AC / DC system power acceptance boundary quantification method, apparatus and device, and medium

Abstract

The invention relates to the technical field of power system stability analysis, in particular to an AC / DC system power admission boundary quantification method, device, equipment and medium, and the method comprises the steps: decomposing and reconstructing the power voltage sensitivity to obtain external characteristic equivalent admittance and equivalent power; constructing a similar transformation matrix, and equivalently transforming the system power flow Jacobian matrix into an improved complex Jacobian matrix; carrying out order reduction on the complex Jacobian matrix by adopting singularity equivalence and Schuer transformation, constructing an admittance ratio matrix, and obtaining a system limit power boundary; and estimating a power boundary according to a matrix operator norm theory, and judging a critical state that the system approaches the power acceptance limit based on an admittance ratio index. According to the method, the influence of different control modes of direct current and new energy equipment on the power acceptance limit is comprehensively considered, quantitative evaluation indexes are provided, whether the system is in a dangerous state or reaches the power acceptance limit or not is effectively judged, the evaluation result is visual, the adaptability is high, whether the system operates safely and stably or not is judged, and a reasonable decision is made.

Description

Technical Field

[0001] The present invention relates to the technical field of power system stability analysis, and in particular to a method, device, equipment and medium for quantifying the power acceptance boundary of an AC / DC system. Background Art

[0002] In recent years, the rapid development of high-voltage direct current (HVDC) technology and the widespread adoption of renewable energy sources (such as wind and solar) have profoundly changed the structure and operational characteristics of power systems. In particular, with the large-scale deployment of HVDC projects and the rapid increase in installed capacity of renewable energy generation, power systems have become not only more complex but also more diverse in their operational characteristics. While this transformation has significantly promoted the optimization of energy mix and the transition to a green and low-carbon economy, it has also brought numerous challenges, particularly system stability issues, which in turn have placed higher demands on the assessment of power acceptance limits.

[0003] In traditional power system analysis, the system's power acceptance limits are typically categorized into static power limits, dynamic power limits, and transient power limits. Static power limit analysis is one of the most common analytical methods. Typically, the assessment of static power limits relies on the study of power flow calculation models and their interactions. However, with the continuous development of DC transmission and renewable energy generation, existing analytical models and methods are no longer able to comprehensively and accurately describe the changes in the system's static power limits. In particular, the variable control modes of DC transmission and renewable energy equipment, as well as their complex interactions with the AC system, further blur the system's power acceptance boundaries.

[0004] The Jacobian matrix is ​​an important tool for analyzing the static stability of a system. Although it can effectively quantify the power acceptance limit of the system, its calculation is complex. Especially when facing the nonlinear characteristics brought by DC systems and new energy equipment, the calculation of indicators such as the determinant and eigenvalue of the Jacobian matrix is ​​relatively difficult, making it difficult to effectively evaluate whether the system is close to the power acceptance limit in real time.

[0005] Therefore, quickly and effectively determining whether a power system is approaching its power acceptance limit (PAL) and conducting timely risk assessments have become key to improving the static stability of power systems and ensuring their safe operation. Especially under complex operating conditions, PAL assessment methods urgently need to be improved to better address the challenges posed by DC transmission and new energy equipment.

[0006] The information disclosed in this background technology section is only intended to deepen the understanding of the overall background technology of the present invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art. Summary of the Invention

[0007] The present invention provides a method, device, equipment and medium for quantifying the power acceptance boundary of an AC / DC system, thereby effectively solving the problems in the background technology.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is: a method for quantifying the power acceptance boundary of an AC / DC system, comprising the following steps:

[0009] Decompose and reconstruct the power and voltage sensitivity of DC and new energy equipment in different control modes to obtain the external characteristic equivalent admittance and external characteristic equivalent power of each device;

[0010] Based on the external characteristic equivalent admittance and equivalent power, a similarity transformation matrix is ​​constructed, and the system power flow Jacobian matrix is ​​equivalently transformed to obtain an improved system complex Jacobian matrix;

[0011] Singularity equivalence and Schur transform are used to reduce the order of the complex Jacobian matrix of the system, an admittance ratio matrix is ​​constructed, and the limit power boundary condition of the system is obtained based on the admittance ratio matrix;

[0012] According to the matrix operator norm theory, the limit power boundary is estimated, and based on the preset improved admittance ratio index, it is determined that the system is in a critical state close to the power acceptance limit.

[0013] Furthermore, the model of the external characteristic equivalent admittance includes:

[0014] ;

[0015] Where, Represents the external characteristic equivalent admittance phasor; represents the external characteristic equivalent conductance; represents the external characteristic equivalent susceptance; j represents the imaginary unit; represents the node voltage amplitude, represents the node voltage phase angle; Indicates the active power generated by the device; Indicates the reactive power generated by the device.

[0016] Furthermore, the model of the external characteristic equivalent power includes:

[0017] ;

[0018] Where, Indicates the external characteristic equivalent power; Indicates the external characteristic equivalent active power; represents the external characteristic equivalent reactive power; j represents the imaginary unit; represents the node voltage amplitude, represents the node voltage phase angle; Indicates the active power generated by the device; Indicates the reactive power generated by the device.

[0019] Furthermore, the similarity transformation matrix includes:

[0020] ;

[0021] Where, represents the similarity transformation matrix; represents the node voltage phasor; represents the conjugate of the node voltage phasor; j represents the imaginary unit.

[0022] Furthermore, the complex Jacobian matrix of the system is expressed by the following equivalent transformation:

[0023] ;

[0024] Where, represents the complex Jacobian matrix of the improved system; represents the system power flow Jacobian matrix; Represents the AC network port characteristics, the AC side Jacobian matrix; Represents the device port characteristics, the device-side Jacobian matrix; represents the submatrix of the reduced-order system admittance matrix after eliminating the tie nodes. For a system without generator PV nodes, The submatrix of the reduced-order system admittance matrix after deleting the rows and columns related to the balanced nodes; It represents the external characteristic equivalent admittance; represents the similarity transformation matrix; j represents the imaginary unit; represents the node voltage amplitude; represents the conjugate of the complex power emitted by the device; Represents the conjugate of the external characteristic equivalent power phasor; The phasor exponential form of the node voltage phase angle.

[0025] Furthermore, singularity equivalence and Schur transform are used to reduce the order of the complex Jacobian matrix of the system, including:

[0026] ;

[0027] Where, represents the complex Jacobian matrix of the improved system; represents the submatrix of the admittance matrix of the reduced-order system after eliminating the contact nodes; It represents the external characteristic equivalent admittance; represents the admittance ratio matrix; represents the node voltage amplitude; represents the conjugate of the complex power emitted by the device; Represents the conjugate of the external characteristic equivalent power phasor; The phasor exponential form of the node voltage phase angle.

[0028] Furthermore, the admittance ratio matrix includes:

[0029] ;

[0030] ;

[0031] ;

[0032] Where, represents the admittance ratio matrix; represents the node voltage amplitude; represents the conjugate of the complex power emitted by the device; Represents the conjugate of the external characteristic equivalent power phasor; The phasor index form that represents the node voltage phase angle; represents the conjugate of the submatrix of the admittance matrix of the reduced-order system after eliminating the contact nodes; represents the conjugate of the external characteristic equivalent admittance.

[0033] Furthermore, based on the admittance ratio matrix, a limit power boundary condition of the system is obtained, including:

[0034] when , the system operates stably and is within the power acceptance boundary;

[0035] when , the system reaches the power acceptance limit and is critically stable;

[0036] when , the system becomes unstable and is outside the power acceptance boundary.

[0037] Furthermore, the improved admittance ratio index includes:

[0038] ;

[0039] Where, A conservative criterion for evaluating the system power acceptance limit; To provide accurate criteria for evaluating the system power acceptance limit; is the critical improved admittance ratio, represents the admittance ratio matrix.

[0040] Furthermore, judging whether the system is in a critical state close to the power acceptance limit based on the preset improved admittance ratio indicator includes:

[0041] according to The distance from 1 determines the distance between the current system power and the power acceptance limit;

[0042] when , the system has not reached the power acceptance limit and maintains stable operation;

[0043] when , the system is close to the power acceptance limit and is in the dangerous operation area;

[0044] when After that, if the system power continues to increase, then by judging Whether the predetermined threshold is met can accurately determine whether the system has reached the power acceptance limit.

[0045] The present invention also includes a device for quantifying the power acceptance boundary of an AC / DC system, using the above method, comprising:

[0046] The power and voltage sensitivity decomposition and reconstruction unit is used to decompose and reconstruct the power and voltage sensitivity of DC and new energy equipment in different control modes to obtain the external characteristic equivalent admittance and external characteristic equivalent power of each device;

[0047] A similarity transformation matrix construction unit is used to construct a similarity transformation matrix based on the external characteristic equivalent admittance and equivalent power, and to perform an equivalent transformation on the system power flow Jacobian matrix to obtain an improved system complex Jacobian matrix;

[0048] An order reduction processing unit is used to reduce the order of the complex Jacobian matrix of the system by using singular equivalence and Schur transform to construct an admittance ratio matrix;

[0049] A power acceptance boundary calculation unit, configured to obtain a limit power boundary condition of the system based on the admittance ratio matrix;

[0050] The power acceptance limit judgment unit is used to estimate the limit power boundary according to the matrix operator norm theory, and judge the critical state of the system approaching the power acceptance limit based on the preset improved admittance ratio index.

[0051] The present invention also includes a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the above method when executing the computer program.

[0052] The present invention also includes a storage medium storing a computer program, which implements the above method when executed by a processor.

[0053] The beneficial effects of the present invention are:

[0054] This evaluation method comprehensively considers the impact of different control modes of DC and new energy equipment on the system power acceptance limit, and provides quantitative evaluation indicators (improved admittance ratio, critical value). It can effectively determine whether the system is in a dangerous operating state and whether it has reached the power acceptance limit, making the evaluation results more intuitive. The proposed indicators are not restricted by equipment type and network topology, have good adaptability, and are conducive to judging whether the system can operate safely and stably, thereby making scientific and reasonable decisions. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0056] Figure 1 A flow chart of a method for quantifying the power acceptance boundary of AC / DC systems;

[0057] Figure 2 The flowchart for the implementation of the power acceptance boundary quantification method for AC and DC systems is provided;

[0058] Figure 3 This is the topology diagram of the improved IEEE39 node system;

[0059] Figure 4 It is the characteristic diagram of the minimum eigenvalue of the system Jacobian matrix and the improved admittance ratio index changing with the increase of system load power;

[0060] Figure 5 This is a characteristic diagram of the change of the improved admittance ratio index with the increase of system load power under different control modes of DC and new energy equipment.

[0061] Figure 6 It is a structural diagram of the power acceptance boundary quantization device of the AC / DC system;

[0062] Figure 7 A schematic diagram of the structure of a computer device. DETAILED DESCRIPTION

[0063] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0064] Example 1:

[0065] like Figure 1 、 2A method for quantifying the power acceptance boundary of an AC / DC system is shown, comprising the following steps:

[0066] S10: Decompose and reconstruct the power and voltage sensitivities of DC and new energy equipment in different control modes to obtain the external characteristic equivalent admittance and external characteristic equivalent power of each device;

[0067] S20: Based on the external characteristic equivalent admittance and equivalent power, construct a similarity transformation matrix, and perform an equivalent transformation on the system power flow Jacobian matrix to obtain an improved system complex Jacobian matrix;

[0068] S30: reducing the order of the complex Jacobian matrix of the system by using singular equivalence and Schur transform, constructing an admittance ratio matrix, and obtaining a limit power boundary condition of the system based on the admittance ratio matrix;

[0069] S40: estimating the limit power boundary according to the matrix operator norm theory, and judging the critical state of the system approaching the power acceptance limit based on a preset improved admittance ratio index.

[0070] Therefore, according to the embodiment of the present invention, the AC / DC system power acceptance boundary quantification method based on the improved admittance ratio is used. The method decomposes and reconstructs the power and voltage sensitivity of DC and new energy equipment in different control modes into external characteristic equivalent admittance and equivalent power, performs equivalent order reduction on the system power flow Jacobian matrix to construct the admittance ratio matrix, and obtains the system limit power boundary condition based on the admittance ratio matrix. By defining the improved admittance ratio index, it is quickly evaluated whether the system is close to the power acceptance limit. The method of the present invention can effectively evaluate the static power limit of the AC / DC system considering different control modes of the equipment.

[0071] According to the above technical solution, compared with the existing technology, the significant advantage of the AC / DC system power acceptance boundary quantification method based on improved admittance ratio proposed in the present invention is that: this evaluation method comprehensively considers the impact of different control modes of DC and new energy equipment on the system power acceptance limit, and provides quantitative evaluation indicators (improved admittance ratio, critical value), which can effectively judge whether the system is in a dangerous operating state and whether it has reached the power acceptance limit, making the evaluation results more intuitive. The proposed indicators are not restricted by equipment type and network topology, have good adaptability, and are conducive to judging whether the system can operate safely and stably, thereby making scientific and reasonable decisions.

[0072] This method provides more accurate system power limit boundary conditions through an improved Jacobian matrix, order reduction techniques, and an admittance ratio matrix. This allows for a more accurate assessment of the power acceptance capacity of AC / DC systems under different control modes, effectively predicting whether the system is approaching its power acceptance limit and avoiding system overload and instability. It comprehensively considers the power and voltage sensitivities of DC and new energy devices under different control modes, a more comprehensive and flexible approach than traditional methods. It is applicable to a variety of device configurations and control strategies, exhibiting strong adaptability and the ability to better address the impact of different system configurations on the power acceptance limit.

[0073] By performing an equivalent transformation on the system power flow Jacobian matrix and employing order reduction techniques (such as singularity equivalence and the Schur transform), the computational complexity of the system's ultimate power limit is significantly reduced. This method enables rapid and effective assessment of system stability in practical applications, avoiding the tedious computational steps required by traditional methods. The method introduces an improved admittance ratio metric, and through estimation based on matrix operator norm theory, it enables rapid assessment of whether the system is approaching the power acceptance limit. In particular, the definition of the "improved admittance ratio metric" enables real-time monitoring of the system's operating status, promptly identifying whether the system has entered a dangerous zone, and providing rapid decision support. By accurately assessing the power acceptance limit and monitoring it in real time, system instability due to overload can be effectively avoided. This helps improve the safety and reliability of AC / DC systems, ensures stable operation in complex operating environments, and reduces the risk of outages.

[0074] This method is not limited by device type, control mode, or network topology, making it widely applicable to various power systems, including both traditional AC grids and modern AC / DC hybrid systems. Whether it is a high-voltage direct current (HVDC) system or a complex grid structure integrating renewable energy, this method can be used to quantitatively analyze the power acceptance boundary.

[0075] As a preference of the above embodiment, in step S10, the model of the external characteristic equivalent admittance includes:

[0076] ;

[0077] Where, Represents the external characteristic equivalent admittance phasor; represents the external characteristic equivalent conductance; represents the external characteristic equivalent susceptance; j represents the imaginary unit; represents the node voltage amplitude, represents the node voltage phase angle; Indicates the active power generated by the device; Indicates the reactive power generated by the equipment; Indicates the active voltage phase angle sensitivity of the equipment; Indicates the reactive voltage phase angle sensitivity of the equipment; Indicates the active voltage amplitude sensitivity of the equipment; Indicates the reactive voltage amplitude sensitivity of the device.

[0078] By introducing the external characteristic equivalent admittance model, the device's electrical characteristics and power acceptance behavior can be more accurately simulated. In particular, by considering the device's active and reactive phase angle sensitivity, as well as voltage sensitivity, a more accurate power acceptance boundary assessment can be provided for the system.

[0079] In this embodiment, in step S10, the model of the external characteristic equivalent power includes:

[0080] ;

[0081] Where, Indicates the external characteristic equivalent power; Indicates the external characteristic equivalent active power; represents the external characteristic equivalent reactive power; j represents the imaginary unit; represents the node voltage amplitude, represents the node voltage phase angle; Indicates the active power generated by the device; Indicates the reactive power generated by the device.

[0082] The above-mentioned external characteristic equivalent admittance and equivalent power can be used not only for DC and new energy equipment, but also for power supplies and loads with power voltage sensitivity.

[0083] By introducing an external characteristic equivalent power model, this method can accurately calculate the contribution of each device in an AC / DC system to the power acceptance limit, especially in complex systems (such as AC / DC hybrid systems with grid-connected renewable energy sources). This helps accurately estimate whether the system is approaching its power acceptance limit.

[0084] Wherein, in step S20, the similarity transformation matrix includes:

[0085] ;

[0086] Where, represents the similarity transformation matrix; represents the node voltage phasor, ; represents the conjugate of the node voltage phasor; j represents the imaginary unit.

[0087] By introducing a similarity transformation matrix, this method can more accurately describe the relationships between node voltages in power systems, especially in complex AC / DC hybrid systems. The use of the similarity transformation matrix allows for a more detailed analysis of device node voltages and power flows, thereby improving the accuracy of power acceptance boundary assessments.

[0088] As a preference of the above embodiment, in step S20, the system complex Jacobian matrix is ​​represented by the following equivalent transformation:

[0089] ;

[0090] Where, represents the complex Jacobian matrix of the improved system; represents the system power flow Jacobian matrix; Represents the AC network port characteristics, the AC side Jacobian matrix; Represents the device port characteristics, the device-side Jacobian matrix; represents the submatrix of the reduced-order system admittance matrix after eliminating the tie nodes. For a system without generator PV nodes, The submatrix of the reduced-order system admittance matrix after deleting the rows and columns related to the balance nodes. For a system with a generator PV node, The reduced-order system admittance matrix is ​​the submatrix after deleting the rows and columns related to the balancing nodes and the rows and columns related to the generator PV nodes; It represents the external characteristic equivalent admittance; represents the similarity transformation matrix; j represents the imaginary unit; represents the node voltage amplitude; represents the conjugate of the complex power emitted by the device; Represents the conjugate of the external characteristic equivalent power phasor; The phasor index form of the node voltage phase angle is expressed as, ; 、 They represent the active and reactive voltage phase angle sensitivity matrices of AC network nodes respectively; 、 They represent the active and reactive voltage amplitude sensitivity matrices of AC network nodes respectively.

[0091] The improved system complex Jacobian matrix enables more accurate assessment of the power acceptance limit of AC and DC systems. Similarity transformations, order reduction, and the introduction of external characteristic admittance allow for more details and device characteristics to be considered when calculating the power acceptance limit, improving assessment accuracy.

[0092] The use of similarity transformation matrices can reduce computational complexity when dealing with complex, high-dimensional systems while maintaining the integrity of system characteristics. This is crucial for analyzing the stability of AC and DC systems, especially in systems with a complex array of devices and diverse control methods. It can more accurately capture the interactions between devices and networks, improving system stability analysis capabilities.

[0093] In this embodiment, in step S30, singular equivalence and Schur transform are used to reduce the order of the complex Jacobian matrix of the system, including:

[0094] ;

[0095] Where, represents the complex Jacobian matrix of the improved system; represents the submatrix of the admittance matrix of the reduced-order system after eliminating the contact nodes; It represents the external characteristic equivalent admittance; represents the admittance ratio matrix; represents the node voltage amplitude; represents the conjugate of the complex power emitted by the device; Represents the conjugate of the external characteristic equivalent power phasor; The phasor index form of the node voltage phase angle is expressed as, .

[0096] Using singularity equivalence and the Schur transform to reduce the order of the complex Jacobian matrix helps simplify the complexity of large-scale AC / DC power systems, maintain system characteristics, and ensure the accuracy of power acceptance boundary assessments. The reduced admittance matrix and improved complex Jacobian matrix improve computational accuracy, avoiding the oversimplification and computational errors common in traditional methods.

[0097] Wherein, in step S30, the admittance ratio matrix includes:

[0098] ;

[0099] ;

[0100] ;

[0101] Where, represents the admittance ratio matrix; represents the node voltage amplitude; represents the conjugate of the complex power emitted by the device; Represents the conjugate of the external characteristic equivalent power phasor; The phasor index form of the node voltage phase angle is expressed as, ; represents the conjugate of the submatrix of the admittance matrix of the reduced-order system after eliminating the contact nodes; represents the conjugate of the external characteristic equivalent admittance.

[0102] By introducing the admittance ratio matrix, this method can more accurately assess the power acceptance limit of AC and DC systems. In particular, by introducing parameters such as node voltage amplitude, the conjugate of complex power, and the conjugate of external characteristic equivalent power, it can more accurately capture the relationship between various devices and the system in the power system, avoiding the accuracy loss of traditional simplified methods.

[0103] As a preference of the above embodiment, in step S30, obtaining the system's limit power boundary condition based on the admittance ratio matrix includes:

[0104] when , the system operates stably and is within the power acceptance boundary;

[0105] when , the system reaches the power acceptance limit and is critically stable;

[0106] when , the system becomes unstable and is outside the power acceptance boundary. This system limit power boundary condition is exactly true for systems without generator PV nodes, and is approximately true for systems with generator PV nodes.

[0107] Based on the operator norm of the admittance ratio matrix, sufficient conditions for the system to not reach the power acceptance limit include:

[0108] ;

[0109] Where, 、 Represent the minimum and maximum eigenvalues ​​of the matrix respectively; represents the operator norm of the matrix; represents the admittance ratio matrix.

[0110] In this embodiment, in step S40, the improved admittance ratio index includes:

[0111] ;

[0112] Where, To improve the admittance ratio; A conservative criterion for evaluating the system power acceptance limit; To provide accurate criteria for evaluating the system power acceptance limit; is the critical improved admittance ratio, represents the admittance ratio matrix.

[0113] Improved admittance ratio ( ) indicator provides a more accurate power acceptance boundary assessment tool for the system. (conservative criterion) and This method provides a more detailed power acceptance limit assessment while maintaining system safety. Particularly in complex AC / DC systems, it avoids the misjudgments and over-conservatism often associated with traditional methods, improving assessment accuracy.

[0114] As a preferred embodiment of the above, in step S40, judging whether the system is in a critical state close to the power acceptance limit based on a preset improved admittance ratio indicator includes:

[0115] according to The distance from 1 determines the distance between the current system power and the power acceptance limit;

[0116] when , the system has not reached the power acceptance limit and maintains stable operation;

[0117] when , the system is close to the power acceptance limit and is in the dangerous operation area;

[0118] when After that, if the system power continues to increase, then by judging Whether the predetermined threshold is met can accurately determine whether the system has reached the power acceptance limit.

[0119] This method can dynamically monitor the approach of the power acceptance limit when the system power increases. Close to critical values ​​(e.g. <1), it can be judged to be close to the power acceptance limit, and timely control measures such as scheduling and load adjustment can be taken to effectively avoid overload and system instability. ) and accurate judgment ( ) Gradually evaluate the power acceptance limit to ensure that the system is not easily put into a dangerous state due to calculation or decision-making errors, thereby enhancing the safety of system operation.

[0120] Example 2:

[0121] Further integration Figures 3 to 5 As shown, based on the implementation of the evaluation method in the above embodiment, the implementation of the AC / DC system power acceptance boundary quantification method of the present invention is further explained.

[0122] like Figure 3The topology diagram of the improved IEEE39 node system shown in the figure shows that the improvement over the original IEEE39 node system lies in that the generator at node 34 is connected to the LCC DC system instead, and the generator at node 37 is connected to the new energy unit instead. The output power of the two remains consistent with the output power of the original generator.

[0123] First, the effectiveness of the improved admittance ratio index is verified. By globally and synchronously increasing the power of all generators and loads, the minimum eigenvalue of the system Jacobian matrix and the characteristics of the improved admittance ratio index changing with the increase of system power are compared. The results are as follows: Figure 4 shown.

[0124] It can be seen that the minimum eigenvalue of the system's Jacobian matrix changes very little with global power growth, only dropping rapidly to a critical value near the static power limit. This trend makes it difficult to predict in advance whether the system is approaching its power limit and effectively assess whether the system has reached its power acceptance limit. However, for the improved admittance ratio indicator, IAR1, it decreases significantly and monotonically with global power growth, remaining in a nearly linear state globally. This trend allows for intuitive analysis of the system's operating state approaching its power limit. Furthermore, the improved admittance ratio crosses the critical value at a load factor of around 1.3, which is only 10% different from the actual power limit. This indicates that IAR1, as a conservative criterion for system proximity to the power acceptance limit, can effectively assess whether the system is nearing its power acceptance limit. After IAR1 crosses the critical value, IAR2 can be used to determine whether the system has reached its power acceptance limit. It can be seen that when the system reaches the power acceptance limit, IAR2 also reaches the critical value, indicating that IAR2 is an accurate criterion for accurately assessing whether the system has reached its power acceptance limit. In addition, for some jumps of the improved admittance ratio indicator, this phenomenon is caused by the reactive power exceeding the limit of the generator PV node and transforming it into the PQ node.

[0125] The above verifies the effectiveness of the improved admittance ratio index. We further analyze the impact of different control modes of DC and new energy equipment on the system power acceptance limit. Similarly, we globally increase the power of all generators and loads, and compare the changing characteristics of the improved admittance ratio index under different control modes of DC and new energy equipment with the increase of system load power. The results are as follows: Figure 5 As shown, the initial control mode of the LCC DC system is the CP-CEA (constant active power and constant arc extinction angle) mode, and the initial control mode of the new energy unit is the constant power mode.

[0126] It can be found that the improved admittance ratio indicator is applicable to DC and new energy equipment in different control modes, and can effectively evaluate whether the system has reached the power acceptance limit.

[0127] The present invention also includes a device for quantifying the power acceptance boundary of an AC / DC system, such as Figure 6As shown, using the method as described above, including:

[0128] The power and voltage sensitivity decomposition and reconstruction unit is used to decompose and reconstruct the power and voltage sensitivity of DC and new energy equipment in different control modes to obtain the external characteristic equivalent admittance and external characteristic equivalent power of each device;

[0129] A similarity transformation matrix construction unit is used to construct a similarity transformation matrix based on the external characteristic equivalent admittance and equivalent power, and to perform an equivalent transformation on the system power flow Jacobian matrix to obtain an improved system complex Jacobian matrix;

[0130] An order reduction processing unit is used to reduce the order of the complex Jacobian matrix of the system by using singular equivalence and Schur transform to construct an admittance ratio matrix;

[0131] A power acceptance boundary calculation unit, configured to obtain a limit power boundary condition of the system based on the admittance ratio matrix;

[0132] The power acceptance limit judgment unit is used to estimate the limit power boundary according to the matrix operator norm theory, and judge the critical state of the system approaching the power acceptance limit based on the preset improved admittance ratio index.

[0133] See Figure 7 The computer device 400 provided in the embodiment of the present application includes a processor 410 and a memory 420, wherein the memory 420 stores a computer program executable by the processor 410, and when the computer program is executed by the processor 410, the method described above is performed.

[0134] The embodiment of the present application further provides a storage medium 430 , on which a computer program is stored. When the computer program is run by the processor 410 , the above method is executed.

[0135] Among them, the storage medium 430 can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, disk or optical disk.

[0136] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. "Multiple" means two or more, unless otherwise specifically defined.

[0137] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0138] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0139] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code comprising one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may be performed out of the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention pertain.

[0140] The logic and / or steps represented in a flowchart or otherwise described herein, for example, can be considered a sequenced list of executable instructions for implementing the logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (e.g., a computer-based system, a system including a processor, or other system that can fetch and execute instructions from an instruction execution system, apparatus, or device). For purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (not exhaustive) of computer-readable media include: an electrical connection with one or more wires (electronic devices), a portable computer disk cartridge (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and programmable read-only memory (EPROM or flash memory), fiber optic devices, and a portable compact disc read-only memory (CDROM). Furthermore, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing it in another suitable manner if necessary, and then storing it in a computer memory.

[0141] It should be understood that various components of the present invention may be implemented using hardware, software, firmware, or a combination thereof. In the above-described embodiments, multiple steps or methods may be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof may be used: a discrete logic circuit having logic gate circuits for implementing logic functions on data signals, an application-specific integrated circuit having suitable combinational logic gate circuits, a programmable gate array (PGA), a field-programmable gate array (FPGA), etc.

[0142] Those skilled in the art will understand that all or part of the steps in the method of the above embodiment can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiment.

[0143] The storage medium mentioned above may be a read-only memory, a magnetic disk, or an optical disk, etc. Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and are not to be construed as limiting the present invention. Persons skilled in the art may make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for quantifying the power acceptance margin of an AC / DC system, characterized in that: The steps include: Decompose and reconstruct the power and voltage sensitivity of DC and new energy equipment in different control modes to obtain the external characteristic equivalent admittance and external characteristic equivalent power of each device; Based on the external characteristic equivalent admittance and equivalent power, a similarity transformation matrix is ​​constructed, and the system power flow Jacobian matrix is ​​equivalently transformed to obtain an improved system complex Jacobian matrix; Singularity equivalence and Schur transform are used to reduce the order of the complex Jacobian matrix of the system, an admittance ratio matrix is ​​constructed, and the limit power boundary condition of the system is obtained based on the admittance ratio matrix; According to the matrix operator norm theory, the limit power boundary is estimated, and based on the preset improved admittance ratio index, it is determined that the system is in a critical state close to the power acceptance limit.

2. The AC / DC system power acceptance margin quantification method according to claim 1, characterized in that: The model of the external characteristic equivalent admittance includes: ； Where, Represents the external characteristic equivalent admittance phasor; represents the external characteristic equivalent conductance; represents the external characteristic equivalent susceptance; j represents the imaginary unit; represents the node voltage amplitude, represents the node voltage phase angle; Indicates the active power generated by the device; Indicates the reactive power generated by the device.

3. The AC / DC system power acceptance margin quantification method according to claim 1, characterized in that: The model of the external characteristic equivalent power includes: ； Where, Indicates the external characteristic equivalent power; Indicates the external characteristic equivalent active power; represents the external characteristic equivalent reactive power; j represents the imaginary unit; represents the node voltage amplitude, represents the node voltage phase angle; Indicates the active power generated by the device; Indicates the reactive power generated by the device.

4. The AC / DC system power acceptance margin quantification method according to claim 1, characterized in that: The similarity transformation matrix includes: ； Where, represents the similarity transformation matrix; represents the node voltage phasor; represents the conjugate of the node voltage phasor; j represents the imaginary unit.

5. The AC / DC system power acceptance margin quantification method according to claim 1, characterized in that: The complex Jacobian matrix of the system is expressed by the following equivalent transformation: ； Where, represents the complex Jacobian matrix of the improved system; represents the system power flow Jacobian matrix; Represents the AC network port characteristics, the AC side Jacobian matrix; Represents the device port characteristics, the device-side Jacobian matrix; represents the submatrix of the reduced-order system admittance matrix after eliminating the tie nodes. For a system without generator PV nodes, The submatrix of the reduced-order system admittance matrix after deleting the rows and columns related to the balanced nodes; It represents the external characteristic equivalent admittance; represents the similarity transformation matrix; j represents the imaginary unit; represents the node voltage amplitude; represents the conjugate of the complex power emitted by the device; Represents the conjugate of the external characteristic equivalent power phasor; The phasor exponential form of the node voltage phase angle.

6. The AC / DC system power acceptance margin quantification method according to claim 1, characterized in that: The system's complex Jacobian matrix is ​​reduced using singularity equivalence and Schur transform, including: ； Where, represents the complex Jacobian matrix of the improved system; represents the submatrix of the admittance matrix of the reduced-order system after eliminating the contact nodes; It represents the external characteristic equivalent admittance; represents the admittance ratio matrix; represents the node voltage amplitude; represents the conjugate of the complex power emitted by the device; Represents the conjugate of the external characteristic equivalent power phasor; The phasor exponential form of the node voltage phase angle.

7. The AC / DC system power acceptance margin quantification method according to claim 1, characterized in that: The admittance ratio matrix includes: ； ； ； Where, represents the admittance ratio matrix; represents the node voltage amplitude; represents the conjugate of the complex power emitted by the device; Represents the conjugate of the external characteristic equivalent power phasor; The phasor index form that represents the node voltage phase angle; represents the conjugate of the submatrix of the admittance matrix of the reduced-order system after eliminating the contact nodes; represents the conjugate of the external characteristic equivalent admittance.

8. The AC / DC system power acceptance margin quantification method according to claim 1, characterized in that: The system's limit power boundary conditions are obtained based on the admittance ratio matrix, including: when , the system operates stably and is within the power acceptance boundary; when , the system reaches the power acceptance limit and is critically stable; when , the system becomes unstable and is outside the power acceptance boundary.

9. The AC / DC system power acceptance margin quantification method according to claim 1, characterized in that: The improved admittance ratio index includes: ； Where, A conservative criterion for evaluating the system power acceptance limit; To provide accurate criteria for evaluating the system power acceptance limit; is the critical improved admittance ratio, represents the admittance ratio matrix.

10. The AC / DC system power acceptance margin quantification method according to claim 1, characterized in that: The system is judged to be in a critical state close to the power acceptance limit based on the preset improved admittance ratio indicator, including: according to The distance from 1 determines the distance between the current system power and the power acceptance limit; when , the system has not reached the power acceptance limit and maintains stable operation; when , the system is close to the power acceptance limit and is in the dangerous operation area; when After that, if the system power continues to increase, then by judging Whether the predetermined threshold is met can accurately determine whether the system has reached the power acceptance limit.

11. A device for quantifying the power acceptance boundary of an AC / DC system, characterized in that: Using the method according to any one of claims 1 to 10, comprising: The power and voltage sensitivity decomposition and reconstruction unit is used to decompose and reconstruct the power and voltage sensitivity of DC and new energy equipment in different control modes to obtain the external characteristic equivalent admittance and external characteristic equivalent power of each device; A similarity transformation matrix construction unit is used to construct a similarity transformation matrix based on the external characteristic equivalent admittance and equivalent power, and to perform an equivalent transformation on the system power flow Jacobian matrix to obtain an improved system complex Jacobian matrix; An order reduction processing unit is used to reduce the order of the complex Jacobian matrix of the system by using singular equivalence and Schur transform to construct an admittance ratio matrix; A power acceptance boundary calculation unit, configured to obtain a limit power boundary condition of the system based on the admittance ratio matrix; The power acceptance limit judgment unit is used to estimate the limit power boundary according to the matrix operator norm theory, and judge the critical state of the system approaching the power acceptance limit based on the preset improved admittance ratio index.

12. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the method according to any one of claims 1 to 10 is implemented.

13. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 10 is implemented.

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