Transient stability evaluation method and system for electrical system of nuclear power plant

Abstract

The present invention relates to the field of power system automation, and provides a transient stability evaluation method and system for an electrical system of a nuclear power plant. The method comprises: constructing an alternating-current power supply system model of the nuclear power plant on the basis of a single-line diagram of the electrical system of the nuclear power plant; acquiring operating conditions of the electrical system of the nuclear power plant, and on the basis of the operating conditions, setting corresponding load conditions and system parameters; simulating the operating conditions of the power plant using the alternating-current power supply system model of the nuclear power plant, and recording an electrical quantity in a power supply switching simulation process under each operating condition; and performing transient stability evaluation on the electrical system of the nuclear power plant on the basis of the electrical quantity. By setting three quantitative criteria, a power supply switching situation of the nuclear power plant is intuitively predicted, thereby improving reliability. The present invention comprehensively considers the impact of a system on motors and the influence on a setting value of a circuit breaker during power supply switching, thereby improving the accuracy and practicality of an evaluation result. Designers and maintenance personnel can determine the feasibility of system voltage switching in advance and discover potential risks as early as possible.

Description

A method and system for transient stability assessment of electrical systems in nuclear power plants

[0001] Cross-references to related applications

[0002] This invention claims priority to Chinese Patent Application No. 202411665443.2, filed on November 20, 2024, entitled "A Transient Stability Assessment Method and System for Electrical Systems in Nuclear Power Plants", the entire contents of which are incorporated herein by reference and constitute a part of this invention for all purposes. Technical Field

[0003] This invention belongs to the field of power system automation, and particularly relates to a transient stability assessment method and system for electrical systems in nuclear power plants. Background Technology

[0004] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0005] The resilience of electrical systems after severe disturbances is crucial for the reliable and safe operation of nuclear power plants. Transient stability analysis should demonstrate that the nuclear power plant can withstand grid disturbances and maintain grid connection without causing generators to lose synchronization with the grid. Therefore, in nuclear power plant design, it is essential to analyze the dynamic response and steady-state limits of the nuclear power plant's electrical system before and after system changes or disturbances.

[0006] During normal operation of a nuclear power plant, the high-voltage auxiliary transformer is connected to the working busbar, while the standby transformer is in standby mode, with a clear division of labor between the working and standby sections. When a fault occurs on the high-voltage side of the auxiliary transformer, generator, or main step-up transformer, the circuit breaker on the low-voltage side of the high-voltage auxiliary transformer should be disconnected, and the circuit breaker on the low-voltage side of the standby transformer should be closed, thus switching the working section to the standby transformer side and completing the power supply switchover process for the nuclear power plant. During this system switchover process, malfunctions such as reactor shutdown, equipment damage, and prolonged power outages leading to production line failures may occur. Therefore, verifying whether the nuclear power plant's electrical system can withstand certain disturbances and maintain system stability during the switchover process is crucial for the normal operation of the nuclear power plant. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, this invention provides a transient stability assessment method and system for electrical systems in nuclear power plants. Under various operating conditions of the nuclear power plant, a model of the entire plant's AC power system is built. By simulating the system switching process, the changes in electrical quantities of the system after simulation are quantitatively judged, which effectively improves the accuracy and practicality of the assessment results and enables the prediction of power switching conditions in nuclear power plants.

[0008] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions:

[0009] The first aspect of this invention provides a transient stability assessment method for electrical systems in nuclear power plants;

[0010] A transient stability assessment method for electrical systems in nuclear power plants includes:

[0011] Based on the single-line diagram of the electrical system of a nuclear power plant, construct a model of the AC power system of the nuclear power plant;

[0012] Obtain the operating conditions of the electrical system of the nuclear power plant, and set the corresponding load conditions and system parameters based on the operating conditions;

[0013] The operating conditions of the power plant were simulated using the aforementioned nuclear power plant AC power system model, and the electrical quantities during the power switching simulation process under each operating condition were recorded.

[0014] A transient stability assessment of the nuclear power plant's electrical system is conducted based on the aforementioned electrical quantities.

[0015] As a further technical solution, the process of constructing a nuclear power plant AC power system model based on the single-line diagram of the nuclear power plant's electrical system is as follows:

[0016] The single-line diagram of the nuclear power plant's electrical system is input into the simulation software. The simulation software is used to simulate the connection relationship of each electrical device in the single-line diagram, and the information of each electrical device is improved by filling in the corresponding component number, name, and power parameters; in this way, the AC power system model of the nuclear power plant is constructed.

[0017] As a further technical solution, the operating conditions of the nuclear power plant's electrical system include load operating conditions, light load operating conditions, and heavy load operating conditions.

[0018] As a further technical solution, the corresponding load conditions and system parameters are set according to the operating conditions as follows: considering the characteristics of the current operating conditions, the corresponding load is selected for operation to achieve the effect of matching the actual operating conditions; the system parameters include grid parameters, plant generator parameters, transformer parameters, and transformer tap positions.

[0019] As a further technical solution, the circuit breaker state change when the system switches from the main transformer to the standby transformer state is set to simulate the system voltage switching.

[0020] As a further technical solution, the electrical quantities include the maximum inrush current of each medium-voltage motor, the maximum inrush current of the medium-voltage bus incoming circuit breaker, the phase angle value of the medium-voltage motor at the moment of switching, the terminal voltage value of the medium-voltage motor at the moment of switching, the slip rate of the medium-voltage motor at the moment of switching, and the grid parameters at the moment of switching.

[0021] As a further technical solution, the process of conducting transient stability assessment of the nuclear power plant's electrical system based on the aforementioned electrical quantities is as follows:

[0022] (1) Determine whether the ratio of the combined voltage to the frequency of the motor is not greater than a specific value when the incoming circuit breaker is closed;

[0023] (2) Whether the motor inrush current is not greater than the motor stall current;

[0024] (3) Whether the impact current of the medium-voltage busbar incoming circuit breaker is not greater than 1.2 × (total calculated current value - calculated current value of the maximum motor + starting current value of the maximum motor);

[0025] When all three conditions mentioned above are met, the electrical system of the nuclear power plant is in a transient stable state. If any condition is not met, the load conditions and system parameters are adjusted, and the simulation and electrical quantity calculations are performed again until all transient stability assessment conditions are met.

[0026] A second aspect of the present invention provides a transient stability assessment system for electrical systems in nuclear power plants.

[0027] A transient stability assessment system for electrical systems in nuclear power plants, comprising:

[0028] The nuclear power plant AC power system model building module is configured to: build a nuclear power plant AC power system model based on the single-line diagram of the nuclear power plant electrical system;

[0029] The operating condition acquisition module is configured to: acquire the operating conditions of the electrical system of the nuclear power plant, and set the corresponding load conditions and system parameters based on the operating conditions;

[0030] The simulation module is configured to: use the nuclear power plant AC power system model to simulate the power plant's operating conditions and record the electrical quantities during the power switching simulation process under each operating condition;

[0031] The transient stability assessment module is configured to perform transient stability assessments on the electrical systems of the nuclear power plant based on the electrical quantities.

[0032] A third aspect of the present invention provides a computer-readable storage medium having a program stored thereon, which, when executed by a processor, implements the steps of a transient stability assessment method for an electrical system of a nuclear power plant as described in the first aspect of the present invention.

[0033] A fourth aspect of the present invention provides an electronic device including a memory, a processor, and a program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps in a transient stability assessment method for an electrical system of a nuclear power plant as described in the first aspect of the present invention.

[0034] The above one or more technical solutions have the following beneficial effects:

[0035] (1) The transient stability assessment method for the power switching process of the electrical system of nuclear power plants proposed in this invention includes three quantitative criteria, which can predict the power switching situation of nuclear power plants through intuitive results and improve the reliability of system operation.

[0036] (2) The transient stability assessment method for the power switching process of the electrical system of nuclear power plants proposed in this invention fully considers the impact of the system on the motor and the influence on the circuit breaker setting value during power switching, which effectively improves the accuracy and practicality of the assessment results.

[0037] (3) In the transient stability assessment of the power switching process of the electrical system of a nuclear power plant, both design and operation and maintenance personnel can use this method to judge the feasibility of the system voltage switching in advance, adjust the design scheme or operation scheme of the electrical system of the nuclear power plant in a timely manner, discover potential risks as early as possible, and thus minimize losses. It has the flexibility of early perception and dynamic adjustment.

[0038] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0039] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0040] Figure 1 is a flowchart of the method in the first embodiment.

[0041] Figure 2 shows the main AC power system architecture of nuclear power plant A in the first embodiment.

[0042] Figure 3 is a system structure diagram of the second embodiment. Detailed Implementation

[0043] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0044] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0045] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0046] To address the significant impacts and system fluctuations experienced by equipment during power supply switching in existing nuclear power plants, this invention proposes a method and system for assessing whether the switching process meets transient stability requirements. This method can quantitatively determine the changes in electrical quantities in the system after simulation, effectively improving the accuracy and practicality of the assessment results and enabling the prediction of power supply switching in nuclear power plants. A detailed description with specific embodiments follows.

[0047] Example 1

[0048] This embodiment discloses a transient stability assessment method for electrical systems in nuclear power plants;

[0049] As shown in Figure 1, a transient stability assessment method for electrical systems in nuclear power plants includes:

[0050] Step S1: Construct a model of the nuclear power plant's AC power system based on the single-line diagram of the nuclear power plant's electrical system.

[0051] In one or more embodiments, the simulation software, taking the ETAP software model as an example (other software with model simulation calculation capabilities can also be used), constructs a nuclear power plant AC power system model, including:

[0052] The single-line diagram of the nuclear power plant's electrical system is input into the ETAP software. The ETAP software is then used to simulate the connection relationships of each electrical device in the single-line diagram and to complete the information of each electrical device, filling in parameters such as the corresponding component number, name, and power. In this way, a model of the nuclear power plant's AC power system is constructed.

[0053] Step S2: Select representative nuclear power plant operating conditions as simulation conditions, such as design load operating conditions, light load operating conditions, and heavy load operating conditions. Taking the design load operating condition as an example, set the corresponding load conditions and system parameters according to the operating conditions. For the load conditions, consider the characteristics of the current operating conditions and select the corresponding load to be put into operation to achieve the effect of matching the actual operating conditions. The load conditions are: the 500kV grid supplies power to the plant's service load, the plant's standby generator is offline, the prospective load is offline, the auxiliary boiler is out of operation, and the load center interconnection switch is open. The system parameters mainly include 500kV grid parameters, 220kV grid parameters, transformer parameters, transformer tap positions, etc., which are set according to the characteristics of the current nuclear power plant site.

[0054] Step S3: Simulate the power plant's operating conditions using the nuclear power plant's AC power system model, and record the electrical quantities during the power switching simulation under each operating condition. These electrical quantities include: the maximum inrush current of each medium-voltage motor; the maximum inrush current of the medium-voltage bus incoming circuit breaker; the phase angle value of the medium-voltage motor at the moment of switching; the terminal voltage value of the medium-voltage motor at the moment of switching; the slip rate of the medium-voltage motor at the moment of switching; and the grid parameters (grid voltage and phase angle difference) at the moment of switching.

[0055] Step S4: Perform transient stability assessment based on the electrical quantities, and calculate whether the assessment conditions for each operating condition meet the requirements. The assessment conditions include:

[0056] (1) When the incoming circuit breaker is closed, the ratio of the motor's combined voltage to its frequency shall not exceed 133%. The calculation method for the motor's combined voltage is as follows:

[0057] In the formula: E R E represents the combined voltage of the motor; S E represents the equivalent voltage of the system. m δ represents the equivalent voltage at the motor terminal; δ represents the phase angle difference between the system voltage and the motor voltage.

[0058] (2) The motor inrush current shall not exceed the motor stall current;

[0059] (3) The impact current of the medium-voltage busbar incoming circuit breaker shall not exceed 1.2 × (total calculated current value - calculated current value of the maximum motor + starting current value of the maximum motor).

[0060] Furthermore, in this embodiment, if any operating condition fails to meet the transient stability assessment conditions, the system architecture or parameters need to be adjusted, and the process of steps S1 to S4 needs to be repeated until all operating conditions meet the transient stability assessment conditions. Then, it can be considered that the system meets the transient stability requirements during voltage switching.

[0061] To verify the effectiveness of the method provided in this embodiment, a nuclear power plant A in China is used as an example. The primary voltage of the plant service transformer is 500kV, and the primary voltage of the standby transformer is 220kV. During normal operation of the nuclear power plant, the high-voltage plant service transformer is connected to the working bus, and the standby transformer is in standby mode, with a clear division of labor between the working section and the standby section. When a fault occurs on the high-voltage side of the plant service transformer, generator, or main step-up transformer, the circuit breaker on the low-voltage side of the high-voltage plant service transformer should be disconnected, and the circuit breaker on the low-voltage side of the standby transformer should be closed, that is, the working section should be switched to the standby transformer side. The system architecture is shown in Figure 2.

[0062] Under each operating condition, the circuit breaker states change during the system's switch from the main transformer to the standby transformer state to simulate system voltage switching. Taking one operating condition as an example, assuming the system power supply switch is caused by a fault in the plant auxiliary transformer, the main changes in the system circuit breakers are as follows:

[0063] When the secondary bus UAT-2A-X of the plant service transformer ZAS-ET-2A0s is in operation, a three-phase fault occurs. At 98.3ms, the medium-voltage circuit breakers of the 10.5kV medium-voltage bus ES-1 to ES-6 open, and the three-phase fault is cleared. The power supply is quickly switched from the 500kV system to the 220kV system. 5ms later, the circuit breakers of each medium-voltage bus connected to the RAT transformer close, and the quick switch is completed (the switching time is set according to the specific situation of each nuclear power plant, and this is only for illustration).

[0064] Record the following electrical quantities during the power switching simulation for each operating condition, and calculate whether the following three evaluation conditions are met for each operating condition. Considering the actual situation of nuclear power plant A in the case study, and the dimensions of the data read after simulation, the above formulas are processed. The processed calculation formulas are as follows:

[0065] Nuclear power plant A used the above formula to verify the simulation results of the medium-voltage motor, and extracted some of the verification results for the motor. The verification results are as follows:

[0066] Table 1. Verification Table of Synthetic Voltage for Medium-Voltage Motors in Part A of Nuclear Power Plants

[0067] (2) The motor inrush current is not greater than the motor stall current. Taking domestic nuclear power plant A as an example, the specific judgment conditions are as follows:

[0068] Table 2 Limits of Inrush Current for Medium Voltage Motors

[0069] (3) The inrush current of the medium-voltage busbar incoming circuit breaker shall not exceed 1.2 × (total calculated current value - calculated current value of the largest motor + starting current value of the largest motor). Taking domestic nuclear power plant A as an example, the specific judgment conditions are as follows:

[0070] Table 3. Limits of Inrush Current for Medium Voltage Busbar Incoming Circuit Breakers

[0071] Example 2

[0072] This embodiment discloses a transient stability assessment system for electrical systems in nuclear power plants;

[0073] As shown in Figure 3, a transient stability assessment system for electrical systems in nuclear power plants includes:

[0074] The nuclear power plant AC power system model building module is configured to: build a nuclear power plant AC power system model based on the single-line diagram of the nuclear power plant electrical system;

[0075] The operating condition acquisition module is configured to: acquire the operating conditions of the electrical system of the nuclear power plant, and set the corresponding load conditions and system parameters based on the operating conditions;

[0076] The simulation module is configured to: use the nuclear power plant AC power system model to simulate the power plant's operating conditions and record the electrical quantities during the power switching simulation process under each operating condition;

[0077] The transient stability assessment module is configured to perform transient stability assessments on the electrical systems of the nuclear power plant based on the electrical quantities.

[0078] Example 3

[0079] The purpose of this embodiment is to provide a computer-readable storage medium.

[0080] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in a transient stability assessment method for an electrical system of a nuclear power plant as described in Embodiment 1 of this disclosure.

[0081] Example 4

[0082] The purpose of this embodiment is to provide an electronic device.

[0083] An electronic device includes a memory, a processor, and a program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps in a transient stability assessment method for an electrical system of a nuclear power plant as described in Embodiment 1 of this disclosure.

[0084] The steps and methods involved in the apparatuses of Embodiments 2, 3, and 4 above correspond to those in Embodiment 1. For specific implementation details, please refer to the relevant description section of Embodiment 1. The term "computer-readable storage medium" should be understood as a single medium or multiple media including one or more instruction sets; it should also be understood as including any medium capable of storing, encoding, or carrying an instruction set for execution by a processor and enabling the processor to perform any of the methods in this invention.

[0085] Those skilled in the art will understand that the modules or steps of the present invention described above can be implemented using general-purpose computer devices. Optionally, they can be implemented using computer-executable program code, thereby allowing them to be stored in a storage device for execution by a computer device, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. The present invention is not limited to any particular combination of hardware and software.

[0086] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A transient stability assessment method for electrical systems in nuclear power plants, characterized in that, include: Based on the single-line diagram of the electrical system of a nuclear power plant, construct a model of the AC power system of the nuclear power plant; Obtain the operating conditions of the electrical system of the nuclear power plant, and set the corresponding load conditions and system parameters based on the operating conditions; The operating conditions of the power plant were simulated using the aforementioned nuclear power plant AC power system model, and the electrical quantities during the power switching simulation process under each operating condition were recorded. A transient stability assessment of the nuclear power plant's electrical system is conducted based on the aforementioned electrical quantities.

2. The transient stability assessment method for electrical systems in nuclear power plants as described in claim 1, characterized in that, The process of constructing a nuclear power plant AC power system model based on the single-line diagram of the nuclear power plant's electrical system is as follows: The single-line diagram of the nuclear power plant's electrical system is input into the simulation software. The simulation software is used to simulate the connection relationship of each electrical device in the single-line diagram, and the information of each electrical device is improved by filling in the corresponding component number, name, and power parameters; in this way, the AC power system model of the nuclear power plant is constructed.

3. The transient stability assessment method for electrical systems in nuclear power plants as described in claim 1, characterized in that, The operating conditions of the nuclear power plant's electrical system include load operating conditions, light load operating conditions, and heavy load operating conditions.

4. The transient stability assessment method for electrical systems in nuclear power plants as described in claim 1, characterized in that, The specific steps for setting the corresponding load conditions and system parameters based on the operating conditions are as follows: considering the characteristics of the current operating conditions, select the corresponding load to be put into operation in order to achieve the effect of matching the actual operating conditions; the system parameters include grid parameters, plant generator parameters, transformer parameters, and transformer tap positions.

5. The transient stability assessment method for electrical systems in nuclear power plants as described in claim 1, characterized in that, The system voltage switching is simulated by setting the circuit breaker state change when the system switches from the main transformer to the standby transformer state.

6. The transient stability assessment method for an electrical system in a nuclear power plant as described in claim 1, characterized in that, The electrical quantities include the maximum inrush current of each medium-voltage motor, the maximum inrush current of the medium-voltage bus incoming circuit breaker, the phase angle value of the medium-voltage motor at the moment of switching, the terminal voltage value of the medium-voltage motor at the moment of switching, the slip rate of the medium-voltage motor at the moment of switching, and the grid parameters at the moment of switching.

7. The transient stability assessment method for an electrical system in a nuclear power plant as described in claim 1, characterized in that, The process of conducting a transient stability assessment of the nuclear power plant's electrical system based on the aforementioned electrical quantities is as follows: (1) Determine whether the ratio of the combined voltage to the frequency of the motor is not greater than a specific value when the incoming circuit breaker is closed; (2) Whether the motor inrush current is not greater than the motor stall current; (3) Whether the impact current of the medium-voltage busbar incoming circuit breaker is not greater than 1.2 × (total calculated current value - calculated current value of the maximum motor + starting current value of the maximum motor); When all three conditions mentioned above are met, the electrical system of the nuclear power plant is in a transient stable state. If any condition is not met, the load conditions and system parameters are adjusted, and the simulation and electrical quantity calculations are performed again until all transient stability assessment conditions are met.

8. A transient stability assessment system for electrical systems in nuclear power plants, characterized in that: include: The nuclear power plant AC power system model building module is configured to: build a nuclear power plant AC power system model based on the single-line diagram of the nuclear power plant electrical system; The operating condition acquisition module is configured to: acquire the operating conditions of the electrical system of the nuclear power plant, and set the corresponding load conditions and system parameters based on the operating conditions; The simulation module is configured to: use the nuclear power plant AC power system model to simulate the power plant's operating conditions and record the electrical quantities during the power switching simulation process under each operating condition; The transient stability assessment module is configured to perform transient stability assessments on the electrical systems of the nuclear power plant based on the electrical quantities.

9. A computer-readable storage medium having a program stored thereon, characterized in that, When executed by the processor, the program implements the steps in the transient stability assessment method for electrical systems of nuclear power plants as described in any one of claims 1-7.

10. An electronic device comprising a memory, a processor, and a program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps in the transient stability assessment method for an electrical system of a nuclear power plant as described in any one of claims 1-7.

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