A new energy mathematical model processing method suitable for online checking application

Abstract

The present application relates to a kind of new energy mathematical model processing method suitable for online checking application, belong to the technical field of relay protection method.The technical scheme of the present application is: operating grid-connected point voltage under normal mode;Calculate the grid-connected point voltage under new energy injection short-circuit current;When positive sequence voltage continues to drop in threshold interval, set boundary variation, determine that grid-connected point voltage falls into threshold interval, operate grid-connected point voltage, when the difference between the results of two operations does not exceed boundary variation, no longer iteration, with the last operation result as final result;When positive sequence voltage interval drop threshold interval, set boundary variation, operate grid-connected point voltage, with the operation result in threshold interval as effective data for comparison.The beneficial effects of the present application are: when the calculated value does not fall into reasonable interval, by setting the boundary condition of iterative operation, ensure that the application software will not enter dead loop when calculating, and relatively reasonable result is calculated.

Description

Technical Field

[0001] This invention relates to a method for processing mathematical models of new energy sources suitable for online verification applications, belonging to the technical field of relay protection methods. Background Technology

[0002] In recent years, with increasing attention to the sustainability and environmental friendliness of energy utilization, new energy sources, as abundant, clean, safe, and reliable renewable energy sources, have been increasingly used in power grids. Currently, more than 20 provinces in my country have conducted surveys and studies on the regulation and grid connection of photovoltaic and wind power systems, and the National Energy Administration predicts that new energy will become the primary component of my country's power supply by 2050. Therefore, the rapid development of new energy power generation will make it an important support and supplement to the future power system.

[0003] However, due to their power supply characteristics, the integration of new energy systems has made the original top-down medium and low-voltage distribution network structure more complex. It is no longer primarily a single-source radial system, but exhibits the steady-state and fault characteristics of multiple power sources. Simultaneously, the fault characteristics of distributed new energy systems are severely affected by their internal control systems and structures, and they exhibit short transient response times and significant nonlinear characteristics. Both of these reasons cause traditional top-down fault protection methods to face serious adaptability problems. Traditional protection systems configured according to the radial power supply structure will experience malfunctions and failures to operate, thus seriously threatening the safe and stable operation of distribution networks containing distributed new energy sources.

[0004] In 2022, the State Grid Corporation of China released the enterprise standard "Modeling Guidelines for New Energy Power Stations for Relay Protection Setting Calculation" Q / GDW 12207—2022. Based on this standard, various power grid companies have successively developed new energy power station models using relay protection setting calculation related business software. Among them, the most widely used algorithm is to treat new energy as equivalent to a voltage-controlled current source and process iterative algorithms based on collected parameters. However, when the collected parameters are inaccurate due to differences in experimental environment, the fault calculation iteration cannot converge, and thus cannot achieve the expected results. Summary of the Invention

[0005] The purpose of this invention is to provide a new energy mathematical model processing method suitable for online verification applications. When the calculated value does not fall within a reasonable range, by setting boundary conditions for iterative calculations, it ensures that the application software will not enter an infinite loop during calculation and calculates a relatively reasonable result, effectively solving the above-mentioned problems existing in the background technology.

[0006] The technical solution of this invention is: a method for processing new energy mathematical models suitable for online verification applications, comprising the following steps: (1) Voltage at the grid connection point under normal operating conditions; (2) Calculate the grid connection point voltage under the short-circuit current injected by the new energy source; (3) When the positive sequence voltage continuously falls into the threshold range, set the boundary change amount to determine that the grid connection point voltage falls into the threshold range, and perform calculations on the grid connection point voltage. When the difference between the results of the two calculations does not exceed the boundary change amount, no further iteration is performed, and the last calculation result is taken as the final result. (4) When the positive sequence voltage drops below the threshold range, a boundary change amount is set, and the grid connection point voltage is calculated. The calculation result falling within the threshold range is used as the valid data for comparison. When the difference between the two calculation results of the grid connection point voltage does not exceed the boundary change amount, no further iteration is performed, and the last calculation result is used as the final result.

[0007] The threshold range is defined as the grid connection point voltage being between 0.8 and 0.9 pu.

[0008] The boundary change is 5%.

[0009] In step (4), the calculation is iterated at least 10 times, and the calculation results that fall into the threshold interval are recorded.

[0010] The beneficial effect of this invention is that when the calculated value does not fall within a reasonable range, by setting the boundary conditions of the iterative operation, it ensures that the application software will not enter an infinite loop during the calculation and calculates a relatively reasonable result. Attached Figure Description

[0011] Figure 1 This is a flowchart illustrating the process of the positive sequence voltage continuously falling within the threshold range according to the present invention. Figure 2 This is a flowchart illustrating the process when the positive sequence voltage interval falls within the threshold range according to the present invention. Detailed Implementation

[0012] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments, which are preferred embodiments of the present invention. It should be understood that the described embodiments are merely some embodiments of the present invention, and not all embodiments; it should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0013] A method for processing new energy mathematical models suitable for online verification applications includes the following steps: (1) Voltage at the grid connection point under normal operating conditions; (2) Calculate the grid connection point voltage under the short-circuit current injected by the new energy source; (3) When the positive sequence voltage continuously falls into the threshold range, set the boundary change amount to determine that the grid connection point voltage falls into the threshold range, and perform calculations on the grid connection point voltage. When the difference between the results of the two calculations does not exceed the boundary change amount, no further iteration is performed, and the last calculation result is taken as the final result. (4) When the positive sequence voltage drops below the threshold range, a boundary change amount is set, and the grid connection point voltage is calculated. The calculation result falling within the threshold range is used as the valid data for comparison. When the difference between the two calculation results of the grid connection point voltage does not exceed the boundary change amount, no further iteration is performed, and the last calculation result is used as the final result.

[0014] The threshold range is defined as the grid connection point voltage being between 0.8 and 0.9 pu.

[0015] The boundary change is 5%.

[0016] In step (4), the calculation is iterated at least 10 times, and the calculation results that fall into the threshold interval are recorded.

[0017] In practical applications: 1. The positive sequence voltage drop threshold consistently falls between 0.8 and 0.9.

[0018] According to the low voltage ride-through requirements for photovoltaic / wind power generation / wind farms in the standard GB / T 19964, when the grid connection point voltage is higher than 0.9 pu, the photovoltaic / wind power generation / wind turbine maintains normal operation and does not provide short-circuit current. When the grid connection point voltage is lower than 0.2 pu, the photovoltaic / wind power generation / wind turbine disconnects from the grid, that is, the output current is zero.

[0019] First, under normal operating conditions, the grid connection point voltage can be calculated by referring to "Power System Analysis". Then, the short-circuit current provided by the new energy source at this moment is calculated according to "Modeling Guidelines for New Energy Power Plants for Relay Protection Setting Calculation" (Q / GDW 12207—2022). After the new energy short-circuit current is injected, the grid reconfiguration recalculates the grid connection point voltage. This process is repeated until the grid connection point voltage no longer changes, thus completing this calculation.

[0020] However, there are two problems: (1) The number of iterations cannot be estimated, resulting in excessive computation; (2) Since it is computer operation, the differences between data will not be absolutely equal after a finite number of operations, which makes it impossible to control the number of iterations.

[0021] Therefore, this invention proposes a boundary condition: when the difference between the two calculation results of the grid connection point voltage does not exceed 5%, the iteration will stop and the result of the last calculation will be taken as the final result.

[0022] The process is explained as follows: 1) Start, initiate the process; 2) Referring to "Power System Analysis", the voltage at the grid connection point of new energy sources under normal conditions can be calculated; 3) Calculate the grid connection point voltage under the short-circuit current injected by the new energy source; 4) Determine whether the voltage at the grid connection point falls within the drop threshold range of 0.8-0.9. If yes, proceed to the next step; otherwise, exit the calculation loop. 5) After each iteration, compare the calculation result with the previous result and determine if the absolute value of the difference is within 5% of the boundary change. If yes, proceed to the next step; otherwise, proceed to the loop calculation. 6) After the conditions are met, output the result of the last calculation; 7) The process ends.

[0023] 2. The positive sequence voltage drop threshold interval falls between 0.8 and 0.9.

[0024] According to the low voltage ride-through requirements for photovoltaic / wind power generation / wind farms in the standard GB / T 19964, when the grid connection point voltage is higher than 0.9 pu, the photovoltaic / wind power generation / wind turbine maintains normal operation and does not provide short-circuit current. When the grid connection point voltage is lower than 0.2 pu, the photovoltaic / wind power generation / wind turbine disconnects from the grid, that is, the output current is zero.

[0025] First, under normal operating conditions, the grid connection point voltage can be calculated by referring to "Power System Analysis". Then, the short-circuit current provided by the new energy source at this moment is calculated according to "Modeling Guidelines for New Energy Power Plants for Relay Protection Setting Calculation" (Q / GDW 12207—2022). After the new energy short-circuit current is injected, the grid reconfiguration recalculates the grid connection point voltage. This process is repeated until the grid connection point voltage no longer changes, thus completing this calculation.

[0026] We will analyze two scenarios: (1) Except for the first calculation where the grid connection point voltage falls within the range, all other calculations are not within the threshold. In this case, the first calculation is used as the basis for outputting the calculation result.

[0027] (2) The first calculation of the grid connection point voltage falls within the range. The second calculation result is not within the threshold. The third calculation result falls within the threshold range. At this time, the calculation result that falls within the threshold range is used as the valid data for comparison. When the difference between the two calculation results of the grid connection point voltage does not exceed 5%, the iteration is stopped and the last calculation result is used as the final result.

[0028] The process is explained as follows: 1) Start, initiate the process; 2) Referring to "Power System Analysis", the voltage at the grid connection point of new energy sources under normal conditions can be calculated; 3) Calculate the grid connection point voltage under the short-circuit current injected by the new energy source; 4) Determine whether the voltage at the grid connection point falls within the drop threshold range of 0.8-0.9. If yes, proceed to the next step; otherwise, exit the calculation loop and output the calculation result that falls within the range. 5) Perform iterative calculations, considering the possibility of jumping out of the calculation loop due to conflicts with the "flowchart of satisfying the voltage drop interval of the grid connection point". Refer to at least 10 iterations and record the calculation results that fall into the interval. 6) Determine if multiple operations fall within an interval and if the difference between the results of two consecutive operations is within 5% of the boundary change. 7) Output the result of the last calculation as the final result; 8) End, process complete.

Claims

1. A method for processing new energy mathematical models suitable for online verification applications, characterized in that... Includes the following steps: (1) Positive sequence voltage at the grid connection point under normal operating conditions; (2) Calculate the positive sequence voltage at the grid connection point under the short-circuit current injected by the new energy source; (3) When the positive sequence voltage continuously falls into the threshold range, set the boundary change amount to determine that the positive sequence voltage of the grid connection point falls into the threshold range, calculate the positive sequence voltage of the grid connection point, and when the difference between the two calculation results does not exceed the boundary change amount, stop iterating and take the last calculation result as the final result. (4) When the positive sequence voltage drops below the threshold range, a boundary change amount is set, and the positive sequence voltage at the grid connection point is calculated. The calculation result falling within the threshold range is used as the valid data for comparison. When the difference between the two calculation results of the positive sequence voltage at the grid connection point does not exceed the boundary change amount, no further iteration is performed, and the last calculation result is used as the final result.

2. The method for processing new energy mathematical models suitable for online verification applications according to claim 1, characterized in that: The threshold range is defined as the positive sequence voltage at the grid connection point being between 0.8 and 0.9 pu.

3. A method for processing new energy mathematical models suitable for online verification applications according to claim 1 or 2, characterized in that: The boundary change is 5%.

4. A method for processing new energy mathematical models suitable for online verification applications according to claim 1 or 2, characterized in that: In step (4), the calculation is iterated at least 10 times, and the calculation results that fall into the threshold interval are recorded.

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