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

Abstract

The invention provides a transient stability evaluation method and system for an electrical system of a nuclear power plant, and belongs to the field of power system automation. The method comprises: constructing a nuclear power plant AC power supply system model according to a single line diagram of a nuclear power plant electrical system; acquiring operation conditions of an electrical system of the nuclear power plant, and setting corresponding load conditions and system parameters according to the operation conditions; simulating the operation conditions of the power plant by using the alternating current power supply system model of the nuclear power plant, and recording the electrical quantity in the power supply switching simulation process under each operation condition; and performing transient stability evaluation on the nuclear power plant electrical system based on the electrical quantity. By setting three quantitative criteria, the power supply switching condition of the nuclear power station is intuitively predicted, and the reliability is improved. The impact of the system on the motor and the influence on the setting value of the circuit breaker during power supply switching are comprehensively considered, and the accuracy and the practicability of an evaluation result are improved. Design and operation and maintenance personnel can judge the feasibility of system voltage switching in advance, and potential risks can be found as early as possible.

Description

Technical Field

[0001] The present invention belongs to the field of power system automation, and in particular relates to a transient stability assessment method and system for an electrical system of a nuclear power plant. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] The ability of the electrical system to recover after a severe disturbance is very important for the reliable and safe operation of the nuclear power plant. Transient stability analysis should be used to prove that the nuclear power plant can withstand the disturbance of the power grid and maintain the connection with the power grid without causing the generator to lose synchronization with the power grid. Therefore, in the design of nuclear power plants, it is very necessary to analyze the dynamic response of the nuclear power plant electrical system and the steady-state limit when the system changes or disturbances and before and after the changes.

[0004] When a nuclear power plant is operating normally, the high-voltage plant transformer carries the working busbar, the standby transformer is in standby state, and the working section and the standby section have clear division of labor; when a plant transformer, generator or high-voltage side of the main step-up transformer fails, the circuit breaker on the low-voltage side of the high-voltage plant transformer should be cut off, and the circuit breaker on the low-voltage side of the standby transformer should be closed, that is, the working section is put into the standby transformer side to realize the power switching process of the nuclear power plant. During the above system switching process, failures such as shutdown of the reactor, equipment damage, and long power outages causing the production line to be scrapped may occur. Therefore, it is very important for the normal operation of the nuclear power plant to verify whether the electrical system of the nuclear power plant can withstand certain disturbances and ensure system stability during the switching process. Summary of the invention

[0005] In order to overcome the deficiencies of the above-mentioned prior art, the present invention provides a transient stability assessment method and system for the electrical system of a nuclear power plant. Under various operating conditions of the nuclear power plant, a model of the AC power supply system of the entire plant is built. By simulating the system switching process, a quantitative judgment is made on the changes in the electrical quantities of the system after the simulation, which effectively improves the accuracy and practicality of the assessment results and realizes the prediction of the power switching situation of the nuclear power plant.

[0006] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions: A first aspect of the present invention provides a transient stability assessment method for an electrical system of a nuclear power plant; A transient stability assessment method for an electrical system of a nuclear power plant, comprising: According to the single-line diagram of the nuclear power plant electrical system, the AC power system model of the nuclear power plant is constructed; Obtaining the operating conditions of the electrical system of the nuclear power plant, and setting corresponding load conditions and system parameters according to the operating conditions; Using the nuclear power plant AC power system model to simulate the power plant operating conditions, and recording the electrical quantities in the power switching simulation process under each operating condition; A transient stability assessment of the electrical system of the nuclear power plant is performed based on the electrical quantities.

[0007] As a further technical solution, the process of constructing the nuclear power plant AC power system model according to the single-line diagram of the nuclear power plant electrical system is as follows: Input the single-line diagram of the nuclear power plant electrical system into the simulation software, use the simulation software to simulate the connection relationship of each electrical equipment in the single-line diagram, complete the information of each electrical equipment, fill in the number, name, and power parameters of the corresponding components; in this way, construct the nuclear power plant AC power supply system model.

[0008] As a further technical solution, the operating conditions of the electrical system of the nuclear power plant include load operating conditions, light load operating conditions and heavy load operating conditions.

[0009] As a further technical solution, the corresponding load conditions and system parameters are set according to the operating conditions: considering the characteristics of the current operating conditions, the corresponding load is selected for operation to achieve an effect matching the actual operating conditions; the system parameters include power grid parameters, in-plant generator parameters, transformer parameters, and transformer tap positions.

[0010] 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.

[0011] As a further technical solution, the electrical quantities include the maximum impact current of each medium-voltage motor, the maximum impact current of the medium-voltage bus incoming circuit breaker, the phase angle value of the medium-voltage motor at the switching moment, the terminal voltage value of the medium-voltage motor at the switching moment, the slip rate of the medium-voltage motor at the switching moment, and the grid parameters at the switching moment.

[0012] As a further technical solution, the process of performing transient stability assessment on the electrical system of a nuclear power plant based on the electrical quantity is as follows: (1) Determine whether the ratio of the motor composite voltage to frequency is not greater than a specific value when the incoming circuit breaker is closed; (2) Whether the motor's inrush current is not greater than the motor's stall current; (3) Whether the inrush current of the medium voltage busbar incoming circuit breaker is not greater than 1.2×, where 1.2× is the difference between the total calculated current and the calculated current value of the largest motor plus the starting current value of the largest motor; When the electrical system of a nuclear power plant meets all the above three conditions, the electrical system of the nuclear power plant is in a transient stable state. When any one of the conditions is not met, the load carrying condition and system parameters are adjusted, and the simulation and electrical quantity calculation are performed again until all transient stability assessment conditions are met.

[0013] A second aspect of the present invention provides a transient stability assessment system for an electrical system of a nuclear power plant.

[0014] A transient stability assessment system for an electrical system of a nuclear power plant, comprising: The nuclear power plant AC power system model building module is configured to: build a nuclear power plant AC power system model according to a single-line diagram of an electrical system of the nuclear power plant; The operating condition acquisition module is configured to: acquire the operating condition of the electrical system of the nuclear power plant, and set corresponding load conditions and system parameters according to the operating condition; A simulation module is configured to: simulate the operation conditions of the power plant using the AC power system model of the nuclear power plant, and record the electrical quantities in the power switching simulation process under each operation condition; The transient stability assessment module is configured to: perform transient stability assessment on the electrical system of the nuclear power plant based on the electrical quantity.

[0015] 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.

[0016] The fourth aspect of the present invention provides an electronic device, comprising a memory, a processor, and a program stored in the memory and executable on the processor, wherein when the processor executes the program, 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 are implemented.

[0017] One or more of the above technical solutions have the following beneficial effects: (1) The transient stability assessment method for the power switching process of the electrical system of a nuclear power plant proposed in the present invention includes three quantitative criteria, which can predict the power switching situation of the nuclear power plant through intuitive results and improve the reliability of system operation.

[0018] (2) The transient stability assessment method for the power switching process of the electrical system of a nuclear power plant proposed in the present invention comprehensively considers the impact of the system on the motor and the influence on the setting value of the circuit breaker during power switching, effectively improving the accuracy and practicality of the assessment results.

[0019] (3) In the transient stability assessment process of the power switching process of the nuclear power plant electrical system, the design and operation and maintenance personnel can use this method to judge the feasibility of system voltage switching in advance, and can timely adjust the nuclear power plant electrical system design plan or system operation plan to discover potential risks as early as possible, thereby minimizing losses. It has the flexibility of early perception and dynamic adjustment.

[0020] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0022] Figure 1 This is a flow chart of the method of the first embodiment.

[0023] Figure 2 This is the main AC power system architecture of the nuclear power plant A in the first embodiment.

[0024] Figure 3 It is a system structure diagram of the second embodiment. DETAILED DESCRIPTION

[0025] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0026] It should be noted that the terms used herein are for describing specific embodiments only and are not intended to be limiting of exemplary embodiments according to the present invention.

[0027] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0028] In view of the fact that the equipment is greatly impacted and the system fluctuates greatly during the power supply switching process of the existing nuclear power plant, the present invention proposes a method and system for evaluating whether the switching process meets the transient stability requirements, which can quantitatively judge the changes in the electrical quantities of the system after simulation, effectively improve the accuracy and practicality of the evaluation results, and realize the prediction of the power supply switching situation of the nuclear power plant. The following will be described in detail in conjunction with specific embodiments.

[0029] Embodiment 1 This embodiment discloses a transient stability assessment method for a nuclear power plant electrical system; like Figure 1 As shown, a transient stability assessment method for an electrical system of a nuclear power plant comprises: Step S1, constructing a nuclear power plant AC power system model according to the single-line diagram of the nuclear power plant electrical system.

[0030] In one or more embodiments, the simulation software takes ETAP software model building as an example (other software with model simulation calculation functions may also be used), and building a nuclear power plant AC power system model includes: Input the single-line diagram of the nuclear power plant electrical system into the ETAP software, use the ETAP software to simulate the connection relationship of each electrical equipment in the single-line diagram, complete the information of each electrical equipment, fill in the corresponding component number, name, power and other parameters; thereby constructing the nuclear power plant AC power system model.

[0031] Step S2, select representative nuclear power plant operating conditions as simulation conditions, such as design load operating conditions, light load operating conditions, heavy load operating conditions, etc.; take the design load operating conditions as an example, set the corresponding load loading conditions and system parameters according to the operating conditions, wherein for the load loading conditions, consider the characteristics of the current operating conditions, select the corresponding load to be put into operation, so as to achieve the effect of matching the actual operating conditions. The load loading conditions are: 500kV power grid supplies power to the plant operating load, the plant standby generator is offline, the prospect load is offline, the auxiliary boiler is out of operation, and the load center contact switch is turned on; the system parameters mainly include 500kV power grid parameters, 220kV power grid parameters, transformer parameters, transformer tap positions, etc., which are set according to the characteristics of the current nuclear power plant site.

[0032] Step S3, using the nuclear power plant AC power system model to simulate the power plant operating conditions, and record the electrical quantities in the power switching simulation process under each operating condition. The electrical quantities include: the maximum impact current of each medium voltage motor; the maximum impact current of the medium voltage bus incoming line circuit breaker; the phase angle value of the medium voltage motor at the switching moment; the terminal voltage value of the medium voltage motor at the switching moment; the slip rate of the medium voltage motor at the switching moment; and the grid parameters (grid voltage and phase angle difference) at the switching moment.

[0033] Step S4, performing transient stability assessment based on the electrical quantity, and calculating whether the assessment conditions under each working condition meet the requirements. The assessment conditions include: (1) When the incoming circuit breaker is closed, the ratio of the motor composite voltage to the frequency is not greater than 133%. The calculation method of the motor composite voltage is as follows: ; Where: Indicates the composite voltage of the motor; Indicates the equivalent voltage of the system; Indicates the equivalent voltage at the motor terminals; Indicates the phase angle difference between the system voltage and the motor voltage.

[0034] (2) The motor’s inrush current is not greater than the motor’s stall current; (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 largest motor + starting current value of the largest motor).

[0035] In addition, in this embodiment, if any operating condition does not meet the transient stability assessment conditions, it is necessary to adjust the system architecture or parameters and repeat the process from step S1 to step S4 until all operating conditions meet the transient stability assessment conditions. Then, it can be considered that the system meets the transient stability requirements during the voltage switching process.

[0036] In order to verify the effect of the method provided in this embodiment, a domestic nuclear power plant A is taken as an example, the primary voltage of the plant transformer is 500kV, and the primary voltage of the standby transformer is 220kV. When the nuclear power plant is operating normally, the high-voltage plant transformer carries the working busbar, and the standby transformer is in standby state, and the working section and the standby section have clear division of labor; when the plant transformer, generator or main step-up transformer high-voltage side fails, the circuit breaker on the low-voltage side of the high-voltage plant transformer should be cut off, and the circuit breaker on the low-voltage side of the standby transformer should be closed, that is, the working section is put into the standby transformer side, and the system architecture is as follows: Figure 2 shown.

[0037] In each working condition, the circuit breaker status changes when the system switches from the main transformer to the standby transformer are set to simulate the system voltage switching. Taking one of the working conditions as an example, assuming that the system power supply is switched due to a plant transformer failure, the changes in the circuit breakers in the system are mainly as follows: At 0s, a three-phase fault occurs on the secondary busbar UAT-2A-X of the plant transformer ZAS-ET-2A. At 98.3ms, the medium-voltage circuit breakers of the 10.5kV medium-voltage busbars ES-1 to ES-6 are opened, and the three-phase fault is cleared at the same time. The power supply is quickly switched from the 500kV system to the 220kV system. After 5ms, the circuit breakers of each medium-voltage busbar connected to the RAT transformer are closed, and the quick switching is completed (the setting of the switching time is determined according to the specific conditions of each nuclear power plant and is only for reference); Record the following electrical quantities during the power switching simulation of each operating condition, and calculate whether the following three evaluation conditions meet the requirements under each operating condition. According to the actual situation of nuclear power plant A in the case and the dimension of the data read after simulation, the above formula is processed, and the calculation formula after processing is as follows: ; Nuclear Power Plant A uses the above formula to verify the simulation results of the medium voltage motor, and extracts the verification results of some motors. The verification results are as follows: Table 1 Nuclear power plant part A medium voltage motor composite voltage calibration table

[0038] (2) The motor impact current is not greater than the motor's locked-rotor current. Taking domestic nuclear power plant A as an example, the specific judgment conditions are as follows: Table 2 Inrush current limits for medium voltage motors

[0039] (3) 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 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: Table 3 Inrush current limit of medium voltage busbar incoming circuit breaker

[0040] Embodiment 2 This embodiment discloses a transient stability assessment system for a nuclear power plant electrical system; like Figure 3 As shown, a transient stability assessment system for an electrical system of a nuclear power plant comprises: The nuclear power plant AC power system model building module is configured to: build a nuclear power plant AC power system model according to a single-line diagram of an electrical system of the nuclear power plant; The operating condition acquisition module is configured to: acquire the operating condition of the electrical system of the nuclear power plant, and set corresponding load conditions and system parameters according to the operating condition; A simulation module is configured to: simulate the operation conditions of the power plant using the AC power system model of the nuclear power plant, and record the electrical quantities in the power switching simulation process under each operation condition; The transient stability assessment module is configured to: perform transient stability assessment on the electrical system of the nuclear power plant based on the electrical quantity.

[0041] Embodiment 3 The purpose of this embodiment is to provide a computer-readable storage medium.

[0042] A computer-readable storage medium stores a computer program, 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 Example 1 of the present disclosure.

[0043] Embodiment 4 The purpose of this embodiment is to provide an electronic device.

[0044] An electronic device comprises a memory, a processor and a program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps in a transient stability assessment method for an electrical system of a nuclear power plant as described in Embodiment 1 of the present disclosure are implemented.

[0045] The steps involved in the apparatuses of the above embodiments 2, 3 and 4 correspond to the method embodiment 1, and the specific implementation methods can refer to the relevant description part 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 to include any medium that can store, encode or carry an instruction set for execution by a processor and enable the processor to execute any method in the present invention.

[0046] Those skilled in the art should understand that the modules or steps of the present invention described above can be implemented by a general-purpose computer device, or alternatively, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. The present invention is not limited to any specific combination of hardware and software.

[0047] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it 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 on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A transient stability assessment method for an electrical system of a nuclear power plant, characterized in that: include: According to the single-line diagram of the nuclear power plant electrical system, the AC power system model of the nuclear power plant is constructed; Obtaining the operating conditions of the electrical system of the nuclear power plant, and setting corresponding load conditions and system parameters according to the operating conditions; Using the nuclear power plant AC power system model to simulate the power plant operating conditions, and recording the electrical quantities in the power switching simulation process under each operating condition; A transient stability assessment of the electrical system of the nuclear power plant is performed based on the electrical quantities.

2. A transient stability assessment method for an electrical system of a nuclear power plant according to claim 1, characterized in that: The process of constructing the nuclear power plant AC power system model according to the single-line diagram of the nuclear power plant electrical system is as follows: Input the single-line diagram of the nuclear power plant electrical system into the simulation software, use the simulation software to simulate the connection relationship of each electrical equipment in the single-line diagram, complete the information of each electrical equipment, fill in the number, name, and power parameters of the corresponding components; in this way, construct the nuclear power plant AC power supply system model.

3. A transient stability assessment method for an electrical system of a nuclear power plant according to claim 1, characterized in that: The operating conditions of the nuclear power plant electrical system include load operating conditions, light load operating conditions and heavy load operating conditions.

4. A transient stability assessment method for an electrical system of a nuclear power plant according to claim 1, characterized in that: The corresponding load carrying conditions and system parameters are set according to the operating conditions: 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 power grid parameters, in-plant generator parameters, transformer parameters, and transformer tap positions.

5. A transient stability assessment method for an electrical system of a nuclear power plant according to claim 1, characterized in that: Set the circuit breaker state change when the system switches from the main transformer to the backup transformer to simulate the system voltage switching.

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

7. A transient stability assessment method for an electrical system of a nuclear power plant according to claim 1, characterized in that: The process of performing transient stability assessment on the electrical system of the nuclear power plant based on the electrical quantity is as follows: (1) Determine whether the ratio of the motor composite voltage to frequency 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's stall current; (3) Whether the inrush current of the medium voltage busbar incoming circuit breaker is not greater than 1.2×, where 1.2× is the difference between the total calculated current and the calculated current value of the largest motor plus the starting current value of the largest motor; When the electrical system of a nuclear power plant meets all the above three conditions, the electrical system of the nuclear power plant is in a transient stable state. When any one of the conditions is not met, the load carrying condition and system parameters are adjusted, and the simulation and electrical quantity calculation are performed again until all transient stability assessment conditions are met.

8. A transient stability assessment system for an electrical system of a nuclear power plant, 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 according to a single-line diagram of an electrical system of the nuclear power plant; The operating condition acquisition module is configured to: acquire the operating condition of the electrical system of the nuclear power plant, and set corresponding load conditions and system parameters according to the operating condition; A simulation module is configured to: simulate the operation conditions of the power plant using the AC power system model of the nuclear power plant, and record the electrical quantities in the power switching simulation process under each operation condition; The transient stability assessment module is configured to: perform transient stability assessment on the electrical system of the nuclear power plant based on the electrical quantity.

9. A computer-readable storage medium having a program stored thereon, characterized in that: When the program is executed by a processor, the steps of a transient stability assessment method for an electrical system of a nuclear power plant as described in any one of claims 1 to 7 are implemented.

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, the steps of the transient stability assessment method for the electrical system of a nuclear power plant are implemented as described in any one of claims 1 to 7.

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