A method for analyzing voltage security of a public power grid under a new energy grid-connected operation scenario

Abstract

The application discloses a new energy grid-connected operation scene public power grid voltage safety analysis method, including the following analysis steps: S1, constructing the grid-connected gateway equivalent voltage-power response characteristic model under static voltage safety analysis; S2, using the node admittance matrix to describe the network topology relationship; S3, using the admittance matrix correction formula to correct the node admittance matrix under n-1 scene; S4, inputting the initial power of each power supply and load, and setting the grid-connected gateway equivalent model parameters; S5, solving each node voltage steady-state value; S6, comparing each node voltage with the allowable deviation range, and marking the voltage out-of-limit node; S7, calculating the load growth evaluation static voltage stability margin; S8, according to the voltage out-of-limit degree and the stability margin, dividing the grades to form a risk evaluation report; the application can quickly master the power grid voltage safety condition, and effectively improves the voltage safety and stability of the public power grid.

Description

Technical Field

[0001] This invention belongs to the field of public power grid voltage security analysis technology, specifically relating to a method for analyzing public power grid voltage security in the scenario of new energy grid connection. Background Technology

[0002] With the accelerated advancement of energy transition, a large number of distributed power sources (such as photovoltaic and wind power) and energy storage systems are being connected to the public power grid, forming a complex operation pattern of integrated power generation, grid, load, and storage. While this transformation improves energy utilization efficiency and promotes the consumption of clean energy, it also brings many challenges to the voltage security of the public power grid. As one of the important indicators of power quality, voltage stability is directly related to the safe and reliable operation of the power system and the normal operation of various electrical equipment. In the context of grid-connected operation, in-depth analysis of the voltage security status of the public power grid is of great significance for ensuring the stable operation of the power system and improving the quality of power supply.

[0003] Among them, the n-1 scenario is a typical fault scenario in the analysis of the safe and stable operation of power systems. It refers to the state in which any single component in the system (such as a line, transformer, generator, etc.) is out of operation due to fault or maintenance. In the n-1 scenario, the outage of the component will lead to changes in the grid topology and redistribution of power flow, which may cause voltage over-limit or voltage instability in local areas. Therefore, analyzing and evaluating the static stability of the voltage of the power system after the outage of a single component is very important for grid dispatching decisions and the safe and stable operation of the power system.

[0004] Therefore, in order to solve the above problems, it is necessary to develop a voltage safety analysis method for the public power grid under the scenario of new energy grid connection. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for analyzing the voltage safety of the public power grid in the scenario of new energy grid connection. The method uses voltage deviation and voltage stability margin to evaluate the voltage level of the system when it reaches a new steady state after a disturbance, which can quickly grasp the voltage safety status of the power grid and effectively improve the voltage safety and stability of the public power grid.

[0006] The objective of this invention is achieved as follows: a method for analyzing the voltage security of the public power grid under the scenario of new energy grid connection, comprising the following analysis steps:

[0007] S1. Construct a model of the equivalent voltage-power response characteristics of the parallel gateway under static voltage security analysis;

[0008] S2. Connect the parallel gateway as an equivalent node to the public power grid, and divide the public power grid into three parts: the external main grid, the new energy access area, and the load center. Use the node admittance matrix to describe the network topology.

[0009] S3. The admittance matrix of the nodes in the n-1 scenario is corrected using the admittance matrix correction formula;

[0010] S4. Based on the network topology of the n-1 scenario, input the initial power of each power source and load, and set the equivalent model parameters of the gateway interface;

[0011] S5. Solve the modified power flow equations using the Newton-Raphson method to obtain the steady-state voltage values ​​at each node;

[0012] S6. Compare the voltage of each node with the allowable deviation range, and mark the nodes whose voltage exceeds the limit;

[0013] S7. For nodes exceeding limits or weak areas, calculate load growth using the continuous power flow method and assess the static voltage stability margin.

[0014] S8. Based on the degree of voltage over-limit and stability margin, the n-1 scenario is divided into three levels: "safe", "warning", and "dangerous", and a risk assessment report is generated.

[0015] Furthermore, the construction of the equivalent voltage-power characteristic model of the parallel gateway under static voltage security analysis in step S1 specifically includes the following steps: ① generating multivariate input samples for the n-1 scenario through Monte Carlo sampling; ② performing power flow calculations for each sample under the n-1 scenario to obtain the steady-state voltage at the parallel gateway. and the corresponding injected active power reactive power Data, and form a dataset. , ③ Indicates the sample size; ③ A gradient boosting regression tree is used to construct a static voltage response model to fit the nonlinear mapping relationship between voltage and power, expressed as: In the formula: This represents the steady-state voltage at the junction of the parallel gateway. , These represent the corresponding injected active power and reactive power, respectively. express Scene identifier variables (representing the type and location of the exiting element). This represents a gradient boosting regression tree model.

[0016] Furthermore, in step S3, the formula for correcting the admittance matrix is ​​expressed as: In the formula: This represents the admittance value of the exit line.

[0017] Furthermore, the power flow equation, i.e., the power balance equation, in step S5 is specifically expressed as follows: In the formula: , They are nodes The injected active and reactive power, , They are nodes , voltage amplitude, , These are the real and imaginary parts of the nodal admittance matrix, respectively. For nodes , The voltage phase angle difference.

[0018] Furthermore, the allowable deviation range of the voltage at each node in step S6 is ±7%.

[0019] Furthermore, in step S7, the static voltage stability margin value is calculated using the continuous power flow method, and is expressed as: In the formula: This is the load growth factor. , They are nodes The injected active and reactive power, , They are nodes The initial active power and reactive power, , These are the active and reactive load growth coefficients, respectively. The reference node voltage; when When the system reaches the voltage stability limit, the static voltage stability margin is: , This is the load growth factor for the current operating point, which is usually set to 0.

[0020] Due to the adoption of the above technical solution, the beneficial effects of this invention are as follows: By constructing an equivalent voltage-power response characteristic model of the parallel gateway interface under static voltage security analysis, and connecting the parallel gateway interface as an equivalent node to the public power grid, integrating it with the power grid network topology and parameters, a complete system-level static voltage security analysis model is formed. The steady-state voltage values ​​of each node are obtained through power flow solution, and voltage over-limit checks are performed. At the same time, the static stability margin is calculated through the continuous power flow method. Combining the degree of voltage over-limit and the stability margin, the static stability of the power grid voltage under the n-1 scenario is analyzed and evaluated, the current power grid safety level is quickly determined, the risks to the safe operation of the power grid are promptly detected, the voltage safety status of the power grid is quickly grasped, and the voltage safety and stability of the public power grid are effectively improved. Attached Figure Description

[0021] Figure 1 This is a flowchart of the present invention.

[0022] Figure 2 This is a flowchart of step S1 in this invention. Detailed Implementation

[0023] The technical solution of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings.

[0024] like Figure 1 , Figure 2 As shown, a method for analyzing the voltage security of the public power grid under a new energy grid-connected operation scenario includes the following analysis steps:

[0025] S1. Construct a model of the equivalent voltage-power response characteristics of the parallel gateway interface under static voltage security analysis.

[0026] Specifically, the n-1 scenario described in this application is an electrical fault scenario in the analysis of the safe and stable operation of a power system, which refers to the state in which any single component in the system (such as a line, transformer, or generator) is taken out of operation due to a fault or maintenance; among them, static voltage safety analysis is the voltage level when the system reaches a new steady state after a disturbance.

[0027] Preferably, the construction of the equivalent voltage-power characteristic model of the parallel gateway outlet under static voltage security analysis in step S1 (same as the equivalent model of the parallel gateway outlet below) specifically includes the following steps: ① generating multivariate input samples for the n-1 scenario through Monte Carlo sampling; ② performing power flow calculations for each sample under the n-1 scenario to obtain the steady-state voltage at the parallel gateway outlet. and the corresponding injected active power reactive power Data, and form a dataset. , ③ Indicates the sample size; ③ A gradient boosting regression tree is used to construct a static voltage response model to fit the nonlinear mapping relationship between voltage and power, expressed as: In the formula: This represents the steady-state voltage at the junction of the parallel gateway. , These represent the corresponding injected active power and reactive power, respectively. express Scene identifier variables (representing the type and location of the exiting element). This represents a gradient boosting regression tree model.

[0028] Preferably, in step ①, the multivariate input samples for the n-1 scenario are generated by Monte Carlo sampling, specifically including: (1) the output of distributed power sources, including photovoltaic power and wind power output. The probability distribution of photovoltaic power output can adopt a Beta distribution, and the distribution parameters are determined based on historical sunshine data. In wind power output, the wind speed follows a Weibull distribution, and the parameters are set based on the wind speed statistics of the wind farm; (2) the active and reactive power of various loads. The load power is usually assumed to follow a normal distribution, and the mean and variance are obtained based on historical load data; (3) the charging and discharging power of the energy storage system (dynamically adjusted according to the state of charge (SOC)); (4) the types and locations of components that may be taken out of operation (such as lines, transformers, etc.). Specifically, the input variables of the equivalent voltage-power characteristic model of the grid connection port under static voltage security analysis in step S1 mainly include the output of distributed power sources (photovoltaic, wind power, etc.), the power consumption of various loads, and the charging and discharging state of the energy storage system, etc., and its output variables are the voltage and reactive power at the grid connection port.

[0029] Preferably, in step S1, during model training, the parameters are optimized by minimizing the mean square error between the predicted voltage and the actual voltage. In the formula: Indicates the number of samples. This indicates the model predicts the voltage. This represents the actual voltage obtained from the measurement.

[0030] S2. Connect the parallel gateway as an equivalent node to the public power grid, and divide the public power grid into three parts: the external main grid, the new energy access area, and the load center. Use the node admittance matrix to describe the network topology.

[0031] In step S2, the parallel gateway interface is connected to the public power grid as an equivalent node, and its static voltage characteristics are described by the aforementioned constructed GBRT model, i.e. In the formula: These are the active and reactive power values ​​at the parallel gateway interface, respectively.

[0032] S3. The admittance matrix of the nodes in the n-1 scenario is corrected using the admittance matrix correction formula.

[0033] Preferably, in step S3, the formula for correcting the admittance matrix is ​​expressed as: In the formula: This represents the admittance value of the exit line.

[0034] S4. Based on the network topology of the n-1 scenario, input the initial power of each power source and load, and set the equivalent model parameters of the gateway interface.

[0035] S5. Solve the modified power flow equations using the Newton-Raphson method to obtain the steady-state voltage values ​​at each node.

[0036] Preferably, the power flow equation, i.e., the power balance equation, in step S5 is specifically expressed as follows: In the formula: , They are nodes The injected active and reactive power, , They are nodes , voltage amplitude, , These are the real and imaginary parts of the nodal admittance matrix, respectively. For nodes , The voltage phase angle difference.

[0037] Preferably, in step S5, the power balance equation of the power system is Taylor expanded at a certain operating point using the Newton-Raphson method. After ignoring higher-order terms, a set of linear equations is obtained. The correction amount of the node voltage is obtained by iteratively solving the linear equations until the convergence condition is met.

[0038] S6. Compare the voltage of each node with the allowable deviation range, mark the nodes where the voltage exceeds the limit, and complete the voltage over-limit check.

[0039] Preferably, the allowable deviation range of the voltage at each node in step S6 is ±7%.

[0040] S7. For nodes exceeding limits or weak areas, calculate load growth using the continuous power flow method to assess the static voltage stability margin.

[0041] Preferably, in step S7, the static voltage stability margin represents the distance from the current operating point to the voltage stability limit point. Based on the equivalent model of the parallel gateway interface, the static voltage stability margin value is calculated using the continuous power flow method and is expressed as: In the formula: This is the load growth factor. , They are nodes The injected active and reactive power, , They are nodes The initial active power and reactive power, , These are the active and reactive load growth coefficients, respectively. The reference node voltage; when When the system reaches the voltage stability limit, the static voltage stability margin is: , This is the load growth factor for the current operating point, which is usually set to 0.

[0042] S8. Based on the degree of voltage over-limit and stability margin, the n-1 scenario is divided into three levels: "safe", "warning", and "dangerous", and a risk assessment report is generated.

[0043] In a specific implementation, as a preferred embodiment of the present invention, taking an industrial park as an example, when the connected 110kV line experiences an n-1 fault, the system-level static voltage safety analysis method in this application calculates that the voltage deviation of the 10kV bus in the park reaches +9.2%, and the static voltage stability margin K=0.05 (close to the critical value), which is determined to be at the "warning" level, and reactive power compensation measures need to be taken to reduce the risk.

[0044] In a specific implementation, as a preferred embodiment of the present invention, an n-1 fault event record of a real power grid (such as a 10kV line tripping event in the summer of 2023) is used to compare the steady-state voltage predicted by the system-level static voltage security analysis method in this application with the measured value. The verification index is the mean absolute percentage error (MAPE). In the formula: Indicates the number of samples. , The values ​​represent the predicted and measured steady-state voltage values, respectively. The results of 100 n-1 fault scenarios demonstrate that the mean absolute percentage error (MAPE) of the static voltage safety analysis method in this application is 2.3%, and the static voltage stability margin calculation error is less than 5%, meeting the requirements for engineering applications.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for analyzing the voltage security of a public power grid under a new energy grid-connected operation scenario, characterized in that: The analysis includes the following steps: S1. Construct a model of the equivalent voltage-power response characteristics of the parallel gateway under static voltage security analysis; S2. Connect the parallel gateway as an equivalent node to the public power grid, and divide the public power grid into three parts: the external main grid, the new energy access area, and the load center. Use the node admittance matrix to describe the network topology. S3. The admittance matrix of the nodes in the n-1 scenario is corrected using the admittance matrix correction formula; S4. Based on the network topology of the n-1 scenario, input the initial power of each power source and load, and set the equivalent model parameters of the gateway interface; S5. Solve the modified power flow equations using the Newton-Raphson method to obtain the steady-state voltage values ​​at each node; S6. Compare the voltage of each node with the allowable deviation range, and mark the nodes whose voltage exceeds the limit; S7. For nodes exceeding limits or weak areas, calculate load growth using the continuous power flow method and assess the static voltage stability margin. S8. Based on the degree of voltage exceedance and stability margin, the n-1 scenario is divided into three levels: "safe", "warning", and "dangerous", and a risk assessment report is generated.

2. The method for analyzing the voltage security of a public power grid in a new energy grid-connected operation scenario according to claim 1, characterized in that: The construction of the equivalent voltage-power characteristic model of the parallel gateway under static voltage security analysis in step S1 specifically includes the following steps: ① generating multivariate input samples for the n-1 scenario through Monte Carlo sampling; ② performing power flow calculations for each sample under the n-1 scenario to obtain the steady-state voltage at the parallel gateway. and the corresponding injected active power reactive power Data, and form a dataset. , ③ Indicates the sample size; ③ A gradient boosting regression tree is used to construct a static voltage response model to fit the nonlinear mapping relationship between voltage and power, expressed as: In the formula: This represents the steady-state voltage at the junction of the parallel gateway. , These represent the corresponding injected active power and reactive power, respectively. express Scene identifier variables (representing the type and location of the exiting element). This represents a gradient boosting regression tree model.

3. The method for analyzing the voltage security of a public power grid in a new energy grid-connected operation scenario according to claim 1, characterized in that: In step S3, the formula for correcting the admittance matrix is ​​expressed as follows: In the formula: This represents the admittance value of the exit line.

4. The method for analyzing the voltage security of a public power grid in a new energy grid-connected operation scenario according to claim 1, characterized in that: The power flow equation, i.e., the power balance equation, in step S5 is specifically expressed as follows: In the formula: , They are nodes The injected active and reactive power, , They are nodes , voltage amplitude, , These are the real and imaginary parts of the nodal admittance matrix, respectively. For nodes , The voltage phase angle difference.

5. The method for analyzing the voltage security of a public power grid in a new energy grid-connected operation scenario according to claim 1, characterized in that: The allowable deviation range for the voltage at each node in step S6 is ±7%.

6. The method for analyzing the voltage security of a public power grid in a new energy grid-connected operation scenario according to claim 1, characterized in that: In step S7, the static voltage stability margin value is calculated using the continuous power flow method, and is expressed as follows: In the formula: This is the load growth factor. , They are nodes The injected active and reactive power, , They are nodes The initial active power and reactive power, , These are the active and reactive load growth coefficients, respectively. The reference node voltage; when When the system reaches the voltage stability limit, the static voltage stability margin is: , This is the load growth factor for the current operating point, which is usually set to 0.

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