A transient stability judgment method and system for a grid-type converter system

Abstract

The present invention discloses a method and system for judging transient stability of a grid-type converter system, wherein the method comprises: reconstructing the system topology and control strategy based on the type of grid-type equipment to obtain a transient stability analysis model of the system under large disturbance; obtaining transient acceleration energy during a fault period based on the system transient stability analysis model; obtaining the sign of a virtual angular acceleration at the moment of fault clearing; when the sign of the virtual angular acceleration is negative for the first time, obtaining the first transient deceleration energy after the moment of fault clearing; judging whether the unit has first-swing transient stability characteristics based on the first transient deceleration energy and the transient acceleration energy; when the sign of the virtual angular acceleration is negative for the second time, obtaining the second transient deceleration energy after the moment of fault clearing; judging whether the unit has periodic transient stability characteristics based on the first transient deceleration energy, the transient acceleration energy and the second transient deceleration energy.

Description

Technical Field

[0001] The present invention relates to the technical field of grid-type converters, and more particularly to a method and system for determining transient stability of a grid-type converter system. Background Art

[0002] In recent years, with the increasing share of renewable energy and power electronics, grid strength has continued to decline, making inverter-based resources (IBRs) based on a grid-following (GFL) strategy no longer suitable for future grid requirements. Reconfiguring IBR control systems to address diverse grid scenarios, safety and stability requirements, and device types, and leveraging the flexibility of power electronics to address weakening grid strength, presents a new challenge for modern power systems. Currently, grid forming (GFM) technology, as a viable solution, has attracted widespread attention from both academia and industry.

[0003] Numerous research teams have proposed various GFM technology solutions, including droop and related derivative control, virtual synchronous machine control, matching control, and virtual oscillator control. These solutions differ primarily in the mechanisms by which the voltage vector is shaped by the power outer loop under disturbances. For small-disturbance scenarios, research on GFM IBRs, including model optimization, parameter design, control improvements, and stability analysis, is relatively mature. However, analyzing and identifying the transient stability mechanisms of GFM IBRs under large disturbances remains a challenge.

[0004] Therefore, in order to accurately analyze the transient stability problem of GFM IBRs system and reveal the transient stability mechanism of GFM IBRs, a transient stability judgment method of grid-connected converter system based on transient unbalanced energy (TUE) accumulation is needed. Summary of the Invention

[0005] The technical solution of the present invention provides a method and system for judging the transient stability of a grid-type converter system, so as to solve the problem of how to judge the transient stability of a grid-type converter system based on transient unbalanced energy accumulation.

[0006] In order to solve the above problems, the present invention provides a method for determining transient stability of a grid-connected converter system, the method comprising:

[0007] Reconstruct the system topology and control strategy based on the type of networked equipment to obtain the system transient stability analysis model under large disturbances;

[0008] Based on the system transient stability analysis model, obtaining transient acceleration energy during the fault period;

[0009] Get the sign of the virtual angular acceleration at the moment of fault clearing;

[0010] When the sign of the virtual angular acceleration is negative for the first time, obtaining the first transient deceleration energy after the fault is cleared;

[0011] Based on the first transient deceleration energy and the transient acceleration energy, determining whether the unit has first-swing transient stability characteristics;

[0012] When the sign of the virtual angular acceleration is negative for the second time, obtaining the second transient deceleration energy after the fault is cleared;

[0013] Based on the first transient deceleration energy, the transient acceleration energy, and the second transient deceleration energy, it is determined whether the unit has periodic transient stability characteristics.

[0014] Preferably, the method further includes judging the transient stability of the multi-mechanism network type equipment type reconstruction system, including:

[0015] When the sum of the transient acceleration energy and the first transient deceleration energy of each unit is less than or equal to 0, the virtual power angle of each unit returns to the initial stable equilibrium point SEP0, and the multi-mechanism network type equipment type reconstruction system has transient stability;

[0016] When each unit does not have the first transient deceleration energy or the sum of the transient acceleration energy and the first transient deceleration energy is greater than 0, the virtual power angle of each unit cannot return to the initial stable equilibrium point SEP0, and the transient stability of the multi-mechanism network type equipment type reconstruction system is uncertain;

[0017] When the sum of the first transient deceleration energy of each unit, the transient acceleration energy and the second transient deceleration energy is less than or equal to 0, the virtual power angle of each unit returns to the initial stable equilibrium point SEP0, and the multi-mechanism network type equipment type reconstruction system has transient stability;

[0018] When the sum of the first transient deceleration energy of each unit, the transient acceleration energy and the second transient deceleration energy is greater than 0, the virtual power angle of each unit cannot return to the initial stable equilibrium point SEP0, and the multi-mechanism network equipment type reconstruction system does not have transient stability.

[0019] Preferably, the reconstructing of the system topology and control strategy based on the type of networked devices to obtain a transient stability analysis model of the system under large disturbances includes:

[0020] The system transient stability analysis model under large disturbance is:

[0021]

[0022] Where, ΔP1, ΔP2…ΔPi are defined as the transient unbalanced power of units 1, 2…i respectively; P in,1 、P in,2 …P in,i are defined as the port power of the i-th unit and do not include the virtual inertia part; P out,1 、P out,2 …P out,i They are defined as the power transmitted from the i-th unit to the grid;

[0023] The reconstruction system based on the networking device type is divided into different stages:

[0024] Before the fault disturbance (defined as time 0):

[0025] 0=P in,i BF -P out,i BF

[0026] Fault disturbance (0~t c ):

[0027] ΔP i F =P in,i F -P out,i F

[0028] After fault disturbance (t c back):

[0029] ΔP i PF =P in,i PF -P out,i PF

[0030] Where, P in，i BF is the port power of the i-th unit before the fault and does not include the virtual inertia part; P in，i F is the port power of the i-th unit during the fault and does not include the virtual inertia part; P in，i PF is the port power of the i-th unit after the fault and does not include the virtual inertia part; ΔP i F is the transient unbalanced power of the i-th unit during the fault; ΔP i PF is the transient unbalanced power of the i-th unit after the fault; P out，i BF is the power transmitted to the grid by the i-th unit before the fault; P out，iF is the power transmitted to the grid by the i-th unit during a fault; P out，i PF is the power transmitted to the grid by the i-th unit after the fault; BF, F and PF represent the power before, during and after the fault respectively; t c Indicates the time when the fault is cleared.

[0031] Preferably, obtaining the transient acceleration energy during the fault period based on the system transient stability analysis model includes:

[0032] When the sign of the virtual angular acceleration changes from negative to positive, it is defined as the existence of VAA SCP;

[0033] When there is no VAA SCP, the transient unbalanced energy of the i-th unit is:

[0034]

[0035] When VAA SCP exists, the sign change points are obtained as (δ F,1 , t F,1 ),(δ F,2 , t F,2 ),…,(δ F,k , t F,k ); where δ F,1 , δ F,2 …δ F,k are the virtual power angle positions corresponding to each VAA SCP during the fault period; t F,1 , t F,2 …t F,k are the fault time positions of each VAA SCP during the temporary fault period; δ c is the virtual power angle at the moment of fault clearing; k is the number of VAA SCPs during the fault period;

[0036]

[0037] Among them, W F1 、W F2 …W Fk are the transient unbalanced energy accumulated at each VAA SCP during the transient fault period;

[0038] When the transient energy W F,i Decrease to the set dead zone value W D There is no need to calculate the subsequent accumulated transient energy.

[0039] Preferably, when the sign of the virtual angular acceleration is negative for the first time, obtaining the first transient deceleration energy after the fault is cleared includes:

[0040] By t cAfter the fault is cleared, VAA SCP1 first exists, and (δ PF,1 , t PF,1 ), and then the first deceleration energy can be obtained:

[0041]

[0042] Among them, δ PF,1 is the virtual power angle position corresponding to the first VAA SCP after the fault is cleared; t PF,1 This is the fault time position corresponding to the first VAA SCP after the fault is cleared.

[0043] 6. According to the method, the step of determining whether the unit has first-swing transient stability characteristics based on the first transient deceleration energy and the transient acceleration energy includes:

[0044] When the sum of the transient acceleration energy and the first transient deceleration energy of the unit is less than or equal to 0, the unit virtual power angle returns to the initial stable equilibrium point SEP0, and the unit has first-swing transient stability;

[0045] When the sum of the transient acceleration energy and the first transient deceleration energy of the unit is greater than 0, the unit virtual power angle cannot return to the initial stable equilibrium point SEP0, and the unit transient stability is uncertain.

[0046] Preferably, when the sign of the virtual angular acceleration is negative for the second time, obtaining the second transient deceleration energy after the fault is cleared includes:

[0047] By t c After the fault is cleared, VAA SCP2 exists for the second time, and (δ PF,2 , t PF,2 ), obtain the second transient deceleration energy after the fault is cleared:

[0048]

[0049] Among them, δ PF,2 is the virtual power angle position corresponding to the second VAA SCP after the fault is cleared; t PF,2 This is the fault time position corresponding to the second VAA SCP after the fault is cleared.

[0050] Preferably, the determining whether the unit has periodic transient stability characteristics based on the first transient deceleration energy, the transient acceleration energy, and the second transient deceleration energy includes:

[0051] When the sum of the first transient deceleration energy, the transient acceleration energy and the second transient deceleration energy of the unit is less than or equal to 0, the virtual power angle of each unit returns to the periodic equilibrium point SEP1, and the unit has transient stability;

[0052] When the sum of the first transient deceleration energy, the transient acceleration energy and the second transient deceleration energy of the unit is greater than 0, the virtual power angle of each unit cannot return to the periodic equilibrium point SEP1, and the unit becomes transiently unstable.

[0053] According to another aspect of the present invention, a transient stability determination system for a grid-type converter system is provided, the system comprising:

[0054] The initial unit is used to reconstruct the system topology and control strategy based on the type of networked equipment and obtain the transient stability analysis model of the system under large disturbances;

[0055] an acquisition unit, configured to acquire, based on the system transient stability analysis model, a transient acceleration energy during a fault period; acquire a sign of a virtual angular acceleration at the moment of fault clearing; when the sign of the virtual angular acceleration is negative for the first time, acquire a first transient deceleration energy after the moment of fault clearing; determine whether the unit has a first-swing transient stability characteristic based on the first transient deceleration energy and the transient acceleration energy; and when the sign of the virtual angular acceleration is negative for the second time, acquire a second transient deceleration energy after the moment of fault clearing;

[0056] The result unit is used to determine whether the unit has periodic transient stability characteristics based on the first transient deceleration energy, the transient acceleration energy and the second transient deceleration energy.

[0057] Based on another aspect of the present invention, the present invention provides a computer-readable storage medium, characterized in that the computer-readable storage medium stores a computer program, and the computer program is used to execute a method for determining transient stability of a grid-type converter system.

[0058] According to another aspect of the present invention, the present invention provides an electronic device, characterized in that the electronic device includes: a processor and a memory; wherein,

[0059] The memory is a memory for storing instructions executable by the processor;

[0060] The processor is used to read the executable instructions from the memory and execute the instructions to implement a transient stability judgment method for a grid-type converter system.

[0061] The technical solution of the present invention provides a method and system for judging transient stability of a grid-type converter system, wherein the method includes: reconstructing the system topology and control strategy based on the type of grid-type equipment to obtain a transient stability analysis model of the system under large disturbances; obtaining transient acceleration energy during a fault period based on the system transient stability analysis model; obtaining the sign of a virtual angular acceleration at the moment of fault clearing; when the sign of the virtual angular acceleration is negative for the first time, obtaining the first transient deceleration energy after the moment of fault clearing; judging whether the unit has first-swing transient stability characteristics based on the first transient deceleration energy and the transient acceleration energy; when the sign of the virtual angular acceleration is negative for the second time, obtaining the second transient deceleration energy after the moment of fault clearing; judging whether the unit has periodic transient stability characteristics based on the first transient deceleration energy, the transient acceleration energy and the second transient deceleration energy. The technical method of the present invention proposes a transient stability judgment method and system for a grid-type converter system based on TUE accumulation, reveals the difference between its transient response mechanism and that of a traditional synchronous machine system from an energy perspective, and obtains a transient stability judgment method for a GFM IBRs system under control shaping, providing a new perspective for the transient stability analysis of a GFM IBRs system. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings:

[0063] Figure 1 Flowchart of a method for determining transient stability of a grid-type converter system according to a preferred embodiment of the present invention;

[0064] Figure 2 A topological structure diagram of a GFM IBRs grid-connected system according to a preferred embodiment of the present invention;

[0065] Figure 3 A control strategy block diagram of a networked device according to a preferred embodiment of the present invention;

[0066] Figure 4 2 is a block diagram of a transient stability determination method based on TUE accumulation according to a preferred embodiment of the present invention;

[0067] Figure 5 Schematic diagram of transient stability of GFM IBRs grid-connected system with different control parameters under large disturbance according to a preferred embodiment of the present invention;

[0068] Figure 6 A schematic diagram of transient stability of a GFM IBRs grid-connected system with different access system strengths under a large disturbance according to a preferred embodiment of the present invention; and

[0069] Figure 7 1 is a structural diagram of a transient stability judgment system of a grid-type converter system according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0070] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to provide a thorough and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments shown in the accompanying drawings is not intended to limit the present invention. In the accompanying drawings, identical elements are denoted by the same reference numerals.

[0071] Unless otherwise specified, the terms used herein (including technical terms) have the meanings commonly understood by those skilled in the art. In addition, it is understood that terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0072] Figure 1 The present invention is a flow chart of a method for determining transient stability of a grid-type converter system according to a preferred embodiment of the present invention. In order to solve the transient stability problem of a grid-type converter system under large disturbances, most existing studies have adopted the perspective and stability determination method of a traditional synchronous machine system, which fails to reflect the characteristics of rapid transient response and control plasticity of power electronic power supplies. To this end, the present invention proposes a method for determining transient stability of a grid-type converter system based on TUE accumulation, which reveals the difference between its transient response mechanism and that of a traditional synchronous machine system from an energy perspective, and obtains a method for determining transient stability of a GFM IBRs system under control shaping, providing a new perspective for transient stability analysis of a GFM IBRs system.

[0073] In view of the deficiencies in the prior art, the present invention provides a transient stability judgment method for a grid-type converter system based on TUE accumulation.

[0074] like Figure 1 As shown, a method for determining transient stability of a grid-type converter system includes:

[0075] Step 101: Reconstruct the system topology and control strategy based on the type of networked devices to obtain a transient stability analysis model of the system under large disturbances;

[0076] Preferably, the system topology and control strategy are reconstructed based on the type of networked devices to obtain a transient stability analysis model of the system under large disturbances, including:

[0077] The transient stability analysis model of the system under large disturbance is:

[0078]

[0079] Where, ΔP1, ΔP2…ΔP i are defined as the transient unbalanced power of units 1, 2…i respectively; P in,1 、P in,2 …P in,i are defined as the port power of the i-th unit and do not include the virtual inertia part; P out,1 、P out,2 …P out,i They are defined as the power transmitted from the i-th unit to the grid;

[0080] The reconstruction system based on the networking device type is divided into different stages:

[0081] Before the fault disturbance (defined as time 0):

[0082] 0=P in,i BF -P out,i BF

[0083] Fault disturbance (0~t c ):

[0084] ΔP i F =P in,i F -P out,i F

[0085] After fault disturbance (t c back):

[0086] ΔP i PF =P in,i PF -P out,i PF

[0087] Where, P in，i BF is the port power of the i-th unit before the fault and does not include the virtual inertia part; P in，i F is the port power of the i-th unit during the fault and does not include the virtual inertia part; P in，i PE is the port power of the i-th unit after the fault and does not include the virtual inertia part; ΔP i F is the transient unbalanced power of the i-th unit during the fault; ΔP i PF is the transient unbalanced power of the i-th unit after the fault; P out，i BFis the power transmitted to the grid by the i-th unit before the fault; P out，i F is the power transmitted to the grid by the i-th unit during a fault; P out，i PF is the power transmitted to the grid by the i-th unit after the fault; BF, F and PF represent the power before, during and after the fault respectively; t c Indicates the time when the fault is cleared.

[0088] Based on the GFMIBRs system topology and control strategy, the transient stability analysis model of the system under large disturbance is obtained as follows:

[0089]

[0090] Where ΔP i Defined as the transient unbalanced power of the i-th GFM IBR; P in,i Defined as the port power of the i-th GFM IBR and does not include the virtual inertia part; P out,i It is defined as the power transmitted from the i-th GFM IBR to the grid.

[0091] Then, the grid-connected system based on GFM IBRs is divided into different stages:

[0092] 1) Before the fault disturbance (defined as time 0):

[0093] 0=P in,i BF -P out,i BF (2)

[0094] 2) Fault disturbance (0~t c ):

[0095] ΔP i F =P in,i F -P out,i F (3)

[0096] 3) After the fault disturbance (t c back):

[0097] ΔP i PF =P in,i PF -P out,i PF (4)

[0098] Where BF, F and PF represent before, during and after the fault respectively; t c Indicates the time when the fault is cleared.

[0099] Step 102: Obtaining transient acceleration energy during the fault period based on the system transient stability analysis model;

[0100] Preferably, based on the system transient stability analysis model, the transient acceleration energy during the fault period is obtained, including:

[0101] When the sign of the virtual angular acceleration changes from negative to positive, it is defined as the existence of VAA SCP;

[0102] When there is no VAA SCP, the transient unbalanced energy of the i-th unit is:

[0103]

[0104] When VAA SCP exists, the sign change points are obtained as (δ F,1 , t F,1 ),(δ F,2 , t F,2 ),…,(δ F,k , t F,k ); where δ F,1 , δ F,2 …δ F,k are the virtual power angle positions corresponding to each VAA SCP during the fault period; t F,1 , t F,2 …t F,k are the fault time positions of each VAA SCP during the temporary fault period; δ c is the virtual power angle at the moment of fault clearing; k is the number of VAA SCPs during the fault period;

[0105]

[0106] Among them, W F1 、W F2 …W Fk are the transient unbalanced energy accumulated at each VAA SCP during the transient fault period;

[0107] When the transient energy W F,i Decrease to the set dead zone value W D There is no need to calculate the subsequent accumulated transient energy.

[0108] The present invention obtains the transient acceleration energy during the fault period.

[0109] When the sign of the virtual angular acceleration changes from negative to positive, it is defined as VAA SCP (virtual angular acceleration change sign point).

[0110] When VAASCP does not exist, the transient unbalanced energy is:

[0111]

[0112] When VAA SCP exists, the sign change points can be obtained as (δ F,1 , t F,1 ),(δ F,2 , t F,2 ),…,(δ F,k , t F,k ).

[0113]

[0114] In the formula, when the transient energy W F,i Decrease to the set dead zone value W D There is no need to calculate the subsequent accumulated transient energy.

[0115] Step 103: Obtain the sign of the virtual angular acceleration at the moment when the fault is cleared;

[0116] The present invention seeks t c VAA symbol of the moment;

[0117] If the sign of VAA is non-negative, there is no first transient deceleration energy, that is, it is impossible to return to the initial stable equilibrium point, but the transient stability is uncertain.

[0118] If the sign of VAA is negative, then find the first VAASCP1.

[0119] Step 104: When the sign of the virtual angular acceleration is negative for the first time, obtain the first transient deceleration energy after the fault is cleared;

[0120] Preferably, when the sign of the virtual angular acceleration is negative for the first time, obtaining the first transient deceleration energy after the fault is cleared includes:

[0121] By t c After the fault is cleared, VAA SCP1 first exists, and (δ PF,1 , t PF,1 ), and then the first deceleration energy can be obtained:

[0122]

[0123] Among them, δ PF,1 is the virtual power angle position corresponding to the first VAA SCP after the fault is cleared; t PF,1 This is the fault time position corresponding to the first VAA SCP after the fault is cleared.

[0124] The present invention seeks t c The first transient deceleration energy after

[0125] By t c After the first VAA SCP1, we get (δ PF,1 , t PF,1 ), and then the first deceleration energy can be obtained:

[0126]

[0127] Step 105: Based on the first transient deceleration energy and the transient acceleration energy, determine whether the unit has the first swing transient stability characteristic;

[0128] Preferably, judging whether the unit has the first-swing transient stability characteristic based on the first transient deceleration energy and the transient acceleration energy includes:

[0129] When the sum of the transient acceleration energy and the first transient deceleration energy of the unit is less than or equal to 0, the unit virtual power angle returns to the initial stable equilibrium point SEP0, and the unit has first-swing transient stability;

[0130] When the sum of the transient acceleration energy and the first transient deceleration energy of the unit is greater than 0, the unit virtual power angle cannot return to the initial stable equilibrium point SEP0, and the unit transient stability is uncertain.

[0131] The present invention determines whether a generator set has first-swing transient stability characteristics.

[0132] If W F,i +W PF,i 1 ≤0, it can return to the initial equilibrium point SEP0, and the unit has first-swing transient stability;

[0133] If W F,i +W PF,i 1 >0, it is impossible to return to the initial equilibrium point SEP0, but the transient stability of the unit is uncertain.

[0134] Step 106: When the sign of the virtual angular acceleration is negative for the second time, obtain the second transient deceleration energy after the fault is cleared;

[0135] Preferably, when the sign of the virtual angular acceleration is negative for the second time, obtaining the second transient deceleration energy after the fault is cleared includes:

[0136] By t c After the fault is cleared, VAA SCP2 exists for the second time, and (δ PF,2 , t PF,2 ), obtain the second transient deceleration energy after the fault is cleared:

[0137]

[0138] Among them, δ PF,2 is the virtual power angle position corresponding to the second VAA SCP after the fault is cleared; t PF,2 This is the fault time position corresponding to the second VAA SCP after the fault is cleared.

[0139] The present invention continues to obtain the secondary transient deceleration energy;

[0140] By t c After the second VAA SCP2, we get (δ PF,2 , t PF,2 ), and then the secondary deceleration energy can be obtained:

[0141]

[0142] Step 107: Based on the first transient deceleration energy, the transient acceleration energy, and the second transient deceleration energy, determine whether the unit has periodic transient stability characteristics.

[0143] Preferably, judging whether the unit has periodic transient stability characteristics based on the first transient deceleration energy, the transient acceleration energy, and the second transient deceleration energy includes:

[0144] When the sum of the first transient deceleration energy, transient acceleration energy and second transient deceleration energy of the unit is less than or equal to 0, the virtual power angle of each unit returns to the cycle balance point SEP1, and the unit has transient stability;

[0145] When the sum of the first transient deceleration energy, transient acceleration energy, and second transient deceleration energy of the unit is greater than 0, the virtual power angle of each unit cannot return to the periodic equilibrium point SEP1, and the unit becomes transiently unstable.

[0146] The present invention determines whether it has periodic transient stability characteristics;

[0147] If W F,i +W PF,i 1 +W PF,i 2 ≤0, it can return to the periodic equilibrium point SEP1, and the unit has transient stability;

[0148] If W F,i +W PF,i 1 +W PF,i 2 >0, it is impossible to return to the periodic equilibrium point SEP1, the unit virtual power angle continues to oscillate, and transient instability occurs;

[0149] Preferably, the method further includes judging the transient stability of the multi-mechanism network type equipment type reconstruction system, including:

[0150] When the sum of the transient acceleration energy and the first transient deceleration energy of each unit is less than or equal to 0, the virtual power angle of each unit returns to the initial stable equilibrium point SEP0, and the multi-mechanism network type equipment type reconstruction system has transient stability;

[0151] When each unit does not have the first transient deceleration energy or the sum of the transient acceleration energy and the first transient deceleration energy is greater than 0, the virtual power angle of each unit cannot return to the initial stable equilibrium point SEP0, and the transient stability of the multi-mechanism network type equipment type reconstruction system is uncertain;

[0152] When the sum of the first transient deceleration energy, transient acceleration energy and second transient deceleration energy of each unit is less than or equal to 0, the virtual power angle of each unit returns to the initial stable equilibrium point SEP0, and the multi-mechanism network type equipment type reconstruction system has transient stability;

[0153] When the sum of the first transient deceleration energy, transient acceleration energy, and second transient deceleration energy of each unit is greater than 0, the virtual power angle of each unit cannot return to the initial stable equilibrium point SEP0, and the multi-mechanism network equipment type reconstruction system does not have transient stability.

[0154] The present invention obtains transient stability criteria. In a multi-machine GFM IBRs system, each unit needs to meet the following criteria before the multi-machine GFM IBRs system can be considered transiently stable.

[0155] Criterion 1: Satisfy W F,i +W PF,i 1 ≤0, the virtual power angle of each unit can return to SEP0, and the system has transient stability; otherwise, there is no W PF,i 1 or W F,i +W PF,i 1 >0, the virtual power angle of each unit cannot return to SEP0, but the transient stability is uncertain.

[0156] Criterion 2: Full W F,i +W PF,i 1 +W PF,i 2 ≤0, the virtual power angle of each unit can return to SEP1, and the system has transient stability; if W F,i +W PF,i 1 +W PF,i 2 >0, the virtual power angle of each unit cannot return to SEP1 and does not have transient stability.

[0157] The present invention proposes a transient stability judgment method for a grid-connected converter system based on TUE accumulation. Based on the perspective of transient unbalanced energy accumulation, a transient stability judgment method for a single-machine or multi-machine GFM IBRs system is obtained.

[0158] See attached Figures 1 to 6 , now the present invention provides a transient stability judgment method for a grid-type converter system based on TUE accumulation.

[0159] As Figure 2 The GFM IBRs grid-connected system is used as an example to further illustrate the present invention in detail. The specific topology is as follows: Figure 2 As shown in Figure 1, it specifically includes three parts: AC side power grid and transmission line, grid-type converter, and DC side equipment. The system includes n+2 nodes, of which the internal potential nodes of the GFM units are numbered 1 to N, the grid nodes are numbered n+1, and the PCC nodes are numbered n+2. The n grid-type units are connected to the PCC bus through different grid access strengths and then to the AC grid through equivalent transmission line impedance. Among them, P i ,Q i are the active and reactive power output of VSC respectively; E i ,δ i are the potential amplitude and virtual power angle in VSC respectively; U i ,θ i are the voltage amplitude and phase of the VSC port respectively; I i is the VSC output current; Z Li , Z SYS are line transmission impedance and system equivalent impedance respectively; Z Fi , C Fi are the low-pass filter parameters of VSCde; U PCC , E SYS are the voltage at the PCC point and the equivalent voltage amplitude of the AC grid, respectively. Figure 3 The control strategy block diagram of GFM IBRs is given, where ω i With ω g are VSC virtual angular frequency and grid side angular frequency respectively; D P,i With τ i 、J i are virtual damping and inertia coefficient respectively; K P,i With K Q,i are active frequency and reactive voltage droop coefficients respectively; U N,i is the rated AC voltage; P N,i ,Q N,i are the rated active and reactive power of VSC respectively.

[0160] The present invention provides a method for determining transient stability of a grid-connected converter system based on TUE accumulation, the method comprising the following steps:

[0161] Step 1: Based on Figure 2 and Figure 3 The GFM IBRs system topology and control strategy are shown in the figure, and the transient stability analysis model of the system under large disturbance is obtained as shown below.

[0162]

[0163] Where ΔP i Defined as the transient unbalanced power of the i-th GFM IBR; P in,i Defined as the port power of the i-th GFM IBR and does not include the virtual inertia part; P out,i It is defined as the power transmitted from the i-th GFM IBR to the grid.

[0164] Then, the grid-connected system based on GFM IBRs is divided into different stages:

[0165] 1) Before the fault disturbance (defined as time 0):

[0166] 0=P in,i BF -P out,i BF (2)

[0167] 2) Fault disturbance (0~t c ):

[0168] ΔP i F =P in,i F -P out,i F (3)

[0169] 3) After the fault disturbance (t c back):

[0170] ΔP i PF =P in,i PF -P out,i PF (4)

[0171] Where BF, F and PF represent before, during and after the fault respectively; t c Indicates the time when the fault is cleared.

[0172] Step 2: Calculate the transient acceleration energy during the fault period;

[0173] When the sign of the virtual angular acceleration changes from negative to positive, it is defined as VAA SCP (virtual angular acceleration change sign point).

[0174] When there is no VAA SCP, the transient unbalanced energy is:

[0175]

[0176] When VAA SCP exists, the sign change points can be obtained as (δ F,1 , t F,1 ),(δ F,2 , t F,2 ),…,(δ F,k , t F,k ).

[0177]

[0178] In the formula, when the transient energy W F,i Decrease to the set dead zone value W D There is no need to calculate the subsequent accumulated transient energy.

[0179] Step 3: Find t c VAA symbol of the moment;

[0180] If the sign of VAA is non-negative, there is no first transient deceleration energy, that is, it is impossible to return to the initial stable equilibrium point SEP0, but the transient stability is uncertain.

[0181] If the sign of VAA is negative, then find the first VAASCP1.

[0182] Step 4: Calculate t c The first transient deceleration energy after

[0183] By t c After the first VAA SCP1, we get (δ PF,1 , t PF,1 ), and then the first deceleration energy can be obtained:

[0184]

[0185] Step 5: Determine whether the unit has the first-swing transient stability characteristics;

[0186] If W F,i +W PF,i 1 ≤0, it can return to the initial equilibrium point SEP0, and the unit has first-swing transient stability;

[0187] If W F,i +WPF,i 1 >0, it is impossible to return to the initial equilibrium point SEP0, but the transient stability of the unit is uncertain.

[0188] Step 6: Continue to calculate the secondary transient deceleration energy;

[0189] By t c After the second VAA SCP2, we get (δ PF,2 , t PF,2 ), and then the secondary deceleration energy can be obtained:

[0190]

[0191] Step 7: Determine whether it has periodic transient stability characteristics;

[0192] If W F,i +W PF,i 1 +W PF,i 2 ≤0, it can return to the periodic equilibrium point SEP1, and the unit has transient stability;

[0193] If W F,i +W PF,i 1 +W PF,i 2 >0, it is impossible to return to the periodic equilibrium point SEP1, the unit virtual power angle continues to oscillate, and transient instability occurs;

[0194] Step 8: Obtain transient stability criteria. The overall diagram of this method is as follows: Figure 4 In addition, it should be noted that in a multi-machine GFM IBRs system, each unit must meet the following criteria before the multi-machine GFM IBRs system can be considered transiently stable.

[0195] Criterion 1: Satisfy W F,i +W PF,i 1 ≤0, the virtual power angle of each unit can return to SEP0, and the system has transient stability; otherwise, there is no W PF,i 1 or W F,i +W PF,i 1 >0, the virtual power angle of each unit cannot return to SEP0, but the transient stability is uncertain.

[0196] Criterion 2: Full W F,i +W PF,i 1 +W PF,i 2 ≤0, the virtual power angle of each unit can return to SEP1, and the system has transient stability; if WF,i +W PF,i 1 +W PF,i 2 >0, the virtual power angle of each unit cannot return to SEP1 and does not have transient stability.

[0197] The specific simulation verification results are as follows Figure 5 and Figure 6 shown.

[0198] Figure 5 (a) and (b) give K P,i Impact on transient stability characteristics of multi-machine grid-connected system. Figure 5 (a) It can be seen that increasing K P,i It will reduce the acceleration area and expand the deceleration area, TUE will be smaller, which is beneficial to the transient stability of the unit. Units 1 and 2 both meet criterion 1 and have transient stability; the lowest K P,i After the disturbance is cleared, the criteria 1 and 2 of unit 3 are not met, the virtual power angle and frequency continue to oscillate, and transient instability occurs.

[0199] Figure 5 (c) and (d) give J i Impact on transient stability characteristics of multi-machine grid-connected system. Figure 5 (c) and (d) show that increasing J i At the same time, the acceleration and deceleration area is expanded, and the release of the unit's adjustment ability is reduced. P,i The risk of virtual power angle oscillation is increased, but its fluctuation range is reduced. Units 1, 2, and 3 all meet criterion 1 and have transient stability;

[0200] Figure 5 (e) and (f) give P N,i Impact on transient stability characteristics of multi-machine grid-connected system. Figure 5 (e) It can be seen that increasing P N,i , the acceleration area is expanded and the deceleration area is reduced, TUE becomes smaller, which is not conducive to the transient stability of the unit. Figure 5 (f) It can be seen that as P N,i As the value of increases, unit 1 meets criterion 1 and has transient stability; unit 2 does not meet criterion 1 but meets criterion 2 and has transient stability; unit 3 does not meet both criterion 1 and 2 and suffers from transient instability.

[0201] Figure 6 The influence of grid connection strength on the transient stability characteristics of multi-machine grid-connected systems is given.

[0202] Depend on Figure 6From (a) and (b), we can see that under the same equivalent system, as the short-circuit ratio of each unit's grid connection point decreases, the deceleration area shrinks, the TUE increases, and the risk of unit transient instability increases. Units 1 and 2 both meet criterion 1 and have transient stability; unit 3 does not meet criterion 1 or 2 and is transiently unstable. Figure 6 From (c) and (d), we can see that, under the same unit and parameter design, the decrease of the equivalent system short-circuit ratio is not conducive to the transient stability of the unit. It can be seen that all three units do not meet criteria 1 and 2, and the system is transiently unstable.

[0203] Figure 7 1 is a structural diagram of a transient stability judgment system of a grid-type converter system according to a preferred embodiment of the present invention.

[0204] like Figure 7 As shown, the present invention provides a transient stability judgment system for a grid-type converter system, the system comprising:

[0205] Initialization unit 701 is used to reconstruct the system topology and control strategy based on the type of networked devices and obtain a transient stability analysis model of the system under large disturbances;

[0206] An acquisition unit 702 is configured to acquire, based on the system transient stability analysis model, a transient acceleration energy during the fault period; acquire the sign of a virtual angular acceleration at the time of fault clearing; when the sign of the virtual angular acceleration is negative for the first time, acquire the first transient deceleration energy after the fault is cleared; determine whether the unit has first-swing transient stability characteristics based on the first transient deceleration energy and the transient acceleration energy; and when the sign of the virtual angular acceleration is negative for the second time, acquire the second transient deceleration energy after the fault is cleared.

[0207] The result unit 703 is configured to determine whether the unit has periodic transient stability characteristics based on the first transient deceleration energy, the transient acceleration energy, and the second transient deceleration energy.

[0208] Preferably, the method further includes judging the transient stability of the multi-mechanism network type equipment type reconstruction system, including:

[0209] When the sum of the transient acceleration energy and the first transient deceleration energy of each unit is less than or equal to 0, the virtual power angle of each unit returns to the initial stable equilibrium point SEP0, and the multi-mechanism network type equipment type reconstruction system has transient stability;

[0210] When each unit does not have the first transient deceleration energy or the sum of the transient acceleration energy and the first transient deceleration energy is greater than 0, the virtual power angle of each unit cannot return to the initial stable equilibrium point SEP0, and the transient stability of the multi-mechanism network type equipment type reconstruction system is uncertain;

[0211] When the sum of the first transient deceleration energy of each unit, the transient acceleration energy and the second transient deceleration energy is less than or equal to 0, the virtual power angle of each unit returns to the initial stable equilibrium point SEP0, and the multi-mechanism network type equipment type reconstruction system has transient stability;

[0212] When the sum of the first transient deceleration energy of each unit, the transient acceleration energy and the second transient deceleration energy is greater than 0, the virtual power angle of each unit cannot return to the initial stable equilibrium point SEP0, and the multi-mechanism network equipment type reconstruction system does not have transient stability.

[0213] Preferably, the reconstructing of the system topology and control strategy based on the type of networked devices to obtain a transient stability analysis model of the system under large disturbances includes:

[0214] The system transient stability analysis model under large disturbance is:

[0215]

[0216] Where, ΔP1, ΔP2…ΔP i are defined as the transient unbalanced power of units 1, 2…i respectively; P in,1 、P in,2 …P in,i are defined as the port power of the i-th unit and do not include the virtual inertia part; P out,1 、P out,2 …P out,i They are defined as the power transmitted from the i-th unit to the grid;

[0217] The reconstruction system based on the networking device type is divided into different stages:

[0218] Before the fault disturbance (defined as time 0):

[0219] 0=P in,i BF -P out,i BF

[0220] Fault disturbance (0~t c ):

[0221] ΔP i F =P in,i F -P out,i F

[0222] After fault disturbance (t c back):

[0223] ΔP iPF =P in,i PF -P out,i PF

[0224] Where, P in，i BF is the port power of the i-th unit before the fault and does not include the virtual inertia part; P in，i F is the port power of the i-th unit during the fault and does not include the virtual inertia part; P in，i PF is the port power of the i-th unit after the fault and does not include the virtual inertia part; ΔP i F is the transient unbalanced power of the i-th unit during the fault; ΔP i PF is the transient unbalanced power of the i-th unit after the fault; P out，i BF is the power transmitted to the grid by the i-th unit before the fault; P out，i F is the power transmitted to the grid by the i-th unit during a fault; P out，i PF is the power transmitted to the grid by the i-th unit after the fault; BF, F and PF represent the power before, during and after the fault respectively; t c Indicates the time when the fault is cleared.

[0225] Preferably, obtaining the transient acceleration energy during the fault period based on the system transient stability analysis model includes:

[0226] When the sign of the virtual angular acceleration changes from negative to positive, it is defined as the existence of VAA SCP;

[0227] When there is no VAA SCP, the transient unbalanced energy of the i-th unit is:

[0228]

[0229] When VAA SCP exists, the sign change points are obtained as (δ F,1 , t F,1 ),(δ F,2 , t F,2 ),…,(δ F,k , t F,k ); where δ F,1 , δ F,2 …δ F,k are the virtual power angle positions corresponding to each VAA SCP during the fault period; t F,1 , t F,2 …t F,kare the fault time positions of each VAA SCP during the temporary fault period; δ c is the virtual power angle at the moment of fault clearing; k is the number of VAA SCPs during the fault period;

[0230]

[0231] Among them, W F1 、W F2 …W Fk are the transient unbalanced energy accumulated at each VAA SCP during the transient fault period;

[0232] When the transient energy W F,i Decrease to the set dead zone value W D There is no need to calculate the subsequent accumulated transient energy.

[0233] Preferably, when the sign of the virtual angular acceleration is negative for the first time, obtaining the first transient deceleration energy after the fault is cleared includes:

[0234] By t c After the fault is cleared, VAA SCP1 first exists, and (δ PF,1 , t PF,1 ), and then the first deceleration energy can be obtained:

[0235]

[0236] Among them, δ PF,1 is the virtual power angle position corresponding to the first VAA SCP after the fault is cleared; t PF,1 This is the fault time position corresponding to the first VAA SCP after the fault is cleared.

[0237] Preferably, judging whether the unit has the first-swing transient stability characteristic based on the first transient deceleration energy and the transient acceleration energy includes:

[0238] When the sum of the transient acceleration energy and the first transient deceleration energy of the unit is less than or equal to 0, the unit virtual power angle returns to the initial stable equilibrium point SEP0, and the unit has first-swing transient stability;

[0239] When the sum of the transient acceleration energy and the first transient deceleration energy of the unit is greater than 0, the unit virtual power angle cannot return to the initial stable equilibrium point SEP0, and the unit transient stability is uncertain.

[0240] Preferably, when the sign of the virtual angular acceleration is negative for the second time, obtaining the second transient deceleration energy after the fault is cleared includes:

[0241] By t cAfter the fault is cleared, VAA SCP2 exists for the second time, and (δ PF,2 , t PF,2) , obtain the second transient deceleration energy after the fault is cleared:

[0242]

[0243] Among them, δ PF,2 is the virtual power angle position corresponding to the second VAA SCP after the fault is cleared; t PF,2 This is the fault time position corresponding to the second VAA SCP after the fault is cleared.

[0244] Preferably, the determining whether the unit has periodic transient stability characteristics based on the first transient deceleration energy, the transient acceleration energy, and the second transient deceleration energy includes:

[0245] When the sum of the first transient deceleration energy, the transient acceleration energy and the second transient deceleration energy of the unit is less than or equal to 0, the virtual power angle of each unit returns to the periodic equilibrium point SEP1, and the unit has transient stability;

[0246] When the sum of the first transient deceleration energy, the transient acceleration energy and the second transient deceleration energy of the unit is greater than 0, the virtual power angle of each unit cannot return to the periodic equilibrium point SEP1, and the unit becomes transiently unstable.

[0247] An embodiment of the present invention provides a transient stability judgment system for a grid-type converter system, which corresponds to another embodiment of the present invention provides a transient stability judgment method for a grid-type converter system, and will not be described in detail here.

[0248] The present invention provides a computer-readable storage medium storing a computer program for executing a method for determining transient stability of a grid-type converter system.

[0249] The present invention provides an electronic device, comprising: a processor and a memory; wherein:

[0250] The memory is a memory for storing instructions executable by the processor;

[0251] The processor is used to read the executable instructions from the memory and execute the instructions to implement a transient stability judgment method for a grid-type converter system.

[0252] It will be understood by those skilled in the art that the embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take 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 may be implemented in various computer languages, for example, the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0253] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes 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 a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0254] These computer program instructions may 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, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0255] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0256] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0257] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

[0258] The invention has been described above with reference to a few embodiments. However, it is readily apparent to a person skilled in the art that other embodiments than the ones disclosed above are equally within the scope of the invention, as defined by the appended patent claims.

[0259] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / the [means, component, etc.]" are to be interpreted openly as referring to at least one instance of the means, component, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not necessarily need to be performed in the exact order disclosed, unless explicitly stated otherwise.

Claims

1. A method for determining transient stability of a grid-connected converter system, the method comprising: Reconstruct the system topology and control strategy based on the type of networked equipment to obtain the system transient stability analysis model under large disturbances; Based on the system transient stability analysis model, the transient acceleration energy during the fault period is obtained, including: When the sign of the virtual angular acceleration changes from negative to positive, it is defined as the existence of VAA SCP; When there is no VAA SCP, the transient unbalanced energy of the i-th unit is: When VAA SCP exists, the sign change points are obtained as (δ F,1 , t F,1 ),(δ F,2 , t F,2 ),…,(δ F,k , t F,k ); where δ F,1 , δ F,2 …δ F,k are the virtual power angle positions corresponding to each VAA SCP during the fault period; t F,1 , t F,2 …t F,k are the fault time positions of each VAA SCP during the temporary fault period; δ c is the virtual power angle at the time of fault clearing; k is the number of VAA SCPs during the fault period; ΔP i F is the transient unbalanced power of the i-th unit during the fault; t c Indicates the time when the fault is cleared; Among them, W F1 、W F2 …W Fk are the transient unbalanced energy accumulated at each VAA SCP during the transient fault period; When the transient energy W F,i Decrease to the set dead zone value W D When , there is no need to calculate the subsequent accumulated transient energy; Get the sign of the virtual angular acceleration at the moment of fault clearing; When the sign of the virtual angular acceleration is negative for the first time, obtaining the first transient deceleration energy after the fault is cleared includes: By t c After the fault is cleared, VAA SCP1 first exists, and (δ PF,1 , t PF,1 ), and then the first deceleration energy can be obtained: Among them, δ PF,1 is the virtual power angle position corresponding to the first VAASCP after the fault is cleared; t PF,1 is the fault time position corresponding to the first VAASCP after the fault is cleared; ΔP i PF is the transient unbalanced power of the i-th unit after the fault; Based on the first transient deceleration energy and the transient acceleration energy, determining whether the unit has first-swing transient stability characteristics; When the sign of the virtual angular acceleration is negative for the second time, obtaining the second transient deceleration energy after the fault is cleared; Based on the first transient deceleration energy, the transient acceleration energy, and the second transient deceleration energy, it is determined whether the unit has periodic transient stability characteristics.

2. The method according to claim 1 further comprises determining the transient stability of the multi-mechanism network device type reconstruction system, comprising: When the sum of the transient acceleration energy and the first transient deceleration energy of each unit is less than or equal to 0, the virtual power angle of each unit returns to the initial stable equilibrium point SEP0, and the multi-mechanism network type equipment type reconstruction system has transient stability; When each unit does not have the first transient deceleration energy or the sum of the transient acceleration energy and the first transient deceleration energy is greater than 0, the virtual power angle of each unit cannot return to the initial stable equilibrium point SEP0, and the transient stability of the multi-mechanism network type equipment type reconstruction system is uncertain; When the sum of the first transient deceleration energy of each unit, the transient acceleration energy and the second transient deceleration energy is less than or equal to 0, the virtual power angle of each unit returns to the initial stable equilibrium point SEP0, and the multi-mechanism network type equipment type reconstruction system has transient stability; When the sum of the first transient deceleration energy of each unit, the transient acceleration energy and the second transient deceleration energy is greater than 0, the virtual power angle of each unit cannot return to the initial stable equilibrium point SEP0, and the multi-mechanism network equipment type reconstruction system does not have transient stability.

3. The method according to claim 1, wherein the reconstructing the system topology and control strategy based on the type of networked devices to obtain a transient stability analysis model of the system under large disturbances comprises: The system transient stability analysis model under large disturbance is: Where, ΔP1, ΔP2…ΔP i are defined as the transient unbalanced power of units 1, 2…i respectively; P in,1 、P in,2 …P in,i are defined as the port power of the i-th unit and do not include the virtual inertia part; P out,1 、P out,2 …P out,i They are defined as the power transmitted from the i-th unit to the grid; The reconstruction system based on the networking device type is divided into different stages: Before the fault disturbance, it is defined as time 0: 0=P in,i BF -P out,i BF Fault disturbance 0~t c : ΔP i F =P in,i F -P out,i F After fault disturbance t c back: ΔP i PF =P in,i PF -P out,i PF Where, P in,i BF is the port power of the i-th unit before the fault and does not include the virtual inertia part; P in,i F is the port power of the i-th unit during the fault and does not include the virtual inertia part; P in,i PF is the port power of the i-th unit after the fault and does not include the virtual inertia part; ΔP i F is the transient unbalanced power of the i-th unit during the fault; ΔP i PF is the transient unbalanced power of the i-th unit after the fault; P out，i BF is the power transmitted to the grid by the i-th unit before the fault; P out，i F is the power transmitted to the grid by the i-th unit during a fault; P out，i PF is the power transmitted to the grid by the i-th unit after the fault; BF, F and PF represent the power before, during and after the fault respectively; t c Indicates the time when the fault is cleared.

4. The method according to claim 1, wherein judging whether the unit has first-swing transient stability characteristics based on the first transient deceleration energy and the transient acceleration energy comprises: When the sum of the transient acceleration energy and the first transient deceleration energy of the unit is less than or equal to 0, the unit virtual power angle returns to the initial stable equilibrium point SEP0, and the unit has first-swing transient stability; When the sum of the transient acceleration energy and the first transient deceleration energy of the unit is greater than 0, the unit virtual power angle cannot return to the initial stable equilibrium point SEP0, and the unit transient stability is uncertain.

5. The method according to claim 4, wherein when the sign of the virtual angular acceleration is negative for the second time, obtaining the second transient deceleration energy after the fault is cleared comprises: By t c After the fault is cleared, VAA SCP2 exists for the second time, and (δ PF,2 , t PF,2 ), obtain the second transient deceleration energy after the fault is cleared: Among them, δ PF,2 is the virtual power angle position corresponding to the second VAA SCP after the fault is cleared; t PF,2 This is the fault time position corresponding to the second VAA SCP after the fault is cleared.

6. The method according to claim 5, wherein judging whether the unit has periodic transient stability characteristics based on the first transient deceleration energy, the transient acceleration energy, and the second transient deceleration energy comprises: When the sum of the first transient deceleration energy, the transient acceleration energy and the second transient deceleration energy of the unit is less than or equal to 0, the virtual power angle of each unit returns to the periodic equilibrium point SEP1, and the unit has transient stability; When the sum of the first transient deceleration energy, the transient acceleration energy and the second transient deceleration energy of the unit is greater than 0, the virtual power angle of each unit cannot return to the periodic equilibrium point SEP1, and the unit becomes transiently unstable.

7. A transient stability determination system for a grid-type converter system, comprising: The initial unit is used to reconstruct the system topology and control strategy based on the type of networked equipment and obtain the transient stability analysis model of the system under large disturbances; An acquisition unit, configured to acquire transient acceleration energy during a fault period based on the system transient stability analysis model, comprising: When the sign of the virtual angular acceleration changes from negative to positive, it is defined as the existence of VAA SCP; When there is no VAA SCP, the transient unbalanced energy of the i-th unit is: When VAA SCP exists, the sign change points are obtained as (δ F,1 , t F,1 ),(δ F,2 , t F,2 ),…,(δ F,k , t F,k ); where δ F,1 , δ F,2 …δ F,k are the virtual power angle positions corresponding to each VAA SCP during the fault period; t F,1 , t F,2 …t F,k are the fault time positions of each VAA SCP during the temporary fault period; δ c is the virtual power angle at the time of fault clearing; k is the number of VAA SCPs during the fault period; ΔP i F is the transient unbalanced power of the i-th unit during the fault; t c Indicates the time when the fault is cleared; Among them, W F1 、W F2 …W Fk are the transient unbalanced energy accumulated at each VAA SCP during the transient fault period; When the transient energy W F,i Decrease to the set dead zone value W D When , there is no need to calculate the subsequent accumulated transient energy; Obtaining the sign of the virtual angular acceleration at the time of fault clearing; when the sign of the virtual angular acceleration is negative for the first time, obtaining the first transient deceleration energy after the fault clearing, including: By t c After the fault is cleared, VAA SCP1 first exists, and (δ PF,1 , t PF,1 ), and then the first deceleration energy can be obtained: Among them, δ PF,1 is the virtual power angle position corresponding to the first VAA SCP after the fault is cleared; t PF,1 is the fault time position corresponding to the first VAASCP after the fault is cleared; ΔP i PF is the transient unbalanced power of the i-th unit after the fault; Based on the first transient deceleration energy and the transient acceleration energy, determining whether the unit has the first swing transient stability characteristic; when the sign of the virtual angular acceleration is negative for the second time, obtaining the second transient deceleration energy after the fault is cleared; The result unit is used to determine whether the unit has periodic transient stability characteristics based on the first transient deceleration energy, the transient acceleration energy and the second transient deceleration energy.

8. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and the computer program is used to execute the method according to any one of claims 1 to 6.

9. An electronic device, characterized in that: The electronic device includes: a processor and a memory; wherein, The memory is a memory for storing instructions executable by the processor; The processor is configured to read the executable instructions from the memory and execute the instructions to implement the method according to any one of claims 1 to 6.

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