Method and device for determining equivalent power grid of large power grid, and computer readable storage medium

Abstract

The invention discloses a method and a device for determining an equivalent power grid of a large power grid, and a computer readable storage medium. The method comprises the following steps: determining a sub-hyper-synchronous frequency range in which sub-hyper-synchronous oscillation occurs in a power grid; performing impedance scanning on the power grid according to a preset frequency interval to obtain actual impedance of the power grid under a plurality of frequency scanning points; performing polynomial fitting on the actual impedance to obtain an impedance transfer function in a Laplacian domain; solving the impedance transfer function to obtain a plurality of fitting coefficients; determining equivalent parameters of the equivalent power grid according to the plurality of fitting coefficients; the equivalent voltage amplitude of the equivalent power grid is determined according to the equivalent parameters; and constructing an equivalent power grid equivalent to the power grid according to the equivalent parameters and the equivalent voltage amplitude. According to the invention, the technical problems in related technologies are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of equivalent power grids, and in particular to a method and device for determining an equivalent power grid of a large power grid, and a computer-readable storage medium. Background Art

[0002] At present, sub-supersynchronous oscillations caused by the access of new energy to the power grid have gradually become a stability issue of widespread concern in the power grid. In engineering practice, electromagnetic transient simulation is a common method for sub-supersynchronous oscillation analysis of power grids. Due to the short step size of electromagnetic transient simulation, the scale of the power grid in the simulation analysis should not be too large. However, the actual power grid often contains tens of thousands of nodes, and the scale of the power grid is huge. Therefore, in the electromagnetic transient simulation analysis of sub-supersynchronous oscillations of the power grid, it is necessary to perform equivalent treatment on the large power grid at the access point of new energy. At present, the general method of equivalent large power grids is to simply equate the large power grid to the form of voltage source series impedance, but there is a big difference in the frequency response characteristics of the equivalent power grid and the actual large power grid in the sub-supersynchronous frequency band, which in turn affects the accuracy of the simulation analysis of sub-supersynchronous oscillations.

[0003] Currently, no effective solution has been proposed for the above-mentioned problems in the related technologies. Summary of the invention

[0004] The embodiments of the present invention provide a method and device for determining an equivalent power grid of a large power grid, and a computer-readable storage medium, so as to at least solve the technical problems in the related art.

[0005] According to one aspect of an embodiment of the present invention, a method for determining an equivalent power grid of a large power grid is provided, comprising: determining a sub-supersynchronous frequency range in which sub-supersynchronous oscillations occur in the power grid, wherein the sub-supersynchronous oscillations include at least: sub-synchronous oscillations and super-synchronous oscillations, wherein the sub-synchronous oscillations refer to oscillation phenomena that occur when the actual frequency of the power grid is lower than the synchronous frequency, and the super-synchronous oscillations refer to oscillation phenomena that occur when the actual frequency of the power grid is higher than the synchronous frequency; performing an impedance scan on the power grid within the sub-supersynchronous frequency range at a predetermined frequency interval to obtain the actual impedance of the power grid at multiple frequency scanning points, wherein the frequency scanning points refer to the frequency points at which the impedance scanning of the power grid is performed; performing polynomial fitting on the actual impedance to obtain an impedance transfer function of the actual impedance in the Laplace domain, wherein the impedance transfer function is the impedance transfer function of the actual impedance in the Laplace domain. The invention relates to a function for describing the impedance characteristics of the power grid in the sub-supersynchronous frequency range; solving the impedance transfer function using the actual impedance to obtain a plurality of fitting coefficients of the impedance transfer function, wherein the fitting coefficient is a coefficient of each term in the impedance transfer function; determining equivalent parameters of an equivalent power grid according to the plurality of fitting coefficients, wherein the equivalent power grid is a power grid obtained by performing equivalent processing on the power grid, and the equivalent parameters are used to make the frequency response characteristics of the equivalent power grid within the sub-supersynchronous frequency range the same as the actual frequency response characteristics of the power grid within the sub-supersynchronous frequency range; determining an equivalent voltage amplitude of the equivalent power grid according to the equivalent parameters, wherein the equivalent voltage amplitude is used to make the voltage of the equivalent power grid the same as the actual voltage of the power grid; and constructing the equivalent power grid equivalent to the power grid according to the equivalent parameters and the equivalent voltage amplitude.

[0006] Optionally, performing impedance scanning on the power grid within the sub-supersynchronous frequency range according to a predetermined frequency interval to obtain actual impedance of the power grid at multiple frequency scanning points includes: determining the predetermined frequency interval according to a first formula, wherein the first formula is: Δf represents the predetermined frequency interval, f a represents the starting frequency of the sub-supersynchronous frequency range, f b represents the end frequency of the sub-supersynchronous frequency range, N represents the total number of the frequency scanning points; and the scanning frequency value at each frequency scanning point is determined by using a second formula according to the predetermined frequency interval, wherein the second formula is: i =f a +(i-1)Δf, i represents the number of the frequency scanning point, f i represents the scanning frequency value at the i-th frequency scanning point; and determines the actual impedance at each frequency scanning point using a third formula according to the scanning frequency value, wherein the third formula is: Z(f i)=R(f i )+j*X(f i ), Z(f i ) represents the actual impedance at the i-th frequency scanning point, R(f i ) is the real part of the actual impedance of the ith element, representing the resistance, X(f i ) is the imaginary part of the i-th actual impedance, represents reactance, and j represents an imaginary number.

[0007] Optionally, performing polynomial fitting on the actual impedance to obtain an impedance transfer function of the actual impedance in the Laplace domain includes: in the process of performing polynomial fitting on the actual impedance, establishing a correlation relationship between the actual impedance and the impedance transfer function according to a fourth formula, wherein the fourth formula is: s = 2πf i *j, s represents the Laplace operator; the impedance transfer function is determined according to the fifth formula, wherein the fifth formula is: Z(s) represents the impedance transfer function, β0 is the first fitting coefficient of the term, β1 is the second fitting coefficient of the term, β2 is the third fitting coefficient of the term, and α1 is the fourth fitting coefficient of the term.

[0008] Optionally, solving the impedance transfer function using the actual impedance to obtain a plurality of fitting coefficients of the impedance transfer function includes: solving the impedance transfer function using the actual impedance according to a sixth formula to obtain a plurality of fitting coefficients of the impedance transfer function, wherein the sixth formula is:

[0009] Optionally, the equivalent parameters include: parallel equivalent resistance, series equivalent resistance, equivalent reactance and equivalent capacitance, and determining the equivalent parameters of the equivalent power grid according to the multiple fitting coefficients includes: determining the parallel equivalent resistance using a seventh formula according to the second fitting coefficient, the third fitting coefficient and the fourth fitting coefficient, wherein the seventh formula is: R1 represents the parallel equivalent resistance; the series equivalent resistance is determined by using the eighth formula according to the first fitting coefficient and the parallel equivalent resistance, wherein the eighth formula is: R2 represents the series equivalent resistance, the first fitting coefficient, the second fitting coefficient, the third fitting coefficient and the fourth fitting coefficient are all one of the multiple fitting coefficients; the equivalent reactance is determined by using a ninth formula according to the fourth fitting coefficient and the series equivalent resistance, wherein the ninth formula is: L=α1R2, L represents the equivalent reactance; the equivalent voltage amplitude is determined by using a tenth formula according to the third fitting coefficient and the fourth fitting coefficient, wherein the tenth formula is: C represents the equivalent voltage amplitude.

[0010] Optionally, determining the equivalent voltage amplitude of the equivalent power grid according to the equivalent parameter includes: determining the equivalent voltage amplitude of the equivalent power grid according to the equivalent parameter using an eleventh formula, wherein the eleventh formula is: V eq represents the equivalent voltage amplitude, P represents the active power of the access point, Q represents the reactive power of the access point, V represents the voltage amplitude of the access point, f0 represents the synchronization frequency, and the access point is the node where the new energy station accesses the power grid.

[0011] Optionally, after constructing the equivalent power grid equivalent to the power grid according to the equivalent parameters and the equivalent voltage amplitude, the method for determining the equivalent power grid of the large power grid further includes: simulating the sub-supersynchronous oscillation using the equivalent power grid to obtain a simulation result.

[0012] According to another aspect of an embodiment of the present invention, there is further provided an equivalent power grid determination device for a large power grid, comprising: a first determination unit, configured to determine a sub-supersynchronous frequency range in which a sub-supersynchronous oscillation occurs in the power grid, wherein the sub-supersynchronous oscillation includes at least: a sub-synchronous oscillation and a supersynchronous oscillation, wherein the sub-synchronous oscillation refers to an oscillation phenomenon that occurs when the actual frequency of the power grid is lower than the synchronous frequency, and the supersynchronous oscillation refers to an oscillation phenomenon that occurs when the actual frequency of the power grid is higher than the synchronous frequency; a first acquisition unit, configured to perform an impedance scan on the power grid within the sub-supersynchronous frequency range at a predetermined frequency interval to obtain the actual impedance of the power grid at a plurality of frequency scanning points, wherein the frequency scanning point refers to a frequency point at which the impedance scanning of the power grid is performed; and a second acquisition unit, configured to perform a polynomial fitting on the actual impedance to obtain an impedance transfer function of the actual impedance in the Laplace domain, wherein the impedance transfer function is a function of the impedance of the actual impedance in the Laplace domain. a function for describing the impedance characteristics of the power grid; a third acquisition unit, used to solve the impedance transfer function using the actual impedance to obtain a plurality of fitting coefficients of the impedance transfer function, wherein the fitting coefficient is the coefficient of each term in the impedance transfer function; a second determination unit, used to determine equivalent parameters of an equivalent power grid according to the plurality of fitting coefficients, wherein the equivalent power grid is a power grid obtained by performing equivalent processing on the power grid, and the equivalent parameters are used to make the frequency response characteristics of the equivalent power grid within the sub-supersynchronous frequency range the same as the actual frequency response characteristics of the power grid within the sub-supersynchronous frequency range; a third determination unit, used to determine an equivalent voltage amplitude of the equivalent power grid according to the equivalent parameters, wherein the equivalent voltage amplitude is used to make the voltage of the equivalent power grid the same as the actual voltage of the power grid; a construction unit, used to construct the equivalent power grid equivalent to the power grid according to the equivalent parameters and the equivalent voltage amplitude.

[0013] Optionally, the first acquisition unit includes: a first determination module, configured to determine the predetermined frequency interval according to a first formula, wherein the first formula is: Δf represents the predetermined frequency interval, f a represents the starting frequency of the sub-supersynchronous frequency range, f b represents the end frequency of the sub-supersynchronous frequency range, and N represents the total number of the frequency scanning points; a second determination module is used to determine the scanning frequency value at each of the frequency scanning points according to the predetermined frequency interval using a second formula, wherein the second formula is: i =f a +(i-1)Δf, i represents the number of the frequency scanning point, f irepresents the scanning frequency value at the i-th frequency scanning point; a third determination module, used to determine the actual impedance at each frequency scanning point using a third formula according to the scanning frequency value, wherein the third formula is: Z(f i )=R(f i )+j*X(f i ), Z(f i ) represents the actual impedance at the i-th frequency scanning point, R(f i ) is the real part of the actual impedance of the ith element, representing the resistance, X(f i ) is the imaginary part of the i-th actual impedance, represents reactance, and j represents an imaginary number.

[0014] Optionally, the second acquisition unit includes: an establishment module, which is used to establish a correlation relationship between the actual impedance and the impedance transfer function according to a fourth formula during the polynomial fitting of the actual impedance, wherein the fourth formula is: s = 2πf i *j, s represents the Laplace operator; a fourth determination module, used to determine the impedance transfer function according to a fifth formula, wherein the fifth formula is: Z(s) represents the impedance transfer function, β0 is the first fitting coefficient of the term, β1 is the second fitting coefficient of the term, β2 is the third fitting coefficient of the term, and α1 is the fourth fitting coefficient of the term.

[0015] Optionally, the third acquisition unit includes: an acquisition module, configured to solve the impedance transfer function using the actual impedance according to a sixth formula to obtain a plurality of fitting coefficients of the impedance transfer function, wherein the sixth formula is:

[0016] Optionally, the equivalent parameters include: parallel equivalent resistance, series equivalent resistance, equivalent reactance and equivalent capacitance, and the second determination unit includes: a fifth determination module, used to determine the parallel equivalent resistance according to the second fitting coefficient, the third fitting coefficient and the fourth fitting coefficient using a seventh formula, wherein the seventh formula is: R1 represents the parallel equivalent resistance; a sixth determination module, used to determine the series equivalent resistance using an eighth formula according to the first fitting coefficient and the parallel equivalent resistance, wherein the eighth formula is: R2 represents the series equivalent resistance, and the first fitting coefficient, the second fitting coefficient, the third fitting coefficient and the fourth fitting coefficient are all one of the multiple fitting coefficients; the seventh determination module is used to determine the equivalent reactance using a ninth formula according to the fourth fitting coefficient and the series equivalent resistance, wherein the ninth formula is: L=α1R2, L represents the equivalent reactance; the eighth determination module is used to determine the equivalent voltage amplitude according to the third fitting coefficient and the fourth fitting coefficient using a tenth formula, wherein the tenth formula is: C represents the equivalent voltage amplitude.

[0017] Optionally, the third determination unit includes: a ninth determination module, configured to determine the equivalent voltage amplitude of the equivalent power grid according to the equivalent parameter using an eleventh formula, wherein the eleventh formula is: V eq represents the equivalent voltage amplitude, P represents the active power of the access point, Q represents the reactive power of the access point, V represents the voltage amplitude of the access point, f0 represents the synchronization frequency, and the access point is the node where the new energy station accesses the power grid.

[0018] Optionally, the equivalent power grid determination device of the large power grid also includes: a fourth acquisition unit, which is used to simulate the sub-supersynchronous oscillation using the equivalent power grid to obtain a simulation result after constructing the equivalent power grid equivalent to the power grid according to the equivalent parameters and the equivalent voltage amplitude.

[0019] According to another aspect of an embodiment of the present invention, a system for determining an equivalent power grid of a large power grid is provided. The system for determining an equivalent power grid of a large power grid uses any one of the above-mentioned methods for determining an equivalent power grid of a large power grid.

[0020] According to another aspect of an embodiment of the present invention, a computer-readable storage medium is further provided, the computer-readable storage medium comprising a stored program, wherein the program executes any one of the above-mentioned methods for determining an equivalent power grid of a large power grid.

[0021] According to another aspect of an embodiment of the present invention, a processor is further provided, the processor being used to run a program, wherein when the program is run, any one of the above-mentioned methods for determining an equivalent power grid of a large power grid is executed.

[0022] According to another aspect of an embodiment of the present invention, a computer program product is further provided, comprising computer instructions, wherein when the computer instructions are executed by a processor, any one of the above-mentioned methods for determining an equivalent power grid of a large power grid is executed.

[0023] In an embodiment of the present invention, a sub-supersynchronous frequency range in which a sub-supersynchronous oscillation occurs in a power grid is determined, wherein the sub-supersynchronous oscillation includes at least: sub-synchronous oscillation and super-synchronous oscillation, sub-synchronous oscillation refers to an oscillation phenomenon that occurs when the actual frequency of the power grid is lower than the synchronous frequency, and super-synchronous oscillation refers to an oscillation phenomenon that occurs when the actual frequency of the power grid is higher than the synchronous frequency; an impedance scan is performed on the power grid within the sub-supersynchronous frequency range at a predetermined frequency interval to obtain an actual impedance of the power grid at multiple frequency scanning points, wherein the frequency scanning point refers to a frequency point at which the impedance scan is performed on the power grid; a polynomial fitting is performed on the actual impedance to obtain an impedance transfer function of the actual impedance in the Laplace domain, wherein the impedance transfer function is an impedance transfer function of the power grid in the Laplace domain. The invention relates to a method for determining an equivalent power grid according to a plurality of fitting coefficients, wherein the equivalent power grid is a power grid obtained by equivalently processing the power grid, and the equivalent parameters are used to make the frequency response characteristics of the equivalent power grid within a sub-supersynchronous frequency range the same as the actual frequency response characteristics of the power grid within the sub-supersynchronous frequency range; determining the equivalent voltage amplitude of the equivalent power grid according to the equivalent parameters, wherein the equivalent voltage amplitude is used to make the voltage of the equivalent power grid the same as the actual voltage of the power grid; and constructing an equivalent power grid equivalent to the power grid according to the equivalent parameters and the equivalent voltage amplitude. Through the above technical scheme, the purpose of performing impedance scanning on the power grid within the sub-supersynchronous frequency range where sub-supersynchronous oscillation occurs, and solving the impedance transfer function in the Laplace domain using the actual impedance obtained by the scan, so as to construct an equivalent power grid with the power grid according to the equivalent parameters and equivalent voltage amplitudes obtained by the solution, and achieve the technical effect of making the constructed equivalent power grid and the actual power grid have the same frequency response characteristics within the sub-supersynchronous frequency range, thereby improving the accuracy of simulation results when simulating and analyzing the power grid, and thus solving the technical problems in related technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0025] Figure 1 It is a hardware structure block diagram of a mobile terminal of a method for determining an equivalent power grid of a large power grid according to an embodiment of the present invention;

[0026] Figure 2 is a flow chart of a method for determining an equivalent power grid of a large power grid according to an embodiment of the present invention;

[0027] Figure 3 is a schematic diagram of a new energy station connected to a large power grid according to an embodiment of the present invention;

[0028] Figure 4 is a flow chart of an optional large power grid equivalent power grid determination method according to an embodiment of the present invention;

[0029] Figure 5 is a schematic diagram of an equivalent power grid of a large power grid according to an embodiment of the present invention;

[0030] Figure 6 4 is a schematic diagram of an equivalent power grid determination device for a large power grid according to an embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings 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 should fall within the scope of protection of the present invention.

[0032] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0033] As introduced in the background technology, in the related art, in view of the above defects, an equivalent power grid determination method and device of a large power grid and a computer-readable storage medium are provided in an embodiment of the present invention.

[0034] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0035] The method embodiments provided in the embodiments of the present invention can be executed in a mobile terminal, a computer terminal or a similar computing device. Taking running on a mobile terminal as an example, Figure 1 1 is a hardware structure block diagram of a mobile terminal of a method for determining an equivalent power grid of a large power grid according to an embodiment of the present invention. Figure 1 As shown, the mobile terminal may include one or more ( Figure 1Only one is shown in the figure) a processor 102 (the processor 102 may include but is not limited to a processing device such as a microprocessor MCU or a programmable logic device FPGA) and a memory 104 for storing data, wherein the mobile terminal may also include a transmission device 106 and an input / output device 108 for communication functions. It can be understood by those skilled in the art that Figure 1 The structure shown is for illustration only and does not limit the structure of the mobile terminal. Figure 1 More or fewer components as shown, or with Figure 1 Different configurations are shown.

[0036] The memory 104 can be used to store computer programs, for example, software programs and modules of application software, such as the computer program corresponding to the method for determining the equivalent power grid of the large power grid in the embodiment of the present invention. The processor 102 executes various functional applications and data processing by running the computer program stored in the memory 104, that is, to implement the above method. The memory 104 may include a high-speed random access memory, and may also include a non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some examples, the memory 104 may further include a memory remotely arranged relative to the processor 102, and these remote memories may be connected to the mobile terminal via a network. Examples of the above network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and a combination thereof. The transmission device 106 is used to receive or send data via a network. The specific example of the above network may include a wireless network provided by a communication provider of the mobile terminal. In one example, the transmission device 106 includes a network adapter (Network Interface Controller, referred to as NIC), which can be connected to other network devices through a base station so as to communicate with the Internet. In one example, the transmission device 106 may be a radio frequency (RF) module, which is used to communicate with the Internet wirelessly.

[0037] According to an embodiment of the present invention, a method embodiment of a method for determining an equivalent power grid of a large power grid is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0038] Figure 2 is a flow chart of a method for determining an equivalent power grid of a large power grid according to an embodiment of the present invention. Figure 2 As shown, the method comprises the following steps:

[0039] Step S202, determining a sub-supersynchronous frequency range in which a sub-supersynchronous oscillation occurs in the power grid, wherein the sub-supersynchronous oscillation includes at least: sub-synchronous oscillation and super-synchronous oscillation. Sub-synchronous oscillation refers to an oscillation phenomenon that occurs when the actual frequency of the power grid is lower than the synchronous frequency, and super-synchronous oscillation refers to an oscillation phenomenon that occurs when the actual frequency of the power grid is higher than the synchronous frequency.

[0040] Combine the following Figure 3 and Figure 4 The above embodiments of the present invention are described in detail. Figure 3 is a schematic diagram of a new energy station connected to a large power grid according to an embodiment of the present invention, Figure 4 is a flow chart of an optional method for determining an equivalent power grid of a large power grid according to an embodiment of the present invention; Figure 3 As shown in the figure, after the new energy station is connected to the large power grid, the active power, reactive power and voltage amplitude of its access point can be represented by P, Q and V respectively; in fact, the power grid usually includes tens of thousands of electrical nodes. The huge scale of the power grid makes it impossible to directly perform electromagnetic transient modeling and simulation on the large power grid in the simulation analysis of the sub-supersynchronous oscillation of the power grid, but it is necessary to simplify the large power grid. In order to ensure the accuracy of the sub-supersynchronous oscillation analysis based on the equivalent power grid, the equivalent power grid needs to retain the frequency response characteristics (referred to as "frequency response characteristics") of the large power grid in the sub-supersynchronous frequency band (i.e., the sub-supersynchronous frequency range, the same below).

[0041] like Figure 4 As shown in the figure, the data of the large power grid can be obtained to clarify the starting frequency and ending frequency of the target frequency band. In the actual sub-supersynchronous oscillation analysis, the frequency band of the large power grid frequency response characteristics that need to be focused on is different depending on the analysis problem. For example, in the power system analysis, the sub-supersynchronous frequency band can be the frequency range of [0, 100] Hz. Assume that the frequency band that needs to be focused on in [0, 100] Hz is [f a , f b ]Hz, where f a , f b are the starting frequency and ending frequency of the frequency band of interest, and there is 0 <f a <f b <100, below [f a , f b ]Hz is taken as an example of the sub-supersynchronous frequency band for detailed description.

[0042] Step S204, performing impedance scanning on the power grid within the sub-supersynchronous frequency range according to a predetermined frequency interval to obtain actual impedance of the power grid at multiple frequency scanning points, wherein the frequency scanning point refers to the frequency point at which the impedance scanning of the power grid is performed.

[0043] In this embodiment, multiple frequency scanning points can be set at a certain frequency interval in the sub-supersynchronous frequency band, and then the power grid can be impedance scanned to obtain the impedance scanning value (i.e., actual impedance) on the power grid side of the new energy station access point at each frequency scanning point.

[0044] According to the above embodiment of the present invention, in the above step S204, the impedance scanning of the power grid is performed within the sub-supersynchronous frequency range according to the predetermined frequency interval to obtain the actual impedance of the power grid at multiple frequency scanning points, including: determining the predetermined frequency interval according to a first formula, wherein the first formula is: Δf represents the predetermined frequency interval, f a represents the starting frequency of the sub-supersynchronous frequency range, f b represents the end frequency of the sub-supersynchronous frequency range, N represents the total number of frequency scanning points; the scanning frequency value at each frequency scanning point is determined by using the second formula according to the predetermined frequency interval, wherein the second formula is: f i =f a +(i-1)Δf, i represents the number of the frequency scanning point, f i represents the scanning frequency value at the i-th frequency scanning point; the actual impedance at each frequency scanning point is determined by using the third formula according to the scanning frequency value, wherein the third formula is: Z(f i )=R(f i )+j*X(f i ), Z(f i ) represents the actual impedance at the i-th frequency scanning point, R(f i ) is the real part of the ith actual impedance, representing the resistance, X(f i ) is the imaginary part of the ith actual impedance, represents reactance, and j represents an imaginary number.

[0045] As above Figure 4 As shown, assuming that the number of frequency scanning points set is N, and the scanning frequency values ​​at the N frequency scanning points follow an arithmetic distribution, the predetermined frequency interval between the scanning frequency values ​​at any two frequency scanning points can be expressed by the formula: Calculated, where Δf represents the predetermined frequency interval, the scanning frequency value f at the i-th (i=1, 2, ..., N) frequency scanning point is i f i =f a +(i-1)Δf; then the formula can be used: Z(f i )=R(f i )+j*X(f i ) calculates the impedance scanning value at each frequency scanning point. The grid side impedance scanning value corresponding to the i-th frequency scanning point is Z(f i ), the real part of the impedance value is R(f i ), the imaginary part is X(fi ).

[0046] Step S206 , performing polynomial fitting on the actual impedance to obtain an impedance transfer function of the actual impedance in the Laplace domain, wherein the impedance transfer function is a function that describes the impedance characteristics of the power grid in the Laplace domain.

[0047] In this embodiment, a polynomial fitting may be performed on the acquired impedance scanning values ​​to obtain an impedance transfer function in the Laplace domain, where the impedance transfer function is a function that describes the impedance characteristics of the power grid in the Laplace domain.

[0048] According to the above embodiment of the present invention, in the above step S206, polynomial fitting is performed on the actual impedance to obtain the impedance transfer function of the actual impedance in the Laplace domain, including: in the process of polynomial fitting of the actual impedance, a correlation relationship between the actual impedance and the impedance transfer function is established according to the fourth formula, wherein the fourth formula is: s = 2πf i *j, s represents the Laplace operator; the impedance transfer function is determined according to the fifth formula, where the fifth formula is: Z(s) represents the impedance transfer function, β0 is the first fitting coefficient of the term, β1 is the second fitting coefficient of the term, β2 is the third fitting coefficient of the term, and α1 is the fourth fitting coefficient of the term.

[0049] As above Figure 4 As shown, assuming that the impedance transfer function of the grid side of the new energy access point is represented by Z(s), let Among them, N(s) and D(s) are the numerator function and denominator function of Z(s) respectively; the polynomial fitting method is used to fit N(s) and D(s) respectively, and the fitting expressions of N(s) and D(s) are as follows: N(s) = β0 + β1s + β2s 2 , D(s)=1+α1s, where s is the Laplace operator, β0, β1, β2 are the fitting coefficients of each term in the N(s) expression, α1 is the fitting coefficient of each term in the D(s) expression, Z(s) and Z(f i ) can be obtained from the relationship between the Laplace operator and the scanning frequency value at each frequency scanning point: s = 2πf i *j contact.

[0050] Step S208, using the actual impedance to solve the impedance transfer function, to obtain a plurality of fitting coefficients of the impedance transfer function, wherein the fitting coefficient is the coefficient of each term in the impedance transfer function.

[0051] In this embodiment, Z(f i ) to solve the fitting coefficients in Z(s), we can use s = 2πfi *j converts Z(s) to complex form, and then makes Z(s) and Z(f i ) in the corresponding expression, the real part and the imaginary part establish an equality relationship, that is, the real part in Z(s) and Z(f i ) are equal to the real parts in Z(s), and the imaginary parts in Z(f i ) is equal to the corresponding imaginary part in Z(s), so as to solve each fitting coefficient in Z(s); in this embodiment, for the complex number representation of Z(s), 2πf i *j replaces s You can get it, no more details here.

[0052] According to the above embodiment of the present invention, in the above step S208, the impedance transfer function is solved by using the actual impedance to obtain multiple fitting coefficients of the impedance transfer function, including: solving the impedance transfer function by using the actual impedance according to the sixth formula to obtain multiple fitting coefficients of the impedance transfer function, wherein the sixth formula is:

[0053]

[0054] As above Figure 4 As shown, based on the impedance scan values ​​at each frequency scan point and the real part of Z(s) and Z(f i ) are equal to the real parts in Z(s), and the imaginary parts in Z(f i ) can be calculated by using the equation relationship established by the corresponding equal parts:

[0055] Step S210, determining equivalent parameters of an equivalent power grid according to a plurality of fitting coefficients, wherein the equivalent power grid is a power grid obtained by performing equivalent processing on the power grid, and the equivalent parameters are used to make the frequency response characteristics of the equivalent power grid within the sub-supersynchronous frequency range the same as the actual frequency response characteristics of the power grid within the sub-supersynchronous frequency range.

[0056] Optionally, the above-mentioned equivalent parameters may include but are not limited to: parallel equivalent resistance, series equivalent resistance, equivalent reactance and equivalent capacitance, etc.

[0057] In this embodiment, the equivalent parameters of the equivalent power grid can be calculated according to the fitting coefficients obtained by the above solution. The equivalent parameters obtained according to the above method provided by the embodiment of the present invention can ensure that the frequency response characteristics of the equivalent power grid within the sub-supersynchronous frequency range are the same as the actual frequency response characteristics of the power grid within the sub-supersynchronous frequency range, so as to ensure the accuracy of the simulation results when simulating the power grid.

[0058] According to the above embodiment of the present invention, in the above step S210, determining the equivalent parameters of the equivalent power grid according to multiple fitting coefficients includes: determining the parallel equivalent resistance using the seventh formula according to the second fitting coefficient, the third fitting coefficient and the fourth fitting coefficient, wherein the seventh formula is: R1 represents a parallel equivalent resistance; the series equivalent resistance is determined using the eighth formula according to the first fitting coefficient and the parallel equivalent resistance, where the eighth formula is: R2 represents the equivalent resistance in series, and the first fitting coefficient, the second fitting coefficient, the third fitting coefficient and the fourth fitting coefficient are all fitting coefficients among the multiple fitting coefficients; the equivalent reactance is determined by the ninth formula according to the fourth fitting coefficient and the equivalent resistance in series, wherein the ninth formula is: L=α1R2, and L represents the equivalent reactance; the equivalent voltage amplitude is determined by the tenth formula according to the third fitting coefficient and the fourth fitting coefficient, wherein the tenth formula is: C represents the equivalent capacitance.

[0059] As above Figure 4 As shown, the equivalent parameters R1, R2, L and C of the equivalent power grid can be calculated based on the fitting data of α1, β0, β1 and β2 by the following formula: L=α1R2, where R1 represents a parallel equivalent resistance, R2 represents a series equivalent resistance, L represents an equivalent reactance, and C represents an equivalent capacitance.

[0060] Step S212, determining an equivalent voltage amplitude of the equivalent power grid according to the equivalent parameters, wherein the equivalent voltage amplitude is used to make the voltage of the equivalent power grid the same as the actual voltage of the power grid.

[0061] In this embodiment, the equivalent voltage amplitude of the equivalent power grid can be calculated based on the calculated equivalent parameters and combined with the active power P, reactive power Q and voltage amplitude V of the access point when the new energy station is connected to the power grid.

[0062] According to the above embodiment of the present invention, in the above step S212, determining the equivalent voltage amplitude of the equivalent power grid according to the equivalent parameters includes: determining the equivalent voltage amplitude of the equivalent power grid according to the equivalent parameters using the eleventh formula, wherein the eleventh formula is: V eq represents the equivalent voltage amplitude, P represents the active power of the access point, Q represents the reactive power of the access point, V represents the voltage amplitude of the access point, f0 represents the synchronization frequency, and the access point is the node where the new energy station is connected to the power grid.

[0063] As above Figure 4 As shown, based on the equivalent parameters R1, R2, L, C and the P, Q, V of the access point, the equivalent power amplitude V of the equivalent power grid can be calculated by the following formula eq :

[0064] Step S214, constructing an equivalent power grid equivalent to the power grid according to the equivalent parameters and the equivalent voltage amplitudes.

[0065] Combine the following Figure 5 The above embodiments of the present invention are described in detail. Figure 5 is a schematic diagram of an equivalent power grid of a large power grid according to an embodiment of the present invention.

[0066] As above Figure 4 As shown, according to the above steps, the equivalent parameters and equivalent voltage amplitudes of the equivalent power grid can be calculated to construct the following Figure 5 The equivalent power grid is shown.

[0067] In a specific embodiment of the present invention, after constructing an equivalent power grid equivalent to the power grid according to equivalent parameters and equivalent voltage amplitudes, the method for determining the equivalent power grid of the large power grid also includes: simulating sub-supersynchronous oscillations using the equivalent power grid to obtain simulation results.

[0068] Specifically, the equivalent power grid obtained according to the above embodiment of the present invention can achieve substantially the same actual frequency response characteristics as the large power grid, and the accuracy of the simulation results can be improved by simulating and analyzing sub-supersynchronous oscillations through the equivalent power grid.

[0069] As can be seen from the above, through the technical solution provided by the above embodiment of the present invention, the sub-supersynchronous frequency range in which sub-supersynchronous oscillation occurs in the power grid can be determined, wherein the sub-supersynchronous oscillation at least includes: sub-synchronous oscillation and supersynchronous oscillation, sub-synchronous oscillation refers to the oscillation phenomenon that occurs when the actual frequency of the power grid is lower than the synchronous frequency, and supersynchronous oscillation refers to the oscillation phenomenon that occurs when the actual frequency of the power grid is higher than the synchronous frequency; the power grid is impedance scanned within the sub-supersynchronous frequency range according to a predetermined frequency interval to obtain the actual impedance of the power grid at multiple frequency scanning points, wherein the frequency scanning point refers to the frequency point at which the impedance scanning of the power grid is performed; the actual impedance is polynomially fitted to obtain the impedance transfer function of the actual impedance in the Laplace domain, wherein the impedance transfer function is a function that describes the impedance characteristics of the power grid in the Laplace domain; the impedance transfer function is solved using the actual impedance to obtain multiple fitting coefficients of the impedance transfer function, wherein the fitting coefficient is the coefficient of each term in the impedance transfer function; according to multiple The fitting coefficient determines the equivalent parameters of the equivalent power grid, wherein the equivalent power grid is a power grid obtained by equivalent processing of the power grid, and the equivalent parameters are used to make the frequency response characteristics of the equivalent power grid in the sub-supersynchronous frequency range the same as the actual frequency response characteristics of the power grid in the sub-supersynchronous frequency range; the equivalent voltage amplitude of the equivalent power grid is determined according to the equivalent parameters, wherein the equivalent voltage amplitude is used to make the voltage of the equivalent power grid the same as the actual voltage of the power grid; an equivalent power grid equivalent to the power grid is constructed according to the equivalent parameters and the equivalent voltage amplitude, so as to achieve the purpose of performing impedance scanning on the power grid in the sub-supersynchronous frequency range where sub-supersynchronous oscillation occurs, and solving the impedance transfer function in the Laplace domain by using the actual impedance obtained by the scan, so as to construct an equivalent power grid with the power grid according to the equivalent parameters and the equivalent voltage amplitude obtained by the solution, so as to achieve the technical effect of making the constructed equivalent power grid have the same frequency response characteristics as the actual power grid in the sub-supersynchronous frequency range, and improve the accuracy of the simulation results when simulating and analyzing the power grid.

[0070] Therefore, the technical problems in the related art are solved through the technical solutions provided by the above embodiments of the present invention.

[0071] It should be noted that, for the aforementioned method embodiments, for the sake of simplicity, they are all expressed as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the described order of actions, because according to the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present application.

[0072] Through the description of the above implementation methods, those skilled in the art can clearly understand that the method according to the above embodiment can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk), and includes a number of instructions for a terminal device (which can be a mobile phone, computer, server, or network device, etc.) to execute the methods described in each embodiment of the present application.

[0073] According to an embodiment of the present invention, there is also provided a device for determining an equivalent power grid of a thermal large power grid for implementing the above-mentioned method for determining an equivalent power grid of a large power grid. Figure 6 is a schematic diagram of an equivalent power grid determination device for a large power grid according to an embodiment of the present invention, such as Figure 6 As shown, the device includes: a first determination unit 601, a first acquisition unit 603, a second acquisition unit 605, a third acquisition unit 607, a second determination unit 609, a third determination unit 611 and a construction unit 613. The equivalent power grid determination device of the large power grid is described in detail below.

[0074] The first determination unit 601 is used to determine a sub-supersynchronous frequency range in which a sub-supersynchronous oscillation occurs in a power grid, wherein the sub-supersynchronous oscillation includes at least: a sub-synchronous oscillation and a super-synchronous oscillation. The sub-synchronous oscillation refers to an oscillation phenomenon that occurs when the actual frequency of the power grid is lower than the synchronous frequency, and the super-synchronous oscillation refers to an oscillation phenomenon that occurs when the actual frequency of the power grid is higher than the synchronous frequency.

[0075] The first acquisition unit 603 is used to perform impedance scanning on the power grid within the sub-supersynchronous frequency range according to a predetermined frequency interval to obtain actual impedance of the power grid at multiple frequency scanning points, wherein the frequency scanning point refers to the frequency point at which the impedance scanning of the power grid is performed.

[0076] The second acquisition unit 605 is used to perform polynomial fitting on the actual impedance to obtain an impedance transfer function of the actual impedance in the Laplace domain, wherein the impedance transfer function is a function that describes the impedance characteristics of the power grid in the Laplace domain.

[0077] The third acquisition unit 607 is used to solve the impedance transfer function by using the actual impedance to obtain a plurality of fitting coefficients of the impedance transfer function, wherein the fitting coefficient is a coefficient of each term in the impedance transfer function.

[0078] The second determination unit 609 is used to determine equivalent parameters of the equivalent power grid according to multiple fitting coefficients, wherein the equivalent power grid is a power grid obtained by equivalent processing of the power grid, and the equivalent parameters are used to make the frequency response characteristics of the equivalent power grid within the sub-supersynchronous frequency range the same as the actual frequency response characteristics of the power grid within the sub-supersynchronous frequency range.

[0079] The third determining unit 611 is used to determine an equivalent voltage amplitude of the equivalent power grid according to the equivalent parameter, wherein the equivalent voltage amplitude is used to make the voltage of the equivalent power grid the same as the actual voltage of the power grid.

[0080] The construction unit 613 is used to construct an equivalent power grid equivalent to the power grid according to the equivalent parameters and the equivalent voltage amplitude.

[0081] It should be noted here that the above-mentioned first determination unit 601, first acquisition unit 603, second acquisition unit 605, third acquisition unit 607, second determination unit 609, third determination unit 611 and construction unit 613 correspond to steps S202 to S214 in the above-mentioned embodiments, and the seven units are the same as the instances and application scenarios implemented by the corresponding steps, but are not limited to the contents disclosed in the above-mentioned embodiments.

[0082] As can be seen from the above, in the scheme recorded in the above embodiment of the present invention, the first determination unit can be used to determine the sub-supersynchronous frequency range in which the sub-supersynchronous oscillation occurs in the power grid, wherein the sub-supersynchronous oscillation includes at least: sub-synchronous oscillation and supersynchronous oscillation, the sub-synchronous oscillation refers to the oscillation phenomenon that occurs when the actual frequency of the power grid is lower than the synchronous frequency, and the supersynchronous oscillation refers to the oscillation phenomenon that occurs when the actual frequency of the power grid is higher than the synchronous frequency; then the first acquisition unit is used to perform impedance scanning on the power grid within the sub-supersynchronous frequency range according to a predetermined frequency interval to obtain the actual impedance of the power grid at multiple frequency scanning points, wherein the frequency scanning point refers to the frequency point at which the impedance scanning of the power grid is performed; then the second acquisition unit is used to perform polynomial fitting on the actual impedance to obtain the impedance transfer function of the actual impedance in the Laplace domain, wherein the impedance transfer function is a function that describes the impedance characteristics of the power grid in the Laplace domain; then the third acquisition unit is used to solve the impedance transfer function using the actual impedance to obtain multiple fitting coefficients of the impedance transfer function, wherein the fitting coefficient is the coefficient of each term in the impedance transfer function; then The second determination unit is used to determine the equivalent parameters of the equivalent power grid according to multiple fitting coefficients, wherein the equivalent power grid is a power grid obtained by equivalent processing of the power grid, and the equivalent parameters are used to make the frequency response characteristics of the equivalent power grid in the sub-supersynchronous frequency range the same as the actual frequency response characteristics of the power grid in the sub-supersynchronous frequency range; then the third determination unit is used to determine the equivalent voltage amplitude of the equivalent power grid according to the equivalent parameters, wherein the equivalent voltage amplitude is used to make the voltage of the equivalent power grid the same as the actual voltage of the power grid; finally, the construction unit is used to construct an equivalent power grid equivalent to the power grid according to the equivalent parameters and the equivalent voltage amplitude, so as to achieve the purpose of performing impedance scanning on the power grid within the sub-supersynchronous frequency range where sub-supersynchronous oscillation occurs, and solving the impedance transfer function in the Laplace domain by using the actual impedance obtained by the scan, so as to construct an equivalent power grid with the power grid according to the equivalent parameters and the equivalent voltage amplitude obtained by the solution, so as to achieve the technical effect of making the constructed equivalent power grid have the same frequency response characteristics as the actual power grid in the sub-supersynchronous frequency range, and improve the accuracy of the simulation results when simulating and analyzing the power grid.

[0083] Therefore, the technical problems in the related art are solved through the technical solutions provided by the above embodiments of the present invention.

[0084] Optionally, the first acquisition unit includes: a first determination module, configured to determine the predetermined frequency interval according to a first formula, wherein the first formula is: Δf represents the predetermined frequency interval, f a represents the starting frequency of the sub-supersynchronous frequency range, f b represents the end frequency of the sub-supersynchronous frequency range, and N represents the total number of frequency scanning points; a second determination module is used to determine the scanning frequency value at each frequency scanning point according to a predetermined frequency interval using a second formula, wherein the second formula is: fi =f a +(i-1)Δf, i represents the number of the frequency scanning point, f i represents the scanning frequency value at the i-th frequency scanning point; a third determination module, used to determine the actual impedance at each frequency scanning point using a third formula according to the scanning frequency value, wherein the third formula is: Z(f i )=R(f i )+j*X(f i ), Z(f i ) represents the actual impedance at the i-th frequency scanning point, R(f i ) is the real part of the ith actual impedance, representing the resistance, X(f i ) is the imaginary part of the ith actual impedance, represents reactance, and j represents an imaginary number.

[0085] Optionally, the second acquisition unit includes: an establishment module, which is used to establish a correlation relationship between the actual impedance and the impedance transfer function according to a fourth formula in the process of performing polynomial fitting on the actual impedance, wherein the fourth formula is: s = 2πf i *j, s represents the Laplace operator; a fourth determination module is used to determine the impedance transfer function according to the fifth formula, wherein the fifth formula is: Z(s) represents the impedance transfer function, β0 is the first fitting coefficient of the term, β1 is the second fitting coefficient of the term, β2 is the third fitting coefficient of the term, and α1 is the fourth fitting coefficient of the term.

[0086] Optionally, the third acquisition unit includes: an acquisition module, which is used to solve the impedance transfer function using the actual impedance according to the sixth formula to obtain multiple fitting coefficients of the impedance transfer function, wherein the sixth formula is:

[0087]

[0088] Optionally, the equivalent parameters include: parallel equivalent resistance, series equivalent resistance, equivalent reactance and equivalent capacitance, and the second determination unit includes: a fifth determination module, used to determine the parallel equivalent resistance according to the second fitting coefficient, the third fitting coefficient and the fourth fitting coefficient using a seventh formula, wherein the seventh formula is: R1 represents a parallel equivalent resistance; a sixth determination module, used to determine the series equivalent resistance using an eighth formula according to the first fitting coefficient and the parallel equivalent resistance, wherein the eighth formula is: R2 represents the series equivalent resistance, and the first fitting coefficient, the second fitting coefficient, the third fitting coefficient and the fourth fitting coefficient are all one of the multiple fitting coefficients; the seventh determination module is used to determine the equivalent reactance using the ninth formula according to the fourth fitting coefficient and the series equivalent resistance, wherein the ninth formula is: L=α1R2, L represents the equivalent reactance; the eighth determination module is used to determine the equivalent voltage amplitude using the tenth formula according to the third fitting coefficient and the fourth fitting coefficient, wherein the tenth formula is: C represents the equivalent capacitance.

[0089] Optionally, the third determination unit includes: a ninth determination module, configured to determine an equivalent voltage amplitude of the equivalent power grid according to the equivalent parameter using an eleventh formula, wherein the eleventh formula is: V eq represents the equivalent voltage amplitude, P represents the active power of the access point, Q represents the reactive power of the access point, V represents the voltage amplitude of the access point, f0 represents the synchronization frequency, and the access point is the node where the new energy station is connected to the power grid.

[0090] Optionally, the equivalent grid determination device of the large grid further includes: a fourth acquisition unit, which is used to simulate sub-supersynchronous oscillation using the equivalent grid to obtain simulation results after constructing an equivalent grid equivalent to the grid according to equivalent parameters and equivalent voltage amplitudes.

[0091] According to another aspect of an embodiment of the present invention, a system for determining an equivalent power grid of a large power grid is provided. The system for determining an equivalent power grid of a large power grid uses any of the above-mentioned methods for determining an equivalent power grid of a large power grid.

[0092] According to another aspect of an embodiment of the present invention, a computer-readable storage medium is further provided. The computer-readable storage medium includes a stored program, wherein the program executes any one of the above-mentioned methods for determining an equivalent power grid of a large power grid.

[0093] Optionally, in this embodiment, the computer-readable storage medium may be located in any one of the computer terminals in a computer terminal group in a computer network, or in any one of the communication devices in a communication device group.

[0094] Optionally, in this embodiment, the computer-readable storage medium is configured to store a program code for executing the following steps: determining a sub-supersynchronous frequency range in which a sub-supersynchronous oscillation occurs in a power grid, wherein the sub-supersynchronous oscillation includes at least: a sub-synchronous oscillation and a super-synchronous oscillation, wherein the sub-synchronous oscillation refers to an oscillation phenomenon that occurs when the actual frequency of the power grid is lower than the synchronous frequency, and the super-synchronous oscillation refers to an oscillation phenomenon that occurs when the actual frequency of the power grid is higher than the synchronous frequency; performing an impedance scan on the power grid within the sub-supersynchronous frequency range at a predetermined frequency interval to obtain an actual impedance of the power grid at multiple frequency scanning points, wherein the frequency scanning point refers to a frequency point at which the impedance scanning of the power grid is performed; performing a polynomial fitting on the actual impedance to obtain an impedance transfer function of the actual impedance in the Laplace domain, wherein the impedance transfer function The transfer function is a function that describes the impedance characteristics of the power grid in the Laplace domain; the impedance transfer function is solved using actual impedance to obtain multiple fitting coefficients of the impedance transfer function, wherein the fitting coefficient is the coefficient of each term in the impedance transfer function; the equivalent parameters of the equivalent power grid are determined according to the multiple fitting coefficients, wherein the equivalent power grid is a power grid obtained by equivalent processing of the power grid, and the equivalent parameters are used to make the frequency response characteristics of the equivalent power grid within the sub-supersynchronous frequency range the same as the actual frequency response characteristics of the power grid within the sub-supersynchronous frequency range; the equivalent voltage amplitude of the equivalent power grid is determined according to the equivalent parameters, wherein the equivalent voltage amplitude is used to make the voltage of the equivalent power grid the same as the actual voltage of the power grid; and an equivalent power grid equivalent to the power grid is constructed according to the equivalent parameters and the equivalent voltage amplitude.

[0095] Optionally, in this embodiment, the computer-readable storage medium is configured to store a program code for executing the following steps: determining a predetermined frequency interval according to a first formula, wherein the first formula is: Δf represents the predetermined frequency interval, f a represents the starting frequency of the sub-supersynchronous frequency range, f b represents the end frequency of the sub-supersynchronous frequency range, N represents the total number of frequency scanning points; the scanning frequency value at each frequency scanning point is determined by using the second formula according to the predetermined frequency interval, wherein the second formula is: f i =f a +(i-1)Δf, i represents the number of the frequency scanning point, f i represents the scanning frequency value at the i-th frequency scanning point; the actual impedance at each frequency scanning point is determined by using the third formula according to the scanning frequency value, wherein the third formula is: Z(f i )=R(f i )+j*X(f i ), Z(f i ) represents the actual impedance at the i-th frequency scanning point, R(f i ) is the real part of the ith actual impedance, representing the resistance, X(f i) is the imaginary part of the ith actual impedance, represents reactance, and j represents an imaginary number.

[0096] Optionally, in this embodiment, the computer-readable storage medium is configured to store a program code for executing the following steps: in the process of performing polynomial fitting on the actual impedance, establishing a correlation relationship between the actual impedance and the impedance transfer function according to a fourth formula, wherein the fourth formula is: s = 2πf i *j, s represents the Laplace operator; the impedance transfer function is determined according to the fifth formula, where the fifth formula is: Z(s) represents the impedance transfer function, β0 is the first fitting coefficient of the term, β1 is the second fitting coefficient of the term, β2 is the third fitting coefficient of the term, and α1 is the fourth fitting coefficient of the term.

[0097] Optionally, in this embodiment, the computer-readable storage medium is configured to store a program code for executing the following steps: solving the impedance transfer function using the actual impedance according to the sixth formula to obtain a plurality of fitting coefficients of the impedance transfer function, wherein the sixth formula is:

[0098]

[0099] Optionally, in this embodiment, the computer-readable storage medium is configured to store a program code for executing the following steps: determining the parallel equivalent resistance using a seventh formula according to the second fitting coefficient, the third fitting coefficient, and the fourth fitting coefficient, wherein the seventh formula is: R1 represents a parallel equivalent resistance; the series equivalent resistance is determined using the eighth formula according to the first fitting coefficient and the parallel equivalent resistance, where the eighth formula is: R2 represents the equivalent resistance in series, and the first fitting coefficient, the second fitting coefficient, the third fitting coefficient and the fourth fitting coefficient are all fitting coefficients among the multiple fitting coefficients; the equivalent reactance is determined by the ninth formula according to the fourth fitting coefficient and the equivalent resistance in series, wherein the ninth formula is: L=α1R2, and L represents the equivalent reactance; the equivalent voltage amplitude is determined by the tenth formula according to the third fitting coefficient and the fourth fitting coefficient, wherein the tenth formula is: C represents the equivalent capacitance.

[0100] Optionally, in this embodiment, the computer-readable storage medium is configured to store a program code for executing the following steps: determining an equivalent voltage amplitude of an equivalent power grid according to an equivalent parameter using an eleventh formula, wherein the eleventh formula is: V eq represents the equivalent voltage amplitude, P represents the active power of the access point, Q represents the reactive power of the access point, V represents the voltage amplitude of the access point, f0 represents the synchronization frequency, and the access point is the node where the new energy station is connected to the power grid.

[0101] Optionally, in this embodiment, the computer-readable storage medium is configured to store program codes for executing the following steps: simulating sub-supersynchronous oscillations using an equivalent power grid to obtain simulation results.

[0102] According to another aspect of an embodiment of the present invention, a processor is further provided, and the processor is used to run a program, wherein when the program is run, any one of the above-mentioned methods for determining an equivalent power grid of a large power grid is executed.

[0103] According to another aspect of an embodiment of the present invention, a computer program product is provided, including computer instructions. When the computer instructions are executed by a processor, any one of the above-mentioned methods for determining an equivalent power grid of a large power grid is executed.

[0104] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0105] In the above embodiments of the present invention, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0106] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only schematic. For example, the division of the units can be a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of units or modules, which can be electrical or other forms.

[0107] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0108] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0109] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), mobile hard disk, magnetic disk or optical disk and other media that can store program codes.

[0110] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for determining an equivalent power grid of a large power grid, characterized in that: include: Determine a sub-supersynchronous frequency range in which a sub-supersynchronous oscillation occurs in a power grid, wherein the sub-supersynchronous oscillation includes at least: a sub-synchronous oscillation and a super-synchronous oscillation, wherein the sub-synchronous oscillation refers to an oscillation phenomenon that occurs when the actual frequency of the power grid is lower than the synchronous frequency, and the super-synchronous oscillation refers to an oscillation phenomenon that occurs when the actual frequency of the power grid is higher than the synchronous frequency; Performing impedance scanning on the power grid within the sub-supersynchronous frequency range at a predetermined frequency interval to obtain actual impedance of the power grid at a plurality of frequency scanning points, wherein the frequency scanning point refers to a frequency point at which impedance scanning of the power grid is performed; Performing polynomial fitting on the actual impedance to obtain an impedance transfer function of the actual impedance in the Laplace domain, wherein the impedance transfer function is a function that describes the impedance characteristics of the power grid in the Laplace domain; Solving the impedance transfer function using the actual impedance to obtain a plurality of fitting coefficients of the impedance transfer function, wherein the fitting coefficients are coefficients of each term in the impedance transfer function; Determining equivalent parameters of an equivalent power grid according to the plurality of fitting coefficients, wherein the equivalent power grid is a power grid obtained by performing equivalent processing on the power grid, and the equivalent parameters are used to make the frequency response characteristics of the equivalent power grid within the sub-supersynchronous frequency range the same as the actual frequency response characteristics of the power grid within the sub-supersynchronous frequency range; Determining an equivalent voltage amplitude of the equivalent power grid according to the equivalent parameter, wherein the equivalent voltage amplitude is used to make the voltage of the equivalent power grid the same as the actual voltage of the power grid; The equivalent power grid equivalent to the power grid is constructed according to the equivalent parameters and the equivalent voltage amplitudes.

2. The method for determining an equivalent power grid of a large power grid according to claim 1, characterized in that: Performing impedance scanning on the power grid within the sub-supersynchronous frequency range at a predetermined frequency interval to obtain actual impedance of the power grid at multiple frequency scanning points includes: The predetermined frequency interval is determined according to a first formula, wherein the first formula is: Δf represents the predetermined frequency interval, f a represents the starting frequency of the sub-supersynchronous frequency range, f b represents the end frequency of the sub-supersynchronous frequency range, and N represents the total number of frequency scanning points; The scanning frequency value at each frequency scanning point is determined by using a second formula according to the predetermined frequency interval, wherein the second formula is: i =f a +(i-1)Δf, i represents the number of the frequency scanning point, f i represents the scanning frequency value at the i-th frequency scanning point; The actual impedance at each frequency scanning point is determined using a third formula according to the scanning frequency value, wherein the third formula is: Z(f i )=R(f i )+j*X(f i ), Z(f i ) represents the actual impedance at the i-th frequency scanning point, R(f i ) is the real part of the i-th actual impedance, representing the resistance, X(f i ) is the imaginary part of the i-th actual impedance, represents reactance, and j represents an imaginary number.

3. The method for determining an equivalent power grid of a large power grid according to claim 1, characterized in that: Performing polynomial fitting on the actual impedance to obtain an impedance transfer function of the actual impedance in the Laplace domain includes: In the process of performing polynomial fitting on the actual impedance, a correlation relationship between the actual impedance and the impedance transfer function is established according to a fourth formula, wherein the fourth formula is: s=2πf i *j, s represents the Laplace operator; The impedance transfer function is determined according to a fifth formula, wherein the fifth formula is: Z(s) represents the impedance transfer function, β0 is the first fitting coefficient of the term, β1 is the second fitting coefficient of the term, β2 is the third fitting coefficient of the term, and α1 is the fourth fitting coefficient of the term.

4. The method for determining an equivalent power grid of a large power grid according to claim 1, characterized in that: The impedance transfer function is solved by using the actual impedance to obtain a plurality of fitting coefficients of the impedance transfer function, including: The impedance transfer function is solved using the actual impedance according to a sixth formula to obtain a plurality of fitting coefficients of the impedance transfer function, wherein the sixth formula is:

5. The method for determining an equivalent power grid of a large power grid according to claim 1, characterized in that: The equivalent parameters include: parallel equivalent resistance, series equivalent resistance, equivalent reactance and equivalent capacitance. The equivalent parameters of the equivalent power grid are determined according to a plurality of the fitting coefficients, including: The parallel equivalent resistance is determined using a seventh formula according to the second fitting coefficient, the third fitting coefficient, and the fourth fitting coefficient, wherein the seventh formula is: R1 represents the parallel equivalent resistance; The series equivalent resistance is determined by using an eighth formula according to the first fitting coefficient and the parallel equivalent resistance, wherein the eighth formula is: R2 represents the series equivalent resistance, and the first fitting coefficient, the second fitting coefficient, the third fitting coefficient and the fourth fitting coefficient are all one of the fitting coefficients; Determine the equivalent reactance using a ninth formula according to the fourth fitting coefficient and the series equivalent resistance, wherein the ninth formula is: L=α1R2, where L represents the equivalent reactance; The equivalent voltage amplitude is determined using a tenth formula according to the third fitting coefficient and the fourth fitting coefficient, wherein the tenth formula is: C represents the equivalent voltage amplitude.

6. The method for determining an equivalent power grid of a large power grid according to claim 1, characterized in that: Determining the equivalent voltage amplitude of the equivalent power grid according to the equivalent parameter includes: The equivalent voltage amplitude of the equivalent power grid is determined according to the equivalent parameter using an eleventh formula, wherein the eleventh formula is: V eq represents the equivalent voltage amplitude, P represents the active power of the access point, Q represents the reactive power of the access point, V represents the voltage amplitude of the access point, f0 represents the synchronization frequency, and the access point is the node where the new energy station accesses the power grid.

7. The method for determining an equivalent power grid of a large power grid according to claim 1, characterized in that: After constructing the equivalent power grid equivalent to the power grid according to the equivalent parameters and the equivalent voltage amplitude, the method further includes: The sub-supersynchronous oscillation is simulated using the equivalent power grid to obtain a simulation result.

8. A device for determining an equivalent power grid of a large power grid, characterized in that: include: A first determining unit is used to determine a sub-supersynchronous frequency range in which a sub-supersynchronous oscillation occurs in a power grid, wherein the sub-supersynchronous oscillation includes at least: a sub-synchronous oscillation and a super-synchronous oscillation, wherein the sub-synchronous oscillation refers to an oscillation phenomenon that occurs when the actual frequency of the power grid is lower than the synchronous frequency, and the super-synchronous oscillation refers to an oscillation phenomenon that occurs when the actual frequency of the power grid is higher than the synchronous frequency; A first acquisition unit is used to perform impedance scanning on the power grid within the sub-supersynchronous frequency range according to a predetermined frequency interval to obtain actual impedance of the power grid at multiple frequency scanning points, wherein the frequency scanning point refers to a frequency point at which impedance scanning is performed on the power grid; a second acquisition unit, configured to perform polynomial fitting on the actual impedance to obtain an impedance transfer function of the actual impedance in a Laplace domain, wherein the impedance transfer function is a function that describes the impedance characteristics of the power grid in the Laplace domain; a third acquisition unit, configured to solve the impedance transfer function using the actual impedance to obtain a plurality of fitting coefficients of the impedance transfer function, wherein the fitting coefficients are coefficients of each term in the impedance transfer function; a second determining unit, configured to determine equivalent parameters of an equivalent power grid according to the plurality of fitting coefficients, wherein the equivalent power grid is a power grid obtained by performing equivalent processing on the power grid, and the equivalent parameters are used to make the frequency response characteristics of the equivalent power grid within the sub-supersynchronous frequency range the same as the actual frequency response characteristics of the power grid within the sub-supersynchronous frequency range; a third determining unit, configured to determine an equivalent voltage amplitude of the equivalent power grid according to the equivalent parameter, wherein the equivalent voltage amplitude is used to make the voltage of the equivalent power grid the same as the actual voltage of the power grid; A construction unit is used to construct the equivalent power grid equivalent to the power grid according to the equivalent parameters and the equivalent voltage amplitude.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored program, wherein the program executes the method for determining an equivalent power grid of a large power grid according to any one of claims 1 to 7.

10. A computer program product comprising computer instructions, characterized in that: When the computer instructions are executed by a processor, the method for determining an equivalent power grid of a large power grid as claimed in any one of claims 1 to 7 is performed.

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