Plant-station operation mode combination method, system and equipment of alternating-current power grid and medium

Abstract

The invention discloses a plant-station operation mode combination method, system and equipment for an alternating current power grid and a medium, and the method comprises the steps: enabling a new energy plant station to be equivalent to a constant current source, and enabling a non-new energy plant station to be equivalent to a band-stop grounding branch, so as to construct a power grid system model; analyzing the node impedance matrix of the power grid system model and the variation amplitudes of the operation modes of the different plant station types, and constructing a criterion relational expression of the influence trend of the variation of the operation modes of the different plant station types on the short-circuit current; during actual operation, a criterion value corresponding to each plant station is calculated based on the criterion relational expression; dividing each plant station into a current gain group and a current weakening group according to the criterion value; in the current excess protection mode, the current gain group is set to be in a large mode, and the current weakening group is set to be in a small mode; and in the current under-quantity protection mode, the operation mode is opposite. The method provided by the invention is suitable for the condition that a new energy plant station is connected to an alternating current power grid, and the precision and efficiency of current protection setting calculation are ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a method, system, equipment and medium for combining plant and station operation modes of an alternating current power grid. Background Art

[0002] In the process of selecting the harsh working conditions of the power system, it is necessary to plan the combination of plant and station operation modes. With the expansion of the scale of the power grid and the access of new energy plants and stations, the combination of plant and station operation modes has the problem of too many working conditions and low setting calculation efficiency. Affected by the tolerance of power electronic devices and internal control strategies, new energy plants and stations exhibit voltage-controlled current source characteristics under fault conditions. The output current of the plant and station is coupled with the terminal voltage, and there is a short-circuit current limitation characteristic. Therefore, new energy plants and stations cannot be simply equivalent to grounded branches with resistance for setting calculations like non-new energy plants and stations. The existing plant and station operation mode combination method cannot comprehensively, reasonably and effectively deal with the scenario where new energy plants and stations are connected to the power system.

[0003] It can be seen that how to solve the problem that the existing plant operation mode combination method cannot be applied to the scenario where new energy plants are connected to the power system has become a technical problem that needs to be urgently solved by technical personnel in this field. Summary of the invention

[0004] The present invention provides a method, system, device and medium for combining plant and station operation modes of an AC power grid to solve the technical problem that the existing method for combining plant and station operation modes cannot be applied to scenarios where new energy plants and stations are connected to the power system, and to achieve the technical effect of comprehensively, accurately and efficiently adjusting the plant and station operation modes of the power system where new energy plants and stations are connected.

[0005] In a first aspect, the present invention provides a method for combining plant operation modes of an AC power grid, the method being applied to an AC power grid including a new energy plant and a non-new energy plant, the method comprising:

[0006] In the process of constructing the model of the target AC power grid, each of the new energy plants is equivalent to a constant current source, and each of the non-new energy plants is equivalent to a grounded branch with resistance, so as to construct a power grid system model;

[0007] Respectively obtaining a node impedance matrix in the power grid system model, and an operating mode change range of the new energy plant and the non-new energy plant;

[0008] Analyze the change amplitude of the operation mode and the node impedance matrix, and respectively construct criterion relationship formulas for the influence trend of the change of the operation mode of the new energy plant and the non-new energy plant on the short-circuit current;

[0009] When the model of the target AC power grid is running, the real-time operation mode change amplitude and real-time node impedance corresponding to the plant operation mode changing from a small mode to a large mode are input into the criterion relationship to obtain the criterion value corresponding to each plant;

[0010] Dividing each of the power plants into a current gain group and a current weakening group according to the criterion value;

[0011] If the pre-selected current protection mode to be set is the overcurrent protection mode, the current gain group is set to the large mode and the current reduction group is set to the small mode; if the pre-selected current protection mode to be set is the undercurrent protection mode, the current gain group is set to the small mode and the current reduction group is set to the large mode.

[0012] Preferably, the step of respectively obtaining the node impedance matrix in the power grid system model, the operating mode change ranges of the new energy plant and the non-new energy plant, comprises:

[0013] Constructing an association matrix and a branch admittance matrix according to the connection relationship between each branch and node in the power grid system model;

[0014] Based on the association matrix and the branch admittance matrix, a node admittance matrix is ​​calculated, and the node admittance matrix is ​​inverted to obtain a node impedance matrix; the node impedance matrix at least includes: the self-impedance of the plant access location node, the self-impedance of the fault node, and the mutual impedance between the plant access location nodes and the fault nodes.

[0015] Preferably, the step of respectively obtaining the node impedance matrix in the power grid system model, the operating mode change ranges of the new energy plant and the non-new energy plant, further includes:

[0016] The non-new energy plant is equivalently represented by a first grounding branch of a power supply series impedance, and a variation range of the first operation mode of the non-new energy plant is calculated;

[0017] Add a second grounding branch to the first grounding branch, and set the equivalent impedance value of the second grounding branch to be equal to the change amplitude of the first operation mode, so as to simulate the change of the operation mode of the non-new energy plant from a small mode to a large mode;

[0018] Based on the constant current source in the power grid system model, the variation range of the second operation mode of the new energy plant is calculated.

[0019] Preferably, the relationship formula of the equivalent impedance value of the second grounding branch is:

[0020]

[0021] Where m represents the node location where the non-new energy plant is connected to the power grid, z m1 Indicates the equivalent impedance value of the first grounding branch when the non-new energy plant is in the small mode, z m2 It indicates the equivalent impedance value of the first grounding branch when the non-new energy plant is in large mode.

[0022] Preferably, the analysis of the change amplitude of the operation mode and the node impedance matrix to respectively construct the criterion relationship of the influence trend of the change of the operation mode of the new energy plant and the non-new energy plant on the short-circuit current includes:

[0023] Based on the node impedance matrix and the change range of the first operation mode, calculating the change value of the fault node self-impedance when the operation mode of the non-new energy plant changes from a small mode to a large mode;

[0024] According to the change value, calculating the first short-circuit current change when the operation mode of the non-new energy plant changes from a small mode to a large mode;

[0025] Calculate the second short-circuit current change when the operation mode of the new energy plant changes from a small mode to a large mode according to the node impedance matrix and the change range of the second operation mode;

[0026] Simplified analysis is performed on the first short-circuit current change to obtain a first criterion relationship for the influence trend of the change in the operation mode of the non-new energy plant on the short-circuit current;

[0027] A simplified analysis is performed on the second short-circuit current change to obtain a second criterion relationship for the impact trend of the change in the operating mode of the new energy plant on the short-circuit current.

[0028] Preferably, the first criterion relationship is:

[0029] δ1=Z mm Z ff -Z mf 2 +Δz m Z ff

[0030] Among them, Z mm represents the self-impedance of the node m where the non-renewable energy plant is connected to the grid, f represents the fault node, and Z ff represents the fault node self-impedance before the non-renewable energy plant changes its operation mode from small mode to large mode, Z mf represents the mutual impedance corresponding to nodes m and f;

[0031] The second criterion relationship is:

[0032]

[0033] Among them, p represents the node location where the new energy plant is connected to the power grid, ΔI p Indicates the change range of the second operation mode when the operation mode of the new energy plant changes, Z fp represents the mutual impedance corresponding to nodes f and p.

[0034] Preferably, each of the power plants is divided into a current gain group and a current weakening group according to the criterion value:

[0035] If the criterion value is greater than zero, the corresponding plant is divided into a current gain group;

[0036] If the criterion value is less than or equal to zero, the corresponding plant is divided into a current weakening group.

[0037] In a second aspect, the present invention further provides a plant operation mode combination system for an AC power grid, the method being applied to an AC power grid including a new energy plant and a non-new energy plant, the system comprising: a model building unit, an analysis and calculation unit, a criterion relationship building unit, a criterion value calculation unit, a plant grouping unit and an operation mode combination unit;

[0038] The model building unit is used to, during the model building process of the target AC power grid, equate each of the new energy plants to a constant current source and each of the non-new energy plants to a grounded branch with resistance, so as to build a power grid system model;

[0039] The analysis and calculation unit is used to respectively obtain the node impedance matrix in the power grid system model, the operating mode change range of the new energy plant and the non-new energy plant;

[0040] The criterion relationship constructing unit is used to analyze the change amplitude of the operation mode and the node impedance matrix, and respectively construct criterion relationship formulas for the influence trend of the change of the operation mode of the new energy plant and the non-new energy plant on the short-circuit current;

[0041] The criterion value calculation unit is used to input the real-time operation mode change amplitude and real-time node impedance corresponding to the change from the small mode to the large mode of the plant operation mode into the criterion relationship when the model of the target AC power grid is running, so as to obtain the criterion value corresponding to each plant;

[0042] The plant grouping unit is used to divide each plant into a current gain group and a current weakening group according to the criterion value;

[0043] The operation mode combination unit is used to set the current gain group to a large mode and the current reduction group to a small mode if the pre-selected current protection mode to be set is an overcurrent protection mode; if the pre-selected current protection mode to be set is an undercurrent protection mode, the current gain group is set to a small mode and the current reduction group is set to a large mode.

[0044] In a third aspect, the present invention also provides a computer device, comprising a memory, a processor and a transceiver, which are connected via a bus; the memory is used to store a set of computer program instructions and data, and transmit the stored data to the processor, and the processor executes the program instructions stored in the memory to execute the above-mentioned method for combining plant and station operation modes of the AC power grid.

[0045] In a fourth aspect, the present invention further provides a computer-readable storage medium, wherein a computer program is stored in the computer-readable storage medium. When the computer program is executed, the above-mentioned method for combining plant and station operation modes of the AC power grid is implemented.

[0046] The present invention provides a combined method, system, device and medium for plant operation mode of an AC power grid. Compared with the prior art, the beneficial effects of the embodiments of the present invention are at least one of the following:

[0047] (1) The plant equivalent model is reasonably constructed, and the new energy plant is equivalent to a constant current source. The relationship between the change in short-circuit current when the operating mode of the non-new energy plant and the new energy plant changes is derived. Based on the relationship, the impact trend of the change in the operating mode of all plants in the system on the short-circuit current is analyzed and the operating mode is set, which can effectively solve the limitations of existing methods in dealing with new energy plants.

[0048] (2) The combination results are accurate and efficient. The problem of operating mode combination of new energy power plants and non-new energy power plants is comprehensively considered to ensure the accuracy and efficiency of current protection setting calculation. The power plants are grouped according to the trend of the impact of changes in the power plant operating mode on the short-circuit current. There is no need to set a threshold value, which reduces the complexity of the calculation, improves the efficiency of the combination, and the accuracy of the combination results. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a schematic diagram of steps of a combined method for plant and station operation modes of an AC power grid provided by a preferred embodiment of the present invention;

[0050] Figure 2 It is a schematic diagram of the steps of a method for obtaining a node impedance matrix provided by a preferred embodiment of the present invention;

[0051] Figure 3It is a schematic diagram of the steps of a method for obtaining the variation range of the operation mode provided by a preferred embodiment of the present invention;

[0052] Figure 4 It is a schematic diagram of the method steps for constructing a criterion relationship provided by a preferred embodiment of the present invention;

[0053] Figure 5 It is a schematic diagram of a combined system structure of a plant and station operation mode of an AC power grid provided by a preferred embodiment of the present invention;

[0054] Figure 6 It is a schematic diagram of a computer device provided by a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0055] The following is a detailed explanation of the implementation mode of the present invention in conjunction with the accompanying drawings. The embodiments are provided only for illustrative purposes and cannot be understood as limiting the present invention. The accompanying drawings are only for reference and illustration purposes and do not constitute a limitation on the scope of patent protection of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. In the description of the present invention, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", "third", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, the meaning of "multiple" is two or more.

[0056] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be a connection between the two elements. The terms "vertical", "horizontal", "left", "right", "upper", "lower" and similar expressions used herein are only for illustrative purposes, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0057] In the description of the present invention, it should be noted that, unless otherwise defined, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0058] See also Figure 1 In an embodiment of the present invention, a method for combining plant operation modes of an AC power grid is provided. The method is applied to an AC power grid including a new energy plant and a non-new energy plant. The method includes:

[0059] S1. In the process of constructing the model of the target AC power grid, each of the new energy plants is equivalent to a constant current source, and each of the non-new energy plants is equivalent to a grounded branch with resistance, so as to construct a power grid system model.

[0060] S2. Obtain the node impedance matrix in the power grid system model, and the range of change in the operation modes of the new energy plant and the non-new energy plant respectively.

[0061] S3. Analyze the amplitude of the operation mode change and the node impedance matrix, and respectively construct criterion relationship equations for the influence trend of the operation mode change of the new energy plant and the non-new energy plant on the short-circuit current.

[0062] S4. When the model of the target AC power grid is running, the real-time operating mode change amplitude and real-time node impedance corresponding to the plant operation mode changing from a small mode to a large mode are input into the criterion relationship to obtain the criterion value corresponding to each plant.

[0063] S5. Divide each of the power plants into a current gain group and a current weakening group according to the criterion value.

[0064] S6. If the pre-selected current protection mode to be set is the overcurrent protection mode, the current gain group is set to the large mode and the current reduction group is set to the small mode; if the pre-selected current protection mode to be set is the undercurrent protection mode, the current gain group is set to the small mode and the current reduction group is set to the large mode.

[0065] New energy plants and stations mainly refer to all equipment at the grid connection points of wind farms or solar farms that are centrally connected to the power system. These equipment include but are not limited to transformers, busbars, lines, converters, energy storage systems, wind turbines, photovoltaic power generation equipment, reactive power regulation equipment and auxiliary equipment. In a preferred embodiment of the present invention, in the process of model construction of the target AC power grid, based on the characteristics of the new energy plants and stations, the new energy plants and stations are equivalent to constant current sources. The constant current source is a wide spectrum, high-precision AC current-stabilized power supply with the characteristics of fast response speed, high constant current accuracy, and long-term stable operation. Equivalent new energy plants and stations to constant current sources can fully reflect the characteristics of new energy plants and stations, fully consider the characteristics of voltage-controlled current sources exhibited by new energy plants and stations under fault conditions, and the output current of the new energy plants and stations is coupled with the terminal voltage, and there is a characteristic of short-circuit current limitation.

[0066] Non-new energy power plants, i.e. traditional power plants, refer to power facilities including main transformers, switchgear, high and low voltage cables, distribution boards, relay protection and automatic control, as well as the general term for the supporting structures required for these facilities. The power stations of traditional power plants convert hydropower, wind power, coal and nuclear power into electrical energy. They have a large number of equipment, large volume, complex equipment connections, high safety requirements and strict environmental requirements. In the power plant operation mode combination of the AC power grid, it is equivalent to a grounded branch with resistance, i.e. a grounded branch with series impedance of the power source. In the present invention, it is represented as the first grounded branch.

[0067] A grid system model is constructed based on a constant current source represented by an equivalent representation of a new energy plant and a grounded branch with resistance represented by an equivalent representation of a non-new energy plant. Further, the node impedance matrix in the grid system model, the magnitude of the change in the operation mode of the new energy plant and the non-new energy plant are obtained respectively, such as Figure 2 As shown, the following steps are included:

[0068] S201. Construct an association matrix and a branch admittance matrix according to the connection relationship between each branch and node in the power grid system model.

[0069] S202. Based on the association matrix and the branch admittance matrix, a node admittance matrix is ​​calculated, and the node admittance matrix is ​​inverted to obtain a node impedance matrix; the node impedance matrix includes at least: an equivalent impedance of a node, a self-impedance of a faulty node, and mutual impedance between nodes.

[0070] Based on the power grid system model, the node impedance matrix is ​​calculated. In the power grid system, the node impedance matrix is ​​an important tool for analyzing the current and voltage relationship in the power grid system. The elements of the node impedance matrix represent the impedance between any two nodes in the power grid system. First, according to the connection relationship between each branch and node in the power grid system model, an association matrix is ​​constructed to describe the connection relationship between branches and nodes. If branch k is connected to node i, then A ik=1 or -1, the specific value depends on the direction of the branch and the numbering rule of the node; if they are not connected, then A ik =0. Based on the association matrix, the branch admittance matrix is ​​calculated. The branch admittance matrix is ​​a matrix that represents the admittance parameters of each branch in a circuit. The number of rows and columns is the total number of branches in the circuit. In a network with N nodes and B branches, its branch admittance matrix is ​​a B-order diagonal matrix, with values ​​only on the main diagonal and all other elements are zero.

[0071] Finally, based on the incidence matrix and the branch admittance matrix, the node admittance matrix is ​​calculated using the following formula:

[0072] Y=A*B*A T

[0073] Among them, A represents the correlation matrix, Y represents the branch admittance matrix, A T represents the transpose of the incidence matrix A.

[0074] The node admittance matrix is ​​inverted to obtain a node impedance matrix, which at least includes the self-impedance of the node at the access location of the plant station, the self-impedance of the fault node, and the mutual impedance between the nodes at the access location of the plant station and the fault node.

[0075] Furthermore, the change range of the operation modes of the new energy plants and non-new energy plants in the power grid system model is obtained, such as Figure 3 As shown, the following steps are included:

[0076] S203, using the first grounding branch of the power supply series impedance to equivalently represent the non-new energy plant, and calculating the variation range of the first operation mode of the non-new energy plant.

[0077] Calculate the change range of the first operating mode of non-new energy plants and stations, the calculation formula is:

[0078]

[0079] Where m represents the node location where the non-new energy plant is connected to the power grid, z m1 Indicates the equivalent impedance value of the first grounding branch when the non-new energy plant is in the small mode, z m2 It indicates the equivalent impedance value of the first grounding branch when the non-new energy plant is in large mode.

[0080] The large mode refers to the operation mode in which the power supply power of the power grid system is the largest, the transformer capacity is the largest, and the line impedance is the smallest. In this mode, the power grid system has the smallest short-circuit impedance value, so the short-circuit current generated after a short circuit occurs is the largest.

[0081] The small mode refers to the operation mode in which the power supply power of the power grid system is the smallest, the transformer capacity is the smallest, and the line impedance is the largest. In this mode, the power grid system has the largest short-circuit impedance value, so the short-circuit current generated after a short circuit occurs is the smallest.

[0082] S204. Add a second grounding branch to the first grounding branch, and set the equivalent impedance value of the second grounding branch to be equal to the change amplitude of the first operating mode to simulate the change of the operating mode of the non-new energy plant from a small mode to a large mode.

[0083] Adding a grounding branch usually refers to adding one or more branches connected to the ground in an existing electrical system. In an embodiment of the present invention, a second grounding branch is added to the first grounding branch, which is mainly used to simulate the change of the operating mode of a non-new energy plant from a small mode to a large mode. The equivalent impedance value of the second grounding branch is equal to the change amplitude of the first operating mode.

[0084] S205. Calculate the variation range of the second operation mode of the new energy plant based on the constant current source in the power grid system model.

[0085] In a preferred embodiment of the present invention, a constant current source is selected as an equivalent model for setting calculation of a new energy plant, and the maximum output current of the new energy plant under a fault condition is used to characterize the change range of the operation mode of the new energy plant, that is, the change range of the second operation mode. The relationship between the change range of the second operation mode is:

[0086] ΔI p =I pmax -I pmin =I pmax

[0087] Where p represents the node location where the new energy plant is connected to the power grid; ΔI p Indicates the change range of the second operation mode; I pmax Indicates the maximum output current of the new energy plant in the event of a fault; I pmin It indicates the minimum output current in case of a fault in a new energy plant, and I pmin =0.

[0088] In a preferred embodiment of the present invention, the operating mode change amplitude and the node impedance matrix are analyzed, and the criterion relationship between the operating mode change of the new energy plant and the non-new energy plant and the influence trend of the short-circuit current is constructed respectively, as shown in Figure 4, including the following steps:

[0089] S301. Based on the node impedance matrix and the variation range of the first operation mode, calculate the variation value of the self-impedance of the fault node when the operation mode of the non-new energy plant changes from a small mode to a large mode.

[0090] S302. Calculate, based on the change value, a first short-circuit current change when the operation mode of the non-new energy plant changes from a small mode to a large mode.

[0091] S303. Calculate the second short-circuit current change when the operation mode of the new energy plant changes from a small mode to a large mode according to the node impedance matrix and the change range of the second operation mode.

[0092] S304: Simplify the analysis of the first short-circuit current change to obtain a first criterion relationship for the impact trend of the change in the operating mode of the non-new energy plant on the short-circuit current.

[0093] S305: Simplify the analysis of the second short-circuit current change to obtain a second criterion relationship for the impact trend of the change in the operation mode of the new energy plant on the short-circuit current.

[0094] In a preferred embodiment of the present invention, the calculation of the criterion of the influence trend of the operation mode change of the new energy power plant and the non-new energy power plant on the short-circuit current is analyzed by taking the influence trend of the non-new energy power plant and the new energy power plant on the short-circuit current when the power plant operation mode changes from a small mode to a large mode as an example. When the power plant operation mode changes from a large mode to a small mode, the influence trend of the non-new energy power plant and the new energy power plant on the short-circuit current is opposite to that when the operation mode changes from a small mode to a large mode.

[0095] When the operation mode of the non-new energy plant changes from small mode to large mode, the impact on the self-impedance of the fault node is described by the following relationship:

[0096]

[0097] Where f represents the faulty node, Z ff represents the fault node self-impedance before the non-renewable energy plant changes its operation mode from small mode to large mode, Z ff ' represents the fault node self-impedance after the non-renewable energy plant operation mode changes from small mode to large mode, Z mm represents the self-impedance of the node m where the non-renewable energy plant is connected to the grid, Z mf Represents the mutual impedance corresponding to nodes m and f.

[0098] Furthermore, based on the equivalent model of the first grounding branch of the power supply series impedance, according to the change value of the fault node self-impedance when the non-new energy plant operation mode changes from a small mode to a large mode, the first short-circuit current change when the non-new energy plant operation mode changes from a small mode to a large mode is calculated. The relationship between the first short-circuit current change is:

[0099]

[0100] Among them, ΔIf (m) Indicates the first short-circuit current change.

[0101] For new energy plants, the equivalent constant current source is used as an equivalent model for practical engineering setting calculation of new energy plants. According to the node impedance matrix and the change range of the second operation mode, the change of the second short-circuit current when the operation mode of the new energy plant changes from the small mode to the large mode is calculated. The change of the second short-circuit current is described by the following relationship:

[0102]

[0103] Among them, ΔI f (p) Indicates the change in the second short-circuit current when the operation mode of the new energy plant changes, Z fp represents the mutual impedance corresponding to nodes f and p.

[0104] Based on the relationship between the first short-circuit current change and the second short-circuit current change, the impact trend of the short-circuit current when the operating mode of each plant changes from a small mode to a large mode can be accurately determined. If the short-circuit current change is positive, it means that the impact trend of the short-circuit current when the plant changes from a small mode to a large mode is a gain; if the short-circuit current change is negative, the impact trend is a weakening.

[0105] Analysis of the first short-circuit current change ΔI f (m) The relationship is: ΔI f (m) The positive or negative value depends on the denominator (Z mm Z ff 2 -Z ff Z mf 2 +Δz m Z ff 2 ) is positive or negative. According to the physical definition of the node impedance matrix, for any node, the self-impedance element of the node is always greater than the mutual impedance element associated with the node, that is, Z ff >Z mf , and Z mm >Z mf .

[0106] Since the relationship between the first short-circuit current change and the change in the first short-circuit current involves many calculation steps, it is cumbersome and requires a lot of calculation in practical applications. f (m)The relationship is simplified to obtain a simplified first criterion relationship that can determine the impact trend of the change in the operation mode of non-new energy plants on the short-circuit current. The first criterion relationship can be described by the following relationship:

[0107] δ1=Z mm Z ff -Z mf 2 +Δz m Z ff

[0108] If the first criterion relationship δ1>0, it means that when the traditional plant operation mode changes from a small mode to a large mode, the short-circuit current increases, and the impact trend on the short-circuit current is gain; if the first criterion δ1≤0, it means that when the traditional plant operation mode changes from a small mode to a large mode, the short-circuit current decreases, and the impact trend on the short-circuit current is weakening.

[0109] For new energy plants, by analyzing the relationship between the change in the second short-circuit current, it can be obtained that all variables in the relationship are greater than 0. When the operation mode of the new energy plant changes from a small mode to a large mode, the change in the second short-circuit current is always positive.

[0110] The second criterion relationship is:

[0111]

[0112] Among them, p represents the node location where the new energy plant is connected to the power grid, ΔI p Indicates the change range of the second operation mode when the operation mode of the new energy plant changes, Z fp represents the mutual impedance corresponding to nodes f and p.

[0113] Therefore, when the operation mode of a new energy plant changes from a small mode to a large mode, the impact on the short-circuit current will always be a gain; when the operation mode of a new energy plant changes from a large mode to a small mode, the impact on the short-circuit current will always be a weakening.

[0114] Therefore, when the model of the target AC power grid is running, the real-time operating mode change amplitude and real-time node impedance corresponding to the operating mode of each plant station when the operating mode changes from a small mode to a large mode are substituted into the corresponding criterion, that is, for non-new energy plants, the real-time operating mode change amplitude and real-time node impedance corresponding to the operating mode changes from a small mode to a large mode are substituted into the corresponding first criterion relationship to obtain the criterion value corresponding to the change of the operating mode of the non-new energy plant station from a small mode to a large mode. If the criterion value is greater than zero, the non-new energy plant station is divided into a current gain group. If the criterion value is less than or equal to zero, the non-new energy plant station is divided into a current weakening group.

[0115] For any new energy plant, the corresponding real-time operating mode change amplitude and real-time node impedance when it changes from a small mode to a large mode are substituted into the corresponding second criterion relationship. If the corresponding criterion values ​​obtained when the operating mode of the new energy plant changes from a small mode to a large mode are all greater than zero, the new energy plant is divided into a current gain group.

[0116] As shown in Table 1, the combination settings of various plant and station operation modes of the AC power grid are shown. In the process of combining various plant and station operation modes of the AC power grid, the current protection mode to be set is determined according to the protection to be set. If the protection mode to be set is current protection, that is, the current overload protection mode, the protection principle is "when the current measurement value is greater than the action setting value, the protection action is started", then the maximum value of the short-circuit current needs to be calculated, and correspondingly, the current gain group is set to the large mode, and the current reduction group is set to the small mode. If the protection to be set is distance protection, that is, the current under-current protection mode, the protection principle is "when the current measurement value is less than the action setting value, the protection action is started", then the minimum value of the short-circuit current needs to be calculated, and correspondingly, the current gain group is set to the small mode, and the current reduction group is set to the large mode.

[0117] Table 1

[0118] Protection status to be set Corresponding group Setting method Overcurrent protection Current Gain Group Big Way Overcurrent protection Current reduction group Small way Undercurrent protection Current Gain Group Small way Undercurrent protection Current reduction group Big Way

[0119] In a preferred embodiment of the present invention, in the process of constructing the model of the target AC power grid, each new energy plant is equivalent to a constant current source, and each non-new energy plant is equivalent to a grounded branch with resistance, so as to construct a power grid system model; the node impedance matrix, the operating mode change amplitude of the new energy plant and the non-new energy plant in the power grid system model are respectively obtained; the operating mode change amplitude and the node impedance matrix are analyzed to construct a criterion relationship for the influence trend of the operating mode change of the new energy plant and the non-new energy plant on the short-circuit current; when the model of the target AC power grid is running, the real-time operating mode change amplitude and real-time node impedance corresponding to the plant operation mode changing from a small mode to a large mode are input into the criterion relationship to obtain the criterion value corresponding to each plant; each plant is divided into a current gain group and a current weakening group according to the criterion value; if the pre-selected current protection mode to be set is an overcurrent protection mode, the current gain group is set to a large mode, and the current weakening group is set to a small mode; if the pre-selected current protection mode to be set is an undercurrent protection mode, the current gain group is set to a small mode, and the current weakening group is set to a large mode. The method for combining plant and station operating modes of an AC power grid provided by the present invention can effectively solve the limitations of existing combination methods in dealing with the access of new energy plants and stations, comprehensively consider the combination of operating modes of new energy plants and stations and non-new energy plants and stations, ensure the accuracy and efficiency of current protection setting calculations, and there is no need to set a threshold value.

[0120] In order to further illustrate the method for combining plant and station operation modes of an AC power grid provided by an embodiment of the present invention, the present invention is further described below in conjunction with specific examples.

[0121] The IEEE 10-machine 39-node standard test system is selected. The access nodes of the new energy plant are set to 30, 32, 36 and 37, and the access nodes of the non-new energy plant are set to 31, 33, 34, 35, 38 and 39. The per-unit value of the electromotive force of the non-new energy plant is 1 and the phase is consistent. The type of the new energy plant is a doubly fed wind turbine generator set, the transformer ratio is 1, the resistance is not considered in the calculation, and the fault type is a three-phase metallic fault.

[0122] Select different protection coordination situations, calculate the calculated value of the first criterion δ1 corresponding to each non-new energy plant, and compare it with the short-circuit current change Δk when the operation mode of the non-new energy plant changes from small mode to large mode. z The calculation results are compared in Table 1.

[0123] Table 2 Calculated value of the first criterion δ1 and short-circuit current change Δk of IEEE 39-bus system z Comparison of calculated values

[0124]

[0125] According to the comparison results in Table 2, the first criterion δ1 based on the traditional power plant grouping that affects the trend, under different protection conditions to be set, the positive and negative values ​​of the calculated value of the first criterion δ1 can be compared with the short-circuit current change Δk when the operation mode of the non-new energy power plant changes. z The positive and negative correspond accurately. According to the definition of non-new energy plant grouping, δ1>0 means that when the operation mode of the non-new energy plant changes from a small mode to a large mode, the influence trend on the short-circuit current is gain, and δ1≤0 means that the influence trend of the non-new energy plant on the short-circuit current is weakened. The judgment results are consistent with the judgment results based on the change in short-circuit current. According to the above analysis, the first criterion δ1 for the grouping of non-new energy plants of the present invention is verified for the judgment of the influence trend and the accuracy of the grouping of non-new energy plants.

[0126] Based on the different protection coordination situations in the IEEE 10-machine 39-node standard test system, the influence trend of the short-circuit current when the non-new energy plant operation mode changes from a small mode to a large mode is judged according to the calculated value of the first criterion δ1, and the non-new energy plant operation modes of different groups are obtained based on the influence trend. The results are shown in Table 3, and the maximum short-circuit current is selected as the severe short-circuit current.

[0127] Table 3 IEEE 39-bus system non-new energy plant grouping and operation mode setting results

[0128]

[0129] The enumeration method is used to calculate the severe short-circuit current, and the calculation results are compared with those of the method of the present invention, see Table 4, where the non-new energy plant operation mode grouping adopts the results shown in Table 3, and the new energy plant operation mode is uniformly selected as the large mode based on the goal of calculating the maximum value of the short-circuit current.

[0130] Table 4 Calculation results of severe short-circuit current for IEEE 39-bus system using different methods

[0131]

[0132] It should be noted that in Table 4, taking "31, 38, 39 small; the rest large" as an example, it means that the operation mode of the non-new energy plants and stations with access nodes 31, 38 and 39 is set to the small mode, and the operation mode of the non-new energy plants and stations with access nodes 33, 34 and 35, and the new energy plants and stations with access nodes 30, 32, 36 and 37 is set to the large mode.

[0133] According to Table 3, combined with the method of the present invention, the influence trend of the change of plant operation mode on the short-circuit current can be determined, and the plant operation mode corresponding to the severe working condition of the power system under the corresponding protection coordination can be directly selected. It can be seen from Table 3 and Table 4 that the calculated severe short-circuit current values ​​are consistent when the enumeration method and the method of the present invention are applied. The accuracy of the calculation of the severe short-circuit current of the plant connected to the power grid containing new energy has been verified by the method of the present invention.

[0134] Accordingly, if Figure 5 As shown, based on a method for combining plant and station operation modes of an AC power grid, an embodiment of the present invention further provides a system for combining plant and station operation modes of an AC power grid, the system being applied to an AC power grid including a new energy plant and station and a non-new energy plant and station, comprising: a model building unit 1, an analysis and calculation unit 2, a criterion relationship building unit 3, a criterion value calculation unit 4, a plant and station grouping unit 5 and an operation mode combining unit 6;

[0135] The model building unit 1 is used to construct a power grid system model by equating each of the new energy plants to a constant current source and each of the non-new energy plants to a grounded branch with resistance during the model building process of the target AC power grid.

[0136] The analysis and calculation unit 2 is used to respectively obtain the node impedance matrix in the power grid system model, and the range of change in the operation mode of the new energy plant and the non-new energy plant.

[0137] The criterion relationship constructing unit 3 is used to analyze the operating mode change amplitude and the node impedance matrix, and construct a criterion relationship for the influence trend of the operating mode change of the new energy plant and the non-new energy plant on the short-circuit current.

[0138] The criterion value calculation unit 4 is used to input the real-time operation mode change amplitude and real-time node impedance corresponding to the change of the plant operation mode from the small mode to the large mode into the criterion relationship when the model of the target AC power grid is running, so as to obtain the criterion value corresponding to each plant.

[0139] The plant grouping unit 5 is used to divide each plant into a current gain group and a current weakening group according to the criterion value.

[0140] The operation mode combination unit 6 is used to set the current gain group to a large mode and the current reduction group to a small mode if the pre-selected current protection mode to be set is an overcurrent protection mode; if the pre-selected current protection mode to be set is an undercurrent protection mode, the current gain group is set to a small mode and the current reduction group is set to a large mode.

[0141] For the specific definition of a combined system of plant and station operation modes of an AC power grid, please refer to the above-mentioned definition of a combined method of plant and station operation modes of an AC power grid, which will not be repeated here. A person of ordinary skill in the art can appreciate that the various modules and steps described in conjunction with the embodiments disclosed in the present invention can be implemented in hardware, software, or a combination of both. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0142] like Figure 6 As shown, a computer device provided in an embodiment of the present invention includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, the steps in the above-mentioned AC power grid plant station operation mode combination method embodiment are implemented, for example Figure 1 Steps S1 to S6 described in .

[0143] Those skilled in the art will understand that the Figure 6 It is only an example of a computer device and does not constitute a limitation of the computer device. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the computer device may also include input and output devices, network access devices, buses, etc.

[0144] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc. The processor is the control center of the computer device, and uses various interfaces and lines to connect various parts of the entire computer device.

[0145] The memory can be used to store the computer program and / or module, and the processor realizes various functions of the computer device by running or executing the computer program and / or module stored in the memory, and calling the data stored in the memory. The memory can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, an application required for at least one function (such as a sound playback function, an image playback function, etc.), etc.; the data storage area can store data created according to the use of the mobile phone (such as audio data, a phone book, etc.), etc. In addition, the memory can include a high-speed random access memory, and can also include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0146] Wherein, if the module integrated in the computer device is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Wherein, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form, etc. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electrical carrier signal, telecommunication signal and software distribution medium, etc.

[0147] A person skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium, and when the program is executed, it can include the processes of the embodiments of the above-mentioned methods. The storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0148] Accordingly, an embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium includes a stored computer program, wherein when the computer program is executed, the device where the computer-readable storage medium is located is controlled to execute the steps in the combined method of plant and station operation modes of the AC power grid in the above embodiment, for example Figure 1 Steps S1 to S6 described in .

[0149] A method, system, computer device and storage medium for combining plant and station operation modes of an AC power grid provided in this embodiment address the technical problem that existing methods for combining plant and station operation modes cannot be applied to scenarios where new energy plants and stations are connected to the power system. The present invention constructs a power grid system model by, during the process of constructing a model of a target AC power grid, making each new energy plant equivalent to a constant current source and each non-new energy plant equivalent to a grounded branch with resistance; respectively obtaining a node impedance matrix, an operation mode change amplitude of the new energy plant and the non-new energy plant in the power grid system model; analyzing the operation mode change amplitude and the node impedance matrix, and constructing a criterion relationship for the influence trend of the operation mode change of the new energy plant and the non-new energy plant on the short-circuit current; when the model of the target AC power grid is running, the real-time operation mode change amplitude and the real-time node impedance corresponding to the plant operation mode changing from a small mode to a large mode are input into the criterion relationship to obtain the criterion value corresponding to each plant; according to the criterion value, each plant is divided into a current gain group and a current weakening group; if the pre-selected current protection mode to be set is an overcurrent protection mode, the current gain group is set to a large mode, and the current weakening group is set to a small mode; if the pre-selected current protection mode to be set is an undercurrent protection mode, the current gain group is set to a small mode, and the current weakening group is set to a large mode. The method for combining plant and station operating modes of an AC power grid provided by the present invention can effectively solve the limitations of existing combination methods in dealing with the access of new energy plants and stations, comprehensively consider the combination of operating modes of new energy plants and stations and non-new energy plants and stations, ensure the accuracy and efficiency of current protection setting calculations, and there is no need to set a threshold value.

[0150] The above-mentioned embodiments only express several preferred implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principle of the present invention, and these improvements and substitutions should also be regarded as the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for combining plant and station operation modes of an AC power grid, characterized in that: The method is applied to an AC power grid including a new energy plant and a non-new energy plant, and the method comprises: In the process of constructing the model of the target AC power grid, each of the new energy plants is equivalent to a constant current source, and each of the non-new energy plants is equivalent to a grounded branch with resistance, so as to construct a power grid system model; Respectively obtaining a node impedance matrix in the power grid system model, and an operating mode change range of the new energy plant and the non-new energy plant; Analyze the change amplitude of the operation mode and the node impedance matrix, and respectively construct criterion relationship formulas for the influence trend of the change of the operation mode of the new energy plant and the non-new energy plant on the short-circuit current; When the model of the target AC power grid is running, the real-time operation mode change amplitude and real-time node impedance corresponding to the plant operation mode changing from a small mode to a large mode are input into the criterion relationship to obtain the criterion value corresponding to each plant; Dividing each of the power plants into a current gain group and a current weakening group according to the criterion value; If the pre-selected current protection mode to be set is the overcurrent protection mode, the current gain group is set to the large mode and the current reduction group is set to the small mode; if the pre-selected current protection mode to be set is the undercurrent protection mode, the current gain group is set to the small mode and the current reduction group is set to the large mode.

2. The method for combining plant and station operation modes of an AC power grid according to claim 1, characterized in that: The step of respectively obtaining the node impedance matrix in the power grid system model, the operating mode change range of the new energy plant and the non-new energy plant includes: Constructing an association matrix and a branch admittance matrix according to the connection relationship between each branch and node in the power grid system model; Based on the association matrix and the branch admittance matrix, a node admittance matrix is ​​calculated, and the node admittance matrix is ​​inverted to obtain a node impedance matrix, wherein the node impedance matrix at least includes: self-impedance of nodes at the plant access location, self-impedance of fault nodes, and mutual impedance between nodes at the plant access location and between fault nodes.

3. The method for combining plant and station operation modes of an AC power grid according to claim 2, characterized in that: The step of respectively obtaining the node impedance matrix in the power grid system model, the operating mode change range of the new energy plant and the non-new energy plant also includes: The non-new energy plant is equivalently represented by a first grounding branch of a power supply series impedance, and a variation range of the first operation mode of the non-new energy plant is calculated; Add a second grounding branch to the first grounding branch, and set the equivalent impedance value of the second grounding branch to be equal to the change amplitude of the first operation mode, so as to simulate the change of the operation mode of the non-new energy plant from a small mode to a large mode; Based on the constant current source in the power grid system model, the variation range of the second operation mode of the new energy plant is calculated.

4. The method for combining plant and station operation modes of an AC power grid according to claim 3, characterized in that: The relationship between the equivalent impedance value of the second grounding branch is: Where m represents the node location where the non-new energy plant is connected to the power grid, z m1 Indicates the equivalent impedance value of the first grounding branch when the non-new energy plant is in the small mode, z m2 It indicates the equivalent impedance value of the first grounding branch when the non-new energy plant is in large mode.

5. The method for combining plant and station operation modes of an AC power grid according to claim 4, characterized in that: The analysis of the change amplitude of the operation mode and the node impedance matrix, and the construction of the criterion relationship of the influence trend of the change of the operation mode of the new energy plant and the non-new energy plant on the short-circuit current, respectively, include: Based on the node impedance matrix and the change range of the first operation mode, calculating the change value of the fault node self-impedance when the operation mode of the non-new energy plant changes from a small mode to a large mode; According to the change value, calculating the first short-circuit current change when the operation mode of the non-new energy plant changes from a small mode to a large mode; Calculate the second short-circuit current change when the operation mode of the new energy plant changes from a small mode to a large mode according to the node impedance matrix and the change range of the second operation mode; Simplified analysis is performed on the first short-circuit current change to obtain a first criterion relationship for the influence trend of the change in the operation mode of the non-new energy plant on the short-circuit current; A simplified analysis is performed on the second short-circuit current change to obtain a second criterion relationship for the impact trend of the change in the operating mode of the new energy plant on the short-circuit current.

6. The method for combining plant and station operation modes of an AC power grid according to claim 5, characterized in that: The first criterion relationship is: δ1=Z mm WITH ff -WITH mf 2 +Δz m WITH ff Among them, Z mm represents the self-impedance of the node m where the non-renewable energy plant is connected to the grid, f represents the fault node, and Z ff represents the fault node self-impedance before the non-renewable energy plant changes its operation mode from small mode to large mode, Z mf represents the mutual impedance corresponding to nodes m and f; The second criterion relationship is: Among them, p represents the node location where the new energy plant is connected to the power grid, ΔI p Indicates the change range of the second operation mode when the operation mode of the new energy plant changes, Z fp represents the mutual impedance corresponding to nodes f and p.

7. The method for combining plant and station operation modes of an AC power grid according to claim 6, characterized in that: The plants are divided into current gain groups and current weakening groups according to the criterion values: If the criterion value is greater than zero, the corresponding plant is divided into a current gain group; If the criterion value is less than or equal to zero, the corresponding plant is divided into a current weakening group.

8. A combined system of plant and station operation modes of an AC power grid, characterized in that: The method is applied to an AC power grid including new energy plants and non-new energy plants, and the system includes: a model building unit, an analysis and calculation unit, a criterion relationship building unit, a criterion value calculation unit, a plant grouping unit and an operation mode combination unit; The model building unit is used to, during the model building process of the target AC power grid, equate each of the new energy plants to a constant current source and each of the non-new energy plants to a grounded branch with resistance, so as to build a power grid system model; The analysis and calculation unit is used to respectively obtain the node impedance matrix in the power grid system model, the operating mode change range of the new energy plant and the non-new energy plant; The criterion relationship constructing unit is used to analyze the change amplitude of the operation mode and the node impedance matrix, and respectively construct criterion relationship formulas for the influence trend of the change of the operation mode of the new energy plant and the non-new energy plant on the short-circuit current; The criterion value calculation unit is used to input the real-time operation mode change amplitude and real-time node impedance corresponding to the change from the small mode to the large mode of the plant operation mode into the criterion relationship when the model of the target AC power grid is running, so as to obtain the criterion value corresponding to each plant; The plant grouping unit is used to divide each plant into a current gain group and a current weakening group according to the criterion value; The operation mode combination unit is used to set the current gain group to a large mode and the current reduction group to a small mode if the pre-selected current protection mode to be set is an overcurrent protection mode; if the pre-selected current protection mode to be set is an undercurrent protection mode, the current gain group is set to a small mode and the current reduction group is set to a large mode.

9. A computer device, characterized in that: The computer device includes a memory, a processor and a transceiver, which are connected via a bus; the memory is used to store a set of computer program instructions and data, and transmit the stored data to the processor, and the processor executes the program instructions stored in the memory to execute the combined method of plant operation modes of the AC power grid as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed, the method for combining plant and station operation modes of an AC power grid as claimed in any one of claims 1 to 7 is implemented.

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