Method and system for calculating short-circuit ratio of new energy multi-station of network construction type SVG (Static Var Generator)

Abstract

The invention, which relates to the new energy power transmission field, discloses a calculation method and system for a short-circuit ratio of a new energy multi-station of a network-building type SVG, comprising the step of obtaining a short-circuit ratio level of the new energy multi-station when the network-building type SVG is not input according to the installation point, the installation capacity, the line impedance and the like of each new energy station. Secondly, the maximum short-circuit current capable of being provided during the fault period is calculated according to the design capacity, the connection impedance, the boost variable capacity, the leakage reactance value and the designed maximum overload capacity of the network construction type SVG; and finally, calculating a multi-infeed short-circuit ratio improvement value of the new energy station after the access of the network construction type SVG. Compared with the prior art, the method can quickly evaluate the improvement effect of the multi-infeed short-circuit ratio of the new energy station after the application of the network construction type SVG.

Description

Technical Field

[0001] The present invention relates to the field of new energy power transmission, and in particular to a method and system for calculating short-circuit ratio of a grid-type SVG new energy multi-station. Background Art

[0002] With the large-scale development and utilization of new energy, the scale of grid connection of new energy stations has shown explosive growth. During the period of new energy development, a large number of traditional synchronous units had to be temporarily shut down, resulting in a sharp drop in the short-circuit capacity of the system. As a result, problems such as insufficient reactive voltage support appeared in new energy stations. In order to enhance the strength of the power grid and reduce various oscillation problems caused by the output of new energy, the calculation requirements of the short-circuit ratio of new energy multiple stations are clearly proposed in the power system safety and stability calculation specification, which mainly guarantees the ratio of the short-circuit capacity of the power grid at the new energy grid connection point / low-voltage side to the scale of new energy grid connection. When the short-circuit ratio of new energy multiple stations does not meet the threshold value requirements, such as less than 3, it is required to take certain measures to improve the strength of the power grid. Generally, the method of installing synchronous condensers at the grid connection point is adopted, but since synchronous condensers are rotating equipment, they need to be equipped with lubrication systems and cooling systems, and the operation and maintenance workload is large. Generally, it is necessary to arrange special personnel to operate and supervise the condensers. This has brought great investment and operation and maintenance pressure to the investors of new energy.

[0003] With the development of grid-building technology, grid-building technology is applied to SVG. After the control strategy, converter overcurrent capacity and DC side energy storage unit are modified, the control effect is almost the same as that of the phase-shifting converter, showing voltage source external characteristics during faults. At the same time, this type of equipment is a static component with extremely low operation and maintenance losses. Therefore, it can be better applied to occasions where the short-circuit ratio of multiple new energy stations is insufficient, thereby improving the strength of the power grid to new energy grid connection points and supporting more new energy access.

[0004] However, the grid-forming SVG is a new type of equipment, and it is difficult to estimate how it will improve the short-circuit ratio of multiple renewable energy stations after it is connected to the grid. Summary of the invention

[0005] In view of the above existing problems, the present invention proposes a calculation method for improving the short-circuit ratio of multiple stations of new energy by using a network-type SVG. The method is mainly applicable to the case where the short-circuit ratio of multiple stations of new energy is insufficient. Considering that the network-type SVG is installed at the new energy grid connection point to meet the requirements of the specification for the short-circuit ratio of multiple stations of new energy, the present invention considers the key parameters of the access of the network-type SVG and proposes a relatively simple and operable method, which can quickly calculate the improvement effect of the short-circuit ratio of multiple stations of new energy. This can meet the requirements of the grid connection of new energy, support more new energy access, and promote the consumption of new energy.

[0006] In order to solve the above technical problems, a calculation method for the short-circuit ratio of a grid-type SVG renewable energy multi-station is proposed, including:

[0007] The short-circuit ratio level of multiple new energy stations is calculated based on the installation points, installation capacity and line impedance of each new energy station when the grid-type SVG is not put into use; the maximum short-circuit current that can be provided during a fault is calculated based on the design capacity, connection impedance, step-up transformer capacity and leakage reactance value, and the designed maximum overload capacity of the grid-type SVG; the improvement value of the multi-feed short-circuit ratio of the new energy station after the grid-type SVG is connected is calculated and evaluated.

[0008] As a preferred solution of a method for calculating the short-circuit ratio of a grid-type SVG new energy multi-station described in the present invention, the grid-type SVG includes a device that adopts a grid-type control strategy and exhibits voltage source characteristics. The device injects a short-circuit current into the fault point and maintains the internal potential unchanged during the fault.

[0009] As a preferred solution of the method for calculating the short-circuit ratio of a network-type SVG new energy multi-station according to the present invention, wherein: the short-circuit ratio level of the new energy multi-station when not put into use includes, the short-circuit ratio level of the new energy multi-station is calculated according to the following formula MRSCR i :

[0010]

[0011] Among them, S aci is the short-circuit capacity of the busbar i at the grid connection point of the new energy station, P rei The output of the new energy station i, Z ij , Z ii are the mutual impedance and self-impedance at the grid connection point of the new energy station, and i and j are the indexes of different variables.

[0012] As a preferred solution of the method for calculating the short-circuit ratio of a grid-type SVG new energy multi-station described in the present invention, wherein: the maximum short-circuit current includes obtaining the design capacity S of the grid-type SVG G , connection impedance X L , boost transformer capacity S T , step-up transformer leakage reactance X T , the transformer ratio is 1:T n , the designed short-time maximum overload capacity K of the mesh-type SVG.

[0013] Calculate the total equivalent impedance X of the connection impedance and boost transformer leakage reactance Z :

[0014]

[0015] Compare the equivalent impedance with The size of When , it is considered that the short-circuit capacity S added by the grid-connected SVG to the grid connection point Δ for:

[0016]

[0017] when When , it is considered that the short-circuit capacity added by SVG to the grid connection point is:

[0018]

[0019] Among them, U is the voltage value.

[0020] As a preferred solution of the method for calculating the short-circuit ratio of multiple stations of a networked SVG new energy source described in the present invention, wherein: the multi-feed short-circuit ratio enhancement value includes obtaining the short-circuit ratio of the new energy source i station as MRSCR i .

[0021] The short-circuit ratio of the grid-type SVG to the new energy i station is:

[0022]

[0023] As a preferred solution of the method for calculating the short-circuit ratio of a grid-type SVG new energy multi-station described in the present invention, the evaluation includes, in combination with the calculation result of the short-circuit ratio, using the grid stability analysis module to evaluate the transient stability model and voltage stability model of the grid after SVG access, and the transient stability model is improved as follows:

[0024]

[0025] Where J represents the moment of inertia of the system, which affects the system's response to dynamic changes, ω represents the phase angle position change of the generator, D is the damping coefficient matrix, G represents the connection strength of the system, and Q electrical is the electrical power in the system, Q mechanical is the mechanical power in the system.

[0026] The transient stability model is improved as follows:

[0027]

[0028] h(t)=e -λt sin(δt)

[0029] Among them, U)t(is the voltage value of the system at time t, λ u is the voltage attenuation coefficient, I d (t) is the load current at time t, which represents the current input that varies with time. R is the resistance of the system, h(t) is the time-varying filter function, λ is the attenuation rate, and δ is the oscillation frequency.

[0030]

[0031] Among them, S evaluation is the comprehensive evaluation value, N is the number of samples considered in the evaluation process, f(k) is a specific filter function, k is the variable index, indicating the kth sample. t' is the total evaluation time, P observed (t is the actual power observed, R min is the minimum resistance value, R max is the maximum resistance value, P threshold (t) is the transient stability threshold.

[0032] When S evaluation ≥S threshold When S evaluation <S threshold The transient stability of the power grid is poor.

[0033] Set the voltage stability index U indicator The measured normal voltage value and the ideal voltage value U observed The deviation determines:

[0034] U indicator =|U nominal -U observed |

[0035] Set the dynamic monitoring threshold U threshold , and monitor the system voltage in real time. indicator ≥U threshold When U indicator <U threshold The voltage stability is good.

[0036] If the transient stability is good and the voltage stability is good, the overall stability of the power grid is good. If any of the indicators is poor, the energy storage system is dynamically adjusted through the intelligent control system, and energy storage devices or speed-regulating generators are introduced to improve the system's transient response capability.

[0037] As a preferred solution of a method for calculating the short-circuit ratio of a grid-type SVG new energy multi-station described in the present invention, the dynamic adjustment of the energy storage system includes using the energy storage system to provide additional short-circuit current when a power grid fault occurs. When the short-circuit current is ≤50kA, the short-circuit current provided by the energy storage system is started to be 20% of the energy storage capacity, and the additional current is released into the power grid to help improve the short-circuit ratio.

[0038] When the short-circuit current is 50kA<≤100kA, the short-circuit current provided by the startup energy storage system is 40% of the energy storage capacity, and the additional current continues to be released to improve the short-circuit ratio.

[0039] When 100kA<short-circuit current≤150kA, the short-circuit current provided by the startup energy storage system is 60% of the energy storage capacity.

[0040] When the short-circuit current is >150kA, the short-circuit current provided by the startup energy storage system is 80% of the energy storage capacity.

[0041] Another object of the present invention is to provide a calculation system for the short-circuit ratio of multiple SVG new energy stations in a networked manner. The present invention ensures that the new energy stations can meet the requirements of grid stability when connected to the grid. Through the optimized configuration and intelligent control of SVG, the short-circuit ratio of the new energy stations is improved, and the transient and voltage stability of the grid is enhanced, thereby ensuring the reliable operation of the grid and the effective use of new energy.

[0042] As a preferred solution of the calculation system of the short-circuit ratio of a networked SVG new energy multi-station described in the present invention, it is characterized by including a data acquisition module, an SVG analysis module, and an evaluation module.

[0043] The data acquisition module collects the installation point, installation capacity, and line impedance parameters of each new energy station, and calculates the short-circuit ratio level of multiple new energy stations when SVG is not put into use.

[0044] The SVG analysis module collects the design capacity, connection impedance, step-up transformer capacity and leakage reactance value, and designed maximum overload capacity parameters of the grid-forming SVG, calculates the maximum short-circuit current that the SVG can provide during a fault, and determines the short-circuit capacity that the SVG adds to the grid connection point based on the impedance comparison result.

[0045] The evaluation module calculates the improvement value of the short-circuit ratio of multiple infeeds of the new energy station after SVG is connected, uses the improved transient stability model and the voltage stability model to perform the evaluation, and dynamically adjusts the energy storage system through the intelligent control system according to the stability evaluation result to improve the short-circuit ratio.

[0046] A computer device includes a memory and a processor, wherein the memory stores a computer program, and is characterized in that when the processor executes the computer program, the steps of the method for calculating the short-circuit ratio of a grid-type SVG new energy multi-station are implemented.

[0047] A computer-readable storage medium having a computer program stored thereon, characterized in that when the computer program is executed by a processor, the steps of a method for calculating the short-circuit ratio of a grid-type SVG new energy multi-station are implemented.

[0048] Beneficial effects of the present invention: The present invention can quickly derive an improved value of the short-circuit ratio of the new energy multi-station of the grid connection point based on the basic parameters of the selected network SVG.

[0049] The present invention can also be based on the problem of insufficient short-circuit ratio of existing new energy multiple stations, in order to meet the short-circuit ratio of new energy multiple stations to meet the grid connection requirements, thereby calculating the capacity and key parameters of the network SVG that needs to be connected at the grid connection point. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. 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 work, among which:

[0051] Figure 1 An overall flow chart of a method for calculating the short-circuit ratio of a grid-type SVG new energy multi-station is provided as an embodiment of the present invention.

[0052] Figure 2 A method for calculating the short-circuit ratio of a meshed SVG new energy multi-station is provided in accordance with an embodiment of the present invention, and a network topology diagram of a meshed SVG accessed with wind and solar new energy stations is provided.

[0053] Figure 3 A schematic diagram of the structure of a computer device of a network-type SVG new energy multi-station short-circuit ratio calculation system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0054] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0055] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0056] 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 term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it an embodiment that is mutually exclusive with other embodiments, either individually or selectively.

[0057] The present invention is described in detail with reference to schematic diagrams. When describing the embodiments of the present invention, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0058] At the same time, in the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper, lower, inner and outer" are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first, second or third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0059] In the present invention, unless otherwise clearly specified and limited, the terms "install, connect, connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection or an integral connection; it can also be a mechanical connection, an electrical connection or a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0060] Example 1, reference Figure 1-Figure 2 , which is the first embodiment of the present invention, and provides a method for calculating the short-circuit ratio of a multi-station network-type SVG new energy source, comprising:

[0061] S1: Calculate the short-circuit ratio of multiple renewable energy stations when the network-type SVG is not put into use based on the installation points, installation capacity and line impedance of each renewable energy station.

[0062] Furthermore, a meshed SVG refers to a device that adopts a meshed control strategy and exhibits voltage source characteristics. The device injects a short-circuit current into the fault point and maintains the internal potential unchanged during the fault.

[0063] It should be noted that the short-circuit ratio level of new energy multi-station is calculated according to the following formula MRSCR i :

[0064]

[0065] Among them, S aci is the short-circuit capacity of the busbar i at the grid connection point of the new energy station, P rei The output of the new energy station i, Z ij , Z ii are the mutual impedance and self-impedance at the grid connection point of the new energy station, and i and j are the indexes of different variables.

[0066] S2: Calculate the maximum short-circuit current that can be provided during a fault according to the design capacity, connection impedance, step-up transformer capacity and leakage reactance value of the grid-type SVG and the designed maximum overload capacity.

[0067] Furthermore, the design capacity S of the mesh SVG is obtained. G , connection impedance X L , boost transformer capacity S T , step-up transformer leakage reactance X T , the transformer ratio is 1:T n , the designed short-time maximum overload capacity K of the mesh-type SVG.

[0068] Calculate the total equivalent impedance X of the connection impedance and boost transformer leakage reactance Z :

[0069]

[0070] Compare the equivalent impedance with The size of When , it is considered that the short-circuit capacity S added by the grid-connected SVG to the grid connection point Δ for:

[0071]

[0072] when When , it is considered that the short-circuit capacity added by SVG to the grid connection point is:

[0073]

[0074] Among them, U is the voltage value.

[0075] S3: Calculate the improvement in the multi-feed short-circuit ratio of the new energy station after the grid-type SVG is connected, and conduct an evaluation.

[0076] It should be noted that the short-circuit ratio of the new energy station i is MRSCR i .

[0077] The short-circuit ratio of the grid-type SVG to the new energy i station is:

[0078]

[0079] Furthermore, combined with the calculation results of the short-circuit ratio, the grid stability analysis module is used to evaluate the transient stability model and voltage stability model of the grid after SVG access. The transient stability model is improved as follows:

[0080]

[0081] Where J represents the moment of inertia of the system, which affects the system's response to dynamic changes, ω represents the phase angle position change of the generator, D is the damping coefficient matrix, G represents the connection strength of the system, and Q electrical is the electrical power in the system, Q mechanical is the mechanical power in the system;

[0082] The transient stability model is improved as follows:

[0083]

[0084] h(t)=e -λt sin(δt)

[0085] Among them, U(t) is the voltage value of the system at time t, λ u is the voltage attenuation coefficient, I d (t) is the load current at time t, indicating the current input that varies with time; R is the resistance of the system, h(t) is the time-varying filter function, λ is the attenuation rate, and δ is the oscillation frequency;

[0086] Using dynamic transient threshold:

[0087]

[0088] Among them, P threshold (t) is the transient stability threshold, is the maximum power value allowed by the system, Dynamic adjustment function, γ is the adjustment parameter for dynamic and fast sensitivity adjustment, τ is the time delay, which determines the response delay of power change;

[0089] Dynamic Voltage Threshold:

[0090] U threshold =U nominal ·(1+ε·cos(δ′t))

[0091] Among them, U threshold Voltage stability threshold, U nominal is the normal working voltage, ε is the standardized allowable voltage fluctuation range, and δ' is the voltage oscillation frequency;

[0092]

[0093] Among them, S evaluation is the comprehensive evaluation value, N is the number of samples considered in the evaluation process, f(k) is a specific filter function, k is the variable index, indicating the kth sample; t' is the total evaluation time, P observed (t is the actual power observed, R min is the minimum resistance value, R max is the maximum resistance value;

[0094] When S evaluation ≥S threshold When S evaluation <S threshold When , the transient stability of the power grid is poor;

[0095] Set the voltage stability index U indicator The measured normal voltage value and the ideal voltage value U observed The deviation determines:

[0096] U indicator =|U nominal -U observed |

[0097] Set the dynamic monitoring threshold U threshold , and monitor the system voltage in real time. indicator ≥U threshold When U indicator <U threshold When the voltage is stable,

[0098] If the transient stability is good and the voltage stability is good, the overall stability of the power grid is good. If any indicator is poor, the load is dynamically adjusted through the intelligent control system, and energy storage devices or speed-regulating generators are introduced to improve the system's transient response capability.

[0099] The dynamic adjustment of the energy storage system is to use the energy storage system to provide additional short-circuit current when the power grid fails. When the short-circuit current is ≤50kA, the short-circuit current provided by the energy storage system is started to be 20% of the energy storage capacity, and the additional current is released into the power grid to help improve the short-circuit ratio.

[0100] When the short-circuit current is 50kA<≤100kA, the short-circuit current provided by the startup energy storage system is 40% of the energy storage capacity, and the additional current continues to be released to improve the short-circuit ratio.

[0101] When 100kA<short-circuit current≤150kA, the short-circuit current provided by the startup energy storage system is 60% of the energy storage capacity.

[0102] When the short-circuit current is >150kA, the short-circuit current provided by the startup energy storage system is 80% of the energy storage capacity.

[0103] 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 the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

[0104] Example 2, reference Figure 1-2 , which is the second embodiment of the present invention, provides a method for calculating the short-circuit ratio of a grid-type SVG new energy multi-station. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through experiments.

[0105] like Figure 1 As shown in the figure, it is a network topology diagram of the grid-type SVG access to the grid-connected point containing the wind and solar new energy collection station. It is assumed that the new energy capacity of the photovoltaic station connected to the area is 120MVA; the capacity of the connected wind farm is 110MVA; the short-circuit capacity of the AC system to the new energy collection station is 210MVA; according to the steps of the present invention, it can be calculated that the multi-station short-circuit ratio of the photovoltaic power station MRSCR=1.75; the multi-station short-circuit ratio of the wind farm MRSCR=1.91; according to the national standard GB / T40581-2021, the multi-station short-circuit ratio of the new energy grid-connected point should be not less than 2.0, preferably greater than 3.0; in order to improve the short-circuit ratio of the new energy multi-station, a grid-type SVG device is added on the low-voltage side of the new energy collection station, the capacity of the device is 50Mvar, and the connection impedance is XL=0.1; the capacity of the step-up transformer is 60MVA, and the transformer leakage reactance is 14%. The transformer ratio is 35 / 220 kV; the short-circuit overload capacity of the grid-forming SVG design is K=4; according to the calculation method proposed by the present invention, the equivalent impedance of the grid-forming SVG relative to the grid connection point is first calculated:

[0106]

[0107] because The capacity provided by this network-type SVG to the grid connection point is:

[0108]

[0109] From this, it can be calculated that the grid-type SVG increases the short-circuit ratio of multiple photovoltaic power stations by 1.75×140 / 210=1.167.

[0110] The short-circuit ratio of multiple wind farm stations increased by 1.91×140 / 210=1.273.

[0111] By using this calculation method, the improvement value of the multi-feed short-circuit ratio of the new energy collection station by the grid-type SVG can be quickly evaluated.

[0112] 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 the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

[0113] Embodiment 3, the third embodiment of the present invention, is different from the first two embodiments in that:

[0114] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several 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 methods described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, and other media that can store program codes.

[0115] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0116] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0117] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0118] Example 4, reference Figure 3 , which is the fourth embodiment of the present invention, provides a calculation system for the short-circuit ratio of a networked SVG new energy multi-station, including a data acquisition module, an SVG analysis module, and an evaluation module.

[0119] The data acquisition module collects the installation points, installation capacity, and line impedance parameters of each new energy station, and calculates the short-circuit ratio level of multiple new energy stations when SVG is not put into use.

[0120] The SVG analysis module collects the design capacity, connection impedance, step-up transformer capacity and leakage reactance value of the grid-forming SVG, and the designed maximum overload capacity parameters to calculate the maximum short-circuit current that the SVG can provide during a fault. Based on the impedance comparison results, the short-circuit capacity that the SVG adds to the grid connection point is determined.

[0121] The evaluation module calculates the improvement value of the short-circuit ratio of multiple infeeds in the new energy station after SVG access, and uses the improved transient stability model and voltage stability model for evaluation. According to the stability evaluation results, the energy storage system is dynamically adjusted through the intelligent control system to improve the short-circuit ratio.

[0122] 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 the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for calculating the short-circuit ratio of a multi-station network-based SVG renewable energy system, characterized in that: include, Calculate the short-circuit ratio of multiple renewable energy stations when the grid-type SVG is not put into use based on the installation points, installation capacity and line impedance of each renewable energy station; Calculate the maximum short-circuit current that can be provided during a fault according to the designed capacity, connection impedance, step-up transformer capacity and leakage reactance value of the grid-type SVG and the designed maximum overload capacity; Calculate and evaluate the improvement in the multi-infeed short-circuit ratio of the new energy station after the grid-type SVG is connected.

2. A method for calculating the short-circuit ratio of a networked SVG new energy multi-station as claimed in claim 1, characterized in that: The grid-type SVG includes a device that adopts a grid-type control strategy and exhibits voltage source characteristics. The device injects a short-circuit current into the fault point and maintains the internal potential unchanged during the fault period.

3. A method for calculating the short-circuit ratio of a networked SVG new energy multi-station as claimed in claim 2, characterized in that: The short-circuit ratio level of multiple renewable energy stations when not put into use includes: The short-circuit ratio level of multiple renewable energy stations is calculated according to the following formula: MRSCR i : Among them, S aci is the short-circuit capacity of the busbar i at the grid connection point of the new energy station, P rei The output of the new energy station i, Z ij , Z ii are the mutual impedance and self-impedance at the grid connection point of the new energy station, and i and j are the indexes of different variables.

4. A method for calculating the short-circuit ratio of a networked SVG new energy multi-station as claimed in claim 3, characterized in that: The maximum short-circuit current includes obtaining the design capacity S of the grid-type SVG. G , connection impedance X L , boost transformer capacity S T , step-up transformer leakage reactance X T , the transformer ratio is 1:T n , the short-term maximum overload capacity K of the designed grid-type SVG; Calculate the total equivalent impedance X of the connection impedance and boost transformer leakage reactance Z : Compare the equivalent impedance with The size of When , it is considered that the short-circuit capacity S added by the grid-connected SVG to the grid connection point Δ for: when When , it is considered that the short-circuit capacity added by SVG to the grid connection point is: Among them, U is the voltage value.

5. A method for calculating the short-circuit ratio of a networked SVG new energy multi-station as claimed in claim 4, characterized in that: The multi-feed short-circuit ratio improvement value includes obtaining the short-circuit ratio of the new energy station i as MRSCR i ; The short-circuit ratio of the grid-type SVG to the new energy i station is:

6. A method for calculating the short-circuit ratio of a networked SVG new energy multi-station as claimed in claim 5, characterized in that: The evaluation includes, in combination with the calculation result of the short-circuit ratio, using the grid stability analysis module to evaluate the transient stability model and voltage stability model of the grid after the SVG is connected, and the transient stability model is improved as follows: Where J represents the moment of inertia of the system, which affects the system's response to dynamic changes, ω represents the phase angle position change of the generator, D is the damping coefficient matrix, G represents the connection strength of the system, and Q electrical is the electrical power in the system, Q mechanical is the mechanical power in the system; The transient stability model is improved as follows: h(t)=e -λt sin(δt) Among them, U(t) is the voltage value of the system at time t, λ u is the voltage attenuation coefficient, I d (t) is the load current at time t, indicating the current input that varies with time; R is the resistance of the system, h(t) is the time-varying filter function, λ is the attenuation rate, and δ is the oscillation frequency; Among them, S evaluation is the comprehensive evaluation value, N is the number of samples considered in the evaluation process, f(k) is a specific filter function, k is the variable index, indicating the kth sample; t' is the total evaluation time, P observed (t) is the actual power observed, R min is the minimum resistance value, R max is the maximum resistance value, P threshold (t) is the transient stability threshold; When S evaluation ≥S threshold When S evaluation <S threshold When , the transient stability of the power grid is poor; Set the voltage stability index U indicator The measured normal voltage value and the ideal voltage value U observed The deviation determines: IN indicator =|U nominal -IN observed | Set the dynamic monitoring threshold U threshold , and monitor the system voltage in real time. indicator ≥U threshold When U indicator <U threshold When the voltage is stable, If the transient stability is good and the voltage stability is good, the overall stability of the power grid is good. If any of the indicators is poor, the energy storage system is dynamically adjusted through the intelligent control system, and energy storage devices or speed-regulating generators are introduced to improve the system's transient response capability.

7. A method for calculating the short-circuit ratio of a networked SVG new energy multi-station as claimed in claim 6, characterized in that: The dynamic regulation of the energy storage system includes using the energy storage system to provide additional short-circuit current when the power grid fails. When the short-circuit current is ≤50kA, the short-circuit current provided by the energy storage system is started to be 20% of the energy storage capacity, and the additional current is released to the power grid to help improve the short-circuit ratio; When the short-circuit current is 50kA<≤100kA, the short-circuit current provided by the energy storage system is started to be 40% of the energy storage capacity, and the additional current continues to be released to improve the short-circuit ratio; When 100kA<short-circuit current≤150kA, the short-circuit current provided by the startup energy storage system is 60% of the energy storage capacity; When the short-circuit current is >150kA, the short-circuit current provided by the startup energy storage system is 80% of the energy storage capacity.

8. A system using a method for calculating short-circuit ratio of a networked SVG new energy multi-station as claimed in any one of claims 1 to 7, characterized in that: Includes data acquisition module, SVG analysis module, and evaluation module; The data acquisition module collects the installation point, installation capacity, and line impedance parameters of each new energy station, and calculates the short-circuit ratio level of multiple new energy stations when SVG is not put into use; The SVG analysis module collects the design capacity, connection impedance, step-up transformer capacity and leakage reactance value, and designed maximum overload capacity parameters of the grid-forming SVG, calculates the maximum short-circuit current that the SVG can provide during a fault, and determines the short-circuit capacity that the SVG adds to the grid connection point based on the impedance comparison result; The evaluation module calculates the improvement value of the short-circuit ratio of multiple infeeds of the new energy station after SVG is connected, uses the improved transient stability model and the voltage stability model to perform the evaluation, and dynamically adjusts the energy storage system through the intelligent control system according to the stability evaluation result to improve the short-circuit ratio.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of a method for calculating the short-circuit ratio of a grid-type SVG new energy multi-station are implemented as described in any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of a method for calculating the short-circuit ratio of a grid-type SVG new energy multi-station are implemented as described in any one of claims 1 to 7.

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