Method and device for calculating equipment critical short-circuit ratio of single grid-following type converter and storage medium

Abstract

The invention relates to the technical field of converters, and discloses an equipment critical short circuit ratio calculation method and device of a single grid-following converter and a storage medium. Time domain steady state analysis is carried out through equipment data of the grid-following converter to obtain a state-space equation of the grid-following converter; time-domain steady-state analysis is carried out through power grid parameters of the grid-following type converter to obtain a state-space equation based on the grid-following type converter, and a small signal model of the grid-following type converter single-machine grid-connected system is constructed by using the state-space equation and an impedance transfer function of an alternating current network side; according to the method, the analysis relation between the equipment critical short-circuit ratio and the following grid type converter is determined, and the equipment critical short-circuit ratio of the following grid type converter is determined through the small signal model, so that an empirical method is replaced, and the calculation efficiency and operability of the equipment critical short-circuit ratio are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of converters, and in particular to a method, a device and a storage medium for calculating the critical short-circuit ratio of a single grid-following converter. Background Art

[0002] At present, large-scale new energy is connected to the AC power grid through power electronic equipment. The current power system has shown a trend of changing from a power system dominated by traditional synchronous machines to a power system with a high proportion of power electronic equipment connected. Grid-following converters using phase-locked loop synchronization are widely used in scenarios where new energy is connected to the grid, which weakens the strength of the system. In the case of weak power grids, sub- / super-synchronous oscillation problems occur frequently, which brings challenges to the safe and stable operation of the grid-connected system of new energy through grid-following converters.

[0003] The short-circuit ratio indicator is generally used to measure the grid strength of the AC system. An AC grid with a short-circuit ratio less than 2 is considered a weak AC grid. The industry generally selects 1.5~2.0 as the critical short-circuit ratio of the equipment based on experience or determines the critical short-circuit ratio of the equipment through experimental methods. When the grid strength, that is, the short-circuit ratio of the equipment access point is greater than the critical short-circuit ratio of the intervening equipment, the grid-connected system of the grid-connected converter is considered to be stable.

[0004] However, since the empirical method is too conservative and even ineffective in some cases, the test method is inefficient and not very practical. Summary of the invention

[0005] In view of this, the present invention provides a method, device and storage medium for calculating the critical short-circuit ratio of equipment of a single grid-following converter, which solves the technical problems that the method based on experience is too conservative and even fails in some cases, the test method is inefficient and has poor operability.

[0006] A first aspect of the present invention provides a method for calculating the critical short-circuit ratio of a single grid-type converter, comprising:

[0007] According to the equipment data of the grid-following converter, a time-domain steady-state analysis is performed to obtain the state space equation based on the grid-following converter;

[0008] According to the grid parameters of the grid-following converter, the frequency domain steady-state analysis is carried out to obtain the impedance transfer function of the AC network side;

[0009] Constructing a small signal model of a single-machine grid-connected system of a grid-connected converter according to the state space equation based on the grid-connected converter and the impedance transfer function on the AC network side;

[0010] The equipment critical short-circuit ratio of the grid-following converter is determined according to the small signal model of the grid-following converter single-machine grid-connected system.

[0011] Preferably, the state space equation based on the grid-following converter is:

[0012]

[0013] In the formula, is a differential operator; is a micro increment; is the state variable, is the output variable of the phase-locked loop PI integral link, is the phase angle measured by the phase-locked loop, T is the matrix transpose sign; is the state matrix; is the control matrix; is the output matrix; , , They are the x-axis and y-axis components of the voltage of the grid-following converter respectively; , , They are the x-axis and y-axis components of the current of the grid-following converter respectively; is the phase-locked loop PI integral parameter; is the phase-locked loop PI proportional coefficient; The reactive power output by the grid-type converter at the steady-state equilibrium point; , They are the x-axis and y-axis components of the voltage of the grid-following converter at the steady-state equilibrium point; , They are respectively the x-axis and y-axis components of the current of the grid-following converter at the steady-state equilibrium point.

[0014] Preferably, the impedance transfer function on the AC network side is:

[0015]

[0016] In the formula, is the inductive reactance value of the grid-following converter connected to the AC grid; s is the Laplace operator; is the ratio of line resistance to inductance of the AC network, , R and L are the line resistance and inductance of the AC network respectively; is the industrial frequency angular velocity.

[0017] Preferably, the small signal model of the grid-connected system of the grid-following converter is:

[0018]

[0019] In the formula, is the state matrix of the system.

[0020] Preferably, the step of determining the critical short-circuit ratio of the grid-connected converter according to the small signal model of the grid-connected converter single-machine grid-connected system comprises:

[0021] Extracting the eigenvalue of the state matrix of the small signal model according to the small signal model of the grid-connected single-machine grid-connected system of the grid-following converter;

[0022] The real part of the complex form of the eigenvalue of the state matrix of the small signal model is set to zero to obtain the equipment critical short-circuit ratio of the grid-following converter.

[0023] Preferably, the eigenvalue of the state matrix of the small signal model is:

[0024]

[0025] In the formula, To find the real part of a complex number; is the eigenvalue of the state matrix of the small signal model; The active power output by the grid-type converter at the steady-state equilibrium point; The reactive power output by the grid-type converter at the steady-state equilibrium point; It is the voltage amplitude of the grid-connected point of the grid-connected converter at the steady-state equilibrium point.

[0026] In a second aspect, the present invention further provides a device for calculating the critical short-circuit ratio of a single grid-type converter, comprising:

[0027] A time domain analysis module is used to perform time domain steady-state analysis based on the equipment data of the grid-following converter to obtain a state space equation based on the grid-following converter;

[0028] The frequency domain analysis module is used to perform frequency domain steady-state analysis based on the grid parameters of the grid-following converter to obtain the impedance transfer function on the AC network side;

[0029] A model building module, used to build a small signal model of a single-machine grid-connected system of a grid-connected converter according to the state space equation based on the grid-connected converter and the impedance transfer function on the AC network side;

[0030] The short-circuit ratio calculation module is used to determine the critical short-circuit ratio of the grid-following converter according to the small signal model of the grid-following converter single-machine grid-connected system.

[0031] In a third aspect, the present invention further provides an electronic device, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the method for calculating the critical short-circuit ratio of a single grid-type converter as described in the first aspect.

[0032] In a fourth aspect, the present invention further provides a computer-readable storage medium having a computer program stored thereon, which, when executed, implements the steps of the method for calculating the critical short-circuit ratio of equipment of a single grid-type converter as described in the first aspect.

[0033] In a fifth aspect, the present invention further provides a computer program product, comprising a computer program stored on a non-transitory computer-readable storage medium, wherein the computer program comprises program instructions, wherein when the program instructions are executed by a computer, the computer executes the steps of the method for calculating the critical short-circuit ratio of a single grid-type converter as described in the first aspect.

[0034] It can be seen from the above technical scheme that the present invention performs time-domain steady-state analysis on the equipment data of the grid-following converter to obtain the state-space equation of the grid-following converter, and performs time-domain steady-state analysis on the power grid parameters of the grid-following converter to obtain the state-space equation based on the grid-following converter, and constructs a small signal model of the grid-connected system of the grid-following converter by using the state-space equation and the impedance transfer function on the AC network side, thereby determining the analytical relationship between the critical short-circuit ratio of the equipment and the grid-following converter, and determining the critical short-circuit ratio of the equipment of the grid-following converter by the small signal model, thereby replacing the empirical method, improving the calculation efficiency and operability of the critical short-circuit ratio of the equipment, and revealing the relationship between the phase-locked loop parameters of the grid-following converter and the critical short-circuit ratio of the equipment, thereby ensuring the stability of the power grid when facing large-scale renewable energy grid connection. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 An application environment diagram of a method for calculating the equipment critical short-circuit ratio of a single grid-type converter provided by an embodiment of the present invention;

[0036] Figure 2 A flow chart of a method for calculating the critical short-circuit ratio of a single grid-type converter provided in an embodiment of the present invention;

[0037] Figure 3 A topological diagram of a grid-connected system of a single-machine grid-connected converter provided in an embodiment of the present invention;

[0038] Figure 4 A waveform diagram showing the comparison between the actual values ​​of SCR and CSCR output by time domain simulation provided by an embodiment of the present invention;

[0039] Figure 5 A waveform diagram showing a comparison between the SCR and CSCR calculated values ​​output by a time domain simulation according to an embodiment of the present invention;

[0040] Figure 6 A waveform diagram showing a comparison of SCR and CSCR empirical values ​​output by time domain simulation according to an embodiment of the present invention;

[0041] Figure 7 A schematic diagram of the structure of a device for calculating the critical short-circuit ratio of a single grid-type converter provided by an embodiment of the present invention;

[0042] Figure 8 A schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0043] 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 are within the scope of protection of the present invention.

[0044] The method for calculating the critical short-circuit ratio of a single grid-type converter provided in the embodiment of the present application can be applied to Figure 1 In the application environment shown. The grid-following converter communicates with the server 102 via the network. The data storage system can store data that the server 102 needs to process. The data storage system can be integrated on the server 102, or placed on the cloud or other network servers. The server 102 can be an independent physical server, or a server cluster or distributed system composed of multiple physical servers, or a cloud server that provides cloud computing services.

[0045] like Figure 2 As shown, the embodiment of the present application provides a method for calculating the critical short-circuit ratio of a single grid-following converter. Figure 1 The server 102 in the example is used as an example to illustrate the method, which includes the following steps S1 to S4. Among them:

[0046] Step S1, performing a time domain steady-state analysis based on equipment data of the grid-following converter to obtain a state space equation based on the grid-following converter.

[0047] Among them, the equipment data of the grid-following converter refers to the operating data inside the grid-following converter body, including but not limited to the phase-locked loop PI proportional coefficient, the phase-locked loop PI integral parameter, the voltage x-axis and y-axis components during steady-state operation, and the current x-axis and y-axis components during steady-state operation. The new energy power grid in this application may contain a static var generator (SVG).

[0048] Among them, by performing time-domain steady-state analysis on the device data of the grid-following converter, Taylor series expansion is performed on the nonlinear state space equation, and the first-order term is retained to obtain the linearized state space equation, that is, the state space equation based on the grid-following converter is:

[0049]

[0050] In the formula, is a differential operator; is a micro increment; is the state variable, is the output variable of the phase-locked loop PI integral link, is the phase angle measured by the phase-locked loop, T is the matrix transpose sign; is the state matrix; is the control matrix; is the output matrix; , , They are the x-axis and y-axis components of the voltage of the grid-following converter respectively; , , They are the x-axis and y-axis components of the current of the grid-following converter respectively; is the phase-locked loop PI integral parameter; is the phase-locked loop PI proportional coefficient; The reactive power output by the grid-type converter at the steady-state equilibrium point; , They are the x-axis and y-axis components of the voltage of the grid-following converter at the steady-state equilibrium point; , They are respectively the x-axis and y-axis components of the current of the grid-following converter at the steady-state equilibrium point.

[0051] Step S2: Perform frequency domain steady-state analysis according to the grid parameters of the grid-following converter to obtain the impedance transfer function of the AC network side.

[0052] The grid parameters of the grid-following converter refer to the parameters of the AC network side corresponding to the grid-following converter, including but not limited to the AC grid line resistance-inductance ratio.

[0053] Among them, by performing frequency domain steady-state analysis on the grid parameters of the grid-following converter, the impedance transfer function on the AC network side is obtained as follows:

[0054]

[0055] In the formula, is the inductive reactance value of the grid-following converter connected to the AC grid; s is the Laplace operator; is the ratio of line resistance to inductance of the AC network, , R and L are the line resistance and inductance of the AC network respectively; is the industrial frequency angular velocity.

[0056] Step S3: construct a small signal model of a grid-connected system of a single-machine grid-connected converter according to a state space equation of the grid-connected converter and an impedance transfer function on the AC network side.

[0057] Among them, the impedance transfer function on the AC network side is substituted into the state space equation of the grid-connected converter, and further based on the relationship between the frequency domain and the time domain, and eliminating the Laplace operator, the small signal model of the grid-connected converter single-machine grid-connected system is obtained as follows:

[0058]

[0059] In the formula, is the state matrix of the system.

[0060] Step S4: determining the critical short-circuit ratio of the grid-following converter according to the small signal model of the grid-following converter single-machine grid-connected system.

[0061] It can be understood that the small signal model can characterize the small disturbance stability of the grid-following converter when it is connected to different power grids. Based on the time domain and frequency domain stability analysis theory, the equipment critical short-circuit ratio of the grid-following converter is derived, and the relationship between the equipment critical short-circuit ratio and the phase-locked loop parameters of the grid-following converter and different working conditions is explained.

[0062] Specifically, the process of determining the critical short-circuit ratio of the grid-connected converter according to the small signal model of the grid-connected converter single machine grid-connected system in step S4 includes:

[0063] Step S401: extracting eigenvalues ​​of a state matrix of a small signal model according to a small signal model of a single-machine grid-connected system of a grid-following converter.

[0064] Among them, the characteristic equation of the state matrix of the small signal model is:

[0065]

[0066] In the formula, det(·) is the determinant of the matrix to be obtained; is the eigenvalue of the state matrix of the small signal model.

[0067] The real part of the eigenvalue of the state matrix of the small signal model can characterize the stability of the system. According to the characteristic equation of the state matrix of the small signal model, the eigenvalue is:

[0068]

[0069] In the formula, To find the real part of a complex number; The active power output by the grid-type converter at the steady-state equilibrium point; The reactive power output by the grid-type converter at the steady-state equilibrium point; is the voltage amplitude of the grid-connected point of the grid-type converter when it is the steady-state equilibrium point. Among them, according to the knowledge of circuit principle, it can be obtained from , , , Calculated.

[0070] Step S402: The real part of the complex form of the eigenvalue of the state matrix of the small signal model is set to zero. At this time, the short-circuit ratio of the system is the critical short-circuit ratio of the equipment.

[0071] Among them, when the real part of the complex form of the eigenvalue of the state matrix of the small signal model is zero, it indicates that the power grid system where the grid-following converter is located is in a critical stable state. At this time, the short-circuit ratio on the AC network side, that is, the equipment critical short-circuit ratio of the grid-following converter is:

[0072]

[0073] In the formula, It is the critical short-circuit ratio of the grid-type converter.

[0074] It should be noted that the embodiment of the present application performs time-domain steady-state analysis on the equipment data of the grid-following converter to obtain the state-space equation of the grid-following converter, and performs time-domain steady-state analysis on the grid parameters of the grid-following converter to obtain the state-space equation based on the grid-following converter, and constructs a small signal model of the grid-connected system of the grid-following converter by using the state-space equation and the impedance transfer function on the AC network side, thereby determining the analytical relationship between the critical short-circuit ratio of the equipment and the grid-following converter, and determining the critical short-circuit ratio of the equipment of the grid-following converter through the small signal model, thereby replacing the empirical method, improving the calculation efficiency and operability of the critical short-circuit ratio of the equipment, and revealing the relationship between the phase-locked loop parameters of the grid-following converter and the critical short-circuit ratio of the equipment, thereby ensuring the stability of the power grid when facing large-scale renewable energy grid connection.

[0075] The following is a calculation example of a method for calculating the critical short-circuit ratio of a single grid-type converter provided in combination with an embodiment of the present application.

[0076] In this example, if Figure 3As shown, a grid-connected system of a single-machine grid-connected converter is built in matlab, wherein node 1 is connected to the grid-connected converter and node 2 is connected to the external AC power grid, which is simplified to an infinite bus. The capacity and detailed control parameters of the grid-connected converter are shown in Table 1. Table 2 shows the calculation method of the critical short-circuit ratio of the grid-connected converter equipment given in the embodiment of the present application under different steady-state operating points and phase-locked loop parameters, the calculation results of the critical short-circuit ratio of the equipment obtained from engineering experience, and the comparison between the actual critical short-circuit ratio of the equipment.

[0077] Table 1 Capacity and control parameters of grid-following converter

[0078]

[0079] Table 2 Comparison of critical short-circuit ratio of grid-type converter under different methods

[0080]

[0081] It can be seen from Table 2 that the calculated equipment critical short-circuit ratio is consistent with the actual equipment critical short-circuit ratio, and the error is within an acceptable range, which verifies the effectiveness of the proposed equipment critical short-circuit ratio calculation method for grid-following converters. Compared with the equipment critical short-circuit ratio obtained from traditional engineering experience, the accuracy of the present invention is greatly improved without the need for actual experiments.

[0082] In addition, a time domain simulation of a single-machine grid-connected system of new energy was conducted to verify the effectiveness of the proposed calculation method for the critical short-circuit ratio of the equipment of the grid-connected converter. When the phase-locked loop parameters are set at 15+9000s, the voltage amplitude is set at 1.0pu, the active power is set at 1.0pu, and the reactive power is set at 0.0pu, the AC grid short-circuit ratio is set at 1.7734, 1.8898, and 1.5, respectively, corresponding to the actual value of the critical short-circuit ratio of the equipment, the calculated value of this method, and the commonly used value in engineering experience. At t=1s, a disturbance is applied to the infinite bus, resulting in a 0.05pu voltage drop, which lasts for 0.05s.

[0083] Figures 4 to 6 The time domain response of all IBR (Intelligent Battery Reserve, the inverter's resource) active power output is given. Figures 4 to 6 It can be seen that when SCR=CSCR actual value, the system oscillates with equal amplitude and is in a critical stable state; when SCR=CSCR calculated value, the system oscillates and converges, but the convergence is very slow, almost equal amplitude oscillation, which shows the effectiveness of the proposed method; when SCR=CSCR empirical value, the system oscillates and diverges, and there is a large error in selecting the engineering empirical value as the critical short-circuit ratio of the equipment. The above time domain simulation results verify the effectiveness of the proposed calculation method.

[0084] In summary, the equipment critical short-circuit ratio calculation of a single grid-type converter proposed in the present application has achieved better results in terms of operability, accuracy and adaptability compared to traditional engineering experience methods.

[0085] Based on the same inventive concept, an embodiment of the present application also provides a device for calculating the critical short-circuit ratio of equipment of a single grid-type converter for implementing the above-mentioned method for calculating the critical short-circuit ratio of equipment of a single grid-type converter.

[0086] The implementation solution to the problem provided by the device is similar to the implementation solution recorded in the above method. Therefore, the specific limitations in the embodiment of the equipment critical short-circuit ratio calculation device for one or more single grid-type converters provided below can be referred to the limitations of the equipment critical short-circuit ratio calculation method for a single grid-type converter in the above text, and will not be repeated here.

[0087] like Figure 7 As shown, the embodiment of the present application proposes a device for calculating the critical short-circuit ratio of a single grid-type converter, comprising:

[0088] The time domain analysis module 100 is used to perform time domain steady-state analysis based on the equipment data of the grid-following converter to obtain a state space equation based on the grid-following converter.

[0089] Among them, the state space equation based on the grid-following converter is:

[0090]

[0091] In the formula, is a differential operator; is a micro increment; is the state variable, is the output variable of the phase-locked loop PI integral link, is the phase angle measured by the phase-locked loop, T is the matrix transpose sign; is the state matrix; is the control matrix; is the output matrix; , , They are the x-axis and y-axis components of the voltage of the grid-following converter respectively; , , They are the x-axis and y-axis components of the current of the grid-following converter respectively; is the phase-locked loop PI integral parameter; is the phase-locked loop PI proportional coefficient; The reactive power output by the grid-type converter at the steady-state equilibrium point; , They are the x-axis and y-axis components of the voltage of the grid-following converter at the steady-state equilibrium point; , They are respectively the x-axis and y-axis components of the current of the grid-following converter at the steady-state equilibrium point.

[0092] The frequency domain analysis module 200 is used to perform frequency domain steady-state analysis according to the grid parameters of the grid-following converter to obtain the impedance transfer function of the AC network side.

[0093] Among them, the impedance transfer function on the AC network side is:

[0094]

[0095] In the formula, is the inductive reactance value of the grid-following converter connected to the AC grid; s is the Laplace operator; is the ratio of line resistance to inductance of the AC network, , R and L are the line resistance and inductance of the AC network respectively; is the industrial frequency angular velocity.

[0096] The model building module 300 is used to build a small signal model of a grid-connected system of a single-machine grid-connected converter according to the state space equation of the grid-connected converter and the impedance transfer function of the AC network side.

[0097] Among them, the small signal model of the grid-connected system of a single-machine grid-connected converter is:

[0098]

[0099] In the formula, is the state matrix of the system.

[0100] The short-circuit ratio calculation module 400 is used to determine the critical short-circuit ratio of the grid-following converter according to the small signal model of the grid-following converter single machine grid-connected system.

[0101] In one example, the short-circuit ratio calculation module 400 is used to extract the eigenvalue of the state matrix of the small signal model based on the small signal model of the single-machine grid-connected system of the grid-following converter; the real part of the complex form of the eigenvalue of the state matrix of the small signal model is taken as zero to obtain the equipment critical short-circuit ratio of the grid-following converter.

[0102] Among them, the characteristic equation of the state matrix of the small signal model is:

[0103]

[0104] In the formula, det(·) is the determinant of the matrix to be obtained; is the eigenvalue of the state matrix of the small signal model.

[0105] The real part of the eigenvalue of the state matrix of the small signal model can characterize the stability of the system. According to the characteristic equation of the state matrix of the small signal model, the eigenvalue is:

[0106]

[0107] In the formula, To find the real part of a complex number; The active power output by the grid-type converter at the steady-state equilibrium point; The reactive power output by the grid-type converter at the steady-state equilibrium point; The voltage amplitude of the grid-connected point of the grid-type converter when it is the steady-state equilibrium point can be obtained based on the knowledge of circuit principles. , , , Calculated.

[0108] Among them, when the real part of the complex form of the eigenvalue of the state matrix of the small signal model is zero, it indicates that the power grid system where the grid-following converter is located is in a critical stable state. At this time, the short-circuit ratio on the AC network side is the equipment critical short-circuit ratio of the grid-following converter:

[0109]

[0110] In the formula, It is the critical short-circuit ratio of the grid-type converter.

[0111] like Figure 8 As shown, an embodiment of the present application also provides an electronic device, the electronic device 10 includes a memory 20 and a processor 30, the memory 20 stores a computer program, and when the computer program is executed by the processor 30, the processor 30 executes the steps of the method for calculating the critical short-circuit ratio of a single grid-type converter as in any of the above embodiments.

[0112] An embodiment of the present application also provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed, the steps of the method for calculating the critical short-circuit ratio of equipment of a single grid-type converter as in any of the above embodiments are implemented.

[0113] An embodiment of the present application also provides a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium, and the computer program includes program instructions. When the program instructions are executed by a computer, the computer executes the steps of the method for calculating the critical short-circuit ratio of a single grid-type converter as in any of the above embodiments.

[0114] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described systems, electronic devices, computer storage media and computer program products can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0115] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or apparatus.

[0116] In several embodiments provided by the present invention, it is understood that each box in the flow chart or block diagram can represent a module, a program segment or a part of a code, and a part of a module, a program segment or a code includes one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from that marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved.

[0117] In the several embodiments provided by the present invention, it should be understood that the disclosed systems, electronic devices, computer storage media, computer program products and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of units is only 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 devices or units, which can be electrical, mechanical or other forms.

[0118] 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 network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0119] 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.

[0120] 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 executing all or part of the steps of the various embodiments of the method of the present invention through a computer device (which can be a personal computer, a server, or a network device, etc.). The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (full name in English: Read-Only Memory, English abbreviation: ROM), random access memory (full name in English: Random Access Memory, English abbreviation: RAM), disk or optical disk, etc. Various media that can store program codes.

[0121] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating the critical short-circuit ratio of a single grid-type converter, characterized in that: include: According to the equipment data of the grid-following converter, a time-domain steady-state analysis is performed to obtain the state space equation based on the grid-following converter; According to the grid parameters of the grid-following converter, the frequency domain steady-state analysis is carried out to obtain the impedance transfer function of the AC network side; Constructing a small signal model of a single-machine grid-connected system of a grid-connected converter according to the state space equation based on the grid-connected converter and the impedance transfer function on the AC network side; The equipment critical short-circuit ratio of the grid-following converter is determined according to the small signal model of the grid-following converter single-machine grid-connected system.

2. The method for calculating the equipment critical short-circuit ratio of a single grid-type converter according to claim 1, characterized in that: The state space equation based on the grid-following converter is: In the formula, is a differential operator; is a micro increment; is the state variable, is the output variable of the phase-locked loop PI integral link, is the phase angle measured by the phase-locked loop, T is the matrix transpose sign; is the state matrix; is the control matrix; is the output matrix; , , They are the x-axis and y-axis components of the voltage of the grid-following converter respectively; , , They are the x-axis and y-axis components of the current of the grid-following converter respectively; is the phase-locked loop PI integral parameter; is the phase-locked loop PI proportional coefficient; The reactive power output by the grid-type converter at the steady-state equilibrium point; , They are the x-axis and y-axis components of the voltage of the grid-following converter at the steady-state equilibrium point; , They are respectively the x-axis and y-axis components of the current of the grid-following converter at the steady-state equilibrium point.

3. The method for calculating the equipment critical short-circuit ratio of a single grid-type converter according to claim 2, characterized in that: The impedance transfer function of the AC network side is: In the formula, The inductive reactance value of the grid-following converter connected to the AC grid; s is the Laplace operator; is the ratio of line resistance to inductance of the AC network, , R and L are the line resistance and inductance of the AC network respectively; is the industrial frequency angular velocity.

4. The method for calculating the equipment critical short-circuit ratio of a single grid-type converter according to claim 3, characterized in that: The small signal model of the grid-connected system of the grid-following converter is: In the formula, is the state matrix of the system.

5. The method for calculating the equipment critical short-circuit ratio of a single grid-type converter according to claim 4, characterized in that: The step of determining the critical short-circuit ratio of the grid-following converter according to the small signal model of the grid-following converter single-machine grid-connected system comprises: Extracting the eigenvalue of the state matrix of the small signal model according to the small signal model of the grid-connected single-machine grid-connected system of the grid-following converter; The real part of the complex form of the eigenvalue of the state matrix of the small signal model is set to zero to obtain the equipment critical short-circuit ratio of the grid-following converter.

6. The method for calculating the equipment critical short-circuit ratio of a single grid-connected converter according to claim 5, characterized in that: The eigenvalue of the state matrix of the small signal model is: In the formula, To find the real part of a complex number; is the eigenvalue of the state matrix of the small signal model; The active power output by the grid-type converter at the steady-state equilibrium point; The reactive power output by the grid-type converter at the steady-state equilibrium point; It is the voltage amplitude of the grid-connected point of the grid-connected converter at the steady-state equilibrium point.

7. A device for calculating the critical short-circuit ratio of a single grid-type converter, characterized in that: include: A time domain analysis module is used to perform time domain steady-state analysis based on the equipment data of the grid-following converter to obtain a state space equation based on the grid-following converter; The frequency domain analysis module is used to perform frequency domain steady-state analysis based on the grid parameters of the grid-following converter to obtain the impedance transfer function on the AC network side; A model building module, used to build a small signal model of a single-machine grid-connected system of a grid-connected converter according to the state space equation based on the grid-connected converter and the impedance transfer function on the AC network side; The short-circuit ratio calculation module is used to determine the critical short-circuit ratio of the grid-following converter according to the small signal model of the grid-following converter single-machine grid-connected system.

8. An electronic device, characterized in that: The electronic device includes a memory and a processor, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the processor executes the steps of the method for calculating the critical short-circuit ratio of a single grid-type converter as described in any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed, the steps of the method for calculating the equipment critical short-circuit ratio of a single grid-connected converter as described in any one of claims 1 to 6 are implemented.

10. A computer program product, characterized in that The computer program product includes a computer program stored on a non-transitory computer-readable storage medium, and the computer program includes program instructions, wherein when the program instructions are executed by a computer, the computer is caused to execute the steps of the method for calculating the equipment critical short-circuit ratio of a single grid-type converter as described in any one of claims 1 to 6.

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