Disclosure of Invention
The present invention has been made in view of the above-described problems.
Therefore, the technical problems solved by the invention are as follows: the existing reliability analysis method has the problems of larger limitation of a calculation method, insufficient artificial intelligence algorithm and optimization of how to comprehensively consider the influence of distributed power supply access on the power distribution network.
In order to solve the technical problems, the invention provides the following technical scheme: the distributed power distribution network reliability assessment method based on the deep neural network comprises the steps of obtaining wind speed data and constructing a wind turbine output model and a photovoltaic output model; distributing a maximum acceptable distributed power capacity to each node in the power distribution network; the raw data set is obtained by a modified monte carlo method, the neural network is trained and predicted.
As a preferable scheme of the reliability evaluation method of the distributed power distribution network based on the deep neural network, the invention comprises the following steps: the wind turbine generator output model comprises the steps of modeling and predicting wind speed by adopting an ARMA model, calculating a wind speed average value and a standard deviation of wind speed distribution based on original wind speed data, and processing the original wind speed data to obtain standardized data, wherein the relationship between the standardized data and the original wind speed data is expressed as follows:
Wherein y t is standardized data, V t is raw wind speed data, μ is an average value of wind speeds, σ is a standard deviation of wind speed distribution, and the ARMA model is expressed as:
yt=a1yt-1+a2yt-2+…+amyt-m+
αt+c1αt-1+c2αt-2+…cnαt-n
Wherein a i is an autoregressive coefficient, c i is a moving average coefficient, alpha t is normally distributed white noise, and the relation between the output and wind speed of the wind turbine generator set is expressed as:
Wherein a, b, c are related to cut-in wind speed and rated wind speed, and a, b, c are expressed as:
v a is the cut-in wind speed of the wind turbine, V b is the rated wind speed of the wind turbine, V c is the cut-out wind speed of the wind turbine, and P e is the rated power of the wind turbine.
As a preferable scheme of the reliability evaluation method of the distributed power distribution network based on the deep neural network, the invention comprises the following steps: the photovoltaic output model comprises an output model for obtaining a photovoltaic power generation system through simulated solar radiation intensity, the output of the photovoltaic power generation system is positively correlated with the solar radiation intensity, and the functional relation is expressed as follows:
P=rAηK
Where r is solar radiation intensity, A is the area of the photovoltaic array, η is the conversion efficiency of the module to convert light energy into electrical energy, and K is the correction coefficient.
As a preferable scheme of the reliability evaluation method of the distributed power distribution network based on the deep neural network, the invention comprises the following steps: the maximum acceptable distributed power supply capacity comprises Zeno polyhedrons, zeno polyhedron is a special symmetric polyhedron, defined as the minkowski sum of finite segments, expressed as:
Wherein c epsilon R n is the center of Zeno polyhedron, g (i)∈Rn is the generation vector of Zeno polyhedron, and the uncertain output of the distributed power supply is represented by Zeno polyhedron.
As a preferable scheme of the reliability evaluation method of the distributed power distribution network based on the deep neural network, the invention comprises the following steps: the maximum acceptable distributed power supply capacity further comprises constructing an uncertain input set, and setting the predicted power of three distributed power supplies asThe output of each distributed power supply has uncertainty of +/-30%, and three directional line segments are obtained and expressed as:
g1=[0.12 0 0]T
g3=[0 0 0.15]T
A Zeno polyhedron was obtained, the power uncertainty set being a rectangular prism centered on [ 0.4.0.5.0.6 ] T, each of side lengths 0.24,0.18,0.3.
As a preferable scheme of the reliability evaluation method of the distributed power distribution network based on the deep neural network, the invention comprises the following steps: the improved monte carlo method includes obtaining, by mathematical sampling, a sampled version of the time to failure TTF and time to repair TTR of the component, expressed as:
R1 and R2 are random numbers in intervals (0 and 1), original parameters of a power distribution network are read and data are initialized, N power elements are arranged in a system, a group of random numbers delta 1,δ2,...,δn are generated, the number of the random numbers is the same as that of the elements in the power distribution network, the range of the random numbers is between (0 and 1), based on an element time sampling formula, the non-fault working time TTF of each element is calculated according to the generated random numbers, the non-fault working time is compared, the power element with the minimum non-fault working time in the fault element is determined, the trend of the system after the fault is calculated, the node voltage of each node after the fault is determined, whether the distributed power supply is offline is determined, the overvoltage influence range caused by the fault is determined if the distributed power supply is not offline, the running state of each load point is determined, the random running time of the system is calculated, the evaluation process is repeated if the running time of the system is smaller than a simulation period, the fault times and the fault time of each load point in the simulation period are calculated, and the reliability index of the system is calculated if the running time of the system is larger than or equal to the simulation period.
As a preferable scheme of the reliability evaluation method of the distributed power distribution network based on the deep neural network, the invention comprises the following steps: the method comprises the steps of training a neural network and predicting the BP neural network, selecting the capacity of each distributed power supply as an input parameter of the BP neural network, selecting a system average outage frequency index, a system average outage duration index and an expected outage amount as the output of the BP neural network, for input characteristics, enabling all input parameters to be in the same competition status, reducing calculation errors caused by the data, firstly, establishing an output model of the distributed power supply, determining a possible output range of the distributed power supply at each moment according to the uncertainty modeling based on Zeno polyhedrons, obtaining the maximum accessible capacity of the distributed power supply through power flow calculation according to the requirement of electric energy quality, obtaining an original dataset for training through a Monte Carlo simulation process, training the neural network model by using a normalized sample after determining the input and output parameters, obtaining a trained neural network model, and predicting by using the trained neural network model.
Another object of the present invention is to provide a distributed power distribution network reliability evaluation system based on a deep neural network, which can train the neural network and perform reliability prediction through a training prediction module, so as to solve the problem of low efficiency when dealing with large-scale and complex power distribution networks at present.
As a preferred scheme of the distributed power distribution network reliability evaluation system based on the deep neural network, the invention comprises the following steps: the system comprises a model building module, a power capacity module and a training prediction module; the model building module is used for obtaining wind speed data and building a wind turbine generator set output model and a photovoltaic output model; the power capacity module is used for distributing a maximum acceptable distributed power capacity to each node in the power distribution network; the training prediction module is used for obtaining an original data set through an improved Monte Carlo method, training a neural network and predicting.
A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that execution of the computer program by the processor is the step of implementing a method for evaluating reliability of a distributed power distribution network based on a deep neural network.
A computer readable storage medium having stored thereon a computer program, characterized in that the computer program when executed by a processor implements the steps of a method for evaluating reliability of a distributed power distribution network based on a deep neural network.
The invention has the beneficial effects that: according to the distributed power distribution network reliability assessment method based on the deep neural network, the influence of environmental factors is considered through the output models of the wind turbine generator system and the photovoltaic power generation system, the practical applicability of the models is enhanced, the reliability index is calculated by adopting the improved Monte Carlo method, the calculation efficiency and accuracy are improved, the reliability index is rapidly predicted through the BP neural network, the analysis time is remarkably shortened, the real-time assessment of the reliability of the large-scale distributed power supply access to the power distribution network is realized, bad weather conditions are effectively met, the reliability assessment efficiency and accuracy of the power distribution network are improved, the safe and stable operation of the power grid is promoted, the access and management of the distributed power supply are optimized, and the method has better effects in the analysis time, the assessment accuracy and the assessment efficiency.
Detailed Description
So that the manner in which the above recited objects, features and advantages of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments, some of which are illustrated in the appended drawings. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
Example 1
Referring to fig. 1-2, for one embodiment of the present invention, a method for evaluating reliability of a distributed power distribution network based on a deep neural network is provided, including:
S1: and acquiring wind speed data, and constructing a wind turbine generator output model and a photovoltaic output model.
Further, the wind turbine generator output model comprises the steps of modeling and predicting wind speed by adopting an ARMA model.
It should be noted that, based on the original wind speed data, the standard deviation of the wind speed average value and the wind speed distribution is calculated, and the original wind speed data is processed to obtain standardized data, and the relationship between the standardized data and the original wind speed data is expressed as:
Wherein y t is standardized data, V t is raw wind speed data, μ is an average value of wind speeds, σ is a standard deviation of wind speed distribution, and the ARMA model is expressed as:
yt=a1yt-1+a2yt-2+…+amyt-m+
αt+c1αt-1+c2αt-2+…cnαt-n
Wherein a i is an autoregressive coefficient, c i is a moving average coefficient, alpha t is normally distributed white noise, and the relation between the output and wind speed of the wind turbine generator set is expressed as:
Wherein a, b, c are related to cut-in wind speed and rated wind speed, and a, b, c are expressed as:
v a is the cut-in wind speed of the wind turbine, V b is the rated wind speed of the wind turbine, V c is the cut-out wind speed of the wind turbine, and P e is the rated power of the wind turbine.
Further, the photovoltaic output model comprises an output model of the photovoltaic power generation system obtained through the simulated solar radiation intensity.
It should be noted that, the output of the photovoltaic power generation system is positively correlated with the solar radiation intensity, and the functional relationship is expressed as follows:
P=rAηK
Where r is solar radiation intensity, A is the area of the photovoltaic array, η is the conversion efficiency of the module to convert light energy into electrical energy, and K is the correction coefficient.
S2: each node in the distribution network is allocated a maximum acceptable distributed power supply capacity.
Still further, the maximum acceptable distributed power capacity comprises a Zeno polyhedron.
It should be noted that Zeno polyhedrons are a special symmetrical polyhedron, defined as minkowski sums of finite segments, expressed as:
Wherein c epsilon R n is the center of Zeno polyhedron, g (i)∈R n is the generation vector of Zeno polyhedron, and the uncertain output of the distributed power supply is represented by Zeno polyhedron.
Still further, the maximum acceptable distributed power supply capacity further includes constructing an uncertainty input set.
It should be noted that, let the predicted power of three distributed power sources beThe output of each distributed power supply has uncertainty of +/-30%, and three directional line segments are obtained and expressed as:
g1=[0.12 0 0]T
g2=[0 0.09 0]T
g3=[0 0 0.15]T
A Zeno polyhedron was obtained, the power uncertainty set being a rectangular prism centered on [ 0.4.0.5.0.6 ] T, each of side lengths 0.24,0.18,0.3.
It should also be noted that, assuming that there is an uncertainty of ±30% per hour of the wind turbine output, an hour-by-hour wind turbine output model is obtained using the ARMA model, and assuming that the rated capacity of the wind turbine is 1MW, if at a certain moment the predicted power of the wind turbine is 60% of the rated capacity, then the possible output power is in the range of [0.42,0.78] MW, in which case it is necessary to ensure that the node voltage of the wind turbine access point meets the power quality requirement, i.e. the voltage deviation cannot exceed ±7%.
S3: the raw data set is obtained by a modified monte carlo method, the neural network is trained and predicted.
Still further, the improved monte carlo method includes sampling by mathematics.
It should be noted that a sampled version of the time to failure TTF and time to repair TTR of the element is obtained, expressed as:
R1 and R2 are random numbers in intervals (0 and 1), original parameters of a power distribution network are read and data are initialized, N power elements are arranged in a system, a group of random numbers delta 1,δ2,...,δn are generated, the number of the random numbers is the same as that of the elements in the power distribution network, the range of the random numbers is between (0 and 1), based on an element time sampling formula, the non-fault working time TTF of each element is calculated according to the generated random numbers, the non-fault working time is compared, the power element with the minimum non-fault working time in the fault element is determined, the trend of the system after the fault is calculated, the node voltage of each node after the fault is determined, whether the distributed power supply is offline is determined, the overvoltage influence range caused by the fault is determined if the distributed power supply is not offline, the running state of each load point is determined, the random running time of the system is calculated, the evaluation process is repeated if the running time of the system is smaller than a simulation period, the fault times and the fault time of each load point in the simulation period are calculated, and the reliability index of the system is calculated if the running time of the system is larger than or equal to the simulation period.
Still further, training the neural network and making predictions includes BP neural network.
It should be noted that, the capacity of each distributed power supply is selected as the input parameter of the BP neural network, the average power failure frequency index of the system, the average power failure duration index of the system and the expected power failure amount are selected as the output of the BP neural network, for the input characteristics, the data of the input parameters are in the same order of magnitude, all the input parameters are in the same competition status, the calculation error caused by the data is reduced, firstly, the output model of the distributed power supply is established, the possible output range of each moment of the distributed power supply is determined according to the uncertainty modeling based on Zeno polyhedrons, the accessible maximum capacity of the distributed power supply is obtained through the calculation of the power flow according to the requirement of the electric energy quality, the original dataset for training is obtained through the monte Carlo simulation process, after the input and output parameters are determined, the trained neural network model is obtained through the normalized sample set training, and the trained neural network model is used for prediction.
It should also be noted that the BP neural network is a multi-layer feedforward neural network, the weight adjustment adopts a back propagation algorithm, the firing function of the neurons is a sigmoid type function, and the output is a continuous value between [0,1 ].
It should also be noted that the learning process of the BP neural network may be divided into two main stages, a known training set is input, and the neurons of each layer are obtained by recursion layer by layer from the neurons of the first layer through the set network structure and the weights and thresholds set in the last iteration or initial setting; the influence of the weight and the threshold value of each neuron on the output of the last layer of neurons is calculated, namely the weight and the threshold value are modified by transferring gradients and errors layer by layer, and the learning process is repeated until the total error reaches the required error performance.
It should also be noted that for output parameters, if the magnitude of the phase difference between the output parameters is too large, then an output parameter of a larger magnitude will have a larger absolute error, and an output parameter of a smaller magnitude will have a smaller absolute error of the output data, so that the raw data must be normalized before the BP neural network is trained using the raw data.
Example 2
Referring to fig. 3-6, for one embodiment of the present invention, a method for evaluating reliability of a distributed power distribution network based on a deep neural network is provided, and in order to verify the beneficial effects of the present invention, scientific demonstration is performed through economic benefit calculation and simulation experiments.
An improved IEEE 33 node distribution system is adopted as a calculation example analysis of the reliability analysis of a distribution network, the system comprises 32 load nodes, 32 transformers, 5 circuit breakers and 3 distributed power supplies, and the structure of the calculation example is shown in figure 3.
As can be seen from fig. 4, when node 17 (LP 17) is connected to a distributed power supply, the voltage at each node in the distribution network changes, and the voltage at each node is increased by the switching-in of the distributed power supply, wherein the effect of the lifting of the branch end nodes is most obvious, and fig. 4 (b) is the maximum capacity of the distributed power supply that each node can accommodate under the power quality requirement.
When three distributed power supplies are connected in a grid mode, as each distributed power supply has a boosting function, the capacity of each distributed power supply cannot be simply calculated according to the maximum capacity of a single distributed power supply when the distributed power supplies are connected in the grid mode, the maximum accessible capacity of the 3 distributed power supplies is selected in various ways on the premise that the power quality of a line is met, in the invention, the maximum capacity of DG1 is 3.6MW, the maximum capacity of DG2 is 1.35MW, the maximum capacity of DG3 is 2.5MW, and the uncertainty of 30% is assumed in the invention.
As can be seen from fig. 6, when the line 22 fails, the possible ranges of node voltages of the node 17, the node 21 and the node 32 are the voltage ranges without failure, the solid line is the voltage range after failure, and the occurrence of failure may cause the node voltage to rise, which may cause the generation of overvoltage, in which case the distributed power supply needs to be disconnected from the power grid, the overvoltage node needs to be cut off, and the system reliability will be affected.
As can be seen from fig. 7, when the capacities of the distributed power sources are different, the reliability of the distribution network changes, in general, as the access capacity of the distributed power sources is closer to the maximum allowable capacity, the reliability of the distribution network is lower, when the access capacity is not more than 50% of the maximum accessible capacity, the reliability of the distribution network is not significantly affected by the change of the capacity of the distributed power sources, and when the access capacity is close to the maximum accessible capacity, the reliability of the distribution network is significantly affected by the change of the capacity of the distributed power sources.
When the capacities of the distributed power sources are different, the reliability index value of the power distribution network is quantitatively calculated, the capacity of the distributed power sources is represented by the percentage of the maximum accessible capacity, when the capacity of the distributed power sources is changed, the reliability index calculation result of the power distribution network is shown in table 1, in order to realize the prediction of the reliability index of the power distribution network by the BP neural network, firstly, the original data obtained from a simulation experiment is required to be normalized so as to obtain a data set for training the BP neural network, finally, the trained BP neural network model is utilized for prediction, and the accuracy and the prediction error of the prediction are compared and analyzed, wherein part of the original data is shown in table 1, and the real data, the prediction result and the error are shown in table 2.
The BP neural network model mainly comprises network layer number design, namely the number of hidden layers, the number of hidden layer nodes, an activation function and a training method, wherein a single hidden layer can finish nonlinear mapping by increasing the number of nodes on the hidden layer, but increasing the hidden layer number can lead to the reduction of an analyzable network scale, the number of hidden layer nodes can not be obtained through an analysis method, the approximate range of the hidden layer nodes can only be obtained through an empirical formula, and then the optimal node number is obtained through continuous experiments. According to the result in the table, the reliability index value of the power distribution network predicted by the BP neural network is basically consistent with the reliability index value of the power distribution network directly obtained by the improved Monte Carlo method, the error is smaller, meanwhile, in the calculation example, when the reliability index is calculated by adopting the improved Monte Carlo method, the calculation time and cost of the method are greatly increased, the running time is about 29.56 seconds, when the reliability index is calculated by adopting the trained BP neural network, only about 0.06 seconds is needed, the rapidity of the reliability analysis of the power distribution network based on the BP neural network is reflected, when the power distribution network structure is complex, more time is needed for calculating the reliability index of the power distribution network by using the Monte Carlo method, at the moment, more time can be saved by calculating the reliability index by utilizing the BP neural network, and the superiority of an artificial intelligent algorithm is better embodied.
TABLE 1 reliability index Table for different distributed Capacity distribution networks
| DG capacity |
DG2 capacity |
DG3 capacity |
SAIFI |
SAIDI |
EENS |
| 20% |
40% |
40% |
1.0239 |
5.8677 |
20.4164 |
| 30% |
50% |
80% |
1.0310 |
5.9283 |
20.9339 |
| 40% |
70% |
80% |
1.0327 |
5.9232 |
20.8973 |
| 50% |
60% |
50% |
1.0279 |
5.9078 |
20.5910 |
| 50% |
80% |
80% |
1.0415 |
5.9999 |
21.0698 |
| 60% |
50% |
50% |
1.0310 |
5.9299 |
20.6954 |
| 70% |
80% |
80% |
1.0554 |
6.1563 |
21.6529 |
| 80% |
60% |
80% |
1.0676 |
6.2851 |
22.1225 |
| 100% |
100% |
100% |
1.1344 |
6.9246 |
24.6625 |
TABLE 2 prediction results and error Table for BP neural network
| |
Real data |
Prediction |
Error of |
Real data |
Prediction |
Error of |
| SAIFI |
1.066 |
1.068 |
0.21% |
1.081 |
1.091 |
0.92% |
| SAIDI |
6.276 |
6.298 |
0.36% |
6.414 |
6.527 |
1.77% |
| EENS |
22.325 |
22.151 |
0.78% |
22.987 |
23.060 |
0.32% |
Example 3
Referring to fig. 7, for one embodiment of the present invention, there is provided a distributed power distribution network reliability evaluation system based on a deep neural network, including: the system comprises a model construction module, a power capacity module and a training prediction module.
The model building module is used for obtaining wind speed data and building a wind turbine generator set output model and a photovoltaic output model; the power capacity module is used for distributing a maximum acceptable distributed power capacity to each node in the power distribution network; the training prediction module is used for obtaining an original data set through the improved Monte Carlo method, training the neural network and predicting.
The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution in the form of a software product stored in a storage medium, comprising several instructions for causing a computer device (which may be a personal computer, a server, a network device, etc.) to perform all or part of the steps of the method of the embodiments of the present invention. And the aforementioned storage medium includes: a usb disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
Logic and/or steps represented in the flowcharts or otherwise described herein, e.g., a ordered listing of executable instructions for implementing logical functions, can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For the purposes of this description, a "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device.
More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic device) having one or more wires, a portable computer diskette (magnetic device), a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium may even be paper or other suitable medium upon which the program is printed, as the program may be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner, if necessary, and then stored in a computer memory.
It is to be understood that portions of the present invention may be implemented in hardware, software, firmware, or a combination thereof. In the above-described embodiments, the various steps or methods may be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, may be implemented using any one or combination of the following techniques, as is well known in the art: discrete logic circuits having logic gates for implementing logic functions on data signals, application specific integrated circuits having suitable combinational logic gates, programmable Gate Arrays (PGAs), field Programmable Gate Arrays (FPGAs), and the like. It should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention may be modified or substituted without departing from the spirit and scope of the technical solution of the present invention, which is intended to be covered in the scope of the claims of the present invention.
It should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention may be modified or substituted without departing from the spirit and scope of the technical solution of the present invention, which is intended to be covered in the scope of the claims of the present invention.