Feeder load shedding method and system considering distributed power supply

Abstract

The application provides a feeder load shedding method and system considering distributed power supply, which comprises the following steps: performing real-time iteration sorting on each feeder according to load shedding cost and load shedding effect; calculating total low-frequency load shedding amount according to a steady-state frequency setting value; detecting that the power system frequency drops to a flexible load shedding setting value, and preferentially shedding the flexible load; if the frequency rises after shedding the flexible load, stopping the feeder shedding process; if the frequency does not obviously rise or does not rise, when detecting that the power system frequency drops to a first round of low-frequency load shedding action frequency, issuing a shedding instruction; determining the load shedding position and capacity according to the frequency change rate, implementing load shedding, and shedding the feeder with the lowest total score; after completing the load shedding, detecting the frequency rise situation, ending the low-frequency load shedding when the frequency rises, and if the frequency further drops, entering the next load shedding; detecting the frequency change situation, stopping the low-frequency load shedding process when the frequency rises, entering a secondary frequency modulation stage, and adjusting the frequency back to the range required by the working frequency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of feeder load shedding, and particularly relates to a feeder load shedding method and system considering distributed power sources. BACKGROUND

[0002] The statements in this section merely provide background information related to the application and do not necessarily constitute prior art.

[0003] As the third line of defense of the power system, low-frequency load shedding is an effective method to suppress frequency drop and maintain system frequency stability. The traditional low-frequency load shedding scheme adopts a successive approximation calculation method, and according to the action frequency of each round, a pre-set load is cut off.

[0004] The main round of low-frequency load shedding relies on frequency relays and time relays. When the frequency of the power system drops to a corresponding frequency of a certain level, the system cuts off part of the load. If the system frequency rises, the load shedding step is stopped. If the system frequency continues to drop, the n+1 level low-frequency load corresponding frequency will be touched, and the system will cut off part of the load until the system frequency returns to the normal value.

[0005] As shown in Figure 1 Before the fault occurs, the system frequency is stable at the rated value f e , it is assumed that at t1, a large amount of active power shortage occurs in the system, and the system frequency sharply drops. When the frequency drops to f2, the first round of frequency relays starts, and a part of the user load is disconnected. Due to the disconnection of part of the load, the frequency will continue to drop along the curve 2-3 instead of the curve 2-4. When the frequency drops to f3, the second round of frequency relays of the low-frequency load shedding starts, and the load set in the second round is disconnected. Figure 1 In this case, after the load set in the second round is disconnected, the frequency starts to rise along the curve 3-6, and finally stabilizes at the recovery frequency f ss , which indicates that the total amount of the first two times of load shedding is approximately equal to the power shortage. If the total amount of the disconnected load after the second round of action is less than the shortage power, the frequency will continue to drop, and through the low-frequency load shedding, the system frequency will gradually approach the value of the power shortage until the system frequency stabilizes or rises, and the whole process of the low-frequency load shedding ends.

[0006] However, with the implementation of new energy policies such as "whole county photovoltaic", a large amount of distributed power sources are connected to the distribution network, which brings a series of problems to the traditional low-frequency load shedding strategy.

[0007] 1) With the connection of distributed power sources, the proportion of traditional power output decreases, the inertia decreases, and the frequency change when dealing with disturbances is more obvious;

[0008] 2) Distributed power access to the feeder, resulting in a decrease in net load, if the load is proportionally reduced, it may cause mis-cut to the distributed power and increase the round;

[0009] 3) After the access of distributed power, it may cause the reverse of part of the feeder flow. The traditional low-frequency load shedding scheme cannot distinguish this situation, resulting in the removal of these feeders, which further deteriorates the frequency.

[0010] The results of the comparison simulation before and after the access of distributed power are shown in Figure 2 After the access of distributed photovoltaic, the traditional low-frequency load shedding scheme needs to cut more rounds of load to keep the system relatively stable in frequency, and the lowest point of frequency is lower than before.

[0011] In addition, although there are existing technologies based on intelligent algorithms for cutting, such as CN113312839B_A power grid emergency auxiliary load shedding decision method and device based on reinforcement learning, CN107749620B_A power supply recovery method for distribution network containing distributed power, and the literature "A distributed power cutting method based on communication protection fusion", the above technical solutions have the following problems:

[0012] The existing technology does not closely combine distributed power, flexible load and low-frequency load shedding process. At the same time, flexible load is not used as a low-frequency load shedding frequency modulation resource. The cost of cutting flexible load is lower than that of other loads. Considering flexible load as a frequency modulation resource can reduce the cost of low-frequency load shedding. In addition, the output of distributed power cannot be measured in real time, and the existing technology cannot be predicted. SUMMARY

[0013] To overcome the above-mentioned deficiencies of the prior art, the present application provides a feeder load shedding method considering distributed power, which is based on a new feeder sorting method, retains feeders with more distributed power output, and realizes accurate cutting of feeder load. It also considers cutting a part of flexible load first to achieve better economic benefits.

[0014] To achieve the above-mentioned purpose, one or more embodiments of the present application provide the following technical solutions:

[0015] In a first aspect, a feeder load shedding method considering distributed power is disclosed, comprising:

[0016] iteratively sorting each feeder in real time according to the load shedding cost and the load shedding effect;

[0017] calculating the total amount of low-frequency load shedding according to the steady-state frequency set value;

[0018] When the power system frequency drops to the flexible load shedding set value, the flexible load is preferentially shed;

[0019] If the frequency rises after the flexible load is shed, the feeder shedding process is stopped;

[0020] If the frequency rise is not obvious or does not rise, when the power system frequency drops to the first action frequency of the low-frequency load shedding, a shedding instruction is issued;

[0021] The load shedding position and capacity are determined according to the frequency change rate, the load shedding is implemented, the feeder with the lowest total score is shed, after the load is shed, the frequency rise is detected, if the frequency rises, the low-frequency load shedding process is ended, if the frequency further drops, the next load shedding is entered;

[0022] The frequency change is detected, when the frequency rises, the low-frequency load shedding process is stopped, and the secondary frequency regulation stage is entered, and the frequency is adjusted to the range required by the working frequency.

[0023] As a further technical solution, the feeder priorities are sorted, and the specific steps are as follows:

[0024] The set indexes include: load category, load frequency characteristic and distributed power generation influence;

[0025] Each index is divided into grades according to importance, and a judgment matrix is obtained according to the grade division;

[0026] The weight of each index is calculated based on the judgment matrix;

[0027] The score of each index is multiplied by the corresponding weight, and finally the total score of each feeder is obtained, and all the feeders are sorted according to the total score of each feeder.

[0028] As a further technical solution, each index is divided into grades according to importance, including: the load category as the first grade target; the distributed power generation as the second grade target; and the load characteristic frequency as the third grade index.

[0029] As a further technical solution, the score of each index includes the load category score, the load frequency characteristic score and the distributed power generation influence score;

[0030] The load category score is the ratio of the unit power outage cost to the unit power outage cost reference value;

[0031] The load frequency characteristic score is the ratio of the product of the power of the load on the feeder and the frequency characteristic coefficient of the load on the feeder to the reference power;

[0032] The distributed power generation influence score is the ratio of the sum of the actual load power and the distributed power generation power to the net load power.

[0033] As a further technical solution, the load shedding position and capacity are determined according to the frequency change rate, the distributed power output is separated from the feeder net load power, and the load shedding is implemented.

[0034] As a further technical solution, the distributed power output is predicted through historical data, feeder net load power and environmental factors.

[0035] As a further technical solution, when the distributed power output is predicted:

[0036] A measurement sequence corresponding to the light intensity, temperature and wind intensity in the region within a period of time is obtained;

[0037] A distributed photovoltaic power generation total power sequence and a distributed wind power generation total power sequence are set;

[0038] It is assumed that there is a certain nonlinear mapping relationship between the distributed photovoltaic power generation total power and the light intensity and temperature, and there is a certain nonlinear mapping relationship between the distributed wind power generation total power and the wind intensity;

[0039] A separation prediction model for the distributed power output is established using a BP neural network, including: a prediction model for real-time output of the distributed photovoltaic power is established; and a prediction model for the distributed wind power generation is established;

[0040] The real-time output of the distributed power is predicted based on the established model.

[0041] In a second aspect, a feeder load shedding system considering distributed power is disclosed, including:

[0042] A sorting module is configured to: sort each feeder in real time according to the load shedding cost and the load shedding effect;

[0043] A load shedding module is configured to: calculate the total amount of low-frequency load shedding according to the steady-state frequency set value, detect that the frequency of the power system drops to the flexible load shedding set value, and preferentially shed the flexible load;

[0044] If the frequency rises after the flexible load is shed, the feeder shedding process is stopped;

[0045] If it is detected that the frequency does not rise significantly or does not rise, when it is detected that the frequency of the power system drops to the first round of action frequency of the low-frequency load shedding, a shedding instruction is issued;

[0046] The load shedding position and capacity are determined according to the frequency change rate, the load shedding is implemented, the feeder with the lowest total score is cut off, after the load shedding is completed, the frequency rise is detected, if the frequency rises, the low-frequency load shedding is ended, and if the frequency further drops, the next level of load shedding is entered;

[0047] The frequency adjustment module is configured to detect frequency change condition, stop the low-frequency load shedding process when the frequency rises, and enter a secondary frequency adjustment stage to adjust the frequency back to the range required by the working frequency.

[0048] The above one or more technical solutions have the following beneficial effects:

[0049] The feeder load shedding method considering the distributed power supply is based on a new feeder sorting method, retains the feeder with more distributed power supply output, realizes accurate cutting of the feeder load, and also considers preferentially cutting a part of flexible load to achieve better economic benefits. In the time period with more distributed power supply output, the scheme can effectively reduce the load shedding round and the amount of load shedding, the minimum frequency is higher, and the economy is better. In the time period with less distributed power supply output, the scheme can achieve slightly better effect than the traditional scheme.

[0050] Advantages of the additional aspects of the application will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the application. BRIEF DESCRIPTION OF DRAWINGS

[0051] The drawings accompanying the specification of this application form a part thereof, serve to provide further understanding of the application, and together with the description of the exemplary embodiments of the application given below, serve to explain the application, and do not constitute an improper limitation of the application.

[0052] Figure 1 It is a low-frequency load shedding schematic diagram;

[0053] Figure 2 It is a simulation result comparison schematic diagram before and after the distributed power supply is connected;

[0054] Figure 3 It is a feeder load shedding process schematic diagram considering the distributed power supply according to the embodiment of the application;

[0055] Figure 4 It is a simulation system network diagram;

[0056] Figure 5 It is a simulation frequency change diagram;

[0057] Figure 6 It is a load amount change diagram. DETAILED DESCRIPTION

[0058] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the application. Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the application belongs.

[0059] It is to be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application.

[0060] In the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0061] Embodiment one

[0062] Referring to the accompanying Figure 3 The embodiment discloses a feeder load shedding method considering distributed power supply, when a disturbance occurs, the load shedding master station issues an instruction according to the feeder ranking of the previous period, and the load shedding sub-station performs the shedding.

[0063] First, the influence of the distributed power output on the feeder power flow is analyzed, and the relationship between them is expressed by the following formula:

[0064] p(t) = p L (t) - p DG (t) (1)

[0065] In the formula: p(t) is the feeder net load power, p L (t) is the actual feeder load power, and p DG (t) is the distributed power. The traditional low-frequency load shedding decision takes p L (t) as the basis, and the sum of the actual load power of the feeder to be cut off meets the system power shortage. However, as can be seen from formula (1), for different feeders with the same actual load power p(t), the feeder with higher distributed power p DG (t) has smaller feeder net load power p(t), and the feeder with smaller net load power p(t) has less impact on the stability of the power system. Therefore, considering the influence of the distributed power output, the feeder net load power should be taken as the basis for load shedding.

[0066] The high proportion of distributed power supply on the user side supplies part of the local load power, but the distributed power output affects the measurement of the actual load. In the subsequent feeder priority ranking scheme, the distributed power output needs to be separated from the feeder net load power.

[0067] The feeder load shedding method considering distributed power supply includes the following specific steps:

[0068] Step 1): After the load shedding master station collects the feeder net load power, load frequency characteristics and other data, the load shedding master station performs real-time iteration sorting on each feeder according to the load shedding cost and load shedding effect;

[0069] Step 2): When the power system frequency drops to the flexible load shedding setting value, automatically act, and preferentially cut off the flexible load;

[0070] Step 3): If the frequency returns after cutting off the flexible load, stop the feeder cutting process. If it is detected that the frequency does not return or does not return significantly, it means that cutting off the flexible load does not work, and when it is detected that the power system frequency drops to the first action frequency of the low frequency load shedding, the cutting instruction is issued.

[0071] Step 4): After the jth level of load is cut off, the frequency return is detected, and the frequency return is detected. If the frequency further decreases, the j+1 level of load cutting is entered. Note that when the j+1 level of low frequency load shedding is not triggered at the low frequency point, the secondary round of load cutting is started. Here, it is still calculated as j+1 times of low frequency load shedding.

[0072] Step 5): Detect the frequency change, stop the low frequency load shedding process when the frequency returns, and enter the secondary frequency modulation stage to adjust the frequency back to the range required by the working frequency.

[0073] In step 1), the specific steps of feeder priority sorting are as follows:

[0074] Among them, the feeder priority sorting needs to consider the following indexes: load category, load frequency characteristic, distributed power, and power flow direction.

[0075] The analytic hierarchy process is used to quantitatively describe the load cutting priority of the feeder, and the following three indexes are set:

[0076] (1) Load category (w1);

[0077] (2) Load frequency characteristic (w2);

[0078] (3) Distributed power influence (w3);

[0079] A judgment matrix is constructed, and the weight of each index is calculated according to the importance of comparison. The judgment matrix formation criterion is shown in Table 1. Each index is divided into grades according to importance: the load category directly determines the low frequency load shedding cutting sequence, which is taken as the first grade target; the new scheme pays attention to the influence of distributed power on power flow, and the distributed power is taken as the second grade target; the load characteristic frequency is a 3-grade index.

[0080] Table 1 Judgment matrix formation criterion

[0081]

[0082]

[0083] Note: ① Scale 2, 4, 6, 8 represents the median of the above two adjacent judgments; ② Reciprocal: factor i and factor j are compared to determine b ij , factor j and factor i are compared to determine b ji = 1 / bij .

[0084] According to the above classification, the judgment matrix is as follows:

[0085]

[0086] Let the weights be:

[0087] w1+w2+w3=1 (3)

[0088] In the formula, w1, w2, and w3 represent the weights of the load category, the load frequency characteristic, and the distributed power generation influence respectively, and the matrix calculation can obtain:

[0089] w=[w1,w2,w3] T =[0.5813 0.1096 0.3091] T (4)

[0090] Multiply the score of each index by the corresponding weight to obtain the total score T of each feeder: i :

[0091] T i =(w1·S i1 +w2·S i2 +w3·S i3 )*δ (5)

[0092] According to the total score T of each feeder: i , sort all the feeders, exclude the feeders with a score of zero, and the feeders with a high score have a low priority, and the feeders with a low score are preferentially cut off. i1 S is the load category score, S i2 is the load frequency characteristic score, and S i3 is the distributed power generation influence score, and δ is the direction detection variable.

[0093] The above feeder sorting method considers the influence of distributed power output and quantifies it as an index to participate in feeder sorting and load shedding.

[0094] The scoring calculation steps of the feeder priority sorting index are as follows:

[0095] For each feeder i, each index is scored:

[0096] 1) Load category: The cost of load shedding of different categories is different, and generally, industrial load > commercial and residential load > flexible load.

[0097] Define the load category score S i1 :

[0098]

[0099] where VoLL i is the unit outage cost, a commonly used index to measure the cost of different load shedding, usually in dollars / kWh, VoLL base is the unit outage cost benchmark. For example, VoLL base is 100 $ / kWh, the VoLL g of industrial load is 20 $ / kWh, its S g1 = 0.2; the VoLL s of commercial load is 10 $ / kWh, its S s1 = 0.1, comparing the two values, it can be concluded that the priority of commercial load shedding is higher. Flexible load is different from other types of load, usually participating in demand response and economic dispatch of power market through incentive price mechanism.

[0100] Flexible load is a load that can actively participate in grid operation control and interact with the grid in energy, with flexible characteristics. Flexible load is divided into translatable load, transferable load and reducible load, and the three types of load have different incentive prices in different time periods. The power company provides different incentive prices for flexible load in different time periods, to guide users to reduce electricity consumption in the case of demand peak or grid pressure, optimize system cost and reduce unnecessary loss caused by load shedding. The incentive price of flexible load is much smaller than the shedding price of residential load, and the shedding cost is smaller, so a round of flexible load cutting is added before the feeder is cut off to improve the frequency dynamic.

[0101] 2) Load frequency characteristics: for traditional load, the frequency criterion for cutting is related to the frequency characteristics. The frequency characteristic coefficient K L The smaller the load, the lower the sensitivity to frequency change, and the power consumption will not be significantly reduced when the system frequency drops, so it cannot help the system restore balance through its own frequency response.

[0102] The load frequency characteristic score S i2 is defined as:

[0103]

[0104] where K Li is the frequency characteristic coefficient of the load on the feeder, P i is the power size of the load on the feeder, P b is the benchmark power, used for normalizing the power index.

[0105] The power system can measure the load frequency characteristics, specifically by installing frequency sensors and power meters on the load side of the feeder, and recording frequency change and load response data in real time.

[0106] 3) Distributed generation: Feeders with distributed power sources that have a positive effect on frequency characteristics should be considered for retention, that is, the net load power of the feeder should be used instead of the actual load power of the feeder as the standard for low-frequency load shedding.

[0107] Define the impact score S of distributed generation i3 :

[0108]

[0109] Feeders with lower performance indicators are prioritized for disconnection. Distributed power output is predicted using a neural network model.

[0110] Finally, since distributed generation can cause bidirectional power flow problems, a special indicator for judging the direction of power flow should be set: if the power flow of the feeder is from the distribution network to the main network during detection, it should not be cut off.

[0111] Let the detection variable δ be defined, where δ = 1 when the power flow direction is positive and δ = 0 when the power flow direction is negative. During implementation, feeders with a score of zero are preferentially excluded. After the integration of distributed generation, some feeders may experience reversed power flow. Traditional low-frequency load shedding schemes cannot detect this, leading to the disconnection of these feeders and further frequency degradation. The purpose of setting the detection variable is to identify feeders with reversed power flow, ensuring that the new scheme retains these feeders that are beneficial to system stability.

[0112] The net load power in the above formula (12) can be obtained by measurement, the distributed generation power is predicted by the following function, and the actual load power is calculated by formula (1) based on these two data.

[0113] Since the real-time output of distributed power sources cannot be measured in real time, the system predicts the real-time output based on historical data, feeder net load power, and environmental factors. The aforementioned historical data refers to historical weather and climate data recorded by the system for the region where the distributed power source is located.

[0114] Assume the net load power measurement of the k-th feeder over a period of time is:

[0115] p = [p1, p2, ..., p N ] T (9)

[0116] In the formula, N is the sequence time length.

[0117] Let the measurement sequence for the region during this period be s (light intensity), T (temperature), and w (wind intensity):

[0118] s = [s1, s2, ..., s N ] T (10)

[0119] T = [T1,T2,…,T]N ] T (11)

[0120] w = [w1, w2, ..., w N ] T (12)

[0121] Let the total power sequence of distributed photovoltaic power generation be p. pv Distributed wind power generation total power sequence p w Assuming the total power of distributed photovoltaic power generation is p pv There exists a nonlinear mapping relationship F between the light intensity s and the temperature T. pv (); Total distributed wind power generation p w There exists a nonlinear mapping relationship F between the wind force and the wind intensity w. w ( ), using a BP neural network to establish a separation prediction model for distributed power output:

[0122]

[0123] Where: V1,…,V n Let n be the weight matrix of the neural network, and n be the number of layers in the neural network. The loss function is defined as:

[0124]

[0125] In the formula: E pv p is the loss function used in distributed photovoltaic forecasting. PVi Contributing to the history of distributed photovoltaic power, ^p PVi To predict the output of distributed photovoltaic (PV) power, the gradient descent method is used to minimize the loss function, updating the weights and biases until the loss function is less than a certain threshold. At this point, the prediction model F for the real-time output of distributed PV power can be obtained. pv ().

[0126] To explain, in a neural network, weights are parameters connecting the neurons. When the neural network begins training, these weights are randomly initialized. With each iteration, the network updates the weights based on the error and gradient, ultimately fitting the model. The weight parameters are a transitional variable in the neural network algorithm, used only for model fitting.

[0127] Once the above-mentioned prediction model for real-time distributed photovoltaic power output is obtained, the real-time output of distributed power sources can be predicted based on the prediction model and the weather and environmental conditions of the day.

[0128] Prediction model F for distributed wind power generation w () can be obtained through the same training method:

[0129]

[0130] E w is the loss function used in distributed wind power prediction, p wi is the historical output of distributed wind power, is the predicted value of distributed photovoltaic power. Gradient descent method is used to minimize the loss function, and the weights and biases are updated until the loss function is less than a certain threshold, at which point the prediction model F of distributed wind power is obtained w .

[0131] Simulation comparison:

[0132] The distribution network is built as shown in the figure by using DIgSILENT\PowerFactory software. The distribution network is a combination of feeders containing loads, photovoltaic power generation and wind power generation, as shown in Figure 4 . The distribution system is a 110kV substation, in which the load is represented as an aggregated load connected to 11 20kV feeders. Among the 11 feeders, Load 1-Load 7 are set as residential loads, Load 8-Load 10 are set as commercial loads, and Load 11 is set as an industrial load. Generators, transformers, loads, wind power generation and photovoltaic power generation all use the standard models provided by DIgSILENT\PowerFactory. The distributed output is predicted, and three time points of 5 o'clock, 13 o'clock and 17 o'clock are selected to construct three simulation scenarios.

[0133] The frequency characteristics of active power and reactive power of different load models are as follows:

[0134]

[0135] The frequency parameters K pf and K qf of different types of loads are shown in Table 2; the distributed power output prediction in different time periods is shown in Table 3; and the scores of each feeder at different time points are shown in Table 4.

[0136] Table 2 Load frequency parameters

[0137]

[0138]

[0139] Table 3 Distributed power output prediction

[0140]

[0141] Table 4 Score of different feeders at different time points

[0142]

[0143] The frequency of cutting is from 49.5hz, and every 0.15hz cuts a round of load. A disturbance of a sudden load surge is applied to the system at 0.5s. When the low-frequency load shedding does not respond, the disturbance will make the system frequency drop below 49Hz, causing the system to be unstable. Using the traditional low-frequency load shedding strategy and the new low-frequency load shedding strategy, the frequency change of the system and the load change of the power distribution network after using different strategies are observed.

[0144] As shown in (a) of Figure 5 , the five-point time simulation frequency change diagram, the photovoltaic power generation in scene one is very weak, and the simulation results of the two schemes are very close. After cutting the small flexible load, both of them are cut for 3 times of low-frequency load shedding, and the lowest frequency of the system is about 49.2Hz. After the third round of load cutting, it rises to the allowed range of the recovery frequency.

[0145] As shown in (b) of Figure 5 , the thirteen-point time simulation frequency change diagram, the photovoltaic power generation in scene two is strong, and the comparison of the two schemes is obvious. The traditional scheme is actuated for 4 rounds, and 5 feeder lines are cut off. The lowest frequency point is about 49hz. The improved scheme is cut for 3 rounds, and 3 loads are cut off. The lowest frequency point is about 49.2hz. Compared with the traditional scheme, 86.4MW is less cut off.

[0146] As shown in (c) of the figure, the seventeen-point time simulation frequency change diagram, in scene three, the lowest frequency of the traditional scheme is 49.26Hz, and the lowest frequency of the improved scheme is 49.22Hz. This is because the method of cutting load considering distributed power supply changes slowly, and the overall action time is longer than that of the traditional method, resulting in a lower frequency. In view of this point, it can be considered to appropriately reduce the load cutting frequency interval of the improved scheme compared with the traditional scheme in the period when the photovoltaic power generation is weak.

[0147] The load cutting amount of the two schemes is shown in Figure 6 , where (a) is the five-point time load change, (b) is the thirteen-point time load change, and (c) is the seventeen-point time load change. The cutting load cost optimization is shown in Table 5. In scene one, the cutting load of the two schemes is basically the same. In scene two, there is a big difference in the cutting load amount between the two schemes. The traditional scheme cuts off 198.1MW of load, and the improved scheme cuts off 111.7MW of load. The improved scheme cuts off 86.4MW less, which is about 43.61% optimized. In scene three, the traditional scheme cuts off 107.1MW of load, and the improved scheme cuts off 91.9MW of load, which is about 14.19% optimized, but the number of load cutting stages is not reduced. The simulation results show that in the period of distributed power supply output, the new scheme can effectively improve the economic benefit of load cutting.

[0148] Table 5: Load shedding cost optimization at different times

[0149]

[0150] Example two

[0151] The purpose of the embodiment is to provide a computer device, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the processor implements the steps of the above method when executing the program.

[0152] Example three

[0153] The purpose of the embodiment is to provide a computer readable storage medium.

[0154] A computer readable storage medium, on which a computer program is stored, wherein the program is executable by a processor to implement the steps of the above method.

[0155] Example four

[0156] The purpose of the embodiment is to provide a feeder load shedding system considering distributed power supply, comprising:

[0157] A sorting module configured to: sort each feeder in real time according to load shedding cost and load shedding effect;

[0158] A load shedding module configured to: calculate the total amount of low-frequency load shedding according to the steady-state frequency set value, and detect that the power system frequency drops to the flexible load shedding set value, and preferentially shed the flexible load;

[0159] If the frequency rises after shedding the flexible load, the feeder shedding process is stopped;

[0160] If the frequency rise is not obvious or does not rise, when it is detected that the power system frequency drops to the first round of low-frequency load shedding action frequency, the shedding instruction is issued;

[0161] According to the frequency change rate, the load shedding position and capacity are determined, the load shedding is implemented, the feeder with the lowest total score is shed, after the load shedding is completed, the frequency rise is detected, if the frequency rises, the low-frequency load shedding is ended, and if the frequency further drops, the next load shedding is entered;

[0162] A frequency adjustment module configured to: detect the frequency change, when the frequency rises, stop the low-frequency load shedding process, and enter the secondary frequency modulation stage to adjust the frequency back to the range required by the working frequency.

[0163] Example five

[0164] The purpose of the embodiment is to provide a computer program product containing instructions, which, when running on a computer, causes the computer to perform the method and functions involved in any of the above embodiments.

[0165] The steps involved in the device of the above embodiment correspond to the method embodiment one, and the specific implementation can refer to the relevant description part of embodiment one. The term "computer readable storage medium" should be understood as including a single medium or multiple media of one or more instruction sets; it should also be understood as including any medium capable of storing, encoding or carrying instruction sets for execution by a processor and causing the processor to perform any of the methods in the present application.

[0166] Those skilled in the art should understand that the above modules or steps of the present application can be realized by a general computer device, alternatively, they can be realized by program codes executable by a computing device, so that they can be stored in a storage device for execution by a computing device, or they can be made into individual integrated circuit modules, or a plurality of modules or steps among them can be made into a single integrated circuit module. The present application is not limited to any specific combination of hardware and software.

[0167] Although the specific embodiments of the present application are described above in combination with the drawings, it is not a limitation on the scope of protection of the present application, and those skilled in the art should understand that various modifications or changes made on the basis of the technical solutions of the present application without creative labor are still within the scope of protection of the present application.

Claims

1. A feeder load shedding method considering distributed power sources, characterized by, The method comprises the following steps: real-time iteration sorting of each feeder according to the load shedding cost and the load shedding effect; calculating the total amount of low-frequency load shedding according to the steady-state frequency set value; detecting that the power system frequency drops to the flexible load shedding set value, and preferentially shedding the flexible load; if the frequency rises after the flexible load is shed, stopping the feeder shedding process; if the frequency rise is not obvious or does not rise, when it is detected that the power system frequency drops to the first round of low-frequency load shedding frequency, issuing a shedding instruction; determining the load shedding position and capacity according to the frequency change rate, implementing load shedding, and shedding the feeder with the lowest total score, and after the load is shed, detecting the frequency rise, and ending the low-frequency load shedding if the frequency rises, or entering the next level of load shedding if the frequency further drops; detecting the frequency change, and when the frequency rises, stopping the low-frequency load shedding process and entering the secondary frequency modulation stage to adjust the frequency to the range required by the working frequency; determining the load shedding position and capacity according to the frequency change rate, implementing load shedding, and separating the distributed power output from the feeder net load power when load shedding.

2. The feeder load shedding method considering distributed power sources according to claim 1, characterized in that, The priority of the feeder is sorted, and the specific steps are as follows: The set indexes include: load category, load frequency characteristic and distributed power generation influence; grading each index according to importance, and obtaining a judgment matrix according to the grading; calculating the weight of each index based on the judgment matrix; multiplying the score of each index by the corresponding weight to obtain the total score of each feeder, and sorting all feeders according to the total score of each feeder.

3. The method of claim 2, wherein the method further comprises: determining a power flow of the distribution system; and determining a power flow of the distribution system after the feeder load is removed. Grading each index according to importance, including: the load category as the first grade target; the distributed power generation as the second grade target; and the load characteristic frequency as the third grade index.

4. The method of claim 2, wherein the method further comprises: determining if the distributed power source is connected to the feeder line; and if the distributed power source is connected to the feeder line, then determining if the distributed power source is connected to the load. The score of each index includes the load category score, the load frequency characteristic score and the distributed power generation influence score; The load category score is the ratio of the unit outage cost to the unit outage cost reference value; The load frequency characteristic score is the ratio of the product of the power of the load on the feeder and the frequency characteristic coefficient of the load on the feeder to the reference power; The distributed power generation influence score is the ratio of the sum of the actual load power and the distributed power to the net load power.

5. The method of claim 1, wherein the method further comprises: determining if the distributed power source is connected to the feeder line; and if the distributed power source is connected to the feeder line, then determining if the distributed power source is connected to the load. The distributed power output is predicted by historical data, feeder net load power and environmental factors; When predicting the distributed power output: obtaining a measurement sequence corresponding to the light intensity, temperature and wind intensity in a region within a period of time; setting a distributed photovoltaic power sequence and a distributed wind power sequence; assuming that there is a certain nonlinear mapping relationship between the distributed photovoltaic power and the light intensity and temperature, and that there is a certain nonlinear mapping relationship between the distributed wind power and the wind intensity; using a BP neural network to establish a separation prediction model of the distributed power output, including: establishing a prediction model of the distributed photovoltaic real-time output; and establishing a prediction model of the distributed wind power generation; predicting the distributed power real-time output based on the established model.

6. A feeder load shedding system considering distributed generation, characterized by, The method comprises the following steps: a sorting module configured to: real-time iteration sort each feeder according to the load shedding cost and the load shedding effect. The load shedding module is configured to calculate the total amount of low-frequency load shedding according to the steady-state frequency setting value, detect that the frequency of the power system drops to the flexible load shedding setting value, and preferentially shed the flexible load; If the frequency rises after the flexible load is shed, the feeder shedding process is stopped; If the frequency rise is not obvious or does not rise, when it is detected that the frequency of the power system drops to the first round action frequency of the low-frequency load shedding, a shedding instruction is issued; The load shedding position and capacity are determined according to the frequency change rate, the load shedding is implemented, the feeder with the lowest total score is shed, after the load is shed, the frequency rise is detected, if the frequency rises, the low-frequency load shedding is ended, and if the frequency further drops, the next load shedding is entered; The frequency adjustment module is configured to detect the frequency change, when the frequency rises, the low-frequency load shedding process is stopped, and a secondary frequency modulation stage is entered to adjust the frequency back to the range required by the working frequency; The load shedding position and capacity are determined according to the frequency change rate, the load shedding is implemented, and when the load shedding is implemented, the distributed power output is separated from the feeder net load power as the reference for load shedding.

7. A computer program product comprising a computer program, characterized in that, The computer program is executed by a processor to implement the method of any one of claims 1 to 5.

8. A computer device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor executes the program to implement the steps of the method of any one of claims 1 to 5.

9. A computer-readable storage medium having stored thereon a computer program, characterized in that, The program is executed by a processor to implement the steps of the method of any one of claims 1 to 5.

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