Acquisition method and device for resistance value of voltage-sharing resistor of flexible direct-current converter valve and monitoring method

Abstract

The invention discloses a flexible direct current converter valve voltage-sharing resistor resistance value obtaining method and device and a monitoring method, and the obtaining method specifically comprises the steps: firstly, presetting a time period T which is smaller than the natural discharge time of a capacitor of a flexible direct current converter valve sub-module in a module locking state; then capacitor discharge energy of the flexible direct current converter valve in the time period T is obtained, and a first energy value is obtained; obtaining a secondary board card loss value of the flexible DC converter valve in the time period T, and obtaining a second energy value; according to the difference between the first energy value and the second energy value, the energy loss of the voltage-sharing resistor of the flexible DC converter valve is obtained; and finally, calculating the resistance value of the voltage-sharing resistor according to the energy loss. According to the invention, the resistance value of the voltage-sharing resistor of each sub-module of the flexible direct current converter valve can be accurately measured, so that potential hazards can be automatically, efficiently and timely found before the performance of the resistor is degraded, and the operation stability and reliability of the flexible direct current converter valve are effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of DC power transmission, and particularly relates to a method for obtaining the resistance value of the voltage-sharing resistor of a flexible DC converter valve, a device, and a monitoring method. Background Art

[0002] Flexible DC power transmission technology has shown great application potential in the fields of offshore wind power grid connection, island power supply, and urban intelligent distribution networks due to its excellent controllability, flexibility, and stability, and has become one of the key technologies in modern power systems. With the large-scale engineering application of this technology, the reliability problem of the converter valve as a core device has become increasingly prominent. Although strengthening measures such as redundancy backup are taken in the design stage, the failure of sub-modules may still lead to the unplanned outage of the system, which will cause significant economic losses.

[0003] In this context, the operation and maintenance of the converter valve are particularly important. However, due to the fact that the equipment is usually distributed in remote areas and has a complex structure, traditional operation and maintenance face great challenges. Even when the system is shut down for maintenance, it is still extremely difficult to comprehensively detect all sub-modules. Currently, fault diagnosis mainly relies on the built-in fault signal mechanism, which locates problems by triggering alarm signals when internal components of the sub-module fail, but this method obviously has monitoring blind spots.

[0004] It should be noted that as a key component for voltage equalization, the resistance value stability of the voltage-sharing resistor is often regarded as an ideal assumption, so it is usually not taken seriously during operation and maintenance. However, the deterioration of the resistor during long-term operation will cause uneven charging of the capacitor, thus directly affecting the quality of the electric energy output by the converter valve. Due to the lack of dedicated monitoring means, currently, only manual periodic measurement of the resistance value of the voltage-sharing resistor of the flexible DC converter valve can be relied on. This passive and lagging detection method is not only inefficient, but also has low detection accuracy, and may miss potential fault hazards. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to propose a method for obtaining the resistance value of the voltage-sharing resistor of a flexible DC converter valve, a device, and a monitoring method in view of the above deficiencies of the prior art. Through this obtaining method, the resistance values of the voltage-sharing resistors of each sub-module of the flexible DC converter valve can be automatically and accurately obtained, so that potential hazards can be efficiently and timely identified before the performance of the voltage-sharing resistor of the flexible DC converter valve deteriorates, thereby improving the operation stability and reliability of the flexible DC converter valve.

[0006] In a first aspect, the present invention provides a method for obtaining the resistance value of the voltage-sharing resistor of a flexible DC converter valve, which is applied to the locked state of the flexible DC converter valve. The method includes the following steps:

[0007] A preset time period T, where the time period T is less than the time for the capacitor of the flexible DC converter valve sub-module to naturally discharge when the module is blocked;

[0008] Obtain the capacitor discharge energy of the flexible DC converter valve within the time period T to obtain a first energy value; and, obtain the loss value of the secondary board of the flexible DC converter valve within the time period T to obtain a second energy value;

[0009] Obtain the energy loss of the equalizing resistor of the flexible DC converter valve according to the difference between the first energy value and the second energy value;

[0010] Calculate the resistance value of the equalizing resistor based on the energy loss of the equalizing resistor of the flexible DC converter valve, so as to obtain the resistance value of the equalizing resistor of the flexible DC converter valve.

[0011] Further, the calculation formula for the energy loss of the equalizing resistor of the flexible DC converter valve is as follows:

[0012]

[0013] Among them, Q t represents the energy loss of the equalizing resistor of the flexible DC converter valve; Q c represents the first energy value; Q board represents the second energy value; T represents the preset time period, and p t represents the energy loss of the equalizing resistor of the flexible DC converter valve at time t.

[0014] Further, for the first energy value, its calculation formula is as follows:

[0015]

[0016] Among them, Q c is the first energy value, C is the capacitance value of the capacitor of the flexible DC converter valve sub-module, U0 is the capacitor voltage before the capacitor of the flexible DC converter valve sub-module discharges, and U T is the capacitor voltage of the flexible DC converter valve sub-module capacitor after the discharge time period T.

[0017] Further, for the second energy value, its calculation formula is as follows:

[0018]

[0019] Among them, Q board represents the second energy value, T represents the preset time period, and P board (t) represents the loss value of the secondary board of the flexible DC converter valve at time t;

[0020] The loss value P of the secondary board of the flexible DC converter valve at time t board(t), and its calculation formula is as follows:

[0021] P board (t) = U board (t) * i board (t);

[0022] Wherein, U board (t) is the capacitance voltage of the sub-module of the flexible DC converter valve; i board (t) is the input current of the energy extraction power supply of the flexible DC converter valve.

[0023] Furthermore, the calculation formula of the resistance value R of the voltage-sharing resistor is as follows:

[0024]

[0025] Wherein, U c (t) represents the voltage across the voltage-sharing resistor of the flexible DC converter valve;

[0026] P t represents the energy loss of the voltage-sharing resistor of the flexible DC converter valve at time t.

[0027] Furthermore, the voltage across the voltage-sharing resistor of the flexible DC converter valve is obtained by exponential curve fitting, and its fitting formula is as follows:

[0028] U c (t) = e attb ;

[0029] Wherein, U c (t) represents the voltage across the voltage-sharing resistor of the flexible DC converter valve; a and b are both fitting coefficients of the exponential curve;

[0030] Converting the exponential curve can obtain the ideal fitting straight-line equation:

[0031] lnU c (t) = at + b;

[0032] Wherein, a and b are the slope and constant of the ideal fitting straight-line equation respectively, and a and b are obtained by fitting the data points within the time period T using the least squares method.

[0033] In a second aspect, the present invention provides a monitoring method for a flexible DC converter valve, and the method includes the following steps:

[0034] Adopt the method for obtaining the resistance value of the voltage-sharing resistor of the flexible DC converter valve described in the first aspect to obtain the resistance value of the voltage-sharing resistor of the flexible DC converter valve;

[0035] Compare the resistance value of the voltage-sharing resistor with the design value or the historical normal operation value, and screen out the abnormal resistance values;

[0036] Adjust the screened abnormal resistance values to complete the monitoring of the flexible DC converter valve.

[0037] Thirdly, the present invention provides a device for obtaining the resistance value of the grading resistor of a flexible DC converter valve, which is applied to the blocked state of the flexible DC converter valve. The device includes:

[0038] A preset unit for presetting a time period T, where the time period T is less than the time for the capacitor of the sub-module of the flexible DC converter valve to naturally discharge completely in the blocked state of the module;

[0039] An acquisition unit, connected to the preset unit, for acquiring the capacitor discharge energy of the flexible DC converter valve within the time period T to obtain a first energy value; and for acquiring the loss value of the secondary board of the flexible DC converter valve within the time period T to obtain a second energy value;

[0040] A first calculation unit, connected to the acquisition unit, for obtaining the energy loss of the grading resistor of the flexible DC converter valve according to the difference between the first energy value and the second energy value;

[0041] A second calculation unit, connected to the first calculation unit, for calculating the resistance value of the grading resistor according to the energy loss of the grading resistor of the flexible DC converter valve, so as to obtain the resistance value of the grading resistor of the flexible DC converter valve.

[0042] Further, the first calculation unit stores a calculation formula for the energy loss of the grading resistor of the flexible DC converter valve, specifically as follows:

[0043]

[0044] Among them, Q t represents the energy loss of the grading resistor of the flexible DC converter valve; Q c represents the first energy value; Q board represents the second energy value; T represents the preset time period, and p t represents the energy loss of the grading resistor of the flexible DC converter valve at time t.

[0045] Further, the acquisition unit includes a first acquisition unit;

[0046] The first acquisition unit is connected to the preset unit for acquiring the capacitor discharge energy of the flexible DC converter valve within the time period T to obtain a first energy value;

[0047] The first acquisition unit stores a calculation formula for the first energy value, specifically as follows:

[0048]

[0049] Among them, Q c is the first energy value, C is the capacitance value of the sub-module capacitor of the flexible DC converter valve, U0 is the capacitor voltage of the sub-module capacitor of the flexible DC converter valve before discharge, and U T is the capacitor voltage of the sub-module capacitor of the flexible DC converter valve after the discharge time period T.

[0050] Furthermore, the obtaining unit further includes a second obtaining unit;

[0051] The second obtaining unit is connected to the preset unit and is configured to obtain the loss value of the secondary board of the flexible DC converter valve within the time period T to obtain a second energy value;

[0052] The second obtaining unit stores the calculation formula of the second energy value, which is specifically as follows:

[0053]

[0054] Among them, Q board represents the second energy value, T represents the preset time period, and P board (t) represents the loss value of the secondary board of the flexible DC converter valve at time t;

[0055] The loss value P of the secondary board of the flexible DC converter valve at time t board (t), and its calculation formula is as follows:

[0056] P board (t) = U board (t) * i board (t);

[0057] Among them, U board (t) is the capacitor voltage of the sub-module of the flexible DC converter valve; i board (t) is the input current of the energy extraction power supply of the flexible DC converter valve.

[0058] Furthermore, the second calculation unit stores the calculation formula of the resistance value R of the voltage-sharing resistor and the calculation formula of the energy loss of the voltage-sharing resistor of the flexible DC converter valve;

[0059] The calculation formula of the resistance value R of the voltage-sharing resistor is as follows:

[0060]

[0061] Among them, U c (t) represents the voltage across the voltage-sharing resistor of the flexible DC converter valve, and the voltage across the voltage-sharing resistor of the flexible DC converter valve is obtained by exponential curve fitting;

[0062] P t represents the energy loss of the voltage-sharing resistor of the flexible DC converter valve at time t.

[0063] Through this acquisition method, the present invention can automatically and accurately obtain the resistance values of the voltage-sharing resistors of each sub-module of the flexible DC converter valve, so that potential hidden dangers can be efficiently and timely detected before the resistance performance deteriorates, effectively improving the operation stability and reliability of the flexible DC converter valve. The specific beneficial effects are as follows:

[0064] 1. Automatic and precise measurement: The present invention does not require direct manual measurement. By directly measuring the energy of capacitor discharge and the loss of the secondary board, the loss situation of the voltage-sharing resistor is accurately evaluated and the accurate resistance value is calculated, providing reliable data for equipment status evaluation and helping engineers deeply understand the electrical performance of each sub-module.

[0065] 2. Preventive maintenance: By analyzing the loss situation of the voltage-sharing resistor, the present invention can detect the problem of resistance performance deterioration in advance, enabling the operation and maintenance team to take preventive maintenance measures before a failure occurs, reducing downtime and maintenance costs, and improving the overall reliability of the system.

[0066] 3. Strong adaptability: During the measurement process, the selection of the time period T is flexible and can be adjusted according to the specific operation conditions. It is applicable to power systems in various operation scenarios, has wide generality, and can be widely applied to different flexible DC transmission projects.

[0067] 4. Reducing operation and maintenance costs: Precise monitoring and fault warning help the operation and maintenance team detect problems in advance and optimize the maintenance strategy, reducing the repair and replacement costs caused by sudden equipment failures, avoiding unnecessary shutdowns and inspections, thereby reducing the overall operation and maintenance costs and improving economic benefits.

[0068] 5. Data-driven decision support: The obtained resistance values and loss information provide reliable data support for operation and maintenance decisions, helping engineers formulate and optimize maintenance strategies, enhancing the management level of the converter valve system, improving operation efficiency, and ensuring the long-term stable operation of the equipment.

[0069] 6. Improving operation stability: By accurately obtaining the resistance values of the voltage-sharing resistors and optimizing voltage balance, the operation stability and efficiency of the flexible DC converter valve are effectively improved, the failure risk caused by resistance problems is reduced, and the safe operation of the power system is guaranteed. Brief Description of the Drawings

[0070] Figure 1 It is a schematic diagram of the method for obtaining the resistance values of the voltage-sharing resistors of the flexible DC converter valve in the embodiment of the present invention;

[0071] Figure 2 It is a flowchart of the method for obtaining the resistance values of the voltage-sharing resistors of the flexible DC converter valve in the embodiment of the present invention;

[0072] Figure 3Schematic diagram for obtaining power consumption of the secondary board card of the flexible DC converter valve in the embodiment of the present invention;

[0073] Figure 4 Schematic diagram of the device for obtaining the resistance value of the voltage-sharing resistor of the flexible DC converter valve in the embodiment of the present invention.

[0074] Reference numerals: 10, preset unit; 20, acquisition unit; 30, first calculation unit; 40, second calculation unit. Detailed implementation manners

[0075] To enable those skilled in the art to better understand the technical solutions of the present invention, the following will further describe the embodiments of the present invention in detail with reference to the drawings.

[0076] It can be understood that the specific embodiments and drawings described herein are only used to explain the present invention, rather than limiting the present invention.

[0077] It can be understood that, without conflict, the various embodiments and features in the embodiments of the present invention can be combined with each other.

[0078] It can be understood that, for the convenience of description, only the parts related to the present invention are shown in the drawings of the present invention, and the parts unrelated to the present invention are not shown in the drawings.

[0079] It can be understood that each unit and module involved in the embodiments of the present invention may correspond to only one physical structure, or may be composed of multiple physical structures, or multiple units and modules may also be integrated into one physical structure.

[0080] It can be understood that, without conflict, the functions and steps marked in the flowcharts and block diagrams of the present invention may occur in an order different from that marked in the drawings.

[0081] It can be understood that in the flowcharts and block diagrams of the present invention, the possible architectures, functions, and operations of the systems, devices, equipment, and methods according to the embodiments of the present invention are shown. Among them, each block in the flowchart or block diagram may represent a unit, module, program segment, or code, which contains executable instructions for implementing the specified function. Moreover, each block or combination of blocks in the block diagram and flowchart can be implemented by a hardware-based system for implementing the specified function, or by a combination of hardware and computer instructions.

[0082] It can be understood that the units and modules involved in the embodiments of the present invention can be implemented in software or in hardware. For example, the units and modules can be located in the processor.

[0083] Embodiment 1:

[0084] This embodiment provides a method for obtaining the resistance value of the grading resistor of a flexible DC converter valve, which is applied to the locked state of the flexible DC converter valve. This method is mainly applied to equipment maintenance, fault diagnosis, and system performance evaluation. During regular equipment maintenance and repair, this method can safely obtain the resistance value of the grading resistor, ensure accurate measurement in the locked state, and thus avoid affecting the stability of the power system. In addition, when a fault occurs, technicians can use this method to quickly evaluate the performance of the resistor, locate the problem, and take corresponding repair measures. At the same time, in the design and acceptance stages of new equipment, this method also provides important data support for optimizing the design, ensuring overall reliability and efficient operation.

[0085] As Figure 1 and Figure 2 shown, the method in this embodiment includes the following steps:

[0086] Step S1: Preset a time period T, where the time period T is less than the time for the capacitor of the flexible DC converter valve sub-module to naturally discharge completely in the module locked state.

[0087] In the operation and maintenance of the flexible DC converter valve, the preset time period T is a key parameter, which is set to be less than the time for the capacitor in the converter valve sub-module to naturally discharge completely in the locked state. The setting of this time period aims to ensure that when the capacitor voltage has not completely discharged, by collecting the voltage data within this time period, an exponential curve close to the actual discharge curve can be fitted using the least squares method. This method not only improves the measurement accuracy but also helps to detect potential deterioration of the grading resistor performance in a timely manner, so as to take preventive maintenance measures to ensure the stable operation of the converter valve and the reliability of the overall system. In this embodiment, when the module is in the locked state, the capacitor starts to discharge naturally, and the valve control system can capture each moment during the natural decay process of the power module capacitor voltage and record the capacitor voltage value at intervals of 100 milliseconds for 5 seconds continuously, finally obtaining 50 capacitor voltage sampling points. This high-frequency sampling method provides rich information for subsequent data analysis and helps to optimize maintenance decisions.

[0088] Step S2: Obtain the capacitor discharge energy of the flexible DC converter valve within the time period T to obtain a first energy value; and obtain the loss value of the secondary board of the flexible DC converter valve within the time period T to obtain a second energy value.

[0089] The formula for the first energy value is as follows:

[0090]

[0091] where Q c is the first energy value, C is the capacitance value of the capacitor of the flexible DC converter valve sub-module, U0 is the capacitor voltage of the flexible DC converter valve sub-module before capacitor discharge, UT is the capacitor voltage after the capacitor discharge time period T of the flexible DC converter valve sub-module.

[0092] As a specific implementation manner, the calculation formula of the second energy value is as follows:

[0093]

[0094] where Q board represents the second energy value, T represents the preset time period, and P board (t) represents the loss value of the secondary board of the flexible DC converter valve at time t;

[0095] The loss value P of the secondary board of the flexible DC converter valve at time t board (t), its calculation formula is as follows:

[0096] P board (t) = U board (t) * i board (t);

[0097] where U board (t) is the capacitor voltage of the flexible DC converter valve sub-module; i board (t) is the input current of the energy extraction power supply of the flexible DC converter valve.

[0098] As a specific implementation manner, the calculation formula of the resistance value R of the voltage-sharing resistor is as follows:

[0099]

[0100] where U c (t) represents the voltage across the voltage-sharing resistor of the flexible DC converter valve;

[0101] P t represents the energy loss of the voltage-sharing resistor of the flexible DC converter valve at time t;

[0102] The calculation formula of the energy loss of the voltage-sharing resistor of the flexible DC converter valve is as follows:

[0103]

[0104] where T represents the preset time period, and P t represents the energy loss of the voltage-sharing resistor of the flexible DC converter valve at time t.

[0105] As a specific implementation manner, the voltage across the voltage-sharing resistor of the flexible DC converter valve is obtained by exponential curve fitting, and its fitting formula is as follows:

[0106] U c (t) = e at+b ;

[0107] Converting the exponential curve gives the ideal fitting straight-line equation:

[0108] lnU c (t) = at + b;

[0109] Wherein, a and b are respectively the slope and the constant of the ideal fitting straight-line equation, and a and b are obtained by fitting the data points within the time period T using the least squares method.

[0110] Step S3: Obtain the energy loss of the voltage-sharing resistor of the flexible DC converter valve according to the difference between the first energy value and the second energy value;

[0111] The calculation formula for the energy loss of the voltage-sharing resistor of the flexible DC converter valve is as follows:

[0112]

[0113] Wherein, Q t represents the energy loss of the voltage-sharing resistor of the flexible DC converter valve; Q c represents the first energy value; Q board represents the second energy value; T represents the preset time period, and P t represents the energy loss of the voltage-sharing resistor of the flexible DC converter valve at time t.

[0114] In addition to directly calculating the energy loss of the voltage-sharing resistor of the flexible DC converter valve by subtracting the second energy value from the first energy value, the ratio of the first energy value and the second energy value can also be considered, combined with factors such as the power factor and the load current, so as to obtain a more accurate loss assessment. However, in this embodiment, a simple direct subtraction method is selected because this method is more convenient and facilitates quick calculation and analysis.

[0115] Step S4: Calculate the resistance value of the voltage-sharing resistor according to the energy loss of the voltage-sharing resistor of the flexible DC converter valve, so as to obtain the resistance value of the voltage-sharing resistor of the flexible DC converter valve.

[0116] The voltage across both ends of the voltage-sharing resistor of the flexible DC converter valve is obtained by fitting an exponential curve, and its fitting formula is as follows:

[0117] U c (t) = e at+b ;

[0118] Wherein, U c (t) represents the voltage across both ends of the voltage-sharing resistor of the flexible DC converter valve; a and b are both fitting coefficients of the exponential curve;

[0119] Converting the exponential curve gives the ideal fitting straight-line equation:

[0120] lnU c (t) = at + b;

[0121] Where a and b are the slope and constant of the ideal fitting straight line equation respectively, and a and b are obtained by fitting the data points within the time period T using the least squares method.

[0122] There are several main reasons for choosing exponential curve fitting to obtain the voltage across the grading resistor of the flexible DC converter valve. First, the exponential model can effectively describe the non-linear relationship between voltage and time or other variables. Especially when the system has a rapid dynamic response or there is an exponential decay phenomenon, it can capture the voltage change law more accurately. Second, using exponential curve fitting can reduce the influence of noise in the data, thus improving the smoothness and reliability of the fitting result. In addition, the function form generated by exponential fitting is usually relatively simple, which is convenient for subsequent calculations and implementations, making it more efficient in practical applications.

[0123] However, in addition to obtaining the voltage across the grading resistor through exponential curve fitting, statistical analysis can also be carried out using the method of actual measurement and data acquisition to determine the voltage value. This includes dynamically monitoring the voltage under different working conditions, collecting the voltage data in real time using sensors, and then directly obtaining the voltage situation across the grading resistor after filtering and processing, so that a more accurate voltage value can be obtained.

[0124] Figure 2 Describes the process for monitoring and calculating the resistance value of the grading resistor in the flexible DC converter valve. The specific steps are as follows:

[0125] (1) Module locking: The system is first in the locked state to prepare for capacitor discharge.

[0126] (2) Capacitor discharge start: Start the capacitor discharge process to release the stored energy.

[0127] (3) Measure the capacitor voltage Uc(t): During the discharge process, monitor the voltage change of the capacitor in real time.

[0128] (4) Measure the current i board (t) at the input of the energy extraction power supply: At the same time, measure the current at the input of the energy extraction power supply through a current sensor.

[0129] (5) Fit the capacitor voltage discharge curve: Using the obtained voltage data, fit the discharge curve of the capacitor voltage, assuming that the curve follows the form of exponential decay.

[0130] (6) Calculate the capacitor discharge energy: According to the fitted discharge curve, calculate the total energy released by the capacitor during the discharge process.

[0131] (7) Monitor the power consumption of the secondary board: Calculate the power consumption of the secondary board by monitoring the input current and voltage of the energy-taking power supply.

[0132] (8) Calculate the loss of the voltage-sharing resistor: Calculate the loss of the voltage-sharing resistor by comparing the energy discharged by the capacitor with the power consumption of the secondary board.

[0133] (9) Calculate the resistance value of the voltage-sharing resistor: Determine its resistance value based on the calculated loss of the voltage-sharing resistor.

[0134] (10) Output the monitoring result of the voltage-sharing resistor resistance value: Finally, output the calculated resistance value of the voltage-sharing resistor for subsequent monitoring and analysis.

[0135] Through this process, accurate monitoring and management of the voltage-sharing resistor resistance value can be achieved, improving the operation efficiency and reliability of the flexible DC converter valve.

[0136] Figure 3 Shows a schematic diagram of obtaining the power consumption of the secondary board of the flexible DC converter valve. The block diagram includes multiple key components and their connection relationships. The module capacitor, as an energy storage element, is responsible for storing energy; the voltage sampling circuit monitors the capacitor voltage through a current sensor; the current sensor is connected to the energy-taking power supply to measure the current flowing through the power supply. The unit control board, as the control center of the sub-module, receives data from the voltage sampling circuit and the current sensor to monitor and control the operation of the sub-module. Finally, the valve control coordinates the operation of the entire flexible DC converter valve and responds to the instructions of the unit control board.

[0137] The design of this monitoring system aims to ensure the stable operation of the sub-module of the flexible DC converter valve. By real-time monitoring the voltage change of the module capacitor and the input current of the energy-taking power supply, the system can identify and handle potential problems in a timely manner, thus improving the overall reliability and efficiency. This comprehensive monitoring solution not only provides the necessary information support for operation but also enhances the system's response ability to abnormal situations.

[0138] Specifically, taking a sub-module of a flexible DC converter valve as an example, assume that the capacitance value of the capacitor of this flexible DC converter valve sub-module is 10 mF, the initial voltage is 2 kV, the voltage after 5 seconds of discharge is 1.5 kV, the input current of the energy-taking power supply is 0.1 A, and the capacitor voltage linearly decays from 2 kV to 1.5 kV. First, calculate the first energy value, that is, the energy discharged by the capacitor

[0139]

[0140] Then calculate the loss Q of the secondary board board , assuming the current is constant and the voltage linearly decays, calculate through integration:

[0141]

[0142] Based on the above calculations, further calculate the parameters of the voltage-sharing resistors. The energy dissipated by the resistors is as follows:

[0143]

[0144] Next, calculate the capacitor voltage of the sub-module. Since the attenuation of the sub-module capacitor voltage is not a traditional RC curve, the loss of the secondary circuit board cannot be directly calculated. Therefore, assume that the ideal curve type of the capacitor voltage discharge is an exponential curve. Thus, an extremely close exponential curve can be fitted using 50 voltage sampling points of the capacitor voltage, and then the loss of the voltage-sharing resistor can be obtained.

[0145] Assume that the ideal exponential curve of the voltage-sharing resistor voltage is:

[0146] U c (t) = e at+b

[0147] Taking the logarithm of both sides of the formula, we can get:

[0148] lnU c (t) = at + b

[0149] Let lnU c (t) = Y, at = X, then we can get:

[0150] Y = aX + b

[0151] Substitute the 50 capacitor voltages within 5 s of discharge into the above formula. By using the least squares method, the values of a and b can be obtained as:

[0152]

[0153] Substitute the values of a and b into the loss formula to obtain the voltage of the voltage-sharing resistor.

[0154] Finally, calculate the resistance value R of the voltage-sharing resistor. Its calculation formula is as follows:

[0155]

[0156] Among them, U c (t) represents the voltage across the voltage-sharing resistor of the flexible DC converter valve;

[0157] P t represents the energy loss of the voltage-sharing resistor of the flexible DC converter valve at time t;

[0158] The calculation formula for the energy loss of the voltage-sharing resistor of the flexible DC converter valve is as follows:

[0159]

[0160] Among them, T represents the preset time period, Pt Represents the energy loss of the grading resistor of the flexible DC converter valve at time t.

[0161] This embodiment proposes a method for accurately obtaining the resistance value of the grading resistor of the flexible DC converter valve. The specific steps are as follows: First, preset a time period T (for example, 5 seconds) that is less than the natural discharge time of the capacitor, and collect the capacitor voltage at intervals of 100 milliseconds when the module is in the locked state to obtain 50 sampling points. Then, calculate the capacitor discharge energy (i.e., the first energy value) and the loss of the secondary board (i.e., the second energy value) within this time period T. The capacitor discharge energy is calculated through the difference between the initial voltage and the terminal voltage, and the loss of the secondary board is obtained by integrating the voltage and current at the power input terminal of the energy extraction power supply through real-time monitoring. Subsequently, calculate the loss of the grading resistor by calculating the difference between the two, and determine the voltage value across the resistor based on the fitted exponential curve, and finally calculate the accurate resistance value of the grading resistor. The implementation of this method significantly improves the operating reliability of the converter valve, and at the same time improves the maintenance efficiency, enabling the system to more efficiently monitor and respond to potential problems and minimize risks.

[0162] Embodiment 2:

[0163] This embodiment provides a monitoring method for a flexible DC converter valve. The method includes the following steps:

[0164] Adopt the method for obtaining the resistance value of the grading resistor of the flexible DC converter valve described in Embodiment 1 to obtain the resistance value of the grading resistor of the flexible DC converter valve;

[0165] Compare the resistance value of the grading resistor with the design value or the historical normal operating value to screen out abnormal resistance values;

[0166] Adjust the screened abnormal resistance values to complete the monitoring of the flexible DC converter valve.

[0167] This embodiment proposes a monitoring method for a flexible DC converter valve. First, adopt the method for obtaining the resistance value of the grading resistor described in Embodiment 1 to accurately calculate the resistance value of the grading resistor of the flexible DC converter valve. Then, compare this resistance value with the original design value or the historical normal operating value to identify and screen out abnormal resistance values. Finally, make necessary adjustments to the screened abnormal resistance values to ensure the operating stability and reliability of the flexible DC converter valve, so as to achieve effective monitoring and management. This series of steps aims to improve the performance of the flexible DC converter valve and ensure that it always remains in a normal operating state during operation.

[0168] Embodiment 3:

[0169] As Figure 4As shown in the figure, this embodiment provides a device for obtaining the resistance value of the grading resistor of a flexible DC converter valve, which is applied to the blocked state of the flexible DC converter valve. The device includes:

[0170] A preset unit 10, configured to preset a time period T, where the time period T is less than the time for the capacitor of the flexible DC converter valve sub-module to naturally discharge completely in the blocked state of the module;

[0171] An acquisition unit 20, connected to the preset unit 10, configured to acquire the capacitor discharge energy of the flexible DC converter valve within the time period T to obtain a first energy value; and, configured to acquire the loss value of the secondary board of the flexible DC converter valve within the time period T to obtain a second energy value;

[0172] A first calculation unit 30, connected to the acquisition unit 20, configured to obtain the energy loss of the grading resistor of the flexible DC converter valve according to the difference between the first energy value and the second energy value;

[0173] A second calculation unit 40, connected to the first calculation unit 30, configured to calculate the resistance value of the grading resistor according to the energy loss of the grading resistor of the flexible DC converter valve, so as to obtain the resistance value of the grading resistor of the flexible DC converter valve.

[0174] As a specific implementation manner, the first calculation unit 30 stores a calculation formula for the energy loss of the grading resistor of the flexible DC converter valve, which is specifically as follows:

[0175]

[0176] Wherein, Q t represents the energy loss of the grading resistor of the flexible DC converter valve; Q c represents the first energy value; Q board represents the second energy value; T represents the preset time period, and P t represents the energy loss of the grading resistor of the flexible DC converter valve at time t.

[0177] As a specific implementation manner, the acquisition unit 20 includes a first acquisition unit;

[0178] The first acquisition unit is connected to the preset unit, and is configured to acquire the capacitor discharge energy of the flexible DC converter valve within the time period T to obtain a first energy value;

[0179] The first acquisition unit stores a calculation formula for the first energy value, which is specifically as follows:

[0180]

[0181] Wherein, Q cis the first energy value, C is the capacitance value of the capacitor of the flexible DC converter valve sub-module, U0 is the capacitor voltage before the capacitor of the flexible DC converter valve sub-module discharges, U T is the capacitor voltage after the discharge time period T of the capacitor of the flexible DC converter valve sub-module.

[0182] As a specific implementation manner, the obtaining unit 20 further includes a second obtaining unit;

[0183] The second obtaining unit is connected to the preset unit, and is used for obtaining the loss value of the secondary board of the flexible DC converter valve within the time period T to obtain a second energy value;

[0184] The second obtaining unit stores the calculation formula of the second energy value, which is specifically as follows:

[0185]

[0186] Among them, T represents a preset time period, P board (t) represents the loss value of the secondary board of the flexible DC converter valve at the moment t;

[0187] The loss value P of the secondary board of the flexible DC converter valve at the moment t board (t), and its calculation formula is as follows:

[0188] P board (t) = U board (t) * i board (t);

[0189] Among them, U board (t) is the capacitor voltage of the flexible DC converter valve sub-module; i board (t) is the input current of the energy extraction power supply of the flexible DC converter valve.

[0190] As a specific implementation manner, the second calculation unit 40 stores the calculation formula of the resistance value R of the voltage-sharing resistor and the calculation formula of the energy loss of the voltage-sharing resistor of the flexible DC converter valve;

[0191] The calculation formula of the resistance value R of the voltage-sharing resistor is as follows:

[0192]

[0193] Among them, U c (t) represents the voltage across the voltage-sharing resistor of the flexible DC converter valve, and the voltage across the voltage-sharing resistor of the flexible DC converter valve is obtained by exponential curve fitting;

[0194] P t represents the energy loss of the voltage-sharing resistor of the flexible DC converter valve at the moment t.

[0195] The device in this embodiment can execute the method in Embodiment 1.

[0196] It can be understood that the above embodiments are merely exemplary embodiments adopted to illustrate the principle of the present invention. However, the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered within the protection scope of the present invention.

Claims

1. A method for obtaining the resistance value of the voltage-sharing resistor of a flexible DC converter valve, which is applied to the blocked state of the flexible DC converter valve, is characterized in that The method includes the following steps: Preset a time period T, where the time period T is less than the time for the capacitor of the flexible DC converter valve sub-module to naturally discharge completely in the module blocking state; Obtain the capacitor discharge energy of the flexible DC converter valve within the time period T to obtain a first energy value; and, obtain the secondary board card loss value of the flexible DC converter valve within the time period T to obtain a second energy value; Obtain the energy loss of the equalizing resistor of the flexible DC converter valve according to the difference between the first energy value and the second energy value; Calculate the resistance value of the equalizing resistor according to the energy loss of the equalizing resistor of the flexible DC converter valve, so as to obtain the resistance value of the equalizing resistor of the flexible DC converter valve.

2. The method for obtaining the resistance value of the equalizing resistor of the flexible DC converter valve according to claim 1, characterized in that The calculation formula for the energy loss of the equalizing resistor of the flexible DC converter valve is as follows: Among them, Q t represents the energy loss of the equalizing resistors of the flexible DC converter valve; Q c represents the first energy value; Q board represents the second energy value; T represents a preset time period, and P t represents the energy loss of the equalizing resistors of the flexible DC converter valve at time t.

3. The method for obtaining the resistance value of the equalizing resistor of the flexible DC converter valve according to claim 1, characterized in that The first energy value, its calculation formula is as follows: Among them, Q c is the first energy value, C is the capacitance value of the capacitor of the flexible DC converter valve sub-module, U0 is the capacitor voltage of the flexible DC converter valve sub-module capacitor before discharge, and U T is the capacitor voltage of the flexible DC converter valve sub-module capacitor after the discharge time period T.

4. The method for obtaining the resistance value of the equalizing resistor of the flexible DC converter valve according to claim 1, characterized in that The second energy value, its calculation formula is as follows: Among them, Q board represents the second energy value, T represents a preset time period, and P board (t) represents the loss value of the secondary board of the flexible DC converter valve at time t; The loss value P of the secondary board of the flexible DC converter valve at time t board (t) is calculated as follows: P board (t) = U board (t) * i board (t); Among them, U board (t) is the capacitor voltage of the flexible DC converter valve sub-module; i board (t) is the input current of the energy extraction power supply of the flexible DC converter valve.

5. The method for obtaining the resistance value of the equalizing resistor of the flexible DC converter valve according to any one of claims 1 to 4, characterized in that The calculation formula for the resistance value R of the equalizing resistor is as follows: Among them, U c (t) represents the voltage across both ends of the grading resistor of the flexible DC converter valve; P t Represents the energy loss of the equalizing resistors of the flexible DC converter valve at time t.

6. The method for obtaining the resistance value of the equalizing resistor of the flexible DC converter valve according to claim 5, characterized in that The voltage at both ends of the equalizing resistor of the flexible DC converter valve is obtained by exponential curve fitting, and its fitting formula is as follows: U c (t) = e at+b ; Among them, U c (t) represents the voltage across both ends of the grading resistor of the flexible DC converter valve; both a and b are fitting coefficients of the exponential curve; Converting the exponential curve can obtain the ideal fitting straight line equation: lnU c (t) = at + b; Wherein, a and b are respectively the slope and constant of the ideal fitting straight line equation, and a and b are obtained by fitting the data points within the time period T using the least squares method.

7. A monitoring method for a flexible DC converter valve, characterized in that The method includes the following steps: Adopt the method for obtaining the resistance value of the equalizing resistor of the flexible DC converter valve according to any one of claims 1 to 6 to obtain the resistance value of the equalizing resistor of the flexible DC converter valve; Compare the resistance value of the equalizing resistor with the design value or the historical normal operation value, and screen out abnormal resistance values; Adjust the screened abnormal resistance values to complete the monitoring of the flexible DC converter valve.

8. A device for obtaining the resistance value of the grading resistor of a flexible DC converter valve, which is applied to the locked state of the flexible DC converter valve, is characterized in that, Includes: A preset unit for presetting a time period T, where the time period T is less than the time for the capacitor of the flexible DC converter valve sub-module to naturally discharge completely in the module blocking state; An acquisition unit connected to the preset unit for acquiring the capacitor discharge energy of the flexible DC converter valve within the time period T to obtain a first energy value; And for acquiring the secondary board card loss value of the flexible DC converter valve within the time period T to obtain a second energy value; A first calculation unit connected to the acquisition unit for obtaining the energy loss of the equalizing resistor of the flexible DC converter valve according to the difference between the first energy value and the second energy value; A second calculation unit connected to the first calculation unit for calculating the resistance value of the equalizing resistor according to the energy loss of the equalizing resistor of the flexible DC converter valve, so as to obtain the resistance value of the equalizing resistor of the flexible DC converter valve.

9. The device for obtaining the resistance value of the equalizing resistor of the flexible DC converter valve according to claim 8, characterized in that the first calculation unit stores the calculation formula for the energy loss of the equalizing resistor of the flexible DC converter valve, which is specifically as follows: Among them, Q t represents the energy loss of the grading resistor of the flexible DC converter valve; Q c represents the first energy value; Q board represents the second energy value; T represents a preset time period, and P t represents the energy loss of the grading resistor of the flexible DC converter valve at time t.

10. The device for obtaining the resistance value of the equalizing resistor of the flexible DC converter valve according to claim 8, characterized in that the obtaining unit includes a first obtaining unit; the first obtaining unit is connected to the preset unit and is used to obtain the capacitor discharge energy of the flexible DC converter valve within the time period T to obtain a first energy value; the first obtaining unit stores the calculation formula for the first energy value, which is specifically as follows: Among them, Q c is the first energy value, C is the capacitance value of the capacitor of the flexible DC converter valve sub-module, U0 is the capacitor voltage of the flexible DC converter valve sub-module capacitor before discharge, and U T is the capacitor voltage of the flexible DC converter valve sub-module capacitor after the discharge time period T.

11. The device for obtaining the resistance value of the equalizing resistor of the flexible DC converter valve according to claim 10, characterized in that the obtaining unit further includes a second obtaining unit; the second obtaining unit is connected to the preset unit and is used to obtain the secondary board card loss value of the flexible DC converter valve within the time period T to obtain a second energy value; the second obtaining unit stores the calculation formula for the second energy value, which is specifically as follows: Among them, Q board represents the second energy value, T represents the preset time period, and P board (t) represents the loss value of the secondary board of the flexible DC converter valve at time t; The loss value P of the secondary board of the flexible DC converter valve at time t board (t) is calculated as follows: P board P(t)=U board (t)*i board (t); Among them, U board (t) is the capacitor voltage of the flexible DC converter valve sub-module; i board (t) is the input current of the energy extraction power supply of the flexible DC converter valve.

12. The device for obtaining the resistance value of the equalizing resistor of the flexible DC converter valve according to any one of claims 8 to 11, characterized in that the second calculation unit stores the calculation formula for the resistance value R of the equalizing resistor and the calculation formula for the energy loss of the equalizing resistor of the flexible DC converter valve; The calculation formula for the resistance value R of the equalizing resistor is as follows: Among them, U c (t) represents the voltage across both ends of the grading resistor of the flexible DC converter valve, and the voltage across both ends of the grading resistor of the flexible DC converter valve is obtained by exponential curve fitting; P t Represents the energy loss of the equalizing resistors of the flexible DC converter valve at time t.

Images