Direct-current voltage transformer frequency response test method and system based on wireless synchronization

Abstract

The invention discloses a direct current voltage transformer frequency response test method and system based on wireless synchronization, and the method comprises the steps: configuring a test host and a wireless sub-machine, and carrying out the wireless synchronization of the test host and the wireless sub-machine; the test host collects a standard signal output by the standard source, and the wireless sub-machine collects an optical fiber digital signal output by the tested DC voltage transformer; the test host detects the fundamental frequency of the standard signal and sends the standard signal to the wireless sub-machine; the wireless sub-machine performs interpolation on the acquired optical fiber digital signal according to the fundamental wave frequency so as to adjust the sampling frequency; the test host performs frequency spectrum calculation on the standard signal, and sends the harmonic order needing to be tested to the wireless sub-machine; the wireless sub-machines return the corresponding actual spectrum parameters to the test host; and the test host executes a direct-current voltage transformer frequency response test according to the actual frequency spectrum parameters. The method has the advantages of simplicity in implementation and operation, low test cost, high test efficiency and precision, safety, reliability and the like.

Description

Technical Field

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

[0002] DC voltage transformer is an important primary equipment in the construction and operation of DC transmission system, providing accurate and reliable measurement information for DC control and protection system. Its operation reliability and measurement accuracy are directly related to the safe and stable operation of DC transmission system. At present, each converter station may have the situation that the DC control and protection action speed slows down due to the long response time of DC voltage transformer, which leads to system failure. In addition, due to the coupling channel between AC and DC in the converter process, the DC voltage will have a large number of high-frequency signals, so it is necessary to conduct frequency response test on DC voltage transformer on site.

[0003] At present, there are two main testing methods for 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, the test range of this type of open-loop test method is limited. It 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, so the test cost is relatively high. The other method is the AC voltage closed-loop test method, which applies AC voltage signals of different frequencies to the DC voltage transformer, and the DC electronic transformer tester synchronously 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 method, since the merging unit is placed in the control room and the DC voltage source and the standard are outdoors, the test optical fiber must be arranged in advance during the test to transmit the merging unit data to the tester. The control room of the UHV DC converter station is far away from the transformer (usually hundreds of meters or even thousands of meters away), and the workload of arranging the test optical fiber on site is very large. Not only is the test complexity and efficiency low, but there are also 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 in a variable frequency sampling manner, and the wireless slave collects the optical fiber digital signal output by the DC voltage transformer under test in a digital sampling manner;

[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 performs spectrum calculation on the standard signal and sends the spectrum harmonic order required to be tested in the calculation result to the wireless slave;

[0012] The wireless slave calculates the corresponding actual spectrum parameters according to the frequency spectrum harmonics 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] Further, 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 by optical fiber, and the test host and the wireless slave are synchronized by 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 time synchronization state; after entering the time synchronization state, the wireless slave is moved to the acquisition and merging unit in the main control room and maintains the time synchronization state.

[0017] Furthermore, after the wireless synchronization between the test host and the wireless sub-unit, the method also includes performing any one or more of sample filtering, frequency correction and delay correction between the test host and the wireless sub-unit 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-unit. The delay correction is used to correct the clock delay between the test host and the wireless sub-unit.

[0018] Further, the 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, and the frequency correction coefficient is calculated according to the time when the test host sends the synchronization message twice and the time when the wireless slave receives the synchronization message twice. 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:

[0019]

[0020] Among them, C n is the current sub-frequency correction coefficient, T n ′ is the arrival time of the message currently received by the wireless slave, T n-1 ′ is the arrival time of the message received by the wireless slave last time, T n T is the time when the test host sends the current message. n-1 The time when the test host last sent a message.

[0021] 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.

[0022] Furthermore, the wireless sub-unit adopts the Lagrange quadratic interpolation method when interpolating the collected optical fiber digital signal according to the fundamental frequency, and the collected optical fiber digital signal is expressed as y=f(x). The signal obtained after interpolation using the Lagrange quadratic interpolation method is:

[0023]

[0024] Among them, x k-1 、x k 、x k+1 are the data points at time k-1, k and k+1 respectively, y k-1 ,y k ,y k+1 In x k-1 、x k 、x k+1 The function value at the point.

[0025] Furthermore, the test host obtains the fundamental wave and amplitude and phase of each harmonic of the standard signal at time 0 by using DFT calculation, and sends the harmonic order required for testing to the wireless slave, and the wireless slave calculates the actual frequency of the DC voltage transformer under test by using frequency tracking.

[0026] 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 tr:

[0027] t r =φ s / 2πf s -φ b / 2πf b

[0028] Among them, φ s ,φ b The phase of the standard signal and the DC voltage transformer under test, f s 、f b They are the fundamental frequencies of the standard signal and the DC voltage transformer under test respectively.

[0029] A DC voltage transformer frequency response test system based on wireless synchronization includes a standard signal source for generating a standard signal to be provided to a DC voltage transformer under test, and also includes: a test host and a wireless sub-machine, wherein the test host is wirelessly connected to the wireless sub-machine and configured for time synchronization, the test host is also connected to the standard signal source for collecting the standard signal output by the standard signal source, detecting the fundamental frequency and calculating the spectrum, sending the detected fundamental frequency and the harmonic number required to be tested to the wireless sub-machine, and performing a DC voltage transformer frequency response test according to the actual spectrum parameters returned by the test host, the wireless sub-machine is also connected to the DC voltage transformer under test for collecting the optical fiber digital signal output by the DC voltage transformer under test, adjusting the sampling frequency according to the received fundamental frequency and calculating the spectrum according to the received harmonic number, and providing the calculated spectrum parameters as synchronization parameters to the test host.

[0030] 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.

[0031] Compared with the prior art, the advantages of the present invention are:

[0032] 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, which can solve the problem of arranging a long-distance test optical fiber during the DC voltage transformer frequency response test, reduce the test cost, and improve the test efficiency.

[0033] 2. The present invention adopts 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 base frequency to the wireless slave. The wireless slave adjusts the frequency by interpolation according to the synchronization time and the base frequency value sent by the test host, so that the test host and the wireless slave are synchronized in time, which can ensure that the test results will not be affected by the crystal oscillator of the test host and the wireless slave and the randomness of the sampling time, and further improve the test accuracy.

[0034] 3. The present invention is based on wireless transmission. The test host interacts with the sub-machine according to the spectrum calculation results to be tested. Only the frequency and harmonic number need to be transmitted between the test host and the wireless sub-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

[0035] Figure 1 It is a schematic diagram of the structural principle of the DC voltage transformer frequency response test system based on wireless synchronization in this embodiment.

[0036] Figure 2 It is a schematic diagram of the implementation flow of the DC voltage transformer frequency response test based on wireless synchronization in this embodiment.

[0037] Figure 3 2 is a schematic diagram of the principle of frequency correction in this embodiment.

[0038] Figure 4 Schematic diagram of the phasor corresponding to the sampling value in this embodiment. DETAILED DESCRIPTION

[0039] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0040] The core of the present invention is to configure a test host and a wireless slave, and the test host and the wireless slave respectively collect a standard signal and a signal of a tested DC voltage transformer, and realize a DC voltage transformer frequency response test based on a master-slave mode. The test operation is simple and convenient, and there is no need to arrange a test optical fiber on site. At the same time, considering that the real-time sampling value cannot be transmitted under LOR A low-speed transmission, and different sampling systems will affect the sampling accuracy of the waveform, the present invention synchronizes the time of the test host and the wireless slave, the test host adopts a variable frequency sampling mode, and the wireless slave adopts an interpolation digital sampling mode, and the wireless slave adopts an interpolation mode to realize frequency adjustment according to the synchronization time and the fundamental frequency value sent by the test host, so as to ensure the synchronization between the test host and the wireless slave, so that the master-slave two systems calculate the spectrum at the same frequency and the same time, and ensure that the test result will not be affected by the crystal oscillator of the test host and the wireless slave and the randomness of the sampling time, so that the test accuracy can be greatly improved on the basis of ensuring the test efficiency, and the DC voltage transformer frequency response test can be realized quickly and accurately.

[0041] To implement the DC voltage transformer frequency response test, this embodiment constructs Figure 1 The DC voltage transformer frequency response test system based on wireless synchronization shown includes a standard signal source for generating a standard signal to provide to the DC voltage transformer under test, and also includes: 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 for collecting the standard signal output by the standard signal source, detecting the fundamental frequency and calculating the spectrum, sending the detected fundamental frequency and the harmonic number required to be tested to the wireless slave, and performing the DC voltage transformer frequency response test according to the actual spectrum parameters returned by the test host, the wireless slave is also connected to the DC voltage transformer under test for collecting the optical fiber digital signal output by the DC voltage transformer under test, adjusting the sampling frequency according to the received fundamental frequency and calculating the spectrum according to the received harmonic number, and providing the calculated spectrum parameters as synchronization parameters to the test host.

[0042] 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 and the voltage divider under test respectively, and the voltage divider is used to divide the large voltage signal to generate a small voltage signal as a standard signal. It can be understood that the standard signal source can also be implemented using other types of structures to provide the required standard signal.

[0043] The above system of this embodiment can solve the problem of arranging long-distance test optical fiber when testing the frequency response of DC voltage transformer by using LORA wireless transmission mode to transmit data between master and slave, reduce test cost and improve test efficiency; use wireless synchronization mode based on LORA communication to make master and slave perform synchronous calculation, which can solve the problem of low bandwidth of LORA signal transmission; the test host interacts with the slave machine with the spectrum parameters required for testing according to the spectrum calculation results, which can also reduce the amount of LORA transmission data and communication time, thereby further improving the test efficiency. In addition, the test host uses standard source frequency tracking and frequency measurement to send the base frequency to the wireless slave machine, and the wireless slave machine performs secondary interpolation according to the base frequency of the standard signal for the digital quantity signal of the DC voltage transformer under test and then performs spectrum calculation, which can further improve the overall accuracy of the test.

[0044] In a specific application embodiment, after constructing the above-mentioned DC voltage transformer frequency response test system, the test host and the wireless sub-machine are first synchronized by optical fiber wire, and then the synchronization optical fiber is unplugged, the wireless sub-machine is synchronized and timed, and then the wireless sub-machine is moved to a distant place for wireless synchronization correction. The test host collects the small analog voltage signal of the standard voltage divider and then measures the frequency, and then sends the fundamental frequency to the wireless sub-machine through LORA. The test host adjusts the sampling frequency, and the wireless sub-machine completes the sampling frequency adjustment through secondary interpolation. After the wireless sub-machine is synchronized, the spectrum is calculated according to the host's synchronization time. After the calculation, the test host sends the frequency times that need to be tested to the wireless sub-machine, and the wireless sub-machine sends the actual frequency, amplitude, and phase of the corresponding frequency to the test host. The test host finally completes the DC voltage transformer frequency response test according to the synchronization amplitude and phase of the host and sub-machine.

[0045] like Figure 2 As shown, the detailed steps of the DC voltage transformer frequency response test method based on wireless synchronization in this embodiment include:

[0046] Step S01. Configure a test host and a wireless slave, and wirelessly synchronize the test host and the wireless slave.

[0047] Specifically, first follow the Figure 1 The method shown configures a test host and a wireless slave, the test host and the wireless slave are wirelessly connected, the test host is also connected to a standard voltage divider, and the wireless slave is also connected to the DC voltage transformer under test. The test host is used as the host and the wireless slave is used as the slave, and then the test host and the wireless slave are wirelessly synchronized to achieve the frequency response test of the DC voltage transformer using the master-slave control method.

[0048] As an optional implementation, the following steps may be used to wirelessly synchronize the test host and the wireless slave:

[0049] Step S101. Wired synchronization between the host and the slave: Before the test begins, the test host and the wireless slave are connected by optical fiber, and the test host and the wireless slave are synchronized by 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 time synchronization state.

[0050] Specifically, before the test begins, the test host and the wireless slave can be placed together, and after being connected 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, and 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 a punctual synchronization state.

[0051] Step S102: After entering the time-keeping synchronization state, move the wireless slave to the acquisition and merging unit in the main control room and maintain the time-keeping synchronization state.

[0052] 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.

[0053] Preferably, the synchronization timing accuracy between the test host and the wireless slave can be configured to reach 4us / 10min, thereby ensuring the accuracy of subsequent tests.

[0054] As an optional implementation, after the test host and the wireless slave are wirelessly synchronized, the process further includes sample filtering, frequency correction, and delay correction between the test host and the wireless slave, so as to achieve wireless synchronization correction and further improve the accuracy of wireless synchronization. Among them, sample filtering is used to use the synchronization message as sample data, and filter the sample data whose deviation value of two adjacent sample data exceeds the preset maximum deviation value, frequency correction is used to adjust the frequency deviation of the clock between the test host and the wireless slave, and delay correction is used to correct the clock delay between the test host and the wireless slave.

[0055] Optionally, when performing sample filtering on the synchronization message, based on the mutation limit of stable data transmission, two adjacent sample data T n and T n+1 If the actual sample data deviation value exceeds the maximum deviation, it indicates that interference has occurred. The sample data is discarded and the previous data is used to replace the current sample data. If it is less than the maximum deviation value, the sample data is considered normal.

[0056] Optionally, the specific steps of frequency correction for the test host and the wireless slave include: the test host sends a synchronization message to the wireless slave at a fixed frequency, calculates a frequency correction coefficient according to the time when the test host sends the synchronization message twice and the time when the wireless slave receives the synchronization message twice, and the wireless slave uses the frequency correction coefficient to perform discrete point correction on its own clock frequency to ensure frequency synchronization between the master and the slave. To further prevent over-modulation oscillation, smooth adjustment can be used.

[0057] Preferably, the frequency correction coefficient can be calculated as follows:

[0058]

[0059] Among them, C n is the current sub-frequency correction coefficient, T n ′ is the arrival time of the message currently received by the wireless slave, T n-1 ′ is the arrival time of the message received by the wireless slave last time, T n T is the time when the test host sends the current message. n-1 The time when the test host last sent a message.

[0060] 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, and 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.

[0061] 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 measurement 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 loop of the master-slave message, a more accurate average path delay can be obtained to achieve delay correction.

[0062] Step 2: The test host collects the standard signal output by the standard source by frequency conversion sampling, and the wireless slave collects the optical fiber digital signal output by the DC voltage transformer under test by digital sampling.

[0063] Specifically, after the test host and the wireless slave enter the synchronization state, the test host and the wireless slave independently perform data collection. The test host collects the analog small voltage signal of the standard source and adopts a variable frequency sampling method, while the wireless slave adopts a digital sampling method to collect the optical fiber digital signal from the DC voltage transformer.

[0064] Optionally, a hardware frequency conversion sampling method is adopted in 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 hardware clock of the FPGA 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.

[0065] Step 3: The test host detects the fundamental frequency of the standard signal and sends the detected fundamental frequency to the wireless slave.

[0066] When tracking the fundamental frequency of the standard source signal, assume that the sampled voltage signal is as follows:

[0067] v(t)=V cos(2πft) (2)

[0068] The signal is sampled at a fixed sampling rate, assuming the sampling frequency f S =50×N, the obtained sampling sequence is: v k , v k-1 , v k-2 , v k-3 ......, using the phasor method for analysis, the phasors corresponding to the sampling sequence are: Assume that its phase distribution is as follows Figure 4 As shown. Among them, 2θ is the angle between the phases, 2θ=2πfT S , T S =1 / f S .

[0069] From the phasor diagram we can get:

[0070]

[0071] The following formula is obtained:

[0072]

[0073] Assuming the above result (phase shift caused by actual frequency) is x, then The fundamental frequency of the system can be obtained:

[0074]

[0075] Optionally, when sampling the standard signal, the test host uses its own crystal oscillator as the reference 0 point, tracks the standard signal according to the frequency f after frequency measurement, calculates the fundamental frequency of the system in real time, and uses the hardware clock of the FPGA inside the host to control the sampling trigger moment of the AD, so as to adjust the sampling interval period of the AD and correct the sampling rate of the host AD in real time. Among them, a discrete sampling sequence of x(i) is generated, and when i=0 is the GPS synchronization moment. Then, DFT is used for discrete Fourier integration to obtain the fundamental wave of the standard signal at the 0 point and the amplitude and phase of each harmonic, that is:

[0076]

[0077] Where N is the total number of samples in the time window, X R , X I are the real and imaginary parts of the standard source signal respectively.

[0078] 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 sub-unit.

[0079] 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.

[0080] Specifically, the signal of the DC voltage transformer under test is first collected by the acquisition unit of the DC electronic transformer, and then the wireless slave performs digital sampling on the signal collected by the acquisition unit of the DC electronic transformer. In the process of the wireless slave sampling the signal of the DC voltage transformer under test, the test host sends the frequency to the wireless slave through the LORA wireless method. After receiving the frequency signal of the host, the wireless slave uses the synchronization signal as the reference 0 point. Since the sampling of the DC voltage transformer under test is completed by the acquisition unit of the DC electronic transformer, the sampling rate of the acquisition unit of the DC electronic transformer is fixed and cannot be adjusted, and the sampling rates of different systems will affect the sampling accuracy. In this embodiment, the digital signal collected by the wireless sub-machine is interpolated to obtain the discrete sampling of the digital signal about the frequency f, so as to adjust the frequency. Subsequently, DFT is used to perform Fourier integration to obtain the fundamental wave of the standard source signal at the time of 0 and the amplitude and phase of each harmonic. The actual frequency of the DC voltage transformer under test can be calculated by frequency tracking, that is, the sampling frequency of the DC voltage transformer under test by the wireless sub-machine is obtained by tracking the standard source frequency of the test host. The wireless sub-machine obtains a new sampling sequence by sampling the collected optical fiber digital signal in a secondary interpolation manner according to the sampling rate of the DC voltage transformer under test.

[0081] As an optional implementation, the wireless sub-unit can use Lagrange quadratic interpolation to interpolate the collected optical fiber digital signal according to the fundamental frequency. Lagrange quadratic interpolation is to construct 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), and the known 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 ), and obtain a polynomial P2(x) of degree not exceeding 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 by interpolation using Lagrange quadratic interpolation is:

[0082]

[0083] Among them, x k-1 、x k 、x k+1 are the data points at time k-1, k and k+1 respectively, y k-1 ,y k ,y k+1 In x k-1 、x k 、x k+1 The function value at the point.

[0084] Step 5: The test host performs spectrum calculation on the standard signal and sends the spectrum harmonic order required to be tested in the calculation result to the wireless slave.

[0085] Specifically, the test host uses DFT calculation to obtain the fundamental wave of the standard signal at time 0 and the amplitude and phase of each harmonic, and sends the harmonic order required for testing to the wireless slave, which then uses frequency tracking to calculate the actual frequency of the DC voltage transformer under test.

[0086] Step 6: The wireless slave calculates the corresponding actual spectrum parameters according to the frequency spectrum harmonics required to be tested and returns them to the test host.

[0087] Since LORA is a low-speed transmission, it is impossible to transmit the actual sampling value, nor can it send all harmonic signals to the test host. This embodiment uses the data interaction between the master and slave machines, and uses the required test spectrum harmonic times to calculate the corresponding actual spectrum parameters. It only needs to transmit the fundamental frequency and harmonic times between the master and slave machines, and does not need to transmit the complete harmonic signal. It can solve the problem of arranging long-distance test optical fibers when testing the frequency response of DC voltage transformers, reduce test costs, and reduce the amount of LORA transmission data, reduce communication time, and effectively improve test efficiency.

[0088] Specifically, the spectrum parameters include amplitude, phase, and frequency. The test host sends the harmonic order of the spectrum to be tested to the wireless slave according to 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 obtains the synchronized standard signal and the amplitude (U b , U s ) and phase

[0089] Step 7: The test host performs a DC voltage transformer frequency response test based on the actual spectrum parameters returned by the wireless slave.

[0090] 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 according to the actual spectrum parameters to complete the test process.

[0091] After the test is completed, the frequency error can be expressed as:

[0092] f ε =f s -f b (9)

[0093] Among them, f s 、f b They are the fundamental frequencies of the standard signal and the DC voltage transformer under test respectively.

[0094] The amplitude error can be expressed as:

[0095] ε%=100%*(U s -U b ) / U b (10)

[0096] The phase error of the frequency response of the DC voltage transformer is expressed in time, and the frequency response time of each harmonic is tr:

[0097] t r =φ s / 2πf s -φ b / 2πf b (11)

[0098] Among them, φ s ,φ b Respectively measure the phase of the standard signal and the DC voltage transformer under test.

[0099] 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.

[0100] The present invention realizes the frequency response test of the DC voltage transformer by utilizing the LORA wireless transmission mode, which can avoid the arrangement of test optical fibers 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 for the frequency and harmonic number to be tested, which can also reduce the amount of LORA transmission data, reduce the communication time, improve the test efficiency, and realize fast and accurate frequency response test of the DC voltage transformer.

[0101] 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 complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. 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 codes. 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 the 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 the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the functions 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 an instruction device, which implements the functions specified in the process. Figure 1 A process or multiple processes and / or boxes Figure 1These 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, so that the instructions executed on the computer or other programmable device provide 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.

[0102] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment, it is not intended to limit the present invention. Therefore, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the content of the technical solution 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 in a variable frequency sampling manner, and the wireless slave collects the optical fiber digital signal output by the DC voltage transformer under test in a digital sampling manner; 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 performs spectrum calculation on the standard signal and sends the spectrum harmonic order required to be tested in the calculation result to the wireless slave; The wireless slave calculates the corresponding actual spectrum parameters according to the frequency spectrum harmonics required 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 by optical fiber, and the test host and the wireless slave are synchronized by 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 time synchronization state; after entering the time synchronization state, the wireless slave is moved to the acquisition and merging unit in the main control room and maintains the time 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 between the test host and the wireless sub-unit is performed, it also includes performing any one or more of sample filtering, frequency correction and delay correction between the test host and the wireless sub-unit 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-unit. The delay correction is used to correct the clock delay between the test host and the wireless sub-unit.

4. The method for testing the frequency response of a DC voltage transformer based on wireless synchronization according to claim 3 is characterized in that: The 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, and the frequency correction coefficient is calculated according to the time when the test host sends the synchronization message twice and the time when the wireless slave receives the synchronization message twice. 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: Among them, C n is the current sub-frequency correction coefficient, T n ′ is the arrival time of the message currently received by the wireless slave, T n-1 ′ is the arrival time of the message received by the wireless slave last time, T n T is the time when the test host sends the current message. 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 by using the Lagrange quadratic interpolation method, and the collected optical fiber digital signal is expressed as y=f(x). The signal obtained after interpolation by using the Lagrange quadratic interpolation method is: Among them, x k-1 、x k 、x k+1 are the data points at time k-1, k and k+1 respectively, y k-1 ,y k ,y k+1 In x k-1 、x k 、x k+1 The 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 obtains the fundamental wave and the amplitude and phase of each harmonic of the standard signal at time 0 by using DFT calculation, and sends the harmonic order required for testing to the wireless slave, and the wireless slave calculates the actual frequency of the DC voltage transformer under test by frequency tracking.

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 tr: t r =φ s / 2πf s -f b / 2πf b Among them, φ s ,φ b The phase of the standard signal and the DC voltage transformer under test, f s 、f b They 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 to provide to a DC voltage transformer under test, characterized in that: Also includes: A test host and a wireless slave, wherein 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 for collecting the standard signal output by the standard signal source and then performing fundamental frequency detection and spectrum calculation, the detected fundamental frequency and the harmonic number required for test are sent to the wireless slave, and a DC voltage transformer frequency response test is performed according to the actual spectrum parameters returned by the test host, the wireless slave is also connected to the DC voltage transformer under test for collecting the optical fiber digital signal output by the DC voltage transformer under test, and the sampling frequency is adjusted according to the received fundamental frequency and the spectrum is calculated according to the received harmonic number, and the calculated spectrum parameters are provided to the test host as synchronization parameters.

10. The DC voltage transformer frequency response test system based on wireless synchronization 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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