A System and Method for Synchronous Acquisition Performance Testing of Distribution Terminals Based on Synchronous Phasors

Abstract

This invention proposes a synchronous acquisition performance testing system and method for power distribution terminals based on synchronous phasors. This system is used to test power distribution terminals capable of recording waveforms of multi-channel electrical quantities. During operation, the power distribution terminal under test records waveforms of multi-channel electrical quantities and transmits the recorded waveforms to the synchronous acquisition performance detection system of the testing system. The testing system includes: a GPS / BeiDou signal forwarding module for achieving indoor GPS / BeiDou signal coverage, enabling the power distribution terminal under test to synchronize its time via GPS / BeiDou signals under test conditions; a synchronous testing system that outputs specified multi-channel electrical quantities to the power distribution terminal under test at whole seconds; and a synchronous acquisition performance detection system that receives waveforms from all power distribution terminals under test and analyzes the waveforms to determine if the synchronous acquisition performance of each terminal meets the requirements. This invention facilitates the control of the synchronous acquisition performance of power distribution terminals, ensuring the reliability of advanced functions based on synchronous acquisition.

Description

Technical Field

[0001] This invention relates to the field of power distribution equipment testing technology, and in particular to a power distribution terminal synchronous acquisition performance testing system and method based on synchronous phasors. Background Technology

[0002] In power distribution networks, main grid equipment primarily uses the IEC 61850 protocol for communication. By parsing the communication messages of the IEC 61850 protocol, the sampling time of the equipment can be obtained, thereby determining the synchronous acquisition performance of the equipment. Thanks to this, advanced technologies such as differential protection and traveling wave ranging have been widely applied, making synchronous acquisition technology mature in the main grid field. Currently, the concept of synchronous acquisition has gradually been introduced from the main grid field to the distribution network field, but its effectiveness in the distribution network field is not ideal. In particular, since most current distribution terminals use the IEC 101 and IEC 104 protocols for communication, the relevant messages do not contain information such as the sampling time of the equipment. Therefore, it is impossible to evaluate the synchronous acquisition performance of the distribution terminal by parsing the messages. Consequently, there is currently no mature testing method or platform for the synchronous acquisition performance of distribution terminals, making it difficult to ensure the quality of distribution terminals during the grid access testing stage. These problems need to be solved. Summary of the Invention

[0003] This invention proposes a system and method for testing the synchronous acquisition performance of power distribution terminals based on synchronous phasors. This method and corresponding platform are beneficial for controlling the synchronous acquisition performance of power distribution terminals and ensuring the reliability of advanced functions related to synchronous acquisition in power distribution terminals.

[0004] The present invention adopts the following technical solution.

[0005] A synchronous acquisition performance testing system for distribution terminals based on synchronous phasors is used to test distribution terminals capable of recording waveforms of multi-channel electrical quantities. When the testing system is operational, the distribution terminal under test records waveforms of multi-channel electrical quantities and transmits the recorded waveforms to the synchronous acquisition performance detection system of the testing system. The testing system includes:

[0006] The GPS / BeiDou signal forwarding module is used to achieve indoor GPS / BeiDou signal coverage, enabling the power distribution terminal equipment under test to synchronize time via GPS / BeiDou signals in the test environment;

[0007] The synchronous testing system outputs specified multi-channel electrical quantities to the power distribution terminal under test at the exact second.

[0008] The synchronous acquisition performance testing system receives waveforms from all the power distribution terminals under test and analyzes the waveforms to determine whether the synchronous acquisition performance of each power distribution terminal meets the requirements.

[0009] The GPS / BeiDou signal relay module includes: an outdoor signal receiver, a wire, and an indoor signal amplifier;

[0010] When the test system is working, the outdoor signal receiver is placed in an open outdoor area to receive GPS / BeiDou signals; the wire is used to transmit the GPS / BeiDou signals received by the outdoor signal receiver to the indoor signal amplifier; the indoor signal amplifier amplifies the received GPS / BeiDou signals so that the GPS / BeiDou signals cover the entire indoor test environment, ensuring that the power distribution terminal under test can synchronize time via GPS / BeiDou signals in the indoor test environment.

[0011] The synchronous testing system includes a synchronous tester modified from a relay protection tester. The synchronous tester has the same functions as the original relay protection tester, and also includes an output interface that ensures all output signals start being output at the exact second.

[0012] When the test system is working, the synchronous test system tests each power distribution terminal under test one by one, or tests multiple power distribution terminals under test by using parallel voltage channels and series current channels, so as to ensure that the voltage and current signals collected by all power distribution terminals participating in the test are completely consistent in time and amplitude.

[0013] When the power distribution terminal under test receives the multi-channel electrical quantity signal output by the synchronous test system, if the electrical quantity signal meets the waveform recording start condition, the waveform recording function of the power distribution terminal is triggered, so that the power distribution terminal records the waveform within at least 80ms before the waveform recording trigger time and within at least 160ms after the trigger time, and generates a waveform recording file, which is sent to the synchronous acquisition performance testing system in the form of a waveform file.

[0014] The synchronous acquisition performance testing system receives waveform files from all the power distribution terminals under test and then parses the waveform files.

[0015] The analysis method is as follows: according to the setting of the synchronous test system starting to output at the whole second and the waveform cycle being 20ms, calculate the theoretical phase at several waveform recording sampling time points, compare it with the actual phase recorded in the waveform file at that time, calculate the synchronous acquisition error of the power distribution terminal, and thus determine whether the synchronous acquisition performance of the power distribution terminal meets the requirements.

[0016] The method for using the power distribution terminal synchronous acquisition performance test system based on synchronous phasors is a method for testing the synchronous acquisition performance of power distribution terminals, including the following steps;

[0017] Step S1, Experimental environment setup, including: GPS / BeiDou signal coverage in the experimental environment, connection to the synchronous test system, the power distribution terminal under test, and the synchronous acquisition performance testing system, and setting the waveform recording trigger conditions for the power distribution terminal under test;

[0018] Step S2, synchronous acquisition test, includes: the synchronous test system outputs the test waveform, the power distribution terminal under test triggers the waveform recording condition and records the test waveform, and the power distribution terminal under test sends the recorded waveform to the synchronous acquisition performance testing system;

[0019] Step S3, Detection Result Analysis, including: waveform analysis and result analysis.

[0020] Step S1 includes the following steps;

[0021] Step S1-1, Experimental Environment GPS / BeiDou Signal Coverage: Place the outdoor signal receiver of the GPS / BeiDou signal relay module in an open outdoor area, and connect it to the indoor signal amplifier of the GPS / BeiDou signal relay module using a wire;

[0022] Step S1-2: Connect the synchronous test system, the power distribution terminal under test, and the synchronous acquisition performance testing system: Connect the synchronous tester and the power distribution terminal to be tested using a parallel voltage channel and a series current channel; connect the power distribution terminal and the synchronous acquisition performance testing system using a network cable and an Ethernet switch to ensure normal communication between the power distribution terminal and the synchronous acquisition performance testing system.

[0023] Step S1-3: Set the waveform recording trigger conditions for the power distribution terminal under test: Set the waveform recording start conditions for each power distribution terminal participating in the test to ensure that the power distribution terminal can record waveforms normally when the synchronous test system starts outputting electrical quantity signals, and that the power distribution terminal does not start waveform recording when the synchronous test system does not output signals; if the synchronous acquisition performance test system tests multiple power distribution terminals at the same time, the waveform recording start conditions of all power distribution terminals must be kept consistent.

[0024] Step S2 includes the following steps;

[0025] Step S2-1: Output test waveform of synchronous test system: First set the synchronous test system to output test waveform, then issue "start output" command. After receiving the command, the synchronous test system will start outputting at the next whole second.

[0026] Step S2-2: Trigger the waveform recording condition and record the test waveform of the power distribution terminal under test: After the power distribution terminal under test receives the signal output by the synchronous test system, the waveform recording start condition is triggered, the terminal starts recording waveforms, records the waveforms at least 80ms before the waveform recording trigger time and at least 160ms after the trigger time, and generates a waveform recording file.

[0027] Step S2-3: The power distribution terminal under test sends the recorded waveform to the synchronous acquisition performance testing system: The power distribution terminal under test sends the recorded waveform file to the synchronous acquisition performance testing system via the IEC 101 protocol or the IEC 104 protocol.

[0028] Step S3 includes the following steps;

[0029] Step S3-1, Waveform Analysis: The synchronous acquisition performance testing system analyzes the waveform recording file to obtain the waveform of each voltage and current signal, including the amplitude and sampling time of each sampling point;

[0030] Step S3-2, Result Analysis: The synchronous acquisition performance testing system compares the phase of the actual sampling time point of the recorded waveform with the theoretical phase of the corresponding time point to draw test conclusions;

[0031] The theoretical phase value of the actual sampling time point of the recorded waveform is calculated according to the output of the synchronous tester at the whole second, with each waveform cycle being 20ms long.

[0032] Among them, the phase of the output waveform of the synchronous test system and the waveform of the power distribution terminal under test are calculated by using the full-wave Fourier algorithm, the phase difference between the output waveform of the synchronous test system and the terminal waveform are compared, and the maximum value of the phase difference between the two is used as the performance evaluation index of the synchronous acquisition of the power distribution terminal.

[0033] The specific method is as follows: Figure 3 As shown, firstly, the output waveform with a duration of mT and the terminal waveform are selected at the output waveform sampling time of... The sampling points are then used to calculate the phase angle between the output waveform of the synchronous test system and the waveform of the power distribution terminal under test at the above time points using the full-wave Fourier algorithm. The difference is then compared, and the maximum value of the phase difference between the two is taken as the synchronous acquisition error of the power distribution terminal.

[0034] The full-wave Fourier algorithm is used as follows: assuming a periodic sampled signal x(t) can be decomposed into...

[0035] In the formula, X mn Let α be the amplitude of the nth harmonic component. n Let a be the phase angle of this component at t=0. n and b n These are the amplitudes of the sine and cosine components of each harmonic, respectively.

[0036] Based on the principle of solving for the nth harmonic component using Fourier series and after discretization, the formula is as follows:

[0037] In the formula, T is the period of the fundamental frequency component, w1 is the angular frequency of the fundamental frequency component, and N is the number of sampling points in the period. In the discrete case:

[0038]

[0039] The phase angle of the obtained signal is

[0040]

[0041] Therefore, the synchronous acquisition error of the power distribution terminal under test is

[0042] θ = max{θ1, θ2, ..., θ 4m}=max{|α1-β1|, |α2-β2|,...,|α 4m -β 4m |}

[0043] In the formula, θ k Sampling time point The phase difference α between the target waveform and the terminal waveform k Sampling time point The phase of the target waveform, β k Sampling time point The phase of the test waveform is measured; finally, the maximum phase difference between the target waveform and the test waveform at each of the above sampling time points is taken as the synchronization acquisition error of the power distribution terminal under test.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] 1) A system and method for testing the synchronous acquisition performance of distribution terminals based on synchronous phasors are provided, filling the gap in the lack of a mature integrated testing platform for the synchronous acquisition performance of distribution terminals in China.

[0046] 2) The integrated testing platform for synchronous acquisition performance of power distribution terminals proposed in this invention can simultaneously test the synchronous acquisition performance of multiple power distribution terminals. These features give this system the following advantages:

[0047] a. Improve the testing efficiency of synchronous data acquisition performance of power distribution terminals. The platform's synchronous testing system outputs waveforms at the second-by-second interval, and the power distribution terminal under test acquires data at the second-by-second interval, with a unified sampling time scale. Provided that the output power of the synchronous testing system allows, multiple devices can be tested simultaneously, and generally, the number of power distribution terminals tested at the same time can exceed 10.

[0048] b. Increase the comparative dimensions of synchronous performance data acquisition from distribution terminals. When multiple distribution terminals are tested simultaneously, the difference between the actual phase and the theoretical phase at the sampling points of the distribution terminals can be compared, as can the difference between the actual phase at the sampling points of different terminals.

[0049] 3) The present invention proposes a method for detecting the synchronous acquisition performance of power distribution terminals, which clarifies the quantitative evaluation index of the synchronous acquisition performance of power distribution terminals and can intuitively reflect the synchronous acquisition performance of power distribution terminals. Attached Figure Description

[0050] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0051] Appendix Figure 1 This is a schematic diagram of the integrated testing platform (testing system) architecture according to an embodiment of the present invention;

[0052] Appendix Figure 2 This is a flowchart of a detection method according to an embodiment of the present invention;

[0053] Appendix Figure 3 This is a waveform phase comparison diagram of a detection method according to an embodiment of the present invention. Detailed Implementation

[0054] like Figure 1 As shown, a synchronous acquisition performance test system for distribution terminals based on synchronous phasors is used to test distribution terminals capable of recording waveforms of multi-channel electrical quantities. When the test system is working, the distribution terminal under test records waveforms of multi-channel electrical quantities and transmits the recorded waveforms to the synchronous acquisition performance detection system of the test system. The test system includes:

[0055] The GPS / BeiDou signal forwarding module is used to achieve indoor GPS / BeiDou signal coverage, enabling the power distribution terminal equipment under test to synchronize time via GPS / BeiDou signals in the test environment;

[0056] The synchronous testing system outputs specified multi-channel electrical quantities to the power distribution terminal under test at the exact second.

[0057] The synchronous acquisition performance testing system receives waveforms from all the power distribution terminals under test and analyzes the waveforms to determine whether the synchronous acquisition performance of each power distribution terminal meets the requirements.

[0058] The GPS / BeiDou signal relay module includes: an outdoor signal receiver, a wire, and an indoor signal amplifier;

[0059] When the test system is working, the outdoor signal receiver is placed in an open outdoor area to receive GPS / BeiDou signals; the wire is used to transmit the GPS / BeiDou signals received by the outdoor signal receiver to the indoor signal amplifier; the indoor signal amplifier amplifies the received GPS / BeiDou signals so that the GPS / BeiDou signals cover the entire indoor test environment, ensuring that the power distribution terminal under test can synchronize time via GPS / BeiDou signals in the indoor test environment.

[0060] The synchronous testing system includes a synchronous tester modified from a relay protection tester. The synchronous tester has the same functions as the original relay protection tester, and also includes an output interface that ensures all output signals start being output at the exact second.

[0061] When the test system is working, the synchronous test system tests each power distribution terminal under test one by one, or tests multiple power distribution terminals under test by using parallel voltage channels and series current channels, so as to ensure that the voltage and current signals collected by all power distribution terminals participating in the test are completely consistent in time and amplitude.

[0062] When the power distribution terminal under test receives the multi-channel electrical quantity signal output by the synchronous test system, if the electrical quantity signal meets the waveform recording start condition, the waveform recording function of the power distribution terminal is triggered, so that the power distribution terminal records the waveform within at least 80ms before the waveform recording trigger time and within at least 160ms after the trigger time, and generates a waveform recording file, which is sent to the synchronous acquisition performance testing system in the form of a waveform file.

[0063] The synchronous acquisition performance testing system receives waveform files from all the power distribution terminals under test and then parses the waveform files.

[0064] The analysis method is as follows: according to the setting of the synchronous test system starting to output at the whole second and the waveform cycle being 20ms, calculate the theoretical phase at several waveform recording sampling time points, compare it with the actual phase recorded in the waveform file at that time, calculate the synchronous acquisition error of the power distribution terminal, and thus determine whether the synchronous acquisition performance of the power distribution terminal meets the requirements.

[0065] like Figure 2 As shown, the method of using the power distribution terminal synchronous acquisition performance test system based on synchronous phasors is a method for testing the synchronous acquisition performance of power distribution terminals, including the following steps;

[0066] Step S1, Experimental environment setup, including: GPS / BeiDou signal coverage in the experimental environment, connection to the synchronous test system, the power distribution terminal under test, and the synchronous acquisition performance testing system, and setting the waveform recording trigger conditions for the power distribution terminal under test;

[0067] Step S2, synchronous acquisition test, includes: the synchronous test system outputs the test waveform, the power distribution terminal under test triggers the waveform recording condition and records the test waveform, and the power distribution terminal under test sends the recorded waveform to the synchronous acquisition performance testing system;

[0068] Step S3, Detection Result Analysis, including: waveform analysis and result analysis.

[0069] Step S1 includes the following steps;

[0070] Step S1-1, Experimental Environment GPS / BeiDou Signal Coverage: Place the outdoor signal receiver of the GPS / BeiDou signal relay module in an open outdoor area, and connect it to the indoor signal amplifier of the GPS / BeiDou signal relay module using a wire;

[0071] Step S1-2: Connect the synchronous test system, the power distribution terminal under test, and the synchronous acquisition performance testing system: Connect the synchronous tester and the power distribution terminal to be tested using a parallel voltage channel and a series current channel; connect the power distribution terminal and the synchronous acquisition performance testing system using a network cable and an Ethernet switch to ensure normal communication between the power distribution terminal and the synchronous acquisition performance testing system.

[0072] Step S1-3: Set the waveform recording trigger conditions for the power distribution terminal under test: Set the waveform recording start conditions for each power distribution terminal participating in the test to ensure that the power distribution terminal can record waveforms normally when the synchronous test system starts outputting electrical quantity signals, and that the power distribution terminal does not start waveform recording when the synchronous test system does not output signals; if the synchronous acquisition performance test system tests multiple power distribution terminals at the same time, the waveform recording start conditions of all power distribution terminals must be kept consistent.

[0073] Step S2 includes the following steps;

[0074] Step S2-1: Output test waveform of synchronous test system: First set the synchronous test system to output test waveform, then issue "start output" command. After receiving the command, the synchronous test system will start outputting at the next whole second.

[0075] Step S2-2: Trigger the waveform recording condition and record the test waveform of the power distribution terminal under test: After the power distribution terminal under test receives the signal output by the synchronous test system, the waveform recording start condition is triggered, the terminal starts recording waveforms, records the waveforms at least 80ms before the waveform recording trigger time and at least 160ms after the trigger time, and generates a waveform recording file.

[0076] Step S2-3: The power distribution terminal under test sends the recorded waveform to the synchronous acquisition performance testing system: The power distribution terminal under test sends the recorded waveform file to the synchronous acquisition performance testing system via the IEC 101 protocol or the IEC 104 protocol.

[0077] Step S3 includes the following steps;

[0078] Step S3-1, Waveform Analysis: The synchronous acquisition performance testing system analyzes the waveform recording file to obtain the waveform of each voltage and current signal, including the amplitude and sampling time of each sampling point;

[0079] Step S3-2, Result Analysis: The synchronous acquisition performance testing system compares the phase of the actual sampling time point of the recorded waveform with the theoretical phase of the corresponding time point to draw test conclusions;

[0080] The theoretical phase value of the actual sampling time point of the recorded waveform is calculated according to the output of the synchronous tester at the whole second, with each waveform cycle being 20ms long.

[0081] Among them, the phase of the output waveform of the synchronous test system and the waveform of the power distribution terminal under test are calculated by using the full-wave Fourier algorithm, the phase difference between the output waveform of the synchronous test system and the terminal waveform are compared, and the maximum value of the phase difference between the two is used as the performance evaluation index of the synchronous acquisition of the power distribution terminal.

[0082] The specific method is as follows: Figure 3 As shown, firstly, the output waveform with a duration of mT and the terminal waveform are selected at the output waveform sampling time of... The sampling points are then used to calculate the phase angle between the output waveform of the synchronous test system and the waveform of the power distribution terminal under test at the above time points using the full-wave Fourier algorithm. The difference is then compared, and the maximum value of the phase difference between the two is taken as the synchronous acquisition error of the power distribution terminal.

[0083] The full-wave Fourier algorithm is used as follows: assuming a periodic sampled signal x(t) can be decomposed into...

[0084] In the formula, X mn Let α be the amplitude of the nth harmonic component. n Let a be the phase angle of this component at t=0. n and b n These are the amplitudes of the sine and cosine components of each harmonic, respectively.

[0085] Based on the principle of solving for the nth harmonic component using Fourier series and after discretization, the formula is as follows:

[0086] In the formula, T is the period of the fundamental frequency component, w1 is the angular frequency of the fundamental frequency component, and N is the number of sampling points in the period. In the discrete case:

[0087]

[0088] The phase angle of the obtained signal is

[0089]

[0090] Therefore, the synchronous acquisition error of the power distribution terminal under test is

[0091] θ = max{θ1, θ2, ..., θ 4m}=max{|α1-β1|, |α2-β2|,...,|α 4m -β 4m |}

[0092] In the formula, θ k Sampling time point The phase difference α between the target waveform and the terminal waveform k Sampling time point The phase of the target waveform, βk Sampling time point The phase of the test waveform is measured; finally, the maximum phase difference between the target waveform and the test waveform at each of the above sampling time points is taken as the synchronization acquisition error of the power distribution terminal under test.

Claims

1. A method for using a power distribution terminal synchronous acquisition performance test system based on synchronous phasor, which is a power distribution terminal synchronous acquisition performance detection method, characterized in that: Comprising the following steps; Step S1-1, experimental environment building, experimental environment GPS / Beidou signal coverage: place the outdoor signal receiver of the GPS / Beidou signal repeater in an outdoor open area, and connect it with the indoor signal amplifier of the GPS / Beidou signal repeater by wire; Step S1-2, connect the synchronous test system, the power distribution terminal to be tested, and the synchronous acquisition performance detection system: connect the synchronous tester and the power distribution terminal to be tested in parallel in the voltage channel and in series in the current channel; connect the power distribution terminal and the synchronous acquisition performance detection system by using a network cable and an Ethernet switch to ensure normal communication between the power distribution terminal and the synchronous acquisition performance detection system; Step S1-3, set the recording wave trigger condition of the power distribution terminal to be tested: set the recording wave start condition of each power distribution terminal to be tested to ensure that the power distribution terminal can normally record waves when the synchronous test system starts to output electrical quantity signals, and the power distribution terminal does not start recording waves when the synchronous test system does not output signals; if the synchronous acquisition performance test system simultaneously detects multiple power distribution terminals, the recording wave start conditions of all power distribution terminals need to be kept consistent; Step S2 comprises the following steps; Step S2-1, the synchronous test system outputs the test waveform: first set the test waveform that needs to be output by the synchronous test system, and then issue the "start output" instruction; after receiving the instruction, the synchronous test system will start outputting at the next whole second; Step S2-2, the power distribution terminal to be tested triggers the recording wave condition and records the test waveform: after receiving the signal output by the synchronous test system, the recording wave start condition is triggered, and the terminal starts recording, records the waveform at least 80ms before the recording wave trigger time and at least 160ms after the recording wave trigger time, and generates a recording wave file; Step S2-3, the power distribution terminal to be tested uploads the recorded waveform to the synchronous acquisition performance detection system: the power distribution terminal to be tested sends the recording wave file to the synchronous acquisition performance detection system through IEC 101 protocol or IEC 104 protocol; Step S3 Comprising the following steps; Step S3-1, waveform analysis: the synchronous acquisition performance detection system analyzes the recording wave file to obtain the waveform of each voltage and current signal, including the amplitude and sampling time of each sampling point; Step S3-2, result analysis: the synchronous acquisition performance detection system compares the phase of the actual sampling time point of the recording wave waveform with the theoretical phase of the corresponding time point to obtain the test conclusion; The theoretical phase value of the actual sampling time point of the recording wave waveform is calculated according to the start of the output of the synchronous tester at the whole second, and each period of the waveform is 20ms long; The phase of the synchronous test system output waveform and the terminal waveform is calculated respectively by using the full-wave Fourier algorithm, the phase difference between the two is compared, and the maximum value of the phase difference is taken as the evaluation index of the synchronous acquisition performance of the power distribution terminal; The synchronous test system comprises a synchronous tester modified from a relay protection tester, and the functions of the synchronous tester include the functions of the relay protection tester before modification, and further include an output interface capable of ensuring that all output signals start to output at the whole second.

2. The method of claim 1, wherein the method further comprises: The specific method of the full-wave Fourier algorithm is as follows: first, selecting the sampling points of the output waveform and the terminal waveform at the sampling time of the output waveform with a time length of mT, then using the full-wave Fourier algorithm to calculate the phase angles of the output waveform and the terminal waveform at the above time, respectively, and making a difference comparison, and finally taking the maximum value of the phase difference as the synchronization acquisition error of the power distribution terminal. The specific method of the full-wave Fourier algorithm is as follows: first, selecting the sampling points of the output waveform and the terminal waveform at the sampling time of the output waveform with a time length of mT, then using the full-wave Fourier algorithm to calculate the phase angles of the output waveform and the terminal waveform at the above time, respectively, and making a difference comparison, and finally taking the maximum value of the phase difference as the synchronization acquisition error of the power distribution terminal. The method for using the full-wave Fourier algorithm is specifically as follows: assuming a periodic sampled signal x(t), the signal can be decomposed into where X mn is the amplitude of the n-th harmonic component, a n is the phase angle of the component at t = 0, a n and b n are the amplitudes of the sine and cosine components, respectively, of each harmonic. According to the principle of n times frequency component solution by Fourier series and after the discretization processing, the formula is expressed as: In the formula, T is the period of the fundamental frequency component, w1 is the angular frequency of the fundamental frequency component, N is the number of periodic sampling points, and in the discrete case: The phase angle of the signal is The synchronization acquisition error of the power distribution terminal to be tested is θ = max {θ1, θ2,..., θ 4m} = max { |α1-β1|, |α2-β2|,..., |α 4m -β 4m |} wherein θ k is a sampling time point a phase difference between the target waveform and the terminal waveform, α k is a sampling time point a phase of the target waveform, β k is a sampling time point a phase of the test waveform; finally, a maximum value of the phase difference between the target waveform and the test waveform at the sampling time points is taken as the synchronization acquisition error of the power distribution terminal to be tested.

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