Method and system for judging power angle instability of synchronous machine under new energy repeated low penetration condition

Abstract

The invention discloses a method and a system for judging power angle instability of a synchronous machine under a new energy repeated low penetration condition, and belongs to the technical field of safety and stability analysis and control of a large power grid. The method comprises the following steps: establishing an equivalent dynamic model of a new energy station and a power grid under a new energy repeated low-pass condition; according to the equivalent dynamic model, after a new energy power coupling item is added for the low-voltage crossing and fault recovery stage of the new energy station, an energy function is established, and the power angle energy of the synchronous machine is calculated according to the energy function; and substituting the power angle energy of the synchronous machine into a preset criterion, and carrying out judgment on the power angle instability of the synchronous machine under the condition of repeated low penetration of new energy. According to the method, through the equivalent dynamic model and the energy function, energy accumulation in each low-pass period and energy dissipation in a recovery stage can be subjected to explicit accumulation, energy quantitative description of multiple disturbance accumulation effects is formed, and stability judgment is given through a preset criterion.

Description

Technical Field

[0001] This invention relates to the field of power grid safety and stability analysis and control technology, and more specifically, to a method and system for determining the instability of the power angle of a synchronous machine under repeated low-voltage power surges from new energy sources. Background Technology

[0002] With the rapid development of high-proportion renewable energy grid connection and DC transmission technology, modern power systems are gradually evolving from traditional grids dominated by synchronous generators to multi-energy complementary AC / DC hybrid systems where wind power, photovoltaic and other power electronic interface power sources operate in coordination with conventional units. On the one hand, synchronous generators, relying on their electromechanical coupling characteristics, have a clear inertial response and primary and secondary regulation capabilities. Their power angle stability analysis has long been based on the equal area method, static stability criteria, and transient stability calculation framework for single faults. On the other hand, large-scale renewable energy units are connected to the grid through converters, and their output characteristics are determined by the control system.

[0003] In power systems with a high proportion of renewable energy sources, renewable energy units are generally equipped with low-voltage ride-through (LVRT) capabilities to meet grid connection standards. During voltage dips, they maintain grid connection through reactive power support, power limiting, and protective actions. However, due to grid voltage fluctuations and frequent faults, renewable energy power plants experience repeated LVRTs, triggering their LVRT control, power regulation, and protection actions multiple times, resulting in strong pulsations and abrupt changes in the equivalent electromagnetic power output. This periodic excitation of the power angle and electromagnetic power caused by repeated LVRTs directly affects the rotor motion equations of the synchronous generator, easily disrupting the original energy balance between mechanical input and electromagnetic output, inducing continuous divergence of the power angle and its evolution into synchronous instability. Summary of the Invention

[0004] To address the above problems, this invention proposes a method for determining the power angle instability of a synchronous machine under repeated low-voltage power surges from new energy sources, comprising:

[0005] Establish an equivalent dynamic model of new energy power plants and power grid under repeated low-voltage conditions;

[0006] Based on the equivalent dynamic model, for the low-voltage transmission and fault recovery phases of new energy power stations, after adding the new energy power coupling term, an energy function is established, and the power angle energy of the synchronous machine is calculated based on the energy function.

[0007] The power angle energy of the synchronizing machine is used as a preset criterion to determine the instability of the synchronizing machine's power angle under repeated low-voltage conditions of new energy sources.

[0008] Alternatively, the energy function can be expressed as follows:

[0009] V σ (δ,ω)=V(δ,ω)+Ψ σ (ΔP,ΔQ)

[0010] Among them, V σ (δ,ω) is the low-power-angle energy function of the synchronous machine, V(δ,ω) is the energy function during normal operation, and Ψ σ The power coupling term of the renewable energy power station is (ΔP,ΔQ), where ΔP and ΔQ are the power decreases in active and reactive power of the renewable energy power station, respectively.

[0011] Optionally, the preset criterion is: V0(δ,ω)>E cr

[0012] Where V0(δ,ω) is the power angle energy of the synchronous machine, and E cr It is the critical energy;

[0013] Optional, critical energy E cr The calculation formula is as follows:

[0014]

[0015] Where M is the inertia constant of the synchronous machine, For the synchronous machine speed, P1, P M δ1 represents the electromagnetic and mechanical power during the fault period, respectively, and δ2 represents the power angle of the synchronous machine when there is no fault.

[0016] Optionally, the criteria for determining the power angle instability of the synchronous motor under repeated low-voltage conditions of new energy sources include:

[0017] When V0(δ,ω)>E cr At that time, the synchronous motor power angle became unstable under repeated low-voltage conditions of the new energy source.

[0018] Furthermore, this invention also proposes a system for determining the power angle instability of a synchronous machine under repeated low-voltage power surges from new energy sources, comprising:

[0019] The modeling unit is used to establish an equivalent dynamic model of the renewable energy power station and the power grid under the condition of repeated low-voltage ride-through of renewable energy sources.

[0020] The calculation unit is used to establish an energy function based on the equivalent dynamic model, for the low-voltage transmission and fault recovery phases of the new energy power station, after adding the new energy power coupling term, and to calculate the power angle energy of the synchronous machine based on the energy function.

[0021] The discrimination unit is used to input the power angle energy of the synchronizing machine into a preset criterion to discriminate the power angle instability of the synchronizing machine under repeated low-voltage conditions of new energy sources.

[0022] Alternatively, the energy function can be expressed as follows:

[0023] V σ (δ,ω)=V(δ,ω)+Ψ σ(ΔP,ΔQ)

[0024] Among them, V σ (δ,ω) represents the power angle energy function of the synchronizer during low-voltage operation, V(δ,ω) represents the power angle energy function in normal mode, and Ψ σ (ΔP,ΔQ) is the power coupling term of the new energy source, where ΔP and ΔQ are the power decreases of the active and reactive power of the new energy power station, respectively.

[0025] Optionally, the preset criterion is: V0(δ,ω)>E cr

[0026] Where V0(δ,ω) is the power angle energy of the synchronous machine, and E cr It is the critical energy;

[0027] Optional, critical energy E cr The calculation formula is as follows:

[0028]

[0029] Where M is the inertia constant of the synchronous machine, For the synchronous machine speed, P1, P M δ1 represents the electromagnetic and mechanical power during the fault period, respectively, and δ2 represents the synchronous power angle when there is no fault.

[0030] Optionally, the criteria for determining the power angle instability of the synchronous motor under repeated low-voltage conditions of new energy sources include:

[0031] When V0(δ,ω)>E cr At that time, the synchronous motor power angle became unstable under repeated low-voltage conditions of the new energy source.

[0032] In another aspect, the present invention also provides a computing device, comprising: one or more processors;

[0033] A processor is used to execute one or more programs;

[0034] When the one or more programs are executed by the one or more processors, the method described above is implemented.

[0035] In another aspect, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed, implements the method described above.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] This invention provides a method for identifying the power angle instability of a synchronous motor under repeated low-voltage ride-through conditions of renewable energy sources. The method includes: establishing an equivalent dynamic model of the renewable energy power station and the power grid under these conditions; based on the equivalent dynamic model, adding renewable energy power coupling terms for the low-voltage ride-through and fault recovery phases of the renewable energy power station, establishing an energy function, and calculating the power angle energy of the synchronous motor based on the energy function; and substituting the power angle energy of the synchronous motor into a preset criterion to identify the power angle instability of the synchronous motor under repeated low-voltage ride-through conditions. This invention, through the equivalent dynamic model and energy function, can explicitly accumulate the energy accumulation during each low-voltage ride-through and the energy dissipation during the recovery phase, forming a quantitative description of the cumulative effect of multiple disturbances, and then providing a stability judgment through a preset criterion. Attached Figure Description

[0038] Figure 1 This is a flowchart of the method of the present invention;

[0039] Figure 2 The above is a combined equivalent circuit diagram of the new energy-synchronous machine for the method of this invention.

[0040] Figure 3 The power angle curve of the synchronous machine in simulation example one of the methods of this invention is shown.

[0041] Figure 4 The power angle energy diagram of the synchronous machine in the simulation example 1 of the method of this invention;

[0042] Figure 5 The power angle curve of the synchronous machine in simulation example two of the method of this invention;

[0043] Figure 6 The power angle curve of the synchronous machine in simulation example two of the method of this invention;

[0044] Figure 7 This is a structural diagram of the system of the present invention. Detailed Implementation

[0045] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0046] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0047] Example 1:

[0048] For situations where the power grid experiences multiple voltage drops and repeated low-voltage ride-throughs after large disturbances under conditions of high-proportion renewable energy integration, existing power angle stability analysis methods have the following shortcomings: First, traditional methods are mostly based on simplified two- or multi-machine static models, mainly considering steady-state angle stability conditions. They typically equate renewable energy disturbances to single faults or equivalent power changes, making it difficult to reflect the temporal superposition effect of multiple power mutations during repeated low-voltage ride-throughs. Second, existing models generally ignore the control response lag, power pulsation, and equivalent energy impact exerted on the power grid by renewable energy units during frequent low-voltage ride-through control, power limiting control, and protection operations, failing to accurately characterize the energy coupling effect between renewable energy power plants and synchronous generators. Third, existing analytical frameworks lack mechanisms to explicitly convert factors such as the electromagnetic transient energy accumulation caused by low-voltage ride-through support and the key energy released or absorbed by different types of renewable energy units during low-voltage ride-throughs into the rotor motion equations. They cannot explain the temporal evolution of the power angle acceleration and deceleration zones after multiple low-voltage ride-throughs from an energy perspective, nor can they provide quantifiable indicators of synchronous stability margin directly related to the characteristics of repeated low-voltage ride-throughs.

[0049] Based on this, the core technical problem that this invention aims to solve is: considering the electromagnetic power mutation and energy accumulation effect caused by low-voltage control, power limiting control and protection actions of new energy units, constructing an analytical model that explicitly introduces additional terms of equivalent disturbance energy and electromagnetic power pulsation of multiple low-voltage runs into the rotor motion equation. This model can uniformly characterize the multi-source energy transfer and conversion process between new energy power plants, synchronous generators and other components of the system, quantitatively describe the power angle dynamic response, the time-series evolution characteristics of the power angle acceleration and deceleration regions and the peak value variation law of the power angle swing after the power grid has experienced multiple low-voltage runs, thereby revealing the energy-power angle correlation mechanism between new energy units, synchronous generators and power angle dynamics, and providing a clear theoretical basis and calculable technical indicators for evaluating the synchronous stability limit under repeated low-voltage runs.

[0050] Therefore, this invention proposes a method S100 for determining the power angle instability of a synchronous motor under repeated low-voltage conditions of new energy sources, such as... Figure 1 As shown, it includes:

[0051] S101, Establish an equivalent dynamic model of new energy power plants and power grid under repeated low-voltage conditions of new energy sources;

[0052] S102, Based on the equivalent dynamic model, for the low-voltage transmission and fault recovery phases of the new energy power station, after adding the new energy power coupling term, an energy function is established, and the power angle energy of the synchronous machine is calculated based on the energy function;

[0053] S103, the power angle energy of the synchronizing machine is input into a preset criterion to determine the instability of the synchronizing machine's power angle under repeated low-voltage conditions of new energy sources.

[0054] The energy function is expressed as follows:

[0055] V σ (δ,ω)=V(δ,ω)+Ψ σ (ΔP,ΔQ)

[0056] Among them, V σ (δ,ω) represents the power angle energy function of the synchronizer during the low-voltage period, V(δ,ω) represents the power angle energy function during the normal period, and Ψ σ (ΔP,ΔQ) is the power coupling term of the new energy source, where ΔP and ΔQ are the power decreases of the active and reactive power of the new energy power station, respectively.

[0057] Optionally, the preset criterion is: V0(δ,ω)>E cr

[0058] Where V0(δ,ω) is the power angle energy of the synchronous machine, and E cr It is the critical energy;

[0059] Among them, the critical energy E cr The calculation formula is as follows:

[0060]

[0061] Where M is the inertia constant of the synchronous machine, For the synchronous machine speed, P1, P M These represent the electromagnetic and mechanical power during the fault, respectively, and δ1 is the synchronous motor power angle when there is no fault.

[0062] Among them, the criteria for determining the instability of the synchronous motor's power angle under repeated low-voltage conditions of new energy sources include:

[0063] When V0(δ,ω)>E cr At that time, the synchronous motor power angle became unstable under repeated low-voltage conditions of the new energy source.

[0064] The above technical solution will be explained in detail below:

[0065] Based on the energy function theory of the combined power transmission system of new energy sources and synchronous machines, an equivalent dynamic model of the new energy power plant-grid is established to reveal the system stability characteristics during the low-voltage ride-through and recovery cycle from an energy perspective. Taking the dynamic changes of active and reactive power of the new energy power plant as the starting point, the impact of power interaction on the dynamic power angle of the synchronous machine during each low-voltage ride-through and recovery process is quantitatively analyzed, thereby assessing the energy increase and decrease characteristics of the system. On this basis, a criterion of critical energy Ecr is introduced to determine whether the system exceeds the stability limit under repeated low-voltage ride-throughs, thereby achieving a quantitative assessment of the instability risk of the synchronous machine.

[0066] If this interconnected power grid is equivalent to a two-machine system, its rotor motion equation can be written as follows, and the equivalent circuit diagram is as follows: Figure 2 As shown:

[0067]

[0068] In the formula, M and δ represent the inertial constant and rotor angle of the synchronous machine; P G1 These are the mechanical power of the zone synchronizing machine, P e (δ) represents the instantaneous electromagnetic power, and D represents the damping coefficient of the synchronous machine;

[0069] When the renewable energy power station repeatedly operates at low voltage, the power of the renewable energy station fluctuates repeatedly, and the renewable energy switches between low voltage and recovery states. The electromagnetic power can be described in the following pattern:

[0070] ΔU PCC =C p ΔP+C q ΔQ

[0071]

[0072] In the formula, ΔU PCC It is the magnitude of the voltage drop at the grid connection point, C p and C q These represent the sensitivities of the renewable energy power plant for active and reactive power, respectively. E is the synchronous machine voltage, X is the line reactance, and δ... s It is the phase difference between the synchronous machine and the grid connection point, P e This refers to the electromagnetic power of the synchronizing machine.

[0073] When a renewable energy power station enters low-voltage operation, its active power decreases by a percentage, while its reactive power decreases according to the grid connection point voltage U. PCC The magnitude of the decrease has been determined.

[0074]

[0075] In the formula, ΔP and ΔQ represent the decrease in active and reactive power at the renewable energy power station, respectively, and U Pcc P is the grid connection point voltage. nomalK represents the active power of the renewable energy power station under normal conditions, K represents the reactive power decrease during low-voltage operation, K1 represents the active power recovery rate, K2 represents the reactive power compensation coefficient, and I represents the reactive power compensation coefficient. N This is the per-unit current.

[0076] When the grid-connected voltage recovers to above 0.9 GHz, the renewable energy power station enters the recovery phase, at which point the power station's output changes as follows:

[0077]

[0078] When the voltage of the new energy source is low, the mechanical power of the synchronous machine is greater than the electromagnetic power, and the power angle accelerates. During the voltage recovery phase of the new energy power station, the electromagnetic power is less than the mechanical power, and the power angle begins to decelerate.

[0079] The Lyapunov function method is used to analyze and construct energy functions under different operating modes of the new energy power station. For the normal operating mode, the traditional energy function is adopted.

[0080]

[0081] The derivation is as follows:

[0082]

[0083] Its derivative is:

[0084]

[0085] For the low-voltage power supply and fault recovery phases of renewable energy power plants, the energy function is constructed by adding a renewable energy power coupling term:

[0086] V σ (δ,ω)=V(δ,ω)+Ψ σ (ΔP,ΔQ)

[0087] Its derivative is:

[0088]

[0089] The derivative of its energy function during the low-voltage and fault recovery phases It may be greater than 0, indicating that the system is in an unstable state and there is energy accumulation in the system.

[0090] During a normal-low-temperature-recovery cycle of a new energy power station, -Dω 2 As the system's inherent damping, it constantly consumes energy. The energy consumed by its inherent damping is:

[0091]

[0092] Where t1 is the time node for entering the low-voltage transmission phase, and t2 is the time node for entering the fault recovery phase.

[0093] The energy accumulated during the low-altitude wear is:

[0094]

[0095] The energy required for the fault recovery phase is:

[0096]

[0097] The energy accumulated within one cycle is:

[0098] ΔV3=ΔV+ΔV1+ΔV2

[0099] If ΔV3 > 0 within one cycle, the power angle accelerates the swing; if ΔV3 < 0, the power angle decays the oscillation.

[0100] When the power angle energy of the synchronizer exceeds the critical energy E cr The critical energy calculation formula for time-work angle instability is as follows:

[0101]

[0102] In the formula, P1, P M These are the electromagnetic and mechanical power between faults.

[0103] If the energy accumulated within a certain period is V0(δ,ω)>E cr Then it is determined that the work angle is unstable.

[0104] This invention addresses the combined power transmission system of new energy sources and synchronous generators. Under repeated low-voltage ride-through conditions at new energy power plants, it establishes a quantitative assessment method for synchronization stability based on multiple Lyapunov energy functions. By dynamically analyzing each low-voltage ride-through and recovery process at the power plant, it uniformly models and quantifies the energy injected into or absorbed from the system by the new energy power plant during low-voltage ride-through, as well as the energy consumed by the synchronous generator during acceleration and deceleration during the fault recovery phase. This yields the critical energy boundary of the synchronous generator's power angle, thereby determining whether the system has lost synchronization. Compared to traditional analysis methods that rely solely on the equal-area method or a single energy function and are heavily dependent on the grid's operating mode, this invention offers the following advantages:

[0105] Critical Energy Criterion:

[0106] By constructing a multi-Lyapunov energy function, the power angle under different operating modes, different fault types, and different underpasses is dynamically and uniformly mapped to the energy space to obtain the critical energy, and the impact of repeated underpasses of new energy power plants on the synchronization stability of the synchronous machine is quickly determined.

[0107] It can quantitatively characterize the energy accumulation effect and provide a criterion for synchronous instability:

[0108] This invention explicitly accumulates the energy accumulation during each low-level penetration period and the energy dissipation during the recovery phase, forming a quantitative description of the cumulative effect of multiple disturbances and providing a stability judgment.

[0109] This invention is applied to new energy-synchronous machine combined power transmission systems, such as... Figure 2 As shown, the synchronous generator has a power of 300MW and a load of 525MW. The power of the new energy power station is 300MW. When a three-terminal n-1 fault occurs on the grid connection line, the new energy unit starts to repeatedly operate at low power, causing the synchronous generator to oscillate.

[0110] The generator's inertial constant is: T J =8

[0111] The initial power is: P G1 =300MW P w =300MW

[0112] The per-unit equivalent reactance of the transmission section is: x 12 =0.0008

[0113] E was calculated Cr =30

[0114] Simulation Example 1 (300MW of new energy power output): For example Figure 3 and Figure 4 The new energy unit repeatedly operates at low power, and the synchronous motor power angle energy has not reached the critical energy (V0(δ,ω)<E). Cr =30), and the energy decreases in each cycle, and the power angle begins to oscillate and decay.

[0115] Simulation Example 2 (400MW output from new energy sources): For example... Figure 5 and Figure 6 The new energy unit repeatedly operates at low voltage, and the synchronous machine power angle energy exceeds the critical energy (V0(δ,ω)>E). Cr =30), the angle of attack begins to diverge.

[0116] Example 2:

[0117] This invention also proposes a discrimination system 200 for synchronous machine power angle instability under repeated low-voltage conditions of new energy sources, such as... Figure 7 As shown, it includes:

[0118] Modeling unit 201 is used to establish an equivalent dynamic model of the new energy power station and the power grid under the condition of repeated low-voltage ride-through of new energy sources;

[0119] The calculation unit 202 is used to establish an energy function based on the equivalent dynamic model, for the low-voltage transmission and fault recovery stages of the new energy power station, after adding the new energy power coupling term, and to calculate the power angle energy of the synchronous machine based on the energy function.

[0120] The discrimination unit 203 is used to input the power angle energy of the synchronizing machine into a preset criterion to discriminate the power angle instability of the synchronizing machine under repeated low-voltage conditions of new energy sources.

[0121] The energy function is expressed as follows:

[0122] V σ (δ,ω)=V(δ,ω)+Ψ σ (ΔP,ΔQ)

[0123] Among them, V σ (δ,ω) represents the power angle energy function of the synchronizer during the low-voltage period, V(δ,ω) represents the power angle energy function during the normal period, and Ψ σ (ΔP,ΔQ) is the power coupling term of the new energy source, where ΔP and ΔQ are the power decreases of the active and reactive power of the new energy power station, respectively.

[0124] The preset criterion is: V0(δ,ω)>E cr

[0125] Where V0(δ,ω) is the power angle energy of the synchronous machine, and E cr It is the critical energy;

[0126] Among them, the critical energy E cr The calculation formula is as follows:

[0127]

[0128] Where M is the inertia constant of the synchronous machine, For the synchronous machine speed, P1, P M These represent the electromagnetic and mechanical power during the fault, respectively, and δ1 is the synchronous motor power angle before the fault.

[0129] Among them, the criteria for determining the instability of the synchronous motor's power angle under repeated low-voltage conditions of new energy sources include:

[0130] When V0(δ,ω)>E cr At that time, the synchronous motor power angle became unstable under repeated low-voltage conditions of the new energy source.

[0131] This invention uses an equivalent dynamic model and an energy function to explicitly accumulate the energy accumulation during each low-level penetration and the energy dissipation during the recovery phase, forming a quantitative description of the cumulative effect of multiple disturbances, and then provides a stability judgment through a preset criterion.

[0132] Example 3:

[0133] Based on the same inventive concept, this invention also provides a computer device, which includes a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions in the computer storage medium to implement corresponding method flows or corresponding functions, thereby implementing the steps of the methods in the above embodiments.

[0134] Example 4:

[0135] Based on the same inventive concept, this invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and extended storage media supported by the computer device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of the method in the above embodiments.

[0136] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention 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 the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0137] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. 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 illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0138] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0139] 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.

[0140] Although preferred embodiments of the invention 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 both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0141] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for determining the power angle instability of a synchronous motor under repeated low-voltage power surges from new energy sources, characterized in that, include: Establish an equivalent dynamic model of new energy power plants and power grid under repeated low-voltage conditions; Based on the equivalent dynamic model, for the low-voltage transmission and fault recovery phases of new energy power stations, after adding the new energy power coupling term, an energy function is established, and the power angle energy of the synchronous machine is calculated based on the energy function. The power angle energy of the synchronizing machine is used as a preset criterion to determine the instability of the synchronizing machine's power angle under repeated low-voltage conditions of new energy sources.

2. The discrimination method according to claim 1, characterized in that, The expression for the energy function is as follows: V σ (δ,ω)=V(δ,ω)+Ψ σ (ΔP,ΔQ) Among them, V σ (δ,ω) represents the power angle energy function of the synchronizer during the low-voltage period, V(δ,ω) represents the power angle energy function during the normal period, and Ψ σ (ΔP,ΔQ) is the power coupling term of the new energy source, where ΔP and ΔQ are the power decreases of the active and reactive power of the new energy power station, respectively.

3. The discrimination method according to claim 1, characterized in that, The preset criterion is: V0(δ,ω)>E cr ; Where V0(δ,ω) is the power angle energy of the synchronous machine, and E cr This is the critical energy.

4. The discrimination method according to claim 3, characterized in that, The critical energy E cr The calculation formula is as follows: Where M is the inertia constant of the synchronous machine, For the synchronous machine speed, P1, P M These represent the electromagnetic and mechanical power during the fault, respectively, and δ1 is the synchronous motor power angle before the fault.

5. The discrimination method according to claim 1, characterized in that, The determination of synchronous motor power angle instability under repeated low-voltage conditions of the new energy source includes: When V0(δ,ω)>E cr At that time, the synchronous motor power angle became unstable under repeated low-voltage conditions of the new energy source.

6. A system for determining the instability of the power angle of a synchronous motor under repeated low-voltage power surges from new energy sources, characterized in that, include: The modeling unit is used to establish an equivalent dynamic model of the renewable energy power station and the power grid under the condition of repeated low-voltage ride-through of renewable energy sources. The calculation unit is used to establish an energy function based on the equivalent dynamic model, for the low-voltage transmission and fault recovery phases of the new energy power station, after adding the new energy power coupling term, and to calculate the power angle energy of the synchronous machine based on the energy function. The discrimination unit is used to input the power angle energy of the synchronizing machine into a preset criterion to discriminate the power angle instability of the synchronizing machine under repeated low-voltage conditions of new energy sources.

7. The discrimination system according to claim 6, characterized in that, The expression for the energy function is as follows: V σ (δ,ω)=V(δ,ω)+Ψ σ (ΔP,ΔQ) Among them, V σ (δ,ω) represents the power angle energy function of the synchronizer during the low-voltage period, V(δ,ω) represents the power angle energy function during the normal period, and Ψ σ (ΔP,ΔQ) is the power coupling term of the new energy source, where ΔP and ΔQ are the power decreases of the active and reactive power of the new energy power station, respectively.

8. The discrimination system according to claim 6, characterized in that, The preset criterion is: V0(δ,ω)>E cr ; Where V0(δ,ω) is the power angle energy of the synchronous machine, and E cr This is the critical energy.

9. The discrimination system according to claim 8, characterized in that, The critical energy E cr The calculation formula is as follows: Where M is the inertia constant of the synchronous machine, For the synchronous machine speed, P1, P M δ1 represents the electromagnetic and mechanical power during the fault period, respectively, and δ2 represents the power angle of the synchronous machine when there is no fault.

10. The discrimination system according to claim 6, characterized in that, The determination of synchronous motor power angle instability under repeated low-voltage conditions of the new energy source includes: When V0(δ,ω)>E cr At that time, the synchronous motor power angle became unstable under repeated low-voltage conditions of the new energy source.

11. A computer device, characterized in that, include: One or more processors; A processor is used to execute one or more programs; When the one or more programs are executed by the one or more processors, the method described in any one of claims 1-5 is implemented.

12. A computer-readable storage medium, characterized in that, It contains a computer program, which, when executed, implements the method as described in any one of claims 1-5.

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