A method and system for evaluating the voltage support ability of a new energy power source

Abstract

The present invention discloses a method and system for evaluating the voltage support ability of a new energy power source. The method includes: determining a system steady-state equation for solving the voltage at the new energy grid connection point in the steady state; determining a reactive current adjustment coefficient under system fault conditions, and based on the reactive current adjustment coefficient and the system steady-state equation, solving the unstable voltage at the new energy grid connection point under system fault conditions; comparing the unstable voltage at the new energy grid connection point with a preset stable critical voltage value, and evaluating the voltage support ability of the new energy power source according to the comparison result.

Description

Technical Field

[0001] The present invention relates to the technical field of power system simulation and analysis, and more specifically, to a method and system for evaluating the voltage support capability of new energy power sources. Background Art

[0002] Traditional power system transient simulation has achieved great success in the simulation and analysis of power systems. The numerical solutions obtained in power flow calculations can accurately reflect the operating state of the power system and the transient process after a fault. At the same time, mathematical tools such as continuous power flow and static security analysis developed based on transient simulation and other technical tools have greatly improved the ability and analysis level of power system safe and stable operation.

[0003] Voltage stability and reactive power support capability play an important role in the safe and stable operation of the power grid. However, with the large-scale access of new energy power sources, the use of traditional methods to analyze the voltage stability and reactive power support capability of the power grid may be inapplicable. According to the current widespread consensus in the academic community, various new energy power sources can be equivalent to current sources. Since they do not have the voltage support characteristics of voltage sources such as synchronous generators, voltage sources are required to provide voltage support when new energy power sources are connected to the grid. When the external voltage support capability is weak, the stable operation ability of new energy power sources will be affected. When the voltage support capability is seriously insufficient, voltage instability and collapse phenomena may occur in new energy power sources.

[0004] Although the wide access of new energy power sources makes the calculation of power system voltage stability and voltage support capability more complex, considering that during the voltage drop process caused by a large disturbance in the AC power grid, both traditional power sources and new energy power sources will provide a certain amount of voltage support according to their respective control methods to maintain system voltage stability. The currently widely used analysis methods can be divided into simulation methods and short-circuit ratio analysis methods.

[0005] Using the simulation method to analyze the system voltage support capability is mainly based on the content of Sections 5.2 and 5.3 of the current industry standard "DL / T1172-2013 Guide for Evaluation of Power System Voltage Stability" to determine whether "the load bus voltage can recover to more than 0.80 p.u. within 10 s after the power system is disturbed" and "during the medium- and long-term process after the power system is disturbed, the load bus voltage can be maintained or restored to more than 0.90 p.u." to evaluate the system voltage support capability. This method obtains the evaluation basis of voltage support capability based on time-domain simulation through the dynamic characteristics of the system. However, the simulation method focuses on the dynamic characteristics after the disturbance or fault clearance, and the obtained results are relatively conservative, and can be further optimized in practical engineering applications.

[0006] Using the short-circuit ratio analysis method to evaluate the voltage support ability is a relatively common analysis method currently considering the access of new energy power sources. This method focuses on simplifying and equivalenting the power system, and measures the voltage support ability of the power system after the access of new energy power sources by calculating the short-circuit current and the short-circuit ratio. This method is a static index and it is difficult to consider the voltage support role played by new energy power sources in the dynamic process after the system is disturbed. Therefore, there is a certain deviation in the accuracy of the short-circuit ratio analysis method.

[0007] Currently, the external characteristics of new energy power sources are generally controlled current sources and need the external power system to provide grid-connected voltage support to work properly. Therefore, when the grid-connected voltage support of the system is weak, it is very likely to cause the grid-connected operation of new energy power sources to be unstable, resulting in phenomena such as broadband oscillations. When the voltage support ability of the system is further weakened, more serious voltage instability and voltage collapse phenomena will occur in the new energy grid-connected system. Compared with the voltage stability phenomenon of the new energy grid-connected system, the broadband oscillation phenomenon usually has a leading nature. Therefore, whether broadband oscillations occur after a large disturbance can be used as an important idea to measure whether the voltage support ability of the external power system for new energy power sources is sufficient.

[0008] Although the wide access of new energy power sources makes the calculation of voltage stability and voltage support ability of the power system more complex, considering that during the voltage drop process caused by a large disturbance in the AC power grid, both traditional power sources and new energy power sources will provide a certain amount of reactive power support according to their respective control methods to maintain the system voltage level. On this basis, relevant analysis calculation and simulation tools can be used to judge whether broadband oscillations will occur in the new energy power sources connected to the system by analyzing the voltage drop depth during the large disturbance, and then to test the strength of the system voltage support under this condition.

[0009] Therefore, a technology is needed to evaluate the voltage support ability of new energy power sources. Summary of the Invention

[0010] The technical solution of the present invention provides a method and system for evaluating the voltage support ability of new energy power sources to solve the problem of how to evaluate the voltage support ability of new energy power sources.

[0011] To solve the above problems, the present invention provides a method for evaluating the voltage support ability of new energy power sources, and the method includes:

[0012] Determine the system steady-state equation when solving the voltage at the new energy grid connection point in the steady state;

[0013] Determine the reactive current adjustment coefficient under system fault conditions, and based on the reactive current adjustment coefficient and the system steady-state equation, solve the unstable voltage at the new energy grid connection point under system fault conditions

[0014] Compare the unstable voltage at the new energy grid connection point with a preset stable critical voltage value, and evaluate the voltage support ability of the new energy power source according to the comparison result.

[0015] Preferably, the system steady-state equation for determining the voltage at the new energy grid connection point during steady-state solution includes:

[0016]

[0017] where, is the equivalent power supply voltage on the grid side, is the active current component of the new energy power source, is the reactive current component of the new energy power source, Z eq is the grounding connection impedance at the fault point, Z1 is the connection impedance between the grid side and the fault point, and Z2 is the connection impedance between the new energy and the fault point.

[0018] Preferably, determining the reactive current adjustment coefficient under system fault conditions includes:

[0019]

[0020] where k is the reactive current adjustment coefficient and j is the imaginary unit.

[0021] Preferably, the value of k is not greater than 3.

[0022] Preferably, based on the reactive current adjustment coefficient and the system steady-state equation, solve the unstable voltage at the new energy grid connection point under system fault conditions including:

[0023]

[0024] Preferably, compare the unstable voltage at the new energy grid connection point with a preset stable critical voltage value, and evaluate the voltage support ability of the new energy power source according to the comparison result, including:

[0025] When the unstable voltage at the new energy grid connection point is greater than the stable critical voltage value, then there is no risk of broadband oscillation for the new energy power source;

[0026] When the unstable voltage at the new energy grid connection point is less than the stable critical voltage value, then there is no risk of broadband oscillation for the new energy power source.

[0027] Based on another aspect of the present invention, the present invention provides a system for evaluating the voltage support ability of a new energy power source, and the system includes:

[0028] A solving unit, configured to determine a system steady-state equation for solving the voltage at the new energy grid connection point in the steady state; determine a reactive current adjustment coefficient under system fault conditions, and solve the unstable voltage at the new energy grid connection point under system fault conditions based on the reactive current adjustment coefficient and the system steady-state equation

[0029] An evaluation unit, configured to use the unstable voltage at the new energy grid connection point Compare with a preset stable critical voltage value, and evaluate the voltage support ability of the new energy power supply according to the comparison result.

[0030] Preferably, the solving unit is configured to determine a system steady-state equation for solving the voltage at the new energy grid connection point in the steady state, and specifically configured to:[[]]

[0031]

[0032] Wherein, is the equivalent power supply voltage on the grid side, is the active current component of the new energy power supply, is the reactive current component of the new energy power supply, Z eq is the grounding connection impedance at the fault point, Z1 is the connection impedance between the grid side and the fault point, and Z2 is the connection impedance between the new energy and the fault point.

[0033] Preferably, the solving unit is configured to determine a reactive current adjustment coefficient under system fault conditions, and specifically configured to:[[]]

[0034]

[0035] Wherein, k is the reactive current adjustment coefficient, and j is the imaginary unit.

[0036] Preferably, the value of k is not greater than 3.

[0037] Preferably, the solving unit is configured to solve the unstable voltage at the new energy grid connection point under system fault conditions based on the reactive current adjustment coefficient and the system steady-state equation Specifically configured to:[[]]

[0038]

[0039] Preferably, the evaluation unit is configured to use the unstable voltage at the new energy grid connection point Compare with a preset stable critical voltage value, and evaluate the voltage support ability of the new energy power supply according to the comparison result, and specifically configured to:[[]]

[0040] When the unstable voltage at the new energy grid connection point is greater than the stable critical voltage value, then there is no risk of broadband oscillation for the new energy power supply;

[0041] When the unstable voltage at the new energy grid connection point is less than the stable critical voltage, there is no risk of broadband oscillation in the new energy power source.

[0042] The technical solution of the present invention provides a method and system for evaluating the voltage support ability of a new energy power source. The method includes: determining the system steady-state equation for solving the voltage at the new energy grid connection point in the steady state; determining the reactive current adjustment coefficient under system fault conditions, and based on the reactive current adjustment coefficient and the system steady-state equation, solving the unstable voltage at the new energy grid connection point under system fault conditions Compare the unstable voltage at the new energy grid connection point with a preset stable critical voltage, and evaluate the voltage support ability of the new energy power source according to the comparison result. The technical solution of the present invention can quickly judge the voltage stability and voltage support ability of the new energy power source under short-circuit disturbances considering the grid structure, the magnitude of short-circuit disturbances and the self-control coefficient of the new energy, avoiding full-network fault scanning and transient simulation calculations, and reducing the workload. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] By referring to the following drawings, the exemplary embodiments of the present invention can be more fully understood:

[0044] Figure 1 It is a flowchart of a method for evaluating the voltage support ability of a new energy power source according to a preferred embodiment of the present invention;

[0045] Figure 2 It is a schematic diagram of the typical system wiring according to a preferred embodiment of the present invention;

[0046] Figure 3 It is a schematic diagram of the voltage change at the new energy grid connection point when k = 0.8 according to a preferred embodiment of the present invention;

[0047] Figure 4 It is a schematic diagram of the voltage change at the new energy grid connection point when k = 1.5 according to a preferred embodiment of the present invention;

[0048] Figure 5 It is a system structure diagram of a method for evaluating the voltage support ability of a new energy power source according to a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0049] Reference is now made to the accompanying drawings to describe exemplary embodiments of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely, and to fully convey the scope of the present invention to those skilled in the art. The terms in the exemplary embodiments shown in the drawings are not intended to limit the present invention. In the drawings, the same units / components are denoted by the same reference numerals.

[0050] Unless otherwise specified, the terms used herein (including scientific and technical terms) have the ordinary meaning understood by those skilled in the art. In addition, it can be understood that the terms defined in the commonly used dictionary should be understood to have a meaning consistent with the context of their related fields, and should not be understood as idealized or overly formal meanings.

[0051] Figure 1 It is a flowchart of a method for evaluating the voltage support ability of a new energy power source according to a preferred embodiment of the present invention. The voltage sag index is a comprehensive evaluation index. Using the voltage sag index to evaluate the voltage support ability of a new energy power source can simultaneously consider the system strength and the control characteristics and parameters of the new energy power source itself, comprehensively reflect the influence of various factors, and has good applicability and comprehensive reflection ability. The voltage stability and voltage support ability calculated by the method proposed by the present invention have sufficient accuracy and can adapt to various operating modes of the power system.

[0052] As Figure 1 shown, the present invention provides a method for evaluating the voltage support ability of a new energy power source, and the method includes:

[0053] Step 101: Determine the system steady-state equation for solving the voltage at the new energy grid connection point in the steady state;

[0054] Preferably, determining the system steady-state equation for solving the voltage at the new energy grid connection point in the steady state includes:

[0055]

[0056] wherein, is the equivalent power supply voltage on the grid side, is the active current component of the new energy power source, is the reactive current component of the new energy power source, Z eq is the grounding connection impedance of the fault point, Z1 is the connection impedance between the grid side and the fault point, and Z2 is the connection impedance between the new energy and the fault point.

[0057] In the present invention, for any new energy power source grid-connected system, the following equivalent treatment can be performed: The grid side of the new energy grid-connected system is equivalently regarded as an ideal power supply E G , and the voltage of this equivalent power supply is And denote the voltage at the grid connection point of the new energy as The voltage at the access point of the new energy system is Without loss of generality, denote the connection impedance between the equivalent busbar of the system and the fault point as Z1, the connection impedance between the busbar of the new energy power source and the fault point as Z2, and the connection impedance of the fault point to the ground as Z eq . And respectively assume that when a three-phase short circuit occurs, the current flowing into the fault point from the grid side is The current flowing from the new energy power source into the fault point is Wherein Is the active current component of the new energy power source, Is the reactive current component of the new energy power source. The active current component and the reactive current component always remain orthogonal. The fault current of the fault point busbar to the ground is I f ;

[0058] When the system is in a steady state, according to the system wiring Figure 2 , the following equations can be written:

[0059]

[0060]

[0061]

[0062]

[0063] Through (1) to (4), And

[0064]

[0065]

[0066]

[0067]

[0068] Step 102: Determine the reactive current adjustment coefficient under system fault conditions, and solve the unstable voltage at the grid connection point of the new energy under system fault conditions based on the reactive current adjustment coefficient and the system steady-state equation

[0069] Preferably, determining the reactive current adjustment coefficient under system fault conditions includes:

[0070]

[0071] Where k is the reactive current adjustment coefficient and j is the imaginary unit.

[0072] Preferably, the value of k is not greater than 3.

[0073] Preferably, based on the reactive current adjustment coefficient and the system steady-state equation, the unstable voltage at the new energy grid connection point under system fault conditions is solved including:

[0074]

[0075] When a short-circuit fault occurs in the system in the present invention, the new energy power source detects the voltage drop at the grid connection point and will increase the reactive current through the reactive power control link to try to maintain the system voltage, playing a role in system voltage support and regulation. In formula (6), is the reactive current provided by the new energy power source. Taking the low voltage ride-through condition as an example in the present invention, considering that the reactive current and the active current are orthogonal and believing that the magnitude of the reactive current is only related to the depth of voltage drop, the reactive current is specifically expressed as:

[0076]

[0077] In formula (9), k is the reactive current adjustment coefficient, usually taking 1.5, and j is the imaginary unit;

[0078] Step5: Substitute (9) into (6) and after arrangement, we can get:

[0079]

[0080] The system voltage can be obtained according to the power flow calculation result The active current component of the new energy power source According to the system equivalent result, the connection impedance Z1 between the system equivalent bus and the fault point, the connection impedance Z2 between the new energy power source bus and the fault point, and the fault point grounding connection impedance Z can be obtained eq ; According to the set parameters of the new energy power source, the reactive current adjustment coefficient k can be obtained. Substituting the above physical quantities into formula (10), the voltage at the new energy grid connection point during a three-phase short-circuit disturbance under this condition can be obtained

[0081] Step 103: Compare the unstable voltage at the new energy grid connection point with the preset stable critical voltage value, and evaluate the voltage support ability of the new energy power source according to the comparison result.

[0082] Preferably, compare the unstable voltage at the new energy grid connection point with the preset stable critical voltage value, and evaluate the voltage support ability of the new energy power source according to the comparison result, including:

[0083] When the unstable voltage When the voltage is greater than the critical voltage of stability, there is no risk of broadband oscillation in the new energy power source;

[0084] When the voltage at the new energy grid connection point is unstable When it is less than the critical voltage of stability, there is no risk of broadband oscillation in the new energy power source.

[0085] Through engineering experience and transient simulation, the critical voltage of stability U RE of Rec can be obtained. In subsequent analysis, this critical voltage U Rec can be used to judge whether there is a possibility of voltage instability in the new energy power source under this working condition, that is, when a three-phase short circuit occurs, U RE If it is greater than U Rec it means that there is no risk of broadband oscillation in the new energy power source. If If it is less than U Rec it means that there is a risk of broadband oscillation in the new energy power source. Thus, the voltage support ability of the power grid under this working condition can be judged.

[0086] Taking the direct-drive wind turbine connected to the system shown in Figure 2 as an example, by setting different operating conditions of the new energy, the effectiveness of the evaluation index is tested. Figure 2 Among them, U PS is the voltage at the system connection point, is the voltage at the new energy grid connection point, Z eq is the equivalent connection impedance between the system connection point and the grounding fault point, Z1 is the system equivalent connection impedance, and Z2 is the connection impedance between the new energy grid connection point and the system connection point.

[0087] When the voltage crossing current control coefficients of the new energy power source are 0.8 and 1.5 respectively, the stability of the new energy grid connection is explored under different impedances Z1 and voltage drop depths. The voltage curves at the new energy grid connection point are as shown in Figure 3 and 4 shown.

[0088] This invention takes k values of 0.8 or 1.5 as examples for illustration, but the implementation mode of this invention is not limited to this.

[0089] Under the working condition of k = 0.8, when the connection impedance Z1 is 0.52 pu, the quasi-steady state voltage during the fault is 0.2992, and the system can still maintain stability after the short-circuit disturbance. When the impedance Z1 is increased to 0.55 pu, the quasi-steady state voltage during the fault drops rapidly to 0.1835, and at the same time, the new energy power source shows continuous oscillation after the short-circuit disturbance. Thus, it can be judged that the value of U Rec is 0.298.

[0090] Changing k to 1.5 and Z1 to 0.55 pu, U REDuring the fault, the quasi-steady state is 0.2981, and the system can remain stable after the short-circuit disturbance; when Z1 is increased to 0.58 pu, after the short circuit the quasi-steady state voltage during the fault drops to 0.2978, and the system becomes unstable. Thus, it is verified that the critical value U of the system under this condition Rec is 0.298.

[0091] Considering the power grid structure, the magnitude of the short-circuit disturbance, and the self-control coefficient of the new energy source, the present invention can quickly judge the voltage stability and voltage support ability of the new energy power source under short-circuit disturbance, avoid full-network fault scanning and transient simulation calculations, and reduce the workload. The stable critical value U calculated by the method of the present invention Rec has sufficient accuracy and can adapt to various operation modes of the power system.

[0092] Figure 5 is a system structure diagram for evaluating the voltage support ability of a new energy power source according to a preferred embodiment of the present invention.

[0093] As Figure 5 shown, the present invention provides a system for evaluating the voltage support ability of a new energy power source, and the system includes:

[0094] A solving unit 501, configured to determine a system steady-state equation for solving the voltage at the new energy grid connection point in the steady state; determine a reactive current adjustment coefficient under system fault conditions, and based on the reactive current adjustment coefficient and the system steady-state equation, solve the unstable voltage at the new energy grid connection point under system fault conditions

[0095] Preferably, the solving unit 501 is configured to determine a system steady-state equation for solving the voltage at the new energy grid connection point in the steady state, specifically:

[0096]

[0097] wherein, is the equivalent power supply voltage on the power grid side, is the active current component of the new energy power source, is the reactive current component of the new energy power source, Z eq is the grounding connection impedance of the fault point, Z1 is the connection impedance between the power grid side and the fault point, and Z2 is the connection impedance between the new energy and the fault point.

[0098] Preferably, the solving unit 501 is configured to determine a reactive current adjustment coefficient under system fault conditions, specifically:

[0099]

[0100] wherein, k is the reactive current adjustment coefficient, and j is the imaginary unit.

[0101] Preferably, k is taken not greater than 3.

[0102] Preferably, the solving unit 501 is configured to solve the unstable voltage at the new energy grid connection point under the system fault condition based on the reactive current adjustment coefficient and the system steady-state equation. Specifically, it is used for:

[0103]

[0104] The evaluation unit 502 is configured to compare the unstable voltage at the new energy grid connection point with a preset stable critical voltage value, and evaluate the voltage support ability of the new energy power source according to the comparison result.

[0105] Preferably, the evaluation unit 502 is configured to compare the unstable voltage at the new energy grid connection point with a preset stable critical voltage value, and evaluate the voltage support ability of the new energy power source according to the comparison result. Specifically, it is used for:

[0106] When the unstable voltage at the new energy grid connection point is greater than the stable critical voltage value, there is no risk of broadband oscillation for the new energy power source;

[0107] When the unstable voltage at the new energy grid connection point is less than the stable critical voltage value, there is no risk of broadband oscillation for the new energy power source.

[0108] A system for evaluating the voltage support ability of a new energy power source according to a preferred embodiment of the present invention corresponds to a method for evaluating the voltage support ability of a new energy power source according to a preferred embodiment of the present invention, and will not be elaborated herein.

[0109] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can be implemented in the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can be implemented in the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention can be implemented in various computer languages, for example, object-oriented programming languages such as Java and interpreted scripting languages such as JavaScript.

[0110] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and combinations of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processors of general-purpose computers, special-purpose computers, embedded processors, or other programmable data processing devices to generate a machine, such that the instructions executed by the processors of the computer or other programmable data processing devices produce means for implementing the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 or means for implementing the functions specified in one or more of the blocks.

[0111] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory produce a manufactured article including instruction means that implement the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 or means for implementing the functions specified in one or more of the blocks.

[0112] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operational steps are performed on the computer or other programmable device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more of the flows Figure 1 one or more of the flows and / or blocks Figure 1 or means for implementing the functions specified in one or more of the blocks.

[0113] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they learn the basic creative concepts. Therefore, the appended claims are intended to be construed to include the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0114] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

[0115] The present invention has been described by referring to a few embodiments. However, as is well known to those skilled in the art, as defined by the appended patent claims, other embodiments equivalent to those disclosed above of the present invention equally fall within the scope of the present invention.

[0116] Generally, all terms used in the claims are construed according to their ordinary meaning in the technical field, unless otherwise expressly defined therein. All references to "a / the [device, component, etc.]" are to be construed openly as being at least one instance of the device, component, etc., unless otherwise expressly stated. The steps of any method disclosed herein need not be performed in the exact order disclosed, unless expressly stated.

Claims

1. A method for evaluating the voltage support ability of a new energy power source, the method comprising: Determining a system steady-state equation for solving the voltage at the new energy grid connection point in the steady state; The determining of the system steady-state equation for solving the voltage at the new energy grid connection point in the steady state includes: Among them, is the equivalent power supply voltage on the grid side, is the active current component of the new energy power supply, is the reactive current component of the new energy power supply, Z eq is the grounding connection impedance at the fault point, Z1 is the connection impedance between the grid side and the fault point, and Z2 is the connection impedance between the new energy and the fault point; Determine the reactive current adjustment coefficient under system fault conditions, and solve for the unstable voltage at the new energy grid connection point under system fault conditions based on the reactive current adjustment coefficient and the system steady-state equation The determination of the reactive current adjustment coefficient under system fault conditions includes: where k is a reactive current adjustment coefficient and j is the imaginary unit; Compare the unstable voltage at the new energy grid connection point with the preset stable critical voltage value, and evaluate the voltage support ability of the new energy power source according to the comparison result.

2. According to the method described in claim 1, the value of k is taken not greater than 3.

3. The method according to claim 1, which solves for the unstable voltage at the new energy grid connection point under system fault conditions based on the reactive current adjustment coefficient and the system steady-state equation comprising:

4. According to the method described in claim 1, the unstable voltage at the new energy grid connection point is compared with a preset stable critical voltage value, and the voltage support ability of the new energy power source is evaluated according to the comparison result, including: When the unstable voltage at the new energy grid connection point is greater than the stable critical voltage, there is no risk of broadband oscillation in the new energy power source; When the unstable voltage at the new energy grid connection point is less than the stable critical voltage, there is no risk of broadband oscillation in the new energy power source.

5. A system for evaluating the voltage support ability of a new energy power source, the system comprising: A solving unit for determining a system steady-state equation for solving the voltage at the new energy grid connection point in the steady state; Determine the reactive current adjustment coefficient under system fault conditions, and solve the unstable voltage at the new energy grid connection point under system fault conditions based on the reactive current adjustment coefficient and the system steady-state equation The solving unit for determining a system steady-state equation for solving the voltage at the new energy grid connection point in the steady state, specifically for: Among them, is the equivalent power supply voltage on the grid side, is the active current component of the new energy power supply, is the reactive current component of the new energy power supply, Z eq is the grounding connection impedance at the fault point, Z1 is the connection impedance between the grid side and the fault point, and Z2 is the connection impedance between the new energy and the fault point; The solving unit for determining the reactive current adjustment coefficient under system fault conditions, specifically for: where k is a reactive current adjustment coefficient and j is the imaginary unit; An evaluation unit for comparing the unstable voltage at the new energy grid connection point with a preset stable critical value voltage, and evaluating the voltage support capacity of the new energy power source according to the comparison result.

6. The system according to claim 5, wherein the solving unit is configured to solve the unstable voltage at the new energy grid connection point under the system fault condition based on the reactive current adjustment coefficient and the system steady-state equation. Specifically, it is configured to:

7. The system according to claim 5, wherein the evaluation unit is configured to compare the unstable voltage at the new energy grid connection point with a preset stable critical voltage value, and evaluate the voltage support capability of the new energy power source according to the comparison result, specifically configured to: Compare the unstable voltage at the new energy grid connection point with a preset stable critical voltage value, and evaluate the voltage support capability of the new energy power source according to the comparison result, specifically configured to: When the unstable voltage at the new energy grid connection point is greater than the stable critical voltage, there is no risk of broadband oscillation in the new energy power source; When the unstable voltage at the new energy grid connection point is less than the stable critical voltage, there is no risk of broadband oscillation in the new energy power source.

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