Method of modeling and computer device for power system load models

Abstract

The application discloses a modeling method and a computer device of a power system load model, and the method comprises the following steps: establishing an initial comprehensive load model according to a third-order state equation of an induction motor and a power equation of a target static load model; simplifying the initial comprehensive load model according to a plurality of self-defined parameters to reduce parameters of the initial comprehensive load model, and obtaining a simplified comprehensive load model; converting the simplified comprehensive load model into a polar coordinate comprehensive load model according to amplitudes and absolute phase angles of port voltages of load nodes and amplitudes and absolute phase angles of state quantities of the simplified motor model; and linearizing the polar coordinate comprehensive load model by using linearization parameters according to constraint relationships corresponding to steady-state parameters, and obtaining a linearized target load model, so that the characterization ability and the accuracy of the target load model are improved.

Description

Technical Field

[0001] This application relates to the field of power system technology, and in particular to a modeling method and computer device for power system load models. Background Technology

[0002] Numerical simulation of power systems is a crucial tool for power system security and stability analysis. The accuracy of numerical simulation depends on the accuracy of power system modeling. Therefore, establishing an accurate power system model is the primary task in power system simulation and analysis, with load modeling being one of the most challenging aspects. The load model represents the aggregation characteristics of various loads at load nodes. However, loads at load nodes are diverse in type and characteristics, and due to changes in user behavior, load characteristics also exhibit time-varying and spatial variations. Furthermore, the low-voltage network topology and line parameters of the load-connected system vary significantly, leading to highly complex node load aggregation characteristics. Choosing different load models and parameters can result in significantly different dynamic response results in power system simulations, potentially even leading to misjudgments or omissions in system stability assessments. Therefore, establishing a correct load model structure and obtaining accurate load model parameters are essential for analysis.

[0003] Early load models primarily used static load models. However, in practice, static load models suffer from overly simplistic structures and insufficient representational capabilities. Therefore, integrated load models combining induction motor and static load models emerged. These integrated load models are complex nonlinear models, and current methods for analyzing nonlinear models are not yet mature enough, which has become one of the obstacles to understanding the nature of loads.

[0004] Some methods involve downgrading the induction motor model in the integrated load model to a lower-order motor model. However, this approach loses much of the dynamic characteristics of the induction motor, affecting the representational capability of the integrated load model.

[0005] Other methods assume a constant phase angle and use voltage amplitude as input to linearize the third-order induction motor model, obtaining the single-input multi-output state-space equations and transfer functions of the linearized induction motor model. Steady-state information is then used to derive the constraints between parameters. Alternatively, based on the constant phase angle assumption, further assumptions of constant frequency and speed are made, degenerating the induction motor model into a second-order linear model, and the parameter sensitivity and spectral characteristics of the transfer function of the induction motor are analyzed. However, using the constant phase angle assumption makes it impossible to study the influence of the phase angle on the induction motor response.

[0006] Another method is based on the PSASP integrated load model. The real and imaginary axis components of the transient electromotive force obtained by rectangular decomposition are used as state variables. Linearization yields a multi-input multi-output state-space equation with voltage amplitude and phase angle as inputs. However, the rectangular coordinate decomposition of the transient electromotive force of the motor state variable does not reflect the dynamic change characteristics of the state variable significantly enough. Summary of the Invention

[0007] This application provides a modeling method and computer device for a power system load model. Based on the constraint relationship corresponding to the steady-state parameters, the polar coordinate integrated load model is linearized using linearization parameters to improve the representation ability and accuracy of the target load model.

[0008] Firstly, a modeling method for a power system load model is provided, comprising: establishing an initial integrated load model based on the third-order state equation of an induction motor and the power equation of a target static load model; simplifying the initial integrated load model based on multiple custom parameters to reduce the parameters of the initial integrated load model, thereby obtaining a simplified integrated load model; converting the simplified integrated load model into a polar coordinate integrated load model based on the amplitude and absolute phase angle of the port voltage of the load node, and the amplitude and absolute phase angle of the state variables of the simplified motor model; and linearizing the polar coordinate integrated load model using linearization parameters based on the constraint relationship corresponding to the steady-state parameters, thereby obtaining a linearized target load model, wherein the steady-state parameters are determined when the polar coordinate integrated load model is in a steady state, and the linearization parameters are determined by performing a first-order Taylor expansion on the target nonlinear parameters in the polar coordinate integrated load model.

[0009] In a second aspect, a computer device is provided, including a processor, a memory, and a computer program stored in the memory, wherein the processor executes the computer program to implement the modeling method for a power system load model as described in the first aspect.

[0010] By applying the above technical solutions, the initial integrated load model is simplified based on multiple custom parameters, reducing model redundancy; the simplified integrated load model is converted into a polar coordinate integrated load model, retaining the phase angle input and improving the integrity of the input information; based on the constraint relationship corresponding to the steady-state parameters, the polar coordinate integrated load model is linearized using linearization parameters to obtain a linearized target load model, which can reflect the influence of the phase angle on the response of the induction motor, thereby improving the representation ability and accuracy of the target load model. Attached Figure Description

[0011] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a flowchart of a modeling method for a power system load model according to an embodiment of this application;

[0013] Figure 2 This is a flowchart illustrating the conversion of a simplified composite load model into a polar coordinate composite load model according to an embodiment of this application.

[0014] Figure 3 A flowchart illustrating a modeling method for a power system load model according to another embodiment of this application;

[0015] Figure 4 A comparison diagram of active power in the linearized target load model and the nonlinear model of this application embodiment when the voltage step response is used;

[0016] Figure 5 A comparison diagram of reactive power in the linearized target load model and the nonlinear model of the embodiments of this application when the voltage step response is shown.

[0017] Figure 6 A comparison diagram of active power of the linearized target load model and the nonlinear model in this application embodiment when the voltage fluctuates randomly;

[0018] Figure 7 A comparison diagram of reactive power between the linearized target load model and the nonlinear model in this application embodiment when voltage fluctuates randomly.

[0019] Figure 8 This is a schematic diagram of the voltage amplitude-active power amplitude-frequency characteristic of an embodiment of this application;

[0020] Figure 9 This is a schematic diagram of the voltage amplitude-reactive power amplitude-frequency characteristic of an embodiment of this application;

[0021] Figure 10 This is a schematic diagram of the voltage phase angle change rate-active amplitude-frequency characteristic of an embodiment of this application;

[0022] Figure 11 This is a schematic diagram of the voltage phase angle change rate-reactive amplitude-frequency characteristic of an embodiment of this application;

[0023] Figure 12 This is a structural block diagram of a computer device according to an embodiment of this application. Detailed Implementation

[0024] Various embodiments and features of this application are described herein with reference to the accompanying drawings.

[0025] It should be understood that various modifications can be made to the embodiments described herein. Therefore, the above description should not be considered as limiting, but merely as an example of embodiments. Other modifications within the scope and spirit of this application will be apparent to those skilled in the art.

[0026] The accompanying drawings, which are included in and form part of this specification, illustrate embodiments of the present application and, together with the general description of the present application given above and the detailed description of the embodiments given below, serve to explain the principles of the present application.

[0027] These and other features of this application will become apparent from the following description of preferred forms of embodiments given as non-limiting examples, with reference to the accompanying drawings.

[0028] It should also be understood that although this application has been described with reference to some specific examples, those skilled in the art can certainly implement many other equivalent forms of this application.

[0029] The above and other aspects, features and advantages of this application will become more apparent when taken in conjunction with the accompanying drawings and in view of the following detailed description.

[0030] Specific embodiments of this application are described thereafter with reference to the accompanying drawings; however, it should be understood that the claimed embodiments are merely examples of this application, which can be implemented in various ways. Well-known and / or repeated functions and structures are not described in detail to avoid unnecessary or redundant details that could obscure the application. Therefore, the specific structural and functional details claimed herein are not intended to be limiting, but merely serve as the basis and representative basis for the claims to teach those skilled in the art to use this application in a variety of substantially any suitable detailed structures.

[0031] This specification may use the phrases “in one embodiment,” “in another embodiment,” “in yet another embodiment,” or “in other embodiments,” all of which may refer to one or more of the same or different embodiments according to this application.

[0032] This application provides a modeling method for a power system load model. It simplifies the initial integrated load model based on multiple custom parameters, reducing model redundancy. The simplified integrated load model is then converted into a polar coordinate integrated load model, preserving the phase angle input and improving the integrity of the input information. Based on the constraint relationships corresponding to the steady-state parameters, the polar coordinate integrated load model is linearized using linearization parameters to obtain a linearized target load model. This allows the target load model to reflect the influence of the phase angle on the induction motor response, thereby improving the representation capability and accuracy of the target load model.

[0033] like Figure 1 As shown, it includes the following steps:

[0034] Step S101: Establish an initial integrated load model based on the third-order state equation of the induction motor and the power equation of the target static load model.

[0035] In this embodiment, the integrated load model includes two parts: dynamic load and static load. The third-order state equation of the induction motor is used as the dynamic load, and the power equation of the target static load model is used as the static load to establish the initial integrated load model.

[0036] Optionally, the target static load model can be a power-law load model or a polynomial load model, i.e., a ZIP load model.

[0037] In some embodiments of this application, the initial third-order state equation of the induction motor can be expressed as:

[0038]

[0039] in, Let s be the transient electromotive force, ω0 be the synchronous rotational angular velocity, X be the rotor open-circuit reactance, X' be the rotor transient reactance, and T be the transient electromotive force. d0 H1 is the rotor open-circuit time constant, H2 is the inertial time constant, and T is the rotor open-circuit time constant. m T is the mechanical torque. e For electromagnetic torque, This represents the motor port current, ignoring the stator resistance. This represents the port voltage of the load node.

[0040] Step S102: Simplify the initial integrated load model according to multiple custom parameters to reduce the parameters of the initial integrated load model and obtain a simplified integrated load model.

[0041] By pre-setting multiple custom parameters, the initial comprehensive load model can be simplified after obtaining the initial comprehensive load model. This reduces the number of parameters in the initial comprehensive load model, resulting in a simplified comprehensive load model. This reduces model redundancy and avoids multiple solutions during parameter identification.

[0042] In some embodiments of this application, multiple custom parameters can be determined by rotor open-circuit reactance, rotor transient reactance, rotor open-circuit time constant, and reactive constant impedance coefficient.

[0043] Step S103: Based on the amplitude and absolute phase angle of the port voltage of the load node, and the amplitude and absolute phase angle of the simplified motor model state variables, the simplified integrated load model is converted into a polar coordinate integrated load model.

[0044] In this embodiment, after obtaining the simplified integrated load model, in order to make the load model better reflect the influence of phase angle and amplitude changes, the simplified integrated load model is converted into a polar coordinate integrated load model based on the amplitude and absolute phase angle of the port voltage of the load node, as well as the amplitude and absolute phase angle of the simplified motor model state variables.

[0045] Step S104: Based on the constraint relationship corresponding to the steady-state parameters, the polar coordinate integrated load model is linearized using linearization parameters to obtain a linearized target load model. The steady-state parameters are determined when the polar coordinate integrated load model is in a steady state. The linearization parameters are determined by performing a first-order Taylor expansion on the target nonlinear parameters in the polar coordinate integrated load model.

[0046] In this embodiment, the polar coordinate integrated load model is still a nonlinear model, which is not conducive to analysis. Therefore, it is necessary to linearize the load model to analyze its properties. When the polar coordinate integrated load model is in a steady state, multiple steady-state parameters are determined, along with the corresponding constraint relationships. Multiple target nonlinear parameters are then determined from the polar coordinate integrated load model. A first-order Taylor expansion is performed on these target nonlinear parameters to determine the linearization parameters. After obtaining the polar coordinate integrated load model, based on the constraint relationships corresponding to the steady-state parameters, the linearization parameters are used to linearize the polar coordinate integrated load model, resulting in a linearized target load model.

[0047] The power system load modeling method of this application includes: establishing an initial integrated load model based on the third-order state equation of the induction motor and the power equation of the target static load model; simplifying the initial integrated load model according to multiple custom parameters to reduce the parameters of the initial integrated load model and obtain a simplified integrated load model; converting the simplified integrated load model into a polar coordinate integrated load model based on the amplitude and absolute phase angle of the port voltage of the load node, and the amplitude and absolute phase angle of the state variables of the simplified motor model; and linearizing the polar coordinate integrated load model using linearization parameters according to the constraint relationship corresponding to the steady-state parameters to obtain a linearized target load model. By simplifying the initial integrated load model, model redundancy is reduced, while the phase angle input is retained, improving the integrity of the input information. This allows the target load model to reflect the influence of the phase angle on the response of the induction motor, and fully utilizes the initial values ​​of the state variables of the motor model and the constraint relationship between the parameters to obtain the target load model, thereby improving the representation capability and accuracy of the target load model.

[0048] In some embodiments of this application, the simplified composite load model is converted into a polar coordinate composite load model based on the amplitude and absolute phase angle of the port voltage of the load node, and the amplitude and absolute phase angle of the simplified motor model state variables, such as... Figure 2 As shown, it includes the following steps:

[0049] Step S1031: Determine the relative phase angle based on the difference between the absolute phase angle of the port voltage of the load node and the absolute phase angle of the simplified motor model state quantity.

[0050] In this embodiment, the relative phase angle can be obtained by subtracting the absolute phase angle of the simplified motor model state variables from the absolute phase angle of the port voltage of the load node.

[0051] Step S1032: Based on the amplitude of the port voltage of the load node, the amplitude of the simplified motor model state quantity, and the relative phase angle, the simplified integrated load model is converted into a polar coordinate integrated load model.

[0052] In this embodiment, by utilizing the amplitude of the port voltage of the load node, the amplitude of the simplified motor model state variables, and the relative phase angle, and based on the rectangular and polar coordinate formulas of the port voltage of the load node and the simplified motor model state variables, the third-order state equation of the induction motor in the simplified integrated load model is rearranged to obtain the polar coordinate integrated load model.

[0053] Since the relative phase angle is determined by the absolute phase angle of the port voltage of the load node and the absolute phase angle of the simplified motor model state quantity, the relative phase angle can characterize the absolute phase angle of the port voltage of the load node and the absolute phase angle of the simplified motor model state quantity, thereby improving the accuracy of the polar coordinate integrated load model.

[0054] In some embodiments of this application, the target static load model adopts a polynomial load model when the constant power load and constant current load are zero.

[0055] The third-order state equation of the induction motor in the initial integrated load model is expressed as:

[0056]

[0057] The output power of the motor in the initial integrated load model is expressed as follows:

[0058]

[0059] The power equation for the target static load model in the initial integrated load model is expressed as:

[0060]

[0061] The output power in the initial integrated load model is expressed as:

[0062]

[0063] Where X is the rotor open-circuit reactance, X' is the rotor transient reactance, and T is the rotor transient reactance. d0 Let ω be the rotor open-circuit time constant, s be the slip, and ω0 be the synchronous rotational angular velocity. V is the port voltage of the load node, and V is the amplitude of the port voltage of the load node. d V q They are respectively The d-axis and q-axis components, H2 is the inertial time constant, T m T is the mechanical torque. e For electromagnetic torque, Re refers to the real part of the function value, and Im refers to the imaginary part of the function value. * Point to conjugate, P m and Q m These represent the active power and reactive power of the motor, P. L and Q L These represent the output active power and output reactive power in the initial integrated load model, E. d E q Transient electromotive force d-axis classification and q-axis components, P static and Q static Q represents the actual active and reactive power of the load at the node voltage. z It is the constant impedance coefficient for reactive power.

[0064] In this embodiment, the motor port current can be controlled by... Substituting the expression into the initial third-order state equation of the induction motor, we obtain the third-order state equation of the induction motor in the initial integrated load model. Meanwhile, for ease of calculation, a polynomial load model (i.e., the Z-load model) with zero constant power load and zero constant current load is used as the target static load model.

[0065] In some embodiments of this application, the various custom parameters are represented as follows:

[0066] F d =E d / X',F q =E q / X',

[0067] Substituting the various custom parameters into the third-order state equation of the induction motor in the initial integrated load model, and ignoring the stator resistance, makes the electromagnetic torque T... e Equal to the active power P of the motor mThe third-order state equation of the induction motor in the simplified integrated load model is obtained, expressed as:

[0068]

[0069] set up

[0070] The output power in the simplified integrated load model is expressed as:

[0071]

[0072] In this embodiment, the parameters of the model are {X,X',T}. d0 ,P z Q z The number of parameters was reduced from 5 to {a,b,P}. z Q z With only 4 parameters, the redundancy of the model is reduced, which can avoid multiple solutions in the actual parameter identification process. In addition, the state equation no longer contains nonlinear terms related to the parameters to be determined, and the equation form is also simplified.

[0073] In some embodiments of this application, the rectangular and polar coordinates of the port voltage of the load node, and the rectangular and polar coordinates of the simplified motor model state variables are expressed as follows:

[0074]

[0075] The relative phase angle is defined as:

[0076] δ = θ - φ;

[0077] Using the rectangular and polar coordinates of the port voltages of the load nodes, and the rectangular and polar coordinates of the simplified motor model state variables, the third-order state equation of the induction motor in the simplified integrated load model is transformed to obtain the third-order state equation of the induction motor in the polar coordinate integrated load model, expressed as:

[0078]

[0079] The output power in the polar coordinate integrated load model is expressed as:

[0080]

[0081] in, To simplify the state variables of the motor model, F is the magnitude of the simplified motor model state variables, θ is the absolute phase angle of the port voltage of the load node, and φ is the absolute phase angle of the simplified motor model state variables. d F q They are respectively The d-axis and q-axis components are given, where a and b are user-defined parameters, P represents the output active power in the polar coordinate integrated load model, and Q represents the output reactive power in the polar coordinate integrated load model. z Q is the constant impedance coefficient with active power. z 'This is a custom constant impedance reactive power coefficient based on a simplified motor model.

[0082] While the simplified integrated load model reduces parameter redundancy, its state variables are F-values ​​decomposed in rectangular coordinates. d and F q In time-domain simulations, it is observed that when the system frequency is not synchronous, the voltage phase angle continuously changes. At this time, the output power of the load model remains almost constant, and the amplitude F of the internal state variables does not change significantly. However, the F of the rectangular decomposition of the motor's internal state variables... d and F q A large change from -F to F will occur, failing to directly reflect the characteristic that the external characteristics remain almost unchanged, and also failing to meet the requirement of linear change. To avoid this problem, in this embodiment, an induction motor model in polar coordinates is established, with slip, transient electromotive force amplitude, and phase angle as state variables, forming a polar coordinate integrated load model. For the polar coordinate integrated load model, the input is the absolute phase angle change rate of the port voltage. It can also be seen that the output of the motor model is affected by the rate of change of the input voltage phase angle.

[0083] In some embodiments of this application, let:

[0084]

[0085] The constraint relationship corresponding to the steady-state parameters is expressed as follows:

[0086]

[0087] The linearization parameter is expressed as:

[0088]

[0089] Substituting the linearized parameters into the polar coordinate integrated load model and eliminating steady-state quantities using the constraint relationships, the third-order state equation of the induction motor in the target load model is obtained, expressed as:

[0090]

[0091] in,

[0092]

[0093] The output power of the target load model is expressed as:

[0094]

[0095] in,

[0096]

[0097] Where ΔV is the change in port voltage of the load node, ΔF is the change in the simplified motor model state quantity, Δs is the change in slip, Δδ is the change in relative phase angle, V0 is the port voltage of the load node in steady state, δ0 is the relative phase angle in steady state, F0 is the simplified motor model state quantity in steady state, and s0 is the slip in steady state.

[0098] In this embodiment, based primarily on the assumption of small changes in linearized input, no excessive simplification was made, ensuring that the model's representational ability is as similar as possible to the original nonlinear model. Steady-state constraints are fully utilized to simplify the parameter matrix of the state-space equation, making the matrix depend only on the undetermined parameters and input / output quantities, thus making the structure of the linearized target load model more symmetrical and concise.

[0099] In some embodiments of this application, the change in the simplified motor model state variables ΔF is normalized to ΔF / F0, and the change in the port voltage of the load node ΔV is converted to ΔV / V0. Substituting the constraint relationships corresponding to the steady-state parameters into the expressions of A and B, the third-order state equation of the induction motor in the target load model is further expressed as:

[0100]

[0101] in,

[0102]

[0103] Substituting the linearization parameters into the expression for the output power of the target load model, the output power of the target load model is further expressed as:

[0104]

[0105] in,

[0106]

[0107] Among them, P m0 and Q m0 These represent the steady-state reactive power output of the motor and the active power output of the motor, respectively.

[0108] In this embodiment, F0 and δ0 are replaced with equivalent forms so that A and B can be represented as parameters {a,b,H,P}. z Q zThe model simplifies A and B by presenting the initial slip s0, steady-state voltage, steady-state active power, and steady-state reactive power, thus reducing complexity. Furthermore, by normalizing the change in the simplified motor model's state variables ΔF to ΔF / F0 and converting the change in the load node's port voltage ΔV to ΔV / V0, the model's symmetry is improved.

[0109] After the above process, a linearized target load model based on polar coordinates and steady-state constraints is obtained. To verify the effectiveness of the target load model, node voltage step and node voltage random fluctuations are used as inputs to compare the active and reactive power response characteristics of the target load model and the nonlinear model. Figure 4 The figure shown is a comparison of the active power of the linearized target load model and the nonlinear model in this application embodiment when the voltage step response occurs; as shown Figure 5 The figure shows a comparison of reactive power between the linearized target load model and the nonlinear model in this application embodiment during voltage step response; as shown. Figure 6 The figure shown is a comparison of the active power of the linearized target load model and the nonlinear model in this application embodiment when the voltage fluctuates randomly; as shown Figure 7 The figure shown is a comparison of reactive power between the linearized target load model and the nonlinear model in this application embodiment when the voltage fluctuates randomly. Figures 4-7 In the diagram, the horizontal axis represents time, and the vertical axis represents power. The blue line corresponds to the linearized model (i.e., the target load model in this embodiment), and the red line corresponds to the nonlinear model. It can be seen that when the node voltage changes slightly, the response characteristics of the linearized target load model and the nonlinear model are similar, demonstrating the effectiveness of the target load model. Therefore, it is feasible to analyze the properties of the nonlinear model using the target load model in this case.

[0110] In some embodiments of this application, after obtaining the linearized target load model, such as Figure 3 As shown, it also includes the following steps:

[0111] Step S105: Determine the transfer function of the target load model. The transfer function includes the voltage amplitude to active power transfer function, the voltage amplitude to reactive power transfer function, the voltage phase angle to active power transfer function, and the voltage phase angle to reactive power transfer function.

[0112] In this embodiment, the third-order state equation of the induction motor in the target load model is a state-space equation. The transfer function of the target load model can be determined based on the transformation relationship between the state-space equation and the transfer function. The target load model has two inputs (voltage amplitude and phase angle) and two outputs (active power and reactive power). Because the influence of the inputs on the outputs is independent in the linearized model, the transfer functions from voltage amplitude to active power, voltage amplitude to reactive power, voltage phase angle to active power, and voltage phase angle to reactive power can be obtained based on the state-space equation. Furthermore, the denominators of the transfer functions are the same, which constitute the characteristic equation of the target load model.

[0113] Step S106: Determine the Bode plot of the target load model based on the transfer function.

[0114] In this embodiment, the Bode plot refers to the amplitude-frequency characteristic and the phase-frequency characteristic. The Bode plot of the input and output of the target load model can be calculated using the transfer function.

[0115] Step S107: Determine the third-order characteristic equation of the target load model based on the state-space equation in the target load model.

[0116] The characteristic roots, damping, and other system properties of the target load model under small disturbances can be analyzed based on the third-order characteristic equation.

[0117] Step S108: Determine the output properties of the target load model based on the Bode plot and the third-order characteristic equation.

[0118] By determining the transfer function of the target load model and the Bode plot based on the transfer function, and by determining the third-order characteristic equation based on the state-space equation in the target load model, it is possible to analyze the properties of the load model more conveniently and effectively, gain a deeper understanding of the model properties, and understand the influence of parameters on the dynamic response characteristics of the load model. This is of great significance for comprehensive load model parameter identification and power system dynamic analysis.

[0119] In some embodiments of this application, the transformation formula between the transfer function and the state-space equation of the target load model is as follows:

[0120]

[0121] The characteristic equation corresponding to the state-space equation is expressed as:

[0122] |λI-A'|=0 ；

[0123] Substituting the specific parameters of A' into the characteristic equation corresponding to the state-space equation, the third-order characteristic equation of the target load model is expressed as:

[0124]

[0125] The expression corresponding to the Bode plot of the target load model is:

[0126]

[0127] Where s is the Laplace operator, G up (s) is the voltage magnitude to active power transfer function, G uq (s) is the voltage magnitude to reactive power transfer function, G θp (s) is the voltage phase angle to active power transfer function, G θq (s) is the voltage phase angle to reactive power transfer function, and |G(jω)| is the amplitude-frequency characteristic of the load model. Let λ represent the phase change from input to output at different frequency bands, λ be the eigenvalue of A', and I be the identity matrix.

[0128] By substituting a set of typical load model parameters into the target load model, the amplitude-frequency characteristics of the transfer function can be calculated, such as... Figures 8-11 As shown, based on the transfer function of the target load model using polar coordinates and steady-state constraints, the amplitude-frequency characteristic relationship between the load model's input and output is obtained. It can be seen that, as... Figure 8 As shown, the voltage amplitude to active power is bandpass, meaning the gain is high in the mid-frequency range, which can excite strong dynamics. For example... Figure 9 As shown, the voltage amplitude to reactive power is high-pass, which will induce significant dynamic changes in reactive power at high frequencies. For example... Figure 10 and Figure 11 As shown, the voltage phase angle change rate is bandpass-passed to both active and reactive power, and can only significantly excite dynamic changes in a specific frequency band. Furthermore, in terms of gain magnitude, the gain from voltage amplitude to output is stronger than the gain from phase angle change rate to output; that is, voltage amplitude is more effective than phase angle in exciting the model's output dynamic characteristics.

[0129] This application also proposes a computer device, such as... Figure 12 As shown, it includes a processor, a memory, and a computer program stored in the memory. The processor executes the computer program to implement the modeling method for a power system load model as described in any embodiment of this application.

[0130] The computer device in this application embodiment can be a terminal or other devices besides a terminal. For example, the computer device can be a mobile phone, tablet computer, laptop computer, handheld computer, in-vehicle electronic device, mobile internet device (MID), augmented reality (AR) / virtual reality (VR) device, robot, wearable device, ultra-mobile personal computer (UMPC), netbook, or personal digital assistant (PDA), etc. It can also be a server, network attached storage (NAS), personal computer (PC), television (TV), ATM, or self-service machine, etc. The embodiments disclosed in this disclosure do not impose specific limitations.

[0131] The memory may include RAM (Random Access Memory) or non-volatile memory, such as at least one disk storage device. Optionally, the memory may also be at least one storage device located remotely from the aforementioned processor.

[0132] The processors mentioned above can be general-purpose processors, including CPUs, NPs (Network Processors), etc.; they can also be DSPs (Digital Signal Processors), ASICs (Application Specific Integrated Circuits), FPGAs (Field Programmable Gate Arrays), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0133] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid-state drive), etc.

[0134] The above embodiments are merely exemplary embodiments of this application and are not intended to limit this application. The scope of protection of this application is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to this application within its substance and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of this application.

Claims

1. A modeling method for a power system load model, characterized in that, include: An initial integrated load model is established based on the third-order state equation of the induction motor and the power equation of the target static load model. The initial integrated load model is simplified based on multiple custom parameters to reduce the number of parameters in the initial integrated load model, thereby obtaining a simplified integrated load model. Based on the amplitude and absolute phase angle of the port voltage of the load node, and the amplitude and absolute phase angle of the simplified motor model state variables, the simplified integrated load model is converted into a polar coordinate integrated load model. Based on the constraint relationship corresponding to the steady-state parameters, the polar coordinate integrated load model is linearized using linearization parameters to obtain a linearized target load model. The steady-state parameters are determined when the polar coordinate integrated load model is in a steady state. The linearization parameters are determined by performing a first-order Taylor expansion on the target nonlinear parameters in the polar coordinate integrated load model.

2. The modeling method for power system load models as described in claim 1, characterized in that, Based on the amplitude and absolute phase angle of the port voltage at the load node, and the amplitude and absolute phase angle of the simplified motor model state variables, the simplified integrated load model is converted into a polar coordinate integrated load model, including: The relative phase angle is determined based on the difference between the absolute phase angle of the port voltage of the load node and the absolute phase angle of the simplified motor model state quantity; Based on the amplitude of the port voltage of the load node, the amplitude of the simplified motor model state quantity, and the relative phase angle, the simplified integrated load model is converted into a polar coordinate integrated load model.

3. The modeling method for power system load models as described in claim 2, characterized in that, The target static load model adopts a polynomial load model when the constant power load and constant current load are zero. The third-order state equation of the induction motor in the initial integrated load model is expressed as: The output power of the motor in the initial integrated load model is expressed as follows: The power equation for the target static load model in the initial integrated load model is expressed as: The output power in the initial integrated load model is expressed as: Where X is the rotor open-circuit reactance, X' is the rotor transient reactance, and T is the rotor transient reactance. d0 Let ω be the rotor open-circuit time constant, s be the slip, and ω0 be the synchronous rotational angular velocity. V is the port voltage of the load node, and V is the amplitude of the port voltage of the load node. d V q They are respectively The d-axis and q-axis components, H2 is the inertial time constant, T m T is the mechanical torque. e For electromagnetic torque, Re refers to the real part of the function value, and Im refers to the imaginary part of the function value. * Point to conjugate, P m and Q m These represent the active power and reactive power of the motor, P. L and Q L These represent the output active power and output reactive power in the initial integrated load model, E. d E q Transient electromotive force d-axis classification and q-axis components, P static and Q static Q represents the actual active and reactive power of the load at the node voltage. z It is the constant impedance coefficient for reactive power.

4. The modeling method for power system load models as described in claim 3, characterized in that, The multiple custom parameters are represented as follows: Substituting the various custom parameters into the third-order state equation of the induction motor in the initial integrated load model, and ignoring the stator resistance, makes the electromagnetic torque T... e Equal to the active power P of the motor m The third-order state equation of the induction motor in the simplified integrated load model is obtained, expressed as: set up The output power in the simplified integrated load model is expressed as:

5. The modeling method for power system load models as described in claim 4, characterized in that, The rectangular and polar coordinates of the port voltages of the load nodes, as well as the rectangular and polar coordinates of the simplified motor model state variables, are expressed as follows: The relative phase angle is defined as: δ = θ - φ; Using the rectangular and polar coordinates of the port voltages of the load nodes, and the rectangular and polar coordinates of the simplified motor model state variables, the third-order state equation of the induction motor in the simplified integrated load model is transformed to obtain the third-order state equation of the induction motor in the polar coordinate integrated load model, expressed as: The output power in the polar coordinate integrated load model is expressed as: in, To simplify the state variables of the motor model, F is the magnitude of the simplified motor model state variables, θ is the absolute phase angle of the port voltage of the load node, and φ is the absolute phase angle of the simplified motor model state variables. d F q They are respectively The d-axis and q-axis components are given, where a and b are user-defined parameters, P represents the output active power in the polar coordinate integrated load model, and Q represents the output reactive power in the polar coordinate integrated load model. z Q is the constant impedance coefficient with active power. z 'This is a custom constant impedance reactive power coefficient based on a simplified motor model.

6. The modeling method for power system load models as described in claim 5, characterized in that, make: The constraint relationship corresponding to the steady-state parameters is expressed as follows: The linearization parameter is expressed as: Substituting the linearized parameters into the polar coordinate integrated load model and eliminating steady-state quantities using the constraint relationships, the third-order state equation of the induction motor in the target load model is obtained, expressed as: in, The output power of the target load model is expressed as: in, Where ΔV is the change in port voltage of the load node, ΔF is the change in the simplified motor model state quantity, Δs is the change in slip, Δδ is the change in relative phase angle, V0 is the port voltage of the load node in steady state, δ0 is the relative phase angle in steady state, F0 is the simplified motor model state quantity in steady state, and s0 is the slip in steady state.

7. The modeling method for power system load models as described in claim 6, characterized in that, Normalizing the change in the state variables ΔF of the simplified motor model to ΔF / F0, and converting the change in the port voltage ΔV of the load node to ΔV / V0, and substituting the constraint relationships corresponding to the steady-state parameters into the expressions of A and B, the third-order state equation of the induction motor in the target load model is further expressed as: in, Substituting the linearization parameters into the expression for the output power of the target load model, the output power of the target load model is further expressed as: in, Among them, P m0 and Q m0 These represent the steady-state reactive power output of the motor and the active power output of the motor, respectively.

8. The modeling method for a power system load model as described in claim 7, characterized in that, After obtaining the linearized target load model, the following steps are also included: Determine the transfer function of the target load model, the transfer function including the voltage amplitude to active power transfer function, the voltage amplitude to reactive power transfer function, the voltage phase angle to active power transfer function, and the voltage phase angle to reactive power transfer function; The Bode plot of the target load model is determined based on the transfer function; The third-order characteristic equation of the target load model is determined based on the state-space equation in the target load model. The output properties of the target load model are determined based on the Bode plot and the third-order characteristic equation.

9. The modeling method for a power system load model as described in claim 8, characterized in that, The conversion formula between the transfer function and the state-space equation of the target load model is as follows: The characteristic equation corresponding to the state-space equation is expressed as: |λI-A'|=0; Substituting the specific parameters of A' into the characteristic equation corresponding to the state-space equation, the third-order characteristic equation of the target load model is expressed as: The expression corresponding to the Bode plot of the target load model is: Where s is the Laplace operator, G up (s) is the voltage magnitude to active power transfer function, G uq (s) is the voltage magnitude to reactive power transfer function, G θp (s) is the voltage phase angle to active power transfer function, G θq (s) is the voltage phase angle to reactive power transfer function, and |G(jω)| is the amplitude-frequency characteristic of the load model. Let λ represent the phase change from input to output at different frequency bands, λ be the eigenvalue of A', and I be the identity matrix.

10. A computer device comprising a processor, a memory, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the modeling method for the power system load model as described in any one of claims 1-9.

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