A method and device for constructing transient stability boundary of a wind-thermal bundled system

Abstract

The application discloses a kind of wind-fire bundling system transient stability boundary construction method and device, method includes: based on the structure characteristics and operating characteristics of wind-fire bundling system, the equivalent model of wind-fire bundling system is established;Based on the operation of wind-fire bundling system in different fault stages, and in combination with the equivalent model, and the wind power generator set output and grid point residual voltage of wind-fire bundling system during fault low voltage ride through, determine the power and phase angle curve of wind-fire bundling system in different fault stages;Based on the power and phase angle curve of wind-fire bundling system in different fault stages, determine the stability margin of wind-fire bundling system about wind power generator set output and grid point residual voltage;Based on the stability margin about wind power generator set output and grid point residual voltage during fault, construct the transient stability boundary based on wind power generator set output and grid point residual voltage.The application can be according to wind power generator set output and grid point residual voltage, quickly and accurately judge whether wind-fire bundling system is located in stable region.

Description

Technical Field

[0001] This invention belongs to the field of power system transient stability technology, specifically relating to a method and apparatus for constructing transient stability boundaries for a wind-fire bundled system. Background Technology

[0002] With the acceleration of the global energy transition, wind power has become a core pathway for large-scale clean energy development. In some regions rich in wind and solar resources, inter-regional power transmission systems based on wind-thermal power bundling have been established. This multi-energy complementary model of "wind, solar, thermal, and energy storage" has solved the challenge of long-distance transmission of new energy power. This model not only aligns with the spatial distribution characteristics of new energy resources but also significantly enhances the system's inertia support capacity through deep peak shaving of thermal power, providing key technical support for the high-proportion consumption of new energy.

[0003] However, when external disturbances (such as short-circuit faults) cause a voltage drop in the grid, wind turbines must strictly adhere to the "Technical Regulations for Wind Farm Connection to the Power System" to perform Low Voltage Ride Through (LVRT) operations. During this time, the turbine injects dynamic reactive current into the system through the converter to support the grid connection voltage. However, this nonlinear control strategy leads to time-varying characteristics in the system's equivalent impedance. Related research indicates that the transient power angle stability of wind-thermal bundled systems is influenced by multiple coupled factors: macroscopic structural factors such as the wind-thermal installed capacity ratio and wind power penetration rate, as well as microscopic operating conditions such as fault location and load characteristics. While existing methods have established multidimensional correlation models between the wind-thermal ratio and fault location, most of these methods focus on steady-state or conventional fault scenarios, failing to fully consider the complex characteristics of the dynamic reactive current injection by wind turbines through the converter during LVRT, resulting in deviations between stability analysis results and actual operating conditions.

[0004] For example, patent CN119009977A discloses a method, system, computer equipment, and computer-readable storage medium for analyzing the transient power angle stability characteristics of a wind-fire bundled system. The method includes: converting the wind-fire bundled system into an equivalent single-machine infinite bus system and a Hamiltonian single-machine infinite bus system; calculating the synchronous motor power angle characteristic equations for three time periods—before the fault, during the fault, and after the wind power active power recovery phase following fault clearance—based on the equivalent single-machine infinite bus system; calculating the synchronous motor power angle characteristic equations for the wind power active power recovery phase after fault clearance based on the preset fault; and calculating the system's transient power angle stability margin on the P-δ phase plane based on the synchronous motor power angle characteristic equations and the corresponding power angles for each time period. This method still has the following drawbacks:

[0005] 1. The active power recovery phase of wind power after fault clearing is divided into several sub-periods, and then the equivalent angle value is calculated iteratively, which results in a certain delay and cannot meet the real-time assessment requirements.

[0006] 2. The model overemphasizes three-phase short-circuit faults and fails to adequately consider the dynamic impact of asymmetrical faults and LVRT scenarios. Although it considers active power recovery during LVRT, the model is oversimplified: ① The active power recovery of wind power uses a fixed slope and does not consider the impact of dynamic changes in voltage drop depth on the recovery process. ② Reactive power support is simplified to constant power factor control, ignoring the actual situation of priority injection of reactive current during LVRT. The time-varying characteristics of wind turbine output are not reflected in the area determination, which easily introduces linearization errors, reduces the adaptability to high-proportion renewable energy grids, and leads to an underestimation of stability margin and limited calculation accuracy.

[0007] For example, patent CN117374910A discloses a method and system for rapidly estimating the transient stability limit of an AC transmission line in a wind-fire bundled system. This method includes collecting wind turbine operating data, constructing an infinite-size system model of a single wind-fire bundled unit, and establishing a simplified system. Based on the simplified system, it establishes rotor motion equations and analyzes the system's operation during fault periods. It also preprocesses the influence of wind power grid-connected capacity and actual wind power output on the transient stability limit of the wind-fire bundled system, and rapidly estimates the transient stability of a single-channel AC transmission tie line in the wind-fire bundled system. However, this method also has the following shortcomings:

[0008] 1. During the active power recovery phase after the fault is cleared, it is also necessary to divide it into several sub-periods and calculate the equivalent value of the power angle using the differential method, which cannot meet the requirements of real-time online monitoring.

[0009] 2. Ignoring the generator's internal impedance and treating the system as a pure external impedance model reduces the accuracy of the model simplification.

[0010] 3. The reactive power support effect during the low voltage drop period of the wind turbine is considered, but the reactive power dynamics are not directly modeled. The influence coefficient of the grid-connected capacity of the wind turbine is directly introduced for approximate characterization. This simplifies the nonlinear reactive power injection to a fixed ratio and cannot reflect the dynamic changes of reactive power with voltage drop depth and time.

[0011] 4. The nonlinear power angle change and reactive power support effect under low voltage ride-through scenarios are not fully considered. Specifically, ① the acceleration area processing simplifies the nonlinear power angle change to linear growth, ignoring the dynamic changes in wind turbine output during the fault period (such as the nonlinear process of low voltage ride-through recovery). This results in large calculation errors and low real-time performance, which can easily lead to the stability margin estimation deviating from reality and making it unsuitable for online application; ② its maximum deceleration area is based on an ideal sine curve and fixed slope recovery assumptions (such as instantaneous power recovery), without considering the reactive power support effect and multi-fault type adaptation (such as asymmetrical faults). This can easily lead to calculation results lower than the actual value, thereby underestimating the system capacity, and its adaptability in multiple scenarios is poor.

[0012] Therefore, in the context of large-scale grid connection of new energy sources, there is an urgent need to propose an analytical method that can quickly identify the stability boundary of the system under low voltage ride-through conditions, so as to provide theoretical support for the security defense of AC / DC hybrid power grids with a high proportion of renewable energy. Summary of the Invention

[0013] To address the shortcomings of the existing technology, this invention provides a method and apparatus for constructing the transient stability boundary of a wind-fire baling system. This invention can quickly and accurately determine whether the wind-fire baling system is within the stable region based on the wind turbine output and the residual voltage at the grid connection point.

[0014] In a first aspect, the present invention provides a method for constructing the transient stability boundary of a wind-fire bundling system, comprising:

[0015] Based on the structural characteristics and operational features of the wind-fire bundling system, an equivalent model of the wind-fire bundling system is established.

[0016] Based on the operation of the wind-fire bundling system at different fault stages, and combined with the equivalent model, as well as the wind turbine output and grid connection point residual voltage during low voltage ride-through of the wind-fire bundling system during the fault, the power and phase angle curves of the wind-fire bundling system at different fault stages are determined.

[0017] Based on the power and phase angle curves of the wind-fire bundling system at different fault stages, the stability margin of the wind-fire bundling system with respect to the wind turbine output and the residual voltage at the grid connection point is determined.

[0018] Based on the stability margin during the fault period, a transient stability boundary is constructed based on the wind turbine output and the residual voltage at the grid connection point.

[0019] Furthermore, based on the structural characteristics and operational features of the wind-fire bundling system, an equivalent model of the wind-fire bundling system is established, including:

[0020] The AC power grid of the combined wind and fire system is equivalent to an infinite system.

[0021] Based on the topological relationship between wind turbines, thermal power units, and the AC power grid, the wind turbines, thermal power units, and the infinite power system are connected by lines, and an initial system model is given. The topological relationship between the wind turbines, thermal power units, and the AC power grid includes: the wind turbines and thermal power units are connected in parallel through transmission lines, and then the power is transmitted to the infinite power system through a double-circuit transmission line.

[0022] Based on the operating characteristics of the wind-fired power tying system, the operating parameters of the wind turbine, thermal power unit, infinite bus system, and transmission line in the initial system model are determined, and an equivalent model of the wind-fired power tying system is given.

[0023] Furthermore, the power and phase angle curves of the wind-fire bundling system at different fault stages were determined, including:

[0024] Based on the operation of the wind-fire bundling system at different fault stages, and combined with the equivalent model, as well as the wind turbine output and grid connection point residual voltage during low voltage ride-through of the wind-fire bundling system during the fault, the maximum electromagnetic power of the wind-fire bundling system at different fault stages is given.

[0025] Based on the equivalent model, a rotor motion model of a thermal power unit is constructed;

[0026] Based on the rotor motion model of thermal power units and combined with the maximum electromagnetic power of the wind-fire bundling system at different fault stages, the phase angles of the wind-fire bundling system at the corresponding key operating points at different fault stages are given.

[0027] Furthermore, based on the operation of the wind-fire tying system at different fault stages, and combined with the equivalent model, as well as the wind turbine output and grid connection residual voltage during low-voltage ride-through of the wind-fire tying system during the fault, the maximum electromagnetic power of the wind-fire tying system at different fault stages is given, including:

[0028] Based on the reactive power injection of the wind-fire bundling system during the low voltage ride-through scenario during the fault, the wind turbine output and grid connection point residual voltage during the fault are determined.

[0029] Based on the operation of the wind-fire bundled system at different fault stages, and combined with the equivalent model, as well as the wind turbine output and grid connection point residual voltage during the fault, the interconnection reactance between the wind-fire bundled system and the thermal power unit and the infinite bus system are given for the wind-fire bundled system at different fault stages; where different fault stages include before the fault, during the fault, and after the fault.

[0030] Based on the operating parameters of the generator and the infinite bus system in the equivalent model, and combined with the interconnecting reactance between the thermal power unit and the infinite bus system, the maximum electromagnetic power of the wind-fire bundled system is given for different fault stages.

[0031] Furthermore, based on the operational status of the wind-fired power tying system at different fault stages, and combined with the equivalent model, as well as the wind turbine output and grid connection point residual voltage during the fault, the interconnection reactance between the wind-fired power tying system and the thermal power unit at different fault stages is given, including:

[0032] Based on the first operating parameters of the equivalent model, the connection reactance between the thermal power unit and the infinite system in the wind-fired power bundled system is determined before and after the fault. The first operating parameters include the transient reactance of the generator, the thermal power step-up transformer, the reactance of the transmission line corresponding to the thermal power unit, the wind power step-up transformer, the reactance of the transmission line corresponding to the wind power unit, the reactance of a single line of the double-circuit transmission line, and the equivalent reactance of the infinite system.

[0033] Based on the location of the fault point, determine the equivalent additional reactance for different fault points;

[0034] Obtain the per-unit value of the residual voltage at the grid connection point of the wind farm and the per-unit value of the dynamic reactive current increment injected by the wind farm under the low voltage ride-through scenario of the wind-fire bundled system, and determine the equivalent reactance of the wind turbine during the fault period;

[0035] Based on the equivalent reactance of the wind turbine during the fault period, the equivalent additional reactance at different fault points, and combined with the first operating parameters, the connection reactance between the thermal power unit and the infinite bus system at different fault points of the wind-fire bundled system during the fault period is determined.

[0036] Furthermore, based on the operating parameters of the generator and the infinite bus system in the equivalent model, and combined with the interconnecting reactance between the thermal power unit and the infinite bus system, the maximum electromagnetic power of the wind-fired power system at different fault stages is given, including:

[0037] Based on the second operating parameters of the equivalent model, and combined with the interconnecting reactance between the thermal power unit and the infinite power system before, during, and after the fault, the maximum electromagnetic power of the wind-fire bundling system is given before, during, and after the fault. The second operating parameters include the terminal voltage of the infinite power system and the internal potential of the generator.

[0038] Furthermore, based on the rotor motion model of the thermal power unit and combined with the maximum electromagnetic power of the wind-fire bundling system at different fault stages, the phase angles of the wind-fire bundling system at key operating points corresponding to different fault stages are given, including:

[0039] Based on the rotor motion model of thermal power units, the mechanical power, wind turbine output, generator moment of inertia, and generator speed reference values ​​of the wind-fired power bundling system in steady state are determined.

[0040] Based on the steady-state mechanical power and wind turbine output of the wind-fire bundling system, and combined with the maximum electromagnetic power of the wind-fire bundling system before the fault, the phase angle of the wind-fire bundling system at the steady-state operating point before the fault is given.

[0041] Based on the steady-state mechanical power, generator rotational inertia, fault clearing time, and wind turbine output during the fault of the wind-fire bundling system, and combined with the phase angle of the wind-fire bundling system at the corresponding critical operating point before the fault, the fault clearing angle of the wind-fire bundling system at the corresponding fault clearing time during the fault is given.

[0042] Based on the steady-state mechanical power and wind turbine output of the wind-fire bundling system, and combined with the maximum electromagnetic power of the wind-fire bundling system after a fault, the phase angle of the wind-fire bundling system at the corresponding unstable operating point after a fault is given.

[0043] Furthermore, based on the power and phase angle curves of the wind-fire tying system at different fault stages, the stability margin of the wind-fire tying system with respect to wind turbine output and grid connection point residual voltage is determined, including:

[0044] Determine the first difference between the mechanical power of the wind-fire bundling system in steady state and the output of the wind turbine during a fault; and give the second difference between the first difference and the maximum electromagnetic power corresponding to the fault.

[0045] Integrating the second difference with respect to the phase angle from the steady-state operating point to the fault clearing angle at the fault clearing time yields the acceleration area during the fault period;

[0046] Determine the third difference between the mechanical power of the wind-fire baling system and the output of the wind turbine in steady state; and give the fourth difference between the maximum electromagnetic power of the wind-fire baling system after a fault and the third difference.

[0047] Integrating the fourth difference with respect to the phase angle from the fault clearing angle at the fault clearing moment to the unstable operating point yields the maximum deceleration area after the fault.

[0048] Based on the difference between the maximum deceleration area after the fault and the acceleration area during the fault, the stability margin of the wind-fire bundling system with respect to the wind turbine output and the residual voltage at the grid connection point is determined.

[0049] Furthermore, based on the stability margins of wind turbine output and grid connection point residual voltage during the fault period, a transient stability boundary based on wind turbine output and grid connection point residual voltage is constructed, including:

[0050] Obtain the wind turbine output and grid connection point residual voltage when the stability margin of the wind turbine output and grid connection point residual voltage of the wind-fire bundling system is zero;

[0051] Using the wind turbine output and grid connection point residual voltage as the horizontal and vertical axes respectively, a critical stability domain diagram is constructed, with zero-value stability margin as the transient stability boundary.

[0052] Secondly, the present invention also provides a transient stability boundary construction device for a wind-fire bundling system, employing the aforementioned transient stability boundary construction method for a wind-fire bundling system, the device comprising:

[0053] The model building module is used to establish an equivalent model of the wind and fire bundling system based on its structural characteristics and operational features.

[0054] The curve determination module is used to determine the power and phase angle curves of the wind-fire bundling system at different fault stages based on the operation of the wind-fire bundling system at different fault stages, combined with the equivalent model, as well as the output of the wind turbine and the residual voltage at the grid connection point during the low voltage ride-through of the wind-fire bundling system during the fault.

[0055] The index determination module is used to determine the stability margin of the wind turbine output and grid connection point residual voltage of the wind-fire bundled system based on the power and phase angle curves of the wind-fire bundled system at different fault stages.

[0056] The boundary delineation module is used to construct transient stability boundaries based on the wind turbine output and the residual pressure at the grid connection point, based on the stability margin during the fault period.

[0057] Furthermore, the model building module is also used for:

[0058] The AC power grid of the combined wind and fire system is equivalent to an infinite system.

[0059] Based on the topological relationship between wind turbines, thermal power units, and the AC power grid in the wind-thermal bundled system, the wind turbines, thermal power units, and the infinite power system are connected by lines, and an initial system model is given. The topological relationship between the wind turbines, thermal power units, and the AC power grid includes: the wind turbines and thermal power units are connected in parallel through transmission lines, and then the power is transmitted to the infinite power system through a double-circuit transmission line.

[0060] Based on the operating characteristics of the wind-fired power tying system, the operating parameters of the wind turbine, thermal power unit, infinite bus system, and transmission line in the initial system model are determined, and an equivalent model of the wind-fired power tying system is given.

[0061] Furthermore, the curve determination module is used for:

[0062] Based on the operation of the wind-fire bundling system at different fault stages, and combined with the equivalent model, as well as the wind turbine output and grid connection point residual voltage during low voltage ride-through of the wind-fire bundling system during the fault, the maximum electromagnetic power of the wind-fire bundling system at different fault stages is given.

[0063] Based on the equivalent model, a rotor motion model of a thermal power unit is constructed;

[0064] Based on the rotor motion model of thermal power units and combined with the maximum electromagnetic power of the wind-fire bundling system at different fault stages, the phase angles of the wind-fire bundling system at the corresponding key operating points at different fault stages are given.

[0065] Furthermore, the curve determination module is used for:

[0066] Based on the reactive power injection of the wind-fire bundling system during the low voltage ride-through scenario during the fault, the wind turbine output and grid connection point residual voltage during the fault are determined.

[0067] Based on the operation of the wind-fire bundled system at different fault stages, and combined with the equivalent model, as well as the wind turbine output and grid connection point residual voltage during the fault, the interconnection reactance between the wind-fire bundled system and the thermal power unit and the infinite bus system are given for the wind-fire bundled system at different fault stages; where different fault stages include before the fault, during the fault, and after the fault.

[0068] Based on the operating parameters of the generator and the infinite bus system in the equivalent model, and combined with the interconnecting reactance between the thermal power unit and the infinite bus system, the maximum electromagnetic power of the wind-fire bundled system is given for different fault stages.

[0069] Furthermore, the curve determination module is used for:

[0070] Based on the first operating parameters of the equivalent model, the connection reactance between the thermal power unit and the infinite system in the wind-fired power bundled system is determined before and after the fault. The first operating parameters include the transient reactance of the generator, the thermal power step-up transformer, the reactance of the transmission line corresponding to the thermal power unit, the wind power step-up transformer, the reactance of the transmission line corresponding to the wind power unit, the reactance of a single line of the double-circuit transmission line, and the equivalent reactance of the infinite system.

[0071] Based on the location of the fault point, determine the equivalent additional reactance for different fault points;

[0072] Obtain the per-unit value of the residual voltage at the grid connection point of the wind farm and the per-unit value of the dynamic reactive current increment injected by the wind farm under the low voltage ride-through scenario of the wind-fire bundled system, and determine the equivalent reactance of the wind turbine during the fault period;

[0073] Based on the equivalent reactance of the wind turbine during the fault period, the equivalent additional reactance at different fault points, and combined with the first operating parameters, the connection reactance between the thermal power unit and the infinite bus system at different fault points of the wind-fire bundled system during the fault period is determined.

[0074] Furthermore, the curve determination module is used for:

[0075] Based on the second operating parameters of the equivalent model, and combined with the interconnecting reactance between the thermal power unit and the infinite power system before, during, and after the fault, the maximum electromagnetic power of the wind-fire bundling system is given before, during, and after the fault. The second operating parameters include the terminal voltage of the infinite power system and the internal potential of the generator.

[0076] Furthermore, the curve determination module is also used for:

[0077] Based on the rotor motion model of thermal power units, the mechanical power, wind turbine output, generator moment of inertia, and generator speed reference values ​​of the wind-fired power bundling system in steady state are determined.

[0078] Based on the steady-state mechanical power and wind turbine output of the wind-fire bundling system, and combined with the maximum electromagnetic power of the wind-fire bundling system before the fault, the phase angle of the wind-fire bundling system at the steady-state operating point before the fault is given.

[0079] Based on the steady-state mechanical power, generator rotational inertia, fault clearing time, and wind turbine output during the fault of the wind-fire bundling system, and combined with the phase angle of the wind-fire bundling system at the corresponding critical operating point before the fault, the fault clearing angle of the wind-fire bundling system at the corresponding fault clearing time during the fault is given.

[0080] Based on the steady-state mechanical power and wind turbine output of the wind-fire bundling system, and combined with the maximum electromagnetic power of the wind-fire bundling system after a fault, the phase angle of the wind-fire bundling system at the corresponding unstable operating point after a fault is given.

[0081] Furthermore, the indicator determination module is also used for:

[0082] Determine the first difference between the mechanical power of the wind-fire bundling system in steady state and the output of the wind turbine during a fault; and give the second difference between the first difference and the maximum electromagnetic power corresponding to the fault.

[0083] Integrating the second difference with respect to the phase angle from the steady-state operating point to the fault clearing angle at the fault clearing time yields the acceleration area during the fault period;

[0084] Determine the third difference between the mechanical power of the wind-fire baling system and the output of the wind turbine in steady state; and give the fourth difference between the maximum electromagnetic power of the wind-fire baling system after a fault and the third difference.

[0085] Integrating the fourth difference with respect to the phase angle from the fault clearing angle at the fault clearing moment to the unstable operating point yields the maximum deceleration area after the fault.

[0086] Based on the difference between the maximum deceleration area after the fault and the acceleration area during the fault, the stability margin of the wind-fire bundling system with respect to the wind turbine output and the residual voltage at the grid connection point is determined.

[0087] Furthermore, the boundary delimitation module is also used for:

[0088] Obtain the wind turbine output and grid connection point residual voltage when the stability margin of the wind turbine output and grid connection point residual voltage of the wind-fire bundling system is zero;

[0089] Using the wind turbine output and grid connection point residual voltage as the horizontal and vertical axes respectively, a critical stability domain diagram is constructed, with zero-value stability margin as the transient stability boundary.

[0090] The present invention provides a method and apparatus for constructing the transient stability boundary of a wind-fire bundling system, which has at least the following beneficial effects:

[0091] (1) By constructing a high-precision transient stability boundary based on the output of the wind turbine and the residual pressure at the grid connection point, the stable and unstable regions can be accurately divided, which facilitates quick querying of whether the current state of the wind-fire bundling system is within the stable region, reducing calculation and judgment time.

[0092] (2) By characterizing the severity of the fault through the residual voltage at the grid connection point and correlating reactive current injection and equivalent impedance, the stability boundary can be dynamically corrected, which can adapt to various fault types and improve the engineering generalization ability. Attached Figure Description

[0093] Figure 1 This invention provides a method for constructing the transient stability boundary of a wind-fire bundling system;

[0094] Figure 2 An architecture diagram of a transient stability boundary construction method provided in a certain embodiment of the present invention;

[0095] Figure 3 A flowchart for establishing an equivalent model provided in one embodiment of the present invention;

[0096] Figure 4 A schematic diagram of an equivalent model provided in a certain embodiment of the present invention;

[0097] Figure 5 A flowchart for determining power and phase angle curves is provided in one embodiment of the present invention;

[0098] Figure 6 A flowchart for determining the maximum electromagnetic power provided in one embodiment of the present invention;

[0099] Figure 7 A flowchart of the contact reactance is provided for one embodiment of the present invention;

[0100] Figure 8 A flowchart providing phase angles is provided for one embodiment of the present invention;

[0101] Figure 9 This is a schematic diagram of a transient stability boundary construction device for a wind and fire bundling system provided by the present invention. Detailed Implementation

[0102] To better understand the above technical solutions, a detailed description of the solutions will be provided below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0103] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0104] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0105] like Figure 1 and Figure 2 As shown, this invention provides a method for constructing the transient stability boundary of a wind-fire bundling system, comprising:

[0106] Based on the structural characteristics and operational features of the wind-fire bundling system, an equivalent model of the wind-fire bundling system is established.

[0107] Based on the operation of the wind-fire bundling system at different fault stages, and combined with the equivalent model, as well as the wind turbine output and grid connection point residual voltage during low voltage ride-through of the wind-fire bundling system during the fault, the power and phase angle curves of the wind-fire bundling system at different fault stages are determined.

[0108] Based on the power and phase angle curves of the wind-fire bundling system at different fault stages, the stability margin of the wind-fire bundling system with respect to the wind turbine output and the residual voltage at the grid connection point is determined.

[0109] Based on the stability margin during the fault period, a transient stability boundary is constructed based on the wind turbine output and the residual voltage at the grid connection point.

[0110] In practical application scenarios, such as Figure 3 As shown, based on the structural characteristics and operational features of the wind-fire bundling system, an equivalent model of the wind-fire bundling system is established, which may include:

[0111] The AC power grid of the combined wind and fire system is equivalent to an infinite system.

[0112] Based on the topological relationship between wind turbines, thermal power units, and the AC power grid in the wind-thermal bundled system, the wind turbines, thermal power units, and the infinite power system are connected by lines, and an initial system model is given. The topological relationship between the wind turbines, thermal power units, and the AC power grid includes: the wind turbines and thermal power units are connected in parallel through transmission lines, and then the power is transmitted to the infinite power system through a double-circuit transmission line.

[0113] Based on the operating characteristics of the wind-fired power tying system, the operating parameters of the wind turbine, thermal power unit, infinite bus system, and transmission line in the initial system model are determined, and an equivalent model of the wind-fired power tying system is given.

[0114] In practical applications, the equivalent model constructed is as follows: Figure 4 The illustrated model of a combined wind and thermal power unit (WHM) system shows wind turbines and thermal power units connected in parallel via separate transmission lines, with power then transmitted to the WHM system via a double-circuit transmission line. The WHM system and the WHM system represent simplified equivalent descriptions of the power source and grid side, respectively. Specifically, the WHM system refers to the combined operation of wind and thermal power units as equivalent to a single equivalent synchronous generator. The active power output of this equivalent synchronous generator is equivalent to the sum of the outputs of the wind turbines and thermal power units (or the coordinated output of thermal power units tracking wind power fluctuations). The reactive power output is equivalent to that provided by the thermal power units (or the coordinated control of wind and thermal power). Its dynamic characteristics are reflected by the rotor motion equations / models (power angle characteristics) of the equivalent synchronous generator, showing the power balance between the combined wind and thermal power source and the grid. The WHM system refers to an ideal grid with extremely large capacity and constant voltage (unaffected by power changes). The operating data of the wind-fire bundled single-unit infinite system model includes the generator's internal electromotive force and phase angle E'∠δ; the infinite system voltage and phase angle U∠0°; and the active power output P of the wind turbine. w Generator mechanical power P m During normal operation, it equals the generator's electromagnetic power P. e The interconnecting reactance x between the thermal power unit and the AC power grid (infinite current system) before the fault. Σ The constructed equivalent model simplifies the actual complex wind-fire bundled system (such as multi-machine interconnection, multi-circuit lines, etc.) into an equivalent topology containing synchronous generators, wind turbines, transformers, transmission lines and infinite busbars. This simplification preserves the main dynamic characteristics of the wind-fire bundled system (such as the transient process dominated by the rotor motion equation).

[0115] like Figure 5 As shown, based on the operation of the wind-fire tying system at different fault stages, and combined with the equivalent model, as well as the wind turbine output and grid connection residual voltage during low-voltage ride-through of the wind-fire tying system during the fault, the power and phase angle curves of the wind-fire tying system at different fault stages are determined, including:

[0116] Based on the operation of the wind-fire bundling system at different fault stages, and combined with the equivalent model, as well as the wind turbine output and grid connection point residual voltage during low voltage ride-through of the wind-fire bundling system during the fault, the maximum electromagnetic power of the wind-fire bundling system at different fault stages is given.

[0117] Based on the equivalent model, a rotor motion model for a thermal power unit is constructed, satisfying the following relationship:

[0118]

[0119] In the formula, M is the generator's moment of inertia; ω is the generator's rotational speed; ω * ω0 is the generator speed per unit value; δ is the generator speed reference value; P is the generator power angle; m P represents the mechanical power of the generator. w For wind turbine output; E' is the generator internal potential; U is the infinite system terminal voltage; x Σ The interconnecting reactance between the thermal power unit and the infinite power system;

[0120] Based on the rotor motion model of a thermal power unit and combined with the maximum electromagnetic power of the wind-fire bundling system at different fault stages, the phase angles of the wind-fire bundling system at key operating points corresponding to different fault stages are given. The electromagnetic power and phase angle of the wind-fire bundling system at key operating points corresponding to different fault stages as a function of time are represented by the power and phase angle curves.

[0121] In an application scenario, such as Figure 6 As shown, based on the operation of the wind-fire bundling system at different fault stages, and combined with the equivalent model, as well as the wind turbine output and grid connection residual voltage during low-voltage ride-through of the wind-fire bundling system during the fault, the maximum electromagnetic power of the wind-fire bundling system at different fault stages is given, which may include:

[0122] Based on the reactive power injection of the wind-fire bundling system during the low voltage ride-through scenario during the fault, the wind turbine output and grid connection point residual voltage during the fault are determined.

[0123] Based on the operation of the wind-fire bundled system at different fault stages, and combined with the equivalent model, as well as the wind turbine output and grid connection point residual voltage during the fault, the interconnection reactance between the wind-fire bundled system and the thermal power unit and the infinite bus system are given for the wind-fire bundled system at different fault stages; where different fault stages include before the fault, during the fault, and after the fault.

[0124] Based on the operating parameters of the generator and the infinite bus system in the equivalent model, and combined with the interconnecting reactance between the thermal power unit and the infinite bus system, the maximum electromagnetic power of the wind-fire bundled system is given for different fault stages.

[0125] Among them, such as Figure 7 As shown, based on the operation of the wind-fired power tying system at different fault stages, and combined with the equivalent model, as well as the wind turbine output and grid connection point residual voltage during the fault, the interconnection reactance between the wind-fired power tying system and the thermal power unit at different fault stages is given, which may include:

[0126] Based on the first operating parameters of the equivalent model, the connection reactance between the thermal power unit and the infinite system in the wind-fired power bundled system is determined before and after the fault. The first operating parameters include the transient reactance of the generator, the thermal power step-up transformer, the reactance of the transmission line corresponding to the thermal power unit, the wind power step-up transformer, the reactance of the transmission line corresponding to the wind power unit, the reactance of a single line of the double-circuit transmission line, and the equivalent reactance of the infinite system.

[0127] Based on the location of the fault point, determine the equivalent additional reactance for different fault points;

[0128] Obtain the per-unit value of the residual voltage at the grid connection point of the wind farm and the per-unit value of the dynamic reactive current increment injected by the wind farm under the low voltage ride-through scenario of the wind-fire bundled system, and determine the equivalent reactance of the wind turbine during the fault period;

[0129] Based on the equivalent reactance of the wind turbine during the fault period, the equivalent additional reactance at different fault points, and combined with the first operating parameters, the connection reactance between the thermal power unit and the infinite bus system at different fault points of the wind-fire bundled system during the fault period is determined.

[0130] In practical applications, in the steady state before the fault, the wind turbine and the thermal power unit are connected in parallel through a single-circuit transmission line, and then the power is transmitted to the infinite system through a double-circuit transmission line. For the equivalent model, the star-angle transformation formula can be used to simplify the equivalent model and determine the connection reactance between the corresponding thermal power unit and the infinite system before the fault, which specifically satisfies the following relationship:

[0131]

[0132] In the formula, x Σ_b x represents the interconnecting reactance between the thermal power unit and the infinite power system prior to the fault. d 'x' represents the transient reactance of the generator; T1 For the reactance of the thermal power plant step-up transformer; x l1 Thermal power unit transmission line reactance; x T2 Reactance of wind power step-up transformer; x l2 For the reactance of the wind turbine transmission line; x l For the reactance of a single line in a double-circuit transmission line, x s It is the equivalent reactance of an infinite system.

[0133] During a fault, the requirements of national standard GB / T 19963.1 "Technical Specifications for Wind Farm Connection to Power Systems Part 1: Onshore Wind Power" must be considered and met.

[0134] During a fault, a) when a three-phase short-circuit fault occurs in the power system and the positive-sequence component of the grid connection voltage is lower than 80% of the nominal voltage, the wind farm should have dynamic reactive power support capability; b) the dynamic reactive current increment of the wind farm should respond to changes in the grid connection voltage and should meet the following requirements:

[0135]

[0136] Where: ΔI t The dynamic reactive current increment injected into the wind farm, measured in amperes (A); K I U is the dynamic reactive current proportionality coefficient for wind farms, with a value not less than 1.5 and not greater than 3. t This refers to the per-unit voltage at the wind farm's grid connection point, measured in per-unit values ​​(pu). N This is the rated current of the wind farm, expressed in amperes (A).

[0137] In practical applications, wind turbines operate under unity power factor control during normal operation, meaning they only output active power to the infinite power system, with zero reactive power output. During a fault, to prevent overcurrent in the grid-connected converter, the active power output of the wind turbine rapidly decreases, and it provides a certain amount of reactive current to the infinite power system. Considering that the resistance of the transmission line is much smaller than its reactance, the equivalent impedance x of the wind turbine in this situation... w The ratio of the residual voltage at the grid connection point of the wind turbine to the reactive current injected into the power system by the wind turbine can be used to calculate the following relationship:

[0138]

[0139] In the formula: U res This refers to the per-unit value of the residual voltage at the wind farm's grid connection point. Specifically, it is the per-unit value of the actual instantaneous voltage at the wind farm's grid connection point (i.e., the actual residual voltage at the wind farm's grid connection point) relative to its rated voltage after a fault occurs; ΔI q The per-unit value of the dynamic reactive current increment injected into the wind farm is ΔI. t .

[0140] At this point, the impact of the fault on the wind-fired power bundling system can be considered as an additional impedance x connected in parallel at the beginning of the high-voltage busbar of the wind turbine and the thermal power unit connected in parallel. Δ It satisfies the following relationship:

[0141]

[0142] In the formula, x Σ(2) The equivalent negative sequence impedance of the fire-resistant bundling system; x Σ(0) Let be the equivalent zero-sequence impedance of the wind-fire bundled system. For a single-circuit transmission line, it is approximately taken as 3 times the normal reactance; for a double-circuit line, it is approximately 4 times. In this case, the equivalent negative-sequence impedance and the equivalent zero-sequence impedance satisfy the following relationship:

[0143]

[0144] For the equivalent model, the star-angle transformation formula can be used to simplify the equivalent model and determine the interconnecting reactance between the thermal power unit and the infinite bus system for different fault points during the fault period (including unidirectional short circuit, two-phase phase-to-phase short circuit, two-phase short circuit to ground, and three-phase short circuit), satisfying the following relationship:

[0145]

[0146] In the formula, x Σ_f This represents the interconnecting reactance between the thermal power unit and the infinite bus system at different fault points during the fault period; / / indicates parallel reactance.

[0147] When the additional impedance is zero in a three-phase short-circuit scenario, the interconnecting reactance between the thermal power unit and the infinite bus system satisfies the following relationship:

[0148]

[0149] After the fault is cleared, the high-voltage busbar connecting the wind turbine and the thermal power unit in parallel is switched to single-circuit operation. The impedance of the transmission line changes, and the corresponding reactance between the thermal power unit and the infinite power system satisfies the following relationship:

[0150]

[0151] In the formula: x Σ_n This is the contact reactance between the thermal power unit and the AC power grid after the fault is cleared.

[0152] After determining the interconnecting reactance between the thermal power unit and the infinite power system at different fault points during the fault period of the wind-fire bundled system, the maximum electromagnetic power of the wind-fire bundled system at different fault stages can be given based on the operating parameters of the generator and the infinite power system in the equivalent model, combined with the interconnecting reactance between the thermal power unit and the infinite power system. Specifically, this includes:

[0153] Based on the second operating parameters of the equivalent model, and combined with the interconnecting reactance between the thermal power unit and the infinite power system before, during, and after the fault, the maximum electromagnetic power of the wind-fire bundling system is given before, during, and after the fault. The second operating parameters include the terminal voltage of the infinite power system and the internal potential of the generator.

[0154] In practical applications, the maximum electromagnetic power of the operating curves before, during, and after a fault satisfies the following relationship:

[0155]

[0156] In the formula, Pem1 P em2 P em3 These represent the maximum electromagnetic power of the operating curves before, during, and after the fault, respectively.

[0157] like Figure 8 As shown, based on the rotor motion model of a thermal power unit and combined with the maximum electromagnetic power of the wind-fire bundling system at different fault stages, the phase angles of the wind-fire bundling system at key operating points corresponding to different fault stages are given, including:

[0158] Based on the rotor motion model of thermal power units, the mechanical power, wind turbine output, generator moment of inertia, and generator speed reference values ​​of the wind-fired power bundling system in steady state are determined.

[0159] Based on the steady-state mechanical power and wind turbine output of the wind-fire bundling system, and combined with the maximum electromagnetic power of the wind-fire bundling system before the fault, the phase angle of the wind-fire bundling system at the steady-state operating point before the fault is given.

[0160] Based on the steady-state mechanical power, generator rotational inertia, fault clearing time, and wind turbine output during the fault period of the wind-fire bundling system, and combined with the phase angle of the wind-fire bundling system at the corresponding critical operating point before the fault, the fault clearing angle of the wind-fire bundling system at the fault clearing time during the fault period is given; where the wind turbine output during the fault period refers to the wind turbine output that performs low voltage ride-through during the fault period.

[0161] Based on the steady-state mechanical power and wind turbine output of the wind-fire bundling system, and combined with the maximum electromagnetic power of the wind-fire bundling system after a fault, the phase angle of the wind-fire bundling system at the corresponding unstable operating point after a fault is given.

[0162] In practical applications, to avoid overcurrent in the grid-connected converter during a fault, the active power output of the wind turbine rapidly decreases, and a certain amount of reactive current is supplied to the infinite power system. This causes a change in the wind turbine's output. At this time, the new wind turbine output during the fault can be determined based on the residual voltage at the wind turbine's grid connection point and the total current flowing from the wind turbine into the wind-fired power system, specifically satisfying the following relationship:

[0163]

[0164] In the formula: I p P is the active current of the wind turbine; I is the current limit value of the wind turbine; w 'To provide power output for wind turbines during a fault.'

[0165] Based on the new wind turbine output during a defined fault period, the phase angle at the steady-state operating point before the fault, the fault clearing angle at the fault clearance time, and the phase angle at the unstable operating point after the fault can be obtained. Specifically, the phase angles at the steady-state operating point before the fault, the fault clearing angle at the fault clearance time, and the phase angles at the unstable operating point after the fault satisfy the following relationships:

[0166]

[0167] In the formula, δ0, δ c δ r These represent the phase angle of the wind-fire bundling system at the steady-state operating point before the fault, the fault clearing angle at the fault clearing moment during the fault, and the phase angle at the unstable operating point after the fault, t. c This is the time to clear the fault.

[0168] Specifically, the phase angle of the wind-fire bundling system at the steady-state operating point before the fault, the fault clearing angle at the fault clearing moment during the fault, and the phase angle at the unstable operating point after the fault are all determined by substituting the maximum electromagnetic power of the corresponding fault stage into the rotor motion model of the thermal power unit and integrating to solve the change of the power angle over time.

[0169] Based on the power and phase angle curves of the wind-fire baling system at different fault stages, the stability margin of the wind-fire baling system with respect to the wind turbine output and the residual voltage at the grid connection point can be determined, which may include:

[0170] Determine the first difference between the mechanical power of the wind-fire bundling system in steady state and the output of the wind turbine during a fault; and give the second difference between the first difference and the maximum electromagnetic power corresponding to the fault.

[0171] Integrating the second difference with respect to the phase angle from the steady-state operating point to the fault clearing angle at the fault clearing time yields the acceleration area during the fault period;

[0172] Determine the third difference between the mechanical power of the wind-fire baling system and the output of the wind turbine in steady state; and give the fourth difference between the maximum electromagnetic power of the wind-fire baling system after a fault and the third difference.

[0173] Integrating the fourth difference with respect to the phase angle from the fault clearing angle at the fault clearing moment to the unstable operating point yields the maximum deceleration area after the fault.

[0174] Based on the difference between the maximum deceleration area after the fault and the acceleration area during the fault, the stability margin of the wind-fire bundling system with respect to the wind turbine output and the residual voltage at the grid connection point is determined.

[0175] In practical applications, the transient stability of the wind-fire bundled system can be constructed using the equal area rule to establish a stability margin expression under different wind turbine outputs and residual voltage at the grid connection point. This expression represents the acceleration area S during the fault period. 加 The maximum deceleration area S after the fault 减max Specifically, the following relationship is satisfied:

[0176]

[0177] Among them, the acceleration area during the fault is automatically captured by continuously accumulating the power difference through the integral term, and the acceleration change and curvature characteristics in the power angle swing, so as to fully consider the nonlinear power angle change under the low voltage ride-through scenario; the maximum deceleration area after the fault realizes the quantitative integration of reactive power support effect through the dynamic mapping of the residual voltage at the grid connection point and the coupled modeling of the maximum electromagnetic power.

[0178] In addition, when a three-phase short circuit occurs, P em2 =0, the acceleration area during the fault period satisfies the following relationship:

[0179]

[0180] Based on the acceleration area S during the fault 加 The maximum deceleration area S after the fault (after the fault is cleared) 减max The stability margin of the wind and fire bundling system can be obtained, specifically satisfying the following relationship:

[0181]

[0182] Correspondingly, when a three-phase short circuit occurs, the stability margin of the wind-fire bundling system can be simplified as follows:

[0183]

[0184] After determining the stability margin of the wind turbine output and grid connection point residual voltage of the wind-fired power bridging system, a transient stability boundary based on the wind turbine output and grid connection point residual voltage during a fault can be constructed, specifically including:

[0185] Obtain the wind turbine output and grid connection point residual voltage when the stability margin of the wind turbine output and grid connection point residual voltage of the wind-fire bundling system is zero;

[0186] Using the wind turbine output and grid connection point residual voltage as the horizontal and vertical axes respectively, a critical stability domain diagram is constructed with zero stability margin as the transient stability boundary. Here, zero stability margin means that the stability margin is equal to zero, and the transient stability boundary refers to the boundary that satisfies the zero stability margin. If the zero stability margin is not satisfied, it is considered to exceed the boundary.

[0187] The constructed critical stability domain diagram can provide a rapid stability criterion for the operation of wind-fire bundled systems under low-voltage ride-through scenarios. In practical applications, it can guide the operational decisions of wind-fire bundled systems, optimize wind power output and voltage control, assist in determining fault recovery strategies, and serve as a basis for theoretical verification and practical engineering design. Specifically, for guiding operational decisions, the critical stability domain diagram uses wind turbine output and grid connection residual voltage as the horizontal and vertical axes, respectively, dividing the stable region into a stable region with zero stability margin and an unstable region with non-zero stability margin. Based on real-time monitoring of wind turbine output and grid connection residual voltage, it can quickly determine whether the wind-fire bundled system is in a stable state, avoiding the risk of instability. For optimizing wind power output and voltage control in a combined wind-fired and thermal power system, during a fault, if the system approaches its stability boundary, stability can be maintained by adjusting wind turbine output (e.g., tripping or reducing power) or increasing reactive power compensation (e.g., dynamically adjusting SVG). Specifically, when the residual voltage at the grid connection point is low, wind turbine output needs to be limited to prevent the acceleration area from exceeding the deceleration area. Regarding the determination of fault recovery strategies for the combined wind-fired and thermal power system, the critical stability domain diagram can provide a reference for post-fault recovery. For example, appropriate reclosing times or tripping strategies can be selected to ensure that the wind turbine output and the residual voltage at the grid connection point are combined within a safe and stable region. As a foundation for theoretical verification and practical engineering design, it can provide theoretical support for assessing the low-voltage ride-through capability, setting protection parameters, and configuring dynamic reactive power compensation in the combined wind-fired and thermal power system.

[0188] like Figure 9 As shown, the present invention also provides a transient stability boundary construction device for a wind-fire bundling system, employing the aforementioned transient stability boundary construction method for a wind-fire bundling system. The device includes:

[0189] The model building module is used to establish an equivalent model of the wind and fire bundling system based on its structural characteristics and operational features.

[0190] The curve determination module is used to determine the power and phase angle curves of the wind-fire bundling system at different fault stages based on the operation of the wind-fire bundling system at different fault stages, combined with the equivalent model, as well as the output of the wind turbine and the residual voltage at the grid connection point during the low voltage ride-through of the wind-fire bundling system during the fault.

[0191] The index determination module is used to determine the stability margin of the wind turbine output and grid connection point residual voltage of the wind-fire bundled system based on the power and phase angle curves of the wind-fire bundled system at different fault stages.

[0192] The boundary delineation module is used to construct transient stability boundaries based on the wind turbine output and the residual pressure at the grid connection point, based on the stability margin during the fault period.

[0193] Furthermore, the model building module is also used for:

[0194] The AC power grid of the combined wind and fire system is equivalent to an infinite system.

[0195] Based on the topological relationship between wind turbines, thermal power units, and the AC power grid, the wind turbines, thermal power units, and the infinite power system are connected by lines, and an initial system model is given. The topological relationship between the wind turbines, thermal power units, and the AC power grid includes: the wind turbines and thermal power units are connected in parallel through transmission lines, and then the power is transmitted to the infinite power system through a double-circuit transmission line.

[0196] Based on the operating characteristics of the wind-fired power tying system, the operating parameters of the wind turbine, thermal power unit, infinite bus system, and transmission line in the initial system model are determined, and an equivalent model of the wind-fired power tying system is given.

[0197] Furthermore, the curve determination module is used for:

[0198] Based on the operation of the wind-fire bundling system at different fault stages, and combined with the equivalent model, as well as the wind turbine output and grid connection point residual voltage during low voltage ride-through of the wind-fire bundling system during the fault, the maximum electromagnetic power of the wind-fire bundling system at different fault stages is given.

[0199] Based on the equivalent model, a rotor motion model of a thermal power unit is constructed;

[0200] Based on the rotor motion model of thermal power units and combined with the maximum electromagnetic power of the wind-fire bundling system at different fault stages, the phase angles of the wind-fire bundling system at the corresponding key operating points at different fault stages are given.

[0201] Furthermore, the curve determination module is used for:

[0202] Based on the reactive power injection of the wind-fire bundling system during the low voltage ride-through scenario during the fault, the wind turbine output and grid connection point residual voltage during the fault are determined.

[0203] Based on the operation of the wind-fire bundled system at different fault stages, and combined with the equivalent model, as well as the wind turbine output and grid connection point residual voltage during the fault, the interconnection reactance between the wind-fire bundled system and the thermal power unit and the infinite bus system are given for the wind-fire bundled system at different fault stages; where different fault stages include before the fault, during the fault, and after the fault.

[0204] Based on the operating parameters of the generator and the infinite bus system in the equivalent model, and combined with the interconnecting reactance between the thermal power unit and the infinite bus system, the maximum electromagnetic power of the wind-fire bundled system is given for different fault stages.

[0205] Furthermore, the curve determination module is used for:

[0206] Based on the first operating parameters of the equivalent model, the connection reactance between the thermal power unit and the infinite system in the wind-fired power bundled system is determined before and after the fault. The first operating parameters include the transient reactance of the generator, the thermal power step-up transformer, the reactance of the transmission line corresponding to the thermal power unit, the wind power step-up transformer, the reactance of the transmission line corresponding to the wind power unit, the reactance of a single line of the double-circuit transmission line, and the equivalent reactance of the infinite system.

[0207] Based on the location of the fault point, determine the equivalent additional reactance for different fault points;

[0208] Obtain the per-unit value of the residual voltage at the grid connection point of the wind farm and the per-unit value of the dynamic reactive current increment injected by the wind farm under the low voltage ride-through scenario of the wind-fire bundled system, and determine the equivalent reactance of the wind turbine during the fault period;

[0209] Based on the equivalent reactance of the wind turbine during the fault period, the equivalent additional reactance at different fault points, and combined with the first operating parameters, the connection reactance between the thermal power unit and the infinite bus system at different fault points of the wind-fire bundled system during the fault period is determined.

[0210] Furthermore, the curve determination module is used for:

[0211] Based on the second operating parameters of the equivalent model, and combined with the interconnecting reactance between the thermal power unit and the infinite power system before, during, and after the fault, the maximum electromagnetic power of the wind-fire bundling system is given before, during, and after the fault. The second operating parameters include the terminal voltage of the infinite power system and the internal potential of the generator.

[0212] Furthermore, the curve determination module is also used for:

[0213] Based on the rotor motion model of thermal power units, the mechanical power, wind turbine output, generator moment of inertia, and generator speed reference values ​​of the wind-fired power bundling system in steady state are determined.

[0214] Based on the steady-state mechanical power and wind turbine output of the wind-fire bundling system, and combined with the maximum electromagnetic power of the wind-fire bundling system before the fault, the phase angle of the wind-fire bundling system at the steady-state operating point before the fault is given.

[0215] Based on the steady-state mechanical power, generator rotational inertia, fault clearing time, and wind turbine output during the fault of the wind-fire bundling system, and combined with the phase angle of the wind-fire bundling system at the corresponding critical operating point before the fault, the fault clearing angle of the wind-fire bundling system at the corresponding fault clearing time during the fault is given.

[0216] Based on the steady-state mechanical power and wind turbine output of the wind-fire bundling system, and combined with the maximum electromagnetic power of the wind-fire bundling system after a fault, the phase angle of the wind-fire bundling system at the corresponding unstable operating point after a fault is given.

[0217] Furthermore, the indicator determination module is also used for:

[0218] Determine the first difference between the mechanical power of the wind-fire bundling system in steady state and the output of the wind turbine during a fault; and give the second difference between the first difference and the maximum electromagnetic power corresponding to the fault.

[0219] Integrating the second difference with respect to the phase angle from the steady-state operating point to the fault clearing angle at the fault clearing time yields the acceleration area during the fault period;

[0220] Determine the third difference between the mechanical power of the wind-fire baling system and the output of the wind turbine in steady state; and give the fourth difference between the maximum electromagnetic power of the wind-fire baling system after a fault and the third difference.

[0221] Integrating the fourth difference with respect to the phase angle from the fault clearing angle at the fault clearing moment to the unstable operating point yields the maximum deceleration area after the fault.

[0222] Based on the difference between the maximum deceleration area after the fault and the acceleration area during the fault, the stability margin of the wind-fire bundling system with respect to the wind turbine output and the residual voltage at the grid connection point is determined.

[0223] Furthermore, the boundary delimitation module is also used for:

[0224] Obtain the wind turbine output and grid connection point residual voltage when the stability margin of the wind turbine output and grid connection point residual voltage of the wind-fire bundling system is zero;

[0225] Using the wind turbine output and grid connection point residual voltage as the horizontal and vertical axes respectively, a critical stability domain diagram is constructed, with zero-value stability margin as the transient stability boundary.

[0226] 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. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A method for constructing the transient stability boundary of a wind-fire bundling system, characterized in that, include: Based on the structural characteristics and operational features of the wind-fire bundling system, an equivalent model of the wind-fire bundling system is established. Based on the reactive power injection of the wind-fire bundling system during the low voltage ride-through scenario during the fault, the wind turbine output and grid connection point residual voltage during the fault are determined. Based on the first operating parameters of the equivalent model, the connection reactance between the thermal power unit and the infinite bus system in the wind-fire bundled system is determined before and after the fault. The first operating parameters include the transient reactance of the generator, the thermal power step-up transformer, the reactance of the transmission line corresponding to the thermal power unit, the wind power step-up transformer, the reactance of the transmission line corresponding to the wind power unit, the reactance of a single line of the double-circuit transmission line, and the equivalent reactance of the infinite bus system. Based on the location of the fault point, the equivalent additional reactance at different fault points is determined. The per-unit value of the residual voltage at the wind farm grid connection point and the per-unit value of the dynamic reactive current increment injected by the wind farm are obtained in the low voltage ride-through scenario to determine the equivalent reactance of the wind power unit during the fault. Based on the equivalent reactance of the wind power unit during the fault, the equivalent additional reactance at different fault points, and combined with the first operating parameters, the connection reactance between the thermal power unit and the infinite bus system corresponding to different fault points in the wind-fire bundled system during the fault is determined. Based on the operating parameters of the generator and the infinite system in the equivalent model, and combined with the interconnecting reactance between the thermal power unit and the infinite system, the maximum electromagnetic power of the wind-fire bundled system is given for different fault stages; where different fault stages include before the fault, during the fault, and after the fault. Based on the equivalent model, a rotor motion model of a thermal power unit is constructed; Based on the rotor motion model of thermal power units and combined with the maximum electromagnetic power of the wind-fire bundling system at different fault stages, the phase angles of the wind-fire bundling system at the corresponding key operating points at different fault stages are given. Based on the power and phase angle curves of the wind-fire bundling system at different fault stages, the stability margin of the wind-fire bundling system with respect to the wind turbine output and the residual voltage at the grid connection point is determined. Based on the stability margin during the fault period, a transient stability boundary is constructed based on the wind turbine output and the residual voltage at the grid connection point.

2. The transient stability boundary construction method as described in claim 1, characterized in that, Based on the structural characteristics and operational features of the wind-fire bundling system, an equivalent model of the wind-fire bundling system is established, including: The AC power grid of the combined wind and fire system is equivalent to an infinite system. Based on the topological relationship between wind turbines, thermal power units, and the AC power grid, the wind turbines, thermal power units, and the infinite power system are connected by lines, and an initial system model is given. The topological relationship between the wind turbines, thermal power units, and the AC power grid includes: the wind turbines and thermal power units are connected in parallel through transmission lines, and then the power is transmitted to the infinite power system through a double-circuit transmission line. Based on the operating characteristics of the wind-fired power tying system, the operating parameters of the wind turbine, thermal power unit, infinite bus system, and transmission line in the initial system model are determined, and an equivalent model of the wind-fired power tying system is given.

3. The transient stability boundary construction method as described in claim 1, characterized in that, Based on the operating parameters of the generator and the infinite power system in the equivalent model, and combined with the interconnecting reactance between the thermal power unit and the infinite power system, the maximum electromagnetic power of the wind-fired power system at different fault stages is given, including: Based on the second operating parameters of the equivalent model, and combined with the interconnecting reactance between the thermal power unit and the infinite power system before, during, and after the fault, the maximum electromagnetic power of the wind-fire bundling system is given before, during, and after the fault. The second operating parameters include the terminal voltage of the infinite power system and the internal potential of the generator.

4. The transient stability boundary construction method as described in claim 1, characterized in that, Based on the rotor motion model of a thermal power unit and combined with the maximum electromagnetic power of the air-fire bundling system at different fault stages, the phase angles of the air-fire bundling system at key operating points corresponding to different fault stages are given, including: Based on the rotor motion model of thermal power units, the mechanical power, wind turbine output, generator moment of inertia, and generator speed reference values ​​of the wind-fired power bundling system in steady state are determined. Based on the steady-state mechanical power and wind turbine output of the wind-fire bundling system, and combined with the maximum electromagnetic power of the wind-fire bundling system before the fault, the phase angle of the wind-fire bundling system at the steady-state operating point before the fault is given. Based on the steady-state mechanical power, generator rotational inertia, fault clearing time, and wind turbine output during the fault of the wind-fire bundling system, and combined with the phase angle of the wind-fire bundling system at the corresponding critical operating point before the fault, the fault clearing angle of the wind-fire bundling system at the corresponding fault clearing time during the fault is given. Based on the steady-state mechanical power and wind turbine output of the wind-fire bundling system, and combined with the maximum electromagnetic power of the wind-fire bundling system after a fault, the phase angle of the wind-fire bundling system at the corresponding unstable operating point after a fault is given.

5. The transient stability boundary construction method as described in claim 4, characterized in that, Based on the power and phase angle curves of the wind-fire baling system at different fault stages, the stability margin of the wind-fire baling system with respect to the wind turbine output and the residual voltage at the grid connection point is determined, including: Determine the first difference between the mechanical power of the wind-fire bundling system in steady state and the output of the wind turbine during a fault; and give the second difference between the first difference and the maximum electromagnetic power corresponding to the fault. Integrating the second difference with respect to the phase angle from the steady-state operating point to the fault clearing angle at the fault clearing time yields the acceleration area during the fault period; Determine the third difference between the mechanical power of the wind-fire baling system and the output of the wind turbine in steady state; and give the fourth difference between the maximum electromagnetic power of the wind-fire baling system after a fault and the third difference. Integrating the fourth difference with respect to the phase angle from the fault clearing angle at the fault clearing moment to the unstable operating point yields the maximum deceleration area after the fault. Based on the difference between the maximum deceleration area after the fault and the acceleration area during the fault, the stability margin of the wind-fire bundling system with respect to the wind turbine output and the residual voltage at the grid connection point is determined.

6. The transient stability boundary construction method as described in any one of claims 1 to 5, characterized in that, Based on the stability margin during the fault period, a transient stability boundary is constructed based on the wind turbine output and the residual voltage at the grid connection point, including: Obtain the wind turbine output and grid connection point residual voltage when the stability margin of the wind turbine output and grid connection point residual voltage of the wind-fire bundling system is zero; Using the wind turbine output and grid connection point residual voltage as the horizontal and vertical axes respectively, a critical stability domain diagram is constructed, with zero-value stability margin as the transient stability boundary.

7. A transient stability boundary construction device for a wind-fire bundling system, characterized in that, The apparatus employing the transient stability boundary construction method for the wind-fire bundling system as described in any one of claims 1 to 6 includes: The model building module is used to establish an equivalent model of the wind and fire bundling system based on its structural characteristics and operational features. The curve determination module is used to determine the power and phase angle curves of the wind-fire bundling system at different fault stages based on the operation of the wind-fire bundling system at different fault stages, combined with the equivalent model, as well as the output of the wind turbine and the residual voltage at the grid connection point during the low voltage ride-through of the wind-fire bundling system during the fault. The index determination module is used to determine the stability margin of the wind turbine output and grid connection point residual voltage of the wind-fire bundled system based on the power and phase angle curves of the wind-fire bundled system at different fault stages. The boundary delineation module is used to construct transient stability boundaries based on the wind turbine output and the residual pressure at the grid connection point, based on the stability margin during the fault period.

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