Temperature on-line monitoring method and system for direct current support capacitor of flexible direct current converter valve

Abstract

The invention discloses a flexible DC converter valve DC support capacitor temperature on-line monitoring method and system. The method comprises the steps of obtaining operation data of a thermistor arranged on a target capacitor wiring terminal; processing the operation data to obtain external temperature data of the target capacitor; constructing a thermal network model of the target capacitor based on the structure data and the material data of the target capacitor; performing optimization processing on the thermal network model through internal temperature data of the target capacitor acquired by the thermocouple to obtain an equivalent thermal resistance and thermal capacitance network model; inputting the obtained real-time current data of the target capacitor into the equivalent thermal resistance and thermal capacitance network model for processing to obtain internal temperature rise data of the target capacitor; and fusing the external temperature data and the internal temperature rise data to realize real-time monitoring of the temperature of the target capacitor according to a fused result. According to the method provided by the invention, real-time monitoring and accurate evaluation of the temperature of the capacitor are realized.

Description

Technical Field

[0001] The present application relates to the field of power monitoring technology, and in particular to a method and system for online monitoring the temperature of a DC support capacitor of a flexible DC converter valve. Background Art

[0002] In the flexible direct current transmission system, as a key component of the flexible direct current transmission system, the DC support capacitor can quickly respond to the voltage changes in the power grid, provide the necessary voltage support, and ensure the safe and reliable operation of the power grid. As the temperature of the capacitor increases, its capacitance loss increases, and the internal temperature rise increases, which may cause the performance of the capacitor to deteriorate or even fail. Therefore, real-time monitoring of the capacitor temperature is of great significance.

[0003] In the prior art, the real-time temperature of the capacitor is obtained by placing a temperature-sensing patch on the surface of the capacitor. However, the accuracy of such measurement is difficult to guarantee, which greatly reduces the safety and stability of the flexible DC valve. Summary of the invention

[0004] The present application aims to provide a method and system for online monitoring of the temperature of a DC support capacitor of a flexible DC converter valve, so as to solve the technical problem of how to improve the accuracy of capacitor temperature measurement.

[0005] In order to solve the above technical problems, the embodiment of the present application provides a method for online monitoring temperature of a DC support capacitor of a flexible DC converter valve, comprising: Acquiring operating data of a thermistor disposed at a terminal of a target capacitor; Processing the operating data to obtain external temperature data of the target capacitor; constructing a thermal network model of the target capacitor based on the structural data and material data of the target capacitor; Optimizing the thermal network model by using the internal temperature data of the target capacitor obtained by the thermocouple to obtain an equivalent thermal resistance and thermal capacitance network model; Inputting the acquired real-time current data of the target capacitor into the equivalent thermal resistance and heat capacitance network model for processing to obtain internal temperature rise data of the target capacitor, wherein the processing process of the equivalent thermal resistance and heat capacitance network model is designed to eliminate the influence of capacitance loss on temperature; The external temperature data and the internal temperature rise data are fused, and the fused result is used to realize real-time monitoring of the temperature of the target capacitor.

[0006] As one preferred solution, the processing of the operating data to obtain the external temperature data of the target capacitor includes: Converting the operating data to obtain voltage data; Inputting the voltage data into a voltage amplifier for amplification processing, and inputting the amplified voltage data into a filter circuit for filtering processing; Sampling the filtered voltage data to obtain a discrete digital signal, and calculating a voltage division value of the thermistor according to the discrete digital signal, wherein the voltage division value is a ratio of a voltage drop in a series circuit where the thermistor is located to a total voltage of the series circuit; The real-time resistance value of the thermistor is calculated based on the voltage division value, and the voltage division value based on the resistance value of the thermistor and the temperature is the ratio of the voltage drop in the series circuit where the thermistor is located to the total voltage of the series circuit.

[0007] As one preferred solution, the step of constructing a thermal network model of the target capacitor based on the structural data and material data of the target capacitor includes: The material data is analyzed to obtain the heat transfer coefficient and thickness of each layer of material of the target capacitor, and the equivalent heat transfer coefficient of the target capacitor is calculated according to the heat transfer coefficient and the thickness. The equivalent heat transfer coefficient is expressed as: , , Among them, λ th_H and λ th_V are the equivalent heat transfer coefficients of the target capacitor in the horizontal and vertical directions, i represents the number of material layers, and λ i With δ i are the heat transfer coefficient and thickness of the i-th layer, respectively, and δ represents the thickness of the target capacitor; Simplifying the target capacitor into a double-layer thermal resistance and heat capacitance network according to the structural data, and calculating the equivalent thermal conductivity of the target capacitor according to the double-layer thermal resistance and heat capacitance network; A thermal network model of the target capacitor is constructed according to the equivalent heat transfer coefficient and the equivalent thermal conductivity.

[0008] As one preferred solution, the thermal network model is optimized by using the internal temperature data of the target capacitor obtained by the thermocouple to obtain an equivalent thermal resistance and thermal capacitance network model, including: A temperature change curve is constructed according to the internal temperature data, and the temperature change curve is fitted to obtain a temperature fitting function, which is expressed as: , Where T(t) represents the temperature at time t, T0 is the ambient temperature, A is the amplitude, and τ is the time constant; Extracting a time constant according to the temperature fitting function, and calculating thermal network parameters of the thermal network model according to the thermal network model and the time constant, wherein the thermal network parameters include thermal resistance and thermal capacitance; An equivalent thermal resistance and thermal capacitance network model of the target capacitor is established according to the thermal network parameters and the thermal network model.

[0009] As one preferred solution, the real-time current data of the target capacitor is input into the equivalent thermal resistance and thermal capacitance network model for processing to obtain the internal temperature rise data of the target capacitor, including: Acquiring real-time current data of the target capacitor; Calculating according to the real-time current data to obtain the capacitance loss of the target capacitor; Calculate the internal temperature rise data of the target capacitor according to the capacitance loss and the equivalent thermal resistance and thermal capacitance network model; Wherein, the capacitance loss is expressed as: , in, represents the capacitance loss, represents the equivalent series resistance, represents the target capacitor current, Indicates frequency.

[0010] Another embodiment of the present application provides an online monitoring system for the temperature of a DC support capacitor of a flexible DC converter valve, comprising: An acquisition module, used to obtain operating data of a thermistor disposed at a terminal of a target capacitor; A conversion module, used for processing the operation data to obtain external temperature data of the target capacitor; A construction module, configured to construct a thermal network model of the target capacitor based on the structural data and material data of the target capacitor; An optimization module, configured to optimize the thermal network model by using the internal temperature data of the target capacitor obtained by the thermocouple to obtain an equivalent thermal resistance and thermal capacitance network model; a calculation module, configured to input the acquired real-time current data of the target capacitor into the equivalent thermal resistance and heat capacitance network model for processing to obtain internal temperature rise data of the target capacitor, wherein the processing process of the equivalent thermal resistance and heat capacitance network model is designed to eliminate the influence of capacitance loss on temperature; The monitoring module is used to fuse the external temperature data and the internal temperature rise data, and use the fused result to realize real-time monitoring of the temperature of the target capacitor.

[0011] As one preferred solution, the conversion module is specifically used for: Converting the operating data to obtain voltage data; Inputting the voltage data into a voltage amplifier for amplification processing, and inputting the amplified voltage data into a filter circuit for filtering processing; Sampling the filtered voltage data to obtain a discrete digital signal, and calculating a voltage division value of the thermistor according to the discrete digital signal, wherein the voltage division value is a ratio of a voltage drop in a series circuit where the thermistor is located to a total voltage of the series circuit; The real-time resistance value of the thermistor is calculated based on the voltage division value, and the voltage division value based on the resistance value of the thermistor and the temperature is the ratio of the voltage drop in the series circuit where the thermistor is located to the total voltage of the series circuit.

[0012] As one preferred solution, the building block is specifically used for: The material data is analyzed to obtain the heat transfer coefficient and thickness of each layer of material of the target capacitor, and the equivalent heat transfer coefficient of the target capacitor is calculated according to the heat transfer coefficient and the thickness. The equivalent heat transfer coefficient is expressed as: , , Among them, λ th_H and λ th_V are the equivalent heat transfer coefficients of the target capacitor in the horizontal and vertical directions, i represents the number of material layers, and λ i With δ i are the heat transfer coefficient and thickness of the i-th layer, respectively, and δ represents the thickness of the target capacitor; Simplifying the target capacitor into a double-layer thermal resistance and heat capacitance network according to the structural data, and calculating the equivalent thermal conductivity of the target capacitor according to the double-layer thermal resistance and heat capacitance network; A thermal network model of the target capacitor is constructed according to the equivalent heat transfer coefficient and the equivalent thermal conductivity.

[0013] As one preferred solution, the optimization module is specifically used for: A temperature change curve is constructed according to the internal temperature data, and the temperature change curve is fitted to obtain a temperature fitting function, which is expressed as: , Where T(t) represents the temperature at time t, T0 is the ambient temperature, A is the amplitude, and τ is the time constant; Extracting a time constant according to the temperature fitting function, and calculating thermal network parameters of the thermal network model according to the thermal network model and the time constant, wherein the thermal network parameters include thermal resistance and thermal capacitance; An equivalent thermal resistance and thermal capacitance network model of the target capacitor is established according to the thermal network parameters and the thermal network model.

[0014] As one preferred solution, the computing module is specifically used for: Acquiring real-time current data of the target capacitor; Calculating according to the real-time current data to obtain the capacitance loss of the target capacitor; Calculate the internal temperature rise data of the target capacitor according to the capacitance loss and the equivalent thermal resistance and thermal capacitance network model; Wherein, the capacitance loss is expressed as: , in, represents the capacitance loss, represents the equivalent series resistance, represents the target capacitor current, Indicates frequency.

[0015] Another embodiment of the present application provides an online temperature monitoring device for a DC support capacitor of a flexible DC converter valve, comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor implements the online temperature monitoring method for the DC support capacitor of a flexible DC converter valve as described above when executing the computer program.

[0016] Yet another embodiment of the present application provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, wherein when the device where the computer-readable storage medium is located executes the computer program, the above-mentioned method for online monitoring of the temperature of the DC support capacitor of the flexible DC converter valve is implemented.

[0017] Compared with the prior art, the beneficial effects of the embodiments of the present application are at least one of the following: 1) This application sets a thermistor on the capacitor terminal and connects the acquisition circuit in series to obtain current data, and then uses a current transformer to convert the current data into voltage data. The voltage divider value of the thermistor can be calculated to obtain the external temperature data of the capacitor. This method reduces the impact of environmental factors on temperature measurement and improves the accuracy of external temperature monitoring. At the same time, by obtaining internal temperature data through thermocouples installed inside the capacitor and combining it with the thermal network model for calculation, the temperature distribution and changes inside the capacitor can be more accurately reflected.

[0018] 2) This application can obtain the external and internal temperature data of the capacitor in real time, providing an important basis for capacitor status monitoring and fault warning. By real-time monitoring of the capacitor temperature, temperature anomalies can be detected in time and corresponding measures can be taken to avoid capacitor failure due to excessive temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a flow chart of an online temperature monitoring method of a DC support capacitor of a flexible DC converter valve in one embodiment of the present application; Figure 2 is a simplified schematic diagram of a capacitor structure in one embodiment of the present application; Figure 3 It is a schematic diagram of an online temperature monitoring system for a DC support capacitor of a flexible DC converter valve in one embodiment of the present application; Figure 4 It is a schematic diagram of an online temperature monitoring device for a DC support capacitor of a flexible DC converter valve in one of the embodiments of the present application. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. The purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0021] In the description of this application, the terms "first", "second", "third", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", "third", etc. may explicitly or implicitly include one or more of the feature. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0022] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be a connection between the two elements. The terms "vertical", "horizontal", "left", "right", "upper", "lower" and similar expressions used in this article are only for illustrative purposes, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. The term "and / or" used in this article includes any and all combinations of one or more related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0023] In the description of this application, it should be noted that, unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by those skilled in the art. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood by specific circumstances.

[0024] This application provides an embodiment, for details, see Figure 1 , Figure 1 The figure shows a flow chart of an online monitoring method for the temperature of a DC support capacitor of a flexible DC converter valve in one embodiment of the present application, which includes steps S1-S6: S1: Acquire the operating data of the thermistor disposed at the target capacitor terminal; It should be noted that the thermistor is a special resistor whose resistance value changes with temperature. In this step, the thermistor is installed on the terminal of the target capacitor to sense the temperature change of the capacitor and its surrounding environment. The acquisition circuit is a circuit connected in series with the thermistor to measure the current passing through the thermistor, usually including a current source (used to provide a stable current) and a current measuring element (such as an ammeter or current sensor).

[0025] Specifically, when the temperature of the target capacitor changes, the resistance value of the thermistor will change accordingly, causing the current passing through it to change. The current measurement element in the acquisition circuit captures this change and converts it into readable current data.

[0026] S2: Processing the operating data to obtain external temperature data of the target capacitor; Preferably, in one embodiment of the present application, the operation data is processed to obtain the external temperature data of the target capacitor, including: Convert the operating data to obtain voltage data; Inputting the voltage data into a voltage amplifier for amplification processing, and inputting the amplified voltage data into a filter circuit for filtering processing; Sampling the filtered voltage data to obtain a discrete digital signal, and calculating a voltage division value of the thermistor according to the discrete digital signal, where the voltage division value is a ratio of a voltage drop of the thermistor in the circuit to a total voltage; The real-time resistance value of the thermistor is calculated based on the voltage division value, and the external temperature data of the target capacitor is calculated based on the corresponding relationship between the resistance value of the thermistor and the temperature.

[0027] Specifically, the operating data (current) of the target capacitor is converted into a voltage signal proportional to the primary current. This voltage signal can be read by a voltage measuring element (such as a voltmeter or a voltage sensor). In a series circuit, the thermistor and other parts of the acquisition circuit (such as the internal resistance of the current source) share the power supply voltage. By measuring the voltage on the secondary side of the current transformer and using Ohm's law, the voltage across the thermistor, i.e., the voltage divider value, can be calculated. There is a certain relationship between the resistance value of the thermistor and the temperature (usually a negative temperature coefficient, i.e., the higher the temperature, the smaller the resistance value). By consulting the thermistor's specification sheet or using a calibrated temperature-resistance relationship curve, the voltage divider value can be converted into the corresponding temperature value. This temperature value represents the external temperature of the target capacitor and its surrounding environment.

[0028] S3: constructing a thermal network model of the target capacitor based on the structural data and material data of the target capacitor; In this step, the structure and material properties of the target capacitor need to be analyzed. These structures and material properties include the internal structure of the capacitor (such as the winding method of the anode foil, cathode foil and PP film), material properties (such as the heat transfer coefficient and thickness of each layer), and operating conditions (such as power level and heat dissipation method). According to the analysis results, select a suitable thermal network model, including Cauer model and Foster model.

[0029] The Cauer model is suitable for high-frequency or complex thermal environments where the actual physical structure inside the capacitor needs to be considered. This model can more accurately reflect the heat conduction and heat capacity distribution inside the capacitor.

[0030] The Foster model is suitable for scenarios with high requirements for computational simplicity. It ignores the internal physical structure and simplifies it into an equivalent thermal resistance and thermal capacitance network. Although this model sacrifices some accuracy, it is simpler to calculate and is suitable for quick analysis and preliminary design.

[0031] Preferably, in one embodiment of the present application, a thermal network model of a target capacitor is constructed based on structural data and material data of the target capacitor, including: The material data is analyzed to obtain the heat transfer coefficient and thickness of each layer of the target capacitor material. The equivalent heat transfer coefficient of the target capacitor is calculated based on the heat transfer coefficient and thickness. The equivalent heat transfer coefficient is expressed as: , , Among them, λ th_H and λ th_V are the equivalent heat transfer coefficients of the target capacitor in the horizontal and vertical directions, i represents the number of material layers, and λ i With δ i are the heat transfer coefficient and thickness of the i-th layer, respectively, and δ represents the thickness of the target capacitor; Simplifying the target capacitor into a double-layer thermal resistance and heat capacitance network according to the structural data, and calculating the equivalent thermal conductivity of the target capacitor according to the double-layer thermal resistance and heat capacitance network; A thermal network model of the target capacitor is constructed based on the equivalent heat transfer coefficient and equivalent thermal conductivity.

[0032] The internal structure of the capacitor can be simplified to a multi-layer structure, in which the anode foil, cathode foil and PP film are wound together to form a multi-layer structure. The capacitor has different equivalent heat transfer coefficients in the horizontal and vertical directions. These coefficients can be calculated by the heat transfer coefficient and thickness of each layer. After further simplification, the capacitor can be regarded as a thermal resistance and heat capacitance network with only two layers. Figure 2 As shown, Figure 2 A simplified schematic diagram of a capacitor structure is provided in an embodiment of the present application, wherein: represents the internal resistance, Represents the external resistor. The equivalent thermal conductivity of this thermal resistance and heat capacitance network is λ th_in It can be calculated by the following formula, which takes into account the thermal conductivity k of the PP film paper and the thickness of the aluminum foil δ Al .

[0033] , , .

[0034] For flexible DC systems, due to the high power level and large capacitance, multiple capacitors are usually connected in parallel. When performing thermal analysis, it is necessary to establish thermal network models between capacitors, between capacitors and module terminals, and between capacitors and submodule housings.

[0035] S4: Optimizing the thermal network model through the internal temperature data of the target capacitor obtained by the thermocouple to obtain an equivalent thermal resistance and thermal capacitance network model; In this step, a thermocouple is installed inside the capacitor to monitor temperature changes. By running the test, the temperature change data of the capacitor under different working conditions is recorded, and the collected temperature data is cleaned to remove abnormal values ​​and noise to ensure the accuracy of the data.

[0036] The cooling curve is fitted using mathematical tools such as MATLAB. The fitting formula is usually an exponential decay function that describes the change of temperature over time. By adjusting the parameters of the function (such as amplitude A, time constant τ, etc.), the error between the fitting curve and the experimental data is minimized. Using the first-order thermal network model and the relationship between the time constant τ and the thermal resistance Rth and thermal capacitance Cth, the values ​​of the thermal resistance Rth and thermal capacitance Cth can be calculated.

[0037] Substitute the obtained thermal network parameters into the thermal network model for simulation. Compare the differences between the simulation results and the experimental data. If the difference is large, it means that the model may be inaccurate or need further optimization. At this time, the model parameters can be adjusted and optimized, such as refitting the experimental data or considering more thermal physical factors. Repeat the verification process until the model can accurately reflect the actual thermal behavior of the capacitor.

[0038] Preferably, in one embodiment of the present application, the thermal network model is optimized by using the internal temperature data of the target capacitor obtained by the thermocouple to obtain an equivalent thermal resistance and thermal capacitance network model, including: The temperature change curve is constructed according to the temperature data, and the temperature change curve is fitted to obtain the temperature fitting function, which is expressed as: , Where T(t) represents the temperature at time t, T0 is the ambient temperature, A is the amplitude, and τ is the time constant; Extracting the time constant according to the temperature fitting function, calculating the thermal network parameters of the thermal network model according to the thermal network model and the time constant, the thermal network parameters including thermal resistance and thermal capacitance; An equivalent thermal resistance and thermal capacitance network model of the target capacitor is established according to the thermal network parameters and the thermal network model.

[0039] S5: inputting the acquired real-time current data of the target capacitor into an equivalent thermal resistance and heat capacitance network model for processing to obtain internal temperature rise data of the target capacitor, wherein the processing process of the equivalent thermal resistance and heat capacitance network model is designed to eliminate the influence of capacitance loss on temperature; Since the impedance of film capacitors has obvious frequency characteristics, it is necessary to perform FFT operation on the current signal in the capacitor to obtain the current spectrum at each frequency point. Then, the power loss is calculated at each frequency point, and the loss at each frequency point is summed to obtain a more accurate internal loss of the capacitor.

[0040] The thermal network model is used to solve the internal temperature rise of the capacitor and realize online monitoring. By inputting the capacitor current data, the current spectrum is calculated using FFT to find the capacitor loss, and then the thermal network model is used to solve the internal temperature rise of the capacitor. This process can reflect the thermal state of the capacitor in real time, providing an important basis for the health management and maintenance of the capacitor.

[0041] Preferably, in one embodiment of the present application, the acquired real-time current data of the target capacitor is input into the equivalent thermal resistance and thermal capacitance network model for processing to obtain the internal temperature rise data of the target capacitor, including: Obtain real-time current data of the target capacitor; Perform fast Fourier transform operation on the real-time current data to obtain the capacitance loss of the target capacitor; Calculate the internal temperature rise data of the target capacitor based on the capacitance loss and the equivalent thermal resistance and thermal capacitance network; Among them, the capacitance loss is expressed as: , in, represents the capacitance loss, represents the equivalent series resistance, represents the target capacitor current, Indicates frequency.

[0042] S6: Fuse the external temperature data and the internal temperature rise data, and use the fused result to achieve real-time monitoring of the target capacitor temperature.

[0043] In this step, the external temperature data and the internal temperature rise data are fused and processed, including data calibration, denoising and filtering steps to ensure the accuracy and reliability of the data. Using the external temperature data and the internal temperature rise data, the actual temperature of the target capacitor is calculated through a preset algorithm (such as a heat conduction model, a heat balance equation, etc.). In addition, in order to improve the accuracy of the temperature calculation, the algorithm needs to be error corrected. This can be achieved by comparing with the actual temperature measurement value and adjusting the parameters in the algorithm to reduce the error.

[0044] A temperature threshold can be set, and when the capacitor temperature exceeds this threshold, the alarm system is triggered. The alarm system can notify relevant personnel through sound, light or email, so that they can take timely measures to prevent the capacitor from overheating or damage.

[0045] Another embodiment of the present application provides an online monitoring system for the temperature of a DC support capacitor of a flexible DC converter valve. For details, see Figure 3 , Figure 3 The figure shows a schematic diagram of an online temperature monitoring system for a DC support capacitor of a flexible DC converter valve in one embodiment of the present application, which includes: a collection module 11, a conversion module 12, a construction module 13, an optimization module 14, a calculation module 15, and a monitoring module 16, wherein: The acquisition module 11 is used to obtain the operation data of the thermistor provided at the target capacitor terminal; A conversion module 12, used for processing the operation data to obtain external temperature data of the target capacitor; A construction module 13 is used to construct a thermal network model of the target capacitor based on the structural data and material data of the target capacitor; The optimization module 14 is used to optimize the thermal network model by using the internal temperature data of the target capacitor obtained by the thermocouple to obtain an equivalent thermal resistance and thermal capacitance network model; A calculation module 15 is used to input the acquired real-time current data of the target capacitor into an equivalent thermal resistance and heat capacitance network model for processing to obtain internal temperature rise data of the target capacitor, wherein the processing process of the equivalent thermal resistance and heat capacitance network model is designed to eliminate the influence of capacitance loss on temperature; The monitoring module 16 is used to fuse the external temperature data and the internal temperature rise data, and use the fused result to realize real-time monitoring of the temperature of the target capacitor.

[0046] Preferably, in one embodiment of the present application, the conversion module is specifically used to: Convert the operating data to obtain voltage data; Inputting the voltage data into a voltage amplifier for amplification processing, and inputting the amplified voltage data into a filter circuit for filtering processing; Sampling the filtered voltage data to obtain a discrete digital signal, and calculating a voltage division value of the thermistor according to the discrete digital signal, where the voltage division value is a ratio of a voltage drop of the thermistor in the circuit to a total voltage; The real-time resistance value of the thermistor is calculated based on the voltage division value, and the external temperature data of the target capacitor is calculated based on the corresponding relationship between the resistance value of the thermistor and the temperature.

[0047] Preferably, in one embodiment of the present application, the building module is specifically used for: The material data is analyzed to obtain the heat transfer coefficient and thickness of each layer of the target capacitor material. The equivalent heat transfer coefficient of the target capacitor is calculated based on the heat transfer coefficient and thickness. The equivalent heat transfer coefficient is expressed as: , , Among them, λ th_H and λ th_V are the equivalent heat transfer coefficients of the target capacitor in the horizontal and vertical directions, i represents the number of material layers, and λ i With δ i are the heat transfer coefficient and thickness of the i-th layer, respectively, and δ represents the thickness of the target capacitor; Simplifying the target capacitor into a double-layer thermal resistance and heat capacitance network according to the structural data, and calculating the equivalent thermal conductivity of the target capacitor according to the double-layer thermal resistance and heat capacitance network; A thermal network model of the target capacitor is constructed based on the equivalent heat transfer coefficient and equivalent thermal conductivity.

[0048] Preferably, in one embodiment of the present application, the optimization module is specifically used to: The temperature change curve is constructed according to the temperature data, and the temperature change curve is fitted to obtain the temperature fitting function, which is expressed as: , Where T(t) represents the temperature at time t, T0 is the ambient temperature, A is the amplitude, and τ is the time constant; Extracting the time constant according to the temperature fitting function, calculating the thermal network parameters of the thermal network model according to the thermal network model and the time constant, the thermal network parameters including thermal resistance and thermal capacitance; An equivalent thermal resistance and thermal capacitance network model of the target capacitor is established according to the thermal network parameters and the thermal network model.

[0049] Preferably, in one embodiment of the present application, the computing module is specifically used for: Obtain real-time current data of the target capacitor; Perform fast Fourier transform operation on the real-time current data to obtain the capacitance loss of the target capacitor; Calculate the internal temperature rise data of the target capacitor based on the capacitance loss and the equivalent thermal resistance and thermal capacitance network; Among them, the capacitance loss is expressed as: , in, represents the capacitance loss, represents the equivalent series resistance, represents the target capacitor current, Indicates frequency.

[0050] Another embodiment of the present application provides an online monitoring device for the temperature of a DC support capacitor of a flexible DC converter valve. For details, see Figure 4, which is a structural block diagram of an online temperature monitoring device for a DC support capacitor of a flexible DC converter valve provided in an embodiment of the present application. The online temperature monitoring device for a DC support capacitor of a flexible DC converter valve provided in an embodiment of the present application comprises a processor 21, a memory 22, and a computer program stored in the memory 22 and configured to be executed by the processor 21. When the processor 21 executes the computer program, the steps in the above-mentioned embodiment of the online temperature monitoring method for the DC support capacitor of a flexible DC converter valve are implemented, for example Figure 1 or, when the processor 21 executes the computer program, the functions of the modules in the above-mentioned device embodiments, such as the acquisition module 11, are implemented.

[0051] Exemplarily, the computer program can be divided into one or more modules, and the one or more modules are stored in the memory 22 and executed by the processor 21 to complete the present application. The one or more modules can be a series of computer program instruction segments that can complete specific functions, and the instruction segments are used to describe the execution process of the computer program in the online monitoring device for the temperature of the DC support capacitor of the flexible DC converter valve. For example, the computer program can be divided into an acquisition module 11, a conversion module 12, a construction module 13, an optimization module 14, a calculation module 15, and a monitoring module 16.

[0052] The online monitoring device for the temperature of the DC support capacitor of the flexible DC converter valve may include, but is not limited to, a processor 21 and a memory 22. Those skilled in the art can understand that the schematic diagram is only an example of the online monitoring device for the temperature of the DC support capacitor of the flexible DC converter valve, and does not constitute a limitation on the online monitoring device for the temperature of the DC support capacitor of the flexible DC converter valve, and may include more or fewer components than shown in the figure, or combine certain components, or different components, for example, the online monitoring device for the temperature of the DC support capacitor of the flexible DC converter valve may also include input and output devices, network access devices, buses, etc.

[0053] The processor 21 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc. The processor 21 is the control center of the online temperature monitoring device for the DC support capacitor of the flexible DC converter valve, and uses various interfaces and lines to connect various parts of the online temperature monitoring device for the DC support capacitor of the flexible DC converter valve.

[0054] The memory 22 can be used to store the computer program and / or module. The processor 21 realizes various functions of the online monitoring device for the temperature of the DC support capacitor of the flexible DC converter valve by running or executing the computer program and / or module stored in the memory 22 and calling the data stored in the memory 22. The memory 22 can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, an application required for at least one function (such as a sound playback function, an image playback function, etc.); the data storage area can store data created according to the use of the mobile phone (such as audio data, a phone book, etc.). In addition, the memory 22 can include a high-speed random access memory, and can also include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0055] Wherein, if the module integrated in the online monitoring device for the temperature of the DC support capacitor of the flexible DC converter valve is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the present application implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Wherein, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form, etc. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electric carrier signal, telecommunication signal and software distribution medium, etc.

[0056] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium, and when the program is executed, it can include the processes of the embodiments of the above-mentioned methods. The storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0057] Accordingly, an embodiment of the present application provides a computer-readable storage medium, wherein the computer-readable storage medium includes a stored computer program, wherein when the computer program is running, the device where the computer-readable storage medium is located is controlled to perform the steps in the method for online monitoring the temperature of the DC support capacitor of the flexible DC converter valve in the above embodiment, for example Figure 1 Steps S1 to S6 described in .

[0058] Compared with the prior art, the embodiments of the present application have the following advantages: 1) This application sets a thermistor on the capacitor terminal and connects the acquisition circuit in series to obtain current data, and then uses a current transformer to convert the current data into voltage data. The voltage divider value of the thermistor can be calculated to obtain the external temperature data of the capacitor. This method reduces the impact of environmental factors on temperature measurement and improves the accuracy of external temperature monitoring. At the same time, by obtaining internal temperature data through thermocouples installed inside the capacitor and combining it with the thermal network model for calculation, the temperature distribution and changes inside the capacitor can be more accurately reflected.

[0059] 2) This application can obtain the external and internal temperature data of the capacitor in real time, providing an important basis for capacitor status monitoring and fault warning. By real-time monitoring of the capacitor temperature, temperature anomalies can be detected in time and corresponding measures can be taken to avoid capacitor failure due to excessive temperature.

[0060] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A method for online monitoring temperature of a DC support capacitor of a flexible DC converter valve, characterized in that: include: Acquiring operating data of a thermistor disposed at a terminal of a target capacitor; Processing the operating data to obtain external temperature data of the target capacitor; constructing a thermal network model of the target capacitor based on the structural data and material data of the target capacitor; Optimizing the thermal network model by using the internal temperature data of the target capacitor obtained by the thermocouple to obtain an equivalent thermal resistance and thermal capacitance network model; Inputting the acquired real-time current data of the target capacitor into the equivalent thermal resistance and heat capacitance network model for processing to obtain internal temperature rise data of the target capacitor, wherein the processing process of the equivalent thermal resistance and heat capacitance network model is designed to eliminate the influence of capacitance loss on temperature; The external temperature data and the internal temperature rise data are fused, and the fused result is used to realize real-time monitoring of the temperature of the target capacitor.

2. The method for online monitoring temperature of a DC support capacitor of a flexible DC converter valve according to claim 1, characterized in that: The processing of the operating data to obtain the external temperature data of the target capacitor includes: Converting the operating data to obtain voltage data; Inputting the voltage data into a voltage amplifier for amplification processing, and inputting the amplified voltage data into a filter circuit for filtering processing; Sampling the filtered voltage data to obtain a discrete digital signal, and calculating a voltage division value of the thermistor according to the discrete digital signal, wherein the voltage division value is a ratio of a voltage drop in a series circuit where the thermistor is located to a total voltage of the series circuit; The real-time resistance value of the thermistor is calculated based on the voltage division value, and the external temperature data of the target capacitor corresponding to the real-time resistance value is calculated based on the corresponding relationship between the resistance value of the thermistor and the temperature.

3. The method for online monitoring temperature of a DC support capacitor of a flexible DC converter valve according to claim 1, characterized in that: The step of constructing a thermal network model of the target capacitor based on the structural data and material data of the target capacitor includes: The material data is analyzed to obtain the heat transfer coefficient and thickness of each layer of material of the target capacitor, and the equivalent heat transfer coefficient of the target capacitor is calculated according to the heat transfer coefficient and the thickness. The equivalent heat transfer coefficient is expressed as: ， ， Among them, λ th_H and λ th_V are the equivalent heat transfer coefficients of the target capacitor in the horizontal and vertical directions, i represents the number of material layers, and λ i With δ i are the heat transfer coefficient and thickness of the i-th layer, respectively, and δ represents the thickness of the target capacitor; Simplifying the target capacitor into a double-layer thermal resistance and heat capacitance network according to the structural data, and calculating the equivalent thermal conductivity of the target capacitor according to the double-layer thermal resistance and heat capacitance network; A thermal network model of the target capacitor is constructed according to the equivalent heat transfer coefficient and the equivalent thermal conductivity.

4. The method for online monitoring temperature of a DC support capacitor of a flexible DC converter valve according to claim 1, characterized in that: The thermal network model is optimized by using the internal temperature data of the target capacitor obtained by the thermocouple to obtain an equivalent thermal resistance and thermal capacitance network model, including: A temperature change curve is constructed according to the internal temperature data, and the temperature change curve is fitted to obtain a temperature fitting function, which is expressed as: ， Where T(t) represents the temperature at time t, T0 is the ambient temperature, A is the amplitude, and τ is the time constant; Extracting a time constant according to the temperature fitting function, and calculating thermal network parameters of the thermal network model according to the thermal network model and the time constant, wherein the thermal network parameters include thermal resistance and thermal capacitance; An equivalent thermal resistance and thermal capacitance network model of the target capacitor is established according to the thermal network parameters and the thermal network model.

5. The method for online monitoring temperature of a DC support capacitor of a flexible DC converter valve according to claim 1, characterized in that: The step of inputting the acquired real-time current data of the target capacitor into the equivalent thermal resistance and thermal capacitance network model for processing to obtain the internal temperature rise data of the target capacitor includes: Acquiring real-time current data of the target capacitor; Calculating according to the real-time current data to obtain the capacitance loss of the target capacitor; Calculate the internal temperature rise data of the target capacitor according to the capacitance loss and the equivalent thermal resistance and thermal capacitance network model; Wherein, the capacitance loss is expressed as: ， in, represents the capacitance loss, represents the equivalent series resistance, represents the target capacitor current, Indicates frequency.

6. An online monitoring system for the temperature of a DC support capacitor of a flexible DC converter valve, characterized in that: include: An acquisition module, used to obtain operating data of a thermistor disposed at a terminal of a target capacitor; A conversion module, used for processing the operation data to obtain external temperature data of the target capacitor; A construction module, configured to construct a thermal network model of the target capacitor based on the structural data and material data of the target capacitor; An optimization module, configured to optimize the thermal network model by using the internal temperature data of the target capacitor obtained by the thermocouple to obtain an equivalent thermal resistance and thermal capacitance network model; a calculation module, configured to input the acquired real-time current data of the target capacitor into the equivalent thermal resistance and heat capacitance network model for processing to obtain internal temperature rise data of the target capacitor, wherein the processing process of the equivalent thermal resistance and heat capacitance network model is designed to eliminate the influence of capacitance loss on temperature; The monitoring module is used to fuse the external temperature data and the internal temperature rise data, and use the fused result to realize real-time monitoring of the temperature of the target capacitor.

7. The online temperature monitoring system for the DC support capacitor of the flexible DC converter valve according to claim 6, characterized in that: The conversion module is specifically used for: Converting the operating data to obtain voltage data; Inputting the voltage data into a voltage amplifier for amplification processing, and inputting the amplified voltage data into a filter circuit for filtering processing; Sampling the filtered voltage data to obtain a discrete digital signal, and calculating a voltage division value of the thermistor according to the discrete digital signal, wherein the voltage division value is a ratio of a voltage drop in a series circuit where the thermistor is located to a total voltage of the series circuit; The real-time resistance value of the thermistor is calculated based on the voltage division value, and the voltage division value based on the resistance value of the thermistor and the temperature is the ratio of the voltage drop in the series circuit where the thermistor is located to the total voltage of the series circuit.

8. The online temperature monitoring system for the DC support capacitor of the flexible DC converter valve according to claim 6, characterized in that: The building blocks are specifically used for: The material data is analyzed to obtain the heat transfer coefficient and thickness of each layer of material of the target capacitor, and the equivalent heat transfer coefficient of the target capacitor is calculated according to the heat transfer coefficient and the thickness. The equivalent heat transfer coefficient is expressed as: ， ， Among them, λ th_H and λ th_V are the equivalent heat transfer coefficients of the target capacitor in the horizontal and vertical directions, i represents the number of material layers, and λ i With δ i are the heat transfer coefficient and thickness of the i-th layer, respectively, and δ represents the thickness of the target capacitor; Simplifying the target capacitor into a double-layer thermal resistance and heat capacitance network according to the structural data, and calculating the equivalent thermal conductivity of the target capacitor according to the double-layer thermal resistance and heat capacitance network; A thermal network model of the target capacitor is constructed according to the equivalent heat transfer coefficient and the equivalent thermal conductivity.

9. The online temperature monitoring system for the DC support capacitor of the flexible DC converter valve according to claim 6, characterized in that: The optimization module is specifically used for: A temperature change curve is constructed according to the internal temperature data, and the temperature change curve is fitted to obtain a temperature fitting function, which is expressed as: ， Where T(t) represents the temperature at time t, T0 is the ambient temperature, A is the amplitude, and τ is the time constant; Extracting a time constant according to the temperature fitting function, and calculating thermal network parameters of the thermal network model according to the thermal network model and the time constant, wherein the thermal network parameters include thermal resistance and thermal capacitance; An equivalent thermal resistance and thermal capacitance network model of the target capacitor is established according to the thermal network parameters and the thermal network model.

10. The online temperature monitoring system for the DC support capacitor of the flexible DC converter valve according to claim 6, characterized in that: The computing module is specifically used for: Acquiring real-time current data of the target capacitor; Calculating according to the real-time current data to obtain the capacitance loss of the target capacitor; Calculate the internal temperature rise data of the target capacitor according to the capacitance loss and the equivalent thermal resistance and thermal capacitance network model; Wherein, the capacitance loss is expressed as: ， in, represents the capacitance loss, represents the equivalent series resistance, represents the target capacitor current, Indicates frequency.

11. An online monitoring device for the temperature of a DC support capacitor of a flexible DC converter valve, characterized in that: The method comprises a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein when the processor executes the computer program, the method for online monitoring the temperature of the DC support capacitor of the flexible DC converter valve as claimed in any one of claims 1 to 5 is implemented.

12. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, wherein when the device where the computer-readable storage medium is located executes the computer program, the online monitoring method for the temperature of the DC support capacitor of the flexible DC converter valve according to any one of claims 1 to 5 is implemented.

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