k on the rectifier side of the DC transmission line. and Current value at time And according to the current value and Calculate the current difference on the rectifier side of the DC transmission line at time k. , Where, k represents the current time of the protection calculation, This is the sampling interval time;

[0058] Data collection from the inverter side of DC transmission lines Current value at time and Current value at time And based on the current value and ,calculate The current difference value on the inverter side of the DC transmission line at time [time]. , ;in, Delay the transmission channel of the DC transmission line.

[0059] Step S104: Based on the current difference between the rectifier side and the inverter side, and the setting of the asynchronous differential relay for sudden change, a second criterion for asynchronous protection of DC transmission lines is constructed.

[0060] The second criterion is

[0061] in, The setting value for the asynchronous differential relay with sudden change is determined based on the sensitivity setting during a high-resistance fault at the end of a DC line. 1 This represents the number of sampling points between t0 and t.

[0062] Step S105: When the first criterion and the second criterion are met simultaneously, the voltage short window relay and the sudden change asynchronous differential relay protection are activated.

[0063] The timing diagram for asynchronous protection of the entire high-speed flexible DC transmission line is attached. Figure 3 As shown. For DC line protection on the M side, the protection criterion at time k is determined by the current value on the M side at time k and the current value on the N side. The current value at any given time constitutes the current value.

[0064] The asynchronous protection logic for the entire high-speed flexible DC transmission line is as follows: Figure 4 As shown, the voltage short-window relay and the sudden change asynchronous differential relay are output through an AND gate logic output.

[0065] Application examples are as follows:

[0066] (1) As attached Figure 2 As shown, the DC protection on the M side of Pole I line is taken as the research object. The protection on the N side of Pole I line and the protection on Pole II line are the same and will not be described again.

[0067] (2) Collect the line current on the M side at time k ,collection DC line M-side current value at time 1 Calculate the difference in current on the M side of the DC line at time k. .collection Current on the N-side line at time ,collection Current on the N-side of the line at time ,calculate The difference in current on the N side of the DC line at any given time Collect the line voltage on side M at time k. ,collection DC line M-side voltage value at time 1 Calculate the voltage difference on the M side of the DC line at time k. ,calculate .

[0068] (3) Calculate , if , then go to step (4); if not, protection returns.

[0069] (4) Calculate , if , then protection action exits, otherwise, protection returns.

[0070] Based on the same inventive concept, the application also provides a DC transmission line asynchronous protection system 500 based on voltage short window relay, as shown in Figure 5 , comprising:

[0071] A voltage difference value calculation module 510 is configured to calculate a voltage difference value of a rectifier side of a DC transmission line, and determine a positive rate of change voltage difference value of the rectifier side of the DC transmission line according to the voltage difference value.

[0072] A first criterion construction module 520 is configured to construct a first criterion of DC transmission line asynchronous protection according to the positive rate of change voltage difference value and a voltage short window relay setting value.

[0073] A current difference value calculation module 530 is configured to calculate current difference values of the rectifier side and an inverter side of the DC transmission line.

[0074] A second criterion construction module 540 is configured to construct a second criterion of DC transmission line asynchronous protection according to the current difference values of the rectifier side and the inverter side, and a sudden change asynchronous differential relay setting value.

[0075] A protection module 550 is configured to make voltage short window relay and sudden change asynchronous differential relay protection actions when the first criterion and the second criterion are both satisfied.

[0076] Further, the voltage difference value calculation module comprises:

[0077] A voltage value acquisition sub-module is configured to acquire voltage values of the rectifier side of the DC transmission line at time k and time .

[0078] A voltage difference value calculation sub-module is configured to calculate a voltage difference value of the rectifier side of the DC transmission line at time k according to the voltage values .

[0079] A rate of change voltage difference value calculation sub-module is configured to determine a positive rate of change voltage difference value of the rectifier side as ​When the voltage difference is positive, the positive rate of change voltage difference at time k is equal to the voltage difference at the same time; when the voltage difference is negative or zero, the positive rate of change voltage difference at time k is equal to 0.

[0080] Furthermore, the current difference calculation module includes:

[0081] The current differential acquisition submodule is used to acquire the current value at time k on the rectifier side of the DC transmission line. and Current value at time And according to the current value and Calculate the current difference on the rectifier side of the DC transmission line at time k. ;in, This is the sampling interval time;

[0082] The current differential value calculation submodule is used to collect data from the inverter side of a DC transmission line. Current value at time and Current value at time And based on the current value and ,calculate The current difference value on the inverter side of the DC transmission line at time [time]. ;in, Delay the transmission channel of the DC transmission line.

[0083] This invention provides an asynchronous protection method and system for DC transmission lines based on a voltage short-window relay. In the event of a metallic fault or high-resistance fault along the entire flexible DC transmission line, it can operate solely based on a single-ended quantity from the M side, without requiring fault current from the N side. This invention reliably operates within 2ms after startup. In the event of an F3 fault outside the flexible DC transmission line area, this invention reliably does not operate. This protection method significantly improves the operating speed of high-resistance fault protection, achieving rapid operation across the entire line.

[0084] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can 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.) containing computer-usable program code.

[0085] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flow or blocks Figure 1 one or more flow or blocks

[0086] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the function specified in the flowchart block or blocks. Figure 1 one or more flow or blocks Figure 1 one or more flow or blocks

[0087] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. Figure 1 one or more flow or blocks Figure 1 one or more flow or blocks

[0088] Finally, it should be noted that the above-mentioned embodiments are merely used to illustrate the technical solutions of the present application, but are not intended to limit the present application. Although the present application is described in detail with reference to the above embodiments, those skilled in the art should understand that the specific embodiments of the present application can be modified or replaced, and any modification or replacement without departing from the spirit and scope of the present application should be covered in the scope of the claims of the present application.

Claims

1. An asynchronous protection method for DC transmission lines based on a voltage short-window relay, characterized in that, include: Calculate the voltage difference value on the rectifier side of the DC transmission line, and determine the positive rate of change voltage difference value on the rectifier side of the DC transmission line based on the voltage difference value; Based on the positive rate of change voltage difference value and the voltage short window relay setting, a first criterion for asynchronous protection of DC transmission lines is constructed. Calculate the current difference between the rectifier side and the inverter side of a DC transmission line; Based on the current difference between the rectifier side and the inverter side, and the setting of the asynchronous differential relay for sudden changes, a second criterion for asynchronous protection of DC transmission lines is constructed. The entire protective action occurs when both the first and second criteria are met simultaneously. Based on the positive rate of change voltage difference value and voltage short window relay setting The first criterion for constructing asynchronous protection for DC transmission lines , Where t0 is the protection start time, The window length is calculated for the floating threshold, and k is the current time of the protection calculation; Based on the current difference between the rectifier side and the inverter side, and the asynchronous differential relay setting for sudden changes, a second criterion for asynchronous protection of DC transmission lines is constructed, including: The second criterion is in, Set the value for the asynchronous differential relay with sudden change. The number of sampling points between t0 and t. Let be the current difference value on the rectifier side of the DC transmission line at time k. for The current difference value on the inverter side of the DC transmission line at any given time. Delay the transmission channel of the DC transmission line.

2. The method according to claim 1, characterized in that, Calculating the voltage difference value on the rectifier side of a DC transmission line, and determining the positive rate-of-change voltage difference value on the rectifier side of the DC transmission line based on the voltage difference value, including: Collect the voltage value at time k on the rectifier side of the DC transmission line. and Voltage value at time Where k represents the current time of the protection calculation. This is the sampling interval time; According to the voltage value and Calculate the voltage difference value on the rectifier side of the DC transmission line at time k. , ; The positive rate of change voltage difference value on the rectifier side is determined based on the voltage difference value on the rectifier side. When the voltage difference is positive, the positive rate of change voltage difference at time k is equal to the voltage difference at the same time; when the voltage difference is negative or zero, the positive rate of change voltage difference at time k is equal to 0.

3. The method according to claim 1, characterized in that, Calculate the current difference between the rectifier and inverter sides of a DC transmission line, including: Collect the current value at time k on the rectifier side of the DC transmission line. and Current value at time And according to the current value and Calculate the current difference on the rectifier side of the DC transmission line at time k. , Where k represents the current time of the protection calculation. This is the sampling interval time; Data collection from the inverter side of DC transmission lines Current value at time and Current value at time And based on the current value and ,calculate The current difference value on the inverter side of the DC transmission line at time [time]. , ;in, Delay the transmission channel of the DC transmission line.

4. An asynchronous protection system for DC transmission lines based on a voltage short-window relay, characterized in that, include: The voltage difference calculation module is used to calculate the voltage difference value on the rectifier side of the DC transmission line, and determine the positive rate of change voltage difference value on the rectifier side of the DC transmission line based on the voltage difference value. The first criterion construction module is used to construct the first criterion for asynchronous protection of DC transmission lines based on the positive rate of change voltage differential value and the voltage short window relay setting value. The current difference calculation module is used to calculate the current difference between the rectifier side and the inverter side of a DC transmission line. The second criterion construction module is used to construct a second criterion for asynchronous protection of DC transmission lines based on the current difference between the rectifier side and the inverter side, and the setting value of the asynchronous differential relay for sudden change. The protection module is used to activate the entire protection system when both the first and second criteria are met simultaneously. Based on the positive rate of change voltage difference value and voltage short window relay setting The first criterion for constructing asynchronous protection for DC transmission lines , Where t0 is the protection start time, The window length is calculated for the floating threshold, and k is the current time of the protection calculation; Based on the current difference between the rectifier side and the inverter side, and the asynchronous differential relay setting for sudden changes, a second criterion for asynchronous protection of DC transmission lines is constructed, including: The second criterion is in, Set the value for the asynchronous differential relay with sudden change. The number of sampling points between t0 and t. Let be the current difference value on the rectifier side of the DC transmission line at time k. for The current difference value on the inverter side of the DC transmission line at any given time. Delay the transmission channel of the DC transmission line.

5. The system according to claim 4, characterized in that, The voltage difference calculation module includes: The voltage acquisition submodule is used to acquire the voltage value at time k on the rectifier side of the DC transmission line. and Voltage value at time ;in This is the sampling interval time; The voltage difference calculation submodule is used to calculate the voltage value based on the voltage value. and Calculate the voltage difference value on the rectifier side of the DC transmission line at time k. ; The rate-of-change voltage difference calculation submodule is used to determine the positive rate-of-change voltage difference value on the rectifier side based on the rectifier side voltage difference value. When the voltage difference is positive, the positive rate of change voltage difference at time k is equal to the voltage difference at the same time; when the voltage difference is negative or zero, the positive rate of change voltage difference at time k is equal to 0.

6. The system according to claim 4, characterized in that, The current difference calculation module includes: The current differential acquisition submodule is used to acquire the current value at time k on the rectifier side of the DC transmission line. and Current value at time And according to the current value and Calculate the current difference on the rectifier side of the DC transmission line at time k. ;in, This is the sampling interval time; The current differential value calculation submodule is used to collect data from the inverter side of a DC transmission line. Current value at time and Current value at time And based on the current value and ,calculate The current difference value on the inverter side of the DC transmission line at time [time]. ;in, Delay the transmission channel of the DC transmission line.

7. An electronic device comprising a memory, a processor, and a computer program stored in the memory and capable of running on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 3.

8. A readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 3.

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