Method for modeling photovoltaic power station for relay protection by using fault recording data

Abstract

The invention relates to a method for modeling a photovoltaic power station for relay protection by using fault recording data. The method comprises the following steps: step 1, acquiring a fault recording file by a fault recording analysis system; 2, processing voltage and current data based on the fault recording file obtained in the step 1, and then calculating the short-circuit current of the photovoltaic power station; 3, obtaining a latest short circuit calculation model based on the voltage and current data processed in the step 2, and obtaining a final short circuit calculation model through multiple times of model correction; and 4, performing short-circuit calculation by using the short-circuit calculation model corrected in the step 3. According to the invention, simulation and actual short-circuit tests can be avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of relay protection, and relates to a method for modeling a photovoltaic power station for relay protection, in particular to a method for modeling a photovoltaic power station for relay protection by using fault recording data. Background Art

[0002] The photovoltaic power station model for relay protection requires simulation of the photovoltaic power station or short-circuit test. Simulation requires a large number of technical parameters, which are difficult for engineers to obtain. On-site short-circuit tests require complex test equipment and have certain risks, which is not convenient for large-scale promotion and use.

[0003] Short-circuit calculation plays a vital role in relay protection setting. It provides accurate setting parameters for relay protection equipment by calculating the current and voltage distribution of the system under various short-circuit faults (such as three-phase, two-phase, and single-phase grounding faults). Through short-circuit calculation, engineers can determine the magnitude and direction of the fault current, so as to reasonably set the action value and action time of the relay protection, ensure that the protection device can act quickly and reliably when a fault occurs, and avoid false action during normal operation or slight fluctuations, so as to ensure the safety and stable operation of the power grid.

[0004] Fault recording is one of the necessary equipment in the substation of the power system. Fault recording data is currently only used in accident analysis scenarios, and the fault recording data of successful reclosing or correct relay protection action has not been fully utilized. Every short-circuit fault in the power grid can be regarded as a short-circuit experiment on the power station, and the experimental results are included in the recording file of the substation.

[0005] Therefore, the present invention proposes a method for modeling a photovoltaic power station for relay protection using fault recording data.

[0006] After searching, no public documents of the prior art that are identical or similar to the present invention were found. Summary of the invention

[0007] The purpose of the present invention is to overcome the deficiencies of the prior art and to propose a method for modeling a photovoltaic power station for relay protection using fault recording data, which can avoid simulation and actual short-circuit tests.

[0008] The present invention solves the practical problem by adopting the following technical solutions:

[0009] A method for modeling a photovoltaic power station for relay protection using fault recording data comprises the following steps:

[0010] Step 1: Obtain the fault recording file from the fault recording analysis system;

[0011] Step 2: Based on the fault recording file obtained in step 1, the voltage and current data are processed to calculate the short-circuit current of the photovoltaic power station;

[0012] Step 3: Based on the voltage and current data processed in step 2, the latest short-circuit calculation model is obtained, and the final short-circuit calculation model is obtained through multiple model corrections;

[0013] Step 4: Apply the short-circuit calculation model corrected in step 3 to perform short-circuit calculation.

[0014] Moreover, the specific method of step 1 is:

[0015] The fault recording and analysis system periodically reads the recording files stored on each fault recorder into the fault recording and analysis system through the dispatching communication network.

[0016] Moreover, the specific steps of step 2 include:

[0017] 2.1 Perform time column processing on voltage and current data;

[0018] 2.2 Process the voltage data;

[0019] 2.3 Processing of current data;

[0020] 2.4 Calculate the short-circuit current of the photovoltaic power station;

[0021] Moreover, the specific steps of step 2.1 include:

[0022] (1) Determine the mutation time:

[0023] The time when the mutation occurs in COMTRADE file A is recorded as ta0, and the time when the mutation occurs in COMTRADE file B is recorded as tb0.

[0024] (2) Align the determined mutation amount moments to obtain a new storage order.

[0025] Moreover, the specific method of step 2.2 is:

[0026] According to the sampling frequency, the effective value of the voltage Uarms of the fault interval in COMTRADE file A is calculated, and the effective value of the voltage Ubrms of the fault interval in COMTRADE file B is calculated.

[0027] Moreover, the specific method of step 2.3 is:

[0028] According to the sampling frequency, the effective value of the current Iarms of the fault interval in COMTRADE file A is calculated, and the Ubrms of the fault interval in COMTRADE file B is calculated.

[0029] Moreover, the specific method of step 2.4 is:

[0030] According to the power grid structure, Igrms = -Iarms - Ibrms; Ugrms = Uarm - Z*Iarms;

[0031] Where Z is the line impedance from the photovoltaic power station grid connection point to substation A;

[0032] Then we can get Pk = (Ugrms, Igrms) at each moment.

[0033] Wherein, Pk is the voltage and current data set of the kth fault photovoltaic power station.

[0034] Moreover, the specific steps of step 3 include:

[0035] 3.1 Generate the latest short-circuit calculation model;

[0036] 3.2 Correct the latest short-circuit calculation model;

[0037] Moreover, the specific steps of step 3.1 include:

[0038] (1) For a photovoltaic power station, there are two model records, denoted as P1 = (U11, I11 ... U1n, I1n), P2 = (U21, I21 ... U2n, I2n)

[0039] (2) Assume that the relationship between voltage and current when a power station is short-circuited is U = I^w; use the least squares method to find the w value with the smallest error and obtain the latest short-circuit calculation model.

[0040] Moreover, the specific method of step 3.2 is:

[0041] After a fault occurs, the voltage-current relationship Pn is obtained. By recording P1, P2, ... Pn, the new w is calculated using the least squares method to complete the model correction and output the result.

[0042] Moreover, the specific method of step 4 is:

[0043] Through the above steps, the relationship between voltage and current when the photovoltaic power station is short-circuited is obtained, which can be input into the short-circuit calculation software for application.

[0044] Advantages and beneficial effects of the present invention:

[0045] 1. The present invention proposes a method for modeling a photovoltaic power station for relay protection using fault recording data. By analyzing and calculating the fault recording data of different substations for the same fault, the fault current curve of the photovoltaic power station under different fault voltages is obtained; by using the centralized processing technology of the fault recording system data in the substation, the recording data is aligned, and the fault short-circuit current and voltage are obtained by calculation. The present invention utilizes the existing fault recording data, avoids tedious on-site testing and simulation, can quickly and effectively obtain the fault current characteristics of the photovoltaic power station, reduces the complexity and time cost of calculation, and ensures the accuracy and pertinence of the data.

[0046] 2. The present invention uses the least squares technique to fit a model curve with the minimum error from multiple fault data. When a new fault occurs, the model is updated with the new data. The least squares method is used to fit multiple fault data, which can effectively reduce errors and improve the accuracy of the model. At the same time, the model can be dynamically updated with new fault data, ensuring the timeliness and adaptability of the model and enhancing the ability to predict future faults.

[0047] 3. The present invention utilizes the fault recording data in the power system, and obtains the branch current of the photovoltaic power station by calculating the associated branch current of the substation. Since the characteristics of each fault are different, the present invention takes the average value of the results of multiple faults through least squares to ensure the accuracy of the calculation. The method of the present invention is used to calculate the short-circuit current of the photovoltaic power station, avoiding simulation and actual short-circuit tests. The workload is greatly reduced and the availability of the photovoltaic power station model for relay protection is improved. The present invention avoids complex simulation processes and high-risk short-circuit tests through associated current calculations, reducing experimental costs and safety hazards. At the same time, the average value of multiple fault results is used to improve the calculation accuracy, ensure the reliability of the model, and greatly improve the practical application value of the model and the effectiveness of relay protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a schematic diagram of the working principle of the present invention;

[0049] Figure 2 It is a short-circuit model calculation flow chart of the present invention;

[0050] Figure 3 It is a schematic diagram of the time column processing principle of the present invention. DETAILED DESCRIPTION

[0051] The following further describes the embodiments of the present invention:

[0052] A method for modeling a photovoltaic power station for relay protection using power system fault recording data, such as Figure 1 and Figure 2 As shown, the following steps are included:

[0053] Step 1: Obtain the fault recording file from the fault recording analysis system;

[0054] The specific method of step 1 is:

[0055] The fault recording and analysis system periodically reads the recording files stored on each fault recorder into the fault recording and analysis system through the dispatching communication network.

[0056] In this embodiment, when a short circuit fault occurs, the fault recorders installed in substation A and substation B automatically start recording voltage and current data, and save the data in the form of COMTRADE files on the hard disks of the fault recorders.

[0057] The fault recording and analysis system periodically reads the recording files stored on each fault recorder into the fault recording and analysis system through the dispatching communication network.

[0058] Step 2: Based on the fault recording file obtained in step 1, the voltage and current data are processed to calculate the short-circuit current of the photovoltaic power station;

[0059] The specific steps of step 2 include:

[0060] 2.1 Perform time column processing on voltage and current data;

[0061] like Figure 3 As shown, the specific steps of step 2.1 include:

[0062] (1) Determine the mutation time:

[0063] The time when the mutation occurs in COMTRADE file A is recorded as ta0, and the time when the mutation occurs in COMTRADE file B is recorded as tb0.

[0064] In this embodiment, due to a fault in the power grid, a sudden change is inevitable in a certain channel of the fault recording; the time when the sudden change occurs in COMTRADE file A is recorded as ta0, and the time when the sudden change occurs in COMTRADE file B is recorded as tb0.

[0065] (2) Align the determined mutation amount moments to obtain a new storage order;

[0066] Since the sampling frequencies of the fault recorders are the same, the new storage order is shown in the following table:

[0067] New time column COMTRADE File A COMTRADE File B File A data...... File B data...... N-1 N-1 N-1 xx.xxx xx.xxx t0 ta0 tb0 xx.xxx xx.xxx N+1 N+1 N+1 xx.xxx xx.xxx ...... ...... ......

[0068] 2.2 Process the voltage data;

[0069] The specific method of step 2.2 is:

[0070] According to the sampling frequency, the effective value of the voltage Uarms of the fault interval in COMTRADE file A is calculated, and the effective value of the voltage Ubrms of the fault interval in COMTRADE file B is calculated.

[0071] 2.3 Processing of current data;

[0072] The specific method of step 2.3 is:

[0073] According to the sampling frequency, the effective value of the current Iarms of the fault interval in COMTRADE file A is calculated, and the effective value of the current Ibrms of the fault interval in COMTRADE file B is calculated.

[0074] 2.4 Calculate the short-circuit current of the photovoltaic power station;

[0075] The specific method of step 2.4 is:

[0076] According to the power grid structure, Igrms = -Iarms - Ibrms; Ugrms = Uarm - Z*Iarms;

[0077] Where Z is the line impedance from the photovoltaic power station grid connection point to substation A;

[0078] Then we can get Pk = (Ugrms, Igrms) at each moment.

[0079] Wherein, Pk is the voltage and current data set of the kth fault photovoltaic power station.

[0080] Step 3: Based on the voltage and current data processed in step 2, the latest short-circuit calculation model is obtained, and the final short-circuit calculation model is obtained through multiple model corrections;

[0081] like Figure 1 As shown, the specific steps of step 3 include:

[0082] 3.1 Generate the latest short-circuit calculation model;

[0083] The specific steps of step 3.1 include:

[0084] (3) For the sake of simplicity, a photovoltaic power station has two model records, which are recorded as P1 = (U11, I11 ... U1n, I1n) and P2 = (U21, I21 ... U2n, I2n)

[0085] (4) Assume that the relationship between voltage and current when a power station is short-circuited is U = I^w; use the least squares method to find the w value with the smallest error and obtain the latest short-circuit calculation model.

[0086] 3.2 Correct the latest short-circuit calculation model;

[0087] The specific method of step 3.2 is:

[0088] After a fault occurs, the voltage-current relationship Pn is obtained. By recording P1, P2, ... Pn, the new w is calculated using the least squares method to complete the model correction and output the result.

[0089] Step 4, applying the short-circuit calculation model corrected in step 3 to perform short-circuit calculation;

[0090] The specific method of step 4 is:

[0091] Through the above steps, the relationship between voltage and current when the photovoltaic power station is short-circuited is obtained, which can be input into the short-circuit calculation software for application.

[0092] The working principle of the present invention is:

[0093] Although GB / T32836-2016 provides a photovoltaic power station short-circuit calculation model, which can be used for relay protection setting calculation in theory, it is difficult to apply in practice because the model parameters can only be obtained by short-circuit testing the photovoltaic power station or the manufacturer needs to provide detailed device parameters. The present invention proposes a method for calculating the model parameters of a photovoltaic power station by using the recorded wave data after a fault in the power system near the photovoltaic power station, aiming at the photovoltaic power station model recommended in the State Grid Corporation of China enterprise standard "Energy Station Modeling for Relay Protection Setting Calculation".

[0094] Since the construction standards of photovoltaic power stations are not unified, some photovoltaic power stations do not install fault recording systems, so it is impossible to obtain the relationship between the grid connection point voltage and fault current during a short circuit fault. The present invention proposes a method for using the fault recording data in the power system around the new energy power station to derive a short circuit calculation model for the new energy power station.

[0095] It should be emphasized that the embodiments of the present invention are illustrative rather than restrictive. Therefore, the present invention includes but is not limited to the embodiments described in the specific implementation modes. Any other implementation modes derived by those skilled in the art based on the technical solutions of the present invention also fall within the scope of protection of the present invention.

Claims

1. A method for modeling a photovoltaic power station for relay protection using fault recording data, characterized in that: The following steps are involved: Step 1: Obtain the fault recording file from the fault recording analysis system; Step 2: Based on the fault recording file obtained in step 1, the voltage and current data are processed to calculate the short-circuit current of the photovoltaic power station; Step 3: Based on the voltage and current data processed in step 2, the latest short-circuit calculation model is obtained, and the final short-circuit calculation model is obtained through multiple model corrections; Step 4: Apply the short-circuit calculation model corrected in step 3 to perform short-circuit calculation.

2. A method for modeling a photovoltaic power station for relay protection using fault recording data according to claim 1, characterized in that: The specific method of step 1 is: The fault recording and analysis system periodically reads the recording files stored on each fault recorder into the fault recording and analysis system through the dispatching communication network.

3. The method for modeling a photovoltaic power station for relay protection using fault recording data according to claim 1, characterized in that: The specific steps of step 2 include: 2.1 Perform time column processing on voltage and current data; 2.2 Process the voltage data; 2.3 Processing of current data; 2.4 Calculate the short-circuit current of the photovoltaic power station.

4. The method for modeling a photovoltaic power station for relay protection using fault recording data according to claim 3, characterized in that: The specific steps of step 2.1 include: (1) Determine the mutation time: The time when the mutation occurs in COMTRADE file A is recorded as ta0, and the time when the mutation occurs in COMTRADE file B is recorded as tb0; (2) Align the determined mutation amount moments to obtain a new storage order.

5. The method for modeling a photovoltaic power station for relay protection using fault recording data according to claim 3, characterized in that: The specific method of step 2.2 is: According to the sampling frequency, the effective value of the voltage Uarms of the fault interval in COMTRADE file A is calculated, and the effective value of the voltage Ubrms of the fault interval in COMTRADE file B is calculated.

6. The method for modeling a photovoltaic power station for relay protection using fault recording data according to claim 3, characterized in that: The specific method of step 2.3 is: According to the sampling frequency, the effective value of the current Iarms of the fault interval in COMTRADE file A is calculated, and the Ubrms of the fault interval in COMTRADE file B is calculated.

7. The method for modeling a photovoltaic power station for relay protection using fault recording data according to claim 3, characterized in that: The specific method of step 2.4 is: According to the power grid structure, Igrms = -Iarms - Ibrms; Ugrms = Uarm - Z*Iarms; Where Z is the line impedance from the photovoltaic power station grid connection point to substation A; Then we can get Pk = (Ugrms, Igrms) at each moment. Wherein, Pk is the voltage and current data set of the kth fault photovoltaic power station.

8. The method for modeling a photovoltaic power station for relay protection using fault recording data according to claim 1, characterized in that: The specific steps of step 3 include: 3.1 Generate the latest short-circuit calculation model; 3.2 Modify the latest short-circuit calculation model.

9. A method for modeling a photovoltaic power station for relay protection using fault recording data according to claim 8, characterized in that: The specific steps of step 3.1 include: (1) A photovoltaic power station has two model records, denoted as P1 = (U11, I11 ... U1n, I1n), P2 = (U21, I21 ... U2n, I2n); (2) Assume that the relationship between voltage and current when a power station is short-circuited is U = I^w; use the least squares method to find the w value with the smallest error and obtain the latest short-circuit calculation model.

10. The method for modeling a photovoltaic power station for relay protection using fault recording data according to claim 8, characterized in that: The specific method of step 3.2 is: After a fault occurs, the voltage-current relationship Pn is obtained. By recording P1, P2, ... Pn, the new w is calculated using the least squares method to complete the model correction and output the result.

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