Passivity index based new energy external characteristic driving source-grid coordination stability judgment method

Abstract

The application discloses a new energy external characteristic driving source network coordination stability judgment method based on passivity index, comprising the following steps: modeling a new energy base power system, and calculating a generalized short-circuit ratio of the new energy base power system; calculating a return ratio matrix of the new energy base power system according to the modeling of the new energy base power system and electromagnetic dynamics of a line, and correspondingly calculating the reciprocal of the minimum passivity index of the new energy base power system in a low frequency band; if the reciprocal of the minimum passivity index is less than or equal to the generalized short-circuit ratio, the state of the new energy base power system is small disturbance stability, otherwise, the state of the new energy base power system is small disturbance instability; the application proposes a source network coordination small disturbance stability criterion based on new energy external characteristic driving for a new energy multi-infeed system with different external characteristics, and the stability criterion only relies on the medium frequency band passivity index of the new energy grid-connected equipment and the generalized short-circuit ratio of the alternating current system, and has good practicability and small conservativeness.

Description

Technical Field

[0001] This invention relates to the technical field of power converters, and in particular to a method for coordinating and determining the stability of new energy sources driven by external characteristics based on a passive index. Background Technology

[0002] New energy power generation, represented by wind and solar power, is gradually replacing thermal power generation. Simultaneously, the increasing proportion of power electronic equipment and the relative decrease in the proportion of synchronous machines are pushing the carrying capacity of AC power grids close to their inherent limits, leading to broadband oscillations. To characterize the carrying capacity limit of multi-infeed power electronic systems and reflect the interaction strength between the high impedance characteristics of weak power grids and new energy control systems, many scholars both domestically and internationally have studied and defined the short-circuit ratio index for multi-infeed systems to quantify grid strength from the perspective of small-disturbance stability.

[0003] Among these, the critical value of the short-circuit ratio for multi-infeed systems based on the small-gain theorem can serve as a sufficient condition for system stability, but it is too conservative. Analytical methods based on perturbation-based approximate calculations or simplified models lack sufficient conditions to guarantee system stability. Therefore, the study of grid strength in heterogeneous multi-infeed systems still faces a contradiction between the sufficiency of the indices and the conservatism of the critical value. Further research is needed to ensure sufficient grid strength conditions for the stability of heterogeneous systems and to reduce the conservatism of the critical short-circuit ratio. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] In view of the aforementioned existing problems, the present invention is proposed.

[0006] Therefore, this invention provides a new energy external characteristic-driven source-network coordination stability judgment method based on the passive index, which improves the conservatism of existing small-disturbance stability judgment methods. That is, for different stability problems, the frequency band range is further expanded or changed according to more information of the actual system to improve the conservatism of the stability judgment method.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution, including: modeling the power system of the new energy base and calculating the generalized short-circuit ratio of the power system of the new energy base; calculating the return ratio matrix of the power system of the new energy base based on the modeling of the power system of the new energy base and the electromagnetic dynamics of the line, and correspondingly calculating the negative number of its minimum passive index in the low-frequency band; if the negative number of the minimum passive index is less than or equal to the generalized short-circuit ratio, the state of the power system of the new energy base is small-disturbance stable; otherwise, the state of the power system of the new energy base is small-disturbance unstable.

[0008] As a preferred embodiment of the new energy external characteristic-driven source-grid coordination stability determination method based on the passive index described in this invention, the calculation of the back-current ratio matrix of the new energy base power system includes: establishing a single-infeed system, constructing the closed-loop characteristic equation of the single-infeed system, and obtaining the back-current ratio matrix of the single-infeed system; establishing a stability determination criterion for the single-infeed system based on the back-current ratio matrix of the single-infeed system; obtaining sufficient conditions for small-disturbance stability of the single-infeed system based on the back-current ratio matrix and the stability determination criterion of the single-infeed system; and deriving sufficient conditions for small-disturbance stability of the new energy base power system, i.e., the heterogeneous multi-infeed system.

[0009] As a preferred embodiment of the new energy external characteristic-driven source-grid coordination stability judgment method based on the passive index described in this invention, the single-feed system includes a pure inductive network and a converter; frequency domain admittance models Yi are established for both the pure inductive network and the converter, pointing inwards from their respective ports. net (s), Y PEDxy (s) Modeling of a single-feed system; wherein, the frequency domain admittance model Y of the purely inductive network port-inward. net (s) is:

[0010]

[0011] Frequency domain admittance model Y of converter port inward PEDxy (s) is:

[0012]

[0013] In the formula, B = 1 / (ω0L), where ω0 is the rated frequency of the AC power grid, and L is the equivalent inductance of the AC power grid; Y PEDdq (s) represents the equipment admittance in the phase-locked loop control coordinate system dq, S B G is the rated capacity of power electronic equipment. dd G dq G qd and G qq Let M and θ represent the input and output transfer functions of the device, i.e., the current response to voltage disturbances. M is the coordinate transformation matrix, and θ is the phase angle of the voltage at the device feed point.

[0014] As a preferred embodiment of the new energy external characteristic-driven source-grid coordination stability determination method based on the passive index described in this invention, it includes: the closed-loop characteristic equation of the single-feed system is:

[0015]

[0016] A single-feed system is stable when the hysteresis matrix satisfies the following equation:

[0017]

[0018] Equivalent to:

[0019]

[0020] The right-hand side of the above inequality has the same form as the definition of the input passivity exponent, and therefore can be further simplified to:

[0021]

[0022] Where H represents the conjugate transpose, ω is the frequency, j is the imaginary unit, and a matrix ≥ 0 represents a positive semi-definite matrix, meaning that all eigenvalues ​​of the matrix are not less than 0; λ i (·) represents the i-th eigenvalue of the matrix, Re(·) represents taking the real part of the complex number; IPI(·) represents the passivity exponent. S is the back-compass ratio matrix of a single-infeed system; SCR is the short-circuit capacity S of a single-infeed system. ac With the rated capacity S of power electronic equipment B The ratio of .

[0023] As a preferred embodiment of the new energy external characteristic-driven source-grid coordination stability judgment method based on the passive index described in this invention, the modeling of the heterogeneous multi-infeed system includes: establishing the device-side frequency domain admittance model Y respectively. multi_PEDxy (s) and network-side frequency domain admittance model Y multi_net (s);

[0024] Among them, the equipment-side frequency domain admittance model Y multi_PEDxy (s) is:

[0025]

[0026]

[0027] Network-side frequency domain admittance model Y multi_net (s) is:

[0028]

[0029] In the formula, SBi ,i=1,...,n represents the rated capacity of the i-th power electronic device, and diag(·) represents a diagonal matrix, with symbols Y represents PEDxy Multiply the diagonal blocks of (s) by the diagonal elements of S; symbol represents the Kronecker product, and B represents the node admittance matrix of the heterogeneous multi-feed system.

[0030] As a preferred embodiment of the new energy external characteristic-driven source-grid coordination stability determination method based on the passive index described in this invention, it includes: [the method includes] based on the equipment-side frequency domain admittance model Y... multi_PEDxy (s) and network-side frequency domain admittance model Y multi_net (s), to obtain the backlash matrix of the heterogeneous multi-feed system:

[0031]

[0032] Based on the return matrix c multi (s) Establish the closed-loop characteristic equation of the heterogeneous multi-feed system:

[0033]

[0034] Among them, symbols Represents Y PEDxy Each diagonal block of (s) is multiplied by

[0035] As a preferred embodiment of the new energy external characteristic-driven source-grid coordination stability judgment method based on the passive index described in this invention, the generalized short-circuit ratio includes:

[0036] gSCR=minλ{S -1 B}

[0037] Where gSCR is the generalized short-circuit ratio.

[0038] As a preferred embodiment of the new energy external characteristic-driven source-grid coordination stability determination method based on the passive index described in this invention, it includes: analyzing the stability of heterogeneous multi-infeed systems based on the generalized Nyquist criterion and through the characteristic trajectory of the back-ratio matrix, wherein the original back-ratio matrix of the heterogeneous multi-infeed system is assumed to be... The characteristic trajectory is closest to the point (-1, 0) in the low-to-mid frequency band (1–100 Hz), and far from the point (-1, 0) in other frequency bands. Furthermore, it does not intersect the negative real axis between the point (-1, 0) and infinity. Therefore, sufficient conditions for the small-disturbance stability of the power system in the new energy base can be obtained:

[0039]

[0040] Among them, YPEDxy,i (s) is the frequency domain admittance model of the i-th converter port inward, and IPI is the input passivity index.

[0041] As a preferred embodiment of the new energy external characteristic-driven source-grid coordination stability judgment method based on the passive index described in this invention, the method includes: the distance between the lower limit of the generalized short-circuit ratio and the critical short-circuit ratio obtained by time-domain simulation can be minimized.

[0042] The beneficial effects of this invention are as follows: This invention proposes a source-grid coordination small-disturbance stability criterion based on the external characteristics of new energy multi-infeed systems with different external characteristics. The stability criterion relies only on the mid-frequency passive index of the grid-connected new energy equipment and the generalized short-circuit ratio of the AC system. It can be implemented separately by the new energy power plants and the power grid company, and has good practicality. At the same time, the criterion is a sufficient condition and its conservatism is relatively small. Attached Figure Description

[0043] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0044] Figure 1 The equivalent circuit diagram of the single-feed system of the new energy external characteristic-driven source-grid coordination stability judgment method based on the passive index described in the first embodiment of the present invention;

[0045] Figure 2 This is a schematic diagram of a multi-feed system for the source-grid coordination and stability determination method based on the passive index driven by the external characteristics of new energy sources, as described in the first embodiment of the present invention.

[0046] Figure 3 The phase-locked loop parameters of the new energy external characteristic-driven source-grid coordination stability judgment method based on the passive index described in the second embodiment of the present invention are the extended passive index and damping ratio of the system at 26+7800 / s.

[0047] Figure 4 The phase-locked loop parameters of the new energy external characteristic-driven source-grid coordination stability judgment method based on the passive index described in the second embodiment of the present invention are the extended passive index and damping ratio of the system at 36+7800 / s.

[0048] Figure 5 The phase-locked loop parameters of the new energy external characteristic-driven source-grid coordination stability judgment method based on the passive index described in the second embodiment of the present invention are the extended passive index and damping ratio of the system at 26+3800 / s.

[0049] Figure 6 The phase-locked loop parameters of the new energy external characteristic-driven source-grid coordination stability judgment method based on the passive index described in the second embodiment of the present invention are the extended passive index and damping ratio of the system at 36+3800 / s.

[0050] Figure 7 The time-domain simulation result shows that the generalized short-circuit ratio (SCR) of the system based on the passive index-driven source-grid coordination stability judgment method for new energy external characteristics is 3.41, as described in the second embodiment of the present invention.

[0051] Figure 8 The time-domain simulation result shows that the generalized short-circuit ratio (SCR) of the system based on the passive index-driven source-grid coordination stability judgment method for new energy external characteristics is 1.96, as described in the second embodiment of the present invention. Detailed Implementation

[0052] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0053] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0054] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0055] This invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of this invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not be construed as limiting the scope of protection of this invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0056] Furthermore, in the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used solely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In addition, the terms "first," "second," or "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0057] Unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" in this invention should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; similarly, they can refer to mechanical connections, electrical connections, or direct connections, or indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0058] Example 1

[0059] Reference Figures 1-2 This is the first embodiment of the present invention, which provides a new energy external characteristic-driven source-grid coordination stability determination method based on the passivity index, including:

[0060] S1: Model the power system of the new energy base and calculate the generalized short-circuit ratio of the power system of the new energy base.

[0061] (1) Modeling

[0062] ① Model the single-feed system.

[0063] A single-infeed system refers to a system where a single converter is fed into an infinite power grid; the specific equivalent circuit diagram is as follows: Figure 1 As shown, where U, θ and I, These represent the amplitude / phase angle of the voltage at the equipment feed point and the amplitude / phase angle of the injected current, respectively; E is the equivalent internal potential of the AC system (in this embodiment, the phase angle of the equivalent bus of the AC system is rigid, focusing on the voltage support strength); and z is the equivalent impedance of the AC system.

[0064] Specifically, frequency domain admittance models Y are established for both the purely inductive network and the converter, pointing inwards from their ports. net (s), Y PEDxy (s) Model the single-feed system;

[0065] Among them, the frequency domain admittance model Y of the port-in of a purely inductive network net (s) is:

[0066]

[0067] The device admittance Y in coordinate system dq is controlled by a phase-locked loop (PLL). PEDdq (s) Perform coordinate transformation to obtain the frequency domain admittance model Y of the converter port inward. PEDxy (s):

[0068]

[0069] In the formula, B = 1 / (ω0L), where ω0 is the rated frequency of the AC power grid, and L is the equivalent inductance of the AC power grid; Y PEDdq (s) represents the equipment admittance in the phase-locked loop control coordinate system dq, S B G is the rated capacity of power electronic equipment. dd G dq G qd and G qq Let M and θ represent the input and output transfer functions of the device, i.e., the current response to voltage disturbances. M is the coordinate transformation matrix, and θ is the phase angle of the voltage at the device feed point.

[0070] ② Model the power system (heterogeneous multi-infeed system) of the new energy base;

[0071] Reference Figure 2 A multi-infeed system refers to a single-infeed system in which multiple converters (PED1 to PEDn) are connected to an infinite power grid through a specific connection method; the frequency domain admittance model Y on the equipment side is established respectively. multi_PEDxy (s) and network-side frequency domain admittance model Y multi_net (s) Establish a heterogeneous multi-feed system;

[0072] Among them, the equipment-side frequency domain admittance model Y multi_PEDxy (s) is:

[0073]

[0074]

[0075] Network-side frequency domain admittance model Y multi_net (s) is:

[0076]

[0077] In the formula, S Bi ,i=1,...,n represents the rated capacity of the i-th power electronic device, and diag(·) represents a diagonal matrix, with symbols Y represents PEDxy Multiply the diagonal blocks of (s) by the diagonal elements of S; symbol represents the Kronecker product, and B represents the node admittance matrix of the heterogeneous multi-feed system.

[0078] (2) Calculate the generalized short-circuit ratio

[0079] gSCR=minλ{S -1 B}

[0080] Where gSCR is the generalized short-circuit ratio.

[0081] S2: Based on the modeling of the power system of the new energy base and the electromagnetic dynamics of the lines, calculate the back ratio matrix of the power system of the new energy base, and calculate the negative number of its minimum passive index in the low and medium frequency band.

[0082] (1) Construct the closed-loop characteristic equation of the single-feed system and obtain the back ratio matrix of the single-feed system;

[0083] According to multivariable feedback control theory Figure 1 The stability of a single-feed system is determined by the zeros of the determinant of the hysteresis matrix, where the hysteresis matrix is:

[0084]

[0085] Where I2 is the identity matrix.

[0086] The closed-loop characteristic equation of a single-feed system can be derived from the backlash matrix c(s):

[0087]

[0088] In the frequency domain model, the passivity of a system is equivalent to the positive reality of its transfer function. For a MIMO passive system, the system is passive if its hysteresis matrix satisfies the condition in the following formula. Furthermore, if the system under study is a minimum-order system, passivity is also a sufficient condition for its stability in the Lyapunov sense. The specific formula is as follows:

[0089]

[0090] Equivalent to:

[0091]

[0092] The right-hand side of the above inequality has the same form as the definition of the input passivity exponent, and therefore can be further simplified to:

[0093]

[0094] Where H represents the conjugate transpose, ω is the frequency, j is the imaginary unit, and a matrix ≥ 0 represents a positive semi-definite matrix, meaning that all eigenvalues ​​of the matrix are not less than 0; λ i(·) represents the i-th eigenvalue of the matrix, Re(·) represents taking the real part of the complex number; IPI(·) represents the passivity exponent. The back-comparison matrix of a single-feed system;

[0095] SCR is the short-circuit capacity of a single-infeed system. ac With the rated capacity S of power electronic equipment B The ratio (rated voltage U) N ≈1):

[0096]

[0097] (2) Establish the stability criterion for a single-feed system based on the back ratio matrix of the single-feed system;

[0098] For example Figure 1 The single-feed system shown is subject to the following assumptions:

[0099] The system under study may exhibit mid-frequency oscillations dominated by a phase-locked loop, or from a geometric perspective, the system's hysteresis matrix... The characteristic trajectory is closest to the point (-1, 0) on the complex plane when ω∈[1,100](Hz), and is far away from the point (-1, 0) in other frequency bands, and does not intersect with the negative real axis between the point (-1, 0) and the point at infinity.

[0100] Therefore, the sufficient condition for the stability of a single-feed system under small disturbances is:

[0101]

[0102] (3) Based on the back ratio matrix and stability criterion of the single-infeed system, the sufficient condition for small-disturbance stability of the single-infeed system is obtained. Based on this, the sufficient condition for small-disturbance stability of the new energy base power system, i.e., the heterogeneous multi-infeed system, is derived. That is, if the negative number of the minimum passive index is less than or equal to the generalized short-circuit ratio, the state of the new energy base power system is small-disturbance stable; otherwise, the state of the new energy base power system is small-disturbance unstable.

[0103] According to the equipment-side frequency domain admittance model Y multi_PEDxy (s) and network-side frequency domain admittance model Y multi_net (s), to obtain the backlash matrix of the heterogeneous multi-feed system:

[0104]

[0105] Based on the return matrix c multi (s) Establish the closed-loop characteristic equation of the heterogeneous multi-feed system:

[0106]

[0107] Among them, symbols Represents Y PEDxy Each diagonal block of (s) is multiplied by is the back ratio matrix of a heterogeneous multi-feed system.

[0108] Furthermore, according to the generalized Nyquist criterion, the stability of heterogeneous multi-feed systems can be determined by the back-ratio matrix. Analyzing the characteristic trajectory, if the characteristic trajectory does not encircle the point (-1, 0), the stability of the multi-infeed system can be guaranteed. Therefore, similar to the single-infeed system, assuming that the characteristic trajectory of the multi-infeed system is also closest to the point (-1, 0) in the mid-to-low frequency range of 1–100 Hz, the sufficient condition for system stability can also be obtained, namely:

[0109] Original back ratio matrix of heterogeneous multi-feed system The characteristic trajectory is closest to the point (-1, 0) in the low-to-mid frequency band (1–100 Hz), and far from the point (-1, 0) in other frequency bands. Furthermore, it does not intersect the negative real axis between the point (-1, 0) and infinity. Therefore, sufficient conditions for the small-disturbance stability of the power system in the new energy base can be obtained:

[0110]

[0111] Among them, Y PEDxy,i (s) is the frequency domain admittance model of the i-th converter port inward, and IPI is the input passivity index.

[0112] The conservatism of this sufficient condition is determined by the frequency band range considered. Currently, only the low-to-mid frequency band is considered for the oscillation problem dominated by the phase-locked loop. If the frequency band range can be further narrowed based on more information about the actual system, the conservatism of the criterion can be reduced. For example, when the accurate frequency range of the weakly damped multi-feed system is known, the distance between the lower limit of the generalized short-circuit ratio obtained by this sufficient condition and the critical short-circuit ratio obtained by time-domain simulation can be minimized. In addition, if the strong coupling between the phase-locked loop and other components is considered, such as the high oscillation frequency caused by the coupling between the phase-locked loop and the inner loop, the sufficient condition for system stability can also be obtained by expanding the frequency band range of the analysis to include the oscillation frequency.

[0113] Example 2

[0114] This embodiment uses the Matlab / Simulink platform to simulate and analyze a new energy feed-in system to verify the effectiveness of the proposed method.

[0115] Specifically, Figures 3-6The extended passive index of a single-feed system in the mid-frequency range of 1–100 Hz is presented under four sets of different phase-locked loop parameters (26+7800 / s, 36+7800 / s, 26+3800 / s, 36+3800 / s). The frequency units in the figures are radians per second (rad / s). Figures 3-6 It can be seen that the minimum value of the extended passive index is within 100 rad / s, while the passive index of other frequency bands is larger. At the same time, in order to facilitate the observation of the passive index distribution in the mid-to-low frequency band, the high-frequency characteristics are not listed.

[0116] Furthermore, by using the negative of the minimum value of the extended passive index, the stability criteria for a single-infeed system under four sets of parameters can be obtained: the short-circuit ratio (SCR) under the four sets of parameters is no less than 3.3, 2.6, 2.1, and 1.7, respectively. However, if modal analysis is performed using detailed system parameters, and the critical short-circuit ratio (CSCR) is determined based on the dominant mode damping ratio being 0, the accurate critical short-circuit ratios (CSCR) are 2.4, 1.9, 1.4, and 1.2, respectively. It can be seen that the analysis results also indicate that the stability criteria for a single-infeed system has a certain degree of conservatism, that is, the minimum short-circuit ratio under the stability criteria of a single-infeed system is greater than the critical short-circuit ratio. It is worth noting that the stability criteria for a single-infeed system can be driven by the frequency sweep data of the new energy converter port, avoiding dependence on detailed models and parameters. Therefore, it gains convenience in application at the cost of a certain degree of conservatism.

[0117] Since the small-interference instability problem in the mid-to-low frequency band is greatly affected by the grid strength and phase-locked loop parameters, here we only construct a heterogeneous multi-infeed system based on the above four sets of phase-locked loop parameters to analyze the effectiveness of the sufficient conditions for small-interference stability in the multi-infeed system.

[0118] A three-feed system is set up, with the grid-connected devices using the first three sets of the four sets of phase-locked loop parameters mentioned above. The node admittance matrix on the network side is as follows (per-unit parameters):

[0119]

[0120] With the device capacities corresponding to the three sets of phase-locked loop parameters set to 3 p.u. and 1.9 p.u. (three converters with the same capacity), and combining the network admittance matrix B, we know that the generalized short-circuit ratios of the system under the two capacity configurations are 3.41 and 1.96, respectively. Furthermore, according to the sufficient condition for small-disturbance stability and the extended passive index, we know that the sufficient condition for the stability of the three-feed system is that gSCR is not less than 3.3.

[0121] Figures 7-8 Time-domain simulation results considering port voltage disturbances are presented under two sets of capacity parameters. Figure 7The result is when the generalized short-circuit ratio of the system is 3.41. Since 3.41 > 3.3 (the negative of the extended passive index), the system satisfies the stability criterion of sufficient condition for small disturbance stability. Therefore, after experiencing voltage amplitude disturbance, the output power of the three converters can converge to the rated value.

[0122] Figure 8 The results are for a generalized short-circuit ratio of 1.96. Since 3.3 > 1.96, the system does not meet the criterion for sufficient stability under small disturbances. Furthermore, the grid strength of the system is between the critical short-circuit ratios of the three converters with different parameters (1.4 to 2.4). Therefore, the system is at risk of instability. When the node voltage is bypassed, the active power of the three converters diverges, and the system becomes unstable under small disturbances. The time-domain simulation results also demonstrate the effectiveness of this method.

[0123] It should be recognized that embodiments of the present invention can be implemented or carried out by computer hardware, a combination of hardware and software, or by computer instructions stored in a non-transitory computer-readable storage medium. The method can be implemented using standard programming techniques—including a non-transitory computer-readable storage medium configured with a computer program, wherein such a storage medium causes the computer to operate in a specific and predefined manner—according to the methods and drawings described in the specific embodiments. Each program can be implemented in a high-level procedural or object-oriented programming language to communicate with the computer system. However, if desired, the program can be implemented in assembly or machine language. In any case, the language can be a compiled or interpreted language. Furthermore, for this purpose, the program can run on a programmed application-specific integrated circuit (ASIC).

[0124] Furthermore, the procedures described herein may be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by the context. The procedures described herein (or variations and / or combinations thereof) may be executed under the control of one or more computer systems configured with executable instructions, and may be implemented by hardware or a combination thereof as code (e.g., executable instructions, one or more computer programs, or one or more applications) that commonly executes on one or more processors. The computer program comprises a plurality of instructions executable by one or more processors.

[0125] Furthermore, the method can be implemented in any suitable type of computing platform, including but not limited to personal computers, minicomputers, mainframes, workstations, networked or distributed computing environments, standalone or integrated computer platforms, or in communication with charged particle tools or other imaging devices, etc. Aspects of the invention can be implemented as machine-readable code stored on a non-transitory storage medium or device, whether removable or integrated into a computing platform, such as a hard disk, optical read and / or write storage medium, RAM, ROM, etc., such that it is readable by a programmable computer, and when the storage medium or device is read by the computer, it can be used to configure and operate the computer to perform the processes described herein. Furthermore, the machine-readable code, or portions thereof, can be transmitted via wired or wireless networks. The invention described herein includes these and other different types of non-transitory computer-readable storage media when such media comprises instructions or programs that implement the steps described above in conjunction with a microprocessor or other data processor. When programmed according to the methods and techniques described herein, the invention also includes the computer itself. A computer program can be applied to input data to perform the functions described herein, thereby transforming the input data to generate output data stored in non-volatile memory. The output information can also be applied to one or more output devices such as a display. In a preferred embodiment of the invention, the converted data represents physical and tangible objects, including specific visual depictions of physical and tangible objects generated on a display.

[0126] As used herein, the terms “component,” “module,” “system,” etc., are intended to refer to a computer-related entity, which may be hardware, firmware, a combination of hardware and software, software, or running software. For example, a component may be, but is not limited to, a process running on a processor, a processor, an object, an executable file, a running thread, a program, and / or a computer. As an example, an application running on a computing device and the computing device itself can both be components. One or more components may reside in a running process and / or thread, and components may be located in a single computer and / or distributed among two or more computers. Furthermore, these components are capable of execution from various computer-readable media having various data structures thereon. These components may communicate locally and / or remotely via signals, such as based on one or more data packets (e.g., data from a component that interacts with a local system, another component in a distributed system, and / or signals that interact with other systems via a network such as the Internet).

[0127] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for determining the stability of a new energy source-grid coordinated system based on the passive index, characterized in that: include: Model the power system of the new energy base and calculate the generalized short-circuit ratio of the power system of the new energy base; Based on the modeling of the power system of the new energy base and the electromagnetic dynamics of the lines, the back ratio matrix of the power system of the new energy base is calculated, and the negative number of its minimum passivity index in the low and medium frequency band is calculated accordingly. If the negative of the minimum passivity index is less than or equal to the generalized short-circuit ratio, the power system of the new energy base is in a state of small-disturbance stability; otherwise, the power system of the new energy base is in a state of small-disturbance instability. The calculation of the back-comparison matrix of the power system in the new energy base includes: Establish a single-feed system, construct the closed-loop characteristic equation of the single-feed system, and obtain the back ratio matrix of the single-feed system. Establish a stability criterion for a single-feed system based on the back ratio matrix of the single-feed system; Based on the back-comparison matrix and stability criterion of the single-infeed system, sufficient conditions for small-disturbance stability of the single-infeed system are obtained. Based on this, sufficient conditions for small-disturbance stability of the power system in the new energy base, i.e., the heterogeneous multi-infeed system, are derived.

2. The method for determining the stability of a new energy source-grid coordination driven by the passive index as described in claim 1, characterized in that, A single-feed system consists of a purely inductive network and a converter; Frequency domain admittance models are established for both the purely inductive network and the converter, pointing inwards from their ports. , Model the single-feed system; Among them, the frequency domain admittance model of port-in of a purely inductive network. for: Frequency domain admittance model of converter port inward for: In the formula, , , , Where L is the rated frequency of the AC power grid, and L is the equivalent inductance of the AC power grid. Let be the device admittance in the phase-locked loop control coordinate system dq. The rated capacity of power electronic equipment. , , and These represent the device's input and output transfer functions, i.e., the current response to voltage disturbances. M This is the coordinate transformation matrix. This refers to the phase angle of the voltage at the device's feed point.

3. The method for determining the stability of a new energy source-grid coordination driven by the passive index as described in claim 2, characterized in that, include: The closed-loop characteristic equation of a single-feed system is: A single-feed system is stable when the hysteresis matrix satisfies the following equation: Equivalent to: The right-hand side of the above inequality has the same form as the definition of the input passivity exponent, and therefore can be further simplified to: Where H represents the conjugate transpose. Let j be the frequency, j be the imaginary unit, and the matrix be... This represents a positive semi-definite matrix, meaning that all eigenvalues ​​of the matrix are not less than 0; This represents the i-th eigenvalue of the matrix. Represents taking the real part of a complex number; Represents the passivity index; The return ratio matrix of a single-infeed system is given; SCR is the short-circuit capacity of a single-infeed system. Rated capacity of power electronic equipment The ratio of .

4. The method for determining the stability of new energy source-grid coordination based on the passive index as described in claim 3, characterized in that, Modeling of heterogeneous multi-feed systems includes: Establish frequency domain admittance models on the equipment side respectively and network-side frequency domain admittance model ; Among them, the equipment-side frequency domain admittance model for: Network-side frequency domain admittance model for: In the formula, This represents the rated capacity of the i-th power electronic device. Represents a diagonal matrix, symbol express Multiply the diagonal blocks by the diagonal elements of S; symbol Represents the Kronecker product. B This represents the node admittance matrix of a heterogeneous multi-feed system.

5. The method for determining the stability of a new energy source-grid coordination driven by the passive index as described in claim 4, characterized in that, include: Based on the equipment-side frequency domain admittance model and network-side frequency domain admittance model Obtain the backlash matrix of the heterogeneous multi-feed system: Based on the return matrix Establish the closed-loop characteristic equation of the heterogeneous multi-feed system: Among them, symbols represent Each diagonal block is multiplied by .

6. The method for determining the stability of a new energy source-grid coordination driven by the passive index as described in claim 5, characterized in that, The generalized short-circuit ratio includes: Where gSCR is the generalized short-circuit ratio.

7. The method for determining the stability of a new energy source-grid coordination driven by the passive index as described in claim 6, characterized in that, include: Based on the generalized Nyquist criterion, the stability of heterogeneous multi-infeed systems is analyzed through the characteristic trajectory of the back-ratio matrix. Here, the original back-ratio matrix of the heterogeneous multi-infeed system is assumed to be... The characteristic trajectory is closest to the point (-1, 0) in the low-to-mid frequency band (1~100Hz), and far from the point (-1, 0) in other frequency bands. Furthermore, it does not intersect the negative real axis between the point (-1, 0) and infinity. Therefore, sufficient conditions for the small-disturbance stability of the power system in the new energy base can be obtained: ， in, For the frequency domain admittance model of the i-th converter port inward, IPI is the input passivity exponent.

8. The method for determining the stability of a new energy source-grid coordination driven by the passive index as described in claim 7, characterized in that, include: The distance between the lower limit of the generalized short-circuit ratio and the critical short-circuit ratio obtained through time-domain simulation can be minimized.

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