Transient stability control method, device and equipment of VSG parallel system, medium and product

Abstract

The invention discloses a transient stability control method, device and equipment of a VSG parallel system, a medium and a product, and relates to the field of transient stability of the VSG parallel system.The method comprises the steps that the VSG parallel system is equivalent to a dual-machine parallel system, and an equivalent model corresponding to the VSG parallel system is constructed; determining an optimal time criterion and an optimal power angle criterion for controlling a reference power angle of the VSG in an active control loop in the equivalent model by using an extended equal area rule; and after a fault occurs, performing power electronic control on the converter in the VSG by using the optimal time criterion and the optimal power angle criterion, thereby meeting the transient stability requirement of a power system.

Description

Technical Field

[0001] The present application relates to the field of transient stability of a VSG parallel system, and in particular to a transient stability control method, device, equipment, medium and product of a VSG parallel system. Background Art

[0002] With the continuous deepening of energy conservation and emission reduction in the power industry, the proportion of new clean energy in the power system has continued to rise, making the power electronics of the system more and more obvious, which in turn causes the transient stability problems such as system intermittency, volatility, and nonlinearity to become more and more serious. Virtual Synchronous Generator (VSG) has attracted widespread attention in new energy systems due to its autonomous inertial support capability. However, when facing large disturbances, the VSG parallel system will also experience transient instability like the traditional power grid composed of synchronous machines, and the new energy system often has a small capacity and a single number of units. Traditional transient control methods such as cutting generators and loads cannot meet the transient stability requirements of the power system. Summary of the invention

[0003] The purpose of this application is to provide a transient stability control method, device, equipment, medium and product for a VSG parallel system to solve the problem that traditional transient control methods cannot meet the transient stability requirements of the power system.

[0004] To achieve the above objectives, this application provides the following solutions:

[0005] In a first aspect, the present application provides a transient stability control method for a VSG parallel system, comprising:

[0006] Equivalently equate the VSG parallel system to a dual-machine parallel system, and construct an equivalent model corresponding to the VSG parallel system;

[0007] Determine the optimal time criterion and the optimal power angle criterion for controlling the reference power angle of the VSG in the active power control loop in the equivalent model by using the extended equal area rule;

[0008] After a fault occurs, the converter in the VSG is power-electronically controlled using the optimal time criterion and the optimal power angle criterion.

[0009] In a second aspect, the present application provides a transient stability control device for a VSG parallel system, comprising:

[0010] An equivalent model building module is used to equate the VSG parallel system to a dual-machine parallel system and build an equivalent model corresponding to the VSG parallel system;

[0011] An optimal time criterion and an optimal power angle criterion determination module, used to determine the optimal time criterion and the optimal power angle criterion for controlling the reference power angle of the VSG in the active power control loop in the equivalent model by using the extended equal area rule;

[0012] The power electronic control module is used to perform power electronic control on the converter in the VSG using the optimal time criterion and the optimal power angle criterion after a fault occurs.

[0013] In a third aspect, the present application provides a computer device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the transient stability control method of the VSG parallel system described in any one of the above.

[0014] In a fourth aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements any of the above-described transient stability control methods for a VSG parallel system.

[0015] In a fifth aspect, the present application provides a computer program product, including a computer program, which, when executed by a processor, implements the transient stability control method of the VSG parallel system described in any one of the above.

[0016] According to the specific embodiments provided by the present application, the present application discloses the following technical effects: the present application treats the VSG parallel system as equivalent to a dual-machine parallel system, and constructs an equivalent model corresponding to the VSG parallel system. Based on the extended equal-area rule, the application determines the optimal time criterion and the optimal power angle criterion for controlling the reference power angle of the VSG in the active control loop in the equivalent model, so as to perform power electronic control on the converter in the VSG. By including two control criteria, time and power angle, the transient control effect is optimized, and this control method can ensure system stability by only utilizing the system's own inertia, avoiding the negative effects caused by changing the control parameters, and meeting the transient stability requirements of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 It is a typical control block diagram of a grid-type converter;

[0019] Figure 2is an adaptive active power regulation control strategy; among them, Figure 2 (a) is the block diagram of adaptive active power regulation control. Figure 2 (b) is the power angle characteristic curve after adaptive active power regulation;

[0020] Figure 3 A flow chart of a transient stability control method for a VSG parallel system provided in an embodiment of the present application;

[0021] Figure 4 A VSG parallel system diagram provided for an embodiment of the present application;

[0022] Figure 5 An equivalent model of a VSG parallel system provided in an embodiment of the present application;

[0023] Figure 6 This is a transient control effect diagram under different control angles provided by an embodiment of the present application; wherein, Figure 6 (a) is the block diagram of adaptive active power regulation control. Figure 6 (b) is the power angle characteristic curve after adaptive active power regulation. Figure 6 (a) is the block diagram of adaptive active power regulation control;

[0024] Figure 7 A power angle control block diagram provided for an embodiment of the present application;

[0025] Figure 8 A control flow chart of a transient stability scheme for a VSG parallel system provided in one embodiment of the present application;

[0026] Fig. 9 A schematic diagram of the structure of a computer device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0028] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0029] As the main control strategy for independent new energy systems, grid-based control can be mainly divided into two types: droop control and virtual synchronization control.

[0030] like Figure 1As shown, the inventors know that a grid-connected converter mainly includes: an outer loop of active and reactive power control and an inner loop of current and voltage control. The active control loop adopts virtual synchronous control, which aims to imitate the rotation equation of the actual synchronous machine to make the new energy power source gain inertia and thus play a certain supporting role in the independent power grid.

[0031] Although some inertia of the synchronous machine is simulated, the inertia of this part itself cannot be compared with the mechanical inertia, so the system will still be unstable due to insufficient transient stability. In the face of large disturbance faults, in traditional power grids composed of synchronous machines, the transient stability of the system can often be quickly improved by cutting the machine and load to ensure stability. However, as an independent new energy power grid, it does not have the characteristics of large capacity and multiple units of traditional power grids, so it cannot be controlled by precise cutting of the machine.

[0032] The essential reason for transient instability is the imbalance of power. Therefore, during a power grid fault, the imbalance of active power can be effectively improved by adaptively adjusting the transient control strategy of the active power reference value, so that the VSG has a steady-state operating point even when the power grid fails seriously. Figure 2 As shown in (a), an adaptive regulation link is added to the active power control link of the VSG. This link can adjust k as the power difference ΔP changes when a fault occurs in the independent power grid, and then adjust the reference power. The transient control principle can be further revealed by the power angle characteristic curve.

[0033] like Figure 2 As shown in (b), the control strategy starts when a fault occurs. Assume that P m Adaptive adjustment to P m ', it can be found that the system may also have a balanced stable point at the time of the fault, and the overall net deceleration area of ​​the system increases by A3 after the fault is removed, which can effectively improve the transient stability of the system. However, the active power reference value set by the unit is generally purposeful and should not be changed at will. If the reference power is adjusted too small, it may cause problems such as insufficient system output; in addition, non-fault fluctuations in the load may also cause changes in the active power reference value in this control method, so this control method is not stable.

[0034] like Figure 3 As shown, a transient stability control method for a VSG parallel system provided in an embodiment of the present application is executed by a computer device, specifically, it can be executed by a computer device such as a terminal or a server alone, or it can be executed by a terminal and a server together. In an embodiment of the present application, the method includes the following steps 301 to 303. Among them:

[0035] Step 301: Equivalently equate the VSG parallel system to a dual-machine parallel system, and construct an equivalent model corresponding to the VSG parallel system.

[0036] Step 302: using the extended equal-area rule, determine the optimal time criterion and the optimal power angle criterion for controlling the reference power angle of the VSG in the active power control loop in the equivalent model.

[0037] Step 303: After a fault occurs, use the optimal time criterion and the optimal power angle criterion to perform power electronic control on the converter in the VSG.

[0038] In an exemplary embodiment, the equivalent process of the VSG parallel system is as follows:

[0039] The topology of VSG parallel system is as follows: Figure 4 As shown, it includes n VSGs connected in parallel and loads. The VSGs are connected to a common bus through line impedance, and the common bus is connected to a load.

[0040] Through the principle of critical grouping Figure 4 The VSG parallel system shown is equivalent to a two-machine parallel system, and because the external characteristics of the VSG behave as a voltage source, it can be Figure 4 The circuit is transformed into Figure 5 The equivalent model shown in the figure; VSG is equivalent to a voltage source, and the effective values ​​of the phase voltages of VSG1 and VSG2 are U1 and U2 respectively; the voltage power angles are δ1 and δ2 respectively; the effective value of the phase voltage at the load is U3, and the power angle is set to 0; Z1 is the line impedance between the common connection point (Point of Common Coupling, PCC) 1 and PCC3, which includes the filter reactance of VSG1; Z2 is the line impedance between PCC2 and PCC3, which includes the filter reactance of VSG 1; Z3 is the load equivalent impedance.

[0041] This application mainly analyzes the transient stability of VSG. Therefore, in the modeling process, the reactive loop dynamics that have little impact on transient stability and the voltage and current control inner loop dynamics with faster response speed are not concerned. At this time, the transient characteristic equation of the grid-connected converter is the virtual synchronous rotation equation:

[0042]

[0043] Where: t is time; δ is the power angle of VSG; J is the inertia coefficient of VSG; D P is the equivalent damping coefficient of VSG; ω is the angular frequency of VSG, ω0 is the initial angular frequency of VSG; P m is the equivalent mechanical power, corresponding to the reference power P in the control loop ref ;P eis the equivalent electromagnetic power of VSG, corresponding to the actual power P in the active control loop.

[0044] From formula (1), we can know that the power angle equation of VSG1 and VSG2 is:

[0045]

[0046] Among them, P m1 is the equivalent mechanical power of VSG1, P m2 is the equivalent mechanical power of VSG2, δ1 is the power angle of VSG1, δ2 is the power angle of VSG2, J1 is the inertia coefficient of VSG1, J2 is the inertia coefficient of VSG2, P e1 is the equivalent electromagnetic power of VSG1, P e2 is the equivalent electromagnetic power of VSG2, D P1 is the equivalent damping coefficient of VSG1, D P2 is the equivalent damping coefficient of VSG2, and t is the time.

[0047] The power angle difference δ between the two is taken as:

[0048] δ=δ 12 =δ1-δ2 (3)

[0049] δ 12 is the power angle difference between VSG1 and VSG2.

[0050] Subtracting the two equations in equation (2) yields:

[0051]

[0052] Assuming that the VSG control coefficients on both sides are similar, the system can be regarded as a single-machine infinite system:

[0053]

[0054] The inertia coefficient J of the newly obtained single-machine infinite system is defined as:

[0055]

[0056] according to Figure 5 The equivalent model shown and Tellegen's law can be obtained from the Norton equation:

[0057]

[0058] in, and are the injected currents at the three common coupling points, and are the line admittances of the three lines respectively.

[0059] definition:

[0060]

[0061] Among them, Y 11 is the amplitude of the equivalent admittance of VSG1; Y 12 is the magnitude of the equivalent admittance between VSG1 and VSG2; Y 22 is the magnitude of the equivalent admittance of VSG2, is the phase angle of the equivalent admittance of VSG1, is the phase angle of equal admittance between VSG1 and VSG2, is the phase angle of the equivalent admittance of VSG2.

[0062] According to Kirchhoff's current law:

[0063]

[0064] The output power of VSG1 and VSG2 is:

[0065]

[0066] in, is the apparent power of VSG1, is the apparent power of VSG2, is the phase voltage of VSG1, is the phase voltage of VSG2, is the conjugate of the VSG1 current vector, is the conjugate of the VSG2 current vector.

[0067] Substituting equation (8) and equation (9) into equation (10) and taking the real part, the output active power of the virtual synchronous machine can be obtained as:

[0068]

[0069] Substituting equation (11) into the electromagnetic power part of equation (5) yields:

[0070]

[0071] Where:

[0072]

[0073]

[0074]

[0075] In an exemplary embodiment, the transient stability judgment process of the Extended Equal Area Criterion (EEAC) is as follows:

[0076] The method of adjusting the active power reference value has the disadvantage of instability. Therefore, this application designs a transient control scheme for accurately controlling the power angle of the VSG parallel system to improve the transient stability of the system. It can be seen from formula (12) that the equivalent power angle characteristic curve of the VSG parallel system is a sine curve. Therefore, the transient control effects under different control angles are compared below. u To control the power angle during cutting in.

[0077] according to Figure 6 From (a) and (b), it can be seen that the larger the power angle reduction value, the better. If the power angle change is too large, the power angle is shifted to δ u2 And exceeds δ1, it can be seen that the system has a partial acceleration area A3, which is not conducive to the stability of the system. Therefore, δ1 is defined as the critical point of this power angle control scheme. Figure 6 (c) It can be seen that when δ u When it is at δ2, the control power angle is reduced to δ1, and the deceleration area is the largest at this time. Therefore, δ1 is both the critical point and the optimal point of this power angle control scheme. Therefore, the optimal control effect of this scheme is as follows: Figure 6 As shown in (c).

[0078] According to the above determination process, a specific control block diagram is proposed, such as Figure 7 shown.

[0079] like Figure 8 As shown, the specific control steps of the transient control scheme are as follows:

[0080] Step 401: obtain a reference power angle δ of the VSG through an active power control loop, and obtain actual power P through measurement.

[0081] Step 402: Ensure control cut-in time t c Greater than the fault clearing time t t Under the premise of ref The equality comparator determines whether they are equal; if they are not equal, the actual power P is continued to be measured; if they are equal, the output control cut-in time t c .

[0082] Step 403: Obtain the coefficient P in the power angle equation according to the voltages U1 and U2 after the fault is cleared and the inertia coefficient of the VSG. max ; Using P max And the reference power angle δ constructs the system power angle equation, and chooses any P eT >Pm The power angle c and c+π, c-π corresponding to the moment are used as the upper and lower limits of the limiter to limit the power angle range; finally, the power angle is compared with the reference value P ref Compare and then obtain the accurate power angle difference Δδ.

[0083] Step 404: Use the power angle difference Δδ as the amplitude of the step link, and control the cut-in time t c When the step link is added to the active loop, the reference power angle δ obtained in step 1 is accurately corrected, and the reference power angle δ′ after the transient stability improvement scheme is implemented is output.

[0084] Figure 7 The two power angles δ1 and δ2 are the system equivalent power angle characteristic curves and mechanical power P obtained by EEAC analysis. m The difference between the two is used as the power angle criterion of control, and the time corresponding to δ2 is used as the time criterion of control.

[0085] In an exemplary embodiment, the process of determining the optimal time criterion specifically includes: measuring the actual power; under the premise of ensuring that the control cut-in time is greater than the fault removal time, judging whether the actual power is equal to the active power reference value; if so, outputting the control cut-in time; the control cut-in time is the optimal time criterion; if not, continuing to measure the actual power.

[0086] In an exemplary embodiment, the determination process of the optimal power angle criterion specifically includes: determining the reference power angle of the VSG according to the active control loop, and obtaining the voltage after the fault is removed; the voltage includes the effective value of the phase voltage of the two VSGs connected in parallel in the equivalent model; the VSG includes VSG1 and VSG2; determining the power angle equation coefficient of the active control loop according to the voltage after the fault is removed and the inertia coefficient of the VSG; constructing the system power angle equation according to the power angle equation coefficient and the reference attack angle, and selecting P in the equivalent power angle characteristic curve of the VSG parallel system eT >P m The power angle c corresponding to the time; where P eT is the power after fault removal, P m is the equivalent mechanical power; c+π and c-π are respectively used as the upper and lower limits of the limiter to limit the power angle range, and the first power angle of VSG1 and the second power angle of VSG2 are determined; the first output active power of VSG1 and the second output active power of VSG2 are determined according to the first power angle, the second power angle and the coefficient of the system power angle equation; based on the first output active power, the second output active power and the active power reference value, the corrected first power angle and the corrected second power angle are determined, and the power angle difference is calculated; the power angle difference is the optimal power angle criterion.

[0087] In an exemplary embodiment, based on the first output active power, the second output active power and the active power reference value, determining the corrected first power angle and the corrected second power angle, and calculating the power angle difference, specifically includes: judging whether the voltage level and the inertia coefficient of VSG1 and VSG2 are less than a set threshold; if so, outputting the power after the fault is removed; if not, using P c and γ to correct the first power angle and the second power angle, and determine the power after the fault is removed according to the corrected first power angle and the corrected second power angle; wherein, P c is the power correction value; γ is the power angle correction value; when the power after the fault is removed is equal to the active power reference value, the corrected first power angle and the corrected second power angle are determined, and the power angle difference is calculated.

[0088] In an exemplary embodiment, step 303 specifically includes: the optimal time criterion is the control cut-in time; the optimal power angle criterion is the power angle difference; the power angle difference is used as the amplitude of the step link, and at the control cut-in time, the step link is added to the active control loop to correct the reference attack angle; and the converter in the VSG is power electronically controlled according to the corrected reference angle.

[0089] As the proportion of renewable energy capacity in modern power systems increases, the stability of power systems also decreases. Faced with the characteristics of independent renewable energy power grids with small capacity and few units, traditional protection schemes are no longer applicable. The transient stability improvement scheme designed by this patent can accurately control the power angle through the power electronic control inside the converter after a VSG parallel system failure, and use its own inertia support to restore the system to stability, so that the transient stability of the VSG parallel system is effectively improved. And this scheme can effectively avoid the shortcomings of over-cutting, insufficient inertia, etc. that may be caused by traditional protection schemes such as cutting machines and loads. Due to the flexibility of converter power electronic control in new energy systems, the control scheme proposed in this application includes two control criteria of time and power angle, which can optimize the transient control effect, and this control method uses the system's own inertia to ensure system stability and avoid the negative effects caused by changing control parameters.

[0090] Based on the same inventive concept, the embodiment of the present application also provides a transient stability control device for a VSG parallel system for implementing the transient stability control method for the VSG parallel system involved above. The implementation scheme for solving the problem provided by the device is similar to the implementation scheme recorded in the above method, so the specific limitations in the embodiments of the transient stability control device for one or more VSG parallel systems provided below can refer to the limitations of the transient stability control method for the VSG parallel system above, and will not be repeated here.

[0091] In an exemplary embodiment, a transient stability control device for a VSG parallel system is provided, comprising:

[0092] The equivalent model building module is used to equate the VSG parallel system to a dual-machine parallel system and build an equivalent model corresponding to the VSG parallel system.

[0093] The optimal time criterion and the optimal power angle criterion determination module is used to determine the optimal time criterion and the optimal power angle criterion for controlling the reference power angle of the VSG in the active power control loop in the equivalent model by using the extended equal area rule.

[0094] The power electronic control module is used to perform power electronic control on the converter in the VSG using the optimal time criterion and the optimal power angle criterion after a fault occurs.

[0095] In an exemplary embodiment, a computer device is provided. The computer device may be a server or a terminal. The internal structure diagram thereof may be as follows: Fig. 9 As shown. The computer device includes a processor, a memory, an input / output interface (Input / Output, referred to as I / O) and a communication interface. The processor, the memory and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store transient stability control data of the VSG parallel system. The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, a transient stability control method of a VSG parallel system is implemented.

[0096] In an exemplary embodiment, a computer device is provided, including a memory and a processor, wherein a computer program is stored in the memory, and the processor implements the steps in the above-mentioned method embodiments when executing the computer program.

[0097] In an exemplary embodiment, a computer-readable storage medium is provided, storing a computer program, and when the computer program is executed by a processor, the steps in the above method embodiments are implemented.

[0098] In an exemplary embodiment, a computer program product is provided, including a computer program, and when the computer program is executed by a processor, the steps in the above method embodiments are implemented.

[0099] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant regulations.

[0100] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ReadOnlyMemory, ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (Magnetoresistive RandomAccess Memory, MRAM), ferroelectric random access memory (Ferroelectric RandomAccess Memory, FRAM), phase change memory (Phase Change Memory, PCM), graphene memory, etc. Volatile memory can include random access memory (RandomAccess Memory, RAM) or external cache memory, etc. By way of illustration and not limitation, RAM may be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0101] The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. The non-relational database may include a distributed database based on blockchain, etc., but is not limited thereto. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., but is not limited thereto.

[0102] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0103] The present application uses specific examples to illustrate the principles and implementation methods of the present application. The above examples are only used to help understand the method and core ideas of the present application. At the same time, for those skilled in the art, according to the ideas of the present application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present application.

Claims

1. A transient stability control method for a VSG parallel system, characterized in that: The transient stability control method of the VSG parallel system includes: Equivalently equate the VSG parallel system to a dual-machine parallel system, and construct an equivalent model corresponding to the VSG parallel system; Determine the optimal time criterion and the optimal power angle criterion for controlling the reference power angle of the VSG in the active power control loop in the equivalent model by using the extended equal area rule; After a fault occurs, the converter in the VSG is power-electronically controlled using the optimal time criterion and the optimal power angle criterion.

2. The transient stability control method of the VSG parallel system according to claim 1, characterized in that: The process of determining the optimal time criterion specifically includes: Measure the actual power; Under the premise of ensuring that the control cut-in time is greater than the fault clearing time, judging whether the actual power is equal to the active power reference value; If yes, output the control cut-in time; the control cut-in time is the optimal time criterion; If not, continue measuring the actual power.

3. The transient stability control method of the VSG parallel system according to claim 1, characterized in that: The process of determining the optimal power angle criterion specifically includes: Determine the reference power angle of the VSG according to the active control loop, and obtain the voltage after the fault is removed; the voltage includes the effective value of the phase voltage of the two VSGs connected in parallel in the equivalent model; the VSG includes VSG1 and VSG2; Determining the power angle equation coefficient of the active control loop according to the voltage after the fault is removed and the inertia coefficient of the VSG; The system power angle equation is constructed according to the power angle equation coefficient and the reference attack angle, and P in the equivalent power angle characteristic curve of the VSG parallel system is selected. eT >P m The power angle c corresponding to the time; where P eT is the power after fault removal, P m is the equivalent mechanical power; c+π and c-π are used as the upper and lower limits of the limiter respectively to limit the power angle range and determine the first power angle of VSG1 and the second power angle of VSG2; Determine a first output active power of VSG1 and a second output active power of VSG2 according to the first power angle, the second power angle and a coefficient of the system power angle equation; Based on the first output active power, the second output active power and the active power reference value, a corrected first power angle and a corrected second power angle are determined, and a power angle difference is calculated; the power angle difference is a criterion for an optimal power angle.

4. The transient stability control method of the VSG parallel system according to claim 3, characterized in that: Based on the first output active power, the second output active power and the active power reference value, determining a corrected first power angle and a corrected second power angle, and calculating a power angle difference, specifically includes: Determine whether the voltage level and inertia coefficient of VSG1 and VSG2 are less than the set threshold; If yes, output the power after the fault is removed; If not, use P c and γ to correct the first power angle and the second power angle, and determine the power after the fault is removed according to the corrected first power angle and the corrected second power angle; wherein, P c is the power correction value; γ is the power angle correction value; When the power after the fault is cleared is equal to the active power reference value, a corrected first power angle and a corrected second power angle are determined, and a power angle difference is calculated.

5. The transient stability control method of the VSG parallel system according to claim 3, characterized in that: The system power angle equation coefficient P max for: Among them, U1 is the effective value of the phase voltage of VSG1; U2 is the effective value of the phase voltage of VSG2; Y 12 is the amplitude of the equivalent admittance between VSG1 and VSG2; J1 is the inertia coefficient of VSG1; J2 is the inertia coefficient of VSG2.

6. The transient stability control method of the VSG parallel system according to claim 1, characterized in that: After a fault occurs, the converter in the VSG is controlled by power electronics using the optimal time criterion and the optimal power angle criterion, specifically including: the optimal time criterion is the control cut-in time; the optimal power angle criterion is the power angle difference; Taking the power angle difference as the amplitude of the step link, and adding the step link to the active control loop at the control cut-in time, to correct the reference attack angle; The converter in the VSG is power electronically controlled according to the modified reference bus.

7. A transient stability control device for a VSG parallel system, characterized in that: The transient stability control device of the VSG parallel system comprises: An equivalent model building module is used to equate the VSG parallel system to a dual-machine parallel system and build an equivalent model corresponding to the VSG parallel system; An optimal time criterion and an optimal power angle criterion determination module, used to determine the optimal time criterion and the optimal power angle criterion for controlling the reference power angle of the VSG in the active power control loop in the equivalent model by using the extended equal area rule; The power electronic control module is used to perform power electronic control on the converter in the VSG using the optimal time criterion and the optimal power angle criterion after a fault occurs.

8. A computer device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the transient stability control method for the VSG parallel system according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the transient stability control method of the VSG parallel system described in any one of claims 1 to 6 is implemented.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the transient stability control method of the VSG parallel system described in any one of claims 1 to 6 is implemented.

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