Pre-judgment method and pre-judgment system for self-healing post-load

Abstract

The invention relates to a pre-judgment method and a pre-judgment system for a self-healing load, and belongs to the technical field of load pre-judgment. According to the invention, by combining and considering the real-time fluctuation characteristic of the power grid load and the overload capacity of the power distribution network, when the power supply switching-on operation needs to be executed according to the fault of the power distribution network line, whether the power supply switching-on operation is executed or not is determined by combining the prediction result of the load after self-healing and the overload capacity of the power supply (standby power supply) corresponding to the power supply switching-on operation; specifically, after the position of a fault point of a distribution network line is judged, whether a transfer condition is met or not is determined based on the predicted redundant capacity of a load to be transferred and a standby power supply at the same time, if yes, transfer power supply closing operation is executed, and if not, the operation is not executed, so that an accurate load pre-judgment result is obtained. Therefore, load shedding operation or manual processing caused by the fact that load transfer is not executed within the overload capacity of the standby power supply can be effectively avoided.

Description

Technical Field

[0001] The present invention relates to a method and a system for predicting the post-healing load, belonging to the technical field of load prediction. Background Art

[0002] With the further development of power grid construction, the requirements for power supply reliability are also further improved. When a fault occurs in the distribution system, the self-healing function of the distribution network can automatically isolate the fault area, perform switching-on for power transfer without relying on manual operation after the fault, and quickly restore the power supply to the non-fault area, thereby reducing the power outage time and scope and improving the power supply reliability.

[0003] Before the distribution network performs switching-on for power transfer after fault isolation, it is necessary to predict the load. When predicting the load, only the total load of the current line to be transferred (also known as the load to be transferred) is obtained based on the current load data of the power grid. If the load prediction result shows that the backup power supply is not sufficient to bear the total load of the current line to be transferred, that is, the redundant capacity of the backup power supply is less than the load to be transferred, it is considered that the load prediction result does not meet the requirements for power transfer, and load shedding operations may be performed or transferred to manual processing. Load shedding operations will affect user power consumption, and manual processing will increase the self-healing processing time, both of which are far from the ideal effect.

[0004] Considering the overload capacity of the distribution network, in the power grid operation regulations, the distribution network can withstand a certain degree of overload within the specified time limit of overload. However, the load prediction result used to judge whether the requirements for power transfer are met is only obtained based on the current load data of the power grid. There is a situation where the current load prediction result does not meet the requirements for power transfer, but the load prediction result after a short time meets the requirements for power transfer, resulting in the inability to execute the switching-on for power transfer in a timely manner, too long self-healing processing time or affecting user power consumption.

[0005] In summary, the load prediction result obtained based on the current load data can only reflect whether the backup power supply can bear the total load of the current line to be transferred, and cannot combine the characteristics of the real-time fluctuation of the power grid load to obtain a more accurate load prediction result. Summary of the Invention

[0006] The purpose of the present invention is to provide a method and a system for predicting the post-healing load to solve the problem of inaccurate existing load prediction results.

[0007] To achieve the above purpose, the solution of the present invention includes: A method for predicting the post-healing load of the present invention includes the following steps: After determining the location of the fault point on the distribution network line, based on the predicted load to be transferred and the redundant capacity of the backup power supply at the same time, determine whether the power transfer conditions are met. If they are met, perform the switching-on operation for power transfer; otherwise, do not perform this operation; The transfer power supply condition is: after this transfer power supply, it exceeds the redundant capacity of the standby power supply but does not exceed the maximum overload of the standby power supply, and the overload operation of the standby power supply ends within the specified time.

[0008] Furthermore, the load to be transferred is predicted by averaging the loads at the same time as the fault occurrence time in the previous n days before the interval downstream of the fault point; n≥10.

[0009] Furthermore, the redundant capacity of the standby power supply is obtained by subtracting the predicted load of the standby power supply from the rated capacity of the standby power supply. The predicted load is predicted by averaging the loads at the same time as the fault occurrence time in the previous n days of the standby power supply; n≥10.

[0010] Furthermore, it also includes the following steps: After determining the position of the fault point on the distribution network line, if the current load meets the transfer power supply requirements, then perform the transfer power supply closing operation.

[0011] Furthermore, the priority of the current load meeting the transfer power supply requirements is higher than the priority of the load to be transferred meeting the transfer power supply conditions.

[0012] Furthermore, the load data in the previous n days is recorded once every set period, and the load data corresponding to the set period is used as the load of that period.

[0013] Furthermore, the value range of the set period is 5 minutes to 25 minutes.

[0014] A load pre-judgment system for after self-healing of the present invention includes a processor, and the processor is used to execute a computer program to implement the steps of the load pre-judgment method for after self-healing as described above.

[0015] Advantages of the present invention: The present invention is a pioneering invention, which provides a load pre-judgment method for after self-healing. By considering the characteristics of the real-time fluctuation of the power grid load and the overload capacity of the distribution network, when a transfer power supply closing operation needs to be performed due to a fault on the distribution network line, it can be determined whether to perform this transfer power supply operation by combining the prediction result of the load after self-healing and the overload capacity of the power supply (standby power supply) corresponding to the transfer power supply operation. Specifically, after determining the position of the fault point on the distribution network line, it is determined whether the transfer power supply conditions are met based on the predicted load to be transferred and the redundant capacity of the standby power supply at the same time. If the conditions are met, the transfer power supply closing operation is performed; otherwise, the operation is not performed, so as to obtain an accurate load pre-judgment result, thereby effectively avoiding not performing the transfer power supply within the overload capacity of the standby power supply, resulting in load shedding operations or manual processing. Among them, the transfer power supply condition is: after this transfer power supply, it exceeds the redundant capacity of the standby power supply but does not exceed the maximum overload of the standby power supply, and the overload operation of the standby power supply ends within the specified time. Description of the Drawings

[0016] Figure 1 It is a schematic diagram of the open-loop operation of a dual-power line in a distribution network system; Figure 2 It is a schematic diagram of the daily load fluctuation. Specific implementation manner

[0017] To solve the problems in the background technology, the present invention combines the characteristics of the real-time fluctuation of the power grid load and the overload capacity of the distribution network, and determines whether to execute the transfer switch closing operation by predicting the load to be transferred and the allowable overload range and allowable overload operation time of the standby power supply within the specified range, so as to effectively avoid not executing the transfer within the overload capacity of the standby power supply, resulting in load shedding operations or manual processing.

[0018] To facilitate the understanding of this solution, the background of this solution will be introduced as necessary, as follows: For a distribution network line with self-healing function, it should have at least two power sources. Each power source supplies power to a section of the distribution network line respectively, and the two adjacent power sources are connected by a tie switch. During normal operation, the tie switch is in the open state. The two adjacent power sources are dual-power sources that are backup power sources for each other. When a fault occurs in the system line and the fault isolation is completed, the non-faulty part of the line downstream of the fault point needs to be powered by the standby power source through transfer switch closing.

[0019] To make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments.

[0020] An embodiment of a method for predicting the load after self-healing: A method for predicting the load after self-healing includes the following steps: After determining the position of the fault point on the distribution network line, based on the predicted load to be transferred at the same time and the redundant capacity of the standby power source, it is determined whether the transfer condition is met. If it is met, the transfer switch closing operation is executed; otherwise, the operation is not executed; The transfer condition is: after this transfer power supply, it exceeds the redundant capacity of the standby power source but does not exceed the maximum overload of the standby power source, that is, after this transfer power supply, it does not exceed the allowable range of the standby power source overload, not overloading below and not exceeding the maximum overload above; and the overload operation of the standby power source ends within the specified time, that is, the load borne by the standby power source is lower than the overload limit within the specified time of overload, which can also be understood as the overload operation time is within the specified range of the overload operation time.

[0021] This solution is proposed based on the situation that under overload of the current load, the transfer operation is not executed. Considering the characteristics of the real-time fluctuation of the power grid load and the overload capacity of the distribution network, when a fault occurs in the distribution network line and a transfer power supply closing operation needs to be executed, the predicted result of the load after self-healing and the overload capacity of the power supply corresponding to the transfer power supply operation (standby power supply) are combined to obtain the load prediction result of this time, and it is decided whether to execute the transfer power supply operation of this time, so as to effectively avoid not executing the transfer within the overload capacity of the standby power supply, resulting in load shedding operations or manual handling.

[0022] Among them, the specified time is determined according to factors such as the degree of overload. The greater the degree of overload, the shorter the specified time, and the specified time varies in different regions and can be specifically determined according to the actual situation.

[0023] Specifically, the load to be transferred is predicted by averaging the loads at the same time as the fault occurrence time in the n days before the interval downstream of the fault point; n≥10. Of course, the load to be transferred can also be predicted by other methods, such as prediction models.

[0024] Specifically, the redundant capacity of the standby power supply is obtained by subtracting the predicted load of the standby power supply from the rated capacity of the standby power supply. The predicted load is predicted by averaging the loads at the same time as the fault occurrence time in the n days before this standby power supply; n≥10. Of course, the predicted load can also be predicted by other methods, such as prediction models.

[0025] As another implementation method, the method for predicting the load after self-healing includes the following steps: After determining the position of the fault point of the distribution network line, if the current load meets the transfer requirements and one of the conditions for determining that the transfer conditions are met based on the predicted load to be transferred and the redundant capacity of the standby power supply at the same time is met, the transfer power supply closing operation is executed; otherwise, this operation is not executed.

[0026] Among them, the transfer requirements are: the load to be transferred is less than the redundant capacity of the standby power supply; the transfer conditions are: after this transfer power supply, it exceeds the redundant capacity of the standby power supply but does not exceed the maximum overload of this standby power supply, and the overload operation of this standby power supply ends at the specified time.

[0027] As another implementation method, the method for predicting the load after self-healing includes the following steps: After determining the position of the fault point of the distribution network line, if the current load meets the transfer requirements, the transfer power supply closing operation is executed; otherwise, it is determined whether the transfer conditions are met based on the predicted load to be transferred and the redundant capacity of the standby power supply at the same time. If the conditions are met, the transfer power supply closing operation is executed; otherwise, this operation is not executed. The power transfer condition is as follows: after this power transfer, the redundant capacity exceeds the standby power supply but does not exceed the maximum overload of the standby power supply, and the overload operation of the standby power supply ends within the specified time.

[0028] In this scheme, the priority of the current load meeting the power transfer requirement is higher than that of the load to be transferred meeting the power transfer condition.

[0029] Considering that the power transfer requirement has little impact on the distribution network, while the power transfer condition requires the distribution network to bear controllable risks, the power transfer operation that meets the power transfer requirement is preferentially executed. Only when the power transfer requirement is not met, the power transfer condition is considered.

[0030] Specifically, considering the pressure of data processing and transmission, the load data within the previous n days is recorded once every set period, and the load data corresponding to the set period is used as the load for that period.

[0031] Specifically, the value range of the set period is from 5 minutes to 25 minutes, and it can also be selected according to actual needs. This scheme preferably selects 15 minutes.

[0032] Specifically, the method for predicting the load after self-healing includes the following steps: To ensure that the standby power supply capacity is sufficient to bear the power supply demand of the fault-free part of the line, the following load prediction needs to be carried out before the power transfer closing: when the load prediction result obtained from the current power grid load data meets the power transfer requirement, the power transfer closing operation can be executed; if the load prediction result obtained from the current power grid load data does not meet the power transfer requirement, the next dynamic load prediction operation is carried out.

[0033] The dynamic load prediction combines the daily load fluctuation of the line to predict the load change after a period of time (T time). If the load prediction result meets the power transfer requirement after T time, the power transfer closing operation can be executed in advance.

[0034] Considering that in the power grid operation regulations, the system can withstand a certain degree of overload in a short time. Therefore, if both conditions are met: ① the load after power transfer is not greater than the overload requirement; ② the system load drops below the overload limit within the specified time T (T time); it is considered that the dynamic load prediction meets the power transfer requirement, and the power transfer closing operation can be executed in advance.

[0035] The data used for dynamic load prediction comes from the average load data at the same time of each day in the recent n days, and based on this, the system load change after T time is judged.

[0036] In the distribution network system, the load pressure is different at different times of the day and generally shows periodic fluctuations. According to the load data trend in the previous n days, the expected trend of the load in a period of time thereafter can be basically judged.

[0037] When the system is running normally, each distribution terminal records the load power values at different time periods of the day in real time. When recording new values every day thereafter, the average is taken with the previous records.

[0038] After the recording time exceeds n days, the data is continuously updated in a rolling recording form.

[0039] The load power value is recorded every 15 minutes, starting from the whole hour of each day, for a total of 96 sets of data.

[0040] When the fault is isolated, the distribution terminals in the non-faulty area send the load data recorded by this device to the distribution terminal for standby power management, and the distribution terminal for standby power management performs the calculation.

[0041] More specifically, the method for predicting the load after self-healing includes the following steps: 1. Load data calculation As Figure 1 shown, a standard ring main unit grid framework is divided into the following elements: Power supplies: G1, G2; Incoming and outgoing line intervals: 101, 102, 201, 202, 301, 302, 401, 402, 501, 502, 601, 602; Sectionalizing switch: 302; Feeder intervals: 111, 112, 211, 212, 311, 312, 411, 412, 511, 512, 611, 612.

[0042] For the distribution line (distribution network line), the real power consumption load is in the feeder interval. Therefore, the load data calculation is carried out in units of the feeder interval.

[0043] Define the power set of a certain feeder interval at every set time interval in a day as s(i,j) = (s(i,1), s(i,2), …, s(i,96)), where i is the corresponding number of this feeder interval and j is the number of power values recorded by this feeder interval every day.

[0044] Among them, when the set time interval is 15 minutes, the number of power values recorded by this feeder interval every day is calculated as follows: j = (24×60) / 15 = 96. In the formula, 24×60 refers to a total of 24×60 minutes (min) in a day, and 15 refers to the recording period of 15 minutes in a day; for example, s(3,9) is the power value of the 3rd feeder interval at the ninth 15-minute interval, that is, at 2:15 on the same day.

[0045] To exclude the impact of abnormal load fluctuations at a single moment, the power data of the same feeder interval at a certain recording moment on a certain day is the average value of the power data of the same feeder interval at the same recording moment in the previous n days, that is, s(i, j) / n, where i and j for taking the average are the same; the average number of days n can vary according to the regional load characteristics or actual application scenarios, but should not be less than 10.

[0046] 2. Load data update Based on the above regulations, the specific calculation method for each element in s(i, j) is as follows: The power data of the same feeder interval at the same recording moment in the previous n days is the value of s(i, j) in the most recent n days, arranged as shown in Table 1 below: Table 1 Number of days The current day The previous day Two days ago …… The (n - 1)th day ago s(i, j) 45 47 65 …… 41 s(i, j) / n is the average value of the s(i, j) data within n days.

[0047] When the time comes to the next day, the data of "the previous n - 2 days" replaces the data of "the previous n - 1 days"; the data of "the previous n - 3 days" replaces the data of "the previous n - 2 days", and so on, until the data of "the current day" replaces the data of "the previous 1 day"; finally, the newly calculated corresponding data is written into the data of "the current day", that is, the data of "the next day" replaces the data of "the current day", and then the value of s(i, j) / n is calculated to complete the data update.

[0048] 3. Load prediction When a fault occurs in the distribution network, the feeder intervals downstream of the fault point send the s(i, j) / n data to the distribution terminal for standby power management, and the distribution terminal for standby power management calculates the total load number Sum(i, j) of the current line to be transferred.

[0049] When the load prediction result shows that the standby power is insufficient to bear the total load of the current line to be transferred, according to the changing trend of the Sum(i, j) data, calculate the total load number of the line to be transferred at each time point starting from the current time within T time, and determine whether there is a time point within T time starting from the current time when the total load number of the line to be transferred can be borne by the standby power. If so, it is considered that the dynamic load prediction result within T time meets the transfer requirements.

[0050] When the load prediction result obtained based on the current load data does not meet the transfer requirements, this scheme can also perform the following steps: when the load prediction result obtained based on the load data in a subsequent period of time meets the transfer requirements, execute the transfer closing. It can not only transfer power in a timely manner, quickly restore power supply, and not affect user power consumption when the load prediction result obtained based on the current load data meets the transfer requirements; but also transfer power in a timely manner, quickly restore power supply, and not affect user power consumption within the load range that the system can bear in a short time.

[0051] This solution takes into account the characteristics of the real-time fluctuations of the grid load and the overload capacity of the distribution network, conducts dynamic load forecasting based on the historical load data within the system, can accurately predict the load, and restore power supply within the allowable overload range specified in the regulations, so as to improve the existing problems, help the power system managers quickly restore power supply, reasonably arrange the output of the generating units, and adjust the power transmission plan to maintain the balance and stable operation of the power system. Among them, the daily load fluctuations of a certain power grid are as Figure 2 shown.

[0052] An embodiment of a system for predicting the load after self-healing: A system for predicting the load after self-healing includes a processor, which is used to execute a computer program to implement the steps of a method for predicting the load after self-healing. Among them, a method for predicting the load after self-healing has been described in detail in an embodiment of a method for predicting the load after self-healing, and will not be elaborated here.

Claims

1. A method for predicting self-healing afterload, characterized in that, It includes the following steps: After determining the location of the fault point on the distribution network line, based on the predicted load to be transferred and the redundant capacity of the standby power supply at the same time, it is determined whether the transfer condition is met. If it is met, the transfer power supply closing operation is executed; otherwise, this operation is not executed. The transfer condition is that after this power transfer, it exceeds the redundant capacity of the standby power supply but does not exceed the maximum overload of the standby power supply, and the overload operation of the standby power supply ends within the specified time.

2. The method for predicting the self-healing post-load according to claim 1, wherein The load to be transferred is predicted by averaging the loads at the same time as the fault time in the n days before the interval downstream of the fault point; n≥10.

3. The prediction method for self-healing afterload according to claim 1, characterized in that, The redundant capacity of the standby power supply is obtained by subtracting the predicted load of the standby power supply from the rated capacity of the standby power supply. The predicted load is predicted by averaging the loads at the same time as the fault time in the n days before the standby power supply; n≥10.

4. The method for predicting self-healing afterload according to claim 1, characterized in that, It also includes the following steps: After determining the location of the fault point on the distribution network line, if the current load meets the transfer requirements, the transfer power supply closing operation is executed.

5. The prediction method for self-healing afterload according to claim 4, wherein The priority of the current load meeting the transfer requirements is higher than the priority of the load to be transferred meeting the transfer conditions.

6. The method for predicting self-healing afterload according to claim 2 or 3, wherein The load data within the previous n days is recorded once every set period, and the load data corresponding to the set period is used as the load for that period.

7. The prediction method for self-healing post-load according to claim 6, characterized in that, The value range of the set period is from 5 minutes to 25 minutes.

8. A prediction system for post-healing afterload, comprising a processor, characterized in that, The processor is used to execute a computer program to implement the steps of the method for predicting the load after self-healing according to any one of claims 1 to 7.

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