A method and system for electromechanical transient simulation of power system voltage stability

Abstract

The present invention discloses a method and system for simulating the electromechanical transient state of power system voltage stability. The method obtains data after the system is disturbed and uses a parameter identification algorithm to obtain the time constant for the load to recover to a steady state, as well as the proportional coefficients related to the static active load and reactive load. A conventional ZIP static load model is listed, and a dynamic ZIP load model is constructed using a proportional-integral-differential (PID) and a limiting step to reflect the input-output relationship between active and reactive loads and equivalent impedances. The system equilibrium point is determined based on the results of steady-state power flow calculations, and all dynamic equations of the entire network are linearized at the equilibrium point to obtain a state-space model. The eigenvalues ​​of the state matrix are calculated, and the voltage stability of the busbar where the load is located is determined based on the positive and negative signs of the real parts of the relevant eigenvalues. A dynamic time-domain simulation is performed on the adjusted system, and an N-1 or N-2 line fault is imposed on the entire network to simulate the voltage collapse scenario that may occur in the system. This provides theoretical support for proposing countermeasures after voltage instability.

Description

Technical Field

[0001] The present invention belongs to the technical field of dynamic load modeling in power systems, and in particular relates to a method and system for electromechanical transient simulation of voltage stability in power systems. Background Art

[0002] As voltage stability research deepens, dynamic load modeling has attracted further attention. It is generally believed that the static voltage characteristics of loads have a crucial impact on system voltage stability. In engineering, the voltage-power (Vp or Vq) transfer characteristic curve of a power system, also known as the nose curve, is often used to analyze the static voltage stability of a power system. Generally speaking, a power system must operate with a certain margin from the nose point to ensure voltage stability. By adjusting network parameters, the required static voltage stability margin can be maintained and the static voltage stability limit of the system can be improved. The nose curve reflects the dominant role of dynamic load characteristics in voltage stability research: First, as the voltage at the node where the load resides drops, the load absorbs reactive power from the system, worsening the reactive power balance and further forming a positive feedback mechanism for voltage drop. Second, after a voltage drop, the load exhibits dynamic recovery characteristics, with active and reactive power recovering to a certain level at a certain rate, and in extreme cases, even returning to their original levels. Third, the inherent characteristic of dynamic loads is that they automatically adjust their equivalent impedance to achieve active / reactive power balance in the system.

[0003] Qualitatively, dynamic load models used in voltage stability studies must inherently adjust their equivalent impedance to maintain active / reactive power balance. Furthermore, the load model must be consistent with the results of static voltage stability analysis during equilibrium point stability analysis and effectively simulate voltage collapse during transient simulations, achieving consistency between transient simulations and post-fault static voltage stability analysis results.

[0004] Based on the ZIP model, the most commonly used comprehensive load model in the industry, this paper proposes a modified ZIP load model. While accurately describing the load port characteristics, this model conducts extensive quantitative research on voltage stability issues and reflects the essential dynamic characteristics related to voltage instability. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the deficiencies in the above-mentioned prior art and provide a method and system for electromechanical transient simulation of power system voltage stability, which is used to solve the technical problem that the existing industrial load model is difficult to reflect the essence of voltage instability, conduct quantitative research on power system voltage stability, and accurately characterize the transient process of power system voltage instability.

[0006] The present invention adopts the following technical solutions:

[0007] A method for simulating electromechanical transient state of power system voltage stability includes the following steps:

[0008] S1. Obtain data on transient changes in voltage, active power, and reactive power of the busbar where the load is located after the system is disturbed, and use a parameter identification algorithm to obtain the time constant for the load to recover to a steady state, and proportional coefficients related to static active load and reactive load. The proportional coefficients related to reactive load include constant power ratio, constant current ratio, and constant impedance ratio parameters.

[0009] S2. Based on the parameters obtained in step S1, a conventional ZIP static load model is written. The load equivalent resistance and equivalent reactance are introduced as state variables of the dynamic load model. A proportional-integral-differential link and a limiter link are used to construct a dynamic ZIP load model to reflect the input-output relationship between active and reactive loads and equivalent impedances.

[0010] S3. Determine the system equilibrium point based on the steady-state power flow calculation results of step S2, and linearize all dynamic equations of the entire network at the equilibrium point to obtain a state space model. Calculate the eigenvalues ​​of the state matrix, and determine the voltage stability of the bus where the load is located based on the positive and negative signs of the real parts of the relevant eigenvalues.

[0011] S4. Perform dynamic time-domain simulation on the adjusted system, impose N-1 or N-2 type line faults on the entire network, and simulate the voltage collapse scenario that may occur in the system.

[0012] Preferably, step S2 is specifically:

[0013] S201. Introducing load equivalent resistance as a state variable. The rate of change of the equivalent resistance is proportional to the difference between the actual active power at the measurement point and the active power calculated by the ZIP static load model. This indicates that when the active power taken is lower than the required active power, greater active power can be obtained by reducing its own resistance.

[0014] S202. Introducing load equivalent reactance as a state variable. The rate of change of the equivalent reactance is proportional to the difference between the reactive power calculated by the ZIP static load model and the actual reactive power at the measurement point. This indicates that when the active power taken is lower than the required active power, greater active power can be obtained by increasing the load resistance.

[0015] S203. Add a network handover equation to describe the relationship between the voltage, current and power of the bus where the load is located.

[0016] Preferably, the dynamic ZIP model is:

[0017]

[0018]

[0019] in, It is the inverse of the active / reactive power recovery time constant; is the maximum / minimum value of the load equivalent resistance; is the maximum / minimum value of the load equivalent reactance; , and They are respectively the active power, reactive power and node voltage absorbed by the load in the steady state before the system is disturbed; , and Respectively represent the active power, reactive power and node voltage absorbed by the load after being disturbed; and Respectively represent the equivalent resistance and equivalent reactance of the load; coefficient a , b and c Respectively represent the proportion of constant impedance, constant current and constant power in the total load, and the subscript " p "and" q ” represents the corresponding active and reactive power situations.

[0020] Preferably, the interface equation between the dynamic load model and the network is as follows:

[0021]

[0022]

[0023]

[0024]

[0025]

[0026] in, represents the real / imaginary part of the receiving node voltage, Represents the real / imaginary part of the current flowing through the transmission line; and They represent the equivalent resistance and equivalent reactance of the load respectively; , and They respectively represent the active power, reactive power absorbed by the load after being disturbed and the node voltage.

[0027] Preferably, in step S3, the voltage stability of the bus where the load is located is judged according to the positive or negative sign of the real part of the relevant eigenvalue, the eigenvalue of the coefficient matrix is ​​calculated, and the relationship between the system eigenvalue and the voltage stability of the power system is observed. The coefficient matrix is ​​specifically:

[0028]

[0029] in, and is the equivalent resistance of the load and equivalent reactance The differential of Represents the receiving node voltage The real / imaginary part of the initial value, Indicates the current flowing through the transmission line Real / imaginary part of the initial value; It represents the initial value of equivalent resistance and equivalent reactance before the load is disturbed. Indicates the resistance and reactance of the transmission line; and They respectively represent the active power and reactive power absorbed by the load after being disturbed.

[0030] Preferably, the steady-state value of the line current is:

[0031]

[0032] in, is the power supply voltage, is the line impedance amplitude, is the load equivalent impedance amplitude, is the line impedance power factor angle, is the load impedance power factor angle.

[0033] Preferably, the steady-state value of the receiving-end voltage is:

[0034]

[0035] in, is the power supply voltage, is the line impedance amplitude, is the load equivalent impedance amplitude, is the line impedance power factor angle, is the load impedance power factor angle.

[0036] Preferably, step S4 is specifically:

[0037] S401. Based on the steady-state solution of the power flow calculation as the initial solution, perform electromechanical transient simulation on the entire system, define the N-1 or N-2 type fault event set for the critical circuit, perform batch operations based on the expected fault event set, and save the relevant transient simulation results.

[0038] S402: Collect node voltage change data of all buses in the entire network in the simulation results, evaluate the system's dynamic response capability for voltage recovery after a fault, and determine whether the voltage collapses in the fault scenario.

[0039] Preferably, the changes in voltage near the load center node due to large disturbances are recorded to determine the system voltage stability, the load nodes far away from the power center are screened, the lines connected to the load nodes at the head or end are listed as lines to be disconnected, and various possible line disconnection situations are simulated to form a line disconnection fault set.

[0040] In a second aspect, an embodiment of the present invention provides a power system voltage stability electromechanical transient simulation system, comprising:

[0041] The data module obtains data on transient changes in voltage, active power, and reactive power of the busbar where the load is located after the system is disturbed. The parameter identification algorithm is used to obtain the time constant for the load to recover to a steady state, and the proportional coefficients related to the static active load and reactive load. The proportional coefficients related to the reactive load include constant power ratio, constant current ratio, and constant impedance ratio parameters.

[0042] The construction module writes a conventional ZIP static load model based on parameter columns, introduces load equivalent resistance and equivalent reactance as state variables of the dynamic load model, and uses proportional integral differential links and limiter links to construct a dynamic ZIP load model to reflect the input-output relationship between active and reactive loads and equivalent impedances;

[0043] The calculation module determines the system equilibrium point based on the steady-state power flow calculation results, linearizes all dynamic equations of the entire network at the equilibrium point to obtain a state space model, calculates the eigenvalues ​​of the state matrix, and determines the voltage stability of the bus where the load is located based on the positive and negative signs of the real parts of the relevant eigenvalues;

[0044] The simulation module performs dynamic time-domain simulation on the adjusted system, imposes N-1 or N-2 type line faults on the entire network, and simulates the voltage collapse scenario that may occur in the system.

[0045] In a third aspect, a computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned electromechanical transient simulation method for power system voltage stability when executing the computer program.

[0046] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, comprising a computer program, which, when executed by a processor, implements the steps of the above-mentioned electromechanical transient simulation method for power system voltage stability.

[0047] Compared with the prior art, the present invention has at least the following beneficial effects:

[0048] A method for electromechanical transient simulation of power system voltage stability is used to analyze the transient process of voltage at load nodes in the power system. Compared with the original static ZIP load model, it can reflect the dynamic characteristics of voltage changes from two aspects: small disturbance voltage stability analysis and large disturbance transient voltage stability.

[0049] Furthermore, the input-output relationship between the active load equivalent resistance adjustment characteristics and its dynamic characteristics is constructed, which is the basic model for the voltage stability analysis of the load node of the present invention. This model is essentially a type of differential equation that describes the dynamic changes of the active load equivalent resistance, reflecting the adjustment of the load equivalent resistance after the active power balance of the power system is destroyed. It can be easily applied to small-disturbance stability analysis and electromechanical transient simulation, and it is easy to form an objective and clear static voltage stability criterion; the input-output relationship between the active load equivalent reactance adjustment characteristics and its dynamic characteristics is constructed, which is the basic model for the voltage stability analysis of the load node of the present invention. Based on the logic of the constructed equivalent resistance dynamic model, the model supplements the influence of reactive load characteristics on the static stability of the system voltage and simplifies the physical law of reactive support of the load node voltage; the use of the xy coordinate system to establish the network interface algebraic relationship between the active load, reactive load and the electrical quantity of the load node is a key step for the small-disturbance stability analysis and electromechanical transient simulation of the present invention.

[0050] Furthermore, the core algorithm of this invention performs small-disturbance voltage stability analysis on specific systems, accurately providing a generalized, practical criterion for the static voltage stability of power systems. Based on the model established in step 2, this algorithm quantitatively identifies the small-disturbance analysis results for the system operating in the upper and lower halves of the nose curve, allowing the static voltage stability of the power system to be determined based on the eigenvalue properties of the resistance and reactance state variables.

[0051] Furthermore, constructing an N-1 or N-2 fault prediction set is a key step in the present invention's electromechanical transient simulation of voltage stability. For load center nodes where static voltage instability or voltage collapse may occur, the lines near the node are selected for disconnection, and a line fault set is formed by screening; performing large-interference voltage stability transient simulation on a specific system is the core algorithm of the present invention. Based on the model established in step S2 and the established fault set, the time-domain simulation results can record the changes in load node voltage after the system is subjected to a large disturbance. Based on the simulation results, it can be clearly judged whether the load node voltage remains at an acceptable level.

[0052] It can be understood that the beneficial effects of the second aspect mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0053] In summary, the method of the present invention can be used to analyze the system voltage stability, identify the weak load nodes of the system voltage stability and the key links that restrict the system voltage stability, and provide theoretical support for proposing countermeasures after voltage instability.

[0054] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings to be used in the description of the embodiments. Obviously, the drawings described below are only some embodiments of 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 It is a schematic diagram of the process of the present invention;

[0057] Figure 2 A dynamic ZIP model constructed using a simple integral link;

[0058] Figure 3 For simple power system;

[0059] Figure 4 A schematic diagram of a computer device provided in accordance with an embodiment of the present invention;

[0060] Figure 5 A block diagram of an electronic device provided according to an embodiment of the present invention;

[0061] Figure 6 This is a simple power system node voltage simulation curve;

[0062] Figure 7 This is a diagram showing the load impedance changes after a simple power system is disturbed;

[0063] Figure 8 This is the active and reactive load diagram of a simple power system after a disturbance;

[0064] Figure 9 This is the IEEE14 system topology diagram and voltage distribution diagram;

[0065] Figure 10 This is a diagram of the node voltage changes in the IEEE14 system. DETAILED DESCRIPTION

[0066] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0067] In the description of the present invention, it is to be understood that the terms “include” and “comprise” indicate the presence of the described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0068] It should also be understood that the terms used in the present specification are only for the purpose of describing particular embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0069] It should be further understood that the term "and / or" as used in the present specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0070] It should be understood that although the terms "first," "second," and "third" may be used to describe preset ranges in embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are merely used to distinguish one preset range from another. For example, without departing from the scope of embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0071] The word "if," as used herein, may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to the determination" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)," depending on the context.

[0072] The accompanying drawings illustrate various schematic diagrams of structures according to embodiments disclosed herein. These figures are not drawn to scale; for clarity, some details are exaggerated and some details may be omitted. The shapes of the various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art may design regions / layers with different shapes, sizes, and relative positions as needed.

[0073] The present invention provides a method for electromechanical transient simulation of power system voltage stability. Based on the integrated load model ZIP, a differential dynamic equation is constructed with load equivalent impedance as the state variable. A proportional-integral link is used to describe the input-output relationship between active / reactive imbalance and equivalent impedance. This, combined with network interface algebraic equations, facilitates small-disturbance stability analysis, reveals the mechanism of non-periodic voltage instability at the equilibrium point, and can be used for transient simulation of bus voltage collapse scenarios. The proposed dynamic load model uses resistance and reactance as state variables in the dynamic load model, avoiding the static constant power characteristics of previous load models and allowing active and reactive loads to undergo step changes after a disturbance. This approach has a wider range of applicability and is more consistent with the dynamic response mechanism of actual loads. Furthermore, the proposed small-disturbance stability analysis algorithm and batch fault voltage transient stability simulation algorithm, based on the dynamic load model, cross-validate the static voltage stability of the power system from both theoretical and simulation perspectives, avoiding the limitations of the traditional nose curve that determines stability based on the transmission power limit point, and revealing the connection between the static voltage stability of the system and the dynamic characteristics of the load.

[0074] See also Figure 1 The present invention provides a method for simulating electromechanical transient state of voltage stability of a power system, comprising the following steps:

[0075] S1. Obtain data on transient changes in voltage, active power, and reactive power of the busbar where the load is located after the system is disturbed, and use a parameter identification algorithm to obtain the time constant for the load to recover to a steady state, and the proportional coefficients related to the static active load and reactive load, the latter of which include constant power ratio, constant current ratio, and constant impedance ratio parameters;

[0076] The input data for the calculation model obtained from relevant departments include the following data:

[0077] The basic technical data for voltage stability analysis include:

[0078] The time constant for the load to recover from disturbance to steady state, the constant active power ratio, the constant active current ratio, the constant active resistance ratio, the constant reactive power ratio, the constant reactive current ratio, and the constant reactive reactance ratio.

[0079] S2. Write a conventional ZIP static load model, introduce the load equivalent resistance and equivalent reactance as the state variables of the dynamic load model, and use the proportional integral differential link and the limit link to construct a dynamic ZIP load model to reflect the input-output relationship between active and reactive loads and equivalent impedance;

[0080] Establish a ZIP comprehensive load model and network handover equations, specifically:

[0081] (1) Establish a polynomial ZIP static load model based on the static active power proportional coefficient and the static reactive power proportional coefficient:

[0082] (1)

[0083] (2)

[0084] in, is the constant resistance ratio / constant reactance ratio; is the constant active current ratio / constant reactive current ratio; is the constant active load ratio / constant reactive load ratio; It is the active power / reactive power absorbed by the load in the steady state before the system is disturbed; It is the active power / reactive power actually absorbed by the load; The node voltage amplitude of the bus where the load is located in the steady state before the system is disturbed; is the node voltage amplitude of the bus where the load is located;

[0085] The proportional coefficients satisfy the following relationship:

[0086] (3)

[0087] (2) Establish the connection between the load model and the power network

[0088] (4)

[0089] (5)

[0090] (6)

[0091] in, is the real / imaginary part of the node voltage; The real / imaginary part of the current injected into the node.

[0092] Based on the fact that load power regulation needs to be achieved through its own internal impedance regulation, the model is dynamically modified. The specific steps are as follows:

[0093] S201. Introducing the load equivalent resistance as a state variable. The rate of change of the equivalent resistance (i.e., the time derivative of the equivalent resistance) is proportional to the difference between the actual active power at the measurement point and the active power calculated by the ZIP static load model. This indicates that when the active power drawn is lower (higher) than the required active power, a greater (less) active power can be obtained by reducing (increasing) the load's own resistance.

[0094] S202. Introducing load equivalent reactance as a state variable, the rate of change of the equivalent reactance (i.e., the time derivative of the equivalent reactance) is proportional to the difference between the reactive power calculated by the ZIP static load model and the actual reactive power at the measurement point. This indicates that when the active power drawn is lower (higher) than the required active power, a greater (less) active power can be obtained by increasing (decreasing) the load resistance.

[0095] S203. Add a network handover equation to describe the relationship between the voltage, current and power of the bus where the load is located.

[0096] The specific steps to establish a dynamic ZIP model are:

[0097] Introduce the load equivalent internal resistance and internal reactance to determine the change of load equivalent impedance

[0098] The load equivalent resistance is defined as , the load equivalent reactance is Assuming that the voltage remains unchanged, the active power is Inversely proportional to the reactive power and Inversely proportional. When , increase (decrease) Reduce (increase) active power gain, increase (decrease) Increase (decrease) reactive power acquisition.

[0099] The PID (Proportional Integral Derivative) control link is used to describe the changes in the load equivalent impedance. The limiter link is used to smooth the resistance reactance and limit the load level. Here, the simplest proportional integral link and limiter link are used as an example to establish a dynamic ZIP load model. More complex load dynamic behaviors can be achieved by adding a differential link, etc.

[0100] (7)

[0101] (8)

[0102] in, It is the active / reactive power demand of conventional ZIP comprehensive load model.

[0103] according to Figure 2The schematic diagram of the dynamic ZIP model constructed by the integral link constructs the dynamic change characteristics of the resistance and reactance, and the generated resistance and reactance are incorporated into the load node, achieving the steady-state characteristics of the ZIP model through self-regulation. Under this simulation structure, the dynamic ZIP load model is described as:

[0104] (9)

[0105] (10)

[0106] in, It is the inverse of the active / reactive power recovery time constant; is the maximum / minimum value of the load equivalent resistance; It is the maximum / minimum value of the load equivalent reactance.

[0107] The interface equation between the dynamic load model and the network is established as follows:

[0108] (11)

[0109] (12)

[0110] (13)

[0111] (14)

[0112] (15)

[0113] S3. Determine the system equilibrium point based on the steady-state power flow calculation results, and linearize all dynamic equations of the entire network at the equilibrium point to obtain a state space model. Calculate the eigenvalues ​​of the state matrix, and determine the voltage stability of the busbar where the load is located based on the positive and negative signs of the real parts of the relevant eigenvalues.

[0114] See also Figure 3 , taking a simple power system as an example, a constant voltage source is connected to a dynamic ZIP load through two transmission lines; the power supply voltage is , the parallel impedance of the two transmission lines is , the load impedance is The steady-state value of the line current can be calculated as:

[0115] (16)

[0116] The steady-state value of the receiving terminal voltage is:

[0117] (17)

[0118] From equations (16) and (17), we can know that the real part of the steady-state value of the line current is and the imaginary part , the real part of the steady-state value of the receiving terminal voltage and the imaginary part , and the steady-state value of the load equivalent impedance and They are and . In addition, the network equation is supplemented as follows:

[0119] (18)

[0120] (19)

[0121] in, , .

[0122] For simplicity, let the constant power portion of the dynamic ZIP load account for 100%, and linearize Equations (9) to (15), (18), and (19) to obtain the following equations:

[0123] (20)

[0124] The eigenvalues ​​of the coefficient matrix of equation (20) are calculated to observe the relationship between the system eigenvalues ​​and the voltage stability of the power system.

[0125] S4. Perform dynamic time-domain simulation on the adjusted system, impose N-1 or N-2 type line faults on the entire network, and simulate the voltage collapse scenario that may occur in the system.

[0126] A set of potential line-break faults that could lead to voltage collapse is formed. Based on this, batch electromechanical transient simulations are performed to record the voltage changes near the load center nodes when they are subject to large disturbances. The system voltage stability is determined, and load nodes far away from the power center (i.e., with weak electrical connection to the power center) are screened. Lines connected to the load nodes at the head or end are listed as lines to be disconnected. Various possible line break situations are simulated to form a line-break fault set, such as single-line break and double-line break faults.

[0127] S401. Based on the steady-state solution of the power flow calculation as the initial solution, perform electromechanical transient simulation on the entire system, define the N-1 or N-2 type fault event set for the critical circuit, perform batch operations based on the expected fault event set, and save the relevant transient simulation results.

[0128] S402: Collect node voltage change data of all buses in the entire network in the simulation results, evaluate the system's dynamic response capability for voltage recovery after a fault, and determine whether the voltage collapses in the fault scenario.

[0129] Those skilled in the art will appreciate that various aspects of the present invention may be implemented as systems, methods, or program products. Accordingly, various aspects of the present invention may be implemented in the following forms: entirely in hardware, entirely in software (including firmware, microcode, etc.), or in a combination of hardware and software, collectively referred to herein as "circuits," "modules," or "platforms."

[0130] In another embodiment of the present invention, a power system voltage stability electromechanical transient simulation system is provided, which can be used to implement the above-mentioned power system voltage stability electromechanical transient simulation method. Specifically, the power system voltage stability electromechanical transient simulation system includes a data module, a construction module, a calculation module and a simulation module.

[0131] The data module obtains data on transient changes in voltage, active power, and reactive power of the busbar where the load is located after the system is disturbed, and uses a parameter identification algorithm to obtain the time constant for the load to recover to a steady state, and the proportional coefficients related to the static active load and reactive load. The proportional coefficients related to the reactive load include constant power ratio, constant current ratio, and constant impedance ratio parameters.

[0132] The construction module writes a conventional ZIP static load model based on parameter columns, introduces load equivalent resistance and equivalent reactance as state variables of the dynamic load model, and uses proportional integral differential links and limiter links to construct a dynamic ZIP load model to reflect the input-output relationship between active and reactive loads and equivalent impedances;

[0133] The calculation module determines the system equilibrium point based on the steady-state power flow calculation results, linearizes all dynamic equations of the entire network at the equilibrium point to obtain a state space model, calculates the eigenvalues ​​of the state matrix, and determines the voltage stability of the bus where the load is located based on the positive and negative signs of the real parts of the relevant eigenvalues;

[0134] The simulation module performs dynamic time-domain simulation on the adjusted system, imposes N-1 or N-2 type line faults on the entire network, and simulates the voltage collapse scenario that may occur in the system.

[0135] In another embodiment of the present invention, a terminal device is provided, which includes a processor and a memory, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions to implement the corresponding method flow or corresponding function; the processor described in the embodiment of the present invention can be used for the operation of the electromechanical transient simulation method of power system voltage stability, including:

[0136] Data on transient changes in voltage, active power, and reactive power on the bus where the load is located after a system disturbance is obtained. A parameter identification algorithm is used to determine the time constant for the load to recover from a disturbance to a steady-state state, as well as the proportional coefficients associated with the static active and reactive loads. The proportional coefficients associated with the reactive load include constant power ratio, constant current ratio, and constant impedance ratio parameters. A conventional ZIP static load model is constructed based on the obtained parameters, and the load equivalent resistance and equivalent reactance are introduced as state variables of the dynamic load model. A dynamic ZIP load model is constructed using proportional-integral-differential and limiting steps to reflect the input-output relationship between active and reactive loads and equivalent impedances. The system equilibrium point is determined based on the steady-state power flow calculation results, and all dynamic equations of the entire network are linearized at the equilibrium point to obtain a state-space model. The eigenvalues ​​of the state matrix are calculated, and the voltage stability of the bus where the load is located is determined based on the sign of the real part of the relevant eigenvalues. A dynamic time-domain simulation of the adjusted system is performed, and an N-1 or N-2 type line fault is imposed on the entire network to simulate possible voltage collapse scenarios in the system.

[0137] In another embodiment of the present invention, a storage medium is provided, specifically a computer-readable storage medium (Memory). The computer-readable storage medium is a memory device in a terminal device, used to store programs and data. It is understood that the computer-readable storage medium herein may include both built-in storage media in the terminal device and, of course, extended storage media supported by the terminal device. It may be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, the storage space also stores one or more instructions suitable for being loaded and executed by a processor. These instructions may be one or more computer programs (including program code). It should be noted that more specific examples (a non-exhaustive list) of computer-readable storage media herein include: an electrical connection having one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), optical fiber, a portable compact disk-read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof.

[0138] Computer-readable storage media also include data signals propagated in baseband or as part of a carrier wave, which carry readable program code. Such propagated data signals can take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. The readable storage medium can also be any readable medium other than a readable storage medium, which can send, propagate, or transmit programs for use by or in conjunction with an instruction execution system, device, or device. The program code contained on the readable storage medium can be transmitted using any appropriate medium, including but not limited to wireless, wired, optical cable, RF, etc., or any suitable combination of the above.

[0139] The program code for performing the operations of the present invention may be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java, C++, and the like, as well as conventional procedural programming languages ​​such as "C" or similar programming languages. The program code may be executed entirely on the user computing device, partially on the user device, as a stand-alone software package, partially on the user computing device and partially on a remote computing device, or entirely on a remote computing device or server. In the case of a remote computing device, the remote computing device may be connected to the user computing device via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computing device (e.g., via the Internet using an Internet service provider).

[0140] The processor may load and execute one or more instructions stored in a computer-readable storage medium to implement the corresponding steps of the electromechanical transient simulation method for power system voltage stability in the above embodiment. The processor may load and execute the following steps:

[0141] Data on transient changes in voltage, active power, and reactive power on the bus where the load is located after a system disturbance is obtained. A parameter identification algorithm is used to determine the time constant for the load to recover from a disturbance to a steady-state state, as well as the proportional coefficients associated with the static active and reactive loads. The proportional coefficients associated with the reactive load include constant power ratio, constant current ratio, and constant impedance ratio parameters. A conventional ZIP static load model is constructed based on the obtained parameters, and the load equivalent resistance and equivalent reactance are introduced as state variables of the dynamic load model. A dynamic ZIP load model is constructed using proportional-integral-differential and limiting steps to reflect the input-output relationship between active and reactive loads and equivalent impedances. The system equilibrium point is determined based on the steady-state power flow calculation results, and all dynamic equations of the entire network are linearized at the equilibrium point to obtain a state-space model. The eigenvalues ​​of the state matrix are calculated, and the voltage stability of the bus where the load is located is determined based on the sign of the real part of the relevant eigenvalues. A dynamic time-domain simulation of the adjusted system is performed, and an N-1 or N-2 type line fault is imposed on the entire network to simulate possible voltage collapse scenarios in the system.

[0142] See also Figure 4 The terminal device is a computer device. The computer device 60 of this embodiment includes: a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable by the processor 61. When the computer program 63 is executed by the processor 61, it implements the method for electromechanical transient simulation of power system voltage stability in the embodiment. To avoid repetition, it is not described in detail here. Alternatively, when the computer program 63 is executed by the processor 61, it implements the functions of each model / unit in the electromechanical transient simulation system for power system voltage stability in the embodiment. To avoid repetition, it is not described in detail here.

[0143] The computer device 60 may be a desktop computer, a notebook computer, a PDA, a cloud server, or other computing devices. The computer device 60 may include, but is not limited to, a processor 61 and a memory 62. It will be understood by those skilled in the art that Figure 4 This is merely an example of the computer device 60 and does not constitute a limitation of the computer device 60 . The computer device 60 may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the computer device may also include input and output devices, network access devices, buses, etc.

[0144] The processor 61 may be a central processing unit (CPU), other general-purpose processors, central processing units (CPUs), graphics processors (GPUs), digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), other programmable logic devices, discrete gate or transistor logic devices, quantum computing-based data processing logic, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor.

[0145] The memory 62 may be an internal storage unit of the computer device 60, such as a hard disk or memory of the computer device 60. The memory 62 may also be an external storage device of the computer device 60, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the computer device 60.

[0146] Furthermore, the memory 62 may include both an internal storage unit of the computer device 60 and an external storage device. The memory 62 is used to store computer programs and other programs and data required by the computer device. The memory 62 may also be used to temporarily store data that has been output or is about to be output.

[0147] Any reference to memory, database, or other media used in the various embodiments provided herein may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical storage, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM may be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0148] The databases involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processors involved in the various embodiments provided herein may include, but are not limited to, general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic units, data processing logic units based on quantum computing, and the like.

[0149] See also Figure 5 The terminal device 600 is an electronic device that is implemented as a general-purpose computing device. The components of the electronic device may include, but are not limited to, at least one processing unit 610, at least one storage unit 620, a bus 630 connecting different platform components (including the storage unit 620 and the processing unit 610), and a display unit 640.

[0150] The storage unit stores program codes, which can be executed by the processing unit 610, so that the processing unit 610 performs the steps according to various exemplary embodiments of the present invention described in the above method section of this specification. For example, the processing unit 610 can perform the following steps: Figure 1 Follow the steps shown in .

[0151] The storage unit 620 may include a readable medium in the form of a volatile storage unit, such as a random access memory unit (RAM) 6201 and / or a cache memory unit 6202 , and may further include a read-only memory unit (ROM) 6203 .

[0152] The storage unit 620 may also include a program / utility 6204 having a set (at least one) of program modules 6205, such program modules 6205 including but not limited to: an operating system, one or more application programs, other program modules, and program data, each of which or some combination may include an implementation of a network environment.

[0153] Bus 630 may represent one or more of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, a processing unit, or a local bus using any of a variety of bus architectures.

[0154] The electronic device 600 can also communicate with one or more external devices 700 (e.g., a keyboard, a pointing device, a Bluetooth device, etc.), one or more devices that enable a user to interact with the electronic device 600, and / or any device that enables the electronic device 600 to communicate with one or more other computing devices (e.g., a router, a modem, etc.). Such communication can occur via an input / output (I / O) interface 650. Furthermore, the electronic device 600 can communicate with one or more networks (e.g., a local area network (LAN), a wide area network (WAN), and / or a public network such as the Internet) via a network adapter 660. The network adapter 660 can communicate with other modules of the electronic device 600 via the bus 630. It should be understood that, although not shown in the figures, other hardware and / or software modules can be used in conjunction with the electronic device 600, including but not limited to microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage platforms.

[0155] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, 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 part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0156] Case Analysis

[0157] In order to verify the effectiveness of the method proposed in this invention, a simple power system and an IEEE 14-bus system are selected for illustration in this case analysis.

[0158] (1) Simple power system: small disturbance stability analysis + voltage transient stability simulation

[0159] For the simple power system studied in step S3, assume that the system base capacity is 100MVA and the rated voltage is 230kV. Ignoring the ground admittance, the impedance of a single-circuit transmission line is 0.017+0.092j, and the initial value of the load impedance is 0.15+0.06j. Given that load regulation is a slow process, the integral constants are For simplicity, it is still assumed that the system's constant power load accounts for 100%.

[0160] First, the system is analyzed for small disturbance stability. The power flow calculation of the system shows that there are two initial solutions for the receiving node voltage. The high voltage solution is , the low voltage solution is Generally speaking, the power system will operate at the operating point where the high voltage solution is located. The low voltage solution means that the system has voltage collapse. Substituting the two initial voltage solutions and their corresponding line current initial values ​​into Equation (20) respectively, we can obtain two sets of eigenvalues ​​of the power system. The eigenvalue corresponding to the high voltage solution is It is an oscillation mode, which means that the receiving node voltage is stable under the high voltage solution modeling. The characteristics corresponding to the low voltage solution are two real eigenvalues, one positive and one negative, and the results are , which shows that the voltage of the receiving node is unstable under the low voltage solution and shows monotonic instability after being disturbed.

[0161] Secondly, the system is subjected to electromechanical transient simulation to observe the dynamic behavior of the voltage at the receiving node after the system is disturbed under the dynamic ZIP model. This example is intended to demonstrate the recovery process of the system load after the disturbance, so the initial value of the load impedance is adjusted to 0.2911+0.1168j, and the other parameters remain unchanged. The simulation interval is 0 to 100 seconds. At 2 seconds, a three-phase grounding fault occurs in the middle of a circuit, and the circuit is cut off after 5 cycles. The voltage change at the receiving node is as follows: Figure 6 As shown, the load equivalent impedance changes as shown in Figure 7 As shown in the figure, the active and reactive power consumed by the load impedance is as follows: Figure 8 shown. Figure 6 It shows that the system voltage drops slowly for a period of time after the fault is cleared, and then enters the recovery stage; Figure 7It shows that the load equivalent resistance first drops and then gradually recovers, while the load equivalent reactance first increases slowly and then gradually drops, reflecting the process of reactive support voltage.

[0162] (2) IEEE 14-bus system for voltage collapse scenario simulation

[0163] This example aims to simulate the voltage collapse scenario of the system using the dynamic ZIP load model. Based on the original standard system, the initial load is adjusted to twice the original example. The flow calculation is performed on this example, and the load equivalent resistance and equivalent reactance are initialized using the flow results. Figure 9 The voltage distribution of the IEEE 14 standard example system is shown. Red indicates high voltage, green indicates normal voltage, and blue indicates low voltage. The power flow results show that voltages near power centers remain high, while voltages at load centers farther from power centers are generally low. This indicates that line failures near load centers are highly likely to cause voltage collapse.

[0164] The simulation interval is from 0 seconds to 150 seconds. At 0.2 seconds, a three-phase grounding fault occurs in the middle of the line between node 6 and node 13 and the line between node 9 and node 14. After 4 cycles, these two lines are cut off. The voltage changes of each node after simulation are as follows: Figure 10 The results show that the voltage trajectory does not experience computational non-convergence and numerical oscillation. Furthermore, voltage collapse occurs at nodes near the load center (such as nodes 12, 13, and 14), with the voltage continuously dropping to a low level with no signs of recovery.

[0165] In summary, the present invention provides an electromechanical transient simulation method and system for power system voltage stability, which uses resistance and reactance as state variables in the dynamic load model, circumvents the static constant power characteristics of the previous load model, allows active and reactive loads to undergo step changes after being disturbed, has a wider range of applications, and is more in line with the dynamic response mechanism of the actual load. In addition, the small disturbance stability analysis algorithm and batch fault voltage transient stability simulation algorithm proposed on the basis of the dynamic load model proposed in the present invention cross-verify the static voltage stability of the power system from both theoretical and simulation levels, avoiding the limitations of the traditional nose curve in judging stability based on the transmission power limit point, and revealing the connection between the static voltage stability of the system and the dynamic characteristics of the load. In summary, the method proposed in the present invention can be used to analyze the system voltage stability, find out the weak load nodes of the system voltage stability and the key links that restrict the system voltage stability, and provide theoretical support for proposing countermeasures after voltage instability.

[0166] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In actual applications, the above-mentioned functions can be distributed and completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0167] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0168] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in the present invention can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present invention.

[0169] In the embodiments provided by the present invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are merely illustrative. For example, the division of the modules or units is merely a logical functional division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be through some interface, indirect coupling or communication connection of devices or units, and can be electrical, mechanical, or other forms.

[0170] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0171] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0172] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the process in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, it can implement the steps of the above-mentioned various method embodiments. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium, etc. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electric carrier signals and telecommunication signals.

[0173] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0174] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0175] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0176] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for simulating electromechanical transients of power system voltage stability, characterized in that: The following steps are involved: S1. Obtain data on transient changes in voltage, active power, and reactive power of the busbar where the load is located after the system is disturbed, and use a parameter identification algorithm to obtain the time constant for the load to recover to a steady state, and proportional coefficients related to static active load and reactive load. The proportional coefficients related to reactive load include constant power ratio, constant current ratio, and constant impedance ratio parameters. S2. Based on the parameters obtained in step S1, a conventional ZIP static load model is written. The load equivalent resistance and equivalent reactance are introduced as state variables of the dynamic load model. A proportional-integral-differential link and a limiter link are used to construct a dynamic ZIP load model to reflect the input-output relationship between active and reactive loads and equivalent impedances. S3. Determine the system equilibrium point based on the steady-state power flow calculation results of step S2, and linearize all dynamic equations of the entire network at the equilibrium point to obtain a state space model. Calculate the eigenvalues ​​of the state matrix, and determine the voltage stability of the bus where the load is located based on the positive and negative signs of the real parts of the relevant eigenvalues. S4. Perform dynamic time-domain simulation on the adjusted system, impose N-1 or N-2 type line faults on the entire network, and simulate the voltage collapse scenario that may occur in the system.

2. The electromechanical transient simulation method for power system voltage stability according to claim 1, characterized in that: Step S2 is specifically as follows: S201. Introducing load equivalent resistance as a state variable. The rate of change of the equivalent resistance is proportional to the difference between the actual active power at the measurement point and the active power calculated by the ZIP static load model. This indicates that when the active power taken is lower than the required active power, greater active power can be obtained by reducing its own resistance. S202. Introducing load equivalent reactance as a state variable. The rate of change of the equivalent reactance is proportional to the difference between the reactive power calculated by the ZIP static load model and the actual reactive power at the measurement point. This indicates that when the active power taken is lower than the required active power, greater active power can be obtained by increasing the load resistance. S203. Add a network handover equation to describe the relationship between the voltage, current and power of the bus where the load is located.

3. The electromechanical transient simulation method for power system voltage stability according to claim 2, characterized in that: The dynamic ZIP model is: in, It is the inverse of the active / reactive power recovery time constant; is the maximum / minimum value of the load equivalent resistance; is the maximum / minimum value of the load equivalent reactance; , and They are respectively the active power, reactive power and node voltage absorbed by the load in the steady state before the system is disturbed; , and Respectively represent the active power, reactive power and node voltage absorbed by the load after being disturbed; and Respectively represent the equivalent resistance and equivalent reactance of the load; coefficient a , b and c Respectively represent the proportion of constant impedance, constant current and constant power in the total load, subscript " p "and" q ” represents the corresponding active and reactive power situations.

4. The electromechanical transient simulation method for power system voltage stability according to claim 3, characterized in that: The interface equation between the dynamic load model and the network is as follows: in, represents the real / imaginary part of the receiving node voltage, Represents the real / imaginary part of the current flowing through the transmission line; and They represent the equivalent resistance and equivalent reactance of the load respectively; , and They respectively represent the active power, reactive power absorbed by the load after being disturbed and the node voltage.

5. The electromechanical transient simulation method for power system voltage stability according to claim 1, characterized in that: In step S3, the voltage stability of the bus where the load is located is determined based on the positive and negative signs of the real parts of the relevant eigenvalues, the eigenvalues ​​of the coefficient matrix are calculated, and the relationship between the system eigenvalues ​​and the voltage stability of the power system is observed. The coefficient matrix is ​​specifically: in, and is the equivalent resistance of the load and equivalent reactance The differential of Represents the receiving node voltage The real / imaginary part of the initial value, Indicates the current flowing through the transmission line Real / imaginary part of the initial value; It represents the initial value of equivalent resistance and equivalent reactance before the load is disturbed. Indicates the resistance and reactance of the transmission line; and They respectively represent the active power and reactive power absorbed by the load after being disturbed.

6. The electromechanical transient simulation method for power system voltage stability according to claim 5, characterized in that: The steady-state value of the line current is: in, is the power supply voltage, is the line impedance amplitude, is the load equivalent impedance amplitude, is the line impedance power factor angle, is the load impedance power factor angle.

7. The electromechanical transient simulation method for power system voltage stability according to claim 5, characterized in that: The steady-state value of the receiving terminal voltage is: in, is the power supply voltage, is the line impedance amplitude, is the load equivalent impedance amplitude, is the line impedance power factor angle, is the load impedance power factor angle.

8. The electromechanical transient simulation method for power system voltage stability according to claim 1, characterized in that: Step S4 is specifically as follows: S401. Based on the steady-state solution of the power flow calculation as the initial solution, perform electromechanical transient simulation on the entire system, define the N-1 or N-2 type fault event set for the critical circuit, perform batch operations based on the expected fault event set, and save the relevant transient simulation results. S402: Collect node voltage change data of all buses in the entire network in the simulation results, evaluate the system's dynamic response capability for voltage recovery after a fault, and determine whether the voltage collapses in the fault scenario.

9. The electromechanical transient simulation method for power system voltage stability according to claim 8, characterized in that: Record the changes in voltage near the load center node when it is subject to large disturbances, judge the system voltage stability, screen the load nodes far away from the power center, list the lines connected to the load nodes at the head or end as lines to be disconnected, and simulate various possible line disconnection situations to form a line disconnection fault set.

10. An electromechanical transient simulation system for power system voltage stability, characterized in that: include: The data module obtains data on transient changes in voltage, active power, and reactive power of the busbar where the load is located after the system is disturbed. The parameter identification algorithm is used to obtain the time constant for the load to recover to a steady state, and the proportional coefficients related to the static active load and reactive load. The proportional coefficients related to the reactive load include constant power ratio, constant current ratio, and constant impedance ratio parameters. The construction module writes a conventional ZIP static load model based on parameter columns, introduces load equivalent resistance and equivalent reactance as state variables of the dynamic load model, and uses proportional integral differential links and limiter links to construct a dynamic ZIP load model to reflect the input-output relationship between active and reactive loads and equivalent impedances; The calculation module determines the system equilibrium point based on the steady-state power flow calculation results, linearizes all dynamic equations of the entire network at the equilibrium point to obtain a state space model, calculates the eigenvalues ​​of the state matrix, and determines the voltage stability of the bus where the load is located based on the positive and negative signs of the real parts of the relevant eigenvalues; The simulation module performs dynamic time-domain simulation on the adjusted system, imposes N-1 or N-2 type line faults on the entire network, and simulates the voltage collapse scenario that may occur in the system.

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