A power grid transient voltage stability evaluation method, system, device and medium

Abstract

The patent application provides a power grid transient voltage stability evaluation method, system, device and medium, comprising: adopting an induction motor model, a distributed photovoltaic model and a constant impedance current power ZIP static load model, correcting a power flow equation of the power grid to obtain the power flow equation; based on the active power and voltage amplitude of the load node in the obtained power grid, combining the power flow equation, calculating the load node power voltage P-V curve of the power grid; according to the load node power voltage P-V curve, the induction motor stability boundary of the power grid and the distributed photovoltaic stability boundary of the power grid, obtaining the transient voltage stability evaluation result of the power grid; when constructing the power flow equation, not only the induction motor model and the distributed photovoltaic model are considered, but also the ZIP static load model is considered, so that the load node power voltage P-V curve with higher accuracy is obtained on the basis of the power flow equation.

Description

Technical Field

[0001] This invention patent application belongs to the field of power system and new energy power generation technology, specifically relating to a method, system, equipment and medium for evaluating the transient voltage stability of a power grid. Background Technology

[0002] With the large-scale integration of photovoltaic (PV) systems into the power grid, the reactive power and voltage interaction processes during grid faults involve numerous nonlinear expressions involving differentiation, integration, limiting, and integers, increasing the complexity of grid transient stability assessment. The direct method, by comparing the initial energy of the system after fault clearing with the critical energy, directly determines grid transient stability. It does not rely on numerical integration methods and has advantages such as clear physical meaning, fast calculation speed, and the ability to quantitatively determine system stability, making it the mainstream method for transient stability analysis of new power systems. The equal-area principle based on the PV (Power-Voltage) curve is one of the most mature and widely used direct methods. However, the transient response characteristics of distributed PV differ from those of traditional synchronous generators, and its connection to the near end of the load causes a new shape in the system's PV curve, resulting in a corresponding change in the system's stability boundary.

[0003] The 2015 paper by K. Kawabe and K. Tanaka, entitled "Impact of Dynamic Behavior of Photovoltaic Power Generation Systems on Short-Term Voltage Stability," treats the induction motor as a constant impedance load in a single-machine infinite bus system containing distributed photovoltaic (PV) power and induction motors. Based on the PV characteristics of distributed PV during steady-state and fault ride-through, it calculates the PV curves at the load nodes and compares them with the load characteristic curves of the induction motors to determine the stability boundary of the system. The 2024 paper by Lan Tiankai, Sun Huadong, Xu Shiyun, et al., entitled "Transient Voltage Instability Phenomenon and Mechanism of Power Systems Dominated by Low-Voltage Ride-Through of New Energy," considers the ride-through control characteristics of distributed PV in an equivalent model of a power system containing distributed PV, modeling the PV as a ZIP static load. It calculates the PV curve of the system, establishes a hybrid system model characterizing the dynamic behavior of continuous and repeated ride-through of distributed PV, calculates the stability boundary of the system, and provides a method for instability discrimination.

[0004] The method in the paper "Impact of Dynamic Behavior of Photovoltaic Power Generation Systems on Short-Term Voltage Stability" determines the transient voltage stability of the system using PV curves based on the dynamic characteristics of distributed photovoltaic (PV) systems and load characteristic curves based on the dynamic characteristics of induction motors. However, it lacks consideration of the PV characteristics of ZIP static loads, resulting in inaccurate PV curves. The method in the paper "Transient Voltage Instability Phenomena and Mechanisms of Power Systems Dominated by Low-Voltage Ride-Through in New Energy Sources" determines the transient voltage stability of the system using PV curves based on the fault ride-through and switching control characteristics of distributed PV systems (during the transient process, distributed PV systems exist in three different operating states due to the influence of generator terminal voltage: normal operation, low-voltage ride-through operation, and low-voltage ride-through recovery. Depending on changes in generator terminal voltage, the operating state of distributed PV systems may switch between these three states) and an instability discrimination method based on a hybrid system model. However, it lacks consideration of the load characteristics of induction motors, resulting in inaccurate stability boundaries. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this patent application proposes a method for evaluating the transient voltage stability of a power grid, comprising:

[0006] During grid operation, the original power flow equations during grid operation are modified using an induction motor model, a distributed photovoltaic model, and a constant impedance current-power ZIP static load model constructed based on the grid's operating parameters, to obtain the final power flow equations.

[0007] Based on the obtained active power and voltage amplitude of the load nodes in the power grid, and combined with the power flow equation, the continuous power flow method is used to calculate the power-voltage (PV) curves of the load nodes in the power grid.

[0008] Based on the load node power-voltage (PV) curves, the grid's induction motor stability boundary, and the grid's distributed photovoltaic (PV) stability boundary, combined with the switching control characteristics of distributed PV, the transient voltage stability assessment results of the grid are obtained.

[0009] Preferably, the power grid operation period includes: a steady-state period and a transient period; the induction motor model includes: a steady-state model and a transient model; the distributed photovoltaic model includes: a steady-state model and a transient model; during power grid operation, the original power flow equations during power grid operation are modified using the induction motor model, the distributed photovoltaic model, and the constant impedance current-power ZIP static load model constructed based on the power grid operating parameters to obtain the final power flow equations, including:

[0010] During the steady state of the power grid, based on the steady-state operating parameters, the original steady-state power flow equations during the power grid operation period are modified using the steady-state model of induction motors, the steady-state model of distributed photovoltaics, and the ZIP static load model constructed according to the power grid operating parameters, so as to obtain the final steady-state power flow equations.

[0011] During the power grid transient period, based on the transient operating parameters, the original transient power flow equations during power grid operation are modified using the transient model of induction motor, the transient model of distributed photovoltaic, and the ZIP static load model constructed according to the power grid operating parameters, so as to obtain the final transient power flow equations.

[0012] Preferably, during the steady-state period of the power grid, based on the steady-state operating parameters, the original steady-state power flow equations during power grid operation are modified using an induction motor steady-state model, a distributed photovoltaic steady-state model, and a ZIP static load model constructed according to the power grid operating parameters, to obtain the final steady-state power flow equations, including:

[0013] During the steady state of the power grid, based on the steady-state operating parameters, the original steady-state power flow equations are modified once using an induction motor steady-state model;

[0014] Based on the constant current load in the ZIP static load model, the original steady-state power flow equation after the first correction is modified a second time.

[0015] Based on the distributed photovoltaic steady-state model, the original steady-state power flow equations after the second correction are modified a third time to obtain the final steady-state power flow equations of the power grid.

[0016] The induction motor steady-state model is constructed based on the PV characteristics of the induction motor in the power grid during the steady-state period; the distributed photovoltaic steady-state model is constructed based on the PV characteristics of the distributed photovoltaic in the power grid during the steady-state period; and the ZIP static load model is constructed based on the power consumed by the constant impedance in the power grid, the power corresponding to the constant current load, and the constant power component.

[0017] Preferably, during the power grid transient period, based on transient operating parameters, the original transient power flow equations during power grid operation are modified using an induction motor transient model, an induction motor transient model, and a ZIP static load model constructed based on the power grid operating parameters, to obtain the final transient power flow equations, including:

[0018] During the power grid transient, based on the transient operating parameters, the original transient power flow equations are corrected once using the induction motor transient model combined with the distributed photovoltaic transient model;

[0019] Based on the constant power load of the ZIP static load model, the original transient power flow equation after the first correction is modified a second time to obtain the final transient power flow equation.

[0020] The transient model of the induction motor is constructed based on the PV characteristics of the induction motor in the power grid during the power grid transient period; the steady-state model of the distributed photovoltaic is constructed based on the PV characteristics of the distributed photovoltaic in the power grid during the power grid transient period.

[0021] Preferably, the load node power-voltage (PV) curve includes: a first segment of the load node power-voltage (PV) curve, a second segment of the load node power-voltage (PV) curve, and a third segment of the load node power-voltage (PV) curve; the calculation of the load node power-voltage (PV) curve of the power grid based on the obtained active power and voltage amplitude of the load nodes in the power grid, combined with the power flow equation, using the continuous power flow method, includes:

[0022] Using the active power of load nodes in the power network as the growth rate, based on the steady-state power flow equation and the continuous power flow method, the power-voltage PV curve of the load nodes in the power network above the static voltage stability critical interval is calculated as the first segment of the load node power-voltage PV curve.

[0023] Using the load node voltage amplitude as the reduction amount, based on the steady-state power flow equation, the continuous power flow method is used to calculate the load node power-voltage PV curve in the critical range of static voltage stability in the power network, which is used as the second load node power-voltage PV curve.

[0024] Using the active power of the load node as the reduction amount, based on the transient power flow equation and the continuous power flow method, the load node power-voltage PV curve below the static voltage stability critical range in the power network is calculated as the third segment of the load node power-voltage PV curve.

[0025] Preferably, the step of using the active power of load nodes in the power network as the growth rate, based on the steady-state power flow equation, and employing the continuous power flow method to calculate the load node power-voltage PV curve above the static voltage stability critical interval in the power network, as the first segment of the load node power-voltage PV curve, includes:

[0026] Based on the steady-state power flow equations, the state variable matrix is ​​obtained; the state variable matrix includes state variables.

[0027] Based on the current state variables and the current node power growth coefficient, the tangent prediction method is used to calculate the estimated values ​​of the state variables and the estimated values ​​of the node power growth coefficient at the next step size.

[0028] Based on the estimated state variables and the active power of the load node at the next step point, calculate the increase factor of the active power of the load node.

[0029] Based on the estimated state variables at the next step point, the estimated node power growth coefficient at the next step point, and the increase factor of the active power of the load node, plot the load node power-voltage (PV) curve.

[0030] The state variable estimate and the node power growth coefficient estimate at the next step point are iterated repeatedly until the load node approaches the static voltage stability critical range. Then the plotting of the load node power voltage PV curve is stopped, and the load node power voltage PV curve above the static voltage stability critical range is obtained as the first segment of the load node power voltage PV curve.

[0031] Preferably, the step of obtaining the transient voltage stability assessment result of the power grid based on the load node power-voltage (PV) curve, the induction motor stability boundary of the power grid, and the distributed photovoltaic (PV) stability boundary of the power grid, combined with the switching control characteristics of the distributed PV, includes:

[0032] When a static load is connected to a load node, the power grid is stable when the PV characteristics of the power grid system are above the static voltage stability critical range; the power grid is unstable when the PV characteristics of the power grid system are below the static voltage stability critical range.

[0033] When an induction motor is connected to a load node, the stability boundary of the induction motor is plotted. Based on the stability boundary of the induction motor, the transient voltage stability boundary on the power-voltage (PV) curve of the load node is determined. When the PV characteristics of the power grid system are within the transient voltage stability boundary, the power grid is stable. If the PV characteristics of the power grid system are outside the transient voltage stability boundary, the power grid is unstable.

[0034] When an induction motor and distributed photovoltaic (PV) are connected to a load node, the stability boundaries of the induction motor and distributed PV are plotted. Based on the stability boundaries of the induction motor and distributed PV, the transient voltage stability boundary on the power-voltage (PV) curve of the load node is determined. When the PV characteristics of the power grid system are within the transient voltage stability boundary, the power grid is stable. If the PV characteristics of the power grid system are outside the transient voltage stability boundary, the power grid is unstable.

[0035] The stability boundary of the induction motor is determined based on the load node power-voltage (PV) curves at different speeds during the steady state of the power grid, combined with the swing equation of the induction motor; the stability boundary of the distributed photovoltaic system is determined based on the hybrid system model.

[0036] Based on the same inventive concept, this patent application also provides a power grid transient voltage stability assessment system, including: a power flow equation determination module, a PV curve calculation module, and a power grid transient voltage evaluation module;

[0037] The power flow equation determination module is used to modify the original power flow equations during grid operation by using an induction motor model, a distributed photovoltaic model, and a constant impedance current-power ZIP static load model constructed based on the grid's operating parameters, in order to obtain the final power flow equations.

[0038] The PV curve calculation module is used to calculate the power-voltage PV curve of the load nodes of the power grid based on the obtained active power and voltage amplitude of the load nodes in the power grid, combined with the power flow equation, using the continuous power flow method.

[0039] The power grid transient voltage evaluation module is used to obtain the power grid transient voltage stability evaluation result based on the load node power voltage PV curve, the power grid induction motor stability boundary, and the power grid distributed photovoltaic stability boundary, combined with the switching control characteristics of distributed photovoltaic.

[0040] Preferably, the power grid operation period includes: a steady-state period and a transient period; the induction motor model includes: a steady-state model and a transient model; the distributed photovoltaic model includes: a steady-state model and a transient model; the power flow equation determination module includes:

[0041] The steady-state power flow equation determination submodule is used to modify the original steady-state power flow equation during the steady-state period of the power grid based on the steady-state operating parameters, using the induction motor steady-state model, the distributed photovoltaic steady-state model and the ZIP static load model constructed according to the operating parameters of the power grid, so as to obtain the final steady-state power flow equation.

[0042] The transient power flow equation determination submodule is used to modify the original transient power flow equations during the power grid operation period based on transient operating parameters, using an induction motor transient model, a distributed photovoltaic transient model, and a ZIP static load model constructed according to the power grid operating parameters, to obtain the final transient power flow equations.

[0043] Preferably, the steady-state power flow equation determination submodule is specifically used to: during the steady state of the power grid, based on the steady-state operating parameters, use an induction motor steady-state model to modify the original steady-state power flow equation once;

[0044] Based on the constant current load in the ZIP static load model, the original steady-state power flow equation after the first correction is modified a second time.

[0045] Based on the distributed photovoltaic steady-state model, the original steady-state power flow equations after the second correction are modified a third time to obtain the final steady-state power flow equations of the power grid.

[0046] The induction motor steady-state model is constructed based on the PV characteristics of the induction motor in the power grid during the steady-state period; the distributed photovoltaic steady-state model is constructed based on the PV characteristics of the distributed photovoltaic in the power grid during the steady-state period; and the ZIP static load model is constructed based on the power consumed by the constant impedance in the power grid, the power corresponding to the constant current load, and the constant power component.

[0047] Preferably, the transient power flow equation determination submodule is specifically used for:

[0048] During the power grid transient, based on the transient operating parameters, the original transient power flow equations are corrected once using the induction motor transient model combined with the distributed photovoltaic transient model;

[0049] Based on the constant power load of the ZIP static load model, the original transient power flow equation after the first correction is modified a second time to obtain the final transient power flow equation.

[0050] The transient model of the induction motor is constructed based on the PV characteristics of the induction motor in the power grid during the power grid transient period; the steady-state model of the distributed photovoltaic is constructed based on the PV characteristics of the distributed photovoltaic in the power grid during the power grid transient period.

[0051] Preferably, the load node power-voltage (PV) curve includes: a first load node power-voltage (PV) curve, a second load node power-voltage (PV) curve, and a third load node power-voltage (PV) curve; the power-voltage (PV) curve calculation module includes:

[0052] The first segment of the load node power-voltage PV curve calculation submodule is used to calculate the load node power-voltage PV curve above the static voltage stability critical range in the power network based on the steady-state power flow equation and the continuous power flow method, with the active power of the load nodes in the power network as the growth amount. This is used as the first segment of the load node power-voltage PV curve.

[0053] The second load node power-voltage PV curve calculation submodule is used to calculate the load node power-voltage PV curve of the load node in the power network in the critical range of static voltage stability, based on the steady-state power flow equation and the continuous power flow method, with the load node voltage amplitude as the reduction amount, as the second load node power-voltage PV curve.

[0054] The third load node power-voltage PV curve calculation submodule is used to calculate the load node power-voltage PV curve below the static voltage stability critical range in the power network, based on the transient power flow equation and using the continuous power flow method, with the active power of the load node as the reduction amount. This curve serves as the third load node power-voltage PV curve.

[0055] Preferably, the first load node power-voltage (PV) curve calculation submodule is specifically used for:

[0056] Based on the steady-state power flow equations, the state variable matrix is ​​obtained; the state variable matrix includes state variables.

[0057] Based on the current state variables and the current node power growth coefficient, the tangent prediction method is used to calculate the estimated values ​​of the state variables and the estimated values ​​of the node power growth coefficient at the next step size.

[0058] Based on the estimated state variables and the active power of the load node at the next step point, calculate the increase factor of the active power of the load node.

[0059] Based on the estimated state variables at the next step point, the estimated node power growth coefficient at the next step point, and the increase factor of the active power of the load node, plot the load node power-voltage (PV) curve.

[0060] The state variable estimate and the node power growth coefficient estimate at the next step point are iterated repeatedly until the load node approaches the static voltage stability critical range. Then the plotting of the load node power voltage PV curve is stopped, and the load node power voltage PV curve above the static voltage stability critical range is obtained as the first segment of the load node power voltage PV curve.

[0061] Preferably, the power grid transient voltage evaluation module is specifically used for:

[0062] When a static load is connected to a load node, the power grid is stable when the PV characteristics of the power grid system are above the static voltage stability critical range; the power grid is unstable when the PV characteristics of the power grid system are below the static voltage stability critical range.

[0063] When an induction motor is connected to a load node, the stability boundary of the induction motor is plotted. Based on the stability boundary of the induction motor, the transient voltage stability boundary on the power-voltage (PV) curve of the load node is determined. When the PV characteristics of the power grid system are within the transient voltage stability boundary, the power grid is stable. If the PV characteristics of the power grid system are outside the transient voltage stability boundary, the power grid is unstable.

[0064] When an induction motor and distributed photovoltaic (PV) are connected to a load node, the stability boundaries of the induction motor and distributed PV are plotted. Based on the stability boundaries of the induction motor and distributed PV, the transient voltage stability boundary on the power-voltage (PV) curve of the load node is determined. When the PV characteristics of the power grid system are within the transient voltage stability boundary, the power grid is stable. If the PV characteristics of the power grid system are outside the transient voltage stability boundary, the power grid is unstable.

[0065] The stability boundary of the induction motor is determined based on the load node power-voltage (PV) curves at different speeds during the steady state of the power grid, combined with the swing equation of the induction motor; the stability boundary of the distributed photovoltaic system is determined based on the hybrid system model.

[0066] Based on the same inventive concept, this patent application also provides an electronic device, comprising: at least one processor and a memory; wherein the memory and the processor are connected via a bus.

[0067] The memory is used to store one or more programs;

[0068] When the one or more programs are executed by the at least one processor, a power grid transient voltage stability assessment method as described above is implemented.

[0069] Based on the same inventive concept, this patent application also provides a readable storage medium having a computer program stored thereon and an executable program stored thereon, wherein when the executable program is executed, it implements the aforementioned method for evaluating the transient voltage stability of a power grid.

[0070] Compared with the closest prior art, the beneficial effects of this invention patent application are as follows:

[0071] This invention patent application provides a method, system, device, and medium for assessing the transient voltage stability of a power grid. It includes: during power grid operation, using an induction motor model, a distributed photovoltaic (PV) model, and a constant impedance current-power ZIP static load model constructed based on the power grid's operating parameters to correct the original power flow equations, obtaining the final power flow equations; based on the obtained active power and voltage amplitude of the load nodes in the power grid, combined with the power flow equations, using the continuous power flow method to calculate the load node power-voltage (PV) curves of the power grid; and based on the load node power-voltage (PV) curves, the induction motor stability boundary of the power grid, and the distributed PV stability boundary of the power grid, combined with the switching control characteristics of the distributed PV, obtaining the transient voltage stability assessment result of the power grid. This invention considers not only the induction motor model and the distributed PV model when constructing the power flow equations, but also the ZIP static load model, thus obtaining more accurate load node power-voltage (PV) curves based on the power flow equations. Furthermore, this invention considers the induction motor stability boundary and the distributed PV stability boundary when assessing the transient voltage stability of the power grid, thus improving the accuracy of the transient voltage stability assessment result based on clearly defined stability boundaries. Attached Figure Description

[0072] Figure 1 A schematic diagram of a method for evaluating transient voltage stability of a power grid provided in this patent application;

[0073] Figure 2 A flowchart of a power grid transient voltage stability assessment method based on PV curves provided for this invention patent application;

[0074] Figure 3 A schematic diagram of a power grid transient voltage stability assessment system provided for this patent application;

[0075] Figure 4 This is a schematic diagram of the structure of an electronic device provided in this patent application. Detailed Implementation

[0076] The specific embodiments of this patent application will be further described in detail below with reference to the accompanying drawings.

[0077] Example 1:

[0078] This invention patent application provides a method for evaluating the transient voltage stability of a power grid, such as... Figure 1 As shown, it includes:

[0079] Step 1: During grid operation, the original power flow equations during grid operation are modified using an induction motor model, a distributed photovoltaic model, and a constant impedance current-power ZIP static load model constructed based on the grid's operating parameters, to obtain the final power flow equations.

[0080] Step 2: Based on the obtained active power and voltage amplitude of the load nodes in the power grid, and in conjunction with the power flow equation, the continuous power flow method is used to calculate the power-voltage (PV) curves of the load nodes in the power grid.

[0081] Step 3: Based on the load node power-voltage (PV) curves, the grid's induction motor stability boundary, and the grid's distributed photovoltaic (PV) stability boundary, combined with the switching control characteristics of distributed PV, the transient voltage stability assessment results of the grid are obtained.

[0082] To address the problems of inaccurate transient voltage stability assessments caused by existing technologies failing to comprehensively consider the static load PV characteristics of ZIP (constant impedance Z, constant current I, and constant power P) and the distributed photovoltaic PV characteristics under fault ride-through strategies when calculating the PV curve of a power grid system, and failing to comprehensively consider the switching control characteristics of distributed photovoltaic systems and the load characteristics of induction motors when calculating the system stability boundary, this invention proposes a power grid transient voltage stability assessment method based on PV curves. This method scientifically assesses the transient voltage stability of power grids containing ZIP static loads, induction motors, and distributed photovoltaic systems. The PV curve is a fundamental static voltage stability analysis tool based on voltage stability mechanisms. P can represent the transmission power of a transmission section or regional tie line, or the total load of a certain area; U represents the critical bus voltage. These two parameters reflect the strength of each load node's ability to maintain voltage stability, providing the system voltage stability margin.

[0083] In one implementation, the power grid operation period includes: a steady-state period and a transient period; the induction motor model includes: a steady-state model and a transient model; the distributed photovoltaic model includes: a steady-state model and a transient model; in step 1 above, during power grid operation, the original power flow equations during power grid operation are modified using the induction motor model, the distributed photovoltaic model, and the constant impedance current-power ZIP static load model constructed based on the power grid's operating parameters, to obtain the final power flow equations, including:

[0084] During the steady state of the power grid, based on the steady-state operating parameters, the original steady-state power flow equations during the power grid operation period are modified using the steady-state model of induction motors, the steady-state model of distributed photovoltaics, and the ZIP static load model constructed according to the power grid operating parameters, so as to obtain the final steady-state power flow equations.

[0085] During the power grid transient period, based on the transient operating parameters, the original transient power flow equations during power grid operation are modified using the transient model of induction motor, the transient model of distributed photovoltaic, and the ZIP static load model constructed according to the power grid operating parameters, so as to obtain the final transient power flow equations.

[0086] For example, the ZIP static load model is a superposition of constant impedance load, constant current load, and constant power load. It can describe models of constant impedance, constant current, and constant power considering frequency domain influence factors, as well as models when the slip rate of an induction motor is zero. The ZIP static load model in a power system is a mathematical model used to describe load characteristics. It consists of three parts: power consumed by constant impedance, power corresponding to constant current load, and constant power component. The ZIP static load model refers to the relationship between load power and voltage as the voltage static characteristic of the load. In constructing the power flow equations, this invention considers not only the induction motor model and the distributed photovoltaic model, but also the ZIP static load model. Based on this, more accurate steady-state power flow equations and transient power flow equations are constructed.

[0087] In one implementation, during the steady-state period of the power grid, based on steady-state operating parameters, the original steady-state power flow equations during power grid operation are modified using an induction motor steady-state model, a distributed photovoltaic steady-state model, and a ZIP static load model constructed based on the power grid operating parameters, to obtain the final steady-state power flow equations, including:

[0088] During the steady state of the power grid, based on the steady-state operating parameters, the original steady-state power flow equations are modified once using an induction motor steady-state model;

[0089] For example, the expression for the steady-state model of an induction motor is shown below:

[0090]

[0091] Among them, T e p is the electromagnetic torque. f R is the extreme number. r ω is the rotor phase resistance, s is the rotor slip, and ω is the rotor phase resistance. s V is the angular velocity of the stator magnetic field. e R is the equivalent terminal voltage of the induction motor. e X is the equivalent resistance of the induction motor. e X is the equivalent reactance of the induction motor. r For rotor phase reactance, P sh To transmit mechanical power to the motor shaft, V s Z is the peak value of the stator rated phase voltage. m This is the equivalent impedance of the induction motor;

[0092] V e The calculation formula is as follows:

[0093]

[0094] Among them, V e R is the equivalent terminal voltage of the induction motor. s X is the stator phase resistance, j is the imaginary unit, and X is the stator phase resistance. s For stator leakage reactance, X m For the magnetizing reactance, V s This is the peak value of the stator's rated phase voltage.

[0095] R e The calculation formula is as follows:

[0096]

[0097] Among them, R e R is the equivalent resistance of the induction motor. s X is the stator phase resistance, j is the imaginary unit, and X is the stator phase resistance. s For stator leakage reactance, X m For the magnetizing reactance, X e This is the equivalent reactance of the induction motor.

[0098] Based on the steady-state model of the induction motor, the induction motor is equivalent to a constant impedance active load; based on the steady-state model of the distributed photovoltaic system, the distributed photovoltaic system is equivalent to a constant power load. The active power component of the distributed photovoltaic steady-state model is equal to the given value of the output active power of the distributed photovoltaic system in steady state, and the reactive power component is equal to the given value of the output reactive power of the distributed photovoltaic system in steady state.

[0099] Based on the constant impedance active load and the pre-obtained constant impedance reactive load, the constant impedance load is obtained. The constant impedance load is then incorporated into the nodal admittance matrix in the original steady-state power flow calculation in the form of self-impedance. Taking the constant impedance load connected to node i as an example, the original steady-state power flow equation is modified. The modification method is shown in the following equation:

[0100]

[0101] Among them, Z Z,i V is the equivalent impedance of a constant impedance load in steady state. i P represents the node voltage in the initial power flow results. Z,i Q represents the active power of a constant impedance load in steady state, where j is the imaginary unit. Z,i Y represents the reactive power of a constant impedance load in steady state. ii The self-admittance of node i after considering the synchronous generator fault calculation model, Y ii The self-admittance of the node.

[0102] Based on the constant current load in the ZIP static load model, the original steady-state power flow equation after the first correction is modified a second time.

[0103] For example, further combining the characteristics of constant current loads in the ZIP static load model, the power flow equations in steady state are modified. Taking the Newton-Raphson power flow calculation method in polar coordinates as an example, assuming that the constant current load is connected to node k, the power flow equation modification method for node k is as follows:

[0104]

[0105] Wherein, ΔP s,k Inject active power deviation ΔQ into node k after the original steady-state power flow equation is corrected. s,k Inject reactive power deviation into node k after the original steady-state power flow equation is corrected. Given the active power of node k in steady state, V represents the reactive power at node k in steady state. s,k V represents the voltage magnitude at node k in steady state. s,i Let G′ be the voltage magnitude at node i in steady state. s,ki θ is the real part of the mutual admittance of nodes k and i in the nodal admittance matrix corrected for steady state. s,ki B′ represents the phase angle difference between nodes k and i in steady state. s,ki K represents the imaginary part of the mutual admittance between nodes k and i in the nodal admittance matrix corrected for steady state. P2,k I is the active current bias coefficient of the distributed photovoltaic system at node k in steady state. P0,k Let be the active current of the distributed photovoltaic system at node k in steady state. This includes all nodes connected to node k, including node k itself.

[0106] Based on the distributed photovoltaic steady-state model, the original steady-state power flow equations after the second correction are modified a third time to obtain the final steady-state power flow equations of the power grid.

[0107] For example, further considering the characteristics of constant power load in the distributed photovoltaic steady-state model, the original steady-state power flow equation is modified again based on the second modification of the original steady-state power flow equation. Taking the Newton-Raphson power flow calculation method in polar coordinates as an example, let the constant power load be connected to node d. The power flow equation modification method for node d is shown in the following equation:

[0108]

[0109] In the formula, ΔP s,d The active power deviation injected into node d after the original steady-state power flow equation is ΔQ. s,d The reactive power deviation injected into node d after the original steady-state power flow equation is corrected. Given the active power of node d in steady state, V represents the reactive power at node d in steady state. s,i V is the voltage magnitude at node i in steady state. s,d G represents the voltage magnitude at node d in steady state. s ′ ,di B is the real part of the mutual admittance of nodes d and i in the nodal admittance matrix corrected for steady state. s ′ ,di θ represents the imaginary part of the mutual admittance between nodes d and i in the nodal admittance matrix corrected for steady state. s,di K represents the phase angle difference between nodes d and i in steady state. P2,k I is the active current bias coefficient of the distributed photovoltaic system at node k in steady state. P0,k Let be the active current of the distributed photovoltaic system at node k in steady state. This represents all nodes connected to node d, including node d and P. P,d Q represents the active power of the constant power load connected to node d in steady state. P,d S represents the reactive power of the constant power load connected to node d in steady state. PV,k K represents the rated capacity of the distributed photovoltaic system connected to node k. Q1,k V represents the reactive current minus the terminal voltage droop factor for the distributed photovoltaic system connected to node k. L,k The threshold for determining the low-voltage ride-through of distributed photovoltaic power at access node k;

[0110] The induction motor steady-state model is constructed based on the PV characteristics of the induction motor in the power grid during the grid's steady-state period; the distributed photovoltaic steady-state model is constructed based on the PV characteristics of the distributed photovoltaic in the power grid during the grid's steady-state period; and the ZIP static load model is constructed based on the power consumed by constant impedance in the power grid, the power corresponding to constant current loads, and constant power components. This invention improves the grid adaptability and accuracy of the steady-state power flow equations by modifying the steady-state power flow equations using the induction motor steady-state model, the distributed photovoltaic steady-state model, and the ZIP static load model.

[0111] In one implementation, during the power grid transient period, based on transient operating parameters, the original transient power flow equations during power grid operation are modified using an induction motor transient model, an induction motor transient model, and a ZIP static load model constructed based on the power grid operating parameters to obtain the final transient power flow equations, including:

[0112] During the power grid transient, based on the transient operating parameters, the original transient power flow equations are corrected once using the induction motor transient model combined with the distributed photovoltaic transient model;

[0113] For example, an equivalent load model, i.e., an induction motor transient model, is established based on the PV characteristics of the induction motor during the transient period. For a certain moment during the fault, the rotor slip s and the peak stator phase voltage V of the induction motor are obtained by simulation calculation. s Then, based on the expression of the transient model of the induction motor, the equivalent constant impedance active load model Z of the induction motor at that moment is calculated. m,t Equivalent constant impedance active load model Z m,t The induction motor is equivalent to a constant impedance active load, and the constant impedance active load and the pre-obtained constant impedance reactive load are taken as constant impedance loads.

[0114] Based on the low-voltage ride-through characteristics of distributed photovoltaic (PV) systems, distributed PV is modeled in a manner similar to a ZIP static load. The distributed PV low-voltage ride-through model is shown in the following equation:

[0115]

[0116] Among them, I PVp For the active current command during low-voltage ride-through of distributed photovoltaic systems, I PVq For reactive current commands during low-voltage ride-through of distributed photovoltaic systems, S PV K represents the rated capacity of distributed photovoltaic power. P1 K is the active current-terminal voltage droop factor. P2 K is the active current bias coefficient in steady state. Q1 I is the reactive current-terminal voltage droop factor. P0 V represents the active current of distributed photovoltaic systems before they enter a low-voltage ride-through phase. t V is the terminal voltage of the distributed photovoltaic system. L The threshold for determining low-voltage ride-through in distributed photovoltaic systems;

[0117] The transient model of distributed photovoltaic power is shown in the following equation:

[0118]

[0119] Among them, Z PV S is the impedance of the equivalent constant impedance load of distributed photovoltaic power generation. Ieq S represents the power of the equivalent constant current load in distributed photovoltaic systems. PV K represents the rated capacity of distributed photovoltaic power. P1 K is the active current-terminal voltage droop factor, where j is an imaginary number. Q1 K is the reactive current-terminal voltage droop factor. P2 I is the active current bias coefficient in steady state. P0 V represents the active current of distributed photovoltaic systems before they enter a low-voltage ride-through phase. tV is the terminal voltage of the distributed photovoltaic system. L The threshold for determining low voltage ride-through in distributed photovoltaic systems.

[0120] The distributed photovoltaic transient model equates distributed photovoltaics to constant impedance loads and constant current loads;

[0121] The constant impedance load is incorporated into the nodal admittance matrix of the power flow calculation in the form of its own impedance. The correction method is the same as that in steady state. Let the corrected nodal admittance matrix be Y. t ′.

[0122] Further considering the characteristics of constant current loads, the original power flow equations for transient conditions are modified. Taking the Newton-Raphson power flow calculation method in polar coordinates as an example, assuming a constant current load is connected to node k, the power flow equations for node k are modified as follows:

[0123]

[0124] Wherein, ΔP t,k The active power deviation ΔQ is injected into node k after the original transient power flow equations are corrected. t,k This refers to the reactive power deviation injected at node k after correction from the original transient power flow equations. Given the active power of node k during the transient state, V is the given reactive power of node k during the transient state. t,i V is the voltage magnitude at node i during the transient state. t,k Let G′ be the voltage magnitude at node k during the transient state. t,ki B′ is the real part of the mutual admittance of nodes k and i in the nodal admittance matrix corrected for transient conditions. t,ki θ represents the imaginary part of the mutual admittance between nodes k and i in the transient-corrected nodal admittance matrix. t,ki K represents the phase angle difference between nodes k and i during the transient state. P2,k I is the active current bias coefficient of the distributed photovoltaic system at node k in steady state. P0,k S is the active current of the distributed photovoltaic system at node k before it enters low-voltage ride-through. PV,k K represents the rated capacity of the distributed photovoltaic system connected to node k. Q1,k V represents the reactive current minus the terminal voltage droop factor for the distributed photovoltaic system connected to node k. L,k The threshold for determining the low-voltage ride-through of distributed photovoltaic power at access node k. This includes all nodes connected to node k, including node k itself.

[0125] Based on the constant power load of the ZIP static load model, the original transient power flow equation after the first correction is modified a second time to obtain the final transient power flow equation.

[0126] For example, further combining the characteristics of constant power load in the ZIP static load model, the power flow equations during transients are modified. Taking the Newton-Raphson power flow calculation method in polar coordinates as an example, assuming a constant power load is connected to node d, the power flow equation modification method for node d is as follows:

[0127]

[0128] Wherein, ΔP t,d The active power deviation injected into node d after correction by the transient power flow equation, ΔQ t,d The reactive power deviation is injected into node d after the transient power flow equation is corrected. Given the active power of node d during the transient state, V is the given reactive power of node d during transients. t,i V is the voltage magnitude at node i during the transient state. t,d G represents the voltage magnitude at node d during the transient state. t ′ ,di B represents the real part of the mutual admittance of nodes d and i in the nodal admittance matrix corrected during transients. t ′ ,di θ represents the imaginary part of the mutual admittance between nodes d and i in the transient-corrected nodal admittance matrix. t,di P represents the phase angle difference between nodes d and i during the transient state. p,d Q represents the active power of the constant power load connected to node d during transients. p,d K represents the reactive power of the constant power load connected to node d during transients. P2,k I is the active current bias coefficient of the distributed photovoltaic system at node k in steady state. P0,k S is the active current of the distributed photovoltaic system at node k in steady state. PV,k K represents the rated capacity of the distributed photovoltaic system connected to node k. Q1,k V represents the reactive current minus the terminal voltage droop factor for the distributed photovoltaic system connected to node k. L,k The threshold for determining the low-voltage ride-through of distributed photovoltaic power at access node k. This includes all nodes connected to node d, including node d itself.

[0129] The transient model of the induction motor is constructed based on the PV characteristics of the induction motor in the power grid during the power grid transient period; the steady-state model of the distributed photovoltaic is constructed based on the PV characteristics of the distributed photovoltaic in the power grid during the power grid transient period; the present invention improves the grid adaptability and accuracy of the transient power flow equation by modifying the transient power flow equation through the induction motor steady-state model, the distributed photovoltaic steady-state model and the ZIP static load model respectively.

[0130] In one implementation, the load node power-voltage (PV) curve includes: a first segment of the load node power-voltage (PV) curve, a second segment of the load node power-voltage (PV) curve, and a third segment of the load node power-voltage (PV) curve; step 2 above, based on the obtained active power and voltage amplitude of the load nodes in the power grid, combined with the power flow equation, uses the continuous power flow method to calculate the load node power-voltage (PV) curve of the power grid, including:

[0131] Using the active power of load nodes in the power network as the growth rate, based on the steady-state power flow equation and the continuous power flow method, the power-voltage PV curve of the load nodes in the power network above the static voltage stability critical interval is calculated as the first segment of the load node power-voltage PV curve.

[0132] For example, the range around 0.9pu is taken as the critical range for static voltage stability. The active power of the load node is used as the growth rate. Based on the steady-state power flow equation, the power-voltage (PV) curve of the load node above the range around 0.9pu is calculated using the continuous power flow method. 0.9pu is the critical point in the critical range for static voltage stability, also known as the static voltage collapse point, which is the nose point of the power-voltage (PV) curve. From a physical point of view, it is the point on the family of maximum power curves reached by each node in the system.

[0133] Using the load node voltage amplitude as the reduction amount, based on the steady-state power flow equation, the continuous power flow method is used to calculate the load node power-voltage PV curve in the critical range of static voltage stability in the power network, which is used as the second load node power-voltage PV curve.

[0134] For example, taking the load node voltage amplitude as the reduction amount, based on the steady-state power flow equation, and using the continuous power flow method, the portion of the load node power-voltage (PV) curve in the range near 0.9 pu is calculated, as follows:

[0135] The voltage amplitude V at node p p,gd As the variable, let the step size be δ, then the expression for the prediction step is as follows:

[0136]

[0137] In the formula, x gd V is the state variable matrix at the current time point. p,gd The voltage amplitude at node p at the current time point. Estimate the state variable matrix for the next time point. The estimated voltage amplitude at the next time point, node p; The gradient of the state variable matrix at the current time point. δ is the gradient of the voltage magnitude at node p at the current time point; δ is the step size, and generally, δ should be set < λ.

[0138] by These are the initial values ​​for the state variable matrix. Set to -1, indicating that the voltage amplitude at node p decreases. The state variable matrix and active power of node p are obtained by iterative calculation using the Newton-Raphson method to obtain the actual operating point that satisfies the steady-state power flow equation. The node power growth factor is then calculated from the active power of node p.

[0139] Continue the prediction-correction two-step process until the value of λ is less than the value recorded when the Newton-Raphson method fails to converge, meaning the power-voltage (PV) curve has moved away from the nose point to a certain extent. Stop the calculation, obtaining the portion of the power-voltage (PV) curve near the nose point at the load node.

[0140] Using the active power of the load node as the reduction amount, based on the transient power flow equation and the continuous power flow method, the load node power-voltage PV curve below the static voltage stability critical range in the power network is calculated as the third segment of the load node power-voltage PV curve.

[0141] For example, taking the active power of the load node as the reduction factor, based on the transient power flow equation and using the continuous power flow method, the power-voltage (PV) curve of the load node in the range near 0.9 pu is calculated as follows:

[0142] Let λ be treated as the variable again, and let Set to -1, meaning the active power at node p changes in a decreasing direction, and use the transient power flow equation for prediction-correction cyclic calculation until the Newton-Raphson method fails to converge or λ decreases to 0, to obtain the power-voltage PV curve of the load node in the range near 0.9pu.

[0143] In one implementation, the step of using the active power of load nodes in the power network as the growth rate, and based on the steady-state power flow equation, using the continuous power flow method to calculate the load node power-voltage (PV) curve above the static voltage stability critical interval in the power network, as the first segment of the load node power-voltage (PV) curve, includes:

[0144] Based on the steady-state power flow equations, the state variable matrix is ​​obtained; the state variable matrix includes state variables.

[0145] For example, suppose there are n+1 nodes in a power network, including 1 Vθ (balance) node, r PV (voltage control) nodes, and nr PQ (load) nodes. Vθ nodes are nodes with given voltage amplitude and phase angle, and active and reactive power to be calculated; PV nodes are nodes with given active power and voltage amplitude, and reactive power and voltage phase angle to be calculated; PQ nodes are nodes with given active and reactive power, and voltage amplitude and phase angle to be calculated.

[0146] Let the active power term in the steady-state power flow equation be ΔP. s (θ,V), the reactive power term is ΔQ s (θ,V), then the steady-state power flow equation is:

[0147] f s (x s ) T =[ΔP s (θ s V s )ΔQ s (θ s V s )]

[0148] Among them, f s (x s ) T For the steady-state power flow equation, (x s ) T ΔP is the transpose of the state variable matrix. s (θ s V s ) represents the active power term in the steady-state power flow equation, ΔP s The active power at steady state is ΔQ. s (θ s V s ) represents the reactive power term in the steady-state power flow equation, ΔQ s θ represents the reactive power in steady state. s V represents the phase difference in steady state. s This represents the voltage amplitude in steady state.

[0149] The transpose of the state variable matrix of the steady-state power flow equations is:

[0150] x s T =[θ s,1 θ s,2 …θ s,n V s,1 V s,2 …V s,n-r ]

[0151] Where, x s Tθ is the transpose of the state variable matrix of the steady-state power flow equations. s,1 Let θ be the phase difference of the first node in steady state. s,2 Let θ be the phase difference of the second node in steady state. s,n V represents the phase difference at the nth node in steady state. s,1 V is the voltage magnitude of the first node in steady state. s,2 V represents the voltage magnitude at the second node in steady state. s,n-r This represents the voltage amplitude at the nr-th node in steady state.

[0152] The transient power flow equations are:

[0153] f t (x t ) T =[ΔP t (θ t V t ) ΔQ t (θ t V t )]

[0154] Among them, f t (x t ) T For transient power flow equations, (x t ) T ΔP is the transpose of the transient state variable matrix. t (θ t V t ) represents the active power term in the transient power flow equation, ΔP t Let θ be the active power during the transient state. t V represents the phase difference during the transient state. t The voltage amplitude during the transient state is ΔQ. t (θ t V t ) represents the reactive power term in the transient power flow equations, ΔQ t reactive power during transient states;

[0155] The transpose of the state variable matrix of the transient power flow equations is:

[0156] x t T =[θ t,1 θ t,2 …θ t,n V t,1 V t,2 …V t,n-r ]

[0157] Where, x t T θ is the transpose of the state variable matrix of the transient power flow equations.t,1 Let θ be the phase difference of the first node during the transient state. t,2 Let θ be the phase difference of the second node during the transient state. t,n V represents the phase difference of the nth node during the transient state. t,1 V is the voltage amplitude of the first node during the transient state. t,2 V represents the voltage amplitude at the second node during the transient state. t,n-r This represents the voltage amplitude at the nr-th node during the transient state.

[0158] The power-voltage (PV) curves for node voltages above 0.9 pu are calculated based on steady-state power flow equations, while those for node voltages below 0.9 pu are calculated based on transient power flow equations. Since the calculation principles are the same, the power flow equation f(x) is used. T = [ΔP(θ,V)ΔQ(θ,V)] and the transpose of the state variable matrix x T =[θ1θ2…θ n V1V2…V n-r Taking [example] as an example, the calculation process of the continuous power flow method used is explained.

[0159] Based on the current state variables and the current node power growth coefficient, the tangent prediction method is used to calculate the estimated values ​​of the state variables and the estimated values ​​of the node power growth coefficient at the next step size.

[0160] Based on the estimated state variables and the active power of the load node at the next step point, calculate the increase factor of the active power of the load node.

[0161] For example, let the node power growth coefficient be λ. The tangent prediction method is used to calculate the next-point estimate of the state variables and the node power growth coefficient in the state variable matrix. This step is denoted as the prediction step. The expression for the next-step point estimate of the state variables and the node power growth coefficient is shown below:

[0162]

[0163] In the formula, Estimate the state variables for the next step size point. Let x0 be the estimated node power growth coefficient for the next step size, and λ0 be the current node power growth coefficient. The gradient of the current state variable. σ represents the gradient of the current node power growth coefficient, where σ is the step size.

[0164] The given active power at node p in the steady-state power flow equation is shown in the following equation:

[0165]

[0166] In the formula, Let be the given active power of node p in the steady-state power flow equations for node p. This is an estimate of the node power growth factor for the next step size. The given active power of node p;

[0167] Setting it to 1 indicates that the active power at node p changes in the increasing direction. As initial values ​​for the state variable matrix, the Newton-Raphson method is used to iteratively calculate the state variable matrix of the operating point that actually satisfies the steady-state power flow equation and the active power P at node p. p,1 Further by P p,1 The calculated λ1 is denoted as the correction step, and its expression is shown in the following formula:

[0168]

[0169] Where λ1 is the increase factor of the active power of the load node in the first correction step, P p,1 The active power of node p is calculated in the first correction step. Let p be the given active power of node p.

[0170] Based on the estimated state variables at the next step point, the estimated node power growth coefficient at the next step point, and the increase factor of the active power of the load node, plot the load node power-voltage (PV) curve.

[0171] The state variable estimate and the node power growth coefficient estimate at one step point are iterated repeatedly until the load node approaches the static voltage stability critical range. Then the plotting of the load node power voltage PV curve is stopped. The load node power voltage PV curve above the static voltage stability critical range is obtained as the first segment of the load node power voltage PV curve.

[0172] For example, continue with the two steps of prediction and correction. Iterate x0, Iterate λ0 until the Newton-Raphson method fails to converge, i.e., the power-voltage PV curve of the load node approaches the nose point, then stop the calculation to obtain the power-voltage PV curve of the load node in the range above 0.9pu.

[0173] In one implementation, step 3 above, which involves obtaining the transient voltage stability assessment result of the power grid based on the load node power-voltage (PV) curve, the induction motor stability boundary of the power grid, and the distributed photovoltaic (PV) stability boundary of the power grid, combined with the switching control characteristics of the distributed PV, includes:

[0174] When a static load is connected to a load node, the power grid is stable when the PV characteristics of the power grid system are above the static voltage stability critical range; the power grid is unstable when the PV characteristics of the power grid system are below the static voltage stability critical range.

[0175] For example, if there are no induction motors and distributed photovoltaics connected at node p, and only static loads are connected, then the static voltage stability critical range of the PV curve at node p is the transient voltage stability boundary of the system. If the PV characteristics of the system are below the transient voltage stability boundary, the power grid system is unstable; otherwise, the power grid system is stable.

[0176] When an induction motor is connected to a load node, the stability boundary of the induction motor is plotted. Based on the stability boundary of the induction motor, the transient voltage stability boundary on the power-voltage (PV) curve of the load node is determined. When the PV characteristics of the power grid system are within the transient voltage stability boundary, the power grid is stable. If the PV characteristics of the power grid system are outside the transient voltage stability boundary, the power grid is unstable.

[0177] For example, the power-voltage (PV) curves of the induction motor at different speeds are calculated. Based on the induction motor swing equation, the acceleration and deceleration boundary points of the induction motor at different speeds are calculated to obtain the stability boundary of the induction motor. The load node power-voltage (PV) curves of the load nodes and the stability boundary of the induction motor are compared and analyzed. Combined with the switching control characteristics of distributed photovoltaic power generation, the transient voltage stability assessment results of the power grid are obtained, as follows:

[0178] The peak value V of the stator phase voltage of the induction motor established based on the steady-state power flow equation. s and the mechanical power P transmitted to the motor shaft sh The relationship between them, at a certain speed, is used to calculate different V values. s Corresponding P sh And draw the corresponding V. s -P sh A graph showing the V values ​​across the rated speed range by varying the rotational speed. s -P sh Curve. Calculate the electromagnetic torque T at different speeds. e With load torque T m P when they are equal sh Value, which is in V s -P sh The points corresponding to these points on the curve are the acceleration / deceleration boundary points of the induction motor. When the induction motor operates on the portion of the curve below these boundary points, dω = ... s / dt<0, indicating an unstable state; when the curve portion above this point has dω sIf ∫dt>0, it is in a stable state; therefore, the curve formed by these points is the stability boundary of the induction motor. The oscillation equation of the induction motor is shown below:

[0179]

[0180] Where J is the moment of inertia, ω s T is the angular velocity of the stator magnetic field. m For the load torque, T e Let t be the electromagnetic torque, and t be the time interval.

[0181] The load torque is shown in the following formula:

[0182] T m =K(1-s) 2

[0183] In the formula, T m Where K is the load torque, K is the proportional coefficient, and s is the rotor slip.

[0184] If only an induction motor is connected at node p, plot the piecewise power-voltage (PV) curves and the stability boundary of the induction motor at node p. If the PV characteristics of the system are outside the stability boundary of the induction motor, the power grid system is unstable; otherwise, the power grid system is stable.

[0185] When an induction motor and distributed photovoltaic (PV) are connected to a load node, the stability boundaries of the induction motor and distributed PV are plotted. Based on the stability boundaries of the induction motor and distributed PV, the transient voltage stability boundary on the power-voltage (PV) curve of the load node is determined. When the PV characteristics of the power grid system are within the transient voltage stability boundary, the power grid is stable. If the PV characteristics of the power grid system are outside the transient voltage stability boundary, the power grid is unstable.

[0186] For example, if there is an induction motor and distributed photovoltaic (PV) at node p, a novel instability discrimination method based on a hybrid system model is used to obtain the stability boundary of the distributed PV. If the PV characteristics of the system are outside the stability boundary of the induction motor or distributed PV, the power grid system is unstable; otherwise, the power grid system is stable.

[0187] The stability boundary of the induction motor is determined based on the load node power-voltage (PV) curves at different speeds during the steady state of the power grid, combined with the swing equation of the induction motor. The stability boundary of the distributed photovoltaic system is determined based on the hybrid system model. When evaluating the transient voltage stability of the power grid system, this invention also considers the stability boundaries of the induction motor and the distributed photovoltaic system. Therefore, based on the clearly defined stability boundaries, the accuracy of the transient voltage stability evaluation results of the power grid system is improved.

[0188] This invention comprehensively considers the ZIP static load power-voltage (PV) characteristics and the distributed photovoltaic (PV) power-voltage (PV) characteristics under fault ride-through strategies. It also considers the distributed PV switching control characteristics and induction motor load characteristics when calculating the system stability boundary. This allows for a more accurate assessment of the transient voltage stability of grids containing integrated loads and distributed PV systems. This invention eliminates the need for simulation calculations and can quickly provide transient voltage stability assessment results for the grid. Figure 2 As shown, this invention is based on the equivalent load models of induction motors and distributed photovoltaics in steady state and transient states, corrects the power flow equations, and then uses the continuous power flow method to calculate the power-voltage (PV) curves of the load nodes. Combined with the calculated stability boundaries of induction motors and distributed photovoltaics, the transient voltage stability of the power grid under different access conditions is determined. The technical solution adopted in this invention is applicable to the analysis of power systems containing integrated loads and distributed photovoltaics. It proposes a method for assessing the transient voltage stability of the power grid based on the power-voltage (PV) curves, which can be used to assess the scope and degree of impact of severe transmission grid faults on new energy sources. This helps to propose requirements for the grid connection performance of new energy generation in a "locally appropriate" manner, assists the power grid dispatching department in reasonably formulating countermeasures and contingency plans, and supports the power grid dispatching and operation decision-making.

[0189] Example 2:

[0190] Based on the same inventive concept, this patent application also provides a power grid transient voltage stability assessment system, such as... Figure 3 As shown, it includes: a power flow equation determination module, a PV curve calculation module, and a power grid transient voltage evaluation module;

[0191] The power flow equation determination module is used to modify the original power flow equations during grid operation by using an induction motor model, a distributed photovoltaic model, and a constant impedance current-power ZIP static load model constructed based on the grid's operating parameters, in order to obtain the final power flow equations.

[0192] The PV curve calculation module is used to calculate the power-voltage PV curve of the load nodes of the power grid based on the obtained active power and voltage amplitude of the load nodes in the power grid, combined with the power flow equation, using the continuous power flow method.

[0193] The power grid transient voltage evaluation module is used to obtain the power grid transient voltage stability evaluation result based on the load node power voltage PV curve, the power grid induction motor stability boundary, and the power grid distributed photovoltaic stability boundary, combined with the switching control characteristics of distributed photovoltaic.

[0194] Preferably, the power grid operation period includes: a steady-state period and a transient period; the induction motor model includes: a steady-state model and a transient model; the distributed photovoltaic model includes: a steady-state model and a transient model; the power flow equation determination module includes:

[0195] The steady-state power flow equation determination submodule is used to modify the original steady-state power flow equation during the steady-state period of the power grid based on the steady-state operating parameters, using the induction motor steady-state model, the distributed photovoltaic steady-state model and the ZIP static load model constructed according to the operating parameters of the power grid, so as to obtain the final steady-state power flow equation.

[0196] The transient power flow equation determination submodule is used to modify the original transient power flow equations during the power grid operation period based on transient operating parameters, using an induction motor transient model, a distributed photovoltaic transient model, and a ZIP static load model constructed according to the power grid operating parameters, to obtain the final transient power flow equations.

[0197] Preferably, the steady-state power flow equation determination submodule is specifically used to: during the steady state of the power grid, based on the steady-state operating parameters, use an induction motor steady-state model to modify the original steady-state power flow equation once;

[0198] Based on the constant current load in the ZIP static load model, the original steady-state power flow equation after the first correction is modified a second time.

[0199] Based on the distributed photovoltaic steady-state model, the original steady-state power flow equations after the second correction are modified a third time to obtain the final steady-state power flow equations of the power grid.

[0200] The induction motor steady-state model is constructed based on the PV characteristics of the induction motor in the power grid during the steady-state period; the distributed photovoltaic steady-state model is constructed based on the PV characteristics of the distributed photovoltaic in the power grid during the steady-state period; and the ZIP static load model is constructed based on the power consumed by the constant impedance in the power grid, the power corresponding to the constant current load, and the constant power component.

[0201] Preferably, the transient power flow equation determination submodule is specifically used for:

[0202] During the power grid transient, based on the transient operating parameters, the original transient power flow equations are corrected once using the induction motor transient model combined with the distributed photovoltaic transient model;

[0203] Based on the constant power load of the ZIP static load model, the original transient power flow equation after the first correction is modified a second time to obtain the final transient power flow equation.

[0204] The transient model of the induction motor is constructed based on the PV characteristics of the induction motor in the power grid during the power grid transient period; the steady-state model of the distributed photovoltaic is constructed based on the PV characteristics of the distributed photovoltaic in the power grid during the power grid transient period.

[0205] Preferably, the load node power-voltage (PV) curve includes: a first load node power-voltage (PV) curve, a second load node power-voltage (PV) curve, and a third load node power-voltage (PV) curve; the PV curve calculation module includes:

[0206] The first segment of the load node power-voltage PV curve calculation submodule is used to calculate the load node power-voltage PV curve above the static voltage stability critical range in the power network based on the steady-state power flow equation and the continuous power flow method, with the active power of the load nodes in the power network as the growth amount. This is used as the first segment of the load node power-voltage PV curve.

[0207] The second load node power-voltage PV curve calculation submodule is used to calculate the load node power-voltage PV curve of the load node in the power network in the critical range of static voltage stability, based on the steady-state power flow equation and the continuous power flow method, with the load node voltage amplitude as the reduction amount, as the second load node power-voltage PV curve.

[0208] The third load node power-voltage PV curve calculation submodule is used to calculate the load node power-voltage PV curve below the static voltage stability critical range in the power network, based on the transient power flow equation and using the continuous power flow method, with the active power of the load node as the reduction amount. This curve serves as the third load node power-voltage PV curve.

[0209] Preferably, the first load node PV curve calculation submodule is specifically used for:

[0210] Based on the steady-state power flow equations, the state variable matrix is ​​obtained; the state variable matrix includes state variables.

[0211] Based on the current state variables and the current node power growth coefficient, the tangent prediction method is used to calculate the estimated values ​​of the state variables and the estimated values ​​of the node power growth coefficient at the next step size.

[0212] Based on the estimated state variables and the active power of the load node at the next step point, calculate the increase factor of the active power of the load node.

[0213] Based on the estimated state variables at the next step point, the estimated node power growth coefficient at the next step point, and the increase factor of the active power of the load node, plot the load node power-voltage (PV) curve.

[0214] The state variable estimate and the node power growth coefficient estimate at the next step point are iterated repeatedly until the load node approaches the static voltage stability critical range. Then the plotting of the load node power voltage PV curve is stopped, and the load node power voltage PV curve above the static voltage stability critical range is obtained as the first segment of the load node power voltage PV curve.

[0215] Preferably, the power grid transient voltage evaluation module is specifically used for:

[0216] When a static load is connected to a load node, the power grid is stable when the PV characteristics of the power grid system are above the static voltage stability critical range; the power grid is unstable when the PV characteristics of the power grid system are below the static voltage stability critical range.

[0217] When an induction motor is connected to a load node, the stability boundary of the induction motor is plotted. Based on the stability boundary of the induction motor, the transient voltage stability boundary on the power-voltage (PV) curve of the load node is determined. When the PV characteristics of the power grid system are within the transient voltage stability boundary, the power grid is stable. If the PV characteristics of the power grid system are outside the transient voltage stability boundary, the power grid is unstable.

[0218] When an induction motor and distributed photovoltaic (PV) are connected to a load node, the stability boundaries of the induction motor and distributed PV are plotted. Based on the stability boundaries of the induction motor and distributed PV, the transient voltage stability boundary on the power-voltage (PV) curve of the load node is determined. When the PV characteristics of the power grid system are within the transient voltage stability boundary, the power grid is stable. If the PV characteristics of the power grid system are outside the transient voltage stability boundary, the power grid is unstable.

[0219] The stability boundary of the induction motor is determined based on the load node power-voltage (PV) curves at different speeds during the steady state of the power grid, combined with the swing equation of the induction motor; the stability boundary of the distributed photovoltaic system is determined based on the hybrid system model.

[0220] Example 3

[0221] like Figure 4As shown, the present invention also provides an electronic device, which may be a computer device, a microcontroller device, a smart mobile device, etc. The electronic device in this embodiment may include a processor, a memory, a transceiver component, etc. The memory, processor, and transceiver component are connected via a bus; the memory can be used to store executable programs, and an exemplary executable program may include instructions; the processor is used to execute the instructions stored in the memory. The memory can also be used to store data, which can be accessed and / or modified when instructions are executed.

[0222] The processor may be a Central Processing Unit (CPU), or it may be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, and it is suitable for implementing one or more instructions. Specifically, it is suitable for loading and executing one or more instructions in the storage medium to implement the corresponding method flow or corresponding function, so as to implement the steps of the power grid transient voltage stability assessment method in the above embodiments.

[0223] Example 4

[0224] Based on the same inventive concept, this invention also provides a readable storage medium, specifically an electronic device readable storage medium (Memory). This readable storage medium is a memory device within an electronic device used to store programs and data. It is understood that the storage medium here can include both built-in storage media within the electronic device and extended storage media supported by the electronic device. The storage medium provides storage space, which stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more executable programs (including program code). It should be noted that the storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device. Loading and executing one or more instructions stored in the storage medium by the processor can implement the steps of the power grid transient voltage stability assessment method described in the above embodiments.

[0225] Those skilled in the art will understand that embodiments of this patent application can be provided as methods, systems, or computer program products. Therefore, this patent application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this patent application can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0226] This patent application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the patent application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing device, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0227] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0228] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0229] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this patent application and not to limit its scope of protection. Although the patent application has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading this patent application, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the application, but these changes, modifications or equivalent substitutions are all within the scope of protection of the claims pending approval.

Claims

1. A method for evaluating the transient voltage stability of a power grid, characterized in that, include: During grid operation, the original power flow equations during grid operation are modified using an induction motor model, a distributed photovoltaic model, and a constant impedance current-power ZIP static load model constructed based on the grid's operating parameters, to obtain the final power flow equations. Based on the obtained active power and voltage amplitude of the load nodes in the power grid, and combined with the power flow equation, the continuous power flow method is used to calculate the power-voltage (PV) curves of the load nodes in the power grid. Based on the load node power-voltage (PV) curves, the grid's induction motor stability boundary, and the grid's distributed photovoltaic (PV) stability boundary, combined with the switching control characteristics of distributed PV, the transient voltage stability assessment results of the grid are obtained.

2. The method as described in claim 1, characterized in that, The power grid operation period includes: a steady-state period and a transient period; the induction motor model includes: a steady-state model and a transient model; the distributed photovoltaic model includes: a steady-state model and a transient model; during power grid operation, the original power flow equations are modified using the induction motor model, the distributed photovoltaic model, and the constant impedance current-power ZIP static load model constructed based on the power grid's operating parameters, to obtain the final power flow equations, including: During the steady state of the power grid, based on the steady-state operating parameters, the original steady-state power flow equations during the power grid operation period are modified using the steady-state model of induction motors, the steady-state model of distributed photovoltaics, and the ZIP static load model constructed according to the power grid operating parameters, so as to obtain the final steady-state power flow equations. During the power grid transient period, based on the transient operating parameters, the original transient power flow equations during power grid operation are modified using the transient model of induction motor, the transient model of distributed photovoltaic, and the ZIP static load model constructed according to the power grid operating parameters, so as to obtain the final transient power flow equations.

3. The method as described in claim 2, characterized in that, During the steady-state period of the power grid, based on steady-state operating parameters, the original steady-state power flow equations during power grid operation are modified using an induction motor steady-state model, a distributed photovoltaic steady-state model, and a ZIP static load model constructed based on the power grid operating parameters, to obtain the final steady-state power flow equations, including: During the steady state of the power grid, based on the steady-state operating parameters, the original steady-state power flow equations are modified once using an induction motor steady-state model; Based on the constant current load in the ZIP static load model, the original steady-state power flow equation after the first correction is modified a second time. Based on the distributed photovoltaic steady-state model, the original steady-state power flow equations after the second correction are modified a third time to obtain the final steady-state power flow equations of the power grid. The induction motor steady-state model is constructed based on the PV characteristics of the induction motor in the power grid during the steady-state period; the distributed photovoltaic steady-state model is constructed based on the PV characteristics of the distributed photovoltaic in the power grid during the steady-state period; and the ZIP static load model is constructed based on the power consumed by the constant impedance in the power grid, the power corresponding to the constant current load, and the constant power component.

4. The method as described in claim 2, characterized in that, During the power grid transient period, based on transient operating parameters, the original transient power flow equations during power grid operation are modified using an induction motor transient model, an induction motor transient model, and a ZIP static load model constructed based on the power grid operating parameters, to obtain the final transient power flow equations, including: During the power grid transient, based on the transient operating parameters, the original transient power flow equations are corrected once using the induction motor transient model combined with the distributed photovoltaic transient model; Based on the constant power load of the ZIP static load model, the original transient power flow equation after the first correction is modified a second time to obtain the final transient power flow equation. The transient model of the induction motor is constructed based on the PV characteristics of the induction motor in the power grid during the power grid transient period; the steady-state model of the distributed photovoltaic is constructed based on the PV characteristics of the distributed photovoltaic in the power grid during the power grid transient period.

5. The method as described in claim 2, characterized in that, The load node power-voltage (PV) curve includes: a first segment of the load node power-voltage (PV) curve, a second segment of the load node power-voltage (PV) curve, and a third segment of the load node power-voltage (PV) curve; the calculation of the load node power-voltage (PV) curve of the power grid based on the obtained active power and voltage amplitude of the load nodes in the power grid, combined with the power flow equation, using the continuous power flow method, includes: Using the active power of load nodes in the power network as the growth rate, based on the steady-state power flow equation and the continuous power flow method, the power-voltage PV curve of the load nodes in the power network above the static voltage stability critical interval is calculated as the first segment of the load node power-voltage PV curve. Using the load node voltage amplitude as the reduction amount, based on the steady-state power flow equation, the continuous power flow method is used to calculate the load node power-voltage PV curve in the critical range of static voltage stability in the power network, which is used as the second load node power-voltage PV curve. Using the active power of the load node as the reduction amount, based on the transient power flow equation and the continuous power flow method, the load node power-voltage PV curve below the static voltage stability critical range in the power network is calculated as the third segment of the load node power-voltage PV curve.

6. The method as described in claim 5, characterized in that, The method uses the active power of load nodes in the power network as the growth rate, and based on the steady-state power flow equation, employs the continuous power flow method to calculate the load node power-voltage (PV) curve above the static voltage stability critical interval in the power network. This serves as the first segment of the load node power-voltage (PV) curve, including: Based on the steady-state power flow equations, the state variable matrix is ​​obtained; the state variable matrix includes state variables. Based on the current state variables and the current node power growth coefficient, the tangent prediction method is used to calculate the estimated values ​​of the state variables and the estimated values ​​of the node power growth coefficient at the next step size. Based on the estimated state variables and the active power of the load node at the next step point, calculate the increase factor of the active power of the load node. Based on the estimated state variables at the next step point, the estimated node power growth coefficient at the next step point, and the increase factor of the active power of the load node, plot the load node power-voltage (PV) curve. The state variable estimate and the node power growth coefficient estimate at the next step point are iterated repeatedly until the load node approaches the static voltage stability critical range. Then the plotting of the load node power voltage PV curve is stopped, and the load node power voltage PV curve above the static voltage stability critical range is obtained as the first segment of the load node power voltage PV curve.

7. The method as described in claim 5, characterized in that, The transient voltage stability assessment results of the power grid are obtained based on the load node power-voltage (PV) curves, the induction motor stability boundary of the power grid, and the distributed photovoltaic (PV) stability boundary of the power grid, combined with the switching control characteristics of distributed PV. These results include: When a static load is connected to a load node, the power grid is stable when the PV characteristics of the power grid system are above the static voltage stability critical range; the power grid is unstable when the PV characteristics of the power grid system are below the static voltage stability critical range. When an induction motor is connected to a load node, the stability boundary of the induction motor is plotted. Based on the stability boundary of the induction motor, the transient voltage stability boundary on the power-voltage (PV) curve of the load node is determined. When the PV characteristics of the power grid system are within the transient voltage stability boundary, the power grid is stable. If the PV characteristics of the power grid system are outside the transient voltage stability boundary, the power grid is unstable. When an induction motor and distributed photovoltaic (PV) are connected to a load node, the stability boundaries of the induction motor and distributed PV are plotted. Based on the stability boundaries of the induction motor and distributed PV, the transient voltage stability boundary on the power-voltage (PV) curve of the load node is determined. When the PV characteristics of the power grid system are within the transient voltage stability boundary, the power grid is stable. If the PV characteristics of the power grid system are outside the transient voltage stability boundary, the power grid is unstable. The stability boundary of the induction motor is determined based on the load node power-voltage (PV) curves at different speeds during the steady state of the power grid, combined with the swing equation of the induction motor; the stability boundary of the distributed photovoltaic system is determined based on the hybrid system model.

8. A power grid transient voltage stability assessment system, characterized in that, include: The power flow equation determination module, the PV curve calculation module, and the power grid transient voltage evaluation module are included. The power flow equation determination module is used to modify the original power flow equations during grid operation by using an induction motor model, a distributed photovoltaic model, and a constant impedance current-power ZIP static load model constructed based on the grid's operating parameters, in order to obtain the final power flow equations. The PV curve calculation module is used to calculate the power-voltage PV curve of the load nodes of the power grid based on the obtained active power and voltage amplitude of the load nodes in the power grid, combined with the power flow equation, using the continuous power flow method. The power grid transient voltage evaluation module is used to obtain the power grid transient voltage stability evaluation result based on the load node power voltage PV curve, the power grid induction motor stability boundary, and the power grid distributed photovoltaic stability boundary, combined with the switching control characteristics of distributed photovoltaic.

9. The system as described in claim 8, characterized in that, The power grid operation period includes: a steady-state period and a transient period; the induction motor model includes: a steady-state model and a transient model; the distributed photovoltaic model includes: a steady-state model and a transient model; the power flow equation determination module includes: The steady-state power flow equation determination submodule is used to modify the original steady-state power flow equation during the steady-state period of the power grid based on the steady-state operating parameters, using the induction motor steady-state model, the distributed photovoltaic steady-state model and the ZIP static load model constructed according to the operating parameters of the power grid, so as to obtain the final steady-state power flow equation. The transient power flow equation determination submodule is used to modify the original transient power flow equations during the power grid operation period based on transient operating parameters, using an induction motor transient model, a distributed photovoltaic transient model, and a ZIP static load model constructed according to the power grid operating parameters, to obtain the final transient power flow equations.

10. The system as described in claim 9, characterized in that, The steady-state power flow equation determination submodule is specifically used to: during the steady-state period of the power grid, based on the steady-state operating parameters, use an induction motor steady-state model to modify the original steady-state power flow equation once; Based on the constant current load in the ZIP static load model, the original steady-state power flow equation after the first correction is modified a second time. Based on the distributed photovoltaic steady-state model, the original steady-state power flow equations after the second correction are modified a third time to obtain the final steady-state power flow equations of the power grid. The induction motor steady-state model is constructed based on the PV characteristics of the induction motor in the power grid during the steady-state period; the distributed photovoltaic steady-state model is constructed based on the PV characteristics of the distributed photovoltaic in the power grid during the steady-state period; and the ZIP static load model is constructed based on the power consumed by the constant impedance in the power grid, the power corresponding to the constant current load, and the constant power component.

11. The system as described in claim 9, characterized in that, The transient power flow equation determination submodule is specifically used for: During the power grid transient, based on the transient operating parameters, the original transient power flow equations are corrected once using the induction motor transient model combined with the distributed photovoltaic transient model; Based on the constant power load of the ZIP static load model, the original transient power flow equation after the first correction is modified a second time to obtain the final transient power flow equation. The transient model of the induction motor is constructed based on the PV characteristics of the induction motor in the power grid during the power grid transient period; the steady-state model of the distributed photovoltaic is constructed based on the PV characteristics of the distributed photovoltaic in the power grid during the power grid transient period.

12. The system as described in claim 9, characterized in that, The load node power-voltage (PV) curve includes: a first segment load node power-voltage (PV) curve, a second segment load node power-voltage (PV) curve, and a third segment load node power-voltage (PV) curve; the power-voltage (PV) curve calculation module includes: The first segment of the load node power-voltage PV curve calculation submodule is used to calculate the load node power-voltage PV curve above the static voltage stability critical range in the power network based on the steady-state power flow equation and the continuous power flow method, with the active power of the load nodes in the power network as the growth amount. This is used as the first segment of the load node power-voltage PV curve. The second load node power-voltage PV curve calculation submodule is used to calculate the load node power-voltage PV curve of the load node in the power network in the critical range of static voltage stability, based on the steady-state power flow equation and the continuous power flow method, with the load node voltage amplitude as the reduction amount, as the second load node power-voltage PV curve. The third load node power-voltage PV curve calculation submodule is used to calculate the load node power-voltage PV curve below the static voltage stability critical range in the power network, based on the transient power flow equation and using the continuous power flow method, with the active power of the load node as the reduction amount. This curve serves as the third load node power-voltage PV curve.

13. The system as described in claim 12, characterized in that, The first submodule for calculating the power-voltage (PV) curve of the load node is specifically used for: Based on the steady-state power flow equations, the state variable matrix is ​​obtained; the state variable matrix includes state variables. Based on the current state variables and the current node power growth coefficient, the tangent prediction method is used to calculate the estimated values ​​of the state variables and the estimated values ​​of the node power growth coefficient at the next step size. Based on the estimated state variables and the active power of the load node at the next step point, calculate the increase factor of the active power of the load node. Based on the estimated state variables at the next step point, the estimated node power growth coefficient at the next step point, and the increase factor of the active power of the load node, plot the load node power-voltage (PV) curve. The state variable estimate and the node power growth coefficient estimate at the next step point are iterated repeatedly until the load node approaches the static voltage stability critical range. Then the plotting of the load node power voltage PV curve is stopped, and the load node power voltage PV curve above the static voltage stability critical range is obtained as the first segment of the load node power voltage PV curve.

14. The system as described in claim 12, characterized in that, The power grid transient voltage evaluation module is specifically used for: When a static load is connected to a load node, the power grid is stable when the PV characteristics of the power grid system are above the static voltage stability critical range; the power grid is unstable when the PV characteristics of the power grid system are below the static voltage stability critical range. When an induction motor is connected to a load node, the stability boundary of the induction motor is plotted. Based on the stability boundary of the induction motor, the transient voltage stability boundary on the power-voltage (PV) curve of the load node is determined. When the PV characteristics of the power grid system are within the transient voltage stability boundary, the power grid is stable. If the PV characteristics of the power grid system are outside the transient voltage stability boundary, the power grid is unstable. When an induction motor and distributed photovoltaic (PV) are connected to a load node, the stability boundaries of the induction motor and distributed PV are plotted. Based on the stability boundaries of the induction motor and distributed PV, the transient voltage stability boundary on the power-voltage (PV) curve of the load node is determined. When the PV characteristics of the power grid system are within the transient voltage stability boundary, the power grid is stable. If the PV characteristics of the power grid system are outside the transient voltage stability boundary, the power grid is unstable. The stability boundary of the induction motor is determined based on the load node power-voltage (PV) curves at different speeds during the steady state of the power grid, combined with the swing equation of the induction motor; the stability boundary of the distributed photovoltaic system is determined based on the hybrid system model.

15. An electronic device, characterized in that, include: At least one processor and memory; The memory and processor are connected via a bus; The memory is used to store one or more programs; When the one or more programs are executed by the at least one processor, a power grid transient voltage stability assessment method as described in any one of claims 1 to 7 is implemented.

16. A readable storage medium, characterized in that, It contains an execution program, which, when executed, implements a power grid transient voltage stability assessment method as described in any one of claims 1 to 7.

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