Method and device for identifying shaft system torsional vibration of variable-rate operation of seawater circulation pump in nuclear power plant

Abstract

Embodiments of the present disclosure relate to a method and device for identifying shaft system torsional vibration of a variable-rate operation of a seawater circulation pump in a nuclear power plant. The method comprises: generating a first speed-time waveform signal about a rotation speed of a shaft of a motor in a seawater circulation pump system on the basis of first detection data about rotation of the shaft of the motor in the seawater circulation pump system of the nuclear power plant measured by a first speed detection unit; generating a second speed-time waveform signal about a rotation speed of a load pump end on the basis of second detection data about rotation of the load pump end of the seawater circulation pump system measured by a second speed detection unit; determining a frequency difference between a first frequency corresponding to the first speed-time waveform signal and a second frequency corresponding to the second speed-time waveform signal; and in response to determining that the frequency difference pertains to a predetermined frequency range, determining that the shaft system torsional vibration occurs in the seawater circulation pump system. According to the solution of the embodiments of the present disclosure, the identification accuracy of the shaft system torsional vibration of the seawater circulation pump system can be remarkably improved.

Description

Method and equipment for identifying shaft torsional vibration of seawater circulation pumps in variable-rate operation in nuclear power plants Technical Field Embodiments of the present disclosure generally relate to a nuclear power plant seawater circulation pump system, and more specifically to a method and device for identifying shaft torsional vibration of a nuclear power plant seawater circulation pump operating at variable magnification. Background Art The seawater circulation pump system used in nuclear power plants usually uses a vertical pump as a circulating water pump. The vertical pump is driven by an electric motor. The seawater circulation pump system is prone to shaft torsional vibration during operation. Once shaft torsional vibration occurs, the seawater circulation pump system will have safety hazards. Therefore, it is of great significance to monitor the shaft torsional vibration of the seawater circulation pump system. In order to monitor whether the seawater circulation pump system has shaft torsional vibration, it is usually analyzed and evaluated based on the voltage, current and other signals collected by the frequency converter to determine whether the seawater circulation pump system has shaft torsional vibration. However, the traditional monitoring method for whether the seawater circulation pump system has shaft torsional vibration has the problem of low detection accuracy. Summary of the invention In view of the above problems, the present disclosure provides a method and device for identifying shaft torsional vibration of a seawater circulating pump in variable magnification operation in a nuclear power plant, which can significantly improve the identification accuracy of shaft torsional vibration of the seawater circulating pump system. According to a first aspect of the present disclosure, a method for identifying shaft torsional vibration of a seawater circulating pump in a nuclear power plant with variable magnification operation is provided, the method comprising: generating a first speed-time waveform signal about the rotation speed of the shaft of the motor of the seawater circulating pump system based on first detection data about the rotation of the shaft of the motor of the seawater circulating pump system of the nuclear power plant detected by a first speed detection unit, the first speed detection unit being arranged on a side of the shaft of the motor of the seawater circulating pump system of the nuclear power plant close to the non-driving end; generating a second speed-time waveform signal about the rotation speed of the load pump end based on second detection data about the rotation of the load pump end of the seawater circulating pump system detected by a second speed detection unit; determining a frequency difference between a first frequency corresponding to the first speed-time waveform signal and a second frequency corresponding to the second speed-time waveform signal; and determining that shaft torsional vibration occurs in the seawater circulating pump system in response to determining that the frequency difference belongs to a predetermined frequency range. In some embodiments, the method further comprises: generating a PID control signal according to the frequency difference, wherein the PID control signal is used to adjust a given signal input of a frequency converter of the seawater circulation pump system so as to suppress shaft system torsional vibration. In some embodiments, determining the frequency difference between a first frequency corresponding to a first speed time waveform signal and a second frequency corresponding to a second speed time waveform signal includes: performing a fast Fourier transform on the first speed time waveform signal to determine the first frequency; performing a fast Fourier transform on the second speed time waveform signal to determine the second frequency; and determining the frequency difference between the first frequency and the second frequency. In some embodiments, the first speed detection unit includes a first code disc; the second speed detection unit includes a second code disc disposed at a load pump end of the seawater circulation pump system. In some embodiments, the axis of the first code disk coincides with the axis of the shaft of the motor of the nuclear power plant seawater circulation pump system. In some embodiments, the axis of the second code disk coincides with the axis of the shaft of the motor of the nuclear power plant seawater circulation pump system. In some embodiments, the control unit is disposed in a frequency converter of the seawater circulation pump system, and the first code disc and the second code disc include at least one of the following: an incremental code disc, an absolute code disc, and a resolution code disc. In some embodiments, the first code wheel and the second code wheel include at least one of the following: an electromagnetic code wheel and a photoelectric code wheel. In some embodiments, performing a fast Fourier transform on the first speed time waveform signal to determine the first frequency includes: performing a fast Fourier transform on the first speed time waveform signal to determine multiple frequency components corresponding to the first speed time waveform signal, and determining the frequency component with the largest corresponding amplitude among the multiple frequency components as the first frequency. In some embodiments, the control unit is further configured to generate a PID control signal for adjusting a given signal input of a frequency converter of the seawater circulation pump system according to a frequency difference between the first frequency and the second frequency and in accordance with a dual-inertia model. According to the second aspect of the present disclosure, a shaft torsional vibration identification device for a nuclear power plant seawater circulation pump with variable magnification operation is provided. The device comprises: a first speed detection unit, configured to detect first detection data about the rotation of the shaft of the motor of the nuclear power plant seawater circulation pump system, so as to generate a first speed time waveform signal about the rotation speed of the shaft of the motor of the seawater circulation pump system, the first speed detection unit being arranged on the side of the shaft of the motor of the nuclear power plant seawater circulation pump system close to the non-driving end; a second speed detection unit, configured to detect second detection data about the rotation of the load pump end of the seawater circulation pump system, so as to generate a second speed time waveform signal about the rotation speed of the load pump end; a control unit, respectively connected to the first speed detection unit and the second speed detection unit in communication, configured to determine the frequency difference between the first frequency corresponding to the first speed time waveform signal and the second frequency corresponding to the second speed time waveform signal, and in response to determining that the frequency difference belongs to a predetermined frequency range, determining that the shaft torsional vibration of the seawater circulation pump system occurs. In some embodiments, the control unit is further configured to generate a PID control signal according to the frequency difference, and the PID control signal is used to adjust a given signal input of a frequency converter of the seawater circulation pump system so as to suppress shaft system torsional vibration. In some embodiments, the first speed detection unit includes a first code disc; the second speed detection unit includes a second code disc disposed at a load pump end of the seawater circulation pump system. According to a third aspect of the present disclosure, a seawater circulation pump system for a nuclear power plant is provided. The system comprises: a motor for driving a load pump end; a load pump end; a frequency converter for driving the motor; and the device according to the first aspect of the present disclosure. It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS The above and other features, advantages and aspects of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. In the accompanying drawings, the same or similar reference numerals represent the same or similar elements. Figure 1 shows the dual-inertia model corresponding to the seawater circulation pump system. FIG2 shows a block diagram of a shaft torsional vibration identification device for a nuclear power plant seawater circulation pump in variable magnification operation according to an embodiment of the present disclosure. FIG3 shows a block diagram of a seawater circulation pump system of a nuclear power plant according to an embodiment of the present disclosure. FIG4 shows a flow chart of a method for identifying shaft torsional vibration of a nuclear power plant seawater circulation pump in variable-power operation according to an embodiment of the present disclosure. FIG. 5 shows a schematic block diagram of an example computing device that can be used to implement the method of an embodiment of the present disclosure. FIG6 shows a partial structural schematic diagram of a shaft torsional vibration identification device for a nuclear power plant seawater circulation pump in variable magnification operation according to an embodiment of the present disclosure. DETAILED DESCRIPTION The following is a description of exemplary embodiments of the present disclosure in conjunction with the accompanying drawings, including various details of the embodiments of the present disclosure to facilitate understanding, which should be considered as merely exemplary. Therefore, it should be recognized by those of ordinary skill in the art that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the present disclosure. Similarly, for the sake of clarity and conciseness, descriptions of well-known functions and structures are omitted in the following description. As used herein, the term "including" and its variations mean open inclusion, i.e., "including but not limited to". Unless otherwise stated, the term "or" means "and / or". The term "based on" means "based at least in part on". The terms "an example embodiment" and "an embodiment" mean "at least one example embodiment". The term "another embodiment" means "at least one additional embodiment". The terms "first", "second", etc. may refer to different or the same objects. Other explicit and implicit definitions may also be included below. As described above, the conventional method for monitoring whether the seawater circulation pump system has shaft torsional vibration has the problem of low detection accuracy. The motor drive end of the seawater circulation pump system is connected to the impeller of the pump (such as the circulating water pump) through a flexible coupling gearbox and a pump shaft. When the frequency converter drives the motor, there may be mechanical resonance caused by the flexible connection and dynamic interference caused by load changes. The existence of this phenomenon not only causes damage to the circulating pump itself, but also seriously affects the safety and reliability of the operation of the nuclear power plant. Therefore, discovering torsional vibration and actively suppressing it has great practical significance and impact. FIG1 shows a dual-inertia model corresponding to a seawater circulation pump system 100. The seawater circulation pump system 100 is composed of a driving motor M, a transmission mechanism S, a load pump end L, etc. The load pump end L is, for example, a circulating water pump. The transmission mechanism S can be, for example, composed of a coupling, a long shaft, etc. The working principle of the seawater circulation pump system 100 is that the driving motor M transmits power or torque to the load pump end L through the transmission mechanism S to realize system operation. Jm represents the inertia of the driving motor M, Jl represents the inertia of the load pump end L, Tm represents the electromagnetic torque of the driving motor M, Tl represents the torque of the load pump end L, represents the rotation angle of the driving motor M, represents the rotation angle of the load pump end L, Ts represents the torque of the long shaft in the transmission mechanism S, Ks represents the stiffness of the long shaft in the transmission mechanism S, and Δθ represents the rotation angle difference between the driving motor M and the load pump end L. Because Ts and Ks represent the long shaft torque and its stiffness respectively, under certain working conditions, they will be out of sync and produce a Δθ rotation angle difference. When this rotation angle difference is serious, it will cause the load pump end L to send torsional vibration during operation. In order to monitor whether the seawater circulation pump system has shaft torsional vibration, it is usually analyzed and evaluated based on the voltage, current and other signals collected by the frequency converter to determine whether the seawater circulation pump system has shaft torsional vibration. However, the traditional monitoring method for whether the seawater circulation pump system has shaft torsional vibration has the problem of low detection accuracy. In order to at least partially solve one or more of the above problems and other potential problems, an exemplary embodiment of the present disclosure proposes a shaft torsional vibration identification scheme for a nuclear power plant seawater circulation pump with variable magnification operation. In the scheme of the present disclosure, based on the first detection data of the rotation of the shaft of the motor of the nuclear power plant seawater circulation pump system detected by the first speed detection unit, a first speed time waveform signal about the rotation speed of the shaft of the motor of the seawater circulation pump system is generated, and the first speed detection unit is arranged on the side of the shaft of the motor of the nuclear power plant seawater circulation pump system close to the non-driving end; based on the second detection data of the rotation of the load pump end of the seawater circulation pump system detected by the second speed detection unit, a second speed time waveform signal about the rotation speed of the load pump end is generated; the frequency difference between the first frequency corresponding to the first speed time waveform signal and the second frequency corresponding to the second speed time waveform signal is determined; and in response to determining that the frequency difference belongs to a predetermined frequency range, it is determined that the seawater circulation pump system has a shaft torsional vibration. The scheme of the embodiment of the present disclosure can significantly improve the identification accuracy of the shaft torsional vibration of the seawater circulation pump system. The method of the embodiment of the present disclosure is described in detail below. FIG2 shows a block diagram of a shaft torsional vibration identification device 200 for a nuclear power plant seawater circulation pump with variable magnification operation according to an embodiment of the present disclosure. FIG6 shows a partial structural diagram of a shaft torsional vibration identification device for a nuclear power plant seawater circulation pump with variable magnification operation according to an embodiment of the present disclosure. The seawater circulation pump system 230 includes, for example, a motor 232, a frequency converter 234, and a load pump end 236. The motor 232 is used to drive the load pump end 236, and the frequency converter 234 is used to drive the motor 232. The load pump end 236 is, for example, a circulating water pump. The device 200 includes a first speed detection unit 202, a second speed detection unit 204, and a control unit 206. The motor 232 includes a non-driving end 241, a non-driving end guide bearing 242, a left cooling water bag 243, a right cooling water bag 244, a rotor 245, a stator 246, a shaft 247, a driving end guide bearing 248, a driving end 249, and a shaft extension end 250. It should be understood that the non-drive end 241 of the motor 232 is also referred to as the “free end”, the rotor 245 includes the rotor winding, and the stator 246 includes the stator winding. Regarding the first speed detection unit 202, it is configured to detect the first detection data about the rotation of the shaft 247 of the motor 232 of the nuclear power plant seawater circulation pump system 230, so as to generate the first speed time waveform signal about the rotation speed of the shaft 247 of the motor 232 of the seawater circulation pump system 230, and the first speed detection unit 202 is arranged on the side of the shaft 247 of the motor 232 of the nuclear power plant seawater circulation pump system 230 close to the non-driving end 241. In some embodiments, the first speed detection unit 202 is, for example, a first encoding disk arranged on the side of the shaft 247 of the motor 232 of the seawater circulation pump system 230 close to the non-driving end 241. It should be understood that the encoding disk is a digital encoder that can be used to measure angular displacement. The first code disk is arranged on the side of the shaft 247 of the motor 232 of the seawater circulation pump system 230 close to the non-driving end 241 (for example, the end of the shaft 247 away from the driving end 249), and rotates with the shaft 247 of the motor 232 of the seawater circulation pump system 230. The first code disk can detect the first detection data about the rotation of the shaft 247 of the motor 232 of the nuclear power plant seawater circulation pump system 230, and the first speed time waveform signal about the rotation speed of the shaft 247 of the motor 232 of the seawater circulation pump system 230 can be generated according to the first detection data. It should be understood that the first speed time waveform signal is a signal of a time domain representation of the first detection data. It is worth noting that there is sufficient space on the side of the shaft 247 of the motor 232 close to the non-driving end 241, and it is convenient to set the first speed detection unit 202 (for example, the first code disk). In some embodiments, the axis of the first code disk coincides with the axis of the shaft 247 of the motor 232 of the nuclear power plant seawater circulation pump system 230 to improve detection accuracy. Regarding the second speed detection unit 204, it is configured to detect the second detection data about the rotation of the load pump end 236 of the seawater circulation pump system 230, so as to generate a second speed time waveform signal about the rotation speed of the load pump end 236. In some embodiments, the second speed detection unit 204 is, for example, a second code disk disposed at the load pump end 236 of the seawater circulation pump system 230. The second code disk is disposed at the load pump end 236 of the seawater circulation pump system 230, and rotates with the load pump end 236 of the seawater circulation pump system 230. The second code disk can detect the second detection data about the rotation of the load pump end 236 of the seawater circulation pump system 230 of the nuclear power plant, and a second speed time waveform signal about the rotation speed of the load pump end 236 of the seawater circulation pump system 230 can be generated according to the second detection data. It should be understood that the second speed time waveform signal is a signal of a time domain representation of the second detection data. In some embodiments, the axis of the second code disk coincides with the axis of the shaft 247 of the motor 232 of the nuclear power plant seawater circulation pump system 230 to improve detection accuracy. Regarding the control unit 206, it is respectively connected to the first speed detection unit 202 and the second speed detection unit 204. The control unit 206 is configured to determine the frequency difference between the first frequency corresponding to the first speed time waveform signal and the second frequency corresponding to the second speed time waveform signal, and in response to determining that the frequency difference belongs to the predetermined frequency range, determine that the seawater circulation pump system 230 has a shaft system torsional vibration.

[0040] The control unit 206 may be implemented based on, for example, an MCU (Micro Controller Unit), a CPU (Central Processing Unit), an MPU (Micro Processing Unit), a GPU (Graphics Processing Units), an FPGA (Field Programmable Gate Array), a DSP (Digital Signal Processor), etc. The control unit 206 may also be implemented based on the computing device 500. In some embodiments, the control unit 206 is a main control board. The main control board is based on a single-board structure of a low-power high-speed processor (DSP+FPGA+ARM), with high system integration, high reliability, and low failure rate. The main control part only includes an integrated main control board. Compared with the traditional discrete functional board plug-in structure, it has fewer components, eliminating the shortcomings of oxidation, looseness, and poor contact of the board plug-in part after long-term operation, which eventually leads to the failure of the entire machine. It should be understood that the DSP chip is the control core, which performs real-time motor control algorithm calculations through analog sampling of voltage, current, and temperature. The analog sampling channel uses a high-performance differential op amp chip, and uses efficient filtering technology to filter out interference signals on the analog channel to achieve high-precision sampling data, which is the basis of high-performance control algorithms. DSP can also store relevant data in the system and perform fault diagnosis and analysis. Data is not lost when power is off, which can effectively ensure that the real operating status of the system can be restored through data analysis. It should be understood that the FPGA chip controls the optical fiber communication to ensure the normal communication between the control system and the power unit. The communication rate can reach 50M (megabytes), ensuring the data throughput and timely transmission. The system can more accurately control the output of the power unit, making the entire inverter system have strong real-time control. Digital input and digital output are also controlled by FPGA and isolated for external use; FPGA outputs high-precision 4-20mA (milliampere) analog quantity by controlling high-precision dedicated chips, and ensures the reliability of the signal through shielding technology. The 4-20mA analog quantity can be collected through FPGA through analog-to-digital conversion. In addition, FPGA also reads the data of the motor encoder. In order to adapt to the application of various types of on-site encoders, the three types of motor speed measuring encoders, namely incremental encoders, absolute encoders, and rotary encoders, can be measured, and high-precision motor speed and position information can be measured through optimized test methods. In some embodiments, the CPU uses an ARM (a processor) processor. It is worth noting that the ARM processor controls all external communication interfaces, which include RS-232 (a serial bus), RS-485 (a serial bus), CAN bus (a bus), PROFIBUS bus (a bus), and TCP / IP (a network protocol) network, which can meet the needs of various industrial applications. At the same time, other functional interfaces can be expanded through RS-232 and RS-485 interfaces. The multifunctional integrated main control system has the characteristics of dual-core CPU high-performance configuration, strong computing power, powerful functions, strong logic control, and rich interfaces, which can meet the needs of various complex systems and high-performance products for controllers. In some embodiments, in order to determine the first frequency, the control unit 206 is configured to perform a fast Fourier transform on the first speed time waveform signal to determine multiple frequency components corresponding to the first speed time waveform signal, and determine the frequency component with the largest corresponding amplitude among the multiple frequency components as the first frequency. It should be understood that the control unit 206 performs a fast Fourier transform on the first speed time waveform signal, and can convert the time domain signal into a frequency domain signal to determine the multiple frequency components corresponding to the first speed time waveform signal. The control unit 206 determines the frequency component with the largest amplitude among the multiple frequency components as the first frequency. It should be understood that the first frequency is related to the rotational speed of the shaft of the motor 232 of the seawater circulation pump system 230. Similarly, in order to determine the second frequency, the control unit 206 is configured to perform a fast Fourier transform on the second speed time waveform signal to determine the multiple frequency components corresponding to the second speed time waveform signal, and determine the frequency component with the largest corresponding amplitude among the multiple frequency components as the second frequency. It should be understood that the control unit 206 performs a fast Fourier transform on the second speed time waveform signal to convert the time domain signal into a frequency domain signal to determine the multiple frequency components corresponding to the second speed time waveform signal. The control unit 206 determines the frequency component with the largest amplitude among the multiple frequency components as the second frequency. It is understood that the second frequency is related to the rotation speed of the load pump end 236 of the seawater circulation pump system 230. After determining the first frequency and the second frequency, the control unit 206 determines a frequency difference between the first frequency and the second frequency. Then, the control unit 206 determines whether the frequency difference between the first frequency and the second frequency belongs to a predetermined frequency range. If it is determined that the frequency difference belongs to the predetermined frequency range, the control unit 206 determines that the seawater circulation pump system 230 has a shaft system torsional vibration. It should be understood that when the frequency difference between the first frequency and the second frequency is within a predetermined frequency range, it indicates that the seawater circulation pump system 230 has a shaft system torsional vibration. The predetermined frequency range can be determined according to the properties of the seawater circulation pump system 230, and can also be determined according to the measured value of the seawater circulation pump system 230. In some embodiments, the control unit 206 is further configured to generate a PID (Proportional Integral Derivative) control signal according to the frequency difference between the first frequency and the second frequency, and the PID control signal is used to adjust the given signal input of the inverter 234 of the seawater circulation pump system 230 so as to suppress the torsional vibration of the shaft system. In some embodiments, the control unit 206 is disposed in the frequency converter 234 of the seawater circulation pump system 230, for example, the control unit 206 is integrated in the main control board of the frequency converter 234 of the seawater circulation pump system 230. The first code disk and the second code disk include at least one of the following: an electromagnetic code disk and a photoelectric code disk. In some embodiments, the first code disk and the second code disk include at least one of the following: an incremental code disk, an absolute code disk, and a resolver code disk. It should be understood that the three motor speed measuring code disks of the incremental code disk, the absolute code disk, and the resolver code disk can all be measured, and the motor speed and position information with high precision can be measured by the optimized test method. In some embodiments, the control unit 206 is configured to generate a PID control signal for adjusting a given signal input of a frequency converter of the seawater circulation pump system according to a frequency difference between the first frequency and the second frequency and in accordance with a dual-inertia model. In some embodiments, the control unit 206 is configured to generate a PID control signal for adjusting a given signal input of the frequency converter of the seawater circulation pump system according to the frequency difference between the first frequency and the second frequency, the current signal and the voltage signal of the seawater circulation pump system 230 collected by the frequency converter, and the dual inertia model. In the embodiments of the present disclosure, a speed detection unit (such as a code disk) is used to obtain detection data (such as a speed code disk signal), and information such as the speed of the motor is calculated through a motor model to improve the shaft system torsional vibration identification technology so as to predict the occurrence of torsional vibration. Moreover, once torsional vibration occurs, the fast dynamic response capability of the torque of the frequency converter is used to realize active suppression control of torsional vibration, and the given signal input of the frequency converter is timely compensated for torsional vibration suppression based on the PID algorithm to form a closed loop, reduce the amplitude of shaft system torsional vibration, expand the speed regulation range of the motor, and ensure the safe and reliable operation of the electric drive system (such as the seawater circulation pump system). In particular, in some embodiments of the present disclosure, torsional vibration suppression technology is integrated in the main control board of the frequency converter. The operating parameters of the motor and the circulating water pump are acquired in real time through sensors such as the encoder and enter the main control board of the frequency converter. The output control quantity is calculated according to the dual inertia type and the current operating parameters, and the output of the frequency converter is adjusted to effectively suppress adverse factors such as torsional vibration that may exist during transmission between the motor and the circulating pump, thereby improving the operating reliability of the seawater circulating pump. FIG3 shows a block diagram of a seawater circulation pump system 300 of a nuclear power plant according to an embodiment of the present disclosure. The seawater circulation pump system 300 of a nuclear power plant includes a motor 232, a frequency converter 234, a load pump end 236, and a device 200. The motor 232 is used to drive the load pump end 236, and the frequency converter 234 is used to drive the motor 232. The load pump end 236 is, for example, a circulating water pump. The device 200 includes a first speed detection unit 202, a second speed detection unit 204, and a control unit 206. The first speed detection unit 202 is configured to detect first detection data about the shaft rotation of the motor 232 of the nuclear power plant seawater circulation pump system 230 to generate a first speed time waveform signal about the shaft rotation speed of the motor 232 of the seawater circulation pump system 230 . The second speed detection unit 204 is configured to detect second detection data regarding the rotation of the load pump end 236 of the seawater circulation pump system 230 , so as to generate a second speed time waveform signal regarding the rotation speed of the load pump end 236 . The control unit 206 is respectively connected to the first speed detection unit 202 and the second speed detection unit 204. The control unit 206 is configured to determine a frequency difference between a first frequency corresponding to the first speed time waveform signal and a second frequency corresponding to the second speed time waveform signal, and in response to determining that the frequency difference belongs to a predetermined frequency range, determine that the seawater circulation pump system 230 has a shaft system torsional vibration. In some embodiments, the control unit 206 is further configured to generate a PID control signal according to the frequency difference between the first frequency and the second frequency, and the PID control signal is used to adjust a given signal input of the frequency converter 234 of the seawater circulation pump system 230 to suppress shaft system torsional vibration. FIG4 shows a flow chart of a method 400 for identifying shaft torsional vibration of a nuclear power plant seawater circulation pump with variable magnification operation according to an embodiment of the present disclosure. The method 400 may be implemented by the control unit 206 or by the computing device 500. It should be understood that the method 400 may also include additional steps not shown and / or may omit the steps shown, and the scope of the present disclosure is not limited in this respect. At step 402, based on first detection data about the rotation of the shaft of the motor of the nuclear power plant seawater circulation pump system detected by the first speed detection unit, a first speed time waveform signal about the rotation speed of the shaft of the motor of the nuclear power plant seawater circulation pump system is generated. The first speed detection unit is arranged on a side of the shaft of the motor of the nuclear power plant seawater circulation pump system close to the non-driving end. In some embodiments, the first speed detection unit 202 is, for example, a first encoding disk disposed on the shaft of the motor 232 of the seawater circulation pump system 230. It should be understood that the encoding disk is a digital encoder that can be used to measure angular displacement. The first encoding disk is disposed on the shaft of the motor 232 of the seawater circulation pump system 230, and rotates following the shaft of the motor 232 of the seawater circulation pump system 230. The first encoding disk can detect first detection data about the shaft rotation of the motor 232 of the nuclear power plant seawater circulation pump system 230, and a first speed time waveform signal about the rotation speed of the shaft of the motor 232 of the seawater circulation pump system 230 can be generated according to the first detection data. It should be understood that the first speed time waveform signal is a signal of a time domain representation of the first detection data. At step 404 , based on second detection data regarding the rotation of the load pump end of the seawater circulation pump system detected by the second speed detection unit, a second speed time waveform signal regarding the rotation speed of the load pump end is generated. In some embodiments, the second speed detection unit 204 is, for example, a second code disk disposed at the load pump end 236 of the seawater circulation pump system 230. The second code disk is disposed at the load pump end 236 of the seawater circulation pump system 230, and rotates following the load pump end 236 of the seawater circulation pump system 230. The second code disk can detect second detection data about the rotation of the load pump end 236 of the seawater circulation pump system 230 of the nuclear power plant, and a second speed time waveform signal about the rotation speed of the load pump end 236 of the seawater circulation pump system 230 can be generated according to the second detection data. It should be understood that the second speed time waveform signal is a signal of a time domain representation of the second detection data. At step 406 , a frequency difference between a first frequency corresponding to the first speed time waveform signal and a second frequency corresponding to the second speed time waveform signal is determined. In some embodiments, determining the frequency difference between a first frequency corresponding to a first speed time waveform signal and a second frequency corresponding to a second speed time waveform signal includes: performing a fast Fourier transform on the first speed time waveform signal to determine the first frequency; performing a fast Fourier transform on the second speed time waveform signal to determine the second frequency; and determining the frequency difference between the first frequency and the second frequency. For example, in order to determine the first frequency, the control unit 206 is configured to perform a fast Fourier transform on the first speed time waveform signal, so as to determine the multiple frequency components corresponding to the first speed time waveform signal, and determine the frequency component with the largest corresponding amplitude among the multiple frequency components as the first frequency. It should be understood that the control unit 206 performs a fast Fourier transform on the first speed time waveform signal, and can convert the time domain signal into a frequency domain signal, so as to determine the multiple frequency components corresponding to the first speed time waveform signal. The control unit 206 determines the frequency component with the largest amplitude among the multiple frequency components as the first frequency. It should be understood that the first frequency is related to the rotational speed of the shaft of the motor 232 of the seawater circulation pump system 230. Similarly, in order to determine the second frequency, the control unit 206 is configured to perform a fast Fourier transform on the second speed time waveform signal to determine the multiple frequency components corresponding to the second speed time waveform signal, and determine the frequency component with the largest corresponding amplitude among the multiple frequency components as the second frequency. It should be understood that the control unit 206 performs a fast Fourier transform on the second speed time waveform signal to convert the time domain signal into a frequency domain signal to determine the multiple frequency components corresponding to the second speed time waveform signal. The control unit 206 determines the frequency component with the largest amplitude among the multiple frequency components as the second frequency. It is understood that the second frequency is related to the rotation speed of the load pump end 236 of the seawater circulation pump system 230. After determining the first frequency and the second frequency, the control unit 206 determines a frequency difference between the first frequency and the second frequency. At step 408 , in response to determining that the frequency difference belongs to a predetermined frequency range, it is determined that shaft torsional vibration occurs in the seawater circulation pump system. Then, the control unit 206 determines whether the frequency difference between the first frequency and the second frequency belongs to a predetermined frequency range. If it is determined that the frequency difference belongs to the predetermined frequency range, the control unit 206 determines that the seawater circulation pump system 230 has a shaft system torsional vibration. It should be understood that when the frequency difference between the first frequency and the second frequency is within a predetermined frequency range, it indicates that the seawater circulation pump system 230 has a shaft system torsional vibration. The predetermined frequency range can be determined according to the properties of the seawater circulation pump system 230, and can also be determined according to the measured value of the seawater circulation pump system 230. In some embodiments, the method 400 further includes: at step 410, generating a PID control signal according to the frequency difference, the PID control signal being used to adjust a given signal input of a frequency converter of the seawater circulation pump system so as to suppress shaft system torsional vibration. In some embodiments, generating a PID control signal according to the frequency difference includes: generating a PID control signal for adjusting a given signal input of a frequency converter of the seawater circulation pump system according to a dual-inertia model based on the frequency difference between the first frequency and the second frequency. In some embodiments, generating a PID control signal according to the frequency difference includes: generating a PID control signal for adjusting a given signal input of the frequency converter of the seawater circulation pump system according to a dual inertia model based on the frequency difference between the first frequency and the second frequency, and the current signal and voltage signal of the seawater circulation pump system 230 collected by the frequency converter. In the embodiments of the present disclosure, a speed detection unit (such as a code disk) is used to obtain detection data (such as a speed code disk signal), and information such as the speed of the motor is calculated through a motor model to improve the shaft system torsional vibration identification technology so as to predict the occurrence of torsional vibration. Moreover, once torsional vibration occurs, the fast dynamic response capability of the torque of the frequency converter is used to realize active suppression control of torsional vibration, and the given signal input of the frequency converter is timely compensated for torsional vibration suppression based on the PID algorithm to form a closed loop, reduce the amplitude of shaft system torsional vibration, expand the speed regulation range of the motor, and ensure the safe and reliable operation of the electric drive system (such as the seawater circulation pump system). In particular, in some embodiments of the present disclosure, torsional vibration suppression technology is integrated in the main control board of the frequency converter. The operating parameters of the motor and the circulating water pump are acquired in real time through sensors such as the encoder and enter the main control board of the frequency converter. The output control quantity is calculated based on the dual inertia model and the current operating parameters, and the output of the frequency converter is adjusted to effectively suppress adverse factors such as torsional vibration that may exist during transmission between the motor and the circulating pump, thereby improving the operating reliability of the seawater circulating pump. FIG5 shows a schematic block diagram of an example computing device 500 that can be used to implement the method of an embodiment of the present disclosure. As shown in the figure, the computing device 500 includes a central processing unit (i.e., CPU 501), which can perform various appropriate actions and processes according to computer program instructions stored in a read-only memory (i.e., ROM 502) or loaded from a storage unit 508 to a random access memory (i.e., RAM 503). In RAM 503, various programs and data required for the operation of the computing device 500 can also be stored. CPU 501, ROM 502, and RAM 503 are connected to each other via a bus 504. An input / output interface (i.e., I / O interface 505) is also connected to the bus 504. A number of components in the computing device 500 are connected to the I / O interface 505, including: an input unit 506, such as a keyboard, a mouse, a microphone, etc.; an output unit 507, such as various types of displays, speakers, etc.; a storage unit 508, such as a disk, an optical disk, etc.; and a communication unit 509, such as a network card, a modem, a wireless communication transceiver, etc. The communication unit 509 allows the computing device 500 to exchange information / data with other devices through a computer network such as the Internet and / or various telecommunication networks. The various processes and processing described above, such as method 400, can be performed by CPU 501. For example, in some embodiments, method 400 can be implemented as a computer software program, which is tangibly contained in a machine-readable medium, such as storage unit 508. In some embodiments, part or all of the computer program can be loaded and / or installed on computing device 500 via ROM 502 and / or communication unit 509. When the computer program is loaded into RAM 503 and executed by CPU 501, one or more actions of method 400 described above can be performed.

[0080] The present disclosure relates to methods, computing devices, computer-readable storage media and / or computer program products. The computer program product may include computer-readable program instructions for performing various aspects of the present disclosure. A computer-readable storage medium may be a tangible device that can hold and store instructions used by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the above. More specific examples (a non-exhaustive list) of computer-readable storage media include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the above. The computer-readable storage medium used herein is not to be interpreted as a transient signal itself, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire. The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network may include copper transmission cables, optical fiber transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge computing devices. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in a computer-readable storage medium in each computing / processing device. The computer program instructions for performing the operations of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages, such as Smalltalk, C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. The computer-readable program instructions may be executed entirely on the user's computer, partially on the user's computer, as a separate software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., using an Internet service provider to connect through the Internet). In some embodiments, by using the state information of the computer-readable program instructions to personalize an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), the electronic circuit may execute the computer-readable program instructions, thereby implementing various aspects of the present disclosure. Various aspects of the present disclosure are described herein with reference to flowcharts and / or block diagrams of methods, devices (systems) and computer program products according to embodiments of the present disclosure. It should be understood that each box in the flowchart and / or block diagram and the combination of boxes in the flowchart and / or block diagram can be implemented by computer-readable program instructions. These computer-readable program instructions can be provided to a processing unit of a general-purpose computer, a special-purpose computer, or other programmable data processing device, thereby producing a machine, so that when these instructions are executed by the processing unit of the computer or other programmable data processing device, a device that implements the functions / actions specified in one or more boxes in the flowchart and / or block diagram is generated. These computer-readable program instructions can also be stored in a computer-readable storage medium, and these instructions cause the computer, programmable data processing device, and / or other equipment to work in a specific manner, so that the computer-readable medium storing the instructions includes a manufactured product, which includes instructions for implementing various aspects of the functions / actions specified in one or more boxes in the flowchart and / or block diagram. Computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device so that a series of operating steps are performed on the computer, other programmable data processing apparatus, or other device to produce a computer-implemented process, thereby causing the instructions executed on the computer, other programmable data processing apparatus, or other device to implement the functions / actions specified in one or more boxes in the flowchart and / or block diagram. The flow chart and block diagram in the accompanying drawings show the possible architecture, function and operation of the equipment, method and computer program product according to multiple embodiments of the present disclosure. In this regard, each square box in the flow chart or block diagram can represent a part of a module, program segment or instruction, and a part of the module, program segment or instruction includes one or more executable instructions for realizing the specified logical function. In some alternative implementations, the functions marked in the square box can also occur in a sequence different from that marked in the accompanying drawings. For example, two continuous square boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each square box in the block diagram and / or flow chart, and the combination of the square boxes in the block diagram and / or flow chart can be implemented with a dedicated hardware-based system that performs the specified function or action, or can be implemented with a combination of special hardware and computer instructions. The embodiments of the present disclosure have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein. The above are only optional embodiments of the present disclosure and are not intended to limit the present disclosure. For those skilled in the art, the present disclosure may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A method for identifying shaft torsional vibration of a nuclear power plant seawater circulation pump with variable magnification operation, characterized in that: The method includes: generating a first speed-time waveform signal about the rotation speed of the shaft of the motor of the seawater circulating pump system based on first detection data about the rotation of the shaft of the motor of the nuclear power plant seawater circulating pump system detected by a first speed detection unit, the first speed detection unit being arranged on the side of the shaft of the motor of the nuclear power plant seawater circulating pump system close to the non-driving end; generating a second speed-time waveform signal about the rotation speed of the load pump end based on second detection data about the rotation of the load pump end of the seawater circulating pump system detected by a second speed detection unit; determining a frequency difference between a first frequency corresponding to the first speed-time waveform signal and a second frequency corresponding to the second speed-time waveform signal; and determining that shaft system torsional vibration occurs in the seawater circulating pump system in response to determining that the frequency difference belongs to a predetermined frequency range.

2. The method according to claim 1, characterized in that Also includes: A PID control signal is generated according to the frequency difference, and the PID control signal is used to adjust a given signal input of a frequency converter of a seawater circulation pump system so as to suppress shaft system torsional vibration.

3. The method according to claim 1, characterized in that Determining the frequency difference between a first frequency corresponding to a first speed time waveform signal and a second frequency corresponding to a second speed time waveform signal includes: performing a fast Fourier transform on the first speed time waveform signal to determine the first frequency; performing a fast Fourier transform on the second speed time waveform signal to determine the second frequency; and determining the frequency difference between the first frequency and the second frequency.

4. The method according to claim 1, characterized in that The first speed detection unit includes a first code disc; the second speed detection unit includes a second code disc arranged at the load pump end of the seawater circulation pump system.

5. The method according to claim 4, characterized in that: The axis of the first code disk coincides with the axis of the shaft of the motor of the seawater circulation pump system of the nuclear power plant.

6. The method according to claim 1, characterized in that: Performing a fast Fourier transform on the first speed time waveform signal to determine the first frequency includes: performing a fast Fourier transform on the first speed time waveform signal to determine multiple frequency components corresponding to the first speed time waveform signal, and determining the frequency component with the largest corresponding amplitude among the multiple frequency components as the first frequency.

7. The method according to claim 2, characterized in that: Generating a PID control signal according to the frequency difference includes: generating a PID control signal for adjusting a given signal input of a frequency converter of a seawater circulation pump system according to a dual-inertia model according to the frequency difference between the first frequency and the second frequency.

8. A shaft torsional vibration identification device for a nuclear power plant seawater circulation pump with variable magnification operation, characterized in that: include: A first speed detection unit is configured to detect first detection data about the rotation of the shaft of the motor of the nuclear power plant seawater circulation pump system, so as to generate a first speed time waveform signal about the rotation speed of the shaft of the motor of the seawater circulation pump system, and the first speed detection unit is arranged on a side of the shaft of the motor of the nuclear power plant seawater circulation pump system close to the non-driving end; a second speed detection unit is configured to detect second detection data about the rotation of the load pump end of the seawater circulation pump system, so as to generate a second speed time waveform signal about the rotation speed of the load pump end; and a control unit, which is respectively communicatively connected to the first speed detection unit and the second speed detection unit, and is configured to determine a frequency difference between a first frequency corresponding to the first speed time waveform signal and a second frequency corresponding to the second speed time waveform signal, and determine that shaft torsional vibration occurs in the seawater circulation pump system in response to determining that the frequency difference belongs to a predetermined frequency range.

9. The device according to claim 8, characterized in that The control unit is further configured to generate a PID control signal according to the frequency difference, wherein the PID control signal is used to adjust a given signal input of a frequency converter of the seawater circulation pump system so as to suppress shaft system torsional vibration.

10. A seawater circulation pump system for a nuclear power plant, characterized in that: include: A motor, used to drive a load pump end; Load pump end; A frequency converter for driving a motor; and a device according to any one of claims 8 and 9.

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