A flow control method for transformer oil filling and discharge pipeline

Abstract

The present application relates to a flow control method for transformer oil filling and discharge pipelines, wherein the oil filling pipeline includes an oil inlet, an oil outlet, an oil storage tank outlet, and a transformer outlet, wherein a first oil discharge pipeline is provided between the oil inlet and the transformer outlet; a second oil discharge pipeline is provided between the oil outlet and the oil storage tank outlet, a first oil filling pipeline having a first oil discharge pipeline and a second oil discharge pipeline is connected between the oil storage tank outlet and the oil inlet, a second oil filling pipeline having a second oil discharge pipeline and a first oil discharge pipeline is connected between the oil outlet and the transformer outlet, and a first three-way ball valve and a second three-way ball valve are also provided in the oil filling and discharge pipelines. The present application uses the least squares method combined with a genetic algorithm through an ARX model to identify the relationship between the oil flow rate and the valve opening, thereby achieving precise control. The present application solves the problems of cumbersome steps and oil outflow during pipeline replacement in the oil filling and discharge process, and can ensure the stability of the oil flow rate through a control method.

Description

Technical Field

[0001] The present application relates to the technical field of transformer maintenance, and in particular to a method for controlling flow rate of a transformer oil filling and draining pipeline. Background Art

[0002] When oil-immersed transformers are being overhauled, it is usually necessary to inject and discharge insulating oil. The oil injection and discharge operation requires the use of an oil filter to release the old oil in the transformer, and then re-inject it into the transformer after filtering. Clean insulating oil can improve the transformer's withstand voltage, improve cooling and arc extinguishing effects, and ensure the long-term stable operation of the transformer.

[0003] When the oil filter is in use, its oil inlet and outlet are fixed. The inlet and outlet oil pipelines need to be replaced during the oil filling and draining process. This process requires the cooperation of at least 4 people, is time-consuming, and the insulating oil may flow out when the pipelines are replaced. Summary of the invention

[0004] The present application provides a method for controlling flow rate of transformer oil filling and draining pipelines, which solves the problems of complicated steps and oil outflow during pipeline replacement in the oil filling and draining process.

[0005] This method is implemented based on the transformer oil filling and discharge pipeline, which includes:

[0006] An oil inlet, wherein the oil is supplied to the oil filter;

[0007] An oil outlet, the oil outlet allowing the oil to flow out of the oil filter;

[0008] An oil tank port, the oil tank port being in communication with the oil tank so as to allow oil to flow into and out of the oil tank;

[0009] A transformer port, the transformer port being in communication with the interior of the transformer so as to allow oil to flow into and out of the transformer;

[0010] a first oil drain pipeline, the first oil drain pipeline being connected to the oil inlet and the transformer port respectively;

[0011] a second oil discharge pipeline, the second oil discharge pipeline is respectively connected to the oil outlet and the oil storage tank port;

[0012] a first oil filling pipeline, wherein the first oil filling pipeline is connected to the first oil discharge pipeline and the second oil discharge pipeline at a position close to the oil storage tank opening and the oil inlet, respectively, and forms a first three-way port with the second oil discharge pipeline at the connection position;

[0013] a second oil injection pipeline, wherein the second oil injection pipeline is connected to the second oil discharge pipeline and the first oil discharge pipeline at a position close to the oil outlet and the transformer port, respectively, and forms a second three-way port with the first pipeline at the connection position;

[0014] A first three-way ball valve, the first three-way ball valve is located at the first three-way port, and the first three-way ball valve is driven by a motor to move the ball valve;

[0015] The second three-way ball valve is located at the second three-way port, and the second three-way ball valve is driven by a motor to actuate the ball valve.

[0016] Furthermore, the first oil discharge pipeline and the second oil discharge pipeline are both straight pipelines, the first oil injection pipeline and the second oil injection pipeline are both broken line pipelines, and the first oil injection pipeline and the second oil injection pipeline are in a leaping type at the intersection;

[0017] A sensor, which is arranged on the inner wall of the first oil discharge pipeline and is used to collect oil flow data;

[0018] A power supply, the power supply being used to supply power to the first three-way ball valve, the second three-way ball valve and the sensor;

[0019] The lower computer is provided with a serial port connected to the upper computer, and the upper computer has a built-in PID controller.

[0020] This method is based on the single-input single-output model in the ARX model and specifically includes the following steps:

[0021] Step 1: Set the sampling period of the single-input single-output model h , with a sampling period h Collecting data samples ;in, is the opening signal value of the three-way ball valve, is the pipeline flow rate, N is the data sample length, t Indicates the length of the sampling period;

[0022] Step 2: Use the ARX model to identify data samples. The ARX model is as follows:

[0023] ;

[0024] In the formula, a 0. a i , b j are the model parameters to be estimated, n a , n b , k b is the structural parameter to be estimated, e ( t ) is zero-mean fixed white noise, is the structural parameter vector, is the model parameter vector;

[0025] in, ;

[0026] ;

[0027] ;

[0028] Step 3: Use the least squares method to estimate the structural parameters in the ARX model. The estimation of the structural parameters is as follows:

[0029] ;

[0030] In the formula, , , , They are , n a , n b , k b The estimated value of is the degree of fit, and its expression is:

[0031] ;

[0032] In the formula, For Related The estimated value of for The average value of

[0033] The expression is as follows:

[0034] ;

[0035] but: ;

[0036] In the formula, , They are a 0. b j An estimated value of

[0037] Step 4: Estimate the model parameter vector value using the least squares method based on the structural parameters :

[0038] ;

[0039] In the formula, ; ;

[0040] and: ;

[0041] Then the transfer function of the ARX model is:

[0042] ;

[0043] It follows that:

[0044]

[0045] Step 5: After reducing the order of the transfer function and performing continuous processing, the transfer function is obtained. The expression of this transfer function is as follows:

[0046] ;

[0047] In the formula, K is the proportionality coefficient, T is the time constant, τ is the delay constant;

[0048] The above transfer function is discretized and written as a difference equation:

[0049] Discretization: ;

[0050] Difference equation: ;

[0051] In the formula, b 1, b 2 are all constants;

[0052] Step 6: According to the difference equation in step 5, the controller parameters of PID , , , is the decision variable, and the genetic algorithm is used to adjust , , ;

[0053] The minimum objective function using the absolute value time integral of the error as parameter selection in the genetic algorithm is:

[0054] ;

[0055] Step 7: The host computer executes the first three-way ball valve and the second three-way ball valve according to the calculated values ​​of the PID controller parameters.

[0056] Furthermore, the opening states of the three-way ball valve in step one include closed, half-open, and fully open, and the corresponding opening signal values ​​are 0, 0.5, and 1, respectively.

[0057] Furthermore, in step six, a penalty factor is added to the objective function to achieve that when an overshoot condition occurs, the overshoot amount is used as the optimal indicator. The objective function after adding the penalty factor is as follows:

[0058] ;

[0059] In the formula, is the weighted value, and .

[0060] The beneficial effects of this application are:

[0061] 1. The pipeline designed in this application can reduce the number of workers, simplify the operating steps, and avoid the oil outflow of the transformer. During the use of the oil filter, the oil inlet and outlet are generally fixed. Therefore, when switching the oil filling and discharge process, it is necessary to switch the inlet and outlet oil pipelines. This process requires at least 4 people to cooperate, which is inefficient and may cause oil outflow during the switching process. However, this application realizes the automatic switching of the inlet and outlet oil of the oil filter. Only two people are needed to switch the pipeline, which reduces the process, can improve efficiency and avoid environmental pollution caused by oil outflow.

[0062] 2. This application collects input and output data through three valve opening states, uses the ARX model and least squares method to identify the mechanism relationship model between valve opening and pipeline flow, provides a reliable basis for determining the PID controller parameters, and maintains the oil flow in the pipeline constant through the PID controller. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 An oil flow diagram of a transformer oil filling and draining pipeline during oil filling and draining provided by the present application;

[0064] Figure 2 This is the schematic diagram of the PID controller in this application;

[0065] Figure 3 This is the flow chart of the genetic algorithm in this application;

[0066] Figure 4 This is a schematic diagram of the structure of the straight plug-in quick connector in this application;

[0067] In the attached drawings, 1, oil inlet; 2, oil outlet; 3, oil storage tank port; 4, transformer port; 5, first oil drain pipeline; 6, second oil drain pipeline; 7, first oil injection pipeline; 8, second oil injection pipeline; 9, first three-way ball valve; 10, second three-way ball valve. DETAILED DESCRIPTION

[0068] Based on the problems existing in the prior art described in the background technology, as shown in the attached Figure 1As shown, the present application provides a transformer oil filling and draining pipeline, comprising:

[0069] Oil inlet 1, the oil inlet 1 is for oil to enter the oil filter; oil outlet 2, the oil outlet 2 is for oil to flow out of the oil filter. Oil tank port 3, the oil tank port 3 is in communication with the oil tank so that the oil can flow into and out of the oil tank. Transformer port 4, the transformer port 4 is in communication with the inside of the transformer so that the oil can flow into and out of the transformer. First oil drain line 5, the first oil drain line 5 is connected to the oil inlet 1 and the transformer port 4, respectively. Second oil drain line 6, the second oil drain line 6 is connected to the oil outlet 2 and the oil tank port 3, respectively. First oil filling line 7, the first oil filling line 7 is connected to the first oil drain line 5 and the second oil drain line 6 near the oil tank port 3 and near the oil inlet 1, respectively, and forms a first three-way port with the second oil drain line 6 at the connection point. The second oil filling pipeline 8 is connected to the second oil draining pipeline 6 and the first oil draining pipeline 5 near the oil outlet 2 and the transformer port 4 respectively, and forms a second three-way port with the first pipeline at the connection point.

[0070] A first three-way ball valve 9, the first three-way ball valve 9 is located at the first three-way port, and the first three-way ball valve 9 is driven by a motor to operate. A second three-way ball valve 10, the second three-way ball valve 10 is located at the second three-way port, and the second three-way ball valve 10 is driven by a motor to operate.

[0071] During the use of the oil filter, the oil inlet 1 and the oil outlet 2 are generally fixed. Therefore, when switching between the filling and draining processes, the inlet and outlet oil pipelines need to be switched. This process requires at least 4 people to cooperate, which is inefficient and may cause oil to leak out during the switching process. However, the present application realizes the automatic switching of the inlet and outlet oil of the oil filter. Only two people are needed to switch the pipelines, which reduces the number of processes, improves efficiency, and avoids environmental pollution caused by oil leaks. Figure 1 The direction of the arrow is the flow direction of the oil.

[0072] As a preferred embodiment of the present application, the first oil discharge pipeline 5 and the second oil discharge pipeline 6 are both straight pipelines, the first oil injection pipeline 7 and the second oil injection pipeline 8 are both broken line pipelines, and the first oil injection pipeline 7 and the second oil injection pipeline 8 are in a leaping type at the intersection.

[0073] In the present application, the connection between the oil filling and draining pipelines can be achieved by using existing technologies. For example, the oil filling and draining pipelines can be connected in the form of threaded connection.

[0074] In this application, if attached Figure 4As shown in the figure, considering the factors of docking time and oil flow pressure, the oil inlet 1 and the oil outlet 2 can be connected to the external pipeline through a straight plug-in quick connector. The straight plug-in quick connector is divided into a sub-body and a parent body. When the sub-body and the parent body are embedded, the ferrule in the straight plug-in quick connector returns to the original position under the action of the spring, and the steel column rolls and locks the sub-body to achieve a tight connection. At the same time, the valves of the parent body and the sub-body push each other to open, and the fluid flows.

[0075] As a preferred embodiment of the present application, the transformer oil filling and discharge pipeline also includes:

[0076] A sensor, which is arranged on the inner wall of the first oil discharge pipeline 5 and is used to collect oil flow data;

[0077] A power supply, which is used to supply power to the first three-way ball valve 9, the second three-way ball valve 10 and the sensor;

[0078] The lower computer is provided with a serial port connected to the upper computer, and the upper computer has a built-in PID controller. The power supply can be an external power supply, and an air switch can be used to provide protection.

[0079] The present application also provides a flow control method for the above transformer oil filling and discharge pipeline, which is implemented based on a single-input single-output model in the ARX model and specifically includes the following steps:

[0080] Step 1: Set the sampling period of the single-input single-output model h , with a sampling period h Collecting data samples ;in, is the opening signal value of the three-way ball valve, is the pipeline flow rate, N is the data sample length, t Indicates the length of the sampling period.

[0081] In this embodiment, the opening states of the three-way ball valve include closed, half-open, and fully open, and the corresponding opening signal values ​​are 0, 0.5, and 1. The pipeline flow is obtained through a sensor.

[0082] Step 2: Use the ARX model to identify data samples. The ARX model is as follows:

[0083] ;

[0084] In the formula, a 0. a i , b j are the model parameters to be estimated, n a , nb , k b is the structural parameter to be estimated, e ( t ) is zero-mean fixed white noise, is the structural parameter vector, is the model parameter vector;

[0085] in, ;

[0086] ;

[0087] .

[0088] The ARX model has a high-order ARX model, which can better approximate any linear time-invariant dynamic system. After determining the structural parameters, the linear least squares algorithm is used to estimate the ARX model parameters, which can simply and efficiently obtain the global optimal parameter estimation value. Therefore, the ARX model is used in this application to identify the pipeline flow change model. That is, the relationship between the oil flow and the valve opening is obtained through the ARX model.

[0089] Step 3: Use the least squares method to estimate the structural parameters in the ARX model. The estimation of the structural parameters is as follows:

[0090] ;

[0091] In the formula, , , , They are , n a , n b , k b The estimated value of is the degree of fit, and its expression is:

[0092] ;

[0093] In the formula, For Related The estimated value of for The average value of .

[0094] It should be noted that It is a representation and The degree of fit.

[0095] The expression is as follows:

[0096] ;

[0097] but: ;

[0098] In the formula, , They are a 0. b j The estimated value of .

[0099] Step 4: Estimate the model parameter vector value using the least squares method based on the structural parameters :

[0100] ;

[0101] In the formula, ; ;

[0102] and: ;

[0103] Then the transfer function of the ARX model is:

[0104] ;

[0105] It follows that:

[0106] .

[0107] The above two equations are the expressions of the discrete and continuous types of transfer functions.

[0108] Step 5: After reducing the order of the transfer function and performing continuous processing, the transfer function is obtained. The expression of this transfer function is as follows:

[0109] ;

[0110] The above transfer function is discretized and written as a difference equation:

[0111] Discretization: ;

[0112] Difference equation: ;

[0113] Step 6: According to the difference equation in step 5, the controller parameters of PID , , , is the decision variable, and the genetic algorithm is used to adjust , , ;

[0114] The minimum objective function using the absolute value time integral of the error as parameter selection in the genetic algorithm is:

[0115] ;

[0116] For the above objective function, a penalty factor is added to it to achieve the overshoot as the optimal indicator when an overshoot condition occurs. The objective function after adding the penalty factor is as follows:

[0117] ;

[0118] In the formula, is the system error, the value is less than 0, is the rise time, , , , is the weighted value, and .

[0119] In order to prevent the control amount from being too large, the input quantity in the above formula uses a square value.

[0120] In this embodiment, as shown in the attached Figure 3 As shown, the genetic operation selects the binary encoding method, and after decoding the individual code string, the individual phenotype can be obtained; the objective function value of the corresponding individual can be calculated from the phenotype; according to the type of optimal problem, the individual fitness can be calculated according to certain conversion rules using the objective function value.

[0121] Step 7: The host computer executes the first three-way ball valve and the second three-way ball valve according to the calculated values ​​of the PID controller parameters.

[0122] Input the parameters into the host computer. The PID controller is a program module that can calculate the corresponding valve opening according to the pipeline flow, send the command to the valve, and realize the valve action. Figure 2 As shown in the figure, PID control is a commonly used controller solution, which is mainly divided into three parts: proportional, integral and differential.

[0123] The PID controller is based on the input given value The actual output value The linear controller that constitutes the deviation can be expressed as: , and then perform proportional, integral and differential operations to control the controlled object. The expression is:

[0124] ;

[0125] The above formula is transformed into a transfer function:

[0126] ;

[0127] In the formula, is the proportionality constant, is the integration time constant, is the integration constant, is the differential time constant, is the differential constant, where , , Three constants need to be determined using genetic algorithms.

[0128] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A method for controlling the flow rate of oil filling and draining pipelines of a transformer, characterized in that: This method is implemented based on the transformer oil filling and discharge pipeline, which includes: An oil inlet, wherein the oil is supplied to the oil filter; An oil outlet, wherein the oil is supplied to flow out of the oil filter; An oil tank port, the oil tank port being in communication with the oil tank so as to allow oil to flow into and out of the oil tank; A transformer port, the transformer port being in communication with the interior of the transformer for allowing oil to flow into and out of the transformer; a first oil drain pipeline, the first oil drain pipeline being connected to the oil inlet and the transformer port respectively; a second oil discharge pipeline, the second oil discharge pipeline is respectively connected to the oil outlet and the oil storage tank port; a first oil filling pipeline, wherein the first oil filling pipeline is connected to the first oil discharge pipeline and the second oil discharge pipeline at a position close to the oil storage tank opening and the oil inlet, respectively, and forms a first three-way port with the second oil discharge pipeline at the connection position; a second oil injection pipeline, the second oil injection pipeline is connected to the second oil discharge pipeline and the first oil discharge pipeline at a position close to the oil outlet and the transformer port, respectively, and forms a second three-way port with the first oil discharge pipeline at the connection position; a first three-way ball valve, the first three-way ball valve is located at the first three-way port, and the first three-way ball valve is driven by a motor to actuate the ball valve; a second three-way ball valve, the second three-way ball valve is located at the second three-way port, and the second three-way ball valve is driven by a motor to actuate the ball valve; A sensor is arranged on the inner wall of the first oil discharge pipeline, and the sensor is used to collect oil flow data; A power supply, the power supply being used to supply power to the first three-way ball valve, the second three-way ball valve and the sensor; A lower computer, wherein the lower computer is provided with a serial port connected to an upper computer, and the upper computer has a built-in PID controller; This method is based on the single-input single-output model in the ARX model and specifically includes the following steps: Step 1: Set the sampling period of the single-input single-output model and collect data samples according to the sampling period; Step 2: Use the ARX model to identify data samples; Step 3: Use the least squares method to estimate the structural parameters in the ARX model; Step 4: Based on the structural parameters, use the least squares method to estimate the model parameter vector value: Step 5: Reduce the order of the transfer function of the ARX model and make it continuous; Step 6: PID controller parameters , , , is the decision variable, and the genetic algorithm is used to adjust , , ;in, is the proportionality constant, is the integration time constant, is the integration constant, is the differential constant; Step 7: The host computer executes the first three-way ball valve and the second three-way ball valve according to the calculated values ​​of the PID controller parameters.

2. A transformer oil filling and draining pipeline flow control method according to claim 1, characterized in that: The first oil discharge pipeline and the second oil discharge pipeline are both straight pipelines, the first oil injection pipeline and the second oil injection pipeline are both broken line pipelines, and the first oil injection pipeline and the second oil injection pipeline are in a leaping type at the intersection.

Images