A method and system for on-line monitoring of temperature of DC support capacitor of a soft straight converter valve

Abstract

The application discloses a kind of flexible straight converter valve direct current support capacitor temperature on-line monitoring method and system, including obtaining the operating data of thermistor arranged in target capacitor terminal;The external temperature data of target capacitor is obtained by processing operating data;Based on the structure data and material data of target capacitor, the thermal network model of target capacitor is constructed;The internal temperature data of target capacitor is obtained by thermocouple, and the thermal network model is optimized and handled, and the equivalent thermal resistance heat capacity network model is obtained;Real-time current data of target capacitor is input into equivalent thermal resistance heat capacity network model and handled, and the internal temperature rise data of target capacitor is obtained;External temperature data and internal temperature rise data are fused, and the real-time monitoring of target capacitor temperature is realized with the result after fusion.The method provided in the application realizes the real-time monitoring and accurate evaluation of capacitor temperature.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power monitoring, in particular to a method and system for online monitoring of temperature of DC support capacitor of HVDC valve. BACKGROUND

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

[0003] In the prior art, the real-time temperature of the capacitor is obtained by placing a temperature-sensitive 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 HVDC valve. SUMMARY

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

[0005] To solve the above technical problem, the present application provides a method for online monitoring of temperature of DC support capacitor of HVDC valve, comprising:

[0006] obtaining operating data of a thermistor arranged at a target capacitor terminal;

[0007] processing the operating data to obtain external temperature data of the target capacitor;

[0008] constructing a thermal network model of the target capacitor based on structure data and material data of the target capacitor;

[0009] optimizing the thermal network model by internal temperature data of the target capacitor obtained by a thermocouple to obtain an equivalent thermal resistance and heat capacity network model;

[0010] inputting the obtained real-time current data of the target capacitor into the equivalent thermal resistance and heat capacity 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 capacity network model is designed to eliminate the influence of capacitor loss on temperature;

[0011] fusing the external temperature data and the internal temperature rise data to realize real-time monitoring of the temperature of the target capacitor based on the fused result.

[0012] As one of the preferred solutions, the processing of the operation data to obtain the external temperature data of the target capacitor comprises:

[0013] Converting the operation data to obtain voltage data;

[0014] Inputting the voltage data into a voltage amplifier for amplification processing, and inputting the voltage data after amplification processing into a filter circuit for filtering processing;

[0015] Sampling the voltage data after filtering processing to obtain discrete digital signals, and calculating a voltage division value of the thermistor according to the discrete digital signals, the voltage division value being a ratio of a voltage drop in a series circuit in which the thermistor is located to a total voltage of the series circuit;

[0016] Calculating a real-time resistance value of the thermistor based on the voltage division value, the voltage division value being a ratio of a voltage drop in a series circuit in which the thermistor is located to a total voltage of the series circuit between the resistance value of the thermistor and the temperature.

[0017] As one of the preferred solutions, the constructing of the thermal network model of the target capacitor based on the structure data and the material data of the target capacitor comprises:

[0018] Analyzing the material data to obtain a heat transfer coefficient and a thickness of each layer of material of the target capacitor, and calculating an equivalent heat transfer coefficient of the target capacitor according to the heat transfer coefficient and the thickness, the equivalent heat transfer coefficient being represented as:

[0019] ,

[0020] ,

[0021] wherein, λ th_H and λ th_V are the equivalent heat transfer coefficients of the target capacitor in the horizontal direction and the vertical direction respectively, i represents the number of layers of material, λ i and δ i are the heat transfer coefficient and the thickness of the i-th layer respectively, and δ represents the thickness of the target capacitor.

[0022] Simplifying the target capacitor into a double-layer thermal resistance and thermal capacity network according to the structure data, and calculating an equivalent thermal conductivity of the target capacitor according to the double-layer thermal resistance and thermal capacity network;

[0023] Constructing the thermal network model of the target capacitor according to the equivalent heat transfer coefficient and the equivalent thermal conductivity.

[0024] As one of the preferred solutions, the optimization of the thermal network model by the internal temperature data of the target capacitor obtained by the thermocouple comprises:

[0025] According to the internal temperature data, a temperature change curve is constructed, and a temperature fitting function is obtained by fitting the temperature change curve, and is expressed as:

[0026] ,

[0027] Wherein, T(t) represents the temperature at time t, T0 is the ambient temperature, A is the amplitude, and τ is the time constant;

[0028] According to the temperature fitting function, the time constant is extracted, and the thermal network parameters of the thermal network model are calculated according to the thermal network model and the time constant, wherein the thermal network parameters include thermal resistance and thermal capacity;

[0029] According to the thermal network parameters and the thermal network model, an equivalent thermal resistance and thermal capacity network model of the target capacitor is established.

[0030] As one of the preferred solutions, the real-time current data of the target capacitor is input into the equivalent thermal resistance and thermal capacity network model for processing to obtain the internal temperature rise data of the target capacitor, comprising:

[0031] Obtain the real-time current data of the target capacitor;

[0032] According to the real-time current data, the capacitance loss of the target capacitor is calculated;

[0033] According to the capacitance loss and the equivalent thermal resistance and thermal capacity network model, the internal temperature rise data of the target capacitor is calculated;

[0034] Wherein, the capacitance loss is expressed as:

[0035] ,

[0036] Wherein, represents the capacitance loss, represents the equivalent series resistance, represents the target capacitor current, represents the frequency.

[0037] Another embodiment of the application provides a flexible direct current (DC) converter valve DC support capacitor temperature online monitoring system, comprising:

[0038] The acquisition module is configured to obtain the operating data of the thermistor arranged at the target capacitor terminal;

[0039] a conversion module, configured to process the operation data to obtain external temperature data of the target capacitor;

[0040] a construction module, configured to construct a thermal network model of the target capacitor based on structure data and material data of the target capacitor;

[0041] an optimization module, configured to optimize the thermal network model by internal temperature data of the target capacitor obtained by a thermocouple to obtain an equivalent thermal resistance and heat capacity network model;

[0042] a calculation module, configured to input real-time current data of the target capacitor obtained to the equivalent thermal resistance and heat capacity 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 capacity network model is designed to eliminate the influence of capacitor loss on temperature;

[0043] a monitoring module, configured to fuse the external temperature data and the internal temperature rise data to realize real-time monitoring of the temperature of the target capacitor based on the fused result.

[0044] As one of the preferred solutions, the conversion module is specifically configured to:

[0045] convert the operation data to obtain voltage data;

[0046] input the voltage data into a voltage amplifier for amplification processing, and input the voltage data after amplification processing into a filter circuit for filtering processing;

[0047] sample the voltage data after filtering processing to obtain discrete digital signals, calculate a voltage division value of the thermistor according to the discrete digital signals, the voltage division value being a ratio of a voltage drop in a series circuit in which the thermistor is located to a total voltage of the series circuit;

[0048] calculate a real-time resistance value of the thermistor based on the voltage division value, the voltage division value being a ratio of a voltage drop in a series circuit in which the thermistor is located to a total voltage of the series circuit between the resistance value of the thermistor and temperature.

[0049] As one of the preferred solutions, the construction module is specifically configured to:

[0050] analyze the material data to obtain a heat transfer coefficient and a thickness of each layer of material of the target capacitor, calculate an equivalent heat transfer coefficient of the target capacitor according to the heat transfer coefficient and the thickness, and the equivalent heat transfer coefficient is expressed as:

[0051] ,

[0052] ,

[0053] wherein λ th_H and λ th_V are the equivalent heat transfer coefficients of the target capacitor in horizontal and vertical directions respectively, i represents the number of material layers, λ i and δ i are the heat transfer coefficient and thickness of the i-th layer respectively, and δ represents the thickness of the target capacitor;

[0054] simplifying the target capacitor into a two-layer thermal resistance and thermal capacity network according to the structure data, and calculating the equivalent thermal conductivity of the target capacitor according to the two-layer thermal resistance and thermal capacity network;

[0055] constructing a thermal network model of the target capacitor according to the equivalent heat transfer coefficient and the equivalent thermal conductivity.

[0056] As one of the preferred solutions, the optimization module is specifically configured to:

[0057] constructing a temperature change curve according to the internal temperature data, fitting the temperature change curve to obtain a temperature fitting function, which is expressed as:

[0058] ,

[0059] wherein T(t) represents the temperature at time t, T0 is the ambient temperature, A is the amplitude, and τ is the time constant;

[0060] extracting the 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 capacity;

[0061] establishing an equivalent thermal resistance and thermal capacity network model of the target capacitor according to the thermal network parameters and the thermal network model.

[0062] As one of the preferred solutions, the calculation module is specifically configured to:

[0063] obtaining real-time current data of the target capacitor;

[0064] calculating the real-time current data to obtain the capacitance loss of the target capacitor;

[0065] calculating internal temperature rise data of the target capacitor according to the capacitance loss and the equivalent thermal resistance and thermal capacity network model;

[0066] wherein the capacitance loss is expressed as:

[0067] ,

[0068] wherein, represents a capacitance loss, represents an equivalent series resistance, represents a target capacitor current, represents a frequency.

[0069] A further embodiment of the present application provides a HVDC converter valve DC support capacitor temperature on-line monitoring device, comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, and the processor implements the HVDC converter valve DC support capacitor temperature on-line monitoring method as described above when executing the computer program.

[0070] A further embodiment of the present application provides a computer readable storage medium storing a computer program, wherein the device where the computer readable storage medium is located implements the HVDC converter valve DC support capacitor temperature on-line monitoring method as described above when executing the computer program.

[0071] Compared with the prior art, the beneficial effects of the embodiments of the present application are at least one of the following:

[0072] 1) The present application sets a thermistor on the capacitor terminal, acquires current data through a series connection acquisition circuit, and then converts the current data into voltage data through a current transformer. The voltage division value of the thermistor can be calculated to obtain the external temperature data of the capacitor. This method reduces the influence of environmental factors on temperature measurement and improves the accuracy of external temperature monitoring. At the same time, the internal temperature data is obtained through the thermocouple arranged in the capacitor, and the calculation is combined with the thermal network model to more accurately reflect the temperature distribution and change in the capacitor.

[0073] 2) The present application can obtain the external and internal temperature data of the capacitor in real time, which provides an important basis for the state monitoring and fault warning of the capacitor. By monitoring the temperature of the capacitor in real time, temperature abnormalities can be found in time and corresponding measures can be taken to avoid the failure of the capacitor due to excessive temperature. BRIEF DESCRIPTION OF DRAWINGS

[0074] Figure 1 is a flowchart of the HVDC converter valve DC support capacitor temperature on-line monitoring method in one of the embodiments of the present application;

[0075] Figure 2 is a simplified capacitor structure schematic diagram in one of the embodiments of the present application;

[0076] Figure 3 is a schematic diagram of the HVDC converter valve DC support capacitor temperature on-line monitoring system in one of the embodiments of the present application;

[0077] Figure 4 is a schematic diagram of a DC support capacitor temperature on-line monitoring device of a HVDC valve in one of the embodiments of the present application. DETAILED DESCRIPTION

[0078] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application. 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 those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0079] In the description of the present application, the terms "first", "second", "third", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second", "third", etc. can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0080] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, or the communication inside two elements. The terms "vertical", "horizontal", "left", "right", "up", "down" and similar expressions used in this paper are only for the purpose of description, and cannot be understood as indicating or implying 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 limiting the present application. The term "and / or" used in this paper includes any and all combinations of one or more related listed items. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood in specific cases.

[0081] In the description of the present application, it should be noted that, unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as understood by those skilled in the art of the technology. The terms used in the specification of the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the present application. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood in specific cases.

[0082] An embodiment of the present application provides a kind of, specifically, please see Figure 1 , Figure 1A flowchart of a method for on-line monitoring of the temperature of a DC support capacitor of a HVDC valve according to an embodiment of the present application is shown, which comprises steps S1-S6.

[0083] S1: Obtain the operating data of the thermistor installed at the terminal of the target capacitor.

[0084] It should be noted that a thermistor is a special resistor whose resistance value changes with temperature. In this step, the thermistor is installed at 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 for measuring the current passing through the thermistor, which usually includes a current source (for providing a stable current) and a current measuring element (such as an ammeter or a current sensor).

[0085] Specifically, when the temperature of the target capacitor changes, the resistance value of the thermistor also changes accordingly, resulting in a change in the current passing through it. The current measuring element in the acquisition circuit will capture this change and convert it into readable current data.

[0086] S2: Process the operating data to obtain the external temperature data of the target capacitor.

[0087] Preferably, in an embodiment of the present application, processing the operating data to obtain the external temperature data of the target capacitor comprises:

[0088] Converting the operating data to obtain voltage data;

[0089] Inputting the voltage data into a voltage amplifier for amplification and inputting the amplified voltage data into a filter circuit for filtering;

[0090] Sampling the filtered voltage data to obtain discrete digital signals, calculating the voltage division value of the thermistor based on the discrete digital signals, and the voltage division value is the ratio of the voltage drop of the thermistor in the circuit to the total voltage;

[0091] Calculating the real-time resistance value of the thermistor based on the voltage division value, and calculating the external temperature data of the target capacitor based on the corresponding relationship between the resistance value of the thermistor and the temperature.

[0092] Specifically, the operating data (current) of the target capacitor is converted into a voltage signal proportional to the primary-side 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 thermal resistor and other parts of the acquisition circuit (such as the internal resistance of the current source) will share the power supply voltage together. By measuring the voltage at the secondary side of the current transformer and using Ohm's law, the voltage across the thermal resistor, i.e. the voltage division value, can be calculated. There is a certain relationship between the resistance value of the thermal resistor and the temperature (usually a negative temperature coefficient, i.e. the higher the temperature, the smaller the resistance value). By consulting the specification book of the thermal resistor or using the calibrated temperature-resistance relationship curve, the voltage division value can be converted into the corresponding temperature value. This temperature value represents the external temperature of the target capacitor and its surrounding environment.

[0093] S3: constructing a thermal network model of the target capacitor based on the structure data and material data of the target capacitor;

[0094] In this step, the structure and material characteristics of the target capacitor need to be analyzed. These structure and material characteristics include the internal structure of the capacitor (such as the winding method of the anode foil, the cathode foil and the PP film), the material properties (such as the heat transfer coefficient and thickness of each layer) and the working conditions (such as the power level and the heat dissipation method). According to the analysis results, select the appropriate thermal network model, including Cauer model and Foster model.

[0095] Cauer model is suitable for high-frequency or complex thermal environment that needs to consider the actual physical structure inside the capacitor. This model can more accurately reflect the heat conduction and heat capacity distribution inside the capacitor.

[0096] Foster model is suitable for scenarios with high requirements for calculation simplicity, ignoring the internal physical structure and simplifying to an equivalent thermal resistance and heat capacity network. Although this model sacrifices part of the accuracy, it is simpler to calculate and is suitable for rapid analysis and preliminary design.

[0097] Preferably, in an embodiment of the present application, constructing a thermal network model of the target capacitor based on the structure data and material data of the target capacitor comprises:

[0098] Analyzing the material data to obtain the heat transfer coefficient and thickness of each layer of material of the target capacitor, calculating the equivalent heat transfer coefficient of the target capacitor according to the heat transfer coefficient and thickness, and the equivalent heat transfer coefficient is represented as:

[0099] ,

[0100] ,

[0101] wherein λ th_H and λ th_Vrespectively, are the equivalent heat transfer coefficients of the target capacitor in the horizontal and vertical directions, i represents the number of material layers, λ i and δ i respectively, are the heat transfer coefficient and thickness of the i-th layer, and δ represents the thickness of the target capacitor.

[0102] The target capacitor is simplified into a two-layer thermal resistance and capacitance network according to the structural data, and the equivalent thermal conductivity of the target capacitor is calculated according to the two-layer thermal resistance and capacitance network.

[0103] The thermal network model of the target capacitor is constructed according to the equivalent heat transfer coefficient and the equivalent thermal conductivity.

[0104] The internal structure of the capacitor can be simplified as a multi-layer structure, in which the anode foil, the cathode foil and the PP film are wound together to form a multi-layer structure. In the horizontal and vertical directions, the capacitor has different equivalent heat transfer coefficients. These coefficients can be calculated by the heat transfer coefficients and thicknesses of the layers. After further simplification, the capacitor can be regarded as a thermal resistance and capacitance network with only two layers. Specifically as shown in Figure 2 , Figure 2 is a simplified capacitor structure diagram provided by an embodiment of the present application, wherein, represents the internal resistance, represents the external resistance. The equivalent thermal conductivity λ th_in of the thermal resistance and capacitance network can be calculated by the following formula, which takes into account the thermal conductivity k paper of the PP film and the thickness δ Al of the aluminum foil.

[0105] ,

[0106] ,

[0107] .

[0108] For the HVDC system, due to the high power level, the capacitance is also large, so multiple capacitors in parallel are usually used. When performing thermal analysis, it is necessary to establish a thermal network model between the capacitors, between the capacitors and the module terminals, and between the capacitors and the sub-module shell.

[0109] S4: The thermal network model is optimized by the internal temperature data of the target capacitor obtained by the thermocouple, and an equivalent thermal resistance and capacitance network model is obtained.

[0110] In this step, a thermocouple is installed inside the capacitor to monitor temperature changes. Through running tests, temperature change data of the capacitor under different working conditions are recorded, and the collected temperature data are cleaned to remove outliers and noise, ensuring the accuracy of the data.

[0111] The cooling curve is fitted using mathematical tools such as MATLAB. The fitted 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 fitted curve and the experimental data is minimized. Using the first-order thermal network model and the relationship between time constant τ and thermal resistance Rth and thermal capacity Cth, the values of thermal resistance Rth and thermal capacity Cth can be calculated.

[0112] The obtained thermal network parameters are substituted into the thermal network model for simulation. The difference between the simulation results and the experimental data is compared. If the difference is large, the model may not be accurate or needs to be further optimized. At this time, the model parameters can be adjusted and optimized, such as re-fitting the experimental data or considering more thermal physical factors. The verification process is repeated until the model can accurately reflect the actual thermal behavior of the capacitor.

[0113] Preferably, in an embodiment of the present application, the thermal network model is optimized by the internal temperature data of the target capacitor obtained by the thermocouple, and an equivalent thermal resistance and thermal capacity network model is obtained, comprising:

[0114] According to the temperature data, a temperature change curve is constructed, and the temperature change curve is fitted to obtain a temperature fitting function, which is expressed as:

[0115] ,

[0116] Where T(t) represents the temperature at time t, T0 is the ambient temperature, A is the amplitude, and τ is the time constant;

[0117] According to the temperature fitting function, the time constant is extracted, and the thermal network parameters of the thermal network model are calculated according to the thermal network model and the time constant, including thermal resistance and thermal capacity;

[0118] According to the thermal network parameters and the thermal network model, an equivalent thermal resistance and thermal capacity network model of the target capacitor is established.

[0119] S5: inputting the obtained real-time current data of the target capacitor into the equivalent thermal resistance and thermal capacity network model for processing to obtain the internal temperature rise data of the target capacitor, wherein the processing process of the equivalent thermal resistance and thermal capacity network model is designed to eliminate the influence of capacitor loss on temperature;

[0120] Since the impedance of the thin film capacitor has obvious frequency characteristics, FFT operation needs to be performed on the current signal in the capacitor to obtain the current spectrum at each frequency point. Then, power loss calculation is carried out at each frequency point, and the losses at each frequency point are summed up to obtain a more accurate internal loss of the capacitor.

[0121] The internal temperature rise of the capacitor is solved by using the thermal network model to realize online monitoring. By inputting the current data of the capacitor, the current spectrum is calculated by using FFT, the capacitor loss is calculated, and the internal temperature rise of the capacitor is calculated by using the thermal network model. This process can reflect the thermal state of the capacitor in real time, and provide an important basis for the health management and maintenance of the capacitor.

[0122] Preferably, in one embodiment of the present application, the real-time current data of the target capacitor is input into the equivalent thermal resistance and heat capacity network model for processing to obtain the internal temperature rise data of the target capacitor, including:

[0123] Obtaining real-time current data of the target capacitor;

[0124] Performing fast Fourier transform operation on the real-time current data to obtain the capacitor loss of the target capacitor;

[0125] According to the capacitor loss and the equivalent thermal resistance and heat capacity network, the internal temperature rise data of the target capacitor is calculated;

[0126] Wherein, the capacitor loss is represented as:

[0127]

[0128] Wherein, represents the capacitor loss, represents the equivalent series resistance, represents the current of the target capacitor, represents the frequency.

[0129] S6: Fuse the external temperature data and the internal temperature rise data to realize real-time monitoring of the temperature of the target capacitor with the fused results.

[0130] In this step, the external temperature data and the internal temperature rise data are fused, including data calibration, denoising and filtering, etc. to ensure the accuracy and reliability of the data. The actual temperature of the target capacitor is calculated by using the external temperature data and the internal temperature rise data through a preset algorithm (such as a heat conduction model, a heat balance equation, etc.). In addition, in order to improve the accuracy of temperature calculation, error correction of the algorithm is needed. This can be achieved by comparing with the actual temperature measurement value, and adjusting the parameters in the algorithm to reduce the error.

[0131] A temperature threshold is set, and when the temperature of the capacitor exceeds this threshold, an alarm system is triggered. The alarm system can notify relevant personnel through sound, light or email, etc. so that they can take timely measures to prevent the capacitor from overheating or damage.

[0132] Another aspect of the present application provides a kind of flexible direct current converter valve direct current support capacitor temperature online monitoring system, specifically, please refer to​Figure 3 , Figure 3 The schematic diagram of the temperature on-line monitoring system of the DC support capacitor of the LCC valve in one of the embodiments of the application is shown, which comprises 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,

[0133] The collection module 11 is used to acquire the operation data of the thermistor arranged at the terminal of the target capacitor.

[0134] The conversion module 12 is used to process the operation data to obtain the external temperature data of the target capacitor.

[0135] The construction module 13 is used to construct the thermal network model of the target capacitor based on the structure data and material data of the target capacitor.

[0136] The optimization module 14 is used to optimize the thermal network model by the internal temperature data of the target capacitor acquired by the thermocouple to obtain the equivalent thermal resistance and heat capacity network model.

[0137] The calculation module 15 is used to input the acquired real-time current data of the target capacitor into the equivalent thermal resistance and heat capacity network model for processing to obtain the internal temperature rise data of the target capacitor, wherein the processing process of the equivalent thermal resistance and heat capacity network model is designed to eliminate the influence of the capacitor loss on the temperature.

[0138] The monitoring module 16 is used to fuse the external temperature data and the internal temperature rise data to realize real-time monitoring of the temperature of the target capacitor based on the fused result.

[0139] Preferably, in one of the embodiments of the application, the conversion module is specifically used for:

[0140] Converting the operation data to obtain voltage data;

[0141] Inputting the voltage data into a voltage amplifier for amplification processing, and inputting the voltage data after the amplification processing into a filter circuit for filtering processing;

[0142] Sampling the voltage data after the filtering processing to obtain discrete digital signals, calculating the voltage division value of the thermistor according to the discrete digital signals, and the voltage division value is the ratio of the voltage drop of the thermistor in the circuit to the total voltage;

[0143] Calculating the real-time resistance value of the thermistor based on the voltage division value, and calculating the external temperature data of the target capacitor based on the corresponding relationship between the resistance value of the thermistor and the temperature.

[0144] Preferably, in one of the embodiments of the application, the construction module is specifically used for:

[0145] The material data is analyzed to obtain the heat transfer coefficient and thickness of each layer 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, and the equivalent heat transfer coefficient is represented as:

[0146] ,

[0147] ,

[0148] wherein λ th_H and λ th_V are the equivalent heat transfer coefficients of the target capacitor in the horizontal direction and the vertical direction respectively, i represents the number of layers, λ i and δ i are the heat transfer coefficient and the thickness of the i-th layer, and δ represents the thickness of the target capacitor.

[0149] The target capacitor is simplified into a double-layer thermal resistance and thermal capacity network according to the structure data, and the equivalent thermal conductivity of the target capacitor is calculated according to the double-layer thermal resistance and thermal capacity network.

[0150] The thermal network model of the target capacitor is constructed according to the equivalent heat transfer coefficient and the equivalent thermal conductivity.

[0151] Preferably, in an embodiment of the present application, the optimization module is specifically used for:

[0152] The temperature change curve is constructed according to the temperature data, and the temperature fitting function is obtained by fitting the temperature change curve, and is represented as:

[0153] ,

[0154] wherein T(t) represents the temperature at time t, T0 is the ambient temperature, A is the amplitude, and τ is the time constant.

[0155] The time constant is extracted according to the temperature fitting function, and the thermal network parameters of the thermal network model are calculated according to the thermal network model and the time constant, wherein the thermal network parameters include thermal resistance and thermal capacity.

[0156] The equivalent thermal resistance and thermal capacity network model of the target capacitor is established according to the thermal network parameters and the thermal network model.

[0157] Preferably, in an embodiment of the present application, the calculation module is specifically used for:

[0158] The real-time current data of the target capacitor is obtained;

[0159] The real-time current data is subjected to fast Fourier transform operation to obtain the capacitance loss of the target capacitor.

[0160] The internal temperature rise data of the target capacitor is calculated according to the capacitance loss and the equivalent thermal resistance and thermal capacity network.

[0161] wherein the capacitance loss is expressed as:

[0162]

[0163] wherein, represents the capacitance loss, represents the equivalent series resistance, represents the target capacitor current, represents the frequency.

[0164] Another aspect of the present application provides a HVDC converter valve DC support capacitor temperature on-line monitoring device, in particular, see Figure 4 which is a structural diagram of the HVDC converter valve DC support capacitor temperature on-line monitoring device provided by the embodiment of the present application, the HVDC converter valve DC support capacitor temperature on-line monitoring device provided by the 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 HVDC converter valve DC support capacitor temperature on-line monitoring method embodiment are realized, for example Figure 1 the steps S1-S6 described in the above; or, when the processor 21 executes the computer program, the functions of each module in the above each device embodiment are realized, for example, the acquisition module 11.

[0165] Exemplarily, the computer program can be divided into one or more modules, 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 capable of completing a specific function, which is used to describe the execution process of the computer program in the HVDC converter valve DC support capacitor temperature on-line monitoring device. 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.

[0166] The HVDC converter valve DC support capacitor temperature on-line monitoring device can include, but is not limited to, the processor 21, the memory 22. Those skilled in the art can understand that the schematic diagram is only an example of the HVDC converter valve DC support capacitor temperature on-line monitoring device, and does not constitute a limitation on the HVDC converter valve DC support capacitor temperature on-line monitoring device, and can include more or fewer components than the diagram, or combine certain components, or different components, for example, the HVDC converter valve DC support capacitor temperature on-line monitoring device can also include an input / output device, a network access device, a bus, etc.

[0167] ​The processor 21 can be a central processing unit (CPU), and can also be 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 components, discrete hardware components, etc. The general-purpose processor can be a microprocessor or can also be any conventional processor. The processor 21 is a control center of the temperature on-line monitoring device for DC support capacitor of HVDC valve, and is connected with various parts of the temperature on-line monitoring device for DC support capacitor of HVDC valve through various interfaces and lines.

[0168] The memory 22 can be used to store computer programs and / or modules. The processor 21 realizes various functions of the temperature on-line monitoring device for DC support capacitor of HVDC valve by running or executing computer programs and / or modules stored in the memory 22, and calling data stored in the memory 22. The memory 22 can mainly include a program storage area and a data storage area. The program storage area can store an operating system, at least one application program required by a function (such as a sound playing function, an image playing function, etc.), etc. The data storage area can store data created according to use of the mobile phone (such as audio data, a phone book, etc.), etc. In addition, the memory 22 can include a high-speed random access memory, and can also include a nonvolatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, at least one disk storage device, a flash memory device, or other volatile solid-state memory devices.

[0169] If the module integrated with the HVDC valve DC support capacitor temperature on-line monitoring device is implemented in the form of a software function unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above-mentioned embodiment methods can also be completed by a computer program instructing related hardware, and the computer program can be stored in a computer-readable storage medium. When the processor executes the computer program, the steps of the above-mentioned various method embodiments can be implemented. The computer program includes computer program code, which can be in the form of source code, object code, an executable file, or some intermediate form, etc. The computer-readable medium can include any entity or device, a recording medium, a U disk, a mobile hard disk, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc. that can carry the computer program code.

[0170] Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by a computer program instructing related hardware, and the program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the above-mentioned various method embodiments. The storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM), etc.

[0171] Correspondingly, an embodiment of the present application provides a computer-readable storage medium including a stored computer program, wherein when the computer program is running, the computer-readable storage medium controls the device where the computer-readable storage medium is located to perform the steps in the HVDC valve DC support capacitor temperature on-line monitoring method of the above-mentioned embodiments, for example, the steps S1-S6 in the method described in the embodiment. Figure 1

[0172] Compared with the prior art, the beneficial effects of the embodiment of the present application are at least one of the following:

[0173] ​1) The application obtains current data by setting a thermistor on the capacitor terminal and connecting a serial acquisition circuit, and then converts the current data into voltage data using a current transformer. The voltage division value of the thermistor can be calculated to obtain the external temperature data of the capacitor. This method reduces the influence of environmental factors on temperature measurement and improves the accuracy of external temperature monitoring. At the same time, the internal temperature data is obtained by the thermocouple in the capacitor, and the calculation is combined with the thermal network model to more accurately reflect the temperature distribution and changes in the capacitor.

[0174] 2) The application can obtain real-time external and internal temperature data of the capacitor, providing an important basis for the state monitoring and fault warning of the capacitor. By monitoring the temperature of the capacitor in real time, temperature abnormalities can be detected in time and appropriate measures can be taken to avoid the failure of the capacitor due to high temperature.

[0175] The above-described embodiments only express several embodiments of the application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent of the application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the application, a number of modifications and improvements can be made, which are within the scope of protection of the application. Therefore, the protection scope of the patent of the application should be subject to the appended claims.

Claims

1. A method for on-line monitoring of temperature of DC support capacitors of a LCC valve, characterized in that, The method comprises the following steps: acquiring operation data of a thermistor arranged at a terminal of a target capacitor; processing the operation data to obtain external temperature data of the target capacitor; constructing a thermal network model of the target capacitor based on structure data and material data of the target capacitor; optimizing the thermal network model based on internal temperature data of the target capacitor acquired by a thermocouple to obtain an equivalent thermal resistance and heat capacity network model; inputting real-time current data of the target capacitor into the equivalent thermal resistance and heat capacity network model for processing to obtain internal temperature rise data of the target capacitor, wherein the processing of the equivalent thermal resistance and heat capacity network model is designed to eliminate the influence of capacitor loss on temperature; fusing the external temperature data and the internal temperature rise data to realize real-time monitoring of the temperature of the target capacitor based on the fused result; the processing of the operation data to obtain the external temperature data of the target capacitor comprises: converting the operation 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 discrete digital signals, calculating a voltage division value of the thermistor based on the discrete digital signals, the voltage division value being a ratio of a voltage drop in a series circuit in which the thermistor is arranged to a total voltage of the series circuit; calculating a real-time resistance value of the thermistor based on the voltage division value, and calculating the external temperature data of the target capacitor corresponding to the real-time resistance value based on a corresponding relationship between the resistance value of the thermistor and temperature; the construction of the thermal network model of the target capacitor based on the structure data and the material data of the target capacitor comprises: analyzing the material data to obtain a heat transfer coefficient and a thickness of each layer of material of the target capacitor, calculating an equivalent heat transfer coefficient of the target capacitor based on the heat transfer coefficient and the thickness, the equivalent heat transfer coefficient being represented as: ， ， wherein λ th_H and λ th_V are the equivalent heat transfer coefficients of the target capacitor in the horizontal and vertical directions, respectively, i denotes the material layer number, λ i and δ i are the heat transfer coefficient and thickness of the i-th layer, respectively, and δ denotes the thickness of the target capacitor; simplifying the target capacitor into a double-layer thermal resistance and heat capacity network according to the structure data, and calculating an equivalent thermal conductivity of the target capacitor based on the double-layer thermal resistance and heat capacity network; constructing the thermal network model of the target capacitor based on the equivalent heat transfer coefficient and the equivalent thermal conductivity; the fusion of the external temperature data and the internal temperature rise data to realize real-time monitoring of the temperature of the target capacitor based on the fused result comprises: calculating an actual temperature of the target capacitor by a preset algorithm using the external temperature data and the internal temperature rise data, wherein the preset algorithm comprises a heat conduction model and a heat balance equation; the inputting of the real-time current data of the target capacitor into the equivalent thermal resistance and heat capacity network model for processing to obtain the internal temperature rise data of the target capacitor comprises: acquiring real-time current data of the target capacitor; calculating the capacitor loss of the target capacitor based on the real-time current data. According to the capacitance loss and the equivalent thermal resistance and thermal capacity network model, internal temperature rise data of the target capacitor is calculated; The capacitance loss is expressed as: ， wherein, represents a capacitance loss, represents an equivalent series resistance, represents a target capacitor current, represents a frequency.

2. The temperature on-line monitoring method for DC support capacitors of a LCC valve according to claim 1, characterized in that, The internal temperature data of the target capacitor is obtained by a thermocouple, and the thermal network model is optimized to obtain an equivalent thermal resistance and thermal capacity network model, including: According to the internal temperature data, a temperature change curve is constructed, and a temperature fitting function is obtained by fitting the temperature change curve, which is expressed as: ， Wherein, T(t) represents the temperature at time t, T0 is the ambient temperature, A is the amplitude, and τ is the time constant; According to the temperature fitting function, the time constant is extracted, and the thermal network parameters of the thermal network model, including thermal resistance and thermal capacity, are calculated according to the thermal network model and the time constant; According to the thermal network parameters and the thermal network model, an equivalent thermal resistance and thermal capacity network model of the target capacitor is established.

3. A temperature on-line monitoring system for DC support capacitors of a LCC valve, characterized in that, Including: The acquisition module is used to acquire the running data of the thermistor arranged at the terminal of the target capacitor; The conversion module is used to process the running data to obtain the external temperature data of the target capacitor; The construction module is used to construct the thermal network model of the target capacitor based on the structure data and material data of the target capacitor; The optimization module is used to optimize the thermal network model by the internal temperature data of the target capacitor obtained by the thermocouple to obtain an equivalent thermal resistance and thermal capacity network model; The calculation module is used to input the real-time current data of the target capacitor into the equivalent thermal resistance and thermal capacity network model for processing to obtain the internal temperature rise data of the target capacitor, wherein the processing process of the equivalent thermal resistance and thermal capacity 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 to realize real-time monitoring of the temperature of the target capacitor based on the fused results; The conversion module is specifically used for: Converting the running data to obtain voltage data; The voltage data is input into the voltage amplifier for amplification processing, and the amplified voltage data is input into the filter circuit for filtering processing; The voltage data after filtering is sampled to obtain discrete digital signals, and the voltage division value of the thermistor is calculated according to the discrete digital signals, which is the ratio of the voltage drop in the series circuit to the 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 is the ratio of the voltage drop in the series circuit to the total voltage of the series circuit between the resistance value and the temperature of the thermistor; The construction 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, and the equivalent heat transfer coefficient of the target capacitor is calculated according to the heat transfer coefficient and the thickness, which is expressed as: ， ， wherein λ th_H and λ th_V are the equivalent heat transfer coefficients of the target capacitor in the horizontal and vertical directions, respectively, i denotes the material layer number, λ i and δ i are the heat transfer coefficient and thickness of the i-th layer, respectively, and δ denotes the thickness of the target capacitor; simplifying the target capacitor into a double-layer thermal resistance and thermal capacity network according to the structural data, and calculating an equivalent thermal conductivity of the target capacitor according to the double-layer thermal resistance and thermal capacity network; constructing a thermal network model of the target capacitor according to the equivalent heat transfer coefficient and the equivalent thermal conductivity; the monitoring module is specifically configured to: calculate an actual temperature of the target capacitor by a preset algorithm using the external temperature data and the internal temperature rise data, wherein the preset algorithm comprises a heat conduction model and a heat balance equation; the calculating module is specifically configured to: obtain real-time current data of the target capacitor; calculate a capacitance loss of the target capacitor according to the real-time current data; calculate internal temperature rise data of the target capacitor according to the capacitance loss and the equivalent thermal resistance and thermal capacity network model; wherein the capacitance loss is represented as: ， wherein, represents a capacitance loss, represents an equivalent series resistance, represents a target capacitor current, represents a frequency.

4. The temperature on-line monitoring system for DC support capacitors of a LCC valve according to claim 3, characterized in that, the optimizing module is specifically configured to: construct a temperature change curve according to the internal temperature data, fit the temperature change curve to obtain a temperature fitting function, represented as: ， wherein T(t) represents a temperature at time t, T0 is an ambient temperature, A is an amplitude, and τ is a time constant; extract a time constant according to the temperature fitting function, and calculate thermal network parameters of the thermal network model according to the thermal network model and the time constant, wherein the thermal network parameters comprise thermal resistance and thermal capacity; establish an equivalent thermal resistance and thermal capacity network model of the target capacitor according to the thermal network parameters and the thermal network model.

5. A temperature on-line monitoring device for DC support capacitors of a LCC valve, characterized in that The computer readable storage medium stores a computer program, wherein the device where the computer readable storage medium is located executes the computer program to implement the flexible DC converter valve DC support capacitor temperature online monitoring method according to any one of claims 1 to 2.

6. A computer-readable storage medium, characterized in that, The computer readable storage medium stores a computer program, wherein the device where the computer readable storage medium is located executes the computer program to implement the flexible DC converter valve DC support capacitor temperature online monitoring method according to any one of claims 1 to 2.

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