Distributed new energy distribution line-containing low-frequency load shedding method and system considering power direction

Abstract

The invention discloses a distributed new energy distribution line low-frequency load shedding method and system considering the power direction, and the method comprises the steps: firstly collecting the frequency of a power grid side of a distribution line, the frequency change rate and the power direction D of the distribution line, determining that the power direction is positive when the power of the distribution line is transmitted to a main grid, taking D as 1, and taking D as 1; if the power is transmitted to the load from the main network through the distribution line, the power direction is negative, and D is minus 1; when the frequency drop amplitude is set to be a threshold and the power direction is judged to be positive, the line cutting operation is not executed; when the frequency drop amplitude reaches a set threshold, the frequency change rate is lower than dfz1 / dt, and the power direction is negative, the T-cut line is delayed, and when the frequency change rate is lower than dfz2 / dt, and the power direction is negative, both dfz1 / dt and dfz2 / dt are negative values, and dfz1 / dtlt; and if dfz2 / dt, directly cutting off the circuit without delay. And the frequency recovery after the system fault can be promoted more quickly.

Description

Technical Field

[0001] The present invention belongs to the technical field of safe and stable control of electric power systems, and in particular relates to a method and system for low-frequency load reduction of a distributed renewable energy distribution line taking power direction into consideration. Background Art

[0002] With the large-scale grid connection of distributed renewable energy, the power flow direction of the distribution lines connecting distributed renewable energy to the main grid has changed significantly, from the previous unidirectional power flow of single-side power to a dual-line flow mode. The power flow of the distribution lines is greatly affected by the output of renewable energy. That is, when renewable energy is generated and the load is light, the power of the distribution lines is sent to the main grid. When the load is large and the output of renewable energy is small, the power of the distribution lines is disconnected from the grid.

[0003] When a serious accident occurs in the system, especially when a locking fault occurs in the DC feed-in or a large power line trips, the power balance is severely damaged and a large power gap occurs. By cutting off part of the load to make up for the power difference, the power generation and consumption balance is re-established to avoid further frequency decline, ensure that the system can still be interconnected and the generator is not disconnected from the grid, then the system can maintain continuous operation for a period of time, otherwise it will slide into system collapse and a large-scale power outage will occur in the region. At this time, the low-frequency load reduction device needs to be activated to cut off part of the load to ensure the rapid balance of power load.

[0004] However, the traditional low-frequency load shedding device does not take into account the possible power access after the connection of new energy. The positioning of the low-frequency load shedding device is still based on the matrix outlet, that is, when the system has low frequency, the power direction of the line is not considered, and the corresponding line is directly cut off according to the matrix outlet. At this time, the system may have low frequency and cut off a large number of power transmission distribution lines, resulting in the problem that the total load shedding of the low-frequency load shedding device is far lower than the preset value after the system failure, and there is a risk of further reduction in system frequency. Summary of the invention

[0005] The present invention provides a method and system for low-frequency load reduction of distributed renewable energy distribution lines taking power direction into consideration, which is used to solve the technical problem that the power direction of the lines is not considered and the corresponding lines are directly cut off according to the matrix outlets, which may cause system low frequency and cut off a large amount of power transmission distribution lines.

[0006] In a first aspect, the present invention provides a method for low-frequency load reduction of a distributed renewable energy distribution line taking into account power direction, comprising:

[0007] Obtain the frequency on the grid side of the distribution line, the frequency change rate on the grid side of the distribution line, and the power direction of the distribution line;

[0008] Determining whether the frequency on the grid side of the distribution line is lower than a set frequency threshold;

[0009] If the frequency on the grid side of the distribution line is lower than the set frequency threshold, determining whether the power direction of the distribution line is positive;

[0010] If it is not positive, determining whether the frequency change rate of the power distribution line grid side is within a preset threshold range;

[0011] If the frequency change rate on the grid side of the distribution line is within the preset threshold range, the distribution line is disconnected after a delay of T time.

[0012] In a second aspect, the present invention provides a low-frequency load reduction system for a distributed renewable energy distribution line taking into account power direction, comprising:

[0013] an acquisition module configured to acquire a frequency on a grid side of a distribution line, a frequency change rate on the grid side of the distribution line, and a power direction of the distribution line;

[0014] A first judgment module is configured to judge whether the frequency of the power distribution line grid side is lower than a set frequency threshold;

[0015] A second judgment module is configured to judge whether the power direction of the distribution line is positive if the frequency of the grid side of the distribution line is not lower than a set frequency threshold;

[0016] A third judgment module is configured to judge whether the frequency change rate of the power distribution line grid side is within a preset threshold range if it is not positive;

[0017] The cutting module is configured to cut off the distribution line after a delay of T time if the frequency change rate on the grid side of the distribution line is within a preset threshold range.

[0018] According to a third aspect, an electronic device is provided, comprising: at least one processor, and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can perform the steps of the method for low-frequency load reduction of a distribution line containing distributed new energy considering power direction according to any embodiment of the present invention.

[0019] In a fourth aspect, the present invention further provides a computer-readable storage medium having a computer program stored thereon. When the program instructions are executed by a processor, the processor executes the steps of a method for low-frequency load reduction of a distributed new energy distribution line taking into account power direction according to any embodiment of the present invention.

[0020] The present application discloses a method and system for reducing the load of a low-frequency distribution line containing distributed new energy sources that considers the power direction. First, the frequency, frequency change rate, and power direction D of the distribution line grid side are collected. When the power is sent from the distribution line to the main grid, the power direction is considered to be positive, and D is 1. When the power is sent from the main grid to the load through the distribution line, the power direction is considered to be negative, and D is -1. When the frequency drop amplitude sets a threshold fz, the line cutting operation is not performed when the power direction is judged to be positive. When the frequency drop amplitude sets a threshold fz and reaches the set threshold fz, the frequency change rate is lower than dfz1 / dt, and the power direction is negative, the line is cut with a delay of T. When the frequency change rate is lower than dfz2 / dt and the power direction is negative, dfz1 / dt and dfz2 / dt are both negative values, and |dfz1 / dt|<|dfz2 / dt|, the line is directly cut without delay, which can promote the frequency recovery after system failure more quickly. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 A flow chart of a method for low-frequency load reduction of a power distribution line containing distributed renewable energy and considering power direction provided by an embodiment of the present invention;

[0023] Figure 2 A structural block diagram of a low-frequency load reduction system for a distributed renewable energy distribution line taking into account power direction provided by an embodiment of the present invention;

[0024] Figure 3 It is a schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] See also Figure 1 , which shows a flow chart of a low-frequency load reduction method for a distributed new energy distribution line considering power direction in the present application.

[0027] like Figure 1 As shown, the low-frequency load reduction method for distributed renewable energy distribution lines considering power direction specifically includes the following steps:

[0028] Step S101, obtaining the frequency of the grid side of the distribution line, the frequency change rate of the grid side of the distribution line, and the power direction of the distribution line.

[0029] In this step, the voltage level of the distribution line is mainly 35kV, 10kV or 400V distribution line.

[0030] Step S102, determining whether the frequency on the grid side of the distribution line is lower than a set frequency threshold.

[0031] Specifically, after determining whether the frequency on the grid side of the distribution line is lower than the set frequency threshold, if the frequency on the grid side of the distribution line is not lower than the set frequency threshold, the low-frequency load reduction will not be implemented, that is, the distribution line will not be cut off.

[0032] Step S103: If the frequency of the power distribution line on the grid side is lower than the set frequency threshold, it is determined whether the power direction of the power distribution line is positive.

[0033] In this step, since a large number of distributed renewable energy sources are connected, the power direction is positive when the load is low and the renewable energy output is large, and the power direction is negative when the load is heavy and the renewable energy output is small.

[0034] Specifically, after determining whether the power direction of the distribution line is positive, if it is positive, the low-frequency load reduction will not be performed, that is, the distribution line will not be cut off.

[0035] Step S104: If it is not positive, determine whether the frequency change rate of the power distribution line grid side is within a preset threshold range.

[0036] In this step, after determining whether the frequency change rate on the grid side of the distribution line is within the preset threshold range, if the frequency change rate on the grid side of the distribution line is less than the minimum value in the preset threshold range, the distribution line is directly cut off without delay. If the frequency change rate on the grid side of the distribution line is greater than the maximum value in the preset threshold range, the low-frequency load reduction does not take effect, that is, the distribution line is not cut off.

[0037] Step S105: If the frequency change rate of the power distribution line on the grid side is within a preset threshold range, the power distribution line is disconnected after a delay of T time.

[0038] In summary, the method of the present application first collects the frequency, frequency change rate and power direction D of the distribution line grid side. When the power is sent from the distribution line to the main grid, the power direction is considered to be positive, and D is 1. When the power is sent from the main grid to the load through the distribution line, the power direction is considered to be negative, and D is -1. When the frequency drop amplitude sets the threshold fz, the line cutting operation is not performed when the power direction is judged to be positive. When the frequency drop amplitude sets the threshold fz, when the set threshold fz is reached, the frequency change rate is lower than dfz1 / dt, and the power direction is negative, the line is cut with a delay of T. When the frequency change rate is lower than dfz2 / dt and the power direction is negative, dfz1 / dt and dfz2 / dt are both negative values, and |dfz1 / dt|<|dfz2 / dt|, the line is directly cut without delay, which can promote the frequency recovery after system failure more quickly.

[0039] See also Figure 2 , which shows a structural block diagram of a low-frequency load reduction system for distributed new energy distribution lines considering power direction in the present application.

[0040] like Figure 2 As shown, a low-frequency load reduction system 200 for distributed new energy distribution lines includes an acquisition module 210, a first judgment module 220, a second judgment module 230, a third judgment module 240 and a removal module 250.

[0041] Among them, the acquisition module 210 is configured to obtain the frequency of the grid side of the distribution line, the frequency change rate of the grid side of the distribution line and the power direction of the distribution line; the first judgment module 220 is configured to judge whether the frequency of the grid side of the distribution line is lower than the set frequency threshold; the second judgment module 230 is configured to judge whether the power direction of the distribution line is positive if the frequency of the grid side of the distribution line is not lower than the set frequency threshold; the third judgment module 240 is configured to judge whether the frequency change rate of the grid side of the distribution line is within the preset threshold range if it is not positive; the cutting module 250 is configured to cut off the distribution line after a delay of T time if the frequency change rate of the grid side of the distribution line is within the preset threshold range.

[0042] It should be understood that Figure 2 Modules and references documented in Figure 1 Therefore, the operations and features described above for the method and the corresponding technical effects are also applicable to Figure 2 The modules in it will not be described in detail here.

[0043] In some other embodiments, the embodiments of the present invention further provide a computer-readable storage medium having a computer program stored thereon, and when the program instructions are executed by a processor, the processor is caused to execute the low-frequency load reduction method for a distribution line containing distributed new energy considering power direction in any of the above method embodiments;

[0044] As an implementation mode, the computer-readable storage medium of the present invention stores computer-executable instructions, and the computer-executable instructions are configured as follows:

[0045] Obtain the frequency on the grid side of the distribution line, the frequency change rate on the grid side of the distribution line, and the power direction of the distribution line;

[0046] Determining whether the frequency on the grid side of the distribution line is lower than a set frequency threshold;

[0047] If the frequency on the grid side of the distribution line is lower than the set frequency threshold, determining whether the power direction of the distribution line is positive;

[0048] If it is not positive, determining whether the frequency change rate of the power distribution line grid side is within a preset threshold range;

[0049] If the frequency change rate on the grid side of the distribution line is within the preset threshold range, the distribution line is disconnected after a delay of T time.

[0050] The computer-readable storage medium may include a program storage area and a data storage area, wherein the program storage area may store an operating system and an application required by at least one function; the data storage area may store data created according to the use of a low-frequency load reduction system for a distributed new energy distribution line considering the power direction, etc. In addition, the computer-readable storage medium may include a high-speed random access memory, and may also include a memory, such as at least one disk storage device, a flash memory device, or other non-volatile solid-state storage device. In some embodiments, the computer-readable storage medium may optionally include a memory remotely disposed relative to the processor, and these remote memories may be connected to the low-frequency load reduction system for a distributed new energy distribution line considering the power direction via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0051] Figure 3 is a schematic diagram of the structure of an electronic device provided by an embodiment of the present invention, such as Figure 3 As shown, the device includes: a processor 310 and a memory 320. The electronic device may also include: an input device 330 and an output device 340. The processor 310, the memory 320, the input device 330 and the output device 340 may be connected via a bus or other means. Figure 3In the example, the bus connection is used. The memory 320 is the above-mentioned computer-readable storage medium. The processor 310 executes various functional applications and data processing of the server by running the non-volatile software programs, instructions and modules stored in the memory 320, that is, the method of low-frequency load reduction of distributed new energy distribution lines considering the power direction of the above-mentioned method embodiment is implemented. The input device 330 can receive input digital or character information, and generate key signal input related to user settings and function control of the low-frequency load reduction system of distributed new energy distribution lines considering the power direction. The output device 340 may include display devices such as display screens.

[0052] The electronic device can execute the method provided by the embodiment of the present invention, and has the functional modules and beneficial effects corresponding to the execution method. For technical details not described in detail in this embodiment, please refer to the method provided by the embodiment of the present invention.

[0053] As an implementation mode, the electronic device is applied to a low-frequency load reduction system of a distributed renewable energy distribution line taking into account power direction, and is used for a client, and includes: at least one processor; and a memory connected to the at least one processor in communication; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can:

[0054] Obtain the frequency on the grid side of the distribution line, the frequency change rate on the grid side of the distribution line, and the power direction of the distribution line;

[0055] Determining whether the frequency on the grid side of the distribution line is lower than a set frequency threshold;

[0056] If the frequency on the grid side of the distribution line is lower than the set frequency threshold, determining whether the power direction of the distribution line is positive;

[0057] If it is not positive, determining whether the frequency change rate of the power distribution line grid side is within a preset threshold range;

[0058] If the frequency change rate on the grid side of the distribution line is within the preset threshold range, the distribution line is disconnected after a delay of T time.

[0059] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods of each embodiment or some parts of the embodiment.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for low-frequency load reduction of a distribution line containing distributed renewable energy considering power direction, characterized in that: include: Obtain the frequency on the grid side of the distribution line, the frequency change rate on the grid side of the distribution line, and the power direction of the distribution line; Determining whether the frequency on the grid side of the distribution line is lower than a set frequency threshold; If the frequency on the grid side of the distribution line is lower than the set frequency threshold, determining whether the power direction of the distribution line is positive; If it is not positive, determining whether the frequency change rate of the power distribution line grid side is within a preset threshold range; If the frequency change rate on the grid side of the distribution line is within the preset threshold range, the distribution line is disconnected after a delay of T time.

2. A method for low-frequency load shedding of a power distribution line containing distributed renewable energy taking into account power direction according to claim 1, characterized in that: After determining whether the frequency on the grid side of the distribution line is lower than a set frequency threshold, the method further includes: If the frequency on the grid side of the distribution line is not lower than the set frequency threshold, the low-frequency load reduction will not take effect, that is, the distribution line will not be cut off.

3. According to a method for low-frequency load shedding of a power distribution line containing distributed new energy taking into account power direction according to claim 1, it is characterized in that: After determining whether the power direction of the power distribution line is positive, the method further includes: If it is positive, the low-frequency load reduction will not be activated, that is, the distribution line will not be cut off.

4. A method for reducing load on a power distribution line containing distributed renewable energy at low frequency considering power direction according to claim 1, characterized in that: After determining whether the frequency change rate of the power distribution line grid side is within a preset threshold range, the method further includes: If the frequency change rate of the power distribution line on the grid side is less than the minimum value in the preset threshold range, the power distribution line is directly cut off without delay.

5. A method for reducing load on a power distribution line containing distributed renewable energy at low frequency considering power direction according to claim 1, characterized in that: After determining whether the frequency change rate of the power distribution line grid side is within a preset threshold range, the method further includes: If the frequency change rate on the grid side of the distribution line is greater than the maximum value in the preset threshold range, the low-frequency load reduction will not be performed, that is, the distribution line will not be cut off.

6. A low-frequency load reduction system for distributed renewable energy distribution lines taking into account power direction, characterized in that: include: an acquisition module configured to acquire a frequency on a grid side of a distribution line, a frequency change rate on the grid side of the distribution line, and a power direction of the distribution line; A first judgment module is configured to judge whether the frequency of the power distribution line grid side is lower than a set frequency threshold; A second judgment module is configured to judge whether the power direction of the distribution line is positive if the frequency of the grid side of the distribution line is not lower than a set frequency threshold; A third judgment module is configured to judge whether the frequency change rate of the power distribution line grid side is within a preset threshold range if it is not positive; The cutting module is configured to cut off the distribution line after a delay of T time if the frequency change rate on the grid side of the distribution line is within a preset threshold range.

7. An electronic device, characterized in that: include: At least one processor, and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to execute the method described in any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method according to any one of claims 1 to 5 is implemented.

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