A network-constructing type new energy flow iteration transient voltage evaluation method and system

Abstract

The application discloses a kind of based on network type new energy flow iteration transient voltage evaluation method, it is related to electric power system field, method includes: build PSCAD high voltage direct current transmission system, simulate commutation failure fault;Determine the direct current node in new energy network type system, introduce reactive power disturbance at direct current node;First flow calculation is carried out to entire new energy network type system, and the voltage variation of network type node is obtained;Based on the voltage variation of network type node, the reactive power injection of new network type node is calculated, and direct current node is injected again;Carry out flow calculation, judge whether flow converges;Whether the error size meets the demand is judged, and transient voltage evaluation result is obtained;The application is not only suitable for the case of single network type new energy access system, but also suitable for the case of multiple network type new energy access system, effectively avoid the complexity of modeling required for transient overvoltage evaluation of multiple network type new energy system.

Description

Technical Field

[0001] This invention relates to the field of power systems, and in particular to a method and system for evaluating transient voltage based on power flow iteration of grid-connected new energy sources. Background Technology

[0002] With the continuous integration of large-scale new energy sources and the deployment of high-capacity DC transmission, the overall inertia of the system has significantly decreased. Related research has proposed integrating grid-connected new energy sources to improve system inertia; however, there is a lack of research on methods for assessing transient overvoltages after the integration of grid-connected new energy sources. The traditional Newton-Raphson power flow iteration method is suitable for systems without grid-connected new energy nodes, but it is not applicable to the future trend of high new energy penetration. Summary of the Invention

[0003] In view of the above-mentioned problems, the present invention is proposed.

[0004] Therefore, the technical problem solved by this invention is: how to evaluate the transient overvoltage that occurs in the system after grid-connected new energy sources are connected.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] In a first aspect, embodiments of the present invention provide a method for evaluating transient voltage based on power flow iteration of a grid-connected renewable energy source, including:

[0007] Build a PSCAD high-voltage DC transmission system and simulate commutation failure faults;

[0008] Identify the DC nodes in the new energy grid system and introduce reactive power disturbances at the DC nodes;

[0009] The first power flow calculation was performed on the entire new energy grid system to obtain the voltage change of the grid nodes;

[0010] Based on the voltage change of the network node, the reactive power injection of the new network node is calculated and injected into the DC node again.

[0011] Perform power flow calculations to determine whether the power flow has converged;

[0012] Determine whether the error magnitude meets the requirements to obtain the transient voltage evaluation result.

[0013] As a preferred scheme for evaluating transient voltage based on power flow iteration of grid-type new energy sources, the following is provided:

[0014] The construction of the PSCAD high-voltage DC transmission system, simulating commutation failure faults, includes:

[0015] Set up DC nodes in the power transmission system and set a grounding resistance of 100ms at the DC nodes. Record the highest value of transient voltage at each node during the transient process. Ensure that the PSCAD model can maintain stable operation during the set simulation time before simulating commutation failure.

[0016] As a preferred scheme for evaluating transient voltage based on power flow iteration of grid-type new energy sources, the following is provided:

[0017] The process of determining the DC nodes in the new energy grid system and introducing reactive power disturbances at the DC nodes includes:

[0018] Select a simulation model, convert the simulation model into Matpower data format, and locate the DC node by matching the node positions one by one. Simulate the commutation failure fault to determine the reactive power disturbance at the DC node. Use the obtained reactive power disturbance as the initial reactive power disturbance to introduce into the DC node in the program.

[0019] As a preferred scheme for evaluating transient voltage based on power flow iteration of grid-type new energy sources, the following is provided:

[0020] The calculation of the reactive power injection of the new grid-type node based on the voltage change of the grid-type node includes:

[0021] The voltage change ΔU of the network node 0 After the droop control equation:

[0022] ΔQ n =K*ΔU n

[0023] Where, ΔQ n This represents the reactive power injection amount of the new network node, and K represents the reactive power droop coefficient of the network node.

[0024] The reactive power injection of the new network node is obtained by calculating the droop control equation.

[0025] As a preferred scheme for evaluating transient voltage based on power flow iteration of grid-type new energy sources, the following is provided:

[0026] The process of performing power flow calculations and determining whether the power flow has converged includes:

[0027] Perform power flow calculations to determine if the power flow has converged. If it has converged, perform error calculations. If it has not converged, stop the program and re-simulate the commutation failure fault. Reduce reactive power disturbance at the DC node by resetting the grounding impedance.

[0028] As a preferred scheme for evaluating transient voltage based on power flow iteration of grid-type new energy sources, the following is provided:

[0029] The error calculation includes:

[0030] The expression for error calculation is:

[0031] ΔU n =||U n -U n-1 ||

[0032] Wherein, ΔU n U represents the voltage change between the nth and (n-1)th iterations. n This represents the voltage value during the nth power flow iteration.

[0033] As a preferred scheme for evaluating transient voltage based on power flow iteration of grid-type new energy sources, the following is provided:

[0034] The determination of whether the magnitude of the error meets the requirements, and the resulting transient voltage assessment, include:

[0035] Determine if the error magnitude meets the requirements. If it does, output the final power flow result. If it does not, check if the number of iterations has reached the set maximum value. If the number of iterations has not reached the maximum value, modify the reactive power droop coefficient K of the network node. If the number of iterations has reached the maximum value, increase the set number of iterations until the error requirement is met.

[0036] Secondly, embodiments of the present invention provide a transient voltage assessment system based on power flow iteration of a grid-type new energy source, comprising:

[0037] The simulation module is used to build a PSCAD high-voltage DC transmission system and simulate commutation failure faults.

[0038] The preprocessing module is used to determine the DC nodes in the new energy grid system and introduce reactive power disturbances at the DC nodes.

[0039] The injection module is used to perform power flow calculations on the entire new energy grid-type system to obtain the voltage change of the grid-type nodes; based on the voltage change of the grid-type nodes, it calculates the reactive power injection amount of the new grid-type nodes and injects it into the DC nodes.

[0040] The power flow calculation module is used to perform power flow calculations and determine whether the power flow has converged.

[0041] The judgment module is used to determine whether the error magnitude meets the requirements and obtain the transient voltage evaluation result.

[0042] Thirdly, embodiments of the present invention provide a computing device, including:

[0043] Memory and processor;

[0044] The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the one or more programs are executed by the one or more processors, the one or more processors implement the method for evaluating transient voltage based on grid-type new energy power flow iteration as described in any embodiment of the present invention.

[0045] Fourthly, embodiments of the present invention provide a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the aforementioned method for evaluating transient voltage based on grid-type new energy power flow iteration.

[0046] The beneficial effects of this invention are as follows: Based on the traditional Newtonian power flow iteration method, this invention considers the droop control characteristics of grid-type renewable energy nodes and successfully achieves effective evaluation of the commutator bus voltage after commutation failure in renewable energy grid-type systems. This avoids the problem that the traditional Newtonian power flow iteration method is not applicable to power flow problems in renewable energy systems containing grid-type renewable energy. At the same time, this invention is applicable not only to the case of a single grid-type renewable energy access system, but also to the case of multiple grid-type renewable energy access systems, effectively avoiding the complexity of modeling required for transient overvoltage evaluation in multi-grid-type renewable energy systems. Attached Figure Description

[0047] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0048] Figure 1 This is an overall flowchart of the method for evaluating transient voltage based on power flow iteration of grid-type new energy sources as described in the first embodiment of the present invention;

[0049] Figure 2 This is a simulation example of a 37-node system structure diagram in the second embodiment of the present invention based on the iterative transient voltage evaluation method of grid-type new energy power flow.

[0050] Figure 3 This is a comparison diagram of transient overvoltage assessment errors when node 34 fails to commutate after being connected to the grid-type new energy source in a simulation example of the transient voltage assessment method based on the power flow iteration of the grid-type new energy source described in the second embodiment of the present invention.

[0051] Figure 4 This is a comparison diagram of transient overvoltage assessment errors when node 36 fails to commutate after being connected to the grid-type new energy source in a simulation example of the transient voltage assessment method based on the power flow iteration of grid-type new energy source described in the second embodiment of the present invention.

[0052] Figure 5 This is a comparison diagram of transient overvoltage assessment errors when nodes 34 and 36 fail to commutate after being connected to the grid-type new energy source in a simulation example of the transient voltage assessment method based on the power flow iteration of grid-type new energy source described in the second embodiment of the present invention. Detailed Implementation

[0053] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0054] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0055] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0056] This invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of this invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not be construed as limiting the scope of protection of this invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0057] Furthermore, in the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used solely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In addition, the terms "first," "second," or "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0058] Unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" in this invention should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integrated connections; similarly, they can refer to mechanical connections, electrical connections, or direct connections, or indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0059] Example 1

[0060] Reference Figure 1 This is the first embodiment of the present invention, which provides a method for evaluating transient voltage based on power flow iteration of grid-type new energy sources, including:

[0061] S1: Build a PSCAD high-voltage DC transmission system and simulate commutation failure;

[0062] Specifically, the construction of the PSCAD high-voltage direct current transmission system to simulate commutation failure faults includes:

[0063] Set up DC nodes in the power transmission system and set a grounding resistance of 100ms at the DC nodes. Record the highest value of transient voltage at each node during the transient process. Ensure that the PSCAD model can maintain stable operation during the set simulation time before simulating commutation failure.

[0064] S2: Determine the DC nodes in the new energy grid system and introduce reactive power disturbances at the DC nodes;

[0065] Specifically, determining the DC nodes in the new energy grid system and introducing reactive power disturbances at the DC nodes includes:

[0066] Select a simulation model, convert the simulation model into Matpower data format, and locate the DC node by matching the node positions one by one. Simulate the commutation failure fault to determine the reactive power disturbance at the DC node. Use the obtained reactive power disturbance as the initial reactive power disturbance to introduce into the DC node in the program.

[0067] S3: Perform the first power flow calculation on the entire new energy grid system to obtain the voltage change of the grid nodes; based on the voltage change of the grid nodes, calculate the reactive power injection of the new grid nodes and inject it into the DC nodes again.

[0068] Specifically, calculating the reactive power injection of the new grid-type node based on the voltage change of the grid-type node includes:

[0069] The voltage change ΔU of the network node 0 After the droop control equation:

[0070] ΔQ n =K*ΔU n

[0071] Where, ΔQ n This represents the reactive power injection amount of the new network node, and K represents the reactive power droop coefficient of the network node.

[0072] The reactive power injection of the new network node is obtained by calculating the droop control equation.

[0073] S4: Perform power flow calculations and determine whether the power flow converges;

[0074] Specifically, the process of performing power flow calculations and determining whether the power flow has converged includes:

[0075] Perform power flow calculations to determine if the power flow has converged. If it has converged, perform error calculations. If it has not converged, stop the program and re-simulate the commutation failure fault. Reduce reactive power disturbance at the DC node by resetting the grounding impedance.

[0076] Furthermore, the error calculation includes:

[0077] The expression for error calculation is:

[0078] ΔU n =||U n -U n-1 ||

[0079] Wherein, ΔU n U represents the voltage change between the nth and (n-1)th iterations. n This represents the voltage value during the nth power flow iteration.

[0080] S5: Determine whether the error magnitude meets the requirements and obtain the transient voltage evaluation result.

[0081] Specifically, determining whether the magnitude of the error meets the requirements to obtain the transient voltage evaluation result includes:

[0082] Determine if the error magnitude meets the requirements. If it does, output the final power flow result. If it does not, check if the number of iterations has reached the set maximum value. If the number of iterations has not reached the maximum value, modify the reactive power droop coefficient K of the network node. If the number of iterations has reached the maximum value, increase the set number of iterations until the error requirement is met.

[0083] It should be noted that the method of this invention first introduces the same reactive power disturbance as the simulation model to perform a power flow calculation to obtain the voltage change of the grid-type nodes. Then, the voltage change of the grid-type nodes in the first calculation is applied to the droop control equation to calculate the reactive power disturbance of the DC nodes in the second calculation. Given the voltage and reactive power droop control characteristics of grid-type renewable energy sources, which have voltage and reactive power regulation capabilities, the reactive power disturbance obtained in the second calculation is smaller than the initially introduced reactive power disturbance. Therefore, each time a power flow calculation is performed and the droop control equation is applied, the new reactive power disturbance obtained is always smaller than the previous one. Thus, the voltage change obtained through iterative calculation becomes smaller and smaller. When the voltage change meets the set error requirements, the power flow results are output, the voltage values ​​of each node are extracted, and the transient voltage assessment is finally completed.

[0084] The above is a schematic scheme of the transient voltage assessment method based on the iterative power flow of grid-type renewable energy in this embodiment. It should be noted that the technical solution of the transient voltage assessment system based on the iterative power flow of grid-type renewable energy and the technical solution of the aforementioned transient voltage assessment method based on the iterative power flow of grid-type renewable energy belong to the same concept. Details not described in detail in the technical solution of the iterative voltage assessment system based on the iterative power flow of grid-type renewable energy in this embodiment can be found in the description of the technical solution of the aforementioned transient voltage assessment method based on the iterative power flow of grid-type renewable energy.

[0085] This embodiment is based on a grid-type renewable energy power flow iterative transient voltage assessment system, including:

[0086] The simulation module is used to build a PSCAD high-voltage DC transmission system and simulate commutation failure faults.

[0087] The preprocessing module is used to determine the DC nodes in the new energy grid system and introduce reactive power disturbances at the DC nodes.

[0088] The injection module is used to perform power flow calculations on the entire new energy grid-type system to obtain the voltage change of the grid-type nodes; based on the voltage change of the grid-type nodes, it calculates the reactive power injection amount of the new grid-type nodes and injects it into the DC nodes.

[0089] The power flow calculation module is used to perform power flow calculations and determine whether the power flow has converged.

[0090] The judgment module is used to determine whether the error magnitude meets the requirements and obtain the transient voltage evaluation result.

[0091] This embodiment also provides a computing device applicable to the case of evaluating transient voltage based on the power flow iteration method of grid-type new energy sources, including:

[0092] The system includes a memory and a processor. The memory stores computer-executable instructions, and the processor executes these instructions to implement the iterative transient voltage evaluation method for grid-based new energy power flow proposed in the above embodiments.

[0093] This embodiment also provides a storage medium storing a computer program that, when executed by a processor, implements the method for evaluating transient voltage based on grid-type new energy power flow iteration as proposed in the above embodiment.

[0094] The storage medium proposed in this embodiment belongs to the same inventive concept as the transient voltage evaluation method based on grid-type new energy power flow iteration proposed in the above embodiments. Technical details not described in detail in this embodiment can be found in the above embodiments, and this embodiment has the same beneficial effects as the above embodiments.

[0095] Example 2

[0096] Reference Figures 2-5 As an embodiment of the present invention, a transient voltage evaluation method based on the power flow iteration of a grid-type new energy source is provided. To verify the beneficial effects of the present invention, a simulation experiment is conducted for scientific demonstration.

[0097] First, the DC nodes in the renewable energy grid system are identified, and a reactive power disturbance equal to the reactive power fluctuation that occurs during the simulated fault is introduced at the DC nodes. Second, a Newton-Raphson power flow calculation is performed on the entire renewable energy grid system to obtain the voltage change ΔU at the grid nodes. 0 Then, the voltage change ΔU of the network node is calculated. 0 After the droop control equation: ΔQ n =K*ΔU n The reactive power injection ΔQ of the new network node was further calculated. n After another Newton-Raphson power flow calculation, it is determined whether the power flow has converged. If it has converged, the error is calculated: ΔU n =||U n -U n-1 If convergence fails, the program stops, and the value of the first reactive power disturbance is reduced and recalculated. Finally, it is determined whether the error size meets the requirements. If it does, the final power flow result is output. If it does not, the number of iterations is checked to see if the maximum value has been reached. If the number of iterations has not reached the maximum value, the reactive power droop coefficient K of the network node is modified. If the number of iterations has reached the maximum value, the set number of iterations is increased until the error requirement is met.

[0098] like Figure 2As shown in the 37-node diagram, node 10 is a DC node, node 8 is a load, nodes 1, 2, 3, 4, and 6 are connected to thermal power units, and nodes 34, 35, 36, and 37 are new energy nodes. New energy nodes can be connected to grid-connected or grid-linked new energy sources.

[0099] Reactive power droop coefficients were set at nodes 34 to 37 for grid-connected or network-structured renewable energy nodes. A simulation model was built based on PSCAD, and a commutation failure fault was simulated by grounding the resistor at node 10 for 100ms. The reactive power disturbance at node 10 was recorded.

[0100] To enrich the experimental scenarios, various experimental conditions were constructed.

[0101] Scenario 1: Select node 34 to connect to the grid-type new energy source, and nodes 35, 36, and 37 to connect to the follow-up grid-type new energy source. Inject reactive power disturbance at DC node 10 to simulate reactive power disturbance caused by commutation failure.

[0102] Scenario 2: Select node 36 to connect to the grid-type new energy source, and nodes 34, 35, and 37 to connect to the follow-up grid-type new energy source. Inject reactive power disturbance at DC node 10 to simulate reactive power disturbance caused by commutation failure.

[0103] Scenario 3: Select nodes 34 and 36 to connect to grid-type new energy, and nodes 35 and 37 to connect to follow-grid type new energy. Inject reactive power disturbance at DC node 10 to simulate reactive power disturbance caused by commutation failure.

[0104] Finally, the transient overvoltage values ​​under the above three scenarios were evaluated using the method of this invention, and an error comparison analysis was performed. Figures 3 to 5 As can be seen, the results calculated by the method of this invention are almost in agreement with the results of PSCAD simulation, with an error within 4%, which meets the calculation requirements. This invention successfully achieves an effective assessment of the commutator bus voltage after commutation failure in a renewable energy grid-connected system, avoiding the problem that the traditional Newton power flow iteration method is not applicable to power flow in renewable energy systems with grids. Furthermore, this invention is applicable not only to single renewable energy grid-connected systems but also to multiple renewable energy grid-connected systems, effectively avoiding the complexity of modeling required for transient overvoltage assessment in multi-grid renewable energy systems.

[0105] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for evaluating transient voltage during power flow iteration of grid-connected new energy sources, characterized in that, include: Build a PSCAD high-voltage DC transmission system and simulate commutation failure faults; Identify the DC nodes in the new energy grid system and introduce reactive power disturbances at the DC nodes; The first power flow calculation was performed on the entire new energy grid system to obtain the voltage change of the grid nodes; Based on the voltage change of the network node, the reactive power injection of the new network node is calculated and injected into the DC node again. Voltage changes at network nodes After the droop control equation: in, This represents the reactive power injection amount of the new network node. This represents the reactive power droop coefficient of a network node. The reactive power injection of the new network node is obtained by calculating the droop control equation. Perform power flow calculations to determine whether the power flow has converged; Perform power flow calculations to determine if the power flow has converged. If it has converged, perform error calculations. If it has not converged, stop the program and re-simulate the commutation failure fault. Reduce the reactive power disturbance at the DC node by resetting the grounding impedance. The expression for error calculation is: in, This represents the voltage change between the nth and (n-1)th iterations. This represents the voltage value during the nth power flow iteration. Determine whether the error magnitude meets the requirements to obtain the transient voltage evaluation result; Determine if the error magnitude meets the requirements. If it does, output the final power flow result. If not, check if the number of iterations has reached the set maximum value. If the number of iterations has not reached the maximum value, modify the reactive power droop coefficient of the network nodes. If the number of iterations has reached the maximum value, the set number of iterations will be increased until the error requirement is met.

2. The method for evaluating transient voltage based on power flow iteration of grid-type new energy sources as described in claim 1, characterized in that, The construction of the PSCAD high-voltage DC transmission system, simulating commutation failure faults, includes: Set up DC nodes in the power transmission system and set a grounding resistance of 100Ω at the DC nodes. Record the highest value of transient voltage at each node during the transient process. Ensure that the PSCAD model can maintain stable operation during the set simulation time before simulating commutation failure.

3. The method for evaluating transient voltage based on power flow iteration of grid-type new energy sources as described in claim 2, characterized in that, The process of determining the DC nodes in the new energy grid system and introducing reactive power disturbances at the DC nodes includes: Select a simulation model, convert the simulation model into Matpower data format, and locate the DC node by matching the node positions one by one. Simulate the commutation failure fault to determine the reactive power disturbance at the DC node. Use the obtained reactive power disturbance as the initial reactive power disturbance to introduce into the DC node in the program.

4. A transient voltage assessment system based on grid-connected new energy power flow iteration, using the method described in any one of claims 1 to 3, characterized in that, include: The simulation module is used to build a PSCAD high-voltage DC transmission system and simulate commutation failure faults. The preprocessing module is used to determine the DC nodes in the new energy grid system and introduce reactive power disturbances at the DC nodes. The injection module is used to perform power flow calculations on the entire new energy grid system to obtain the voltage changes of the grid nodes; Based on the voltage change of the network node, calculate the reactive power injection of the new network node and inject it into the DC node; The power flow calculation module is used to perform power flow calculations and determine whether the power flow has converged. The judgment module is used to determine whether the error magnitude meets the requirements and obtain the transient voltage evaluation result.

5. A computing device, comprising: Memory and processor; The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the computer-executable instructions are executed by the processor, they implement the steps of the method for evaluating transient voltage based on the power flow iteration of a grid-type new energy source as described in any one of claims 1 to 3.

6. A computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the steps of the method for evaluating transient voltage based on the grid-type new energy power flow iteratively as described in any one of claims 1 to 3.

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