Transient synchronous stability evaluation method and system for network construction type power generation equipment

Abstract

The invention discloses a method and system for evaluating transient synchronous stability of network construction type power generation equipment, and the method comprises the steps: obtaining main circuit parameters and control parameters of the network construction type power generation equipment, and constructing a transient equivalent model of the network construction type power generation equipment; according to the transient equivalent model of the system, constructing a Lyapunov energy function V lambda of the network-forming power generation equipment; determining an initial state point of the final stage of the network-forming type power generation equipment according to whether the fault is cleared or not; substituting the initial state point of the final stage into the Lyapunov energy function V lambda, and calculating to obtain the total energy V of the network construction type power generation equipment in the final stage; judging whether a balance point exists in the final stage or not according to the transient equivalent model of the grid-forming type power generation equipment; if the total energy V is smaller than the critical energy Vcr, calculating the critical energy Vcr of the final stage, if the total energy V is smaller than the critical energy Vcr, judging that transient synchronization is stable, and otherwise, judging that synchronization is unstable; and if not, determining that synchronization is unstable. According to the method, the problem of difficulty in frame-by-frame modeling in a complex switching process is solved.

Description

Technical Field

[0001] This invention relates to new energy power generation control technology, and in particular to a method and system for evaluating the transient synchronization stability of grid-connected power generation equipment in scenarios with frequent switching. Background Technology

[0002] Grid-connected power generation equipment, as a core component of new energy grid-connected systems, possesses the characteristic of actively supporting grid voltage and frequency, and is widely used in distributed generation, microgrids, and other fields. Current-limiting strategies based on virtual impedance are a key technology for fault ride-through in grid-connected power generation equipment. These strategies can maintain grid-connected operation during faults, preserving active support capabilities while limiting the fault current amplitude.

[0003] Virtual impedance control exhibits control switching characteristics during transient processes, and its switching timing and triggering conditions significantly alter the transient behavior and stability characteristics of the system. Traditional transient synchronization stability assessment methods, such as the equal-area method, rely on the assumption of "constant control parameters" and cannot cope with the abrupt changes in the system model caused by control switching; the phase trajectory method depends on the continuity of the state space and is difficult to handle state jumps caused by switching, both having certain limitations. Therefore, developing a transient synchronization stability assessment method that can accurately adapt to frequent control switching conditions has become crucial for ensuring the safe and stable operation of grid-connected power generation equipment. Thus, how to conduct transient synchronization stability assessments of grid-connected power generation equipment under frequent control switching conditions is an urgent technical problem to be solved. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a transient synchronization stability assessment method for grid-type power generation equipment, which addresses the shortcomings of the existing technology by using an energy boundary threshold to assess the transient synchronization stability of grid-type equipment under control switching action, thereby avoiding frame-by-frame modeling of complex switching processes.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for evaluating the transient synchronization stability of grid-connected power generation equipment, comprising the following steps:

[0006] S1. Obtain the main circuit parameters and control parameters of the grid-type power generation equipment, and construct the transient equivalent model of the grid-type power generation equipment;

[0007] S2. Based on the system transient equivalent model, construct the Lyapunov energy function V for grid-connected power generation equipment. λ ;

[0008] S3. Determine the final stage based on whether the fault has been cleared, and determine the initial state point of the final stage of the grid-connected power generation equipment based on whether the fault has been cleared.

[0009] S4. Substitute the initial state point of the final stage into the Lyapunov energy function V.λ The total energy V of the grid-type power generation equipment in the final stage is calculated.

[0010] S5. Determine whether there is an equilibrium point in the final stage based on the transient equivalent model of the grid-connected power generation equipment; if so, calculate the critical energy V of the final stage. cr If the total energy V is less than the critical energy V cr If the condition is met, it is determined to be transiently synchronous and stable; otherwise, it is determined to be synchronously unstable.

[0011] In this invention, if the fault is cleared, the final stage is determined to be a normal state, the grid voltage is restored to the rated value, and the virtual impedance control is deactivated; otherwise, the final stage is determined to be a fault state, the grid voltage is maintained at the fault level, and the virtual impedance is always activated.

[0012] This invention assesses system stability by comparing the energy V in the "final" stage with the critical energy Vcr of the grid-connected power generation equipment, regardless of the dynamic path the system undergoes during control switching (e.g., virtual impedance step input, parameter gradual adjustment). This avoids frame-by-frame modeling of complex switching processes. Specifically, if the energy V in the "final" stage is less than the critical energy Vcr, it indicates that the system has not exceeded the critical stability boundary and can recover to a stable state. Conversely, if the energy V in the final stage is greater than the critical energy Vcr, it indicates that the system has exceeded the critical stability boundary and transient synchronous instability has occurred. This method incorporates discontinuous state transitions caused by multi-stage control switching into the energy conversion framework through the global energy conservation property. Compared to the dependence on state continuity by traditional equal-area methods, phase trajectory methods, and inverse trajectory methods, this criterion achieves transient synchronous stability assessment of grid-connected equipment under control switching through energy boundary thresholds.

[0013] The specific implementation process for determining whether a fault has been cleared includes: If U g =U N If the power grid is determined to be in normal operating condition, the fault is cleared; if U g N The power grid is determined to be in a fault condition, and the fault has not been cleared; among them, U N U is the rated voltage of the power grid. g This is the grid voltage.

[0014] The transient equivalent model of grid-connected power generation equipment is expressed as follows:

[0015]

[0016] Where J represents the inertia of the grid-connected power generation equipment. For the angular frequency deviation of grid-connected power generation equipment, For grid-type power generation equipment angular frequency, P is the rated angular frequency.​ref P represents the reference power of the grid-connected power generation equipment, and P represents the output active power of the grid-connected power generation equipment. Let E be the power angle of the grid-connected power generation equipment, E be the output voltage of the grid-connected power generation equipment, D be the damping, K be the reactive power loop droop system, and Q be the power angle of the grid-connected power generation equipment. ref Q is the reactive power reference value, and D is the output reactive power. q This is a reactive power droop system, where E0 is the rated voltage. , These are the first and second derivatives of δ, respectively. It is the first derivative of E.

[0017] Lyapunov energy function V for grid-connected power generation equipment λ Represented as:

[0018]

[0019] Among them, X g For line reactance, R g Z represents the line resistance. g For line impedance, δ0 is the steady-state operating point x before the fault. u1 The work angle, J is the inertia of the grid-type power generation equipment. Let D be the angular frequency deviation of the grid-connected power generation equipment, and D be the damping. q For a reactive power droop system, E is the output voltage of the grid-connected power generation equipment, and J is the inertia of the grid-connected power generation equipment.

[0020] The specific implementation process of step S3 includes: if the fault is not cleared, the initial state point of the final stage is the steady-state operating point x before the fault. u1 If the fault is cleared, the initial state point of the final stage is the operating point x at the time the fault is cleared. u2 .

[0021] The total energy V of the final stage grid-connected power generation equipment is expressed as:

[0022]

[0023] Where, δ u Let E be the initial point work angle. u Let R be the voltage at the initial fault point, 0 ≤ λ ≤ 1. g Z represents the line resistance. g Q is the line impedance. ref D is the reactive power reference value. q For a reactive power droop system, E0 is the rated voltage, and δ0 is the steady-state operating point before the fault. u1 The work angle is J, where J is the inertia of the grid-type power generation equipment.

[0024] The critical energy V of the final stage systemcr The energy corresponding to the unstable equilibrium point of the system in the final stage is expressed as:

[0025]

[0026] in, Indicates the work angle at an unstable equilibrium point. R represents the voltage at the unstable equilibrium point. g Z represents the line resistance. g Q is the line impedance. ref D is the reactive power reference value. q For a reactive power droop system, E0 is the rated voltage, and δ0 is the steady-state operating point before the fault. u1 The work angle is J, where J is the inertia of the grid-type power generation equipment.

[0027] The process of determining whether an equilibrium point exists includes: comparing the reference power P of the grid-connected power generation equipment. ref The magnitude of the output active power P, if P ref If the equilibrium point is greater than P, then the equilibrium point does not exist; otherwise, it does exist.

[0028] As an inventive concept, the present invention also provides a transient synchronization stability assessment system for grid-connected power generation equipment, including a memory, a processor, and a computer program stored in the memory; the processor executes the computer program to implement the steps of the above method.

[0029] As an inventive concept, the present invention also provides a computer-readable storage medium having a computer program / instructions stored thereon; when the computer program / instructions are executed by a processor, they implement the steps of the above-described method.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention realizes the evaluation of transient synchronization stability of grid-type power generation equipment under frequent switching scenarios, and solves the problem of difficult frame-by-frame modeling in complex switching processes. Attached Figure Description

[0031] Figure 1 This is a procedure for determining the transient synchronization stability applicable to control switching;

[0032] Figure 2 The control switching behavior for different fault conditions throughout the transient process; (a) fault clearing condition, (b) fault continuation condition;

[0033] Figure 3 The results are: (a) Estimation of the stable domain under continuous fault conditions and simulation results of Case 1; (b) State trajectory of the "final" stage under a fault drop depth of 0.6 pu;

[0034] Figure 4The stability domain estimation for fault clearing condition (Td=0) and the simulation results for Case 2 are shown; (a) a two-dimensional cross-sectional view of the stability domain on the E-δ plane, and (b) the simulation results for Case 2.

[0035] Figure 5 The results are: (a) Stability domain estimation (Td=0.5s) under fault clearing condition and simulation results for Case 3; (b) Stability domain estimation (Td=0.5s) under fault clearing condition and simulation results for Case 3. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] Figure 1 This is a transient synchronization stability determination process applicable to control switching. First, the main circuit parameters and control parameters of the grid-connected power generation equipment are input, and a transient equivalent model and energy function of the system are constructed. The equivalent state equation of the grid-connected power generation equipment can be expressed as:

[0039]

[0040] In the formula, δ is the power angle between the grid-connected power generation equipment and the power grid. For the output angular frequency, P ref and Q ref For reference power, E0 is the rated voltage, J and D are the active loop inertia coefficient and damping coefficient, respectively, and D... q K represents the reactive power loop droop factor and integral factor, respectively. Based on power transmission theory, the actual output power of grid-connected equipment can be expressed as:

[0041]

[0042] In the formula, , , , , , During the transient process, if the virtual impedance is activated, it can be considered as being in series with the line impedance. The state equation still follows equation (1), the difference being the impedance Z. g By Z s replace:

[0043]

[0044] Therefore, the system state equations have a unified mathematical expression regardless of whether the virtual impedance is activated.

[0045] Multiply both sides of the second equation (1) by ∆ω, and then integrate over time t:

[0046]

[0047] because , The energy conservation equation for grid-connected power generation equipment can be derived as follows:

[0048]

[0049] in,

[0050]

[0051] Equation (5) and the term const in the following text both represent arbitrary constants. When considering power coupling between the active and reactive power loops, δ, Δω, and E are all independent variables. Based on the integral transform, equation... It can be converted into:

[0052]

[0053] because , , ,Mode It can be further simplified to:

[0054]

[0055] According to equation (1), we can obtain:

[0056]

[0057] The formula Substitution ,Mode This can be further deduced as follows:

[0058]

[0059] The formula Substituting into equation (5), the energy conservation equation can be derived as follows:

[0060]

[0061] Among them, V k and V p These are the equivalent kinetic energy and equivalent potential energy of the grid-connected power generation equipment, respectively, and can be expressed as:

[0062]

[0063]

[0064] Due to the formula The voltage integral term cannot be directly integrated, so an additional term is introduced to cancel it out. Without considering energy dissipation caused by damping, the Lyapunov function V can be constructed as:

[0065]

[0066] Pair Differentiate:

[0067]

[0068] The formula Substitution :

[0069]

[0070] Clearly, for grid-connected power generation equipment, both K and D are positive, and dV / dt is always negative. However, the damping dissipation effect of grid-connected power generation equipment is not reflected in the energy function V, which makes the stability region conservative. When the system damping is large, the conservatism of the stability region plotted based on the energy function V and the error in the prediction of transient synchronous stability will further increase. To reduce the degree of conservatism and error, the damping dissipation effect should be reflected in the energy function, and the equation should be... The energy dissipation caused by moderate damping is converted into a path-independent energy term.

[0071] Δω is the derivative of δ, and Δω is also the derivative of Δδ. Δδ = δ - δ0, where δ0 is the initial work angle, and V is the damped dissipated energy. d This can be deduced as:

[0072]

[0073] According to the integral transform, equation It can be rewritten as:

[0074]

[0075] Substituting the state equation (1) into the equation The second item on the right:

[0076]

[0077] Combined with formula Damping dissipation energy V d Further transformed into:

[0078]

[0079] In the formula, .

[0080] Due to the formula The equation contains a path-dependent integral term. By introducing a parameter λ to scale the damping dissipation energy, the damping dissipation energy can be approximately estimated as follows:

[0081]

[0082] In summary, the Lyapunov energy function V, taking into account power coupling and damping dissipation, λ It can be constructed as:

[0083]

[0084] The formula ,Mode Japanese style Substitution Lyapunov energy function V λ It can be represented as:

[0085]

[0086] During the transient process of network-type equipment, the "final" stage and critical energy of the same system are different depending on whether the fault is cleared. Figure 2 The control switching behavior under different fault conditions throughout the transient process is presented. Specifically, if the focus of the study is whether the system can return to stability after fault clearance (i.e., fault clearance condition), then the "final" stage is the "normal state," such as... Figure 2As shown in (a) above. At this point, the grid voltage returns to its rated value, and the virtual impedance is forcibly disconnected. If the focus is on whether the system can maintain stable operation during the fault (i.e., the fault-continuous operating condition), then the final stage is the "fault" stage, as shown in (a). Figure 2 As shown in (b) above. After determining the final state, the total energy of the system in the "final" stage is calculated based on the Lyapunov energy function constructed above.

[0087] This invention embodiment quantifies the initial energy V and critical energy V of the system in the "final" stage. cr The relative relationship is used to assess the transient synchronization stability of grid-connected power generation equipment under control switching scenarios. Next, the unstable equilibrium point method is used to determine the critical energy, i.e., the unstable equilibrium point x... u Energy value V λ (x u ) as the critical energy V cr This establishes the intrinsic connection between the energy boundary and the dynamic characteristics of the system. The physical basis for this lies in the unstable equilibrium point x. u The saddle point on the potential energy surface represents the critical state separating the stable and unstable regions of the system. For the unstable equilibrium point x... u The system state no longer changes with time, satisfying equation (24).

[0088] (twenty four)

[0089] Substituting equation (24) into equation (1):

[0090] (25)

[0091] Solving the system of equations (25), we obtain the unstable equilibrium point x. u =[δ u , Δω u E u Then, x u Substitution The critical energy V can be calculated. cr As shown in equation (27).

[0092] (26)

[0093] To achieve quantitative assessment of the transient synchronization stability of network-type equipment, the stability margin η can be defined as the critical energy V. cr The difference between the total energy V0 at the initial moment of the "final" stage, i.e.:

[0094] (27)

[0095] According to an embodiment of the present invention, if the total energy V0 of the system at the initial moment of the "final" stage is less than the critical energy V0 of the system...cr If the initial point is within the stability region Ω and the stability margin η is positive, it indicates that the system can maintain transient stability. Conversely, if the total energy V0 of the system at the initial moment of the "final" stage is greater than the critical energy V0, then the system is transiently stable. cr If the initial point is outside the stability region, the stability margin η is negative, and the system experiences transient synchronous instability. Furthermore, a larger stability margin indicates a higher degree of system stability and stronger disturbance rejection capability. Therefore, the transient stability of network-type equipment can be determined by the location of the initial point, the sign of the stability margin, or the relationship between the system's initial energy V0 and critical energy V0. cr The size relationship can be quantitatively assessed.

[0096] Next, we will verify the accuracy of the transient synchronization stability criterion and the stability domain estimation. We will design three sets of comparative cases for two transient operating conditions: fault persistence and fault clearing.

[0097] (1) In Case 1, a voltage drop occurs at t=3s with a depth of 0.6 pu. The fault is not cleared. The "final" stage is the "fault" stage. x0=[δ(0+), ∆ω(0+), E(0+)] is the initial point of the "final" stage. sf This is the stable equilibrium point in the "final" stage.

[0098] Figure 3 Figure (a) shows the cross-section of the stability region in the E-δ plane (Δω is fixed at Δω(0+)). Since the fault is not cleared, the "final" stage is the fault stage, with its initial time being the end of the normal stage; therefore, Δω(0+) = 0. Compared to the stability region without considering damping effects, damping increases the system's stability region and reduces the conservatism of the stability assessment. To verify the accuracy of the stability region estimation, Figure 3 Figure (a) shows the state trajectory of the "final" stage at a fault drop depth of 0.6 pu. The initial point x0 of the trajectory is located within the orange-filled area but outside the blue-filled area. This indicates that, neglecting the damping effect, the conventional energy function V predicts the system to be unstable; while the energy function V considering damping dissipation proposed in this embodiment of the invention... λ The system is predicted to be stable. The state trajectory shows that after the fault, the system reaches a new equilibrium point x. sf Stable operation verifies the Lyapunov function V proposed in this paper. λ The accuracy of the transient synchronization stability was assessed. Furthermore, by calculating the initial energy at the initial point x0, the stability margin η was found to be positive at 1773, further indicating that the system is stable. Figure 3 (b) shows the simulation results for Case 1. At the moment of the fault, the virtual impedance control is activated, and the control switches. After the fault, the system stabilizes at a new equilibrium point x. sf It operates synchronously with the power grid, and the simulation results are consistent with the stability domain analysis results.

[0099] (2) In Case 2, a voltage drop occurs at t=3s with a depth of 0.8pu and a transition time T d =0s, meaning the virtual impedance control is immediately cleared the moment the fault is cleared. At this point, the "final" stage is the "normal" stage.

[0100] Figure 4 Figure (a) shows a two-dimensional cross-sectional view of the stability region on the E-δ plane. To verify the accuracy of the stability region estimation, the fault duration was gradually increased, and the stability of the system under different fault durations and the positional relationship between the initial point and the stability region in the "final" stage were observed. Figure 4 (a) shows the state trajectories of the system in the "final" stage when the fault duration is 0.17s and 0.18s. Figure 4 As shown in (a), when FD = 0.17s, the initial point x1 of the trajectory is within the stable region, and the system maintains synchronous and stable operation. Conversely, when FD = 0.18s, the initial point x2 is outside the stable region, the state trajectory diverges, and the system experiences transient synchronous instability. Therefore, by identifying whether the initial point of the "final" stage is within or outside the stable region, the transient synchronous stability of the network-type equipment after fault clearance can be accurately predicted. Furthermore, the initial point x1 is within the orange-filled region but outside the blue-filled region. This indicates that the energy function V without damping dissipation causes an incorrect prediction of transient synchronous stability under fault clearance conditions. Therefore, constructing an accurate Lyapunov function is crucial for assessing transient synchronous stability.

[0101] Figure 4 (b) shows the simulation results for Case 2. At the moment of the fault, the virtual impedance control is activated, and the control switches; after the fault is cleared, the virtual impedance control is deactivated, and the control switches again. When the fault duration is 0.17s, the grid-connected power generation equipment can maintain synchronization with the grid, and the system stabilizes at a new equilibrium point; when the fault duration increases to 0.18s, the grid-connected power generation equipment loses synchronization with the grid. The simulation results are consistent with the stability domain analysis results. Furthermore, the critical energy V under the fault-clearing condition... cr The calculated value is 4100. When FD = 0.17s, the stability margin η at the initial point x1 is calculated to be 2051. When the fault clearing time increases to 0.18s, the stability margin η at the initial point x2 is -1382, the initial energy exceeds the critical energy, and the system becomes unstable. Therefore, the transient stability of grid-connected power generation equipment can be determined by the location of the initial point in the "final" stage, the sign of the stability margin, or the relationship between the total system energy V and the critical energy V. cr The size relationship enables accurate quantitative assessment of stability.

[0102] (3) In Case 3, the operating conditions and fault depth are the same as in Case (2), and the transition time T d=0.5s, meaning the virtual impedance is forcibly cut off 0.5 seconds after the fault is cleared. During the transition time, the virtual impedance control will frequently switch due to the fluctuation of the output current near the rated value. According to formula (22), the stability region estimate for Case 3 is as follows: Figure 5 As shown in (a) of the diagram. Although T d The situation has changed, but the "final" stage remains the same. The stable region can still be estimated using the parameters of the "normal" stage, so the stable region is the same as in Case 2. Figure 5 Figure (a) shows the state trajectories for fault durations of 0.09 s and 0.10 s. From... Figure 5 As can be seen in (a), although the difference in fault duration is only 0.01 seconds, the initial position of the trajectory differs greatly. This difference evolves and accumulates after a transition time of 0.5 seconds. Figure 5 As shown in (a), when the fault duration is 0.09 s, the initial point x1 of the trajectory is within the stable region, thus predicting that the system will remain transiently synchronous and stable. However, when the fault duration increases to 0.10 s, the initial point x2 is outside the stable region, and the system is predicted to be unstable.

[0103] To visually represent the control switching effect, the simulation results for the entire transient period are as follows: Figure 5 As shown in (b) of the diagram. From Figure 5 As shown in (b), during the "post-fault" phase, the virtual impedance is frequently switched on and off because the output current fluctuates around its rated value within this 0.5s period. The virtual impedance is allowed to activate to better limit the overcurrent caused by fault clearing. The figure shows that the switching signals at FD=0.09s and FD=0.10s are significantly different. Nevertheless, the transient synchronization stability of the grid-connected power generation equipment can still be predicted by the relationship between the initial point and the stability domain position in the "final" phase. This demonstrates the advantage of the energy function method in switching systems and verifies the effectiveness of the stability criterion proposed in this embodiment of the invention in controlled switching scenarios.

[0104] Example 2

[0105] Embodiment 2 of the present invention provides a terminal device corresponding to Embodiment 1 above. The terminal device can be a processing device for a client, such as a mobile phone, a laptop, a tablet computer, a desktop computer, etc., to execute the method of the above embodiments.

[0106] The terminal device in this embodiment includes a memory, a processor, and a computer program stored in the memory; the processor executes the computer program in the memory to implement the steps of the method in Embodiment 1 described above.

[0107] In some implementations, the memory may be high-speed random access memory (RAM), and may also include non-volatile memory, such as at least one disk storage device.

[0108] In other implementations, the processor can be any type of general-purpose processor, such as a central processing unit (CPU) or a digital signal processor (DSP), and there is no limitation here.

[0109] Example 3

[0110] Embodiment 3 of the present invention provides a computer-readable storage medium corresponding to Embodiment 1 above, on which a computer program / instructions are stored. When the computer program / instructions are executed by a processor, they implement the steps of the method of Embodiment 1 above.

[0111] A computer-readable storage medium can be a tangible device that holds and stores instructions for use by an instruction execution device. A computer-readable storage medium can be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any combination thereof.

[0112] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can 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 this application can be implemented in various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0113] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations 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, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0114] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0115] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0116] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method for evaluating the transient synchronization stability of grid-connected power generation equipment, characterized in that, Includes the following steps: S1. Obtain the main circuit parameters and control parameters of the grid-type power generation equipment, and construct the transient equivalent model of the grid-type power generation equipment; S2. Based on the system transient equivalent model, construct the Lyapunov energy function V for grid-connected power generation equipment. λ ; S3. Determine the final stage based on whether the fault has been cleared, and determine the initial state point of the final stage of the grid-connected power generation equipment based on whether the fault has been cleared. S4. Substitute the initial state point of the final stage into the Lyapunov energy function V. λ The total energy V of the grid-type power generation equipment in the final stage is calculated. S5. Determine whether there is an equilibrium point in the final stage based on the transient equivalent model of the grid-connected power generation equipment; if so, calculate the critical energy V of the final stage. cr If the total energy V is less than the critical energy V cr If the condition is met, it is determined to be transiently synchronous and stable; otherwise, it is determined to be synchronously unstable.

2. The method for evaluating the transient synchronization stability of grid-connected power generation equipment according to claim 1, characterized in that, The specific implementation process for determining whether a fault has been cleared includes: if V g =V N If the power grid is determined to be in normal operating condition, the fault is cleared; if V g <V N The power grid is determined to be in a fault condition, and the fault has not been cleared; among which, V N The rated voltage of the power grid, V g This is the grid voltage.

3. The method for evaluating the transient synchronization stability of grid-connected power generation equipment according to claim 1, characterized in that, The transient equivalent model of grid-connected power generation equipment is expressed as follows: ； Where J represents the inertia of the grid-connected power generation equipment. For the angular frequency deviation of grid-connected power generation equipment, For grid-type power generation equipment angular frequency, P is the rated angular frequency. ref P is the reference power of the grid-connected power generation equipment, δ is the power angle of the grid-connected power generation equipment, E is the output voltage of the grid-connected power generation equipment, D is the damping, K is the reactive power loop droop system, and Q is the reference power of the grid-connected power generation equipment. ref Q is the reactive power reference value, and D is the output reactive power. q This is a reactive power droop system, where E0 is the rated voltage. , These are the first and second derivatives of δ, respectively. It is the first derivative of E.

4. The method for evaluating the transient synchronization stability of grid-connected power generation equipment according to claim 1, characterized in that, Lyapunov energy function V for grid-connected power generation equipment λ Represented as: ； Among them, X g For line reactance, R g Z represents the line resistance. g For line impedance, δ0 is the steady-state operating point x before the fault. u1 The work angle is J, where J is the inertia of the grid-type power generation equipment. Let D be the angular frequency deviation of the grid-connected power generation equipment, and D be the damping. q For a reactive power droop system, E is the output voltage of the grid-connected power generation equipment, J is the inertia of the grid-connected power generation equipment, and V... g This is the grid voltage.

5. The method for evaluating the transient synchronization stability of grid-connected power generation equipment according to claim 1, characterized in that, The specific implementation process of step S3 includes: if the fault is not cleared, the initial state point of the final stage is the steady-state operating point x before the fault. u1 If the fault is cleared, the initial state point of the final stage is the operating point x at the time the fault is cleared. u2 .

6. The method for evaluating the transient synchronization stability of grid-connected power generation equipment according to claim 1, characterized in that, The total energy V of the final stage grid-connected power generation equipment is expressed as: ； Where, δ u Let E be the initial point work angle. u The initial voltage of the fault is given by R, where 0 ≤ λ ≤ 1. g Z represents the line resistance. g Q is the line impedance. ref D is the reactive power reference value. q For a reactive power droop system, E0 is the rated voltage, and δ0 is the steady-state operating point before the fault. u1 The work angle, J is the inertia of the grid-connected power generation equipment, V g This is the grid voltage.

7. The method for evaluating the transient synchronization stability of grid-connected power generation equipment according to claim 1, characterized in that, The critical energy V of the final stage system cr The energy corresponding to the unstable equilibrium point of the system in the final stage is expressed as: ； in, Indicates the work angle at an unstable equilibrium point. R represents the unstable equilibrium point voltage. g Z represents the line resistance. g Q is the line impedance. ref D is the reactive power reference value. q For a reactive power droop system, E0 is the rated voltage, and δ0 is the steady-state operating point before the fault. u1 The work angle, J is the inertia of the grid-connected power generation equipment, V g The voltage is the grid voltage. According to claim 1, the transient synchronization stability assessment method for grid-connected power generation equipment is characterized in that the process of determining whether an equilibrium point exists includes: comparing the reference power P of the grid-connected power generation equipment. ref The magnitude of the output active power P, if P ref If the equilibrium point is greater than P, then the equilibrium point does not exist; otherwise, it does exist.

8. A transient synchronization stability assessment system for grid-connected power generation equipment, comprising a memory, a processor, and a computer program stored in the memory; characterized in that, The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 8.

9. A computer-readable storage medium having a computer program / instructions stored thereon; characterized in that, When the computer program / instructions are executed by the processor, they implement the steps of the method according to any one of claims 1 to 8.

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