Evaluation method, system and equipment for improving transient voltage stability of receiving-end power grid by synchronous generator and medium

Abstract

The invention provides an evaluation method, system, equipment and medium for improving transient voltage stability of a receiving-end power grid by a synchronous generator, and belongs to the technical field of transient voltage stabilization of a power system, and the method comprises the steps: S1, carrying out the multi-port Thevenin equivalence of a receiving-end AC system from a DC conversion bus side and a new energy grid-connected bus side; s2, calculating a multi-infeed transient short circuit ratio of a direct current conversion bus and a multi-infeed transient short circuit ratio of a new energy grid-connected bus based on a receiving end alternating current system after multi-port Thevenin equivalence; s3, weights of different faults, the weight of the direct current conversion bus and the weight of the new energy grid-connected bus are determined based on the response of the receiving end alternating current system to the fault set, and the comprehensive short-circuit ratio of the direct current conversion bus and the comprehensive short-circuit ratio of the new energy grid-connected bus are obtained through calculation; s4, constructing an index system based on the comprehensive short-circuit ratio of the direct-current conversion bus, the comprehensive short-circuit ratio of the new energy grid-connected bus and the network loss of the receiving-end alternating-current system; and S5, based on the index system, combined with the subjective and objective combination weight and the TOPSIS improved by the foreground theory, carrying out comprehensive evaluation on the transient voltage level of the synchronous generator supporting receiving end alternating current system. According to the invention, the transient stability margin of the voltage of the direct-current conversion bus and the new energy grid-connected bus is improved, and the operation risks of direct-current locking and new energy unit off-network after power grid fault disturbance are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of transient voltage stabilization of power systems, and in particular to an evaluation method, system, equipment and medium for improving the transient voltage stability capability of a receiving-end power grid by a synchronous generator. Background Art

[0002] Due to the reverse distribution of renewable energy and load centers, the problem of large-scale clean energy transmission is currently solved through UHV DC transmission. The development and construction of new energy in the receiving power grid is rapid, and the peak output of new energy accounts for more than 50% of the power load at the same time. Therefore, the DC receiving power grid has or will present an operating scenario where multiple DC feed-ins and new energy coexist.

[0003] However, DC feed-in and new energy access have led to a large number of conventional generators being replaced in the receiving grid, reducing the dynamic reactive capacity of the load center and the voltage support capability. At the same time, the DC system not only does not provide reactive support during the fault, but also absorbs a large amount of reactive power from the AC system during the recovery process.

[0004] Therefore, finding a method that can both improve the transient voltage stability of the power grid and reduce the risk of DC lockout and off-grid operation of new energy units after a power grid fault disturbance is a technical problem that needs to be urgently solved by technical personnel in this field. Summary of the invention

[0005] In view of this, the present invention proposes a method, system, equipment and medium for evaluating the ability of a synchronous generator to improve the transient voltage stability of a receiving-end power grid, which can improve the transient stability margin of the DC commutation bus and the new energy grid-connected bus voltage, and reduce the operating risks of DC lockout and new energy unit disconnection after a power grid fault disturbance.

[0006] The technical solution of the present invention is achieved in this way:

[0007] In a first aspect, the present invention provides a method for evaluating the ability of a synchronous generator to improve the transient voltage stability of a receiving-end power grid, comprising the following steps:

[0008] S1, perform multi-port Thevenin equivalence on the receiving end AC system from the DC conversion bus side and the new energy grid-connected bus side respectively;

[0009] S2. Based on the receiving-end AC system after multi-port Thevenin equivalent, calculate the multi-infeed transient short-circuit ratio of the DC commutation bus and the multi-infeed transient short-circuit ratio of the renewable energy grid-connected bus;

[0010] S3. Determine the weights of different faults, the weight of the DC commutation bus, and the weight of the renewable energy grid-connected bus based on the response of the receiving-end AC system to the fault set, and calculate the comprehensive short-circuit ratio of the DC commutation bus and the comprehensive short-circuit ratio of the renewable energy grid-connected bus;

[0011] S4. Construct an index system based on the comprehensive short-circuit ratio of the DC commutation bus, the comprehensive short-circuit ratio of the new energy grid-connected bus, and the network loss of the receiving-end AC system;

[0012] S5. Based on the index system and combined with the subjective and objective combined weights and the improved TOPSIS of prospect theory, a comprehensive evaluation is conducted on the transient voltage level of the AC system at the receiving end of the synchronous generator support.

[0013] Based on the above technical solution, preferably, step S3 specifically includes:

[0014] S31. Establish a power flow analysis and transient stability calculation model of the receiving-end power grid in the PSD-BPA power system analysis program, perform transient stability simulation calculation of the power grid based on the receiving-end power grid and the fault set, and obtain transient voltage data of the node; wherein the receiving-end power grid includes the receiving-end AC system, DC conversion bus, new energy grid-connected bus and synchronous generator;

[0015] S32, calculating a transient stability margin index based on a voltage transient response curve of a node;

[0016] S33, weighting different faults in the fault set, the DC commutation bus and the new energy grid-connected bus, and calculating the weights of different faults and the weights of different buses;

[0017] S34. The binomial coefficient method is used to weight the transient stability margin index of the bus voltage response to different fault disturbances, and the comprehensive short-circuit ratio under the fault set is calculated based on the weights of different faults and the weights of different buses.

[0018] On the basis of the above technical solution, preferably, the transient stability margin index is calculated using a multi-binary table method, specifically including:

[0019] Establish bus voltage drop below a certain voltage value V crk Duration T crk The multi-binary table (V crk , T crk );

[0020] Determine the weight coefficient K of the kth voltage drop based on the multi-binary table k ;

[0021] The transient voltage stability margin of the bus based on the multi-binary table is calculated according to the weight coefficient. The calculation formula is:

[0022]

[0023] Where η represents the transient voltage stability margin of the bus based on the multi-binary table, V min Indicates the lowest value of bus voltage during fault, VN Indicates the rated voltage of the busbar, k indicates the number of voltage drop, K k represents the weight coefficient of the kth voltage drop, T cr,k Indicates that the bus voltage drops below the voltage value V crk Duration, V cr,k represents the voltage threshold of the kth voltage drop, V cr,k-1 represents the voltage threshold of the k-1th voltage drop, K 1 Represents the weight coefficient of the first voltage drop, V cr,1 Indicates the voltage threshold of the first voltage drop, V R Indicates the recovery level of the bus voltage after the fault ends.

[0024] On the basis of the above technical solution, preferably, the weights of the different faults and the weights of the different buses are calculated as follows:

[0025]

[0026] Among them, W fy represents the weight of different faults, x represents the bus number, y represents the fault number, η xy represents the transient voltage stability margin of bus x to the yth fault, W Bx Indicates the weights of different buses.

[0027] On the basis of the above technical solution, preferably, the calculation formula of the comprehensive short-circuit ratio under the fault set is:

[0028] K WMITSCR =∑ y ∑ x W fy W Bx K MITSCR ;

[0029] K WMITSCR-N =∑ y ∑ x W fy W Bx K MITSCR-N ;

[0030] Among them, K WMITSCR Indicates the comprehensive short-circuit ratio of the DC commutation bus, K MITSCR K represents the transient short-circuit ratio of the multi-infeed DC commutation busbar. WMITSCR-N Indicates the comprehensive short-circuit ratio of the new energy grid-connected busbar, K MITSCR-N It represents the transient short-circuit ratio of multiple infeeds in the renewable energy grid-connected node.

[0031] More preferably, the index system includes a first sensitivity, a second sensitivity and a third sensitivity, wherein the first sensitivity is the sensitivity of the comprehensive short-circuit ratio of the DC commutation bus to the change in the generator power factor, the second sensitivity is the sensitivity of the comprehensive short-circuit ratio of the new energy grid-connected bus to the change in the generator power factor, and the third sensitivity is the sensitivity of the receiving-end AC system network loss to the change in the generator power factor; wherein,

[0032] The calculation formula of the first sensitivity is:

[0033]

[0034] The calculation formula of the second sensitivity is:

[0035]

[0036] The calculation formula of the third sensitivity is:

[0037]

[0038] Where K WMITSCR is the comprehensive short-circuit ratio of the DC commutation bus, cosθ k is the power factor of the kth synchronous generator, K WMITSCR-N is the comprehensive short-circuit ratio of the new energy grid-connected busbar, P loss It is the network loss of the receiving end AC system.

[0039] On the basis of the above technical solution, preferably, step S5 specifically includes:

[0040] S51, forming a data matrix according to the first sensitivity, the second sensitivity and the third sensitivity;

[0041] S52, establishing a judgment matrix of the first sensitivity, the second sensitivity and the third sensitivity, and based on the data matrix, respectively calculating the comprehensive weights of the first sensitivity, the second sensitivity and the third sensitivity in the judgment matrix; the comprehensive weights include subjective weights, objective weights and subjective and objective combined weights;

[0042] S53. Based on subjective weights, objective weights and subjective and objective combined weights, the synchronous generators are evaluated and ranked using TOPSIS improved by prospect theory, and the ability of different synchronous generators in the receiving-end AC system to improve the transient voltage stability of the receiving-end power grid is obtained.

[0043] In a second aspect, the present invention provides an evaluation system for improving the transient voltage stability capability of a receiving-end power grid by a synchronous generator, using the evaluation method described above, the system comprising:

[0044] A multi-port Thevenin equivalent module is configured to perform multi-port Thevenin equivalent on the receiving-end AC system from the DC conversion bus side and the new energy grid-connected bus side respectively;

[0045] A short-circuit ratio calculation module is configured to calculate the multi-infeed transient short-circuit ratio of the DC commutation bus and the multi-infeed transient short-circuit ratio of the new energy grid-connected bus based on the receiving-end AC system after multi-port Thevenin equivalent;

[0046] A comprehensive short-circuit ratio calculation module is configured to determine the weights of different faults, the weight of the DC commutation bus and the weight of the renewable energy grid-connected bus based on the response of the receiving-end AC system to the fault set, and calculate the comprehensive short-circuit ratio of the DC commutation bus and the comprehensive short-circuit ratio of the renewable energy grid-connected bus;

[0047] An indicator system construction module is configured to construct an indicator system based on the comprehensive short-circuit ratio of the DC commutation bus, the comprehensive short-circuit ratio of the new energy grid-connected bus, and the network loss of the receiving-end AC system;

[0048] The comprehensive evaluation module is configured as TOPSIS based on the index system and combined with subjective and objective combined weights and prospect theory to comprehensively evaluate the transient voltage level of the AC system at the receiving end of the synchronous generator support.

[0049] In a third aspect, the present invention provides an electronic device, characterized in that it comprises: at least one processor, at least one memory, a communication interface and a bus, wherein:

[0050] The processor, memory, and communication interface communicate with each other via the bus;

[0051] The memory stores program instructions that can be executed by the processor, and the processor calls the program instructions to implement the evaluation method as described above.

[0052] In a fourth aspect, the present invention provides a computer-readable storage medium, characterized in that the computer-readable storage medium stores computer instructions, and the computer instructions enable the computer to implement the evaluation method as described above.

[0053] The evaluation method, system, device and medium of the present invention have the following beneficial effects compared with the prior art:

[0054] (1) By calculating the multi-input transient short-circuit ratio of the DC commutation bus and the renewable energy grid-connected bus, combined with the receiving end AC system network loss, a comprehensive evaluation index system was established to evaluate and rank the transient voltage stability capabilities of different synchronous generators in the system, improve the transient stability margin of the DC commutation bus and the renewable energy grid-connected bus voltage, reduce the operating risks of DC lockout and renewable energy unit disconnection after grid fault disturbance, and take into account the impact of the steady-state reactive power regulation of the generator on the network loss, providing a basis for unit selection for improving the transient voltage stability of the system by using the reactive power regulation of the synchronous generator;

[0055] (2) Based on the power network analysis theory and multi-infeed short-circuit ratio, combined with the electromechanical transient simulation of the power system, the multi-infeed transient short-circuit ratio of the DC commutation bus and the renewable energy grid-connected bus is calculated, and the transient voltage stability of the receiving-end AC system during the fault process is quantified, realizing the assessment of the receiving-end AC system's ability to withstand DC feed-in and renewable energy access during the transient process;

[0056] (3) The comprehensive transient short-circuit ratio is calculated by weighting the fault set and the bus. The weighted method uses the minimum value of the node voltage drop, the specified threshold duration of the voltage drop, and the voltage recovery level. Compared with the single binary table and the direct calculation of the transient voltage integral area, it can more accurately calculate the bus voltage transient margin while improving the calculation efficiency, thereby realizing the weight calculation more accurately and efficiently. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] 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.

[0058] Figure 1 is a flow chart of the evaluation method of the present invention;

[0059] Figure 2 A schematic diagram of a busbar transient voltage drop multi-binary table and weight coefficients of the evaluation method of the present invention;

[0060] Figure 3 The improved IEEE 30-node system wiring diagram of the evaluation method of the present invention;

[0061] Figure 4 The equivalent diagram of the receiving-end AC system viewed from the DC commutation busbar according to the evaluation method of the present invention;

[0062] Figure 5The transient voltage variation curve of converter bus node 3 of the improved IEEE 30-node system for the evaluation method of the present invention under typical faults. Specific embodiments

[0063] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0064] As can be understood by those skilled in the art, the synchronous generator, as an important regulation resource in the system, can not only fill the active power deficit caused by DC faults, but also provide reactive power support for the system and improve the transient voltage stability of the receiving-end power grid.

[0065] As Figure 1 shown, the present invention provides an evaluation method for a synchronous generator to improve the transient voltage stability ability of a receiving-end power grid, including the following steps:

[0066] S1. Perform multi-port Thevenin equivalent on the receiving-end AC system from the DC converter bus side and the new energy grid-connected bus side respectively.

[0067] Specifically, in an embodiment of the present application, it is assumed that there are N nodes in the receiving-end AC system, where there are m DC converter buses and n new energy grid-connected buses, where m < N and n < N;

[0068] Taking the DC converter bus as an example, assume that the DC converter bus m k (k < N) is the kth bus, then its corresponding N×1-dimensional node-port vector is:

[0069]

[0070] Among them, M k represents the 1×N-dimensional node-port vector corresponding to the kth DC converter bus;

[0071] Arranging all the node-port correlation vectors in columns together constitutes the N×m-dimensional node-port correlation matrix of the DC converter bus:

[0072] M D =[M 1 M 2 …M m (2)

[0073] Among them, M D represents the node-port correlation matrix of the DC converter bus, and M 1represents the node-port vector corresponding to the first DC commutation bus, M 2 represents the node-port vector corresponding to the second DC commutation bus, M m represents the node-port vector corresponding to the mth DC commutation bus;

[0074] From the perspective of m DC conversion buses, the m×m-order equivalent node impedance matrix of the multi-port Thevenin equivalent circuit of the receiving-end AC system is:

[0075]

[0076] Among them, Z eq represents the m×m-order equivalent node impedance matrix of the multi-port Thevenin equivalent circuit of the receiving-end AC system viewed from the m DC conversion buses, Indicates M D The transposed matrix, Z represents the node impedance matrix of the original receiving end AC system, M D Represents the node-port association matrix of the DC commutation bus.

[0077] Assume that the original network equation of the receiving AC system is:

[0078]

[0079] Where Y represents the node admittance matrix, represents the node voltage column vector, represents the node injection current column vector;

[0080] Then the Thevenin equivalent electromotive force is:

[0081]

[0082] in, represents the Thevenin equivalent electromotive force, Indicates M D The transposed matrix of Represents the node voltage column vector of the original receiving end AC system;

[0083] Therefore, the multi-port Thevenin equivalent circuit equation is:

[0084]

[0085] in, It represents the voltage on the DC bus. Indicates the current on the DC bus.

[0086] It can be understood that the multi-port Thevenin equivalent circuit equation viewed from the perspective of n new energy conversion busbars is the same and will not be elaborated here.

[0087] S2. Based on the receiving-end AC system after multi-port Thevenin equivalent, calculate the multi-infeed transient short-circuit ratio of the DC commutation bus and the multi-infeed transient short-circuit ratio of the renewable energy grid-connected bus;

[0088] Specifically, the multi-infeed short-circuit ratio of the DC commutation bus node i' is defined as:

[0089]

[0090] in, represents the short-circuit ratio of multiple infeeds at the DC commutation bus node i', S aci’ represents the short-circuit capacity of the receiving AC system at the DC conversion bus node i', P deqi’ It represents the equivalent DC rated power at the DC commutation bus node i', U Ni’ represents the average rated voltage of the DC bus node i', I aci’ represents the three-phase short-circuit current of the DC commutation bus node i', P dNi’ represents the rated power of the DC system of the converter station at the DC converter bus node i', i' represents the specific DC converter bus node for which the multi-infeed short-circuit ratio is being calculated, j' represents other DC converter bus nodes except the DC converter bus node i', and Z i’j’ represents the i'th row and j'th column element of the equivalent node matrix viewed from the DC commutation bus, Z i’i’ represents the self-impedance of the equivalent receiving AC system node i', Z i’j’ represents the mutual impedance between the DC commutation bus node i' and the DC commutation bus node j', P dNj’ Represents the rated power of the DC system of the converter station at node j'.

[0091] In an embodiment of the present application, it is assumed that at a certain moment, a node in the receiving-end AC system fails, causing a voltage drop. At this time, the short-circuit current of the commutation bus node i' is:

[0092]

[0093] Among them, I aci’ It represents the three-phase short-circuit current of the DC commutation bus node i', U Ni’ represents the average rated voltage of the DC bus node i', Z i’i’ represents the self-impedance of the DC commutation bus node i';

[0094] Substituting equation (5) into equation (7) yields a practical calculation formula for the transient short-circuit ratio of multiple infeeds at the DC commutation bus node i':

[0095]

[0096] in, represents the transient short-circuit ratio of multiple infeeds at the DC commutation bus node i', Z Si’i’ It represents the self-impedance of the DC bus node i' when all the new energy sources in the system are open after the fault occurs, Z NEi’i’ It represents the self-impedance of the DC commutation bus node i' when all synchronous generators in the system are open after a fault occurs.

[0097] Since a fault in a node in the system will change the voltage and injected current of each node, the short-circuit impedance of each node will change accordingly. Therefore, it is necessary to correct the self-impedance of the receiving AC system node in real time according to the system simulation calculation results.

[0098] S3. Determine the weights of different faults, the weight of the DC commutation bus and the weight of the renewable energy grid-connected bus based on the response of the receiving AC system to the fault set, and calculate the comprehensive short-circuit ratio of the DC commutation bus and the comprehensive short-circuit ratio of the renewable energy grid-connected bus.

[0099] Specifically, step S3 specifically includes:

[0100] S31. Establish a power flow analysis and transient stability calculation model of the receiving-end power grid in the PSD-BPA power system analysis program, perform transient stability simulation calculation of the power grid based on the receiving-end power grid and the fault set, and obtain transient voltage data of the node; wherein the receiving-end power grid includes the receiving-end AC system, DC conversion bus, new energy grid-connected bus and synchronous generator;

[0101] S32, calculating a transient stability margin index based on a voltage transient response curve of a node;

[0102] S33, weighting different faults in the fault set, the DC commutation bus and the new energy grid-connected bus, and calculating the weights of different faults and the weights of different buses;

[0103] S34. The binomial coefficient method is used to weight the transient stability margin index of the bus voltage response to different fault disturbances, and the comprehensive short-circuit ratio under the fault set is calculated according to the weights of different faults and different buses.

[0104] This application is based on power network analysis theory and multi-infeed short-circuit ratio, combined with power system electromechanical transient simulation to calculate the multi-infeed transient short-circuit ratio of the DC commutation bus and the renewable energy grid-connected bus, quantifies the transient voltage stability of the receiving-end AC system during a fault, and realizes the evaluation of the receiving-end AC system's ability to withstand DC feed-in and renewable energy access during a transient process.

[0105] In one embodiment of the present application, the equivalent grid-connected capacity of the new energy grid-connected node i is:

[0106]

[0107] Among them, Seqi represents the equivalent grid-connected capacity of the renewable energy grid-connected node i, S i represents the capacity of the renewable energy connected to the renewable energy grid node i, S j represents the capacity of the renewable energy connected to the renewable energy grid node j, U i Represents the voltage of the new energy grid-connected node i, U j represents the voltage of the new energy grid-connected node j, Z ij represents the mutual impedance between the new energy grid-connected node i and the new energy grid-connected node j, Z ii represents the self-impedance of the new energy grid-connected node i;

[0108] The practical calculation formula for the transient short-circuit ratio of multiple feed-in nodes i in the renewable energy grid is:

[0109]

[0110] Among them, K MITSCR-N represents the transient short-circuit ratio of multiple feed-in nodes i connected to the renewable energy grid, U N Indicates the rated voltage of the renewable energy grid-connected node i, U Ti It represents the voltage of the new energy grid-connected node i at a certain moment after the fault occurs, U Tj It represents the voltage of the new energy grid-connected node j at a certain moment after the fault occurs, Z Tii It represents the self-impedance of the renewable energy grid-connected node i after the fault occurs.

[0111] like Figure 2 As shown, the horizontal axis is time t, and the vertical axis is voltage V. In one embodiment of the present application, the transient stability margin index is calculated using a multi-binary table method, specifically including:

[0112] Establish bus voltage drop below a certain voltage value V crk Duration T crk The multi-binary table (V crk , T crk );

[0113] Determine the weight coefficient K of the kth voltage drop based on the multi-binary table k ; The formula is:

[0114]

[0115] Among them, K n Represents the weight coefficient of the nth voltage drop, V N Indicates the rated voltage of the busbar, V cr,n Indicates the voltage threshold of the nth voltage drop, T cr,n Indicates that the nth voltage drops below the voltage threshold V cr,n Duration of

[0116] The transient voltage stability margin of the bus based on the multi-binary table is calculated according to the weight coefficient. The calculation formula is:

[0117]

[0118] Where η represents the transient voltage stability margin of the bus based on the multi-binary table, V min Indicates the lowest value of bus voltage during fault, V N Indicates the rated voltage of the busbar, k indicates the number of voltage drop, K k represents the weight coefficient of the kth voltage drop, T cr,k Indicates that the bus voltage drops below the voltage value V crk Duration, V cr,k represents the voltage threshold of the kth voltage drop, V cr,k-1 represents the voltage threshold of the k-1th voltage drop, K 1 Represents the weight coefficient of the first voltage drop, V cr,1 Indicates the voltage threshold of the first voltage drop, V R Indicates the recovery level of the bus voltage after the fault ends.

[0119] Furthermore, the weights of the different faults and the weights of the different buses are calculated as follows:

[0120]

[0121]

[0122] Among them, W fy represents the weight of different faults, x represents the bus number, y represents the fault number, η xy represents the transient voltage stability margin of bus x to the yth fault, W Bx Indicates the weights of different buses.

[0123] In one embodiment of the present application, the fault includes a three-phase short circuit, a two-phase short circuit, a single-phase short circuit, etc.

[0124] Furthermore, the calculation formula of the comprehensive short-circuit ratio under the fault set is:

[0125] K WMITSCR =∑ y ∑ x W fy W Bx K MITSCR (16)

[0126] K WMITSCR-N =∑ y ∑ x W fy W Bx KMITSCR-N (17)

[0127] Among them, K WMITSCR Indicates the comprehensive short-circuit ratio of the DC commutation bus, K MITSCR K represents the transient short-circuit ratio of the multi-infeed DC commutation busbar. WMITSCR-N Indicates the comprehensive short-circuit ratio of the new energy grid-connected busbar, K MITSCR-N It represents the transient short-circuit ratio of multiple infeeds in the renewable energy grid-connected node.

[0128] The present application calculates the comprehensive transient short-circuit ratio through fault set and bus weighted calculation. The weighted method used utilizes the minimum value of node voltage drop, the specified threshold duration of voltage drop and the voltage recovery level. Compared with a single binary table and direct calculation of the transient voltage integral area, it can more accurately calculate the transient margin of the bus voltage while improving the calculation efficiency, thereby realizing weight calculation more accurately and efficiently.

[0129] S4. Construct an index system based on the comprehensive short-circuit ratio of the DC commutation bus, the comprehensive short-circuit ratio of the new energy grid-connected bus and the network loss of the receiving-end AC system.

[0130] Specifically, the index system includes a first sensitivity, a second sensitivity and a third sensitivity. The first sensitivity is the sensitivity of the comprehensive short-circuit ratio of the DC commutation bus to the change of the generator power factor. The second sensitivity is the sensitivity of the comprehensive short-circuit ratio of the new energy grid-connected bus to the change of the generator power factor. The third sensitivity is the sensitivity of the receiving end AC system network loss to the change of the generator power factor.

[0131] The calculation formula of the first sensitivity is:

[0132]

[0133] The calculation formula of the second sensitivity is:

[0134]

[0135] The calculation formula of the third sensitivity is:

[0136]

[0137] Where K WMITSCR is the comprehensive short-circuit ratio of the DC commutation bus, cosθ k is the power factor of the kth synchronous generator, K WMITSCR-N is the comprehensive short-circuit ratio of the new energy grid-connected busbar, P loss It is the network loss of the receiving end AC system.

[0138] S5. Based on the index system and combined with the subjective and objective combined weights and the improved TOPSIS of prospect theory, a comprehensive evaluation is conducted on the transient voltage level of the AC system at the receiving end of the synchronous generator support.

[0139] Furthermore, step S5 specifically includes:

[0140] S51, forming a data matrix according to the first sensitivity, the second sensitivity and the third sensitivity;

[0141] S52, establishing a judgment matrix of the first sensitivity, the second sensitivity and the third sensitivity, and based on the data matrix, respectively calculating the comprehensive weights of the first sensitivity, the second sensitivity and the third sensitivity in the judgment matrix; the comprehensive weights include subjective weights, objective weights and subjective and objective combined weights;

[0142] S53. Based on subjective weights, objective weights and subjective and objective combined weights, the synchronous generators are evaluated and ranked using TOPSIS improved by prospect theory, and the ability of different synchronous generators in the receiving-end AC system to improve the transient voltage stability of the receiving-end power grid is obtained.

[0143] In one embodiment of the present application, the rows of the initial data matrix represent indicators, and the columns represent different synchronous generators.

[0144] In one embodiment of the present application, a judgment matrix R of three indicators is established based on the opinions of L experts, and the calculation formula of the subjective weight of each indicator in the judgment matrix is ​​as follows:

[0145]

[0146] Among them, δ l represents the subjective weight of the lth indicator, R ln represents the element in the lth row and nth column of the judgment matrix, and L represents the L-bit expert advice;

[0147] Standardize the initial data matrix X to obtain the normalized data matrix X s , and then calculate the objective weight of each indicator:

[0148]

[0149] Among them, I τ represents the information entropy of the τth index, p μω Represents the standardized data matrix X s The weight of the element in the μth row and the ωth column, x rt Represents the standardized data matrix X s The element in the rth row and τth column, v τ represents the information utility value of the τth indicator, ε τrepresents the objective weight of the τth indicator, v u represents the information utility value of the u-th indicator;

[0150] The calculation formula of subjective and objective combined weight is:

[0151]

[0152] Among them, w τ represents the subjective and objective combined weight of the τth indicator, δ r represents the subjective weight of the rth indicator, δ τ represents the subjective weight of the τth indicator, ε r represents the objective weight of the rth indicator, ε τ Represents the objective weight of the τth indicator.

[0153] In one embodiment of the present application, the TOPSIS improved by prospect theory specifically includes:

[0154] Give the expected value of each indicator for m indicators to form the expected matrix Q;

[0155] Based on the original data matrix X, the index value and the expected matrix are standardized. The formula is as follows:

[0156]

[0157] Among them, x eq Represents the element value of the e-th row and q-th column in the standardized original data matrix X, q g represents the element value of the g-th column in the standardized expectation matrix Q, Q h represents the original element value of the hth column in the expected matrix Q;

[0158] Calculate the loss matrix S, the calculation formula is as follows:

[0159]

[0160] Among them, s cy Represents the element value of the cth row and yth column in the loss matrix S;

[0161] The loss matrix S is used to calculate the prospect value matrix V, and the calculation formula is:

[0162]

[0163] Among them, V fq represents the element value of the fth row and qth column in the prospect value matrix V, λ represents the loss aversion coefficient, α represents the return risk coefficient, and β represents the loss risk coefficient.

[0164] In one embodiment of the present application, when the risk coefficient α is 0.88 and the loss aversion coefficient β is 2.25, the analysis result of the prospect theory is closer to the decision result caused by the actual decision maker's psychology of gains and losses.

[0165] In one embodiment of the present application, the specific steps of TOPSIS improved by prospect theory are as follows:

[0166] First, positive and negative rational points are selected. The positive ideal point and negative ideal point of the dth indicator are calculated as follows:

[0167]

[0168] in, represents the positive ideal point of the dth index, represents the negative ideal point of the dth index, V sd Represents the element in the sth row and dth column of the prospect value matrix V;

[0169] For the zth synchronous generator, calculate its distance from the positive ideal point and the negative ideal point:

[0170]

[0171] in, represents the weighted Euclidean distance between the zth synchronous generator and the positive ideal point, w τ represents the weight of the τth indicator, represents the weighted Euclidean distance between the i-th synchronous generator and the negative ideal point;

[0172] According to the distance of each solution from the positive ideal point and the negative ideal point, the closeness of each solution can be calculated and sorted:

[0173]

[0174] Among them, d z Indicates the relative proximity of the zth synchronous generator.

[0175] This application calculates the multi-input transient short-circuit ratio of the DC commutation bus and the new energy grid-connected bus, and establishes a comprehensive evaluation index system in combination with the receiving-end AC system network loss, thereby realizing the evaluation and ranking of the transient voltage stability improvement capabilities of different synchronous generators in the system, improving the transient stability margin of the DC commutation bus and the new energy grid-connected bus voltage, and reducing the operating risks of DC lockout and new energy unit disconnection after power grid fault disturbances. At the same time, the influence of the steady-state reactive power regulation of the generator on the network loss is taken into account, providing a basis for unit selection for improving the transient voltage stability of the system by using the reactive power regulation of the synchronous generator.

[0176] In one embodiment of the present application, in order to verify the evaluation method of a synchronous generator of the present invention for improving the transient voltage stability capability of a receiving-end power grid with multiple DC feeds and renewable energy sources, a simulation study was performed using an improved IEEE 30-node system example.

[0177] like Figure 3 As shown, compared with the standard IEEE30 node system, in the improved IEEE30 node system provided by the present invention, the synchronous generators at nodes 11 and 13 are replaced with wind turbines, and a photovoltaic power station is added at node 9. Two DC lines are fed in at nodes 3 and 7. The capacities of the DC lines and the new energy units are shown in Table 1. In addition, the capacity of the synchronous generators at nodes 1, 2, 5 and 8 is 300MW, and the initial power factor is 0.9. It can be seen that the improved IEEE30 node system is a typical receiving-end power grid with multiple DC feeds and new energy access.

[0178] like Figure 4 As shown, taking the DC commutation bus as an example, the equivalent system after the multi-port Thevenin equivalent is performed on the receiving-end AC system of the multi-input DC receiving-end power grid viewed from the commutation bus, the rated power of the DC line and the capacity of the new energy unit are shown in Table 1:

[0179] Table 1

[0180]

[0181] The improved IEEE 30-bus system power flow analysis and transient stability calculation model is established in PSD-BPA, and the transient stability simulation calculation of the power grid is performed based on typical faults. The selected typical faults are: {three-phase short circuit, single-phase short circuit, two-phase short circuit, two-phase to ground short circuit, three-phase line break, two-phase line break, single-phase line break, DC blocking, DC power reverse}. Taking the commutation bus node 3 as an example, the transient voltage change curve of node 3 under different faults is shown in the figure below: Figure 5 As shown, the horizontal axis is time, the unit is cycle, and the vertical axis is voltage, the unit is per unit (pu).

[0182] According to the simulation results, the weights of different serious faults and the commutation bus and the new energy grid-connected bus are calculated as shown in Tables 2 and 3.

[0183] Table 2

[0184]

[0185] Table 3

[0186] Busbar Node 3 Node 7 Node 9 Node 11 Node 13 Weight value 0.4892 0.5108 0.3475 0.3075 0.3450

[0187] It can be seen from Table 2 that the weight values ​​of three-phase short circuit, two-phase short circuit and two-phase to ground short circuit are relatively high, and have a greater impact on the transient voltage stability of the system, while the weight values ​​of DC faults such as DC blocking and DC power reversal are relatively small. This is because the system has sufficient active backup and reactive power support capabilities, so the impact of DC faults on the transient voltage stability of the system is smaller than that of three-phase short circuit and two-phase short circuit faults.

[0188] The various index values ​​of different synchronous generators are calculated by combining the weight values ​​of different faults and different buses as shown in Table 4. Dk and S Nk They are the sensitivity of the commutation bus multi-feed transient short-circuit ratio to the generator power factor change and the sensitivity of the new energy grid-connected bus multi-feed transient short-circuit ratio to the generator power factor change, both of which are better indicators as they are larger; S Lk It is the sensitivity of the receiving-end AC system loss to the change of the generator power factor. The smaller the better.

[0189] Table 4

[0190] Node 1 Node 2 Node 5 Node 8 <![CDATA[S Dk ]]> 5.32 7.15 6.03 6.67 <![CDATA[S Nk ]]> 7.46 9.14 7.21 8.94 <![CDATA[S Lk ]]> 21.75 23.79 19.86 20.37

[0191] According to the index values, the comprehensive evaluation results are: node 2> node 8> node 5> node 1. That is, the synchronous generator at node 2 has a stronger ability to improve the transient voltage stability of the system.

[0192] The present application provides an evaluation system for improving the transient voltage stability capability of a receiving-end power grid by a synchronous generator, using the above-mentioned evaluation method, including:

[0193] A multi-port Thevenin equivalent module is configured to perform multi-port Thevenin equivalent on the receiving-end AC system from the DC conversion bus side and the new energy grid-connected bus side respectively;

[0194] A short-circuit ratio calculation module is configured to calculate the multi-infeed transient short-circuit ratio of the DC commutation bus and the multi-infeed transient short-circuit ratio of the new energy grid-connected bus based on the receiving-end AC system after multi-port Thevenin equivalent;

[0195] A comprehensive short-circuit ratio calculation module is configured to determine the weights of different faults, the weight of the DC commutation bus and the weight of the renewable energy grid-connected bus based on the response of the receiving-end AC system to the fault set, and calculate the comprehensive short-circuit ratio of the DC commutation bus and the comprehensive short-circuit ratio of the renewable energy grid-connected bus;

[0196] An indicator system construction module is configured to construct an indicator system based on the comprehensive short-circuit ratio of the DC commutation bus, the comprehensive short-circuit ratio of the new energy grid-connected bus, and the network loss of the receiving-end AC system;

[0197] The comprehensive evaluation module is configured as TOPSIS based on the index system and combined with subjective and objective combined weights and prospect theory to comprehensively evaluate the transient voltage level of the AC system at the receiving end of the synchronous generator support.

[0198] The present application provides an electronic device, comprising: at least one processor, at least one memory, a communication interface and a bus; wherein the processor, memory, and communication interface communicate with each other through the bus; the memory stores program instructions that can be executed by the processor, and the processor calls the program instructions to implement the evaluation method described above.

[0199] The present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer instructions, and the computer instructions enable the computer to implement the evaluation method as described above.

[0200] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for evaluating the ability of a synchronous generator to improve the transient voltage stability of a receiving-end power grid, characterized in that: The following steps are involved: S1, perform multi-port Thevenin equivalence on the receiving end AC system from the DC conversion bus side and the new energy grid-connected bus side respectively; S2. Based on the receiving-end AC system after multi-port Thevenin equivalent, calculate the multi-infeed transient short-circuit ratio of the DC commutation bus and the multi-infeed transient short-circuit ratio of the renewable energy grid-connected bus; S3. Determine the weights of different faults, the weight of the DC commutation bus, and the weight of the renewable energy grid-connected bus based on the response of the receiving-end AC system to the fault set, and calculate the comprehensive short-circuit ratio of the DC commutation bus and the comprehensive short-circuit ratio of the renewable energy grid-connected bus; S4. Construct an index system based on the comprehensive short-circuit ratio of the DC commutation bus, the comprehensive short-circuit ratio of the new energy grid-connected bus, and the network loss of the receiving-end AC system; S5. Based on the index system and combined with the subjective and objective combined weights and the improved TOPSIS of prospect theory, a comprehensive evaluation is conducted on the transient voltage level of the AC system at the receiving end of the synchronous generator support.

2. The method for evaluating the ability of a synchronous generator to improve the transient voltage stability of a receiving-end power grid as claimed in claim 1, characterized in that: Step S3 specifically includes: S31. Establish a power flow analysis and transient stability calculation model of the receiving-end power grid in the PSD-BPA power system analysis program, perform transient stability simulation calculation of the power grid based on the receiving-end power grid and the fault set, and obtain transient voltage data of the node; wherein the receiving-end power grid includes the receiving-end AC system, DC conversion bus, new energy grid-connected bus and synchronous generator; S32, calculating a transient stability margin index based on a voltage transient response curve of a node; S33, weighting different faults in the fault set, the DC commutation bus and the new energy grid-connected bus, and calculating the weights of different faults and the weights of different buses; S34. The binomial coefficient method is used to weight the transient stability margin index of the bus voltage response to different fault disturbances, and the comprehensive short-circuit ratio under the fault set is calculated based on the weights of different faults and the weights of different buses.

3. The method for evaluating the ability of a synchronous generator to improve the transient voltage stability of a receiving-end power grid as claimed in claim 2, characterized in that: The calculation of the transient stability margin index adopts a multi-binary table method, which specifically includes: Establish bus voltage drop below a certain voltage value V crk Duration T crk The multi-binary table (V crk , T crk ); Determine the weight coefficient K of the kth voltage drop based on the multi-binary table k ; The transient voltage stability margin of the bus based on the multi-binary table is calculated according to the weight coefficient. The calculation formula is: Where η represents the transient voltage stability margin of the bus based on the multi-binary table, V min Indicates the minimum value of bus voltage during fault, V N Indicates the rated voltage of the busbar, k indicates the number of voltage drop, K k represents the weight coefficient of the kth voltage drop, T cr,k Indicates that the bus voltage drops below the voltage value V crk Duration, V cr,k represents the voltage threshold of the kth voltage drop, V cr,k-1 represents the voltage threshold of the k-1th voltage drop, K1 represents the weight coefficient of the first voltage drop, V cr,1 Indicates the voltage threshold of the first voltage drop, V R Indicates the recovery level of the bus voltage after the fault ends.

4. The method for evaluating the ability of a synchronous generator to improve the transient voltage stability of a receiving-end power grid as claimed in claim 3, characterized in that: The weights of different faults and the weights of different buses are calculated as follows: Among them, W fy represents the weight of different faults, x represents the bus number, y represents the fault number, η xy represents the transient voltage stability margin of bus x to the yth fault, W Bx Represents the weights of different buses, and max represents the maximum value.

5. The method for evaluating the ability of a synchronous generator to improve the transient voltage stability of a receiving-end power grid as claimed in claim 4, characterized in that: The calculation formula of the comprehensive short-circuit ratio under the fault set is: K WMITSCR =∑ y ∑ x W fy W Bx K MITSCR ; K WMITSCR-N =∑ y ∑ x W fy W Bx K MITSCR-N ; Among them, K WMITSCR Indicates the comprehensive short-circuit ratio of the DC commutation bus, K MITSCR K represents the transient short-circuit ratio of the multi-infeed DC commutation busbar. WMITSCR-N Indicates the comprehensive short-circuit ratio of the new energy grid-connected busbar, K MITSCR-N It represents the transient short-circuit ratio of multiple infeeds in the renewable energy grid-connected node.

6. The method for evaluating the ability of a synchronous generator to improve the transient voltage stability of a receiving-end power grid as claimed in claim 1, characterized in that: The index system includes a first sensitivity, a second sensitivity and a third sensitivity. The first sensitivity is the sensitivity of the comprehensive short-circuit ratio of the DC commutation bus to the change of the generator power factor. The second sensitivity is the sensitivity of the comprehensive short-circuit ratio of the new energy grid-connected bus to the change of the generator power factor. The third sensitivity is the sensitivity of the receiving end AC system network loss to the change of the generator power factor. The calculation formula of the first sensitivity is: The calculation formula of the second sensitivity is: The calculation formula of the third sensitivity is: Where K WMITSCR is the comprehensive short-circuit ratio of the DC commutation bus, cosθ k is the power factor of the kth synchronous generator, K WMITSCR-N is the comprehensive short-circuit ratio of the new energy grid-connected busbar, P loss It is the network loss of the receiving end AC system.

7. The method for evaluating the ability of a synchronous generator to improve the transient voltage stability of a receiving-end power grid as claimed in claim 6, characterized in that: Step S5 specifically includes: S51, forming a data matrix according to the first sensitivity, the second sensitivity and the third sensitivity; S52, establishing a judgment matrix of the first sensitivity, the second sensitivity and the third sensitivity, and based on the data matrix, respectively calculating the comprehensive weights of the first sensitivity, the second sensitivity and the third sensitivity in the judgment matrix; the comprehensive weights include subjective weights, objective weights and subjective and objective combined weights; S53. Based on subjective weights, objective weights and subjective and objective combined weights, the synchronous generators are evaluated and ranked using TOPSIS improved by prospect theory, and the ability of different synchronous generators in the receiving-end AC system to improve the transient voltage stability of the receiving-end power grid is obtained.

8. An evaluation system for improving the transient voltage stability capability of a synchronous generator at a receiving-end power grid, characterized in that: The evaluation method according to any one of claims 1 to 7 is adopted, comprising: A multi-port Thevenin equivalent module is configured to perform multi-port Thevenin equivalent on the receiving-end AC system from the DC conversion bus side and the new energy grid-connected bus side respectively; A short-circuit ratio calculation module is configured to calculate the multi-infeed transient short-circuit ratio of the DC commutation bus and the multi-infeed transient short-circuit ratio of the new energy grid-connected bus based on the receiving-end AC system after multi-port Thevenin equivalent; A comprehensive short-circuit ratio calculation module is configured to determine the weights of different faults, the weight of the DC commutation bus and the weight of the renewable energy grid-connected bus based on the response of the receiving-end AC system to the fault set, and calculate the comprehensive short-circuit ratio of the DC commutation bus and the comprehensive short-circuit ratio of the renewable energy grid-connected bus; An indicator system construction module is configured to construct an indicator system based on the comprehensive short-circuit ratio of the DC commutation bus, the comprehensive short-circuit ratio of the new energy grid-connected bus, and the network loss of the receiving-end AC system; The comprehensive evaluation module is configured as TOPSIS based on the index system and combined with subjective and objective combined weights and prospect theory to comprehensively evaluate the transient voltage level of the AC system at the receiving end of the synchronous generator support.

9. An electronic device, characterized in that: include: at least one processor, at least one memory, a communication interface, and a bus, wherein: The processor, memory, and communication interface communicate with each other via the bus; The memory stores program instructions that can be executed by the processor, and the processor calls the program instructions to implement the evaluation method according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions enable the computer to implement the evaluation method according to any one of claims 1 to 7.

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