Stability evaluation method, device and equipment of receiving end system and storage medium

Abstract

The invention discloses a stability evaluation method and device of a receiving end system, equipment and a storage medium. The method comprises the following steps: determining a network equation of the receiving end system according to a correction value of an admittance array diagonal element, a set of internal potentials of all synchronous generators, a set of voltages of nodes and a total current of the new energy system and the synchronous generators; determining an open-circuit voltage and a short-circuit current of a node incorporated into the new energy system in the receiving end system according to the network equation; determining an interaction factor according to the voltage change quantity and the current change quantity; and determining the multi-infeed short-circuit ratio according to the rated capacity, the open-circuit voltage, the short-circuit current and the interaction factor. According to the invention, the relative capacity between the receiving end system and the new energy system can be visually compared through the short-circuit ratio; and planning and operation of new energy grid connection can be guided more accurately and efficiently through the interaction factors.

Description

Technical Field

[0001] The present invention relates to the technical field of power system stability assessment, and in particular to a receiving-end system stability assessment method, device, equipment and storage medium. Background Art

[0002] With the development of direct current transmission and the increasing scale of power generation from new energy sources such as wind power and photovoltaic power, the power of direct current or new energy stations connected to the receiving system continues to increase, and the support strength of the power grid at the grid connection point is relatively weak, which reduces the safety and stability of the power system. At the same time, the formic acid method used in the existing technology to determine the stability of the power system is less efficient and cannot fully reflect the stability of the power system. Summary of the invention

[0003] Based on this, it is necessary to propose a stability evaluation method, device, equipment and storage medium for the receiving system to address the above problems.

[0004] A method for evaluating the stability of a receiving system, wherein the receiving system is an AC system incorporated into a new energy system, and the receiving system includes a synchronous generator, and the method comprises:

[0005] Obtaining the correction values ​​of the diagonal elements of the admittance array of the receiving system, the set of internal potentials of all synchronous generators, the set of voltages of nodes in the receiving system when the new energy system is not incorporated, and the total current of the new energy system and the synchronous generators;

[0006] Determine the network equation of the receiving-end system according to the correction value of the diagonal element of the admittance array, the set of the internal potentials of all the synchronous generators, the set of the voltages of the nodes, and the total current of the new energy system and the synchronous generators;

[0007] Determine the open circuit voltage and short circuit current of the node in the receiving end system that has been incorporated into the new energy system according to the network equation;

[0008] Obtaining the rated capacity of the new energy system;

[0009] Determine a single-feed short-circuit ratio according to the rated capacity, the open-circuit voltage and the short-circuit current;

[0010] Obtaining a voltage conversion amount and a current change amount after the node is incorporated into the new energy system;

[0011] Determining an interaction factor according to the voltage change amount and the current change amount;

[0012] A multi-infeed short-circuit ratio is determined according to the rated capacity, the open-circuit voltage, the short-circuit current and the interaction factor.

[0013] In one embodiment, the correction values ​​of the diagonal elements of the admittance array are determined by the following steps:

[0014] Obtaining the equivalent admittance of the receiving system and the node admittance matrix of the classical system;

[0015] The correction values ​​of the diagonal elements of the admittance matrix are determined according to the equivalent admittance of the receiving system and the node admittance matrix of the classical system.

[0016] In one embodiment, the equivalent admittance is obtained by the following steps:

[0017] Obtain node voltage, load power, active power and reactive power;

[0018] The equivalent admittance is determined according to the voltage, load power, active power and reactive power.

[0019] In one embodiment, the equivalent admittance is obtained by the following formula:

[0020]

[0021] Among them, Y Li is the equivalent admittance at node i; U i is the voltage of node i; S Li is the load power of node i, P Li is the active power of node i, Q Li is the reactive power of node i, and j is the coefficient.

[0022] In one embodiment, the expression of the correction value of the diagonal element of the admittance array is as follows:

[0023]

[0024] in, is the correction value of the diagonal element of the admittance matrix, Y is the node admittance matrix of the classical system, Y L Is the equivalent admittance Y Li The diagonal array of .

[0025] In one embodiment, determining the open circuit voltage and short circuit current of the node in the receiving system according to the network equation includes:

[0026] Obtaining a vector consisting of a synchronous generator current at a node where the synchronous generator is located and a first voltage of the node when the synchronous generator is not incorporated into the new energy system;

[0027] Determine the open circuit voltage according to a vector consisting of the synchronous generator current and the voltage;

[0028] Acquiring a second voltage of a node that is not incorporated into the new energy system;

[0029] The short-circuit current is determined based on the synchronous generator current and the second voltage.

[0030] In one embodiment, the open circuit voltage is obtained by the following formula:

[0031]

[0032] Among them, U i,oc represents the open circuit voltage at node i, represents the i-th row of the identity matrix, I S is the synchronous generator current of the node where the synchronous generator is located, and U is the vector composed of the first voltage of the node when it is not incorporated into the new energy system;

[0033] The short-circuit current is obtained by the following formula:

[0034]

[0035] Among them, I i,sc is the short-circuit current at node i, is the nth row of the identity matrix, is the second voltage of the node not incorporated into the new energy system, I S is the synchronous generator current at the node where the synchronous generator is located.

[0036] A device for evaluating the stability of a receiving end system, the device comprising:

[0037] A first acquisition module is used to obtain the correction value of the diagonal element of the admittance array of the receiving system, the set of internal potentials of all synchronous generators, the set of voltages of nodes in the receiving system when the new energy system is not incorporated, and the total current of the new energy system and the synchronous generator;

[0038] A first determination module is used to determine the network equation of the receiving end system according to the correction value of the diagonal element of the admittance array, the set of internal potentials of all synchronous generators, the set of voltages of the nodes and the total current of the new energy system and the synchronous generator;

[0039] A second determination module is used to determine the open circuit voltage and short circuit current of the node in the receiving end system that has been incorporated into the new energy system according to the network equation;

[0040] A second acquisition module, used to acquire the rated capacity of the new energy system;

[0041] A fourth determination module, configured to determine a single-feed short-circuit ratio according to the rated capacity, the open-circuit voltage and the short-circuit current;

[0042] A third acquisition module is used to acquire the voltage conversion amount and current change amount after the node is incorporated into the new energy system;

[0043] The fifth determination module is used to determine the interaction factor according to the voltage transformation amount and the current change amount; and determine the multi-input short-circuit ratio according to the rated capacity, the open-circuit voltage, the short-circuit current and the interaction factor.

[0044] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor performs the following steps:

[0045] Obtaining the correction values ​​of the diagonal elements of the admittance array of the receiving system, the set of internal potentials of all synchronous generators, the set of voltages of nodes in the receiving system when the new energy system is not incorporated, and the total current of the new energy system and the synchronous generators;

[0046] Determine the network equation of the receiving-end system according to the correction value of the diagonal element of the admittance array, the set of the internal potentials of all the synchronous generators, the set of the voltages of the nodes, and the total current of the new energy system and the synchronous generators;

[0047] Determine the open circuit voltage and short circuit current of the node in the receiving end system that has been incorporated into the new energy system according to the network equation;

[0048] Obtaining the rated capacity of the new energy system;

[0049] Determine a single-feed short-circuit ratio according to the rated capacity, the open-circuit voltage and the short-circuit current;

[0050] Obtaining a voltage conversion amount and a current change amount after the node is incorporated into the new energy system;

[0051] Determining an interaction factor according to the voltage change amount and the current change amount;

[0052] A multi-infeed short-circuit ratio is determined according to the rated capacity, the open-circuit voltage, the short-circuit current and the interaction factor.

[0053] A computer-readable storage medium stores a computer program, which, when executed by a processor, causes the processor to perform the following steps:

[0054] Obtaining the correction values ​​of the diagonal elements of the admittance array of the receiving system, the set of internal potentials of all synchronous generators, the set of voltages of nodes in the receiving system when the new energy system is not incorporated, and the total current of the new energy system and the synchronous generators;

[0055] Determine the network equation of the receiving-end system according to the correction value of the diagonal element of the admittance array, the set of the internal potentials of all the synchronous generators, the set of the voltages of the nodes, and the total current of the new energy system and the synchronous generators;

[0056] Determine the open circuit voltage and short circuit current of the node in the receiving end system that has been incorporated into the new energy system according to the network equation;

[0057] Obtaining the rated capacity of the new energy system;

[0058] Determine a single-feed short-circuit ratio according to the rated capacity, the open-circuit voltage and the short-circuit current;

[0059] Obtaining a voltage conversion amount and a current change amount after the node is incorporated into the new energy system;

[0060] Determining an interaction factor according to the voltage change amount and the current change amount;

[0061] A multi-infeed short-circuit ratio is determined according to the rated capacity, the open-circuit voltage, the short-circuit current and the interaction factor.

[0062] The present application obtains the correction value of the diagonal element of the admittance array of the receiving system, the set of the internal potentials of all synchronous generators, the set of the voltages of the nodes in the receiving system when the new energy system is not incorporated, and the total current of the new energy system and the synchronous generators; determines the network equation of the receiving system according to the correction value of the diagonal element of the admittance array, the set of the internal potentials of all synchronous generators, the set of the voltages of the nodes, and the total current of the new energy system and the synchronous generators; determines the open-circuit voltage and short-circuit current of the nodes in the receiving system that have been incorporated into the new energy system according to the network equation; obtains the rated capacity of the new energy system; determines the single-feed short-circuit ratio according to the rated capacity, the open-circuit voltage and the short-circuit current; obtains the voltage transformation amount and the current change amount after the node is incorporated into the new energy system; determines the interaction factor according to the voltage transformation amount and the current change amount; determines the multi-feed short-circuit ratio according to the rated capacity, the open-circuit voltage, the short-circuit current and the interaction factor. The present application can intuitively compare the relative sizes of the capacities between the receiving system and the new energy system through the short-circuit ratio; the larger the short-circuit ratio, the better the static stability after the DC or new energy is connected to the receiving system; the smaller the interaction factor, the lower the degree of coupling between different DC transmission lines; thereby more accurately and efficiently guiding the planning and operation of the new energy grid connection. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0064] in:

[0065] Figure 1 is an application environment diagram of a method for evaluating the stability of a receiving end system in one embodiment;

[0066] Figure 2 is a flow chart of a method for evaluating the stability of a receiving end system in one embodiment;

[0067] Figure 3 is a structural block diagram of a stability evaluation device for a receiving end system in one embodiment;

[0068] Figure 4 FIG. 4 is a structural block diagram of a computer device in one embodiment. DETAILED DESCRIPTION

[0069] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0070] With the development of direct current transmission and the increasing scale of new energy power generation such as wind power and photovoltaic power, the power of direct current or new energy stations connected to the receiving system is increasing, and the grid support strength at the grid connection point is weak, which reduces the safety and stability of the power system. At the same time, the formic acid method used in the prior art to determine the stability of the power system is inefficient and cannot fully reflect the stability of the power system. In order to solve the above technical problems, this application provides a method for evaluating the stability of the receiving system. Figure 1 FIG. 1 is an application environment diagram of a method for evaluating the stability of a receiving end system in an embodiment. Figure 1, the stability assessment method of the receiving system is applied to the stability assessment system of the receiving system. The stability assessment system of the receiving system includes a terminal 110 and a server 120. The terminal 110 and the server 120 are connected through a network. The terminal 110 can be a desktop terminal or a mobile terminal. The mobile terminal can be at least one of a mobile phone, a tablet computer, a laptop computer, etc. The server 120 can be implemented by an independent server or a server cluster composed of multiple servers. The terminal 110 is used to obtain the correction value of the diagonal element of the admittance array of the receiving system, the set of the internal potentials of all synchronous generators, the set of the voltage of the nodes in the receiving system when the new energy system is not incorporated, and the total current of the new energy system and the synchronous generator; obtain the rated capacity of the new energy system; obtain the voltage change amount and current change amount after the node is incorporated into the new energy system. The server 120 is used to determine the network equation of the receiving system according to the correction value of the diagonal element of the admittance array, the set of the internal potentials of all synchronous generators, the set of the voltage of the nodes, and the total current of the new energy system and the synchronous generator. According to the network equation, the open circuit voltage and short circuit current of the node in the receiving system that has been incorporated into the new energy system are determined. The single-feed short-circuit ratio is determined according to the rated capacity, the open-circuit voltage and the short-circuit current. The interaction factor is determined according to the voltage change amount and the current change amount; and the multi-feed short-circuit ratio is determined according to the rated capacity, the open-circuit voltage, the short-circuit current and the interaction factor.

[0071] like Figure 2 As shown, in one embodiment, a method for evaluating the stability of a receiving system is provided. The method can be applied to both a terminal and a server. This embodiment is illustrated by applying to a terminal. The receiving system is an AC system incorporated into a new energy system, and the receiving system includes a synchronous generator. The method includes:

[0072] S10: obtaining the correction value of the diagonal element of the admittance array of the receiving system, the set of internal potentials of all synchronous generators, the set of voltages of nodes in the receiving system when the new energy system is not incorporated, and the total current of the new energy system and the synchronous generator;

[0073] S20: determining the network equation of the receiving-end system according to the correction value of the diagonal element of the admittance array, the set of the internal potentials of all the synchronous generators, the set of the voltages of the nodes, and the total current of the new energy system and the synchronous generators;

[0074] S30: determining the open circuit voltage and short circuit current of the node in the receiving system that has been incorporated into the new energy system according to the network equation;

[0075] S40: Obtaining the rated capacity of the new energy system;

[0076] S50: determining a single-feed short-circuit ratio according to the rated capacity, the open-circuit voltage and the short-circuit current;

[0077] S60: Obtaining a voltage conversion amount and a current change amount after the node is incorporated into the new energy system;

[0078] S70: determining an interaction factor according to the voltage change amount and the current change amount;

[0079] S80: Determine a multi-infeed short-circuit ratio according to the rated capacity, the open-circuit voltage, the short-circuit current and the interaction factor.

[0080] The present application obtains the correction value of the diagonal element of the admittance array of the receiving system, the set of the internal potentials of all synchronous generators, the set of the voltages of the nodes in the receiving system when the new energy system is not incorporated, and the total current of the new energy system and the synchronous generators; determines the network equation of the receiving system according to the correction value of the diagonal element of the admittance array, the set of the internal potentials of all synchronous generators, the set of the voltages of the nodes, and the total current of the new energy system and the synchronous generators; determines the open-circuit voltage and short-circuit current of the nodes in the receiving system that have been incorporated into the new energy system according to the network equation; obtains the rated capacity of the new energy system; determines the single-feed short-circuit ratio according to the rated capacity, the open-circuit voltage and the short-circuit current; obtains the voltage transformation amount and the current change amount after the node is incorporated into the new energy system; determines the interaction factor according to the voltage transformation amount and the current change amount; determines the multi-feed short-circuit ratio according to the rated capacity, the open-circuit voltage, the short-circuit current and the interaction factor. The present application can intuitively compare the relative sizes of the capacities between the receiving system and the new energy system through the short-circuit ratio; the larger the short-circuit ratio, the better the static stability after the DC or new energy is connected to the receiving system; the smaller the interaction factor, the lower the degree of coupling between different DC transmission lines; thereby more accurately and efficiently guiding the planning and operation of the new energy grid connection.

[0081] In one embodiment, in step S10, the correction value of the diagonal element of the admittance array is determined by the following steps:

[0082] S101: Obtaining the equivalent admittance of the receiving system and the node admittance matrix of the classical system;

[0083] Specifically, in this step, the equivalent admittance is obtained through the following steps: obtaining the voltage, load power, active power and reactive power of the node; and determining the equivalent admittance according to the voltage, load power, active power and reactive power.

[0084] The equivalent admittance is obtained by the following formula:

[0085]

[0086] Among them, Y Li is the equivalent admittance at node i; U i is the voltage of node i; S Li is the load power of node i, P Li is the active power of node i, Q Li is the reactive power of node i, and m is the coefficient.

[0087] S102: Determine the correction value of the diagonal element of the admittance matrix according to the equivalent admittance of the receiving system and the node admittance matrix of the classical system.

[0088] Specifically, the expression of the correction value of the diagonal element of the admittance array is as follows:

[0089]

[0090] in, is the correction value of the diagonal element of the admittance matrix, Y is the node admittance matrix of the classical system, Y L Is the equivalent admittance Y Li The diagonal matrix of is expressed as follows:

[0091]

[0092] Considering the nodes inside the synchronous generator, it is assumed that the receiving system has a total of n nodes, where node i∈Ω1 (i is the potential node inside the synchronous generator, Ω1 is the set of all potential nodes inside the synchronous generator), i∈Ω2 (i is the node of the new energy system incorporated into the receiving system, Ω2 is the set of all nodes of the new energy system incorporated into the receiving system). At the same time, after the load is incorporated into the admittance array as a constant impedance, the network equation of the receiving system is:

[0093]

[0094] in, is the correction value of the diagonal element of the admittance array; is the set of internal potentials of all synchronous generators. For node i∈Ω1 (Ω1 is the set of internal potential nodes of all synchronous generators), the corresponding element is E i ″ is the potential inside the generator; The corresponding element is 0; is the set of node voltages. For node i∈Ω1, the element should be 0. The corresponding element is U i ; I is the total current of the new energy system and the synchronous generator. Thus:

[0095]

[0096] in, represents the set of potentials in all synchronous generators, represents the set of power network node voltages, K S is the column of the n-order identity matrix corresponding to i∈Ω1, is the vector of the known potential inside the synchronous generator, K U is the n-th order identity matrix corresponding to , U is the vector composed of unknown node voltages.

[0097] Similarly, the total current of the new energy system and the synchronous generator is expressed as follows:

[0098] I=K S I S +K N I N (6)

[0099] Where I is the total current of the new energy system and the synchronous generator, K S is the column of the n-order identity matrix corresponding to i∈Ω1; I S is the vector of injected currents of synchronous generator nodes; K N is the column of the n-order identity matrix corresponding to i∈Ω2; I N It is the vector of node current that the new energy system is integrated into the receiving system.

[0100] Therefore, the network equation of the receiving system can be written as follows:

[0101]

[0102] In step S30, determining the open circuit voltage and short circuit current of the node in the receiving system according to the network equation includes:

[0103] S301: Obtaining a vector consisting of a current of a synchronous generator at a node where the synchronous generator is located and a first voltage of the node when the synchronous generator is not incorporated into a new energy system;

[0104] S302: Determine the open circuit voltage according to a vector consisting of the synchronous generator current and the voltage;

[0105] S303: Acquire a second voltage of a node that is not incorporated into the new energy system;

[0106] S304: Determine the short-circuit current according to the synchronous generator current and the second voltage.

[0107] Specifically, for the node that needs to be calculated and connected to the energy system, after removing the equivalent admittance of its load from the admittance matrix, the voltage of the node is obtained as the open circuit voltage. For the converter node, after removing the equivalent current from the above equation, the solution process of the open circuit voltage is derived as follows:

[0108]

[0109] In the solution process, the unknown node voltage vector U and the synchronous generator node injection current vector I S is the unknown quantity, the vector I of the current injected by the new energy node N , the vector of the potential components in the known synchronous generator is a known quantity. So we have:

[0110]

[0111] Only one LU decomposition is required to obtain the value of the open circuit voltage of node i, which is obtained by the following formula:

[0112]

[0113] Among them, U i,oc represents the open circuit voltage at node i, represents the i-th row of the identity matrix, I S is the synchronous generator current of the node where the synchronous generator is located, and U is the vector composed of the first voltage of the node when it is not integrated into the new energy system.

[0114] When calculating the short-circuit current of node i, it is assumed that a new injection current is added to the node i, so that the voltage of node i is 0. Formula (7) is written as:

[0115]

[0116] Note that compared to the original form, The voltage at node i is not included. It also does not contain the i-th column of the identity matrix, e i represents the i-th column of the identity matrix, U i,oc represents the open circuit voltage of node i, I i,sc In this case, node i is short-circuited and its node voltage U i It is known that is 0, and formula (11) can be further written as:

[0117]

[0118] Therefore, the short-circuit current I i,sc Obtained by the following formula:

[0119]

[0120] Among them, I i,sc is the short-circuit current at node i, is the nth row of the identity matrix, is the second voltage of the node not incorporated into the new energy system, I S is the synchronous generator current at the node where the synchronous generator is located.

[0121] In step S50, for the calculation of the short-circuit ratio of the new energy system connected to the receiving end system, if there is only a single-circuit line connection, the corresponding single-feed short-circuit ratio calculation formula is:

[0122]

[0123] Where SCR is the single-feed short-circuit ratio, P Ni is the rated capacity of new energy; U i,oc represents the open circuit voltage of node i, I i,sc Represents the short-circuit current at node i.

[0124] In step S80, if a multi-circuit energy system is incorporated into the receiving system, the multi-infeed short-circuit ratio corresponding to node i is:

[0125]

[0126] Among them, U i,oc represents the open circuit voltage of node i, I i,sc Represents the short-circuit current of node i, MIIF ij It is expressed as the interaction factor between commutation busbar i and commutation busbar j, P Ni It is represented by the rated capacity of the new energy system connected to the commutation bus i, P Nj It represents the rated capacity of the new energy system connected to the commutation bus j;

[0127] In step S70, when multiple new energy systems are integrated into the receiving system, the network strength of the receiving system needs to be evaluated by using the multi-infeed short-circuit ratio. The calculation of the interaction factor is involved in the multi-infeed short-circuit ratio, which is defined as:

[0128]

[0129] MIIF is defined as: when the voltage of commutation bus i drops by about 1% through a parallel reactive element (e.g., a symmetrical three-phase reactor), the voltage change of commutation bus j is observed. The ratio of the voltage changes of the two is the multi-infeed interaction factor between buses i and j; ΔU i is the voltage change of commutation bus i, ΔUj is the voltage change of commutation bus j.

[0130] The equation (9) can be further linearized as follows:

[0131]

[0132] At the same time, the expression of the voltage change of the commutation bus i is as follows:

[0133]

[0134] The expression of the voltage change of commutation bus j is as follows:

[0135]

[0136] in, The diagonal elements of the power system admittance matrix are incorporated into Y Li The modified matrix after K U is the n-th order identity matrix corresponding to Column; K S K is the column of the n-order identity matrix corresponding to i∈Ω1; N is the column of the n-order identity matrix corresponding to i∈Ω2; ΔU j is the voltage change of commutation bus j, ΔU i is the voltage change of commutation bus i, is the i-th row of the identity matrix, is the jth row of the identity matrix; ΔU is the vector composed of the changes in the voltages of all unknown nodes; ΔI S is a vector consisting of the changes in the injected current of all synchronous generator nodes; ΔI N is the vector of the changes in the current injected into all new energy nodes; therefore, substituting formula (18) and formula (19) into formula (16) can obtain MIIF ij Calculated value.

[0137] If the current source model is a controlled current source, in I N Substitute it into the control equation. In particular, when the new energy node is considered to be a conventional constant current source, equation (17) can be further deduced as follows:

[0138]

[0139] Among them, MIIF ij is the interaction factor between commutation busbar i and commutation busbar j, is the j-th row of the identity matrix, is the i-th row of the identity matrix, e i represents the i-th column of the identity matrix, is the transpose of the corrected values ​​of the diagonal elements of the admittance matrix.

[0140] In order to verify the accuracy and efficiency of the method for calculating the short-circuit ratio and interaction factor of the receiving system of the new energy system integrated into the present invention, the method is verified on the New England 10-machine 39-node system, and an actual power system with more than 4000 nodes is used to evaluate the calculation results and calculation time.

[0141] Replace some synchronous machines of the 39-node system with DC inverter stations respectively, and test the system as follows Figure 3 As shown (taking node 34 as an example). In order to compare the accuracy of different methods, when testing each DC grid-connected node separately, its DC power is increased until the critical point of the power flow, and the short-circuit ratio under the critical state is calculated. When DC only transmits active power and the AC side line is considered to be a pure reactance, the value of the critical short-circuit ratio should be strictly 2. The short-circuit ratio of the grid-connected point is calculated by the method mentioned above and the traditional Thevenin equivalent impedance method, and the results are shown in Table 1.

[0142] Table 1 Comparison of short-circuit ratio solution results of 39-node test system

[0143]

[0144] The present invention is based on the definition of short-circuit ratio and is obtained strictly through an algorithm according to the system network parameters; while the traditional method performs Thevenin equivalent on the receiving end system, and the approximation in the model equivalent process will lead to a certain error in the result. As can be seen from Table 1, when solving the short-circuit ratio, the approximate calculation result of the traditional Thevenin equivalent impedance method has an error of about 2% compared with the strict algorithm proposed by the present invention.

[0145] Similarly, in the actual large power grid, two methods are used to calculate the short-circuit ratio of some new energy stations connected to the grid, and the difference in calculation time is compared. The results are shown in Tables 2 and 3.

[0146] Table 2 Comparison of actual power system short-circuit ratio solution results

[0147]

[0148] It can be seen that in actual power systems, the strict algorithm proposed by the present invention can reduce the error of about 3-5% in accuracy compared with the traditional Thevenin equivalent impedance approximation method.

[0149] Table 3 Solution time of two algorithms in actual power system

[0150]

[0151] As can be seen from Table 3, for large systems, the computational efficiency of this method can be improved by about 20% compared with traditional methods. And for power systems with larger networks and more nodes, this method will perform better in terms of computational time, and is suitable for large systems in engineering practice.

[0152] Compared with the prior art, the advantages of the present invention are:

[0153] First, in the process of solving the short-circuit ratio and interaction factor, a strict deduction is performed based on the definition formula without approximate calculation, and the current source model commonly used in new energy systems and flexible DC converters is taken into account, which greatly improves the calculation accuracy of the short-circuit current of multiple power electronic equipment connected to the receiving-end AC system.

[0154] Second, this method can be used for both the early planning of new energy system grid connection and the real-time monitoring of the network strength of the receiving system after grid connection. When used for planning, there is no need to perform system flow calculation, which further improves efficiency; when used for real-time monitoring, the flow results are introduced to improve the accuracy of the load equivalent impedance model.

[0155] Third, when calculating the short-circuit capacity and interaction factor, only one LU decomposition is required, and it is based on the actual network model without the need to perform the Thevenin equivalent on the receiving system. The calculation process is more intuitive and concise, and the relevant parameters can be monitored in real time during the operation of a given power grid.

[0156] The present application also provides a device for evaluating the stability of a receiving end system, such as Figure 3 As shown, the device comprises:

[0157] The first acquisition module 100 is used to obtain the correction value of the diagonal element of the admittance array of the receiving system, the set of internal potentials of all synchronous generators, the set of voltages of nodes in the receiving system when the new energy system is not incorporated, and the total current of the new energy system and the synchronous generator;

[0158] A first determination module 200 is used to determine the network equation of the receiving end system according to the correction value of the diagonal element of the admittance array, the set of internal potentials of all synchronous generators, the set of voltages of the nodes, and the total current of the new energy system and the synchronous generator;

[0159] A second determination module 300 is used to determine the open circuit voltage and short circuit current of the node in the receiving end system that has been incorporated into the new energy system according to the network equation;

[0160] A second acquisition module 300 is used to acquire the rated capacity of the new energy system;

[0161] A fourth determination module 400, configured to determine a single-feed short-circuit ratio according to the rated capacity, the open-circuit voltage and the short-circuit current;

[0162] The third acquisition module 500 is used to acquire the voltage conversion amount and current change amount after the node is incorporated into the new energy system;

[0163] The fifth determination module 600 is used to determine an interaction factor according to the voltage transformation amount and the current change amount; and determine a multi-infeed short-circuit ratio according to the rated capacity, the open-circuit voltage, the short-circuit current and the interaction factor.

[0164] The present application obtains the correction value of the diagonal element of the admittance array of the receiving system, the set of the internal potentials of all synchronous generators, the set of the voltages of the nodes in the receiving system when the new energy system is not incorporated, and the total current of the new energy system and the synchronous generators; determines the network equation of the receiving system according to the correction value of the diagonal element of the admittance array, the set of the internal potentials of all synchronous generators, the set of the voltages of the nodes, and the total current of the new energy system and the synchronous generators; determines the open-circuit voltage and short-circuit current of the nodes in the receiving system that have been incorporated into the new energy system according to the network equation; obtains the rated capacity of the new energy system; determines the single-feed short-circuit ratio according to the rated capacity, the open-circuit voltage and the short-circuit current; obtains the voltage transformation amount and the current change amount after the node is incorporated into the new energy system; determines the interaction factor according to the voltage transformation amount and the current change amount; determines the multi-feed short-circuit ratio according to the rated capacity, the open-circuit voltage, the short-circuit current and the interaction factor. The present application can intuitively compare the relative sizes of the capacities between the receiving system and the new energy system through the short-circuit ratio; the larger the short-circuit ratio, the better the static stability after the DC or new energy is connected to the receiving system; the smaller the interaction factor, the lower the degree of coupling between different DC transmission lines; thereby more accurately and efficiently guiding the planning and operation of the new energy grid connection.

[0165] Figure 4 FIG. 1 shows an internal structure diagram of a computer device in an embodiment. The computer device may be a terminal or a server. Figure 4 As shown, the computer device includes a processor, a memory and a network interface connected via a system bus. The memory includes a non-volatile storage medium and an internal memory. The non-volatile storage medium of the computer device stores an operating system and may also store a computer program. When the computer program is executed by the processor, the processor may implement a stability assessment method for the receiving end system. The internal memory may also store a computer program. When the computer program is executed by the processor, the processor may implement an age recognition method. Those skilled in the art will appreciate that Figure 4The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0166] In one embodiment, a computer device is provided, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor performs the following steps:

[0167] Obtaining the correction values ​​of the diagonal elements of the admittance array of the receiving system, the set of internal potentials of all synchronous generators, the set of voltages of nodes in the receiving system when the new energy system is not incorporated, and the total current of the new energy system and the synchronous generators;

[0168] Determine the network equation of the receiving-end system according to the correction value of the diagonal element of the admittance array, the set of the internal potentials of all the synchronous generators, the set of the voltages of the nodes, and the total current of the new energy system and the synchronous generators;

[0169] Determine the open circuit voltage and short circuit current of the node in the receiving end system that has been incorporated into the new energy system according to the network equation;

[0170] Obtaining the rated capacity of the new energy system;

[0171] Determine a single-feed short-circuit ratio according to the rated capacity, the open-circuit voltage and the short-circuit current;

[0172] Obtaining a voltage conversion amount and a current change amount after the node is incorporated into the new energy system;

[0173] Determining an interaction factor according to the voltage change amount and the current change amount;

[0174] A multi-infeed short-circuit ratio is determined according to the rated capacity, the open-circuit voltage, the short-circuit current and the interaction factor.

[0175] In one embodiment, a computer-readable storage medium is provided, storing a computer program, wherein when the computer program is executed by a processor, the processor performs the following steps:

[0176] Obtaining the correction values ​​of the diagonal elements of the admittance array of the receiving system, the set of internal potentials of all synchronous generators, the set of voltages of nodes in the receiving system when the new energy system is not incorporated, and the total current of the new energy system and the synchronous generators;

[0177] Determine the network equation of the receiving-end system according to the correction value of the diagonal element of the admittance array, the set of the internal potentials of all the synchronous generators, the set of the voltages of the nodes, and the total current of the new energy system and the synchronous generators;

[0178] Determine the open circuit voltage and short circuit current of the node in the receiving end system that has been incorporated into the new energy system according to the network equation;

[0179] Obtaining the rated capacity of the new energy system;

[0180] Determine a single-feed short-circuit ratio according to the rated capacity, the open-circuit voltage and the short-circuit current;

[0181] Obtaining a voltage conversion amount and a current change amount after the node is incorporated into the new energy system;

[0182] Determining an interaction factor according to the voltage change amount and the current change amount;

[0183] A multi-infeed short-circuit ratio is determined according to the rated capacity, the open-circuit voltage, the short-circuit current and the interaction factor.

[0184] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the program can be stored in a non-volatile computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0185] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0186] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A method for evaluating the stability of a receiving system, wherein the receiving system is an AC system incorporated into a new energy system, and the receiving system includes a synchronous generator, characterized in that: The method comprises: Obtaining the correction values ​​of the diagonal elements of the admittance array of the receiving system, the set of internal potentials of all synchronous generators, the set of voltages of nodes in the receiving system when the new energy system is not incorporated, and the total current of the new energy system and the synchronous generators; Determine the network equation of the receiving-end system according to the correction value of the diagonal element of the admittance array, the set of the internal potentials of all the synchronous generators, the set of the voltages of the nodes, and the total current of the new energy system and the synchronous generators; Determine the open circuit voltage and short circuit current of the node in the receiving end system that has been incorporated into the new energy system according to the network equation; Obtaining the rated capacity of the new energy system; Determine a single-feed short-circuit ratio according to the rated capacity, the open-circuit voltage and the short-circuit current; Obtaining a voltage conversion amount and a current change amount after the node is incorporated into the new energy system; Determining an interaction factor according to the voltage change amount and the current change amount; A multi-infeed short-circuit ratio is determined according to the rated capacity, the open-circuit voltage, the short-circuit current and the interaction factor.

2. The method for evaluating the stability of a receiving system according to claim 1, characterized in that: The correction values ​​of the diagonal elements of the admittance array are determined by the following steps: Obtaining the equivalent admittance of the receiving system and the node admittance matrix of the classical system; The correction values ​​of the diagonal elements of the admittance matrix are determined according to the equivalent admittance of the receiving system and the node admittance matrix of the classical system.

3. The method for evaluating the stability of a receiving system according to claim 2, characterized in that: The equivalent admittance is obtained by the following steps: Obtain node voltage, load power, active power and reactive power; The equivalent admittance is determined according to the voltage, load power, active power and reactive power.

4. The method for evaluating the stability of a receiving system according to claim 3, characterized in that: The equivalent admittance is obtained by the following formula: Among them, Y Li is the equivalent admittance at node i; U i is the voltage of node i; S Li is the load power of node i, P Li is the active power of node i, Q Li is the reactive power of node i, and j is the coefficient.

5. The method for evaluating the stability of a receiving system according to claim 2, characterized in that: The expression of the correction value of the diagonal element of the admittance array is as follows: in, is the correction value of the diagonal element of the admittance matrix, Y is the node admittance matrix of the classical system, Y L is the equivalent admittance Y Li The diagonal array of .

6. The method for evaluating the stability of a receiving system according to claim 1, characterized in that: Determining the open circuit voltage and short circuit current of the node in the receiving end system according to the network equation includes: Obtaining a vector consisting of a synchronous generator current of a node where the synchronous generator is located and a first voltage of the node when the synchronous generator is not incorporated into the new energy system; Determine the open circuit voltage according to a vector consisting of the synchronous generator current and the voltage; Acquiring a second voltage of a node that is not incorporated into the new energy system; The short-circuit current is determined based on the synchronous generator current and the second voltage.

7. The method for evaluating the stability of a receiving system according to claim 6, characterized in that: The open circuit voltage is obtained by the following formula: Among them, U i,oc represents the open circuit voltage at node i, represents the i-th row of the identity matrix, I S is the synchronous generator current of the node where the synchronous generator is located, and U is the vector composed of the first voltage of the node when it is not incorporated into the new energy system; The short-circuit current is obtained by the following formula: Among them, I i,sc is the short-circuit current at node i, is the nth row of the identity matrix, is the second voltage of the node not incorporated into the new energy system, I S is the synchronous generator current at the node where the synchronous generator is located.

8. A device for evaluating the stability of a receiving system, characterized in that: The device comprises: A first acquisition module is used to obtain the correction value of the diagonal element of the admittance array of the receiving system, the set of internal potentials of all synchronous generators, the set of voltages of nodes in the receiving system when the new energy system is not incorporated, and the total current of the new energy system and the synchronous generator; A first determination module is used to determine the network equation of the receiving end system according to the correction value of the diagonal element of the admittance array, the set of internal potentials of all synchronous generators, the set of voltages of the nodes and the total current of the new energy system and the synchronous generator; A second determination module is used to determine the open circuit voltage and short circuit current of the node in the receiving end system that has been incorporated into the new energy system according to the network equation; A second acquisition module is used to acquire the rated capacity of the new energy system; A fourth determination module, configured to determine a single-feed short-circuit ratio according to the rated capacity, the open-circuit voltage and the short-circuit current; A third acquisition module is used to acquire the voltage conversion amount and current change amount after the node is incorporated into the new energy system; The fifth determination module is used to determine the interaction factor according to the voltage transformation amount and the current change amount; and determine the multi-input short-circuit ratio according to the rated capacity, the open-circuit voltage, the short-circuit current and the interaction factor.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor is caused to perform the steps of the method according to any one of claims 1 to 7.

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