A method for evaluating the transmission performance of a flexible direct-current current transformer under fault and related equipment

Abstract

The application discloses a kind of flexible direct current under current transformer's transmission and transformation performance evaluation method and related equipment, method includes: the remote module of the current transformer to be evaluated is set to working state;Determine flexible direct current fault current continuous function according to flexible direct current system parameter, determine shunt output small voltage continuous function in combination with shunt parameter, further determine small voltage analog signal and output to remote module, receive the test current digital signal returned;Determine test current sample value sequence according to test current digital signal, determine standard current sample value sequence according to evaluation synchronization parameter and flexible direct current fault current continuous function;According to two sample value sequences, determine the transmission and transformation performance evaluation result of the current transformer to be evaluated.The application embodiment can realize the evaluation of the transmission and transformation performance of the current transformer to be evaluated without applying actual fault high current, with higher credibility.The application can be widely applied in the field of current transformer technology.

Description

Technical Field

[0001] This application relates to the field of current transformer technology, and in particular to a method and related equipment for evaluating the transmission performance of a current transformer under flexible DC faults. Background Technology

[0002] With the rapid development of high-power fully controlled power electronic devices and the continuous improvement of DC grid manufacturing capabilities, flexible DC transmission technology has received increasing attention and application in the field of high-voltage DC transmission, and it will become the most important transmission method in DC grids. Unlike current source converter-type high-voltage DC transmission based on phase-controlled commutation technology, the converter in flexible DC transmission is a voltage source converter (VSC). Its biggest feature is the use of turn-off devices (usually insulated gate bipolar transistors, IGBTs) and high-frequency modulation technology. At the same time, in order to ensure uniform voltage distribution, voltage-equalizing capacitors are generally configured in the IGBT power transistors. Therefore, the main requirement for current transformers is their speed; simply put, the faster the transmission speed, the better, and it must maintain its transmission accuracy during rapid response.

[0003] Internationally, DC current transformers are generally divided into DC current transformers and zero-flux DC current transformers. Optical DC current transformers are mainly used for optical DC current measurement in the main circuit, while zero-flux DC current transformers are mainly used in grounding terminals. In the past decade, domestically produced DC current transformers have mainly been shunt-type electrical DC current transformers. Shunt-type DC current transformers use a shunt to convert the measured DC current signal into a low-voltage signal according to a certain ratio. This signal is then converted into an optical signal by a converter and transmitted to the control room via optical fiber for measurement, protection, and control in DC transmission systems.

[0004] The shunt-type DC current transformer uses a shunt as its sensing element. Its output is a small voltage signal at the same potential, so it needs to be sampled locally at the high-voltage end. Its power supply is provided remotely by a laser located in the merging unit at the low potential end, supplying power to the remote module. Therefore, the remote module of the DC current transformer receives and processes the shunt's output signal, and its output is a serial digital optical signal. The acquisition unit's power supply is provided by the laser located in the merging unit in the control room.

[0005] Currently, flexible DC current transformers mainly employ purely optical principles. However, due to the high failure rate of optical sensors, the primary research and development direction for DC current transformers in China focuses on electrical principles, specifically shunts, to convert current into low-voltage signals. Since the rated output voltage of a shunt is typically 75mV, its resistance is only tens of microohms when the rated current is several thousand A. At this point, the stray inductance within the shunt cannot be ignored when transmitting high-frequency signals. Furthermore, flexible DC current transformers are affected by the voltage-equalizing capacitors, resulting in a much faster current rise and a significantly higher peak fault current compared to conventional DC. According to current national standards for DC transformers, the maximum fault current transmission rate for conventional DC is 6 times the rated current, while for flexible DC it is 15 times the rated current. Due to the lack of appropriate evaluation methods, it is impossible to determine whether its fault transmission performance meets the requirements.

[0006] In summary, the technical problems existing in the relevant technologies need to be improved. Summary of the Invention

[0007] The main objective of this application is to propose a method and related equipment for evaluating the transmission performance of current transformers under flexible DC faults. This method can evaluate the transmission performance of the current transformers without directly applying a large actual fault current, thus having high reliability.

[0008] To achieve the above objectives, one aspect of this application proposes a method for evaluating the transmission performance of a current transformer under flexible DC faults, the method comprising: Obtain the parameters of the flexible DC system and the shunt, and set the remote module of the current transformer to be evaluated to the working state. The continuous function of the flexible DC fault current is determined based on the parameters of the flexible DC system, and the continuous function of the shunt output small voltage is determined based on the continuous function of the flexible DC fault current and the shunt parameters. The small voltage analog signal is determined based on the small voltage continuous function output by the shunt, the small voltage analog signal is output to the remote module, and the digital signal of the sample current returned by the remote module based on the small voltage analog signal is received. The sample current sampling value sequence is determined based on the sample current digital signal, the evaluation synchronization parameters are determined based on the output process of the small voltage analog signal and the receiving process of the sample current digital signal, and the standard current sampling value sequence is determined based on the evaluation synchronization parameters and the flexible DC fault current continuous function. The performance evaluation result of the current transformer to be evaluated is determined based on the sample current sampling value sequence and the standard current sampling value sequence.

[0009] In some embodiments, setting the remote module of the current transformer to be evaluated to an operational state includes: The laser power module supplies energy to the remote module and obtains the communication status and power status values ​​returned by the remote module. The output of the laser power supply module is adjusted according to the communication status quantity and the power status quantity to put the remote module into working state.

[0010] In some embodiments, the flexible DC system parameters include initial load current, pre-fault capacitor voltage, equivalent parallel capacitance of the DC system, equivalent resistance of the fault loop, equivalent inductance of the fault loop, and rated current of the flexible DC system. Determining the continuous function of the flexible DC fault current based on the flexible DC system parameters includes: The steady-state current function before the fault occurs is determined based on the initial load current. The oscillating current function after the fault is determined based on the initial load current, the pre-fault capacitor voltage, the equivalent parallel capacitance of the DC system, the equivalent resistance of the fault circuit, and the equivalent inductance of the fault circuit. The switching time when the fault current value reaches a preset multiple of the rated current of the flexible DC system is determined based on the oscillating current function. The peak fault current is determined based on the switching time and the oscillation current function. The initial current before attenuation is determined based on the peak fault current and the preset initial attenuation ratio parameter. The decay current function is determined based on the initial current before decay and the preset decay time constant; The steady-state current function, the oscillating current function, and the decaying current function are combined based on the fault occurrence time and the switching time to obtain the flexible DC fault current continuous function.

[0011] In some embodiments, the shunt parameters include the shunt equivalent resistance and the shunt equivalent stray inductance, and determining the shunt output small voltage continuity function based on the flexible DC fault current continuity function and the shunt parameters includes: The continuous function of the rate of change of fault current is determined based on the continuous function of the flexible DC fault current. The continuous function of the shunt output small voltage is determined based on the continuous function of the flexible DC fault current, the continuous function of the fault current rate of change, the equivalent resistance of the shunt, and the equivalent stray inductance of the shunt.

[0012] In some embodiments, determining the small voltage analog signal based on the small voltage continuous function of the shunt output includes: The continuous function of the small voltage output of the shunt is discretized according to the preset digital-to-analog conversion sampling rate to obtain the small voltage digital sequence. The digital sequence of small voltages is converted into the analog signal of small voltages using a digital-to-analog converter module.

[0013] In some embodiments, determining the evaluation synchronization parameters based on the output process of the low-voltage analog signal and the reception process of the digital signal of the test sample current, and determining the standard current sampling value sequence based on the evaluation synchronization parameters and the flexible DC fault current continuous function, includes: Obtain the digital-to-analog conversion delay and output time of the small voltage analog signal; The processing time of the remote module in processing the low voltage analog signal and the reception time of the digital signal of the sample current are obtained. The digital-to-analog conversion delay, the output time, the processing time, and the receiving time are used as the evaluation synchronization parameters; The synchronous sampling time corresponding to the sample current sampling value sequence is determined based on the evaluation synchronization parameters. The standard current sampling value sequence is determined based on the synchronous sampling time and the flexible DC fault current continuity function.

[0014] In some embodiments, determining the transmission performance evaluation result of the current transformer to be evaluated based on the sample current sampling value sequence and the standard current sampling value sequence includes: The sample current sampling value sequence is compared with the standard current sampling value sequence to obtain the error current sampling value sequence; The maximum error current and the time of occurrence of the maximum error current are determined based on the error current sampling value sequence. The maximum peak error current, response time, and decay time error are determined based on the sample current sampling value sequence and the standard current sampling value sequence. The maximum error current, the occurrence time of the maximum error current, the maximum peak error current, the response time, and the decay time error are used as the evaluation results of the transmission performance.

[0015] To achieve the above objectives, another aspect of this application proposes a device for evaluating the transmission performance of a current transformer under flexible DC faults, the device comprising: The simulation parameter configuration module is used to obtain the parameters of the flexible DC system and the shunt, and to set the remote module of the current transformer to be evaluated to the working state. The simulation function determination module is used to determine the continuous function of the flexible DC fault current based on the parameters of the flexible DC system, and to determine the continuous function of the shunt output small voltage based on the continuous function of the flexible DC fault current and the shunt parameters. The low-voltage analog signal processing module is used to determine the low-voltage analog signal based on the low-voltage continuous function output by the shunt, output the low-voltage analog signal to the remote module, and receive the sample current digital signal returned by the remote module based on the low-voltage analog signal. The current sampling value sequence determination module is used to determine the sample current sampling value sequence based on the sample current digital signal, determine the evaluation synchronization parameters based on the output process of the small voltage analog signal and the receiving process of the sample current digital signal, and determine the standard current sampling value sequence based on the evaluation synchronization parameters and the flexible DC fault current continuous function. The transmission performance evaluation module is used to determine the transmission performance evaluation result of the current transformer to be evaluated based on the sample current sampling value sequence and the standard current sampling value sequence.

[0016] To achieve the above objectives, another aspect of this application provides an electronic device, which includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the methods described above.

[0017] To achieve the above objectives, another aspect of the embodiments of this application proposes a computer-readable storage medium storing a computer program that, when executed by a processor, implements the methods described above.

[0018] To achieve the above objectives, another aspect of the embodiments of this application proposes a computer program product, including a computer program that, when executed by a processor, implements the methods described above.

[0019] The embodiments of this application include at least the following beneficial effects: This application provides a method and related equipment for evaluating the transmission performance of a current transformer under flexible DC faults. This scheme determines the continuous function of the flexible DC fault current and the continuous function of the small voltage output of the shunt based on the parameters of the flexible DC system and the shunt parameters, enabling the test process to simulate the equivalent working condition of the flexible DC fault based on parametric simulation, without the need for an external large current source to form the test conditions; it determines the small voltage analog signal based on the continuous function of the small voltage output of the shunt, and inputs the small voltage analog signal to the remote module of the current transformer to be evaluated, so that the remote module can generate a digital signal of the test current based on the small voltage analog signal, thereby combining the sampling, processing and output process of the real remote module, improving the reliability of the evaluation results; it determines the standard current sampling value sequence based on the evaluation synchronization parameters, and then compares the test current sampling value sequence with the standard current sampling value sequence to complete the transmission performance evaluation, avoiding the influence of signal transmission time difference on the evaluation results, and further improving the reliability of the transmission performance evaluation. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the steps of a method for evaluating the transmission performance of a current transformer under a flexible DC fault, as provided in an embodiment of this application. Figure 2 This is a schematic diagram illustrating the working principle of a remote module in the prior art provided in this application embodiment; Figure 3 This is a schematic diagram of the working process of a DC current transformer testing system in the prior art provided in the embodiments of this application; Figure 4 This is a schematic diagram of the circuit principle of the equivalent circuit after a flexible DC short circuit provided in the embodiments of this application; Figure 5 This is a functional module division diagram of a method for evaluating the transmission performance of a current transformer under a flexible DC fault, provided in an embodiment of this application. Figure 6 This is a schematic diagram of the hardware module connection of a method for evaluating the transmission performance of a current transformer under a flexible DC fault, provided in an embodiment of this application. Figure 7 This is a schematic diagram of the structure of a current transformer transmission performance evaluation device under flexible DC fault provided in an embodiment of this application; Figure 8 This is a schematic diagram of the hardware structure of the electronic device provided in the embodiments of this application. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit it. In the following description, when referring to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with those of this application; they are merely examples of apparatuses and methods consistent with some aspects of the embodiments of this application as detailed in the appended claims.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0023] The concept of the present invention will now be explained in conjunction with the background art.

[0024] In existing technology, each remote module of a DC current transformer has two analog input terminals for receiving the output signal of the shunt, one fiber optic receiver for receiving laser signals, and one fiber optic transmitter for transmitting digital signals. (Refer to...) Figure 2 Taking the acquisition unit of NARI's DC current transformer as an example, its internal schematic diagram is as follows: Figure 2 As shown, the working principle of the remote module is that after the photovoltaic cell receives the laser power signal from the merging unit laser, the power control module forwards the photovoltaic cell voltage signal according to the voltage requirements of the AD circuit, CPU control circuit, and photoelectric conversion circuit. Therefore, there is an urgent need for an evaluation method at present. This method combines fault simulation of flexible DC and shunt characteristic simulation with sampling processing of the remote module to conduct individual tests on the remote module of the DC current transformer. Then, by comparing the results with the actual output of the primary current, the current transmission capability of the DC current transformer under flexible DC fault conditions can be obtained, providing technical support for the application of DC current transformers in flexible DC.

[0025] Currently, the testing of DC current transformers is mainly offline. A DC current is applied to the DC electronic transformer to perform an overall accuracy test. The workflow of this type of testing system is as follows: Figure 3 As shown, it has the following problems: 1) This offline testing method is a test behavior based on the application of primary current. It requires the application of an external DC current source. However, the current primary current source cannot apply a fault change of primary current of 15 times the rated current. It can only realize steady-state testing of rated current and step and high-frequency testing of 10% of rated current.

[0026] 2) It cannot truly reflect the flexible DC fault process, and its test results cannot prove that the DC current transformer can correctly transmit current under fault conditions.

[0027] 3) The testing cost is too high, requiring the configuration of different current sources. The testing results cannot be changed by adjusting parameters, and the testing process is simplistic.

[0028] Therefore, this application provides a method and related equipment for evaluating the transmission performance of a current transformer under a flexible DC fault. By performing fault simulation and shunt simulation on the flexible DC system and combining it with the remote module of the actual project to achieve analog-to-digital conversion, the transmission performance of the flexible DC transformer under the fault is evaluated through a combination of hardware and software.

[0029] This application provides a method for evaluating the transmission performance of a current transformer under flexible DC faults, relating to the field of information technology. This method can be applied to a terminal, a server, or software running on either a terminal or a server. In some embodiments, the terminal can be a smartphone, tablet, laptop, desktop computer, smart speaker, smartwatch, or vehicle terminal, but is not limited to these. The server can be configured as an independent physical server, a server cluster or distributed system composed of multiple physical servers, or a cloud server providing basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communication, middleware services, domain name services, security services, CDN, and big data and artificial intelligence platforms. The server can also be a node server in a blockchain network. The software can be an application implementing the method for evaluating the transmission performance of a current transformer under flexible DC faults, but is not limited to the above forms.

[0030] This application can be used in a wide variety of general-purpose or special-purpose computer system environments or configurations. Examples include: personal computers, server computers, handheld or portable devices, tablet devices, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable consumer electronics, network PCs, minicomputers, mainframe computers, and distributed computing environments including any of the above systems or devices. This application can be described in the general context of computer-executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform specific tasks or implement specific abstract data types. This application can also be practiced in distributed computing environments where tasks are performed by remote processing devices connected via a communication network. In distributed computing environments, program modules can reside in local and remote computer storage media, including storage devices.

[0031] Figure 1 This is an optional flowchart of a method for evaluating the transmission performance of a current transformer under a flexible DC fault, provided in an embodiment of this application. Figure 1 The method may include, but is not limited to, steps S101 to S105.

[0032] S101. Obtain the parameters of the flexible DC system and the shunt, and set the remote module of the current transformer to be evaluated to the working state. In some embodiments, setting the remote module of the current transformer to be evaluated to an operational state includes: S201. Provide energy to the remote module through the laser power module, and obtain the communication status and power status returned by the remote module. S202. Adjust the output of the laser power supply module according to the communication status and power status to put the remote module into working state.

[0033] S102. Determine the continuous function of the flexible DC fault current based on the parameters of the flexible DC system, and determine the continuous function of the shunt output small voltage based on the continuous function of the flexible DC fault current and the shunt parameters. In some embodiments, the flexible DC system parameters include the initial load current, the pre-fault capacitor voltage, the equivalent parallel capacitance of the DC system, the equivalent resistance of the fault loop, the equivalent inductance of the fault loop, and the rated current of the flexible DC system. Determining the continuous function of the flexible DC fault current based on the flexible DC system parameters includes: S301. Determine the steady-state current function before the fault occurs based on the initial load current; S302. Determine the oscillating current function after the fault occurs based on the initial load current, the capacitor voltage before the fault, the equivalent parallel capacitance of the DC system, the equivalent resistance of the fault circuit, and the equivalent inductance of the fault circuit. S303. Determine the switching time when the fault current value reaches a preset multiple of the rated current of the flexible DC system based on the oscillation current function. S304. Determine the peak fault current based on the switching time and the oscillation current function; S305. Determine the initial current before attenuation based on the peak fault current and the preset initial attenuation ratio parameter. S306. Determine the decay current function based on the initial current before decay and the preset decay time constant; S307. Based on the fault occurrence time and switching time, the steady-state current function, oscillating current function, and decaying current function are combined to obtain the flexible DC fault current continuous function.

[0034] In some embodiments, the shunt parameters include the shunt equivalent resistance and the shunt equivalent stray inductance. The shunt output small voltage continuity function is determined based on the flexible DC fault current continuity function and the shunt parameters, including: S401. Determine the continuous function of the rate of change of fault current based on the continuous function of flexible DC fault current. S402. Determine the continuous function of the shunt output small voltage based on the continuous function of the flexible DC fault current, the continuous function of the fault current change rate, the equivalent resistance of the shunt, and the equivalent stray inductance of the shunt.

[0035] Specifically, in this embodiment, it is first necessary to configure the flexible DC system parameters for simulating fault conditions and the shunt parameters for characterizing the shunt output characteristics, and then bring the remote module of the current transformer to be evaluated into a stable operating state. Existing detection methods relying on external primary current sources cannot realistically apply fault currents up to fifteen times the rated current, thus making it difficult to directly evaluate the current transformer's transmission capability under severe fault conditions. Therefore, this embodiment does not directly apply actual large fault currents, but instead first constructs the continuous change process of the flexible DC fault current and the corresponding output voltage of the shunt through parametric simulation.

[0036] Specifically, in this embodiment, the test system first needs to obtain flexible DC system parameters such as initial load current, pre-fault capacitor voltage, equivalent parallel capacitance of DC system, equivalent resistance of fault circuit, equivalent inductance of fault circuit, and rated current of flexible DC system.

[0037] Because the flexible DC fault process is exceptionally complex, it is difficult to construct the current changes during the fault process. Therefore, referring to... Figure 4 This embodiment simulates the transmission performance of a DC current sensor under the most severe condition by constructing a simplified equivalent circuit model of a flexible DC system when a fault occurs on the DC side, thereby evaluating the transmission performance of the current sensor under flexible DC fault conditions. (Refer to...) Figure 4 R0 is the equivalent load resistance, which can be determined based on the rated power E of the converter valve. n With rated voltage U n C is the equivalent parallel capacitance of the DC system. The capacitance of the DC line to ground is much smaller than the parallel capacitance and can be ignored. R and L are the equivalent resistance and equivalent inductance of the fault circuit, respectively. Essentially, it is an RLC oscillating circuit, so its oscillation output function can be obtained. Therefore, during a fault, it exhibits a second-order step response oscillation. Since the DC capacitance of the system is generally large, the oscillation process is an underdamped response process. Therefore, when a metallic short-circuit fault occurs in a flexible DC system under load, the flexible DC output current is:

[0038]

[0039] Among them, the above formula This is the oscillating current function after the fault occurs. This is the initial load current. This is the capacitor voltage before the fault. The equivalent resistance of the faulty circuit. C is the equivalent inductance of the fault circuit, and C is the equivalent parallel capacitance of the DC system. For attenuation coefficient, The frequency of the damped oscillation. This represents the oscillation coefficient. In the above formula, a positive sign indicates the rectifier-side current, and a negative sign indicates the inverter-side current.

[0040] The current will rapidly reach its peak value within milliseconds, with an amplitude several times or even tens of times the rated current. This patent is designed to test the transmission characteristics of a flexible DC current sensor, so its maximum fault current peak value is 15 times the rated current. That is, the IGBT is blocked when the current reaches 15 times the rated current. In this embodiment, this moment is defined as the switching moment, and the oscillating current function value corresponding to this switching moment is determined as the fault current peak value. At this time, the modular multilevel converter (MMC) bridge arm enters the uncontrolled rectification state, and the equivalent circuit is no longer a pure RLC discharge, but rather a stage where the AC system feeds current to the fault point through diodes. At this time, the DC side current will not return to zero, but will have a relatively long attenuation tail. If this tail current cannot be correctly transmitted, it is highly likely to cause false tripping of the DC protection. Therefore, the second segment of current is the DC attenuation current.

[0041] The above formula This is the decaying current function, at this time The initial current before attenuation is τ, which is usually 20-40% of the peak fault current, depending on the set initial attenuation ratio. τ is the attenuation time constant, which is generally between 0.2 and 15 ms.

[0042] In summary, by combining the fault occurrence time and the switching time, the steady-state current function, the oscillating current function, and the decaying current function can be combined to finally obtain the output formula of the flexible DC, which is a three-segment continuous function of the flexible DC fault current:

[0043]

[0044]

[0045] In this case, the fault occurrence time is set to t=0. The switching moment is the time it takes for the instantaneous value to oscillate to 15 times the rated current.

[0046] After obtaining the continuous function of the flexible DC fault current, this embodiment further determines the continuous function of the shunt output small voltage based on the shunt parameters. The shunt parameters include the shunt equivalent resistance and the shunt equivalent stray inductance. The shunt is an approximately non-inductive resistor; its steady-state voltage is approximately equal to the product of its resistance and current. However, during a flexible DC fault, the fault current changes rapidly, and the dynamic voltage corresponding to the shunt equivalent stray inductance cannot be ignored. Therefore, this embodiment determines the continuous function of the fault current rate of change based on the continuous function of the flexible DC fault current, and combines this with the shunt equivalent resistance and the shunt equivalent stray inductance to determine the continuous function of the shunt output small voltage, as shown in the following equation:

[0047] That is, the shunt output voltage is a continuous function of a small voltage. For fault current, Let be a continuous function of the rate of change of fault current. Substituting the aforementioned three-stage flexible DC fault current continuous function into the above equation, we can obtain the continuous function of the shunt output small voltage under flexible DC fault conditions:

[0048]

[0049]

[0050] The continuous function of the small voltage output of the shunt is used to characterize the small voltage change process of the shunt output to the remote module.

[0051] Furthermore, during the simulation process described above, the test system can be fiber optically connected to the remote module of the DC current transformer under evaluation. Energy is supplied to the remote module via a laser power supply module, and digital signals from the remote module are received via a digital receiver module. The output laser energy of the laser power supply module is controlled based on the communication and power supply self-test status signals of the remote DC current transformer to keep the remote module operational. The entire system is constantly under real-time laser power supply adjustment to prevent insufficient light source causing sampling distortion in the remote module due to changes in its sampling system, or to prevent rapid temperature rise and damage to the remote module due to prolonged over-power supply. Therefore, the subsequent performance evaluation of the transformer in response to flexible DC faults can be completed while the remote module is in a stable operating state.

[0052] It can be recognized that this embodiment can obtain the continuous function of flexible DC fault current and its corresponding continuous function of small voltage output of shunt without directly generating the actual large fault current, and ensure that the remote module is in a testable state, thereby providing a basis for applying an equivalent small voltage signal to the remote module and conducting transmission performance evaluation.

[0053] S103. Determine the small voltage analog signal based on the small voltage continuous function of the shunt output, output the small voltage analog signal to the remote module, and receive the sample current digital signal returned by the remote module based on the small voltage analog signal. In some embodiments, determining the small voltage analog signal based on the continuous function of the small voltage output of the shunt includes: S501. Discretize the continuous function of the small voltage output of the shunt according to the preset digital-to-analog conversion sampling rate to obtain the small voltage digital sequence. S502 converts a small voltage digital sequence into a small voltage analog signal through a digital-to-analog converter module.

[0054] S104. Determine the sample current sampling value sequence based on the sample current digital signal, determine the evaluation synchronization parameters based on the output process of the small voltage analog signal and the reception process of the sample current digital signal, and determine the standard current sampling value sequence based on the evaluation synchronization parameters and the flexible DC fault current continuous function. In some embodiments, the evaluation synchronization parameters are determined based on the output process of the low-voltage analog signal and the reception process of the digital signal of the test sample current, and the standard current sampling value sequence is determined based on the evaluation synchronization parameters and the flexible DC fault current continuity function, including: S601. Obtain the digital-to-analog conversion delay and output time of the small voltage analog signal; S602. Obtain the processing time of the remote module for processing the low voltage analog signal and the reception time of the digital signal of the sample current. S603, Use the digital-to-analog conversion delay, output time, processing time, and receiving time as evaluation synchronization parameters; S604. Determine the synchronous sampling time corresponding to the sample current sampling value sequence based on the evaluation synchronous parameters; S605. Determine the standard current sampling value sequence based on the synchronous sampling time and the continuous function of flexible DC fault current.

[0055] S105. Determine the performance evaluation result of the current transformer to be evaluated based on the sample current sampling value sequence and the standard current sampling value sequence.

[0056] In some embodiments, the performance evaluation result of the current transformer to be evaluated is determined based on the sample current sampling value sequence and the standard current sampling value sequence, including: S701. Compare the sample current sampling value sequence with the standard current sampling value sequence to obtain the error current sampling value sequence; S702. Determine the maximum error current and the time of occurrence of the maximum error current based on the error current sampling value sequence; S703. Determine the maximum peak error current, response time, and decay time error based on the sample current sampling value sequence and the standard current sampling value sequence. S704. The maximum error current, the time of occurrence of the maximum error current, the maximum peak error current, the response time, and the decay time error are used as the results of the transmission performance evaluation.

[0057] Specifically, in this embodiment, after obtaining the continuous function of the small voltage output of the shunt, the continuous function is further converted into a small voltage analog signal that can be actually input to the remote module. Since the continuous function of the small voltage output of the shunt is a continuous function that changes with time, and the digital-to-analog converter module in the actual test device can only output voltage point by point according to a certain sampling rate, the continuous function of the small voltage output of the shunt is first discretized according to the preset digital-to-analog conversion sampling rate to obtain a small voltage digital sequence; then the small voltage digital sequence is converted into a small voltage analog signal by the digital-to-analog converter module.

[0058] After obtaining the small voltage analog signal, the small voltage analog signal is output to the remote module of the current transformer to be evaluated, and the output time t1 and the time Δt1 spent on digital-to-analog conversion are recorded.

[0059] After receiving the low-voltage analog signal, the remote module samples, processes, and converts the input signal according to its own workflow to obtain the digital signal of the test sample current corresponding to the low-voltage analog signal. It then returns this digital signal to the test system, recording the reception time t2 of the received digital signal and the time t taken by the remote module to process the data. N .

[0060] Subsequently, the testing system, based on the mapping relationship between the digital signal and analog signal of the test sample current, converts the digital signal into a current value and forms a sequence of sampled test sample current values ​​X. sn [0,1,2,3,4,5……n], based on the aforementioned output time t1, the time Δt1 spent on digital-to-analog conversion, the time t2 spent receiving the digital signal, and the time t spent by the remote module processing the data. N The compensation time t for the final delay time data can be obtained. b =Δt1+(t2-t1)+t N Then, based on the arrival time and compensation time, the synchronous sampling time is obtained. Substituting this into the aforementioned flexible DC fault current continuity function yields the standard current sampling value sequence X, which is perfectly synchronized with the test sample data. bn [0,1,2,3,4,5……n].

[0061] After obtaining the sample current sampling value sequence and the standard current sampling value sequence, the two are compared, and the error current sampling value sequence X of the real-time error curve is calculated. σ[n] = Xs n [n]- X bn [n], thereby obtaining the true response error during the test process. To obtain quantitative data to evaluate whether the transmission characteristics of the DC current transformer under flexible DC faults can meet the control and protection requirements, this embodiment defines the following based on the above data: X σmax = MAX(X) σ [n]), corresponding to time t. σmax ; X smax =MAX(Xs) n [n]), corresponding to time t. smax ; X bmax =MAX(X bn [n]), corresponding to time t. bmax ; At the same time, for X sn The data [0,1,2,3,4,5……n] is processed, and the decay time constant τ1 is calculated based on its decay value (i.e., from I...). dc (Time to reach the 1 / e value).

[0062] Therefore, the final performance evaluation indicators for transmission are as follows: Maximum error current X σmax ; Maximum error current time t σmax ; Maximum peak error current X σ1max =X smax - X bmax ; Response time t x = t smax - t bmax 、; decay time error τ σ =τ1-τ.

[0063] The embodiments of the present invention will be further described below with reference to a specific example.

[0064] Reference Figure 5 , Figure 5This diagram illustrates the functional module division of a method for evaluating the transmission performance of a current transformer under flexible DC faults, as provided in an embodiment of the present invention. It comprises seven modules: a human-machine interaction module, a flexible DC simulation module, a shunt simulation module, a digital-to-analog converter module, a digital signal receiving module, a laser power supply module, and a fault current evaluation module. The human-machine interaction module is primarily responsible for configuring flexible DC fault parameters, configuring shunt parameters, and displaying feedback on evaluation results. The flexible DC simulation module simulates the current output during a flexible DC fault. The shunt simulation module simulates the conversion of the flexible DC fault current into a small voltage signal after passing through the shunt. The digital-to-analog converter module discretizes the output function of the small voltage signal and outputs it via an analog-to-digital converter chip. The digital signal receiving module receives fiber optic digital signals from a remote module. The laser power supply module provides power to the remote module by outputting optical signals. The fault current evaluation module performs real-time evaluation of the digital signals output by the remote module after synchronization.

[0065] Reference Figure 6 , Figure 6 This is a schematic diagram of the hardware module connection for a method to evaluate the transmission performance of a current transformer under flexible DC faults, provided in an embodiment of the present invention. It employs a ZYNQ dual-core CPU. The ZYNQ dual-core CPU consists of an FPGA and an ARM core. The FPGA, due to its excellent real-time characteristics, is responsible for external data acquisition and transmission, while the ARM core is responsible for data calculation, data generation, human-computer interaction, and program download and debugging. The ZYNQ is configured with peripheral chips and circuits to achieve external output and reception. The photoelectric conversion circuit receives the fiber optic digital signal from the acquisition unit, converts it into an electrical signal, and then sends it to the FPGA for signal processing. The DA1 conversion module converts the digital control signal of the laser power supply into an analog signal. The DA2 conversion module simulates the small voltage signal output by the primary sensor of the DC current transformer. The AD module converts the feedback voltage of the laser power supply module into a digital signal. The FPGA, photoelectric converter, and fiber optic serial port together constitute the digital signal receiving module. The FPGA and DA2 converter together constitute the digital-to-analog conversion module. The laser power supply module is configured separately and is adjusted in real time by the FPGA through DA1. The ARM core has built-in flexible DC fault simulation module, shunt simulation module, and fault current assessment module. The ARM core and LCD touch screen together constitute the human-machine interaction module.

[0066] It can be understood that this embodiment uses software simulation combined with physical construction of a flexible DC current transformer under fault conditions, and then tests to complete the evaluation of the transmission performance of the flexible DC current transformer under fault conditions. The application example adopts a portable design, which can significantly improve testing efficiency and quickly evaluate the performance of DC current transformers used in the field. A three-segment function is used to simulate the RLC oscillation circuit of the flexible DC current transformer under near-field metallic faults with load, and the time point of oscillation to 15 times the rated current is used as the state switching point to assess the response capability of the DC current transformer under the most severe condition. A separate laser power supply module is used in conjunction with the FPGA's digital signal receiver to control the output of the laser power supply in real time to achieve stable operation of the remote module and provide stable power conditions for the entire test. A continuous domain function differential equation is used to simulate the output of the shunt under fault conditions. In order to ensure the realism of the simulation, all simulations are implemented in the continuous domain function. The continuous domain function under flexible DC fault conditions is used as the evaluation standard. The actual arrival time of the discrete sampled values ​​of the remote module is used as the test time point on the continuous domain function. After delay compensation, the data is synchronized across the entire domain to generate a discrete standard sampled value sequence to improve the reliability of the evaluation.

[0067] Please see Figure 7 This application also provides a device for evaluating the transmission performance of a current transformer under a flexible DC fault, which can implement the above-mentioned method. The device includes: The simulation parameter configuration module is used to obtain the parameters of the flexible DC system and the shunt, and to set the remote module of the current transformer to be evaluated to the working state. The simulation function determination module is used to determine the continuous function of the flexible DC fault current based on the parameters of the flexible DC system, and to determine the continuous function of the shunt output small voltage based on the continuous function of the flexible DC fault current and the shunt parameters. The low-voltage analog signal processing module is used to determine the low-voltage analog signal based on the continuous function of the low-voltage output of the shunt, output the low-voltage analog signal to the remote module, and receive the digital signal of the test sample current returned by the remote module based on the low-voltage analog signal. The current sampling value sequence determination module is used to determine the current sampling value sequence of the test sample based on the digital signal of the test sample current, determine the evaluation synchronization parameters based on the output process of the small voltage analog signal and the receiving process of the digital signal of the test sample current, and determine the standard current sampling value sequence based on the evaluation synchronization parameters and the flexible DC fault current continuous function. The current transformer performance evaluation module is used to determine the current transformer performance evaluation result based on the sample current sampling value sequence and the standard current sampling value sequence.

[0068] It is understood that the content of the above method embodiments is applicable to the present device embodiments. The specific functions implemented by the present device embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0069] This application also provides an electronic device, which includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the above-described method. This electronic device can be any smart terminal, including tablet computers, in-vehicle computers, etc.

[0070] It is understood that the content of the above method embodiments is applicable to this device embodiment. The specific functions implemented by this device embodiment are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0071] Please see Figure 8 , Figure 8 The hardware structure of an electronic device according to another embodiment is illustrated. The electronic device includes: The processor 901 can be implemented using a general-purpose CPU (Central Processing Unit), microprocessor, application-specific integrated circuit (ASIC), or one or more integrated circuits, and is used to execute relevant programs to implement the technical solutions provided in the embodiments of this application. The memory 902 can be implemented as a read-only memory (ROM), static storage device, dynamic storage device, or random access memory (RAM). The memory 902 can store the operating system and other application programs. When the technical solutions provided in the embodiments of this specification are implemented through software or firmware, the relevant program code is stored in the memory 902 and is called and executed by the processor 901 using the methods described in the embodiments of this application. The input / output interface 903 is used to implement information input and output; The communication interface 904 is used to enable communication and interaction between this device and other devices. Communication can be achieved through wired means (such as USB, Ethernet cable, etc.) or wireless means (such as mobile network, WIFI, Bluetooth, etc.). Bus 905 transmits information between various components of the device (e.g., processor 901, memory 902, input / output interface 903, and communication interface 904); The processor 901, memory 902, input / output interface 903, and communication interface 904 are connected to each other within the device via bus 905.

[0072] This application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method.

[0073] It is understood that the content of the above method embodiments is applicable to this storage medium embodiment. The specific functions implemented in this storage medium embodiment are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those achieved in the above method embodiments.

[0074] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method.

[0075] It is understood that the content of the above method embodiments is applicable to the embodiments of this program product. The specific functions implemented by the embodiments of this program product are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0076] Memory, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs and non-transitory computer-executable programs. Furthermore, memory may include high-speed random access memory, and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, memory may optionally include memory remotely located relative to the processor, and these remote memories can be connected to the processor via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0077] This application provides a method and related equipment for evaluating the transfer performance of a current transformer under flexible DC faults. The method involves determining the continuous function of the flexible DC fault current and the continuous function of the shunt output small voltage based on the parameters of the flexible DC system and the shunt parameters. This allows the testing process to simulate the equivalent working condition of the flexible DC fault using parametric simulation, eliminating the need for an external high-current source. A small voltage analog signal is determined based on the shunt output small voltage continuous function and input to the remote module of the current transformer under evaluation. This enables the remote module to generate a digital signal of the test current based on the small voltage analog signal, allowing the evaluation process to incorporate the sampling, processing, and output processes of the actual remote module, thus improving the reliability of the evaluation results. Finally, a standard current sampling value sequence is determined based on the evaluation synchronization parameters, and the test current sampling value sequence is compared with the standard current sampling value sequence to complete the transfer performance evaluation. This avoids the influence of signal transmission time difference on the evaluation results, further improving the reliability of the transfer performance evaluation.

[0078] The embodiments described in this application are for the purpose of more clearly illustrating the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions provided by the embodiments of this application. As those skilled in the art will know, with the evolution of technology and the emergence of new application scenarios, the technical solutions provided by the embodiments of this application are also applicable to similar technical problems.

[0079] Those skilled in the art will understand that the technical solutions shown in the figures do not constitute a limitation on the embodiments of this application, and may include more or fewer steps than shown, or combine certain steps, or different steps.

[0080] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0081] Those skilled in the art will understand that all or some of the steps in the methods disclosed above, as well as the functional modules / units in the systems and devices, can be implemented as software, firmware, hardware, or suitable combinations thereof.

[0082] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0083] It should be understood that in this application, "at least one (item)" means one or more, and "more than" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0084] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of the units described above is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0085] The units described above as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0086] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0087] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes multiple instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing programs, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0088] The preferred embodiments of the present application have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims of the present application. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and substance of the embodiments of the present application shall be within the scope of the claims of the present application.

Claims

1. A method for evaluating the transmission performance of a current transformer under flexible DC faults, characterized in that, include: Obtain the parameters of the flexible DC system and the shunt, and set the remote module of the current transformer to be evaluated to the working state. The continuous function of the flexible DC fault current is determined based on the parameters of the flexible DC system, and the continuous function of the shunt output small voltage is determined based on the continuous function of the flexible DC fault current and the shunt parameters. The small voltage analog signal is determined based on the small voltage continuous function output by the shunt, the small voltage analog signal is output to the remote module, and the digital signal of the sample current returned by the remote module based on the small voltage analog signal is received. The sample current sampling value sequence is determined based on the sample current digital signal, the evaluation synchronization parameters are determined based on the output process of the small voltage analog signal and the receiving process of the sample current digital signal, and the standard current sampling value sequence is determined based on the evaluation synchronization parameters and the flexible DC fault current continuous function. The performance evaluation result of the current transformer to be evaluated is determined based on the sample current sampling value sequence and the standard current sampling value sequence.

2. The method for evaluating the transmission performance of a current transformer under a flexible DC fault according to claim 1, characterized in that, Setting the remote module of the current transformer to be evaluated to the working state includes: The laser power module supplies energy to the remote module and obtains the communication status and power status values ​​returned by the remote module. The output of the laser power supply module is adjusted according to the communication status quantity and the power status quantity to put the remote module into working state.

3. The method for evaluating the transmission performance of a current transformer under a flexible DC fault according to claim 1, characterized in that, The flexible DC system parameters include the initial load current, pre-fault capacitor voltage, equivalent parallel capacitance of the DC system, equivalent resistance of the fault loop, equivalent inductance of the fault loop, and rated current of the flexible DC system. Determining the continuous function of the flexible DC fault current based on the flexible DC system parameters includes: The steady-state current function before the fault occurs is determined based on the initial load current. The oscillating current function after the fault is determined based on the initial load current, the pre-fault capacitor voltage, the equivalent parallel capacitance of the DC system, the equivalent resistance of the fault circuit, and the equivalent inductance of the fault circuit. The switching time when the fault current value reaches a preset multiple of the rated current of the flexible DC system is determined based on the oscillating current function. The peak fault current is determined based on the switching time and the oscillation current function. The initial current before attenuation is determined based on the peak fault current and the preset initial attenuation ratio parameter. The decay current function is determined based on the initial current before decay and the preset decay time constant; The steady-state current function, the oscillating current function, and the decaying current function are combined based on the fault occurrence time and the switching time to obtain the flexible DC fault current continuous function.

4. The method for evaluating the transmission performance of a current transformer under a flexible DC fault according to claim 1, characterized in that, The shunt parameters include the shunt equivalent resistance and the shunt equivalent stray inductance. Determining the shunt output small voltage continuity function based on the flexible DC fault current continuity function and the shunt parameters includes: The continuous function of the rate of change of fault current is determined based on the continuous function of the flexible DC fault current. The continuous function of the shunt output small voltage is determined based on the continuous function of the flexible DC fault current, the continuous function of the fault current rate of change, the equivalent resistance of the shunt, and the equivalent stray inductance of the shunt.

5. The method for evaluating the transmission performance of a current transformer under a flexible DC fault according to claim 1, characterized in that, The step of determining the small voltage analog signal based on the continuous function of the small voltage output of the shunt includes: The continuous function of the small voltage output of the shunt is discretized according to the preset digital-to-analog conversion sampling rate to obtain the small voltage digital sequence. The digital sequence of small voltages is converted into the analog signal of small voltages using a digital-to-analog converter module.

6. The method for evaluating the transmission performance of a current transformer under a flexible DC fault according to claim 1, characterized in that, The process of determining evaluation synchronization parameters based on the output process of the low-voltage analog signal and the reception process of the digital signal of the test sample current, and determining the standard current sampling value sequence based on the evaluation synchronization parameters and the flexible DC fault current continuous function, includes: Obtain the digital-to-analog conversion delay and output time of the small voltage analog signal; The processing time of the remote module in processing the low voltage analog signal and the reception time of the digital signal of the sample current are obtained. The digital-to-analog conversion delay, the output time, the processing time, and the receiving time are used as the evaluation synchronization parameters; The synchronous sampling time corresponding to the sample current sampling value sequence is determined based on the evaluation synchronization parameters. The standard current sampling value sequence is determined based on the synchronous sampling time and the flexible DC fault current continuity function.

7. The method for evaluating the transmission performance of a current transformer under a flexible DC fault according to claim 1, characterized in that, The step of determining the transmission performance evaluation result of the current transformer to be evaluated based on the sample current sampling value sequence and the standard current sampling value sequence includes: The sample current sampling value sequence is compared with the standard current sampling value sequence to obtain the error current sampling value sequence; The maximum error current and the time of occurrence of the maximum error current are determined based on the error current sampling value sequence. The maximum peak error current, response time, and decay time error are determined based on the sample current sampling value sequence and the standard current sampling value sequence. The maximum error current, the occurrence time of the maximum error current, the maximum peak error current, the response time, and the decay time error are used as the evaluation results of the transmission performance.

8. A device for evaluating the transmission performance of a current transformer under flexible DC faults, characterized in that, The device includes: The simulation parameter configuration module is used to obtain the parameters of the flexible DC system and the shunt, and to set the remote module of the current transformer to be evaluated to the working state. The simulation function determination module is used to determine the continuous function of the flexible DC fault current based on the parameters of the flexible DC system, and to determine the continuous function of the shunt output small voltage based on the continuous function of the flexible DC fault current and the shunt parameters. The low-voltage analog signal processing module is used to determine the low-voltage analog signal based on the low-voltage continuous function output by the shunt, output the low-voltage analog signal to the remote module, and receive the sample current digital signal returned by the remote module based on the low-voltage analog signal. The current sampling value sequence determination module is used to determine the sample current sampling value sequence based on the sample current digital signal, determine the evaluation synchronization parameters based on the output process of the small voltage analog signal and the receiving process of the sample current digital signal, and determine the standard current sampling value sequence based on the evaluation synchronization parameters and the flexible DC fault current continuous function. The transmission performance evaluation module is used to determine the transmission performance evaluation result of the current transformer to be evaluated based on the sample current sampling value sequence and the standard current sampling value sequence.

9. An electronic device, characterized in that, The electronic device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the method according to any one of claims 1 to 7.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the method of any one of claims 1 to 7.

Images