A method and device for depicting voltage stable operation domain of a new energy sending-out system

Abstract

The application discloses a voltage stable operation domain delineation method and device of a new energy sending-out system, relates to the technical field of power system stability analysis, and aims at the technical problem that the system voltage stability boundary is difficult to delineate after high proportion of new energy is connected to a weak sending-end power grid. A three-dimensional state space surface composed of grid-connected point voltage, active power and reactive power is constructed, and preset high / low voltage ride-through thresholds, converter capacity and active power margin are mapped to quantifiable geometric boundaries on the power plane. Then, the intersection relationship between the power margin boundary and the voltage boundary is used to determine the critical short-circuit ratio. Finally, the numerical comparison between the critical short-circuit ratio and the actual short-circuit ratio is used to determine the dominance of each boundary and filter out effective boundary combinations to form a voltage stable operation domain, so that the accurate quantification and partition delineation of the voltage stable operation boundary of the weak sending-end power grid under all working conditions are realized, and clear boundary basis is provided for voltage support control strategy formulation and stability margin evaluation.

Description

Technical Field

[0001] This invention relates to the field of power system stability analysis technology, and more specifically, to a method and apparatus for characterizing the voltage stability operating domain of a new energy transmission system. Background Technology

[0002] With the high proportion of renewable energy integrated into the grid, the nonlinear control characteristics of power electronic equipment have made voltage stability issues in renewable energy transmission systems increasingly prominent. In grids dominated by conventional synchronous generators, the voltage stability domain boundary is usually determined by the power transmission limit caused by load growth, which can be quantitatively analyzed using PV curves and continuous power flow methods. However, in high-proportion renewable energy transmission systems, factors such as phase-locked loop dynamics, current limiting, and fault ride-through control cause the system PV curve to exhibit piecewise discontinuous characteristics, and the voltage stability boundary shows significant non-smoothness and nonlinearity. Existing active voltage support research has not clearly characterized the voltage stability operating region under such complex constraints, resulting in an unclear voltage stability boundary. Consequently, the design of voltage support control parameters lacks precise basis, making it difficult to ensure the safe and stable transmission of renewable energy. Summary of the Invention

[0003] The purpose of this invention is to address the technical problem of difficulty in characterizing the voltage stability boundary of a system after a high proportion of new energy sources are connected to a weak-sending-end power grid. It proposes a method and apparatus for characterizing the voltage stability operating domain of a new energy transmission system. This method constructs a three-dimensional state space surface composed of grid connection point voltage, active power, and reactive power. Preset high / low voltage ride-through thresholds, converter capacity, and active power margin are mapped onto the power plane as quantifiable geometric boundaries. The critical short-circuit ratio is determined by the intersection of the power margin boundary and the voltage boundary. Finally, the dominance of each boundary is determined by comparing the critical short-circuit ratio with the actual short-circuit ratio, and effective boundary combinations are selected to enclose and form the voltage stability operating domain. This achieves accurate quantification and partitioning of the voltage stability operating boundary of the weak-sending-end power grid under all operating conditions, providing clear boundary basis for voltage support control strategy formulation and stability margin assessment.

[0004] In a first aspect, one technical solution provided in the embodiments of the present invention is: a method for characterizing the voltage stability operating domain of a new energy transmission system, comprising the following steps: A three-dimensional state space surface is established based on the power flow equation of the renewable energy transmission system, consisting of the renewable energy grid connection point voltage, the transmitted active power, and the transmitted reactive power. The preset voltage ride-through threshold, converter capacity, and active power margin are respectively mapped to the voltage boundary, capacity boundary, and power margin boundary of the three-dimensional state space surface on the power plane. Based on the intersection relationship between the power margin boundary and the voltage boundary on the power plane, the critical short-circuit ratio of the new energy transmission system under different voltage thresholds is determined; Based on the numerical comparison results between the critical short-circuit ratio and the actual system short-circuit ratio, an effective boundary combination constituting the voltage stable operating domain on the power plane is determined from the voltage boundary, capacity boundary, and power margin boundary. The voltage stable operating domain of the new energy transmission system is characterized according to the effective boundary combination.

[0005] Preferably, the step of establishing a three-dimensional state space surface composed of the grid connection point voltage of the new energy source, the transmitted active power, and the transmitted reactive power based on the power flow equation of the new energy transmission system is as follows: An equivalent circuit model is constructed based on the receiving-end equivalent electromotive force and the transmitting-line equivalent reactance of the new energy transmission system. Based on the equivalent circuit model, the power flow equation is determined according to the mathematical relationship between the voltage, active power and reactive power of the new energy grid connection point. All feasible solutions to the power flow equations are solved within the three-dimensional spatial constraints consisting of the voltage, active power, and reactive power to construct the three-dimensional state space surface; the three-dimensional state space surface is used to characterize the global operating trajectory of the voltage at the grid connection point of the new energy source as the power output changes.

[0006] Preferably, the construction of the voltage boundary specifically includes: The normalized voltage amplitude of the new energy grid connection point is limited to between a preset low voltage ride-through threshold and a high voltage ride-through threshold, and a first voltage boundary corresponding to the low voltage ride-through threshold and a second voltage boundary corresponding to the high voltage ride-through threshold are determined in the power plane; the first voltage boundary and the second voltage boundary together define the effective operating voltage range of the new energy grid connection point voltage in the power plane.

[0007] Preferably, the construction of the capacity boundary specifically includes: The apparent power limit of the converter is determined based on the capacity of the grid-connected converter. A capacity constraint equation between the active power and reactive power of the new energy grid-connected point is established based on the apparent power limit of the converter. The capacity constraint equation indicates that the sum of the squares of the active power and the squares of the reactive power does not exceed the square of the apparent power limit of the converter. Thus, on the power plane constructed with active power as the horizontal axis and reactive power as the vertical axis, the operable power point of the new energy grid-connected point is limited to the area inside a circle with the origin of the power plane as the center and the apparent power limit of the converter as the radius. The circumferential boundary of the area inside the circle is taken as the capacity boundary.

[0008] Preferably, the construction of the power margin boundary specifically includes: The active power margin coefficient is determined based on the ratio of the current active power of the new energy grid connection point to the reserved power reserve ratio between the current active power and the system active power transmission limit. On the three-dimensional state space surface, the active power transmission limit value corresponding to each reactive power value is solved along the reactive power change path; The active power transmission limit value is reduced by the active power margin coefficient to obtain the active power reduction value corresponding to each reactive power value. The set of power margin boundary points on the power plane is constructed by the reactive power value and the active power reduction value. The power margin boundary is constructed by sequentially connecting the points in the power margin boundary point set.

[0009] Preferably, the critical short-circuit ratio includes a first short-circuit ratio characterizing the system short-circuit capacity level at the intersection of the power margin boundary and the high-voltage crossing threshold boundary, and a second short-circuit ratio characterizing the system short-circuit capacity level at the intersection of the power margin boundary and the high-voltage crossing threshold boundary; the steps for determining the critical short-circuit ratio are as follows: On the power plane, a first intersection point between the power margin boundary and the first voltage boundary is determined, and the first short-circuit ratio corresponding to the first intersection point is calculated based on the coordinate value of the first intersection point on the power plane. A second intersection point between the power margin boundary and the second voltage boundary is determined on the power plane, and the second short-circuit ratio corresponding to the second intersection point is calculated based on the coordinate value of the second intersection point on the power plane.

[0010] Preferably, the steps for characterizing the voltage stable operating domain include: When the actual system short-circuit ratio is greater than the first short-circuit ratio, the voltage stable operating region is determined to be a first type of region enclosed by the first voltage boundary, the second voltage boundary, and the capacity boundary. When the actual system short-circuit ratio is less than the second short-circuit ratio, the voltage stable operating region is determined to be a third type of region enclosed by the first voltage boundary, the second voltage boundary and the power margin boundary; When the actual system short-circuit ratio is between the first short-circuit ratio and the second short-circuit ratio, the voltage stable operating region is determined to be a second type of region jointly enclosed by the first voltage boundary, the second voltage boundary, the capacity boundary, and the power margin boundary.

[0011] Secondly, an embodiment of the present invention also provides a technical solution: a voltage stable operating domain characterization device, applicable to the method described in the first aspect, comprising: The surface construction module establishes a three-dimensional state space surface based on the power flow equation of the renewable energy transmission system, consisting of the renewable energy grid connection point voltage, the transmitted active power, and the transmitted reactive power. The boundary mapping module maps the preset voltage crossover threshold, converter capacity, and active power margin to the voltage boundary, capacity boundary, and power margin boundary of the three-dimensional state space surface on the power plane, respectively. The short-circuit ratio determination module determines the critical short-circuit ratio of the new energy transmission system under different voltage thresholds based on the intersection relationship between the power margin boundary and the voltage boundary on the power plane. The operating domain characterization module, based on the numerical comparison results between the critical short-circuit ratio and the actual system short-circuit ratio, determines the effective boundary combination constituting the voltage stable operating domain on the power plane from the voltage boundary, capacity boundary and power margin boundary, and characterizes the voltage stable operating domain of the new energy transmission system according to the effective boundary combination.

[0012] Thirdly, one technical solution provided in the embodiments of the present invention is: an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the method as described in any one of the first aspects when it calls the computer program in the memory.

[0013] Fourthly, one technical solution provided in this embodiment of the invention is: a storage medium storing computer-executable instructions, wherein when the computer-executable instructions are loaded and executed by a processor, the steps of the method as described in any one of the first aspects are implemented.

[0014] This invention offers at least the following substantial benefits: By establishing a three-dimensional state-space surface composed of voltage, active power, and reactive power, and mapping multiple physical constraints such as voltage ride-through threshold, converter capacity, and active power margin onto a two-dimensional power plane, this application solves the problem of non-smooth and difficult-to-quantify stability boundaries caused by nonlinear control of power electronic equipment in high-proportion renewable energy systems. By analyzing the geometric intersection relationship between the power margin boundary and the voltage boundary, the critical short-circuit ratio is determined, revealing the decisive mechanism of network strength on the stability domain topology. Based on the numerical comparison of the actual system's short-circuit ratio and the critical short-circuit ratio, three types of voltage stability operating domains composed of different boundary combinations are adaptively identified, realizing a shift from a single fixed boundary to dynamic partitioning. This method not only clarifies the true safe operating range of the system under different operating conditions of strong and weak networks but also provides accurate quantitative basis for the differentiated tuning of voltage support control parameters, effectively improving the voltage safety and stability level of renewable energy transmission systems.

[0015] The above description of the invention is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0016] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings. The drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0017] Figure 1 This is a flowchart of a method for characterizing the voltage stability operating domain of a new energy transmission system according to an embodiment of this application; Figure 2 This is a schematic diagram of the three-dimensional state space surface of the new energy transmission system according to an embodiment of this application; Figure 3 This is a schematic diagram of the PV plane voltage stable operating domain according to an embodiment of this application; Figure 4 This is a schematic diagram of the boundary of the PQ plane voltage stable operating domain according to an embodiment of this application; Figure 5 This is a schematic diagram of the voltage stability operating domain characterization device of the new energy transmission system according to an embodiment of this application. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only one preferred embodiment of this invention and are only used to explain this invention. They do not limit the scope of protection of this invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0019] Before discussing the exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe the operations (or steps) as sequential processes, many of the operations (or steps) can be performed in parallel, concurrently, or simultaneously. Furthermore, the order of the operations can be rearranged. The process can be terminated when its operation is completed, but it may also have additional steps not included in the figures; the process may correspond to a method, function, procedure, subroutine, subroutine, etc.

[0020] Example 1: As Figure 1As shown, one technical solution provided in this embodiment of the invention is: a method for characterizing the voltage stable operating domain of a new energy transmission system. By analyzing the geometric shape and evolution law of the voltage stable operating domain under different network strengths, the partition characterization based on the critical short-circuit ratio can reflect the safety boundary of the new energy transmission system under different operating conditions, reduce the stability domain estimation deviation caused by ignoring constraint coupling, and provide a quantitative basis for the formulation of voltage control strategies. The specific method is shown in steps S100~S400.

[0021] Step S100: Establish a three-dimensional state space surface based on the power flow equation of the new energy transmission system, consisting of the voltage at the new energy grid connection point, the transmitted active power, and the transmitted reactive power.

[0022] Understandably, traditional PV curve analysis only examines the relationship between voltage and active power on a two-dimensional plane, which is difficult to fully reflect the impact of reactive power on voltage stability. This embodiment establishes a state space surface in three-dimensional space to fully describe the operating characteristics of the system.

[0023] As an optional embodiment, step S100 is specifically implemented as follows: First, an equivalent circuit model is constructed based on the equivalent electromotive force at the receiving end of the new energy transmission system and the equivalent reactance of the transmission line; based on the equivalent circuit model, the power flow equation is determined according to the mathematical relationship between the voltage, active power and reactive power at the new energy grid connection point; subsequently, all feasible solutions of the power flow equation are solved in the three-dimensional spatial constraints composed of voltage, active power and reactive power to construct a three-dimensional state space surface.

[0024] As an optional embodiment, the specific steps for determining the power flow equations based on the equivalent circuit model are as follows: Let the voltage phasor at the new energy grid connection point be... The equivalent electromotive force phasor at the receiving end is Equivalent reactance of the transmitting line (Ignoring resistance), the line current phasor is Then the equivalent circuit satisfies the voltage balance equation. Complex power is defined by the grid connection point power. = Eliminating the current phasor, we can obtain the voltage amplitude V at the grid connection point and the active power. reactive power The power flow equations between them are: + The equation is about The discriminant of a quadratic equation in one variable is: ,when When the equation has a real solution, the corresponding system at that operating point ( , It can maintain voltage stability under these conditions; when When the equation has no real solution, the corresponding system at that operating point ( , Under these conditions, voltage stability cannot be maintained; under conditions determined by voltage V and active power... and reactive power By traversing all feasible solutions of the equations in the constructed three-dimensional space, the three-dimensional state space surface can be constructed.

[0025] like Figure 2 As shown, the system operating state is derived from the power flow equation of the new energy transmission system. The waistline of a three-dimensional state space surface, defined by a normalized voltage. With normalized active power as the vertical axis. and normalized reactive power With the horizontal axis as the axis, the overall shape presents a nose-shaped curved surface. Among them, For the voltage amplitude at the grid connection point of new energy sources, The equivalent electromotive force amplitude of the receiving-end synchronous generator set and its connected power grid is given. The active power injected into the transmission network from the new energy grid connection point. The reactive power injected into the transmission network from the new energy grid connection point. Equivalent reactance of the transmission channel between the grid connection point and the equivalent power source. Horizontal axis. To deliver active power relative to a power reference Normalized value, horizontal axis This represents the normalized value of reactive power output relative to a common benchmark. The horizontal axis reflects the level of active power output relative to the network's equivalent transmission capacity, and the vertical axis reflects the level of reactive power injection or absorption relative to that capacity. The voltage amplitude at the new energy grid connection point is the ratio of the voltage amplitude at the receiving end to the equivalent electromotive force amplitude, reflecting the rise or fall of the grid connection point voltage relative to the equivalent power supply voltage. A three-dimensional state-space surface characterizes the global operating trajectory of the new energy grid connection point voltage as the transmitted power changes. Each point on the surface corresponds to a steady-state operating point satisfying the power flow equations, and the surface edges correspond to the theoretical transmission limit of the system under given network parameters. This embodiment, through three-dimensional modeling, extends voltage stability analysis from a single active-voltage plane to a full-state space of active-reactive-voltage, providing a geometric basis for subsequent mapping under multiple constraints.

[0026] Step S200: Map the preset voltage ride-through threshold, converter capacity, and active power margin to the voltage boundary, capacity boundary, and power margin boundary of the three-dimensional state space surface on the power plane, respectively.

[0027] It is understood that in this embodiment, various physical constraints are projected onto the power plane to form corresponding geometric boundaries, thereby defining the area where the system can operate.

[0028] As an optional embodiment, for the construction of voltage boundaries, the normalized voltage amplitude of the new energy grid connection point is limited to between a preset low voltage ride-through threshold and a high voltage ride-through threshold, and a first voltage boundary corresponding to the low voltage ride-through threshold and a second voltage boundary corresponding to the high voltage ride-through threshold are determined in the power plane.

[0029] like Figure 4 As shown, the first and second voltage boundaries are represented by two specific curves or straight line segments on the PQ plane, which together define the effective operating range of the grid connection point voltage of new energy sources in the power plane. Within the region between these two boundaries, the grid connection point voltage is not lower than the low voltage crossover threshold. And not higher than the high voltage ride-through threshold It meets the safety standards for power grid fault ride-through.

[0030] As an optional embodiment, for the construction of the capacity boundary, the apparent power upper limit of the converter is determined based on the capacity of the grid-connected converter, and a capacity constraint equation between the active power and reactive power of the new energy grid connection point is established based on the apparent power upper limit of the converter. This capacity constraint equation indicates that the sum of the squares of the active power and the squares of the reactive power does not exceed the square of the apparent power upper limit of the converter.

[0031] As an optional representation, the capacity constraint equation can be expressed as: ,in, This represents the upper limit of apparent power determined by the capacity parameters of the grid-connected converter. The capacity constraint equation characterizes the active power of the new energy grid connection point. With reactive power The sum of the squares does not exceed the square of the apparent power limit of the converter. (This is based on the active power...) The horizontal axis represents reactive power. On the power plane constructed with the vertical axis as the ordinate, the equations correspond to a circle centered at the origin and with... The circumferential boundary of the region within a circle of radius is: That is, the capacity boundary.

[0032] Specifically, on a power plane constructed with active power as the horizontal axis and reactive power as the vertical axis, the operable power point of the new energy grid connection is limited to an area within a circle centered at the origin of the power plane and with the upper limit of the apparent power of the converter as the radius. The circumferential boundary of this area is taken as the capacity boundary. For example... Figure 4 As shown by the arc segment in the figure, this boundary is determined by the thermal limit and current withstand capability of the power electronic equipment, and is a hard constraint independent of the grid conditions.

[0033] As an optional embodiment, the active power margin coefficient is determined based on the reserved power reserve ratio between the current active power of the new energy grid connection point and the system active power transmission limit when constructing the power margin boundary.

[0034] In this embodiment, the active power margin factor is denoted as Its physical meaning is the ratio of the difference between the critical active power and the current active power to the current active power. For example, according to relevant safety and stability calculation specifications, it is the active power margin of the regional load under normal operation or maintenance mode under the maximum regional load or cross-sectional power flow. It should be greater than 8%. Setting the active power output constraint at the new energy grid connection point to 8% yields the new energy power transmission limit boundary considering the active power margin constraint, which can be expressed as: In the formula, , These represent the active and reactive power delivered by the new energy source, respectively; E is the equivalent electromotive force amplitude of the synchronous generator set; and X is the equivalent reactance of the transmission channel between the grid connection point and the equivalent power source.

[0035] Next, on the three-dimensional state space surface, the active power transmission limit value corresponding to each reactive power value is solved along the reactive power change path; the active power transmission limit value is reduced by the active power margin coefficient to obtain the active power reduction value corresponding to each reactive power value, and the power margin boundary point set on the power plane is constructed by the reactive power value and the active power reduction value; the points in the power margin boundary point set are connected in sequence to construct the power margin boundary.

[0036] Understandably, considering active power margin constraints, grid-connected converter capacity constraints, and high / low voltage ride-through threshold constraints, characterizing the voltage stability domain of the renewable energy transmission system within ( , Planar projection. Wherein, Figure 3 For the system voltage stability domain in ( , Plane projection, Figure 4 For the system voltage stability domain in ( (V) Plane projection. Limit boundary of renewable energy power transmission considering active power margin constraints. , for: In the formula, , Representing the given normalized voltages At that time, the normalized active power coordinates and normalized reactive power coordinates of the same operating point on the active power margin boundary; The dimensionless active power loading ratio, obtained from the set active power margin, represents the active power amplification factor required to reach the critical boundary along the defined path to meet the preset active power margin requirement. Specifically... ; The normalized voltage amplitude at the grid connection point used to traverse the margin boundary is the ratio of V to E, and is not another independent supply voltage. Dimensionless auxiliary quantities introduced to simplify analytical expressions do not correspond to independent device parameters or new constraints, and are specifically defined as follows: ,in The normalized voltage amplitude at the grid connection point is used to traverse the margin boundary, and its value range is... The calculation results of active and reactive power jointly determine a boundary point that satisfies the preset active power margin. The upper and lower voltage limits are used to define the effective range of this boundary; therefore, the formula itself is an active power margin constraint. The power margin boundary constructed through the above parameterization method is as follows: Figure 4 The dotted lines in the diagram represent the maximum active-reactive power combination that the system can withstand after retaining the specified safety margin.

[0037] Step S300: Determine the critical short-circuit ratio of the new energy transmission system under different voltage thresholds based on the intersection relationship between the power margin boundary and the voltage boundary on the power plane.

[0038] In this embodiment, the critical short-circuit ratio is used to distinguish different stability domain morphologies and reflect the switching conditions of the constraint-dominant mechanism as the network strength changes.

[0039] Specifically, the critical short-circuit ratio includes a first short-circuit ratio and a second short-circuit ratio. The first short-circuit ratio characterizes the system short-circuit capacity level at the intersection of the power margin boundary and the low voltage crossing threshold boundary; the second short-circuit ratio characterizes the system short-circuit capacity level at the intersection of the power margin boundary and the high voltage crossing threshold boundary.

[0040] The specific steps for determining the critical short-circuit ratio are as follows: Determine the first intersection point of the power margin boundary and the first voltage boundary on the power plane (e.g., Figure 4 Point A in the diagram is used to calculate the first short-circuit ratio corresponding to the first intersection point based on its coordinates on the power plane. Determine the second intersection point of the power margin boundary and the second voltage boundary on the power plane (e.g., Figure 4 Point B in the diagram), the second short-circuit ratio corresponding to the second intersection point is calculated based on the coordinates of the second intersection point on the power plane. These two critical short-circuit ratios quantify the network strength level at which the dominant relationship between active power margin constraints and voltage ride-through constraints shifts. As network strength changes, the main factors limiting system output will switch between equipment capacity, voltage safety, and power reserve. and This refers to the quantitative indicators used to determine the switching conditions.

[0041] Specifically, the system short-circuit ratio corresponding to the intersection of the active power margin boundary and the voltage crossing threshold boundary can be expressed as: In the formula, SCR is the dimensionless short-circuit ratio used for this boundary classification. The normalized voltage threshold selected when calculating the boundary intersection points. In order to make the corresponding The dimensionless parameter obtained by substituting the auxiliary quantity definition is specifically defined as follows: .

[0042] Step S400: Based on the numerical comparison results of the critical short-circuit ratio and the actual system short-circuit ratio, determine the effective boundary combination that constitutes the voltage stable operating domain on the power plane from the voltage boundary, capacity boundary and power margin boundary, and characterize the voltage stable operating domain of the new energy transmission system according to the effective boundary combination.

[0043] In this embodiment, the effective boundary combination of the stability region is determined based on the comparison results of the short-circuit ratio, including the following three cases: Scenario 1: When the actual system short-circuit ratio is greater than the first short-circuit ratio At that time, the voltage stable operating region is determined to be the first type of region enclosed by the first voltage boundary, the second voltage boundary, and the capacity boundary. Corresponding to... Figure 4 The region enclosed by the GMAH (Government Power Regulator) is considered. At this point, the grid strength is relatively high, voltage support is sufficient, and the power margin boundary lies outside the capacity boundary. The system can consistently meet the preset active power margin requirements before reaching the equipment capacity limit. The dominant constraints limiting system operation are converter capacity limits and voltage ride-through thresholds; power margin constraints do not constitute an effective boundary.

[0044] Scenario 2: When the actual system short-circuit ratio is less than the second short-circuit ratio At that time, the voltage stable operating region is determined to be a third type of region bounded by the first voltage boundary, the second voltage boundary, and the power margin boundary. Corresponding to Figure 4 The voltage stability region is enclosed by GBAH. At this point, the power grid is extremely weak, and voltage stability becomes the primary concern. The power margin boundary shrinks inward to the inside of the capacity boundary; before reaching the equipment capacity limit, the system is already constrained by its inability to meet active power margin requirements. In a weak grid environment, to ensure sufficient power regulation margin to cope with voltage fluctuations, it is necessary to actively reduce the upper limit of active power output. Therefore, the power margin boundary replaces the capacity boundary as the primary constraint limiting output.

[0045] Scenario 3: When the actual system short-circuit ratio is between the first short-circuit ratio Second short-circuit ratio When this period is in between, the voltage stable operating region is determined to be the second type of region jointly enclosed by the first voltage boundary, the second voltage boundary, the capacity boundary, and the power margin boundary. Corresponding to... Figure 4 The region enclosed by GCDAH. At this point, the grid strength is at a moderate level, belonging to a transitional state. Within this interval, the capacity boundary and the power margin boundary intersect on the power plane (e.g., Figure 4 Point D in the equation (referring to the boundary conditions) and the capacity boundary act as constraints in different power factor ranges. In the low power factor region, the capacity boundary plays a dominant role; in the high power factor region, the power margin boundary plays a dominant role. The final stability region is a composite region formed by the joint cutting of these four types of boundaries.

[0046] Example 2: An optional embodiment also provided in this embodiment of the invention: a voltage stable operating domain characterization device, applicable to the method described in the first embodiment, such as... Figure 5 As shown, it includes: The surface construction module establishes a three-dimensional state space surface based on the power flow equation of the renewable energy transmission system, consisting of the renewable energy grid connection point voltage, the transmitted active power, and the transmitted reactive power. The boundary mapping module maps the preset voltage crossover threshold, converter capacity, and active power margin to the voltage boundary, capacity boundary, and power margin boundary of the three-dimensional state space surface on the power plane, respectively. The short-circuit ratio determination module determines the critical short-circuit ratio of the new energy transmission system under different voltage thresholds based on the intersection relationship between the power margin boundary and the voltage boundary on the power plane. The operating domain characterization module, based on the numerical comparison results between the critical short-circuit ratio and the actual system short-circuit ratio, determines the effective boundary combination constituting the voltage stable operating domain on the power plane from the voltage boundary, capacity boundary and power margin boundary, and characterizes the voltage stable operating domain of the new energy transmission system according to the effective boundary combination.

[0047] In this embodiment, the surface construction module first constructs a three-dimensional state space surface based on system parameters. This surface fully depicts all feasible operating trajectories of the new energy grid connection point voltage as the transmitted power changes. The boundary mapping module superimposes three types of engineering constraints—high / low voltage cross-through threshold, converter capacity, and active power margin—onto the same power plane as geometric boundaries, enabling the physical constraints required for stable system operation to be uniformly represented in geometric space. The short-circuit ratio determination module further utilizes the intersection relationship between the power margin boundary and the voltage boundary to calculate the critical short-circuit ratio. This critical short-circuit ratio quantitatively reflects the alternating dominance conditions of each constraint boundary on the power plane. Finally, the operating domain characterization module automatically identifies and selects effective boundary combinations to enclose a voltage-stable operating domain based on the positional relationship between the actual short-circuit ratio and the critical short-circuit ratio. By uniformly mapping multiple heterogeneous constraints to the power plane and transforming the geometric boundary intersection relationship into a criterion for operating domain boundary selection through the critical short-circuit ratio as a numerical bridge, the voltage safety and stability level of the new energy transmission system is effectively improved.

[0048] Thirdly, one technical solution provided in the embodiments of the present invention is: an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the method as described in any one of the first aspects when it calls the computer program in the memory.

[0049] Fourthly, one technical solution provided in this embodiment of the invention is: a storage medium storing computer-executable instructions, wherein when the computer-executable instructions are loaded and executed by a processor, the steps of the method as described in any one of the first aspects are implemented.

[0050] Example 3: One technical solution provided in this embodiment of the invention is: an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor, when calling the computer program in the memory, implements the steps of the voltage stability operating domain characterization method of a new energy transmission system described above.

[0051] Example 4: One technical solution provided in this embodiment of the invention is: a storage medium storing computer-executable instructions, which, when loaded and executed by a processor, implement the steps of a method for characterizing the voltage stable operating domain of a new energy transmission system as described in the above embodiment.

[0052] Through the above description of the embodiments, those skilled in the art will understand that, for the sake of convenience and brevity, only the division of the above functional modules is used as an example. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the specific device can be divided into different functional modules to complete all or part of the functions described above.

[0053] In the embodiments provided in this application, it should be understood that the disclosed structures and methods can be implemented in other ways. For example, the structural embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another structure, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, or indirect coupling or communication connection between structures or units, and may be electrical, mechanical, or other forms.

[0054] The units described as separate components may or may not be physically separate. A component shown as a unit can be one or more physical units; that is, it can be located in one place or distributed in multiple different locations. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0055] Furthermore, in the embodiments of this application, the functional units can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0056] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a readable storage medium. Based on this understanding, the technical solutions of the embodiments of this application, in essence, or the parts that contribute to the prior art, or all or part of the technical solutions, can be embodied in the form of a software product. This software product is stored in a storage medium and includes several instructions to cause a device (which may be a microcontroller, chip, etc.) or processor to execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0057] The specific embodiments described above are preferred embodiments of the voltage stability operating domain characterization method and apparatus for a new energy transmission system of the present invention, and are not intended to limit the specific scope of the present invention. The scope of the present invention includes but is not limited to the specific embodiments described above. All equivalent changes made in accordance with the shape and structure of the present invention are within the protection scope of the present invention.

Claims

1. A method for characterizing the voltage stability operating domain of a new energy transmission system, characterized in that: Includes the following steps: A three-dimensional state space surface is established based on the power flow equation of the renewable energy transmission system, consisting of the renewable energy grid connection point voltage, the transmitted active power, and the transmitted reactive power. The preset voltage ride-through threshold, converter capacity, and active power margin are respectively mapped to the voltage boundary, capacity boundary, and power margin boundary of the three-dimensional state space surface on the power plane. Based on the intersection relationship between the power margin boundary and the voltage boundary on the power plane, the critical short-circuit ratio of the new energy transmission system under different voltage thresholds is determined; Based on the numerical comparison results between the critical short-circuit ratio and the actual system short-circuit ratio, an effective boundary combination constituting the voltage stable operating domain on the power plane is determined from the voltage boundary, capacity boundary, and power margin boundary. The voltage stable operating domain of the new energy transmission system is characterized according to the effective boundary combination.

2. The method for characterizing the voltage stability operating domain of a new energy transmission system according to claim 1, characterized in that: The steps for establishing a three-dimensional state space surface composed of the grid connection point voltage of the renewable energy transmission system, the transmitted active power, and the transmitted reactive power based on the power flow equations of the renewable energy transmission system are as follows: An equivalent circuit model is constructed based on the receiving-end equivalent electromotive force and the transmitting-line equivalent reactance of the new energy transmission system. Based on the equivalent circuit model, the power flow equation is determined according to the mathematical relationship between the voltage, active power and reactive power of the new energy grid connection point. All feasible solutions to the power flow equations are solved within the three-dimensional spatial constraints consisting of the voltage, active power, and reactive power to construct the three-dimensional state space surface; the three-dimensional state space surface is used to characterize the global operating trajectory of the voltage at the grid connection point of the new energy source as the power output changes.

3. The method for characterizing the voltage stability operating domain of a new energy transmission system according to claim 1, characterized in that: The construction of the voltage boundary specifically includes: The normalized voltage amplitude of the new energy grid connection point is limited to between a preset low voltage ride-through threshold and a high voltage ride-through threshold, and a first voltage boundary corresponding to the low voltage ride-through threshold and a second voltage boundary corresponding to the high voltage ride-through threshold are determined in the power plane; the first voltage boundary and the second voltage boundary together define the effective operating voltage range of the new energy grid connection point voltage in the power plane.

4. The method for characterizing the voltage stability operating domain of a new energy transmission system according to claim 1, characterized in that: The construction of the capacity boundary specifically includes: The apparent power limit of the converter is determined based on the capacity of the grid-connected converter. A capacity constraint equation between the active power and reactive power of the new energy grid-connected point is established based on the apparent power limit of the converter. The capacity constraint equation indicates that the sum of the squares of the active power and the squares of the reactive power does not exceed the square of the apparent power limit of the converter. Thus, on the power plane constructed with active power as the horizontal axis and reactive power as the vertical axis, the operable power point of the new energy grid-connected point is limited to the area inside a circle with the origin of the power plane as the center and the apparent power limit of the converter as the radius. The circumferential boundary of the area inside the circle is taken as the capacity boundary.

5. The method for characterizing the voltage stability operating domain of a new energy transmission system according to claim 1, characterized in that: The construction of the power margin boundary specifically includes: The active power margin coefficient is determined based on the ratio of the current active power of the new energy grid connection point to the reserved power reserve ratio between the current active power and the system active power transmission limit. On the three-dimensional state space surface, the active power transmission limit value corresponding to each reactive power value is solved along the reactive power change path; The active power transmission limit value is reduced by the active power margin coefficient to obtain the active power reduction value corresponding to each reactive power value. The set of power margin boundary points on the power plane is constructed by the reactive power value and the active power reduction value. The power margin boundary is constructed by sequentially connecting the points in the power margin boundary point set.

6. The method for characterizing the voltage stability operating domain of a new energy transmission system according to claim 3, characterized in that: The critical short-circuit ratio includes a first short-circuit ratio characterizing the system short-circuit capacity level at the intersection of the power margin boundary and the high-voltage crossing threshold boundary, and a second short-circuit ratio characterizing the system short-circuit capacity level at the intersection of the power margin boundary and the high-voltage crossing threshold boundary; the steps for determining the critical short-circuit ratio are as follows: On the power plane, a first intersection point between the power margin boundary and the first voltage boundary is determined, and the first short-circuit ratio corresponding to the first intersection point is calculated based on the coordinate value of the first intersection point on the power plane. A second intersection point between the power margin boundary and the second voltage boundary is determined on the power plane, and the second short-circuit ratio corresponding to the second intersection point is calculated based on the coordinate value of the second intersection point on the power plane.

7. The method for characterizing the voltage stability operating domain of a new energy transmission system according to claim 6, characterized in that, The steps for characterizing the voltage stable operating domain include: When the actual system short-circuit ratio is greater than the first short-circuit ratio, the voltage stable operating region is determined to be a first type of region enclosed by the first voltage boundary, the second voltage boundary, and the capacity boundary. When the actual system short-circuit ratio is less than the second short-circuit ratio, the voltage stable operating region is determined to be a third type of region enclosed by the first voltage boundary, the second voltage boundary and the power margin boundary; When the actual system short-circuit ratio is between the first short-circuit ratio and the second short-circuit ratio, the voltage stable operating region is determined to be a second type of region jointly enclosed by the first voltage boundary, the second voltage boundary, the capacity boundary, and the power margin boundary.

8. A voltage stable operating domain characterization apparatus, applicable to the method described in claims 1 to 7, characterized in that: include: The surface construction module establishes a three-dimensional state space surface based on the power flow equation of the renewable energy transmission system, consisting of the renewable energy grid connection point voltage, the transmitted active power, and the transmitted reactive power. The boundary mapping module maps the preset voltage crossover threshold, converter capacity, and active power margin to the voltage boundary, capacity boundary, and power margin boundary of the three-dimensional state space surface on the power plane, respectively. The short-circuit ratio determination module determines the critical short-circuit ratio of the new energy transmission system under different voltage thresholds based on the intersection relationship between the power margin boundary and the voltage boundary on the power plane. The operating domain characterization module, based on the numerical comparison results between the critical short-circuit ratio and the actual system short-circuit ratio, determines the effective boundary combination constituting the voltage stable operating domain on the power plane from the voltage boundary, capacity boundary and power margin boundary, and characterizes the voltage stable operating domain of the new energy transmission system according to the effective boundary combination.

9. An electronic device, characterized in that: It includes a memory and a processor, wherein the memory stores a computer program, and the processor, when calling the computer program in the memory, implements the steps of the method as described in any one of claims 1 to 7.

10. A storage medium, characterized in that: The storage medium stores computer-executable instructions, which, when loaded and executed by a processor, implement the steps of the method as described in any one of claims 1 to 7.

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