Wireless synchronization-based direct-current voltage transformer frequency response test method and system

Abstract

The application discloses a DC voltage transformer frequency response test method and system based on wireless synchronization, and the method steps comprise the following steps: a test host and a wireless slave are configured, and the test host and the wireless slave are wirelessly synchronized; the test host collects standard signals output by a standard source, and the wireless slave collects optical fiber digital signals output by a measured DC voltage transformer; the test host detects a fundamental wave frequency of the standard signals and sends the standard signals to the wireless slave; the wireless slave adjusts a sampling frequency by interpolating the collected optical fiber digital signals according to the fundamental wave frequency; the test host performs spectrum calculation on the standard signals, sends harmonic numbers required to be tested to the wireless slave, and returns corresponding actual spectrum parameters to the test host; and the test host performs DC voltage transformer frequency response test according to the actual spectrum parameters. The application has the advantages of simple operation, low test cost, high test efficiency and precision, safety and reliability and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current (DC) power transmission systems, and in particular to a method and system for testing the frequency response of a DC voltage transformer based on wireless synchronization. Background Art

[0002] DC voltage transformers (DC voltage transformers) are crucial primary equipment in the construction and operation of DC transmission systems. They provide precise and reliable measurement information for DC control and protection systems. Their operational reliability and measurement accuracy are directly linked to the safe and stable operation of DC transmission systems. Currently, converter stations often experience slow DC control and protection operations due to the DC voltage transformer's long response time, leading to system failures. Furthermore, due to the coupling channel between AC and DC during the converter's commutation process, the DC voltage contains a large amount of high-frequency signals, necessitating on-site frequency response testing of the DC voltage transformers.

[0003] Currently, there are two main methods for testing the frequency response of DC electronic voltage transformers. One is the AC voltage open-loop test method, which applies an AC voltage signal to the DC voltage and then reads the voltage value output by the DC voltage transformer in the background. However, this type of open-loop test method has a limited test range and can only test the amplitude accuracy of the AC voltage, but cannot test the phase accuracy and delay accuracy of the AC voltage. It also has very high requirements for the output stability of the AC voltage source, resulting in high testing costs. The other method is the AC voltage closed-loop test method, which applies AC voltage signals of different frequencies to the DC voltage transformer. The DC electronic transformer tester then simultaneously receives the small voltage signal from the standard voltage divider and the digital test signal of the DC voltage transformer to complete the test. In this type of closed-loop test, since the merging unit is placed in the control room and the DC voltage source and standard are outdoors, a test optical fiber must be laid out in advance during the test to transmit the merging unit data to the tester. However, the location of the UHVDC converter station control room and the transformer is far away (usually hundreds of meters or even thousands of meters away). The workload of laying out the test optical fiber on site is very large, not only reducing the test complexity and efficiency, but also raising safety issues in on-site testing. Summary of the Invention

[0004] The technical problem to be solved by the present invention is: in response to the technical problems existing in the prior art, the present invention provides a DC voltage transformer frequency response testing method and system based on wireless synchronization, which is simple to operate, low in testing cost, high in testing efficiency and accuracy, strong in flexibility, and safe and reliable.

[0005] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0006] A method for testing the frequency response of a DC voltage transformer based on wireless synchronization, comprising the following steps:

[0007] Configure a test host and a wireless slave, and wirelessly synchronize the test host and the wireless slave;

[0008] The test host collects the standard signal output by the standard source using a variable frequency sampling method, and the wireless slave uses a digital sampling method to collect the optical fiber digital signal output by the DC voltage transformer under test;

[0009] The test host detects the fundamental frequency of the standard signal and sends the detected fundamental frequency to the wireless slave;

[0010] After receiving the fundamental frequency, the wireless sub-unit interpolates the collected optical fiber digital signal according to the fundamental frequency to adjust the sampling frequency;

[0011] The test host calculates the spectrum of the standard signal and sends the spectrum harmonics required for testing in the calculation result to the wireless slave;

[0012] The wireless handset calculates the corresponding actual spectrum parameters based on the frequency harmonics of the spectrum to be tested and returns them to the test host;

[0013] The test host performs a DC voltage transformer frequency response test based on the actual spectrum parameters returned by the wireless slave.

[0014] Furthermore, the wireless synchronization of the test host and the wireless slave includes:

[0015] Before the test begins, the test host and the wireless slave are connected using optical fiber, and time synchronization is performed between the test host and the wireless slave via optical fiber pulses;

[0016] After time synchronization, the wireless slave is controlled to adjust its own crystal oscillator to follow the crystal oscillator beat of the test host and enter the punctual synchronization state;

[0017] After entering the punctual synchronization state, move the wireless slave to the acquisition and merging unit in the main control room and maintain the punctual synchronization state.

[0018] Furthermore, after the wireless synchronization of the test host and the wireless sub-machine, the method further includes performing any one or more of sample filtering, frequency correction and delay correction between the test host and the wireless sub-machine to achieve wireless synchronization correction. The sample filtering is used to use the synchronization message as sample data and filter out sample data whose deviation value of two adjacent sample data exceeds a preset maximum deviation value. The frequency correction is used to adjust the frequency deviation of the clock between the test host and the wireless sub-machine. The delay correction is used to correct the clock delay between the test host and the wireless sub-machine.

[0019] Furthermore, frequency correction of the test host and the wireless slave includes: the test host sending a synchronization message to the wireless slave at a fixed frequency, calculating a frequency correction coefficient based on the time between two synchronization message transmissions by the test host and the time between two synchronization message receptions by the wireless slave, and the wireless slave using the frequency correction coefficient to perform discrete point correction on its own clock frequency. The calculation expression of the frequency correction coefficient is:

[0020]

[0021] in, C n is the current sub-frequency correction coefficient, T n ' is the arrival time of the message currently received by the wireless handset, T n-1 ' is the arrival time of the message received by the wireless handset last time, T n The time when the test host sends the current message. T n-1 The time when the test host last sent a message.

[0022] Furthermore, the test host collects the standard signal output by the standard source in a variable frequency sampling manner, including: using the hardware clock of the FPGA inside the test host to control the sampling trigger moment of the AD sampling module according to the calculated fundamental frequency, so as to adjust the sampling interval period of the AD sampling module to realize variable frequency sampling.

[0023] Furthermore, the wireless sub-unit interpolates the collected optical fiber digital signal according to the fundamental frequency using a Lagrange quadratic interpolation method. The collected optical fiber digital signal is expressed as y=f(x). The signal obtained after interpolation using the Lagrange quadratic interpolation method is:

[0024]

[0025] in, 、 、 are the data points at time k-1, k and k+1 respectively, 、 、 Respectively in 、 、 Function value at the point.

[0026] Furthermore, the test host uses DFT calculation to obtain the fundamental wave and amplitude and phase of each harmonic of the standard signal at time 0, and sends the harmonic order required for testing to the wireless slave. The wireless slave uses frequency tracking to calculate the actual frequency of the DC voltage transformer under test.

[0027] Furthermore, after the test, the phase error of the frequency response of the DC voltage transformer is expressed by time, and the frequency response time of each harmonic is obtained as :

[0028]

[0029] in, 、 are the phases of the standard signal and the DC voltage transformer under test, 、 are the fundamental frequencies of the standard signal and the DC voltage transformer under test respectively.

[0030] A DC voltage transformer frequency response test system based on wireless synchronization includes a standard signal source for generating a standard signal and providing it to a DC voltage transformer under test; and a test host and a wireless slave. The test host is wirelessly connected to the wireless slave and configured for time synchronization. The test host is also connected to the standard signal source to collect the standard signal output by the standard signal source, perform fundamental frequency detection and spectrum calculation, send the detected fundamental frequency and the harmonic order to be tested to the wireless slave, and perform a DC voltage transformer frequency response test based on actual spectrum parameters returned by the test host. The wireless slave is also connected to the DC voltage transformer under test to collect the optical fiber digital signal output by the DC voltage transformer under test, adjust the sampling frequency based on the received fundamental frequency, perform spectrum calculation based on the received harmonic order, and provide the calculated spectrum parameters as synchronization parameters to the test host.

[0031] Furthermore, the standard signal source includes a large voltage generator and a voltage divider connected to each other, wherein the large voltage generator is used to generate a large voltage signal of arbitrary waveform and provide it to the DC voltage transformer under test and the voltage divider respectively, and the voltage divider is used to divide the large voltage signal to generate a small voltage signal as a standard signal.

[0032] Compared with the prior art, the advantages of the present invention are:

[0033] 1. The present invention configures a test host and a wireless slave and uses LoRa wireless transmission to implement a DC voltage transformer frequency response test. This can solve the problem of needing to arrange long-distance test optical fibers during DC voltage transformer frequency response testing, reduce test costs, and improve test efficiency.

[0034] 2. The present invention uses a variable frequency sampling method for the test host and an interpolation digital sampling method for the wireless slave. The test host tracks and measures the frequency of the standard source and sends the fundamental frequency to the wireless slave. The wireless slave uses interpolation to adjust the frequency based on the synchronization time and the fundamental frequency value sent by the test host. This ensures that the test host and wireless slave are time synchronized, ensuring that the test results are not affected by the randomness of the crystal oscillators of the test host and wireless slave, as well as the sampling time, further improving test accuracy.

[0035] 3. The present invention is based on wireless transmission. The test host interacts with the slave machine with the spectrum parameters to be tested according to the spectrum calculation results. Only the frequency and harmonic number need to be transmitted between the test host and the wireless slave machine, and there is no need to transmit the complete harmonic signal. This can greatly reduce the amount of LORA transmission data, reduce communication time, and thus improve test efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the structure and principle of the DC voltage transformer frequency response test system based on wireless synchronization in this embodiment.

[0037] Figure 2 This is a schematic diagram of the implementation flow of the wireless synchronous DC voltage transformer frequency response test in this embodiment.

[0038] Figure 3 FIG. 2 is a schematic diagram of the principle of frequency correction in this embodiment.

[0039] Figure 4 Schematic diagram of the phasor corresponding to the sampling value in this embodiment. DETAILED DESCRIPTION

[0040] The present invention will be further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the scope of protection of the present invention is not limited thereby.

[0041] The core of the present invention is to configure a test host and a wireless slave, and respectively collect a standard signal and a signal of a DC voltage transformer under test by the test host and the wireless slave, thereby implementing a DC voltage transformer frequency response test based on a master-slave mode. The test operation is simple and there is no need to arrange test optical fibers on site. At the same time, considering that real-time sampling values ​​cannot be transmitted under LORA low-speed transmission, and different sampling systems can affect the sampling accuracy of the waveform, the present invention synchronizes the test host and the wireless slave in time. The test host adopts a variable frequency sampling mode and the wireless slave adopts an interpolation digital sampling mode. The wireless slave adopts an interpolation mode to implement frequency adjustment based on the fundamental frequency value sent by the test host at the synchronization moment, thereby ensuring synchronization between the test host and the wireless slave. The master and slave systems calculate the spectrum at the same frequency and at the same time, ensuring that the test results are not affected by the crystal oscillators of the test host and the wireless slave and the randomness of the sampling time. Therefore, the test accuracy can be greatly improved while ensuring test efficiency, and the DC voltage transformer frequency response test can be implemented quickly and accurately.

[0042] To implement the DC voltage transformer frequency response test, this embodiment constructs the following Figure 1 The DC voltage transformer frequency response test system shown here includes a standard signal source for generating a standard signal and providing it to the DC voltage transformer under test, and also includes: a test host and a wireless slave. The test host and the wireless slave are wirelessly connected and configured for time synchronization. The test host is also connected to the standard signal source to collect the standard signal output by the standard signal source, then detect the fundamental frequency and calculate the spectrum. The detected fundamental frequency and the number of harmonics to be tested are sent to the wireless slave, and the DC voltage transformer frequency response test is performed based on the actual spectrum parameters returned by the test host. The wireless slave is also connected to the DC voltage transformer under test to collect the optical fiber digital signal output by the DC voltage transformer under test, adjust the sampling frequency based on the received fundamental frequency, and perform spectrum calculation based on the received harmonic number. The calculated spectrum parameters are provided to the test host as synchronization parameters.

[0043] In this embodiment, the standard signal source specifically includes a large voltage generator and a voltage divider connected to each other. The large voltage generator is used to generate a large voltage signal of arbitrary waveform and provide it to the DC voltage transformer under test and the voltage divider, respectively. The voltage divider is used to divide the large voltage signal to generate a small voltage signal as the standard signal. It is understood that the standard signal source can also be implemented using other types of structures to provide the required standard signal.

[0044] The system of this embodiment utilizes LORA wireless transmission to transmit data between the master and slave devices, resolving the need for long-distance test fiber optic cables during DC voltage transformer frequency response testing, reducing testing costs and improving test efficiency. Utilizing wireless synchronization based on LORA communication to allow the master and slave devices to perform synchronous calculations can address issues such as low LORA signal transmission bandwidth. The test host communicates the required test spectrum parameters with the slave device based on the spectrum calculation results, reducing the amount of LORA transmission data and communication time, thereby further improving test efficiency. Furthermore, the test host uses a standard source frequency to track and measure the frequency, then transmits the baseband frequency to the wireless slave device. The wireless slave device then performs secondary interpolation of the digital signal of the DC voltage transformer under test according to the baseband frequency of the standard signal before performing spectrum calculation, further improving the overall accuracy of the test.

[0045] In a specific application embodiment, after constructing the aforementioned DC voltage transformer frequency response test system, the test host and wireless slave first synchronize via optical fiber, then unplug the synchronization fiber. The wireless slave synchronizes and keeps time, and then moves the wireless slave to a remote location for wireless synchronization correction. The test host collects a small analog voltage signal from a standard voltage divider and measures its frequency. The fundamental frequency is then transmitted to the wireless slave via LoRa. The test host adjusts the sampling frequency, and the wireless slave adjusts the sampling frequency through quadratic interpolation. After synchronization, the wireless slave performs spectrum calculation according to the host's synchronization time. After calculation, the test host transmits the frequency number to be tested to the wireless slave, which then transmits the actual frequency, amplitude, and phase of the corresponding frequency to the test host. The test host then completes the DC voltage transformer frequency response test based on the synchronized amplitude and phase of the host and slave.

[0046] like Figure 2 As shown, the detailed steps of the wireless synchronization-based DC voltage transformer frequency response test method of this embodiment include:

[0047] Step S01: Configure a test host and a wireless slave, and wirelessly synchronize the test host and the wireless slave.

[0048] Specifically, first follow the Figure 1 The illustrated configuration involves a test host and a wireless slave. The host and slave are wirelessly connected, connected to a standard voltage divider, and connected to the DC voltage transformer under test. The host acts as the master, and the slave acts as the slave. The two devices are then wirelessly synchronized to perform a DC voltage transformer frequency response test using a master-slave control scheme.

[0049] As an optional implementation, wireless synchronization between the test host and the wireless slave may be performed using the following steps:

[0050] Step S101. Wired synchronization between the master and slave: Before the test begins, the test master and the wireless slave are connected via optical fiber. Time synchronization is achieved between the master and the wireless slave via optical fiber pulses. After time synchronization, the wireless slave adjusts its crystal oscillator to match the test master's crystal oscillator rhythm, achieving punctual synchronization.

[0051] Specifically, before the test begins, the test host and the wireless slave can be placed together. After connecting them through optical fiber, the optical fiber pulse synchronization method is used to achieve time synchronization between the host and the slave. That is, the test host and the wireless slave are synchronized by transmitting optical fiber pulses. After synchronization, the crystal oscillator error between the test host and the wireless slave is calculated. According to the crystal oscillator error, the wireless slave adjusts its own crystal oscillator to follow the crystal oscillator beat of the host and enters the time synchronization state.

[0052] Step S102: After entering the time synchronization state, the wireless handset is moved to the acquisition and merging unit in the main control room and the time synchronization state is maintained.

[0053] Specifically, when the wireless slave enters the timed synchronization state, the synchronization optical fiber can be unplugged and the wireless slave can be moved to the acquisition and merging unit in the main control room so that the signal of the DC voltage transformer under test can be collected later. At this time, timed synchronization is used to keep the test host and the wireless slave in a synchronized state.

[0054] Preferably, the synchronization timing accuracy between the test host and the wireless slave can be configured to reach 4us / 10min to ensure the accuracy of subsequent tests.

[0055] As an optional implementation, wireless synchronization between the test host and the wireless slave also includes performing sample filtering, frequency correction, and delay correction between the two devices to achieve wireless synchronization correction and further improve synchronization accuracy. Sample filtering uses synchronization messages as sample data and filters out samples where the deviation between two adjacent sample data exceeds a preset maximum deviation. Frequency correction adjusts the frequency deviation between the test host and the wireless slave. Delay correction corrects the clock delay between the test host and the wireless slave.

[0056] Optionally, when performing sample filtering on the synchronization message, based on the mutation limit of stable data transmission, the two adjacent sample data T n and T n+1 If the actual sample data deviation exceeds the maximum deviation, it indicates that interference has occurred. The sample data is discarded and replaced with the previous data. If it is less than the maximum deviation, the sample data is considered normal.

[0057] Optionally, frequency correction between the test host and the wireless slave includes: the test host sending a synchronization message to the wireless slave at a fixed frequency; calculating a frequency correction coefficient based on the time between two synchronization message transmissions by the test host and the time between two synchronization message receptions by the wireless slave; and the wireless slave using the frequency correction coefficient to perform discrete point corrections on its own clock frequency to ensure frequency synchronization between the host and the slave. To further prevent overshoot and oscillation, smoothing can be employed.

[0058] Preferably, the frequency correction coefficient can be calculated as follows:

[0059] (1)

[0060] in, C n is the current sub-frequency correction coefficient, T n ' is the arrival time of the message currently received by the wireless handset, T n-1 ' is the arrival time of the message received by the wireless handset last time, T n The time when the test host sends the current message. T n-1 The time when the test host last sent a message.

[0061] Furthermore, the initial frequency deviation of the master and slave clocks can be adjusted by measuring the average path delay, and then the frequency correction can be performed by combining the above method of calculating the frequency correction coefficient, such as Figure 3 As shown, the master clock of the test host sends synchronization messages to the slave clock at a fixed frequency. The slave clock of the wireless slave records the corrected arrival message frequency and uses the frequency correction coefficient to perform discrete point correction on its own clock frequency.

[0062] Optionally, delay correction can be performed by using synchronization messages and delay request messages to perform time correction, and the master-slave clock loop delay between the test host and the wireless slave is obtained to obtain the measured delay. If the measured delay is greater than the average path time, the measured value may contain message transmission delay jitter, and the value is not used to correct the slave clock delay; otherwise, the measured delay is considered valid, and the slave clock of the wireless slave eliminates the delay difference with the master clock of the test host through multiple transmission delays. By repeatedly sending a message to form a master-slave message loop, a more accurate average path delay can be obtained to achieve delay correction.

[0063] Step 2: The test host collects the standard signal output by the standard source using a variable frequency sampling method, and the wireless slave uses a digital sampling method to collect the optical fiber digital signal output by the DC voltage transformer under test.

[0064] Specifically, after the test host and the wireless slave enter the synchronization state, the test host and the wireless slave independently perform data acquisition. The test host acquires the analog low-voltage signal of the standard source and adopts a variable-frequency sampling method, while the wireless slave adopts a digital sampling method to acquire the optical fiber digital signal from the DC voltage transformer.

[0065] Optionally, a hardware frequency conversion sampling method is adopted during the acquisition process of the test host. The AD sampling module of the internal FPGA of the test host performs sampling. At the same time, the sampling trigger moment of the AD sampling module is controlled by the FPGA hardware clock according to the fundamental frequency calculated by the test host to adjust the sampling interval of the AD sampling module. That is, variable frequency sampling is achieved by adjusting the sampling trigger time interval of the AD chip, which can ensure synchronization with the wireless sub-machine, thereby ensuring the measurement accuracy of the standard signal harmonics.

[0066] Step 3: The test host detects the fundamental frequency of the standard signal and sends the detected fundamental frequency to the wireless slave.

[0067] When tracking the fundamental frequency of the standard source signal, assume that the sampled voltage signal is as follows:

[0068] (2)

[0069] The signal is sampled at a fixed sampling rate, and the sampling frequency is set to , the obtained sampling sequence is: , , , ..., using the phasor method for analysis, let the phasors corresponding to the sampling sequence be: , , , ..., assuming that its phasor distribution is as follows Figure 4 As shown. Among them, 2 is the angle between the phasors, 2 = , =1 / .

[0070] From the phasor diagram we can get:

[0071] + + + = (3)

[0072] Then we get the following formula:

[0073] = = 2cos2 (4)

[0074] =cos2 =cos( )= cos( )(5)

[0075] Assume that the above result (phase shift caused by actual frequency) is ,but = = cos( ), we can get the fundamental frequency of the system:

[0076]

[0077] Optionally, when sampling the standard signal, the test host uses its own crystal oscillator as the reference 0 point and samples the standard signal according to the frequency after frequency measurement. f After tracking and calculating the fundamental frequency of the system in real time, the hardware clock of the FPGA inside the host is used to control the sampling trigger moment of AD, so as to adjust the sampling interval of AD and correct the sampling rate of host AD in real time. x (i) is a discrete sampling sequence, i=0 is the GPS synchronization moment. Then, DFT is used to perform discrete Fourier integration to obtain the fundamental wave and the amplitude and phase of each harmonic of the standard signal at time 0, that is:

[0078] (6)

[0079] (7)

[0080] Where N is the total number of samples in the time window, 、 are the real and imaginary parts of the standard source signal respectively.

[0081] According to the above method, the amplitude and phase of each harmonic of the standard signal source can be obtained, and the harmonic order required for testing can be transmitted to the wireless slave.

[0082] Step 4: After receiving the fundamental frequency, the wireless slave interpolates the collected optical fiber digital signal according to the fundamental frequency to adjust the sampling frequency.

[0083] Specifically, the signal from the DC voltage transformer under test is first collected by the DC electronic transformer's acquisition unit, and then the wireless slave performs digital sampling of the signal. While the wireless slave is sampling the DC voltage transformer's signal, the test host sends the frequency to the wireless slave via LoRa wireless communication. After receiving the host's frequency signal, the wireless slave uses the synchronization signal as a reference zero point. Because the DC voltage transformer under test is sampled by the acquisition unit of the DC electronic transformer, the sampling rate of the acquisition unit is fixed and cannot be adjusted. Different sampling rates in different systems can affect sampling accuracy. This embodiment achieves frequency adjustment by interpolating the digital signal collected by the wireless slave to obtain discrete samples of the digital signal at frequency f. Subsequently, a DFT Fourier integral is performed to obtain the fundamental wave and the amplitude and phase of each harmonic of the standard source signal at time zero. Frequency tracking is then used to calculate the actual frequency of the DC voltage transformer under test. Specifically, the wireless slave obtains the sampling frequency of the DC voltage transformer under test by tracking the standard source frequency of the test host. The wireless slave then obtains a new sampling sequence by performing secondary interpolation on the collected fiber-optic digital signal based on the sampling rate of the DC voltage transformer under test.

[0084] As an optional implementation, the wireless sub-unit can use Lagrange quadratic interpolation to interpolate the collected optical fiber digital signal based on the fundamental frequency. Lagrange quadratic interpolation constructs a polynomial from a set of known data points, and the polynomial takes the same value at all given data points. For example, the collected optical fiber digital signal is represented as y=f(x). It is known that the function y=f(x) at point x k-1 ,x k ,x k+1 The function value y on k-1 =f(x k-1 ),y k =f(x k ), y k+1 =f(x k+1 ), get a polynomial P2(x) of degree not more than two, so that it satisfies P2(x k-1 )=y k-1 ,P2(x k )=y k ,P2(x k+1 )=y k+1， Finally, the signal obtained after interpolation using the Lagrange quadratic interpolation method is:

[0085] (8)

[0086] in, 、 、 are the data points at time k-1, k and k+1 respectively, 、 、 Respectively in 、 、 Function value at the point.

[0087] Step 5: The test host calculates the spectrum of the standard signal and sends the spectrum harmonics required for testing in the calculation result to the wireless slave.

[0088] Specifically, the test host uses DFT calculation to obtain the fundamental wave and amplitude and phase of each harmonic of the standard signal at time 0, and sends the required harmonic order to the wireless slave. The wireless slave then uses frequency tracking to calculate the actual frequency of the DC voltage transformer under test.

[0089] Step 6: The wireless handset calculates the corresponding actual spectrum parameters according to the frequency harmonics of the spectrum to be tested and returns them to the test host.

[0090] Since LORA is a low-speed transmission method, it cannot transmit actual sampling values, nor can it send all harmonic signals to the test host. This embodiment uses data exchange between the master and slave devices and calculates the corresponding actual spectrum parameters using the required test spectrum harmonic order. Only the fundamental frequency and harmonic order need to be transmitted between the master and slave devices, without the need to transmit the complete harmonic signal. This can solve the problem of long-distance test fiber layout when testing the frequency response of DC voltage transformers, reduce testing costs, and also reduce the amount of LORA transmission data, shorten communication time, and effectively improve test efficiency.

[0091] Specifically, spectrum parameters include amplitude, phase, and frequency. The test host sends the harmonic order of the spectrum to be tested to the wireless slave based on the harmonic spectrum distribution of the standard signal source. After receiving the test harmonic order from the host, the wireless slave sends the actual frequency, amplitude, and phase of the corresponding harmonic to the test host. The test host then obtains the synchronized standard signal and the amplitude of the corresponding harmonic order (U b 、U s ) and phase (φ b 、φ s ).

[0092] Step 7: The test host performs a DC voltage transformer frequency response test based on the actual spectrum parameters returned by the wireless slave.

[0093] After receiving the actual spectrum parameters such as amplitude, phase and frequency transmitted by the wireless slave, the test host performs the DC voltage transformer frequency response test based on the actual spectrum parameters to complete the test process.

[0094] After the test is completed, the frequency error can be expressed as:

[0095] (9)

[0096] in, 、 are the fundamental frequencies of the standard signal and the DC voltage transformer under test respectively.

[0097] The amplitude error can be expressed as:

[0098] (10)

[0099] The phase error of the frequency response of the DC voltage transformer is expressed in time, so the frequency response time of each harmonic is :

[0100] (11)

[0101] in, 、 are the phases of the standard signal and the DC voltage transformer under test respectively.

[0102] By using the delay to express the phase and establishing a unified response model for each frequency spectrum, the frequency response characteristics of the DC voltage transformer can be accurately analyzed.

[0103] The present invention realizes the frequency response test of the DC voltage transformer by utilizing the LORA wireless transmission mode, which can avoid the layout of test optical fiber and reduce the test cost. The wireless data transmission channel is used for synchronous signal transmission, which can solve the synchronization problem of wireless transmission in the converter station. At the same time, the test host interacts with the slave machine through spectrum calculation to calculate the frequency and harmonic number to be tested, which can also reduce the amount of LORA transmission data, shorten the communication time, improve the test efficiency, and realize fast and accurate frequency response test of the DC voltage transformer.

[0104] Those skilled in the art will appreciate that the above-mentioned embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application may take the form of a computer program product implemented on one or more computer-readable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of processes and / or boxes in the flowchart and / or block diagram, may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 These computer program instructions can also be stored in a computer-readable memory that can guide a computer or other programmable data processing device to work in a specific way, so that the instructions stored in the computer-readable memory produce a product including the instruction device, which implements the function specified in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0105] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed above with reference to the preferred embodiment, it is not intended to limit the present invention. Therefore, any simple modifications, equivalent variations, and modifications to the above embodiment that do not depart from the technical solution of the present invention and are based on the technical essence of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for testing the frequency response of a DC voltage transformer based on wireless synchronization, characterized in that the steps include: Configure a test host and a wireless slave, and wirelessly synchronize the test host and the wireless slave; The test host collects the standard signal output by the standard source using a variable frequency sampling method, and the wireless slave uses a digital sampling method to collect the optical fiber digital signal output by the DC voltage transformer under test; The test host detects the fundamental frequency of the standard signal and sends the detected fundamental frequency to the wireless slave; After receiving the fundamental frequency, the wireless sub-unit interpolates the collected optical fiber digital signal according to the fundamental frequency to adjust the sampling frequency; The test host calculates the spectrum of the standard signal and sends the spectrum harmonics required for testing in the calculation result to the wireless slave; The wireless handset calculates the corresponding actual spectrum parameters based on the frequency harmonics of the spectrum to be tested and returns them to the test host; The test host performs a DC voltage transformer frequency response test based on the actual spectrum parameters returned by the wireless slave.

2. The method for testing the frequency response of a DC voltage transformer based on wireless synchronization according to claim 1, characterized in that: The wireless synchronization of the test host and the wireless slave comprises: Before the test begins, the test host and the wireless slave are connected using optical fiber, and time synchronization is performed between the test host and the wireless slave via optical fiber pulses; After time synchronization, the wireless slave is controlled to adjust its own crystal oscillator to follow the crystal oscillator beat of the test host and enter the punctual synchronization state; After entering the punctual synchronization state, move the wireless slave to the acquisition and merging unit in the main control room and maintain the punctual synchronization state.

3. The method for testing the frequency response of a DC voltage transformer based on wireless synchronization according to claim 1, characterized in that: After the wireless synchronization of the test host and the wireless slave, the method further includes performing any one or more of sample filtering, frequency correction and delay correction between the test host and the wireless slave to achieve wireless synchronization correction. The sample filtering is used to use the synchronization message as sample data and filter out sample data whose deviation value of two adjacent sample data exceeds a preset maximum deviation value. The frequency correction is used to adjust the frequency deviation of the clock between the test host and the wireless slave. The delay correction is used to correct the clock delay between the test host and the wireless slave.

4. The method for testing the frequency response of a DC voltage transformer based on wireless synchronization according to claim 3, characterized in that: Frequency correction of the test host and the wireless slave includes: the test host sends a synchronization message to the wireless slave at a fixed frequency, calculates a frequency correction coefficient based on the time between two synchronization message transmissions by the test host and the time between two synchronization message receptions by the wireless slave, and the wireless slave uses the frequency correction coefficient to perform discrete point correction on its own clock frequency. The calculation expression of the frequency correction coefficient is: in, C n is the current sub-frequency correction coefficient, T n ' is the arrival time of the message currently received by the wireless handset, T n-1 ' is the arrival time of the message received by the wireless handset last time, T n The time when the test host sends the current message. T n-1 The time when the test host last sent a message.

5. The method for testing the frequency response of a DC voltage transformer based on wireless synchronization according to claim 1, characterized in that: The test host collects the standard signal output by the standard source in a variable frequency sampling manner, including: using the hardware clock of the FPGA inside the test host to control the sampling trigger moment of the AD sampling module according to the calculated fundamental frequency, so as to adjust the sampling interval period of the AD sampling module to realize variable frequency sampling.

6. The method for testing the frequency response of a DC voltage transformer based on wireless synchronization according to any one of claims 1 to 5, characterized in that: The wireless sub-unit interpolates the collected optical fiber digital signal according to the fundamental frequency using the Lagrange quadratic interpolation method. The collected optical fiber digital signal is expressed as y=f(x). The signal obtained after interpolation using the Lagrange quadratic interpolation method is: in, 、 、 are the data points at time k-1, k and k+1 respectively, 、 、 Respectively in 、 、 Function value at the point.

7. The method for testing the frequency response of a DC voltage transformer based on wireless synchronization according to any one of claims 1 to 5, characterized in that: The test host uses DFT calculation to obtain the fundamental wave and amplitude and phase of each harmonic of the standard signal at time 0, and sends the harmonic order required for testing to the wireless slave. The wireless slave uses frequency tracking to calculate the actual frequency of the DC voltage transformer under test.

8. The method for testing the frequency response of a DC voltage transformer based on wireless synchronization according to any one of claims 1 to 5, characterized in that: After the test, the phase error of the frequency response of the DC voltage transformer is expressed by time, and the frequency response time of each harmonic is obtained as : in, 、 are the phases of the standard signal and the DC voltage transformer under test, 、 are the fundamental frequencies of the standard signal and the DC voltage transformer under test respectively.

9. A DC voltage transformer frequency response test system based on wireless synchronization, comprising a standard signal source for generating a standard signal and providing it to the DC voltage transformer under test, characterized in that: Also includes: A test host and a wireless slave, wherein the test host and the wireless slave are wirelessly connected and configured for time synchronization. The test host is also connected to the standard signal source to collect the standard signal output by the standard signal source using a variable frequency sampling method, then detect the fundamental frequency and calculate the spectrum. The detected fundamental frequency and the number of spectrum harmonics to be tested are sent to the wireless slave. The wireless slave is also connected to the DC voltage transformer under test to collect the optical fiber digital signal output by the DC voltage transformer under test using a digital sampling method, interpolate the collected optical fiber digital signal according to the received fundamental frequency to adjust the sampling frequency, and calculate the corresponding actual spectrum parameters according to the received spectrum harmonics, and return them to the test host. The test host performs a DC voltage transformer frequency response test based on the actual spectrum parameters returned by the wireless slave.

10. The wireless synchronization-based DC voltage transformer frequency response test system according to claim 9, characterized in that: The standard signal source includes a large voltage generator and a voltage divider connected to each other. The large voltage generator is used to generate a large voltage signal of arbitrary waveform and provide it to the DC voltage transformer under test and the voltage divider respectively. The voltage divider is used to divide the large voltage signal to generate a small voltage signal as a standard signal.

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