Disclosure of Invention
The invention provides a diagnosis method of transformer direct current magnetic biasing based on a fuzzy neural network, which comprises the following steps:
step 1: selecting fundamental frequency amplitude p of transformer vibrationf50Frequency complexity FC, ratio of odd-even sub-harmonic amplitudes λoeAs the characteristic quantity, a vibration sensor is adopted to collect vibration signal data of the transformer during working, and the data is analyzed and processed to obtain the characteristic quantity parameter of the transformer at the moment;
step 2: constructing a membership function and a neural network, and initializing related parameters;
and step 3: dividing the sample into a training set and a verification set, and training the neural network containing the membership function by using the training set until the error meets the requirement;
and 4, step 4: verifying the effectiveness of the trained model on a verification set;
and 5: searching key values in the membership function of the three characteristic quantities by using a trained model through a traversal method, thereby determining membership function parameters and obtaining a fault probability curve for fault diagnosis; the output of the trained model can only represent whether the transformer has faults or not, namely the output set is [0,1 ];
step 6: and obtaining the fault probabilities corresponding to the three characteristic quantities according to the fault probability curve, and taking the weighted average as the final fault probability of the transformer, namely the probability of DC magnetic biasing.
Further, the frequency complexity FC, the ratio λ of the odd-even sub-harmonic amplitudesoeThe calculation method (2) is shown in the following formulas (1) and (2):
wherein the fundamental frequency amplitude pf5050Hz frequency amplitude of 100-2000 Hz;
further, the neural network architecture in step 2 is composed of six layers, which are an input layer, a quantized input layer, 3 hidden layers and an output layer, wherein each hidden layer is provided with 6 neurons; the membership function is an S-shaped function, and is shown as a formula (3).
The first layer of the neural network is an input layer, x1,x2,x3The number of the nodes is 3, and the input layer transmits the collected characteristic quantity data to the second layer; the second layer is a quantitative input layer, the input variable is fuzzified through a membership function, the number of nodes is three, and each node represents a fuzzy set; the third to the fifth layers are hidden layers of the network; and the sixth layer is an output layer, the output results are 0 and 1, 1 represents that the transformer generates direct current magnetic biasing, and 0 represents that the transformer has no direct current magnetic biasing.
Further, the step 3 specifically includes:
step S31: inputting a training sample and expected output, and setting the learning error and the maximum training frequency;
step S32: initializing parameters of a membership function and each connection weight of nodes in a neural network;
step S33: inputting samples, fuzzifying the samples by using a membership function of the 2 nd layer, calculating the fuzzified samples by using the 3 rd to 5 th layers, and outputting the fuzzified samples by using the 6 th layer;
step S34: calculating the square error E (i) between the obtained target value and the actual value, and judging whether the error requirement is met;
step S35: if the requirement is not met, back propagation is carried out, parameter adjustment quantity of each layer is calculated, the parameters are updated, and if the requirement is met, the trained network and the trained parameters are stored.
Further, the determining parameters of the membership function in step 5 refers to determining parameters α and β of a membership function s (x), and specifically includes:
when the characteristic quantity X is larger than a certain specific value, no matter how the other two characteristic quantities take values, the neural network can judge that the neural network is in a fault state, and at the moment, the characteristic quantity X is recorded as XHNamely, as shown in formula (4):
taking epsilon as a minimum value, the formula (5) is shown as follows:
the finishing can be obtained as shown in formula (6):
finding a point X on the membership function curveMSo that the output of the trained model in step 5 changes from 0 to 1, assuming a point XMThe corresponding failure probability in the membership function curve s (x) is 1/2, i.e. as shown in equation (7),
the finishing is shown as a formula (8):
β=-XM=f(X1,X2) (8),
wherein, X1,X2Are two characteristic quantities other than X; f (X)1,X2) Fitting X by testing the existing networkMCurve (c) of (d).
Detailed Description
The invention is described in detail below with reference to the figures and the specific examples.
In order to solve the problem of data labeling with insufficient sample quantity required by the existing diagnosis method, the invention constructs the labeling method of the transformer vibration data by using the thought of fuzzy mathematics, taking the vibration signal of the transformer as input, taking an expert knowledge base as a core, and taking the data labeled with the transformer state information as output, constructs the membership function by using a fitting method, reduces the requirement on expert knowledge, and verifies the effectiveness of the method by using a labeling experiment on sample data.
In the embodiment, a diagnosis method of the transformer direct current magnetic biasing based on the fuzzy neural network is disclosed, which comprises the following steps:
step S1: and obtaining the characteristic quantity parameters of the transformer at a certain moment.
The method comprises the steps of installing vibration sensors on the top surface and four side surfaces of a transformer, collecting vibration signals of the transformer during working, analyzing and processing the signals to obtain characteristic quantities, and labeling the obtained characteristic quantities to be divided into non-direct-current magnetic biasing and direct-current magnetic biasing. In this embodiment, the fundamental frequency amplitude p of the transformer vibration is selectedf50Frequency complexity FC, ratio of odd-even sub-harmonic amplitudes λoeAs the characteristic amount.
The frequency complexity and the ratio of odd-even sub-harmonic amplitudes are calculated as shown in the following formulas (1) and (2), respectively:
where FC is the frequency complexity, pf50In 100-2000Hz50Hz frequency amplitude.
Wherein λoeIs the ratio of the amplitudes of odd and even sub-harmonics
Step 2: constructing a membership function and a neural network, and initializing related parameters;
the neural network architecture applied in this embodiment is shown in fig. 1, and has six layers, namely an input layer, a quantized input layer, a 3-layer hidden layer, and an output layer, where each hidden layer has 6 neurons.
The first layer is an input layer, x1,x2,x3The number of the nodes is 3, and the input layer transmits the collected characteristic quantity data to the second layer.
The second layer is a quantitative input layer, the input variable is fuzzified through a membership function, the number of nodes is three, each node represents a fuzzy set and is used for calculating the membership value of the input component belonging to each fuzzy set, according to experience, the larger the characteristic quantity value is, the higher the possibility of the transformer generating direct current magnetic biasing is, so that the membership function of the system input variable selects an S-shaped function, as shown in formula (3):
the third to fifth layers are hidden layers of the network.
And the sixth layer is an output layer of the network, the output results are 0 and 1, 1 represents that the transformer generates direct current magnetic biasing, and 0 represents that the transformer has no direct current magnetic biasing.
The learning process of the fuzzy neural network is mainly divided into two stages, firstly, membership function parameters of each node of a fuzzy layer, namely alpha and beta in S (x), are solved according to an input transformer vibration characteristic quantity sample; then, after determining the number of neurons and their parameters, the weight between the hidden layer and the output layer is calculated, in the parameter optimization process, each gradient is calculated by adopting an error back propagation algorithm, then the parameters to be learned are adjusted by utilizing an optimization algorithm, and in the embodiment, the parameters α and β are optimized by adopting a first-order gradient optimization algorithm.
Step S3: training a neural network by using a training set sample, and specifically comprising the following steps:
step S31, inputting training sample and expected output, setting learning error and maximum training times
Step S32, initializing parameters of membership function and each connection weight of nodes in neural network
And step S33, inputting the sample, fuzzifying the sample by using the membership function of the 2 nd layer, calculating the fuzzified sample by using the 3 rd to 5 th layers, and outputting the fuzzified sample by using the 6 th layer.
Step S34, the square error e (i) between the calculated target value and the actual value is determined whether the error requirement is satisfied.
And step S35, if the requirement is not met, performing back propagation, calculating parameter adjustment quantity of each layer, updating the parameters, and if the requirement is met, storing the trained network and the trained parameters.
And step S36, verifying the validity of the trained model on the verification set.
Step S37, the output of the trained model can only indicate whether the transformer has a fault, i.e. the output set is [0,1], and in order to indicate the fault by the fault probability, we need to determine the parameters of the original membership function, i.e. α and β, by using the trained model.
To do this, we need to determine at least two points to determine the parameters of the sigmoid function.
When the characteristic quantity X is larger than a certain specific value, no matter how the other two characteristic quantities take values, the neural network can judge that the neural network is in a fault state, and at the moment, the characteristic quantity X is recorded as XH. It can be known that there are, for example,
taking epsilon as a minimum value, the above formula can be expressed,
after the finishing, the product can be obtained,
in a specific calculation, we can take epsilon as 0.001, (alpha, beta) epsilon [ (alpha, beta)1,β1),(α2,β2),(α3,β3) Represents pf50、λoeParameters in the membership function of the FC; xHRepresenting the input feature quantity variable.
For the characteristic quantity X, when we determine the other two characteristic quantities, one point X can be found on the membership function curveMSo that the output of the trained model changes from 0 to 1, it can be generally considered that this point corresponds to a failure probability of 1/2 in the membership function curve, which sometimes,
after the finishing, the product can be obtained,
β=-XM
find XMThe precondition for this is to determine the other two characteristic quantities, i.e. to determine
β=-XM=f(X1,X2)
Wherein, X1,X2Are two characteristic quantities other than X; f (X)1,X2) X can be fitted by carrying out value test on the existing networkMCurve (c) of (d).
Determine f (X)1,X2) Then, we can construct the membership function of three characteristic quantities, namely a fault probability curve.
And step S38, inputting the three characteristic quantities into the fault probability curves respectively to obtain corresponding fault probabilities, and taking the weighted average of the fault probabilities to obtain the final fault probability of the transformer, namely the probability of the occurrence of the direct current magnetic biasing.