Method, system, device and medium for determining over-current capacity of network-forming converters considering transient synchronization stability

Abstract

The present invention belongs to the technical field of network-forming converters, and particularly relates to a method, system, device, and medium for determining the overcurrent capacity of network-forming converters. Aiming at the deficiencies of the existing method for calculating the current limit value corresponding to the critical clearing time of network-forming converters, which has a large amount of calculation, long time consumption, or cannot obtain the calculation result, the present invention adopts the following technical solutions: A method for determining the overcurrent capacity of network-forming converters considering transient synchronous stability, including: establishing a reduced-order simplified model of the network-forming converter under short-circuit faults; obtaining the electromagnetic power curves under steady state, during transient faults, and after fault clearing; obtaining the mechanical power curve considering damping power consumption; calculating the fault critical clearing angle and critical clearing time under the initial current limit and determining whether the requirements are met; increasing the current limit value until the calculated fault critical clearing time is greater than the actual fault clearing time. The beneficial effect of the present invention is: quickly and accurately obtaining the required minimum current limit value.

Description

Technical Field

[0001] The present invention belongs to the technical field of grid-forming converters, and particularly relates to a method, system, device and medium for determining the overcurrent capacity of a grid-forming converter considering transient synchronous stability. Background Art

[0002] In recent years, grid-forming (GFM) converters based on virtual synchronous generator (VSG) control have been gradually widely used. The grid-forming converter based on VSG control realizes synchronization with the power grid by simulating the characteristics of the synchronous machine swing equation. Compared with the grid-following (GFL) converter that relies on the phase-locked loop for synchronization, the grid-forming converter has better adaptability to weak power grids. At present, grid-forming transformation tests have been completed in several wind farms in China.

[0003] However, since the grid-forming converter exhibits a voltage source characteristic externally, during a voltage dip when a fault occurs in the external power grid, the converter control system will generate a current reference value much higher than the rated current. Since the grid-forming converter is connected to the grid through power electronic devices, its current limit is much lower than that of a synchronous generator. At this time, the converter cannot increase the current to the reference value and can only operate in the current saturation (limiting) mode, and externally changes to a current source characteristic.

[0004] In addition, due to the simulation of the synchronous machine power angle swing equation, the grid-forming converter has a power angle characteristic similar to that of a synchronous machine under large disturbances, so there is also a problem of transient power angle instability. Existing related research shows that the converter is more likely to cause power angle instability under current limiting conditions, and the lower the current limit, the more serious the power angle instability problem.

[0005] The invention patent application with the publication number CN117674013A discloses a method and device for calculating the critical clearing time of a grid-forming converter. The method includes: according to the law of conservation of energy, the transient damping consumption energy in the fault is equal to the difference between the total transient energy at the fault occurrence moment and the fault clearing moment, and the transient damping consumption energy from the critical clearing angle to the maximum swing angle at the fault clearing moment is equal to the difference between the total transient energy at the fault clearing moment and the total transient energy at the maximum swing angle moment. These two are used as the system transient consumption energy equations in the fault and solved to obtain the critical clearing angle and the corresponding angular frequency, and then the critical clearing time is calculated.

[0006] The aforementioned invention patent application simultaneously considers the influences of transient damping and current limiting strategies during faults, and can calculate the critical clearing time of the network-forming converter, thereby solving the technical problem that the calculation results have large errors due to the failure to simultaneously consider the influences of transient damping and current limiting. However, the solution of the aforementioned invention patent application still has the following deficiencies: (1) According to the law of conservation of energy, the dynamic energy of the system is calculated, and the calculation results have very large conservativeness; (2) The energy function of the system is obtained by using the numerical fitting method. The numerical fitting method has problems such as complex process, large calculation amount, and long time consumption, and it is difficult to be applied to the engineering site and online strategy adjustment. At the same time, the numerical method also has the problem of fitting failure; (3) To obtain the critical clearing condition, the Newton-Raphson method needs to be used to solve the nonlinear algebraic equation. The non-existence of the derivative and unreasonable disposal selection are very likely to lead to non-convergence of the solution and unable to give the calculation results; (4) In terms of the idea, the energy function is constructed and approximated, and the method complexity is relatively large; (5) In terms of parameters, the influence of control parameters on the dynamic characteristics of the system cannot or has not been taken into consideration. Summary of the Invention

[0007] Aiming at the deficiencies of the existing methods for calculating the current limit value corresponding to the critical clearing time of the network-forming converter, which have large calculation amount, long time consumption or cannot obtain the calculation results, the present invention provides a method for determining the overcurrent capacity of the network-forming converter, which can quickly and reliably obtain the current limit value corresponding to the critical clearing time. The present invention also provides a system for determining the overcurrent capacity of the network-forming converter, a computer device, and a computer-readable storage medium.

[0008] To achieve the above object, the present invention adopts the following technical solutions: A method for determining the overcurrent capacity of a network-forming converter considering transient synchronous stability, the method for determining the overcurrent capacity of a network-forming converter considering transient synchronous stability includes:

[0009] Step S1: Obtain the control parameters of the network-forming converter, the equivalent impedance of the line, and the grid fault voltage under the short-circuit fault, and establish a reduced-order simplified model of the network-forming converter under the short-circuit fault;

[0010] Step S2: Based on the reduced-order simplified model and the electromagnetic power characteristics of the network-forming converter before and after current limiting, input the initial current limit value to obtain the electromagnetic power curves under steady state, during transient fault, and after fault clearing;

[0011] Step S3: Based on the reduced-order simplified model, scale and approximate the damping consumption power to obtain the mechanical power curve considering the damping consumption power;

[0012] Step S4: According to the equal-area criterion, the electromagnetic power curve, and the mechanical power curve considering the damping consumption power, calculate the critical clearing angle and critical clearing time of the fault under the initial current limit;

[0013] Step S5: Compare the fault critical clearing time under the initial current limit with the actual fault clearing time. If it is less than the actual fault clearing time, it indicates that the converter will have an angle instability problem under this current limit. Then increase the current limit value and repeat Steps S2 to S4 until the calculated fault critical clearing time is greater than the actual fault clearing time. At this time, the current limit value is the minimum limit value that meets the transient stability requirements of the converter.

[0014] As an improvement, in Step S1, the control parameters include the equivalent mechanical inertia, equivalent damping, and power reference value.

[0015] As an improvement, in Step S1, the reduced-order simplified model is expressed as:

[0016] (1)

[0017] Wherein, and are respectively the angle difference and frequency difference between the output angle of the network-forming converter and the grid phase; M and D and and respectively represent the equivalent mechanical inertia, equivalent damping, power reference value, and electromagnetic power of the network-forming converter, and respectively represent the first-order derivatives of the output angle difference and frequency difference of the network-forming converter with respect to time.

[0018] As an improvement, in Step S2, the electromagnetic power curve under steady state is expressed as:

[0019] (2)

[0020] In the formula, is the electromagnetic power under steady state, E is the port voltage of the point of common coupling, is the grid voltage at steady state, is the line impedance;

[0021] The electromagnetic power curve during transient fault is expressed as:

[0022] (3)

[0023] In the formula, is the electromagnetic power during transient fault, is the current limit value, is the grid fault voltage;

[0024] The electromagnetic power curve of the electromagnetic power curve after fault clearing is expressed as:

[0025] (4)

[0026] In the formula, is the electromagnetic power after fault clearing.

[0027] As an improvement, in step S3, the mechanical power curve considering the damping consumption power is expressed as:

[0028] (5)

[0029] In the formula, represents the power reference value considering the damping consumption, represents the maximum deviation between the electromagnetic power that the network-forming converter can output and the power reference value ; and represent the power angle value and the critical clearing angle corresponding to the unstable equilibrium point respectively;

[0030] The maximum deviation Δ P ref between the electromagnetic power that the network-forming converter can output and the power reference value P max is expressed as:

[0031] (6)

[0032] is the point with the largest frequency deviation corresponding to, and is expressed as:

[0033] (7)

[0034] In the formula, represents the angle difference between the output angle of the network-forming converter before the fault and the grid phase.

[0035] As an improvement, in step S4, according to the equal area criterion, the deceleration area and the acceleration area are calculated, and the critical clearing angle δ c of the fault is solved, and the calculation formula is expressed as:

[0036] (8)

[0037] In the formula, represents the maximum value that can reach during the fault, that is, the power angle value corresponding to the unstable equilibrium point;

[0038] After obtaining , the swing equation is numerically solved, and the critical clearing time of the fault is obtained. The swing equation is expressed as:

[0039] (9)

[0040] In the formula, is the second derivative of the output phase of the network-forming converter with respect to time.

[0041] As an improvement, in step S5, it is judged whether the critical clearing time satisfies the following formula:

[0042] (10)

[0043] In the formula, represents the actual fault clearing time.

[0044] The method for determining the overcurrent capacity of the network-forming converter considering transient synchronization stability according to the present invention analyzes the dynamic characteristics of the network-forming converter during the transient synchronization process based on the equal-area criterion theory, quantitatively considers the influence of the damping term on the mechanical power during the transient synchronization process of the network-forming converter, has higher theoretical analysis accuracy, has more accurate calculation of the minimum limit current, and effectively avoids obtaining overly conservative results; approximates the electromagnetic power, and compared with constructing and approximating the energy function, the method complexity is small. Further, only explicit mathematical expression calculations are required, and numerical fitting methods are not used, so the calculation amount is smaller and the speed is faster. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is a flowchart of the method for determining the overcurrent capacity of the network-forming converter considering transient synchronization stability according to an embodiment of the present invention.

[0046] Figure 2 is a schematic diagram of the equal-area analysis process of the power angle curve according to an embodiment of the present invention.

[0047] Figure 3 is an equivalent circuit diagram of the network-forming converter feeding into the system in the simulation verification according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] The technical solutions of the embodiments of the present invention will be explained and described below. However, the following embodiments are only the preferred embodiments of the present invention and not all of them. Based on the embodiments in the embodiments, other embodiments obtained by those skilled in the art without creative efforts all belong to the protection scope of the present invention.

[0049] Refer to Figure 1 , the method for determining the overcurrent capacity of the network-forming converter considering transient synchronization stability according to an embodiment of the present invention includes:

[0050] Step S1, obtain the control parameters of the network-forming converter, the equivalent impedance of the line, and the grid fault voltage under the short-circuit fault, and establish a reduced-order simplified model of the network-forming converter under the short-circuit fault;

[0051] Step S2: Based on the reduced - order simplified model and the electromagnetic power characteristics of the grid - forming converter before and after current limiting, input the initial current limit value to obtain the electromagnetic power curves under steady state, during transient faults, and after fault clearing;

[0052] Step S3: Based on the reduced - order simplified model, scale and approximate the damping power consumption to obtain the mechanical power curve considering the damping power consumption;

[0053] Step S4: According to the equal - area criterion, the electromagnetic power curve, and the mechanical power curve considering the damping power consumption, calculate the fault - limiting clearing angle and the limiting clearing time under the initial current limit;

[0054] Step S5: Compare the fault - limiting clearing time under the initial current limit with the actual fault clearing time. If it is less than the actual fault clearing time, it indicates that the converter will have an angle instability problem under this current limit. Then increase the current limit value and repeat Steps S2 to S4 until the calculated fault - limiting clearing time is greater than the actual fault clearing time. At this time, the current limit value is the minimum limit value that meets the transient stability requirements of the converter.

[0055] In this embodiment, the first step is mainly to obtain basic data such as the controller parameters of the voltage - source converter and the system operating conditions, and establish a reduced - order simplified model of the converter grid - connected system. Ignoring fast - scale dynamics such as the current loop, a second - order mathematical model of the converter grid - connected system under faults is established, expressed as:

[0056] (1)

[0057] Wherein, and are respectively the angle difference and frequency difference between the output angle of the grid - forming converter and the grid phase; M 、 D 、 、 respectively represent the equivalent mechanical inertia, equivalent damping, power reference value, and electromagnetic power of the grid - forming converter, 、 respectively represent the first - order derivatives of the output angle difference and frequency difference of the grid - forming converter with respect to time. In this step, the angle difference δ between the output angle of the grid - forming converter and the grid phase can be calculated, and the angle difference δ changes before and after the fault. The reduced - order simplified model is the basis or prerequisite for the method of this embodiment of the present invention. Only when the reduced - order simplified model is satisfied can the subsequent steps be carried out.

[0058] The second step mainly involves inputting the initial current limit value into the reduced-order simplified model to obtain the electromagnetic power curves under steady state, during transient faults, and after fault clearance. Combining with Figure 2 For further illustration. In the figure, the abscissa is the angle difference between the output angle of the grid-forming converter and the grid phase , and the ordinate P is the electromagnetic power.

[0059] See Figure 2 , before the fault occurs, the converter operates in the voltage source mode. At this time, the converter operates at point a, and the electromagnetic power is as Figure 2 shown by curve I in

[0060] The electromagnetic power curve I, which is also the electromagnetic power curve under steady state, is expressed as:

[0061] (2)

[0062] In the formula, is the electromagnetic power under steady state, E is the port voltage of the point of common coupling, is the grid voltage at steady state, is the line impedance, is the angle difference between the output angle of the grid-forming converter and the grid phase.

[0063] After the fault occurs, the voltage drops instantaneously to , the converter changes to the current source mode, the electromagnetic power curve changes from curve I to curve II, and the operating point drops from point a to point b and gradually runs to point c as the power angle increases.

[0064] The electromagnetic power curve II, which is also the electromagnetic power curve during transient faults, is expressed as:

[0065] (3)

[0066] In the formula, is the electromagnetic power during transient faults, is the current limit value, is the grid fault voltage, is the angle difference between the output angle of the grid-forming converter and the grid phase.

[0067] When the converter runs to point c, the system removes the fault, and at this time the voltage recovers to . However, due to the fact that the phase angle of the converter cannot change suddenly, after the voltage recovers, the converter still operates at point e in the current source mode and gradually decelerates to point f, and the electromagnetic power curve changes from curve II to curve III.

[0068] The electromagnetic power curve III, which is also the electromagnetic power curve after fault clearance, is expressed as:

[0069] (4)

[0070] Wherein, is the electromagnetic power after fault clearing, is the current limit value, is the grid voltage at steady state, is the angle difference between the output angle of the network-forming converter and the grid phase.

[0071] After that, if the phase angle continues to increase, the converter will enter the unstable operation region and the system will become unstable; if the phase angle starts to decrease, the operating point will finally re-stabilize at point a and the converter will return to the voltage source operation mode. Under fault conditions, curves I, II, and III together constitute the electromagnetic power curve of the system.

[0072] The third step is mainly to determine the equivalent mechanical power curve after the fault. Since the damping of the network-forming converter is large and cannot be ignored, after considering the damping power consumption, the equivalent mechanical power is no longer a straight line but bends downward, as shown by the red dashed line in Figure 2 .

[0073] To determine the equivalent mechanical power curve, first approximately calculate the maximum deviation value between the electromagnetic power that the network-forming converter can output and the power reference value , which is also the maximum power deviation at point d (the vertical red line part in the figure, that is, the deviation between the power at point d and the power reference value P ref ):

[0074]

[0075] Wherein, represents the maximum deviation value between the electromagnetic power that the network-forming converter can output and the power reference value , D represents the equivalent damping of the network-forming converter, is the corresponding point with the largest frequency deviation;

[0076] The calculation formula of

[0077] (7)

[0078] Wherein, D represents the equivalent damping of the network-forming converter, represents the critical clearing angle corresponding to the unstable equilibrium point, δ 0 represents the angle difference between the output angle of the network-forming converter and the grid phase before the fault, represents the critical clearing angle corresponding to the unstable equilibrium point,M represents the equivalent mechanical inertia of the network-forming converter, represents the power reference value of the network-forming converter, is the electromagnetic power of the network-forming converter during a transient fault;

[0079] Let Figure 2 the red dotted line in be approximated as the broken line adf, and the expression for the equivalent mechanical power of the converter can be written as:

[0080] (5)

[0081] In the formula, represents the power reference value after considering damping consumption, represents the maximum deviation between the electromagnetic power that the network-forming converter can output and the power reference value ; and represent the power angle value and the critical clearing angle corresponding to the unstable equilibrium point (at different stages of ), represents the power reference value of the network-forming converter (before considering damping consumption).

[0082] The fourth step is mainly to calculate the critical clearing angle and the critical clearing time .

[0083] During the transient process, the deceleration area of the system is the plane abcd, and the acceleration area is the plane def. According to the equal area criterion (the deceleration area is equal to the acceleration area, that is, the area of the plane abcd is equal to the area of the plane def), the calculation formula for the critical clearing angle of the system is:

[0084] (8)

[0085] In the formula, represents the maximum value that can reach during the fault, that is, the power angle value corresponding to the unstable equilibrium point; , and are all specific values.

[0086] After obtaining , the critical clearing time of the fault is numerically solved by the swing equation shown below:

[0087] (9)

[0088] In the formula, is the second derivative of the output phase of the network-forming converter with respect to time.

[0089] The fifth step is mainly to determine the minimum current limit of the converter. Judge whether the critical clearing time satisfies the following formula:

[0090] (10)

[0091] In the formula, represents the actual fault clearing time.

[0092] If it is satisfied, the current limit at this time is the minimum current limit; if it is not satisfied, increase the current limit value and repeat the above steps to recalculate the critical clearing time until the critical clearing time satisfies the above formula. Output the current limit value at this time, which is the minimum current limit to ensure that the system does not experience transient instability. The actual fault clearing time can be obtained through simulation, and the actual fault clearing time is determined by simulating the occurrence of a fault .

[0093] Build a single-fed system of the grid-forming converter as shown in Figure 3 . In the figure, Figure 3 where represents the DC capacitor voltage, E represents the internal potential of the grid-forming converter input, I represents the output current of the grid-forming converter, represents the equivalent grid voltage. The DC side voltage is given as 1.0 p.u. (per unit value), and the reference value of the active power is given as 0.8 p.u., and the current limit value is generally 1.1 - 1.3 p.u.; the pre-fault grid voltage is 1.0 p.u., and during the fault drops to 0.5 p.u., and the voltage amplitude after the fault recovers to 0.9 p.u. At this time, the initial current limit value starts to be calculated from 1.1 p.u. After the voltage drop, the system cannot be stable; after multiple iterative calculations, when the current limit value is 1.25 p.u., the system can remain stable after the voltage drop. The current limit value at this time is the minimum current limit value that satisfies transient synchronous stability, thus verifying the effectiveness of the method of this embodiment.

[0094] In this embodiment, no numerical fitting is required, and only explicit mathematical expression calculations are needed, so there will be no problem of non-convergence of solving algebraic equations in CN117674013A.

[0095] This embodiment of the present invention also provides a system for determining the overcurrent capacity of the grid-forming converter, including:

[0096] A reduced-order model construction module, configured to obtain the control parameters of the grid-forming converter, the line equivalent impedance, and the grid fault voltage under a short-circuit fault, and establish a reduced-order simplified model of the grid-forming converter under a short-circuit fault;

[0097] An electromagnetic power curve plotting module, configured to input an initial current limit value into a reduced-order simplified model based on the reduced-order simplified model and the electromagnetic power characteristics of the network-forming converter before and after current limiting, so as to obtain electromagnetic power curves under steady state, during transient faults, and after fault clearing;

[0098] A mechanical power curve plotting module, configured to perform scaling approximation on the damping consumption power based on the reduced-order simplified model to obtain a mechanical power curve considering the damping consumption power;

[0099] A critical clearing time calculation module, configured to calculate the critical clearing angle and the critical clearing time of a fault under the initial current limit;

[0100] A comparison and update module, configured to compare the critical clearing time of a fault under the initial current limit with the actual fault clearing time. If it is less than the actual fault clearing time, it indicates that the converter will have an angle instability problem under this current limit. At this time, increase the current limit value until the calculated critical clearing time of the fault is greater than the actual clearing time;

[0101] A result output module, configured to output the minimum current limit value when the critical clearing time of the fault is greater than the actual clearing time.

[0102] An embodiment of the present invention further provides a computer device, including a processor and a storage medium. A computer program is stored in the storage medium. When the computer program is executed by the processor, the above-mentioned method for determining the overcurrent capacity of a network-forming converter considering transient synchronous stability is implemented.

[0103] An embodiment of the present invention further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed, the above-mentioned method for determining the overcurrent capacity of a network-forming converter considering transient synchronous stability is implemented.

[0104] As described above, the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes but is not limited to the content described in the above specific implementation manner. Any modification that does not deviate from the functional and structural principles of the present invention will be included in the scope of the claims.

Claims

1. A method for determining the overcurrent capacity of a grid-connected converter considering transient synchronization stability, characterized in that: The method for determining the overcurrent capacity of a grid-connected converter considering transient synchronization stability includes: Step S1, obtaining control parameters of the grid-type converter, line equivalent impedance and grid fault voltage under a short-circuit fault, and establishing a reduced-order simplified model of the grid-type converter under a short-circuit fault; Step S2, based on the reduced-order simplified model and the electromagnetic power characteristics of the grid-type converter before and after current limiting, input the initial current limiting value to obtain the electromagnetic power curves in steady state, during transient fault and after fault clearing; Step S3, based on the reduced-order simplified model, scaling and approximating the damping power consumption to obtain a mechanical power curve after considering the damping power consumption; Step S4, calculating the fault limit removal angle and limit removal time under the initial current limitation according to the equal area rule, the electromagnetic power curve and the mechanical power curve after considering the damping power consumption; Step S5, compare the fault limit removal time under the initial current limit with the actual fault removal time. If the fault limit removal time under the initial current limit is less than the actual fault removal time, it means that the converter will have a power angle instability problem under the current limit. Then increase the current limit value and repeat steps S2 to S4 until the calculated fault limit removal time is greater than the actual fault removal time. The current limit value at this time is the minimum limit value that meets the transient stability requirements of the converter. In step S4, according to the equal area rule, the deceleration area and the acceleration area are calculated to obtain the fault limit removal angle , the calculation formula is expressed as: (8) In the formula, is the angle difference between the grid-connected converter output angle and the grid phase, Indicates when a fault occurs value, Indicates a fault The maximum value that can be achieved is the power angle value corresponding to the unstable equilibrium point. represents the limit resection angle corresponding to the unstable equilibrium point, Represents the power reference value of the grid-connected converter, is the electromagnetic power during transient fault, It indicates the power reference value after considering the damping consumption; get After that, the swing equation is numerically solved to obtain the fault limit clearing time , the swing equation is expressed as: (9) In the formula, M represents the equivalent mechanical inertia of the grid-type converter, is the second-order derivative of the grid-type converter output phase with respect to time, is the time when the fault occurs, is the fault limit clearing time.

2. The method for determining the overcurrent capacity of a grid-connected converter considering transient synchronization stability according to claim 1 is characterized in that: In step S1, the control parameters include equivalent mechanical inertia, equivalent damping, and power reference value.

3. The method for determining the overcurrent capacity of a grid-connected converter considering transient synchronization stability according to claim 2 is characterized in that: In step S1, the reduced-order simplified model is expressed as: (1) in, , They are the angle difference and frequency difference between the grid-forming converter output angle and the grid phase; M , D , , Respectively represent the equivalent mechanical inertia, equivalent damping, power reference value and electromagnetic power of the grid-type converter, , They respectively represent the first-order derivatives of the output angle difference and frequency difference of the grid-type converter with respect to time.

4. The method for determining the overcurrent capacity of a grid-connected converter considering transient synchronization stability according to claim 3 is characterized in that: In step S2, the electromagnetic power curve in steady state is expressed as: (2) In the formula, is the electromagnetic power in steady state, E is the port voltage at the common coupling point, is the grid voltage in steady state, is the line impedance; The electromagnetic power curve during transient fault is expressed as: (3) In the formula, is the electromagnetic power during transient fault, is the current limit value, is the grid fault voltage; The electromagnetic power curve after the fault is cleared is expressed as: (4) In the formula, is the electromagnetic power after the fault is cleared.

5. The method for determining the overcurrent capacity of a grid-connected converter considering transient synchronization stability according to claim 4 is characterized in that: In step S3, the mechanical power curve after considering the damping power consumption is expressed as: (5) In the formula, It represents the power reference value after considering the damping consumption. Indicates that the grid-type converter can output electromagnetic power and power reference value The maximum deviation between and They represent the power angle value and the limit resection angle corresponding to the unstable equilibrium point respectively; The grid-type converter can output electromagnetic power and power reference value The maximum deviation between It is expressed as: (6) yes The corresponding maximum frequency deviation point is expressed as: (7) In the formula, It indicates the angle difference between the output angle of the grid-connected converter and the grid phase before the fault.

6. The method for determining the overcurrent capacity of a grid-connected converter considering transient synchronization stability according to claim 1, characterized in that: In step S5, the limit removal time is determined Does it satisfy the following formula: (10) In the formula, Indicates the actual fault clearing time.

7. A system for determining overcurrent capacity of a grid-connected converter considering transient synchronization stability, applying the method for determining overcurrent capacity of a grid-connected converter considering transient synchronization stability as claimed in any one of claims 1 to 6, characterized in that: The grid-connected converter overcurrent capacity determination system considering transient synchronization stability comprises: A reduced-order simplified model building module is used to obtain the control parameters of the grid-type converter, the line equivalent impedance and the grid fault voltage under a short-circuit fault, and to establish a reduced-order simplified model of the grid-type converter under a short-circuit fault; The electromagnetic power curve drawing module is used to input the initial current limit value into the reduced-order simplified model based on the reduced-order simplified model and the electromagnetic power characteristics of the grid-type converter before and after current limit, and obtain the electromagnetic power curves in steady state, during transient fault and after fault clearing; A mechanical power curve drawing module is used to scale and approximate the damping power consumption based on a reduced-order simplified model to obtain a mechanical power curve after considering the damping power consumption; The limit removal time calculation module is used to calculate the fault limit removal angle and limit removal time under the initial current limitation according to the equal area rule, the electromagnetic power curve and the mechanical power curve after considering the damping power consumption; A comparison and update module is used to compare the fault limit removal time under the initial current limit with the actual fault removal time. If the fault limit removal time is less than the actual fault removal time, the current limit value is increased until the calculated fault limit removal time is greater than the actual removal time. The result output module outputs the minimum current limit value when the fault limit removal time is greater than the actual removal time.

8. A computer device comprising a processor and a storage medium, wherein the storage medium stores a computer program, characterized in that: When the computer program is executed by a processor, the method for determining the overcurrent capacity of a grid-connected converter taking into account transient synchronization stability as described in any one of claims 1 to 6 is implemented.

9. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed, a method for determining the overcurrent capacity of a grid-connected converter taking into account transient synchronization stability as described in any one of claims 1 to 6 is implemented.

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