A low-frequency low-voltage load shedding control method and system based on information collection of cuttable objects

Abstract

The application discloses a low-frequency low-voltage load shedding control method and system based on information collection of cuttable objects, and the method comprises the following steps: when low frequency / low voltage occurs in a power grid, load property lines are selected and cut according to a selected cutting mode; when the selected cutting is performed according to a preset export matrix constant value mode, the load property lines are selected and cut according to the matrix constant value; when the selected cutting is performed according to a required load cutting ratio mode, the required load cutting amount is obtained according to the required load cutting ratio and total load power in the current round, and the load property lines are selected and cut according to load priorities; wherein, the property of each load line is determined to be a load type or a power supply type according to the active power of the load line. Through collection of power information of cuttable objects, the load / power supply property is accurately identified, only load lines are cut off when low frequency / low voltage acts, and power supply lines are not cut off, so that the system frequency and voltage are further deteriorated due to mis-cutting of power supply during low frequency / low voltage of the power grid, and the reliability and accuracy of the low-frequency low-voltage control are improved.

Description

Technical Field

[0001] This invention belongs to the field of power system automation, and specifically relates to a low-frequency, low-voltage load shedding control method and system based on the acquisition of information about shedding objects. Background Technology

[0002] With the continuous advancement of new power system construction and the large-scale integration of new energy sources, the characteristics of the power grid are becoming increasingly complex, making it difficult to configure traditional second-line security control strategies and increasing the risk of mismatch. Against this backdrop of security issues, low-frequency, low-voltage load shedding, as the third line of defense for the power system, is a crucial means to ensure that the system does not experience frequency collapse and maintains stable operation.

[0003] Lines awaiting disconnection that carry a large amount of distributed renewable energy exhibit a "tidal" characteristic in terms of active power direction, highly correlated with solar and wind power over time. That is, when power generation exceeds consumption, the line behaves as a power source; when consumption exceeds power generation, the line behaves as a load source. Traditional low-frequency, low-voltage load shedding methods cannot accurately identify active lines, leading to erroneous power disconnection and increased system risks.

[0004] Furthermore, traditional low-frequency, low-voltage load shedding strategies cut off lines according to a fixed output matrix in each round of operation. This process is time-consuming to set and difficult to adjust, and cannot adapt to system and load changes in real time. During periods of high renewable energy generation, if the distributed renewable energy output connected to the line to be cut off balances a significant portion of the load, low-frequency / low-voltage operations may cause under-cutting when cutting off that line. Moreover, since the low-frequency operation output matrix is ​​set according to the maximum load predicted by the central dispatch, when the overall network load is at a low level, low-frequency operations may cause over-cutting, resulting in additional load loss.

[0005] Therefore, there is an urgent need for a low-frequency, low-voltage load shedding control scheme that can accurately identify the characteristics of the load / power supply that can be sheared. Summary of the Invention

[0006] The purpose of this invention is to provide a low-frequency, low-voltage load shedding control method and system based on the acquisition of switchable object information. By acquiring the power information of switchable objects, the load / power supply characteristics can be accurately identified. During low-frequency / low-voltage operations, only the load line is disconnected, without disconnecting the power supply line. This avoids the further deterioration of the system frequency and voltage caused by erroneous power disconnection when the power grid experiences low frequency or low voltage, thereby improving the reliability and accuracy of low-frequency, low-voltage control.

[0007] To achieve the above objectives, the solution of the present invention is:

[0008] A low-frequency, low-voltage load shedding control method based on the acquisition of switchable object information is disclosed. When low-frequency / low-voltage conditions occur in the power grid, load-type lines are selectively shedding according to their shedding modes. The shedding modes include a preset output matrix setting mode and a load shedding ratio mode. When selecting loads according to the preset output matrix setting mode, load-type lines are selected according to the matrix setting. When selecting loads according to the load shedding ratio mode, the load to be shedding is obtained based on the load shedding ratio and total load power in this round, and load-type lines are selected according to load priority. The nature of each load line is determined as either a load or a power source based on its active power.

[0009] Among these, the nature of each load line is determined as either a load or a power source based on its active power, including:

[0010] Obtain information about each load line within the station through communication or direct cable procurement methods. active power ;

[0011] Based on the active power values ​​of each load line, if Then it is considered that the load line If it is classified as a load, then it is considered a load line. It is a power supply type.

[0012] When obtaining the active power of each load line, if the active power of a certain load line cannot be obtained, the active power of that load line is set to 0 and it is treated as a load.

[0013] This includes obtaining the active power of each load line within the station through communication or direct cable acquisition methods, including...

[0014] The active power of each load line in the substation can be obtained from the line measurement and control department within the substation through station control layer communication or object-oriented substation event communication; or, the active power of each load line in the substation can be calculated by directly sampling the line voltage and current through cables.

[0015] When selecting and switching according to the preset output matrix setting mode, the selected load-type lines satisfy the following conditions:

[0016]

[0017] In the formula, Indicates the first The exit matrix is ​​a fixed value for each action round; this formula represents the bit of the exit matrix. The value is 1, meaning the line is 1. It was integrated into the export matrix.

[0018] When selecting load shedding according to the required load ratio mode, the required load shedding amount is obtained based on the required load shedding ratio and the total load power for this round.

[0019]

[0020] In the formula, This indicates the amount of load to be cut in the j-th action round; Indicates the first The load ratio needs to be cut in each action cycle; This indicates the total load power.

[0021] The method for obtaining the total load power is as follows:

[0022] Obtain information about each load line within the station through communication or direct cable procurement methods. active power ;

[0023] Calculate using the following formula,

[0024]

[0025] In the formula, This indicates the total load power of the entire station; Indicates the load line The power; This indicates the total number of load lines.

[0026] Among them, selecting and cutting load-type lines according to load priority includes prioritizing the cutting of non-critical load-type lines.

[0027] A low-frequency, low-voltage load shedding control system based on the acquisition of shearable object information includes,

[0028] The low-frequency / low-voltage discrimination module is configured to determine whether the power grid is experiencing low frequency / low voltage.

[0029] The load power processing module is configured to determine whether each load line is a load or a power source based on its active power.

[0030] The load-switching module based on the output matrix settings is configured to select and switch load-type lines according to preset output matrix settings; and,

[0031] The load shedding module is configured to calculate the amount of load to be shedding based on the required load shedding ratio and total load power in this round, and select the load type lines to be shedding according to load priority.

[0032] After adopting the above scheme, the present invention collects information on switchable objects and identifies their status through communication or direct cable acquisition. Two control modes are set for low-frequency and low-voltage applications: matrix control and load-proportional control. In matrix control mode, the power direction of each switchable object in the preset matrix is ​​determined, and the power outlet of the power object is blocked. In load-proportional control mode, the power information of all objects is accumulated, the total load power of the station is calculated, a cutoff ratio setting is set for each cycle, the required load cutoff amount for each cycle is dynamically calculated, and load objects are selected for cutoff according to priority among the switchable load objects.

[0033] This invention enables accurate identification of the load and power supply attributes of the object being cut off, avoiding further deterioration of system frequency and voltage caused by erroneous power supply cutting when the power grid experiences low frequency and low voltage, and improving the reliability and accuracy of low frequency and low voltage control. Attached Figure Description

[0034] Figure 1 This is a flowchart illustrating the present invention;

[0035] Figure 2 This is a device architecture diagram provided in Embodiment 1 of the present invention (obtaining load line power via communication).

[0036] Figure 3 This is a device architecture diagram provided in Embodiment 1 of the present invention (obtaining load line power through direct cable sampling). Detailed Implementation

[0037] The technical solution and beneficial effects of the present invention will be described in detail below with reference to the accompanying drawings.

[0038] like Figure 1 As shown, Embodiment 1 of the present invention provides a low-frequency, low-voltage load shedding control method based on the acquisition of shearable object information, comprising the following steps:

[0039] Step 1: Obtain information for each load line within the station via communication or direct cable procurement. active power .

[0040] The load line power can be obtained from the line measurement and control department within the station by the low-frequency, low-voltage load shedding device through station control layer communication or through Generic Object Oriented Substation Event (GOOSE) communication. The device architecture for obtaining the load line power through communication is as follows: Figure 2 As shown; alternatively, the voltage and current of the line can be directly obtained by a low-frequency, low-voltage load shedding device through cable, and the results can be calculated. The device architecture for obtaining the load line power through direct cable acquisition is as follows. Figure 3 As shown.

[0041] Step 2, determine the load line power value, if P i If the value is greater than or equal to 0, then line i is considered a load; otherwise, line i is considered a power source.

[0042] In a preferred but non-limiting embodiment, in step 2, when the low-frequency low-voltage load shedding device is unable to obtain the active power of certain load lines due to communication interruption, invalid data quality, or other reasons, the power of these lines should be set to 0 and they should be regarded as load lines.

[0043] Step 3, calculate the active power P of all lines. i The total load power P is calculated by summing the results. xw .

[0044] In a preferred but non-limiting embodiment, in step 3, the total load power P of the entire station xw Calculate using the following formula.

[0045] (1)

[0046] In the formula:

[0047] P xw This indicates the total load power of the entire station;

[0048] P i This represents the power of line i. For load lines, the power is a positive number or 0, and for power supply lines, the power is a negative number.

[0049] n represents the total number of lines.

[0050] Step 4: If the power grid experiences low frequency / low voltage and the switching is performed according to the preset output matrix setting mode, then the load characteristics of the line are selected and switched according to the matrix setting.

[0051] In a preferred but non-limiting embodiment, in step 4, if the device performs selection and switching according to the preset output matrix setting mode, then line i must simultaneously meet the following two conditions to be selected and switched.

[0052] (2)

[0053] (3)

[0054] In the formula:

[0055] TM j This represents the constant value of the exit matrix for the j-th action round;

[0056] P i This represents the power of line i. For load lines, the power is a positive number or 0, and for power supply lines, the power is a negative number.

[0057] Formula (2) indicates that bit i in the exit matrix is ​​1, meaning that line i is tuned into the exit matrix.

[0058] Step 5: If the power grid experiences low frequency / low voltage, and load shedding is performed according to the required load shedding ratio mode, then the required load shedding ratio k for this round is used as the determining factor. j and total load power P xw Calculate the required load shedding P xq_j And select the load type line according to load priority, and give priority to cutting non-critical loads.

[0059] In a preferred but non-limiting embodiment, in step 5, if the device selects and cuts loads according to the required load ratio mode, then the required load P in the j-th operation round... xq_j Calculate using the following formula.

[0060] (4)

[0061] In the formula:

[0062] P xq_j This indicates the amount of load to be cut in the j-th action round;

[0063] k j This indicates the percentage of load that needs to be cut in the j-th action round;

[0064] P xw This indicates the total load power of the entire station.

[0065] In a non-limiting example, such as when a substation experiences low frequency / low voltage, the present invention achieves accurate identification of the load and power supply attributes of the object being cut during the operation of the low frequency / low voltage load shedding device. This avoids the further deterioration of the system frequency and voltage caused by erroneous power supply cutting when the power grid experiences low frequency / low voltage, thereby improving the reliability and accuracy of low frequency / low voltage control.

[0066] To more clearly illustrate the technical solution and beneficial effects of the present invention, a non-limiting example is given below.

[0067] This invention provides a low-frequency, low-voltage load shedding control method and system based on the acquisition of switchable object information. Assume a 110kV substation contains eight 10kV lines (Line 1, Line 2...Line 8), each line supporting distributed photovoltaic (PV) power of varying capacities. Most of the time, the lines are in a load-bearing state; however, during periods of high PV power generation, some lines become power sources. A low-frequency, low-voltage load shedding device is installed within the substation for low-frequency, low-voltage control, and all eight lines are included in the control resource scope.

[0068] I. Assume that during a period of high photovoltaic power generation, the power values ​​of each load line are as shown in the table below.

[0069] Table 1

[0070] power 6 MW -5 MW -3 MW 6 MW 0 MW 9 MW -2 MW 9 MW

[0071] First, the device determines the power direction of each line, and then determines its load / power supply characteristics. The determination results are shown in the table below.

[0072] Table 2

[0073] nature load power supply power supply load load load power supply load

[0074] When the device detects a low frequency in the power grid, it initiates the first low-frequency operation. Assuming the device performs load switching according to the output matrix mode, the output matrix setting for the first low-frequency operation is 0X000F.

[0075] If the device selects and switches according to the traditional mode, without considering the direction of line power, it will select and switch lines 1, 2, 3, and 4, with a total actual load being...

[0076] 6 – 5 – 3 + 6 = 4 MW

[0077] If the device determines the direction of power in the line and does not cut off the power supply line, then only lines 1 and 4 will be cut off, and the total actual load cut will be...

[0078] 6 + 6 = 12 MW

[0079] As can be seen from the above comparison, when new energy sources generate a large amount of power, if the distributed new energy output connected to the line to be cut off balances a large load, the power line will be accidentally cut off when the low frequency / low voltage is controlled in the traditional mode, resulting in the overall system under-cutting. After adopting the solution of the present invention, only the load line is cut off, and the power line is not cut off, thus ensuring the effectiveness of low frequency / low voltage control.

[0080] II. Assume the region requires that when a low-frequency event occurs in the power grid, 20% of the total grid load will be cut off in the first round of low-frequency events. The dispatching department will adjust the load according to the maximum load predicted by the unified dispatching department. The maximum load of this substation is shown in the table below.

[0081] Table 3

[0082] power 7 MW 6 MW 3 MW 8 MW 8 MW 10 MW 7 MW 11 MW

[0083] Total load power of the station for

[0084]

[0085] Low-frequency load shedding required in the first round for

[0086]

[0087] Assuming that the cutoff priority of each load line is consistent with the line number, according to the overcut principle, the first round of low frequency should select and cut line 1 and line 2. According to the traditional output matrix mode, the output matrix of the first round of low frequency should be set to 0X0003.

[0088] During actual operation, the power values ​​of each load line during a period of low load level are shown in the table below.

[0089] Table 4

[0090] power 4 MW 3 MW 1 MW 5 MW -1 MW 3 MW 0 MW 4 MW

[0091] Total load power of the station for

[0092]

[0093] When the device detects a low frequency in the power grid, it initiates the first low-frequency operation. Assuming the device performs selective switching according to the fixed output matrix mode, disconnecting line 1 and line 2, the actual disconnected load is... for

[0094]

[0095] Assuming the device selects loads according to the required load shedding ratio, and the first round of required load shedding ratio for low-frequency loads is 20%, then the first round of required load shedding for low-frequency loads is... for

[0096]

[0097] At this point, simply disconnecting line 1 is sufficient to meet the 20% load shedding requirement, and the actual load shedding amount is... With a capacity of 4MW, it cuts one less load line compared to the fixed outlet matrix mode.

[0098] As can be seen from the above comparison, by using the solution of the present invention to collect information on slicable objects and adopting a proportional control method, the problem of over-slicing when the load level is low can be effectively prevented.

[0099] Embodiment 2 of the present invention provides a low-frequency, low-voltage load shedding control system based on the acquisition of shearable object information, which operates the low-frequency, low-voltage control method described above, including:

[0100] The low-frequency / low-voltage discrimination module is configured to determine whether the power grid is experiencing low frequency / low voltage.

[0101] The load power processing module is configured to determine whether each load line is a load or a power source based on its active power.

[0102] The load-switching module based on the output matrix settings is configured to select and switch load-type lines according to preset output matrix settings; and,

[0103] The load shedding module is configured to calculate the amount of load to be shedding based on the required load shedding ratio and total load power in this round, and select the load type lines to be shedding according to load priority.

[0104] 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.

[0105] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0106] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A low-frequency, low-voltage load shedding control method based on the acquisition of shearable object information, characterized in that: When the power grid experiences low frequency / low voltage, load-type lines are selectively switched according to their switching modes. These modes include a preset output matrix setting mode and a load-switching ratio mode. When switching is performed according to the preset output matrix setting mode, load-type lines are selected and switched according to the matrix setting. When switching is performed according to the load-switching ratio mode, the load to be switched is obtained based on the load-switching ratio and total load power in this round, and load-type lines are selected and switched according to load priority. Among them, the nature of each load line is determined as either a load or a power source based on its active power.

2. The method as described in claim 1, characterized in that: The nature of each load line is determined by its active power, classifying it as either a load or a power source. Obtain information about each load line within the station through communication or direct cable procurement methods. active power ; Based on the active power values ​​of each load line, if Then it is considered that the load line If it is classified as a load, then it is considered a load line. It is a power supply type.

3. The method as described in claim 2, characterized in that: When obtaining the active power of each load line, if the active power of a certain load line cannot be obtained, the active power of that load line is set to 0 and it is treated as a load.

4. The method as described in claim 2, characterized in that: The active power of each load line within the station is obtained through communication or direct cable acquisition. include, The active power of each load line in the station is obtained from the line measurement and control department in the station through station control layer communication or object-oriented substation event communication. Alternatively, the voltage and current of the cable line can be directly sampled, and the active power of each load line in the station can be calculated.

5. The method as described in claim 1, characterized in that: When selecting and switching according to the preset output matrix setting mode, the selected load-type lines satisfy the following conditions: ， In the formula, Indicates the first The exit matrix is ​​a fixed value for each action round; this formula represents the bit of the exit matrix. The value is 1, meaning the line is 1. It was integrated into the export matrix.

6. The method as described in claim 1, characterized in that: When selecting load shedding according to the required load ratio mode, the required load shedding amount is obtained based on the required load shedding ratio and the total load power for this round. ， In the formula, This indicates the amount of load to be cut in the j-th action round; Indicates the first The load ratio needs to be cut in each action cycle; This indicates the total load power.

7. The method as described in claim 6, characterized in that: The method for obtaining total load power is as follows: Obtain information about each load line within the station through communication or direct cable procurement methods. active power ; Calculate using the following formula, ， In the formula, This indicates the total load power of the entire station; Indicates the load line The power; This indicates the total number of load lines.

8. The method as described in claim 6, characterized in that: Selecting and cutting off lines based on load priority includes prioritizing the cutting off of lines with non-critical load characteristics.

9. A low-frequency, low-voltage load shedding control system based on the acquisition of shearable object information, characterized in that: include, The low-frequency / low-voltage discrimination module is configured to determine whether the power grid is experiencing low frequency / low voltage. The load power processing module is configured to determine whether each load line is a load or a power source based on its active power. The load-switching module based on the output matrix setting is configured to select and switch load-type lines according to the preset output matrix setting. as well as, The load shedding module is configured to calculate the amount of load to be shedding based on the required load shedding ratio and total load power in this round, and select the load type lines to be shedding according to load priority.

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