CN111458564A - Method and device for synchronizing secondary sampling values of different types of current transformers of generator set - Google Patents

Method and device for synchronizing secondary sampling values of different types of current transformers of generator set Download PDF

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CN111458564A
CN111458564A CN202010288044.4A CN202010288044A CN111458564A CN 111458564 A CN111458564 A CN 111458564A CN 202010288044 A CN202010288044 A CN 202010288044A CN 111458564 A CN111458564 A CN 111458564A
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current
sampling
time
neutral point
generator
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刘军
李重阳
陈创佳
李德华
陆明
王凯
王光
余涛
贺儒飞
李毅
俞家良
李硕
李青
王红星
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Shenzhen Storage Generating Co ltd
China Southern Power Grid Co Ltd
NR Electric Co Ltd
NR Engineering Co Ltd
Electric Power Research Institute of Guangdong Power Grid Co Ltd
Peak and Frequency Regulation Power Generation Co of China Southern Power Grid Co Ltd
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Shenzhen Storage Generating Co ltd
China Southern Power Grid Co Ltd
NR Electric Co Ltd
NR Engineering Co Ltd
Electric Power Research Institute of Guangdong Power Grid Co Ltd
Peak and Frequency Regulation Power Generation Co of China Southern Power Grid Co Ltd
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Priority to CN202010288044.4A priority Critical patent/CN111458564A/en
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R25/00—Arrangements for measuring phase angle between a voltage and a current or between voltages or currents
    • G01R25/005—Circuits for comparing several input signals and for indicating the result of this comparison, e.g. equal, different, greater, smaller, or for passing one of the input signals as output signal
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/175—Indicating the instants of passage of current or voltage through a given value, e.g. passage through zero

Abstract

The invention discloses a method and a device for synchronizing secondary sampling values of different types of current transformers of a generator set. For generator sets with different types of current transformers arranged on the generator end and the neutral point side, synchronous processing of current sampling data is needed when differential protection is formed by secondary current of the generator sets. The method specifically comprises the steps of acquiring secondary current waveforms of a current transformer at a generator end and a current transformer at a neutral point side when a short-circuit characteristic test is carried out on a generator, calculating a phase angle difference of the secondary current waveforms, taking the time difference as an internal curing parameter of the device, and carrying out phase correction on one current sample based on the phase angle difference to achieve a sampling synchronization target. The method does not need to accurately calculate the time delay of each sampling channel, completes the synchronous processing of the sampling values by an experimental method, and is simple and easy to implement.

Description

Method and device for synchronizing secondary sampling values of different types of current transformers of generator set
Technical Field
The invention relates to the field of relay protection of generators, in particular to a method and a device for synchronizing secondary sampling values of different types of current transformers.
Background
For medium-large generator sets, current transformers are arranged on the generator end side and the neutral point side of the generator, and secondary currents of the transformers are led into a protection device to realize complete differential protection. When the installed current transformers are all electromagnetic transformers, the sampling current does not need to be subjected to resynchronization processing in the protection device. However, when the current transformers on the two sides are current transformers with different principles, for example, when one side is an electromagnetic current transformer and the other side is an optical electronic current transformer, the protection device needs to perform resynchronization processing on the current sampling values of the electromagnetic current transformer and the optical electronic current transformer due to different delay characteristics of the sampling loops.
At present, there are two common resynchronization processing methods: one is that an external clock is used for timing a current transformer sampling data processing module, time marks are marked when secondary current data are sent to a protection device, and the protection device performs interpolation resynchronization according to the time marks of current sampling data at different sides; and the other method is that sampling data is uploaded to the protection device by each side current transformer, meanwhile, a sampling channel is also uploaded in a delayed manner, and the protection device performs backspacing interpolation processing on current sampling values of different sides so as to realize resynchronization. Both of the two methods have certain limitations, the first synchronization method depends on an external clock for time setting, and when the clock is abnormal or lost, the protection reliability is directly influenced; the second synchronization method needs to accurately calculate the accumulation of the channel delay of each sampling link of the current transformer, and has complex calculation and high precision requirement.
Disclosure of Invention
The purpose of the invention is: by utilizing the opportunity of the short-circuit characteristic test of the generator set, a simple asynchronous synchronization method is provided for the generator protection device connected with different types of current transformers.
In order to achieve the purpose, the following technical scheme is adopted in the application:
the method for synchronizing the secondary sampling values of different types of current transformers of the generator set comprises the steps that different types of current transformers are arranged on the generator end side and the neutral point side of the generator, and secondary signals of the current transformers are respectively connected into a protection device; the method comprises the following steps:
recording secondary current data of a current transformer at the generator terminal side and the neutral point side of the protection device when the generator performs a short-circuit characteristic test;
converting the phase difference of secondary current data of the current transformers at the computer end side and the neutral point side into a time difference; or the time difference corresponding to the phase difference of the secondary current data of the current transformer at the computer end side and the neutral point side is directly calculated;
and compensating the sampling delay difference of different current channels according to the time difference, and combining a corresponding resampling interpolation algorithm to realize the synchronization of the sampling values of the two current channels.
In a preferred embodiment, the time difference is used as a curing parameter of the protection device.
In a preferred embodiment, the current transformers of different types include: an electromagnetic current transformer, an active electronic current transformer or a passive electronic current transformer.
In a preferred scheme, the method for testing the short-circuit characteristic of the generator comprises the following steps: the generator is short-circuited at the outlet end of the stator three-phase winding at the rated rotating speed, the rotating speed is maintained unchanged, and the excitation current of the generator is gradually increased until the stator current of the generator reaches the rated value.
In a preferred embodiment, the method for phase difference between secondary current data of the current transformer on the computer side and the current transformer on the neutral point side includes: zero crossing point method or fourier phasor method.
In a preferred scheme, the method for synchronizing the secondary sampling values of the current transformers of different types of the generator set according to claim 5 is characterized in that: the zero crossing point method specifically comprises the following steps:
Figure BDA0002449285710000021
in the formula，
Figure BDA0002449285710000022
Is the phase difference; x is the number of0、x1For a certain zero-crossing time t of terminal current signal0Two adjacent sampling values in front and back, and x0≤0，x1Is greater than 0; at t0After the time, the zero-crossing time t at which the neutral point current sampling value changes from negative or zero to positive for the first time1The front and the rear two adjacent sampling values are y0、y1And y is0≤0，y1Is greater than 0; k is terminal current x1Sampling point time and neutral point current y0The number of sampling cycles spaced between sampling point times; f. ofsSampling frequency for the device; f. ofnIs the nominal frequency.
In a preferred embodiment, the zero-crossing point method specifically includes:
Figure BDA0002449285710000023
in the formula (I), the compound is shown in the specification,
Figure BDA0002449285710000024
is the phase difference; x is the number of0、x1For a certain zero-crossing time t of terminal current signal0Two adjacent sampling values in front and back, and x0≥0，x1Less than 0; at t0After the time, the zero-crossing time t at which the neutral point current sampling value changes from positive or zero to negative for the first time1The front and the rear two adjacent sampling values are y0、y1And y is0≥0，y1Less than 0; k is terminal current x1Sampling point time and neutral point current y0The number of sampling cycles spaced between sampling point times; f. ofsSampling frequency for the device; f. ofnIs the nominal frequency.
In a preferred embodiment, the method of converting the phase difference into a time difference comprises:
Figure BDA0002449285710000031
where at is the time difference and at is,
Figure BDA0002449285710000032
is a phase difference of fnIs the nominal frequency.
In a preferred embodiment, the time difference method corresponding to the phase difference between the secondary current data of the current transformer on the direct computer side and the secondary current data of the current transformer on the neutral point side is as follows:
Figure BDA0002449285710000033
wherein Δ t is a time difference, x0、x1For a certain zero-crossing time t of terminal current signal0Two adjacent sampling values in front and back, and x0≤0，x1Is greater than 0; at t0After the time, the zero-crossing time t at which the neutral point current sampling value changes from negative or zero to positive for the first time1The front and the rear two adjacent sampling values are y0、y1And y is0≤0，y1Is greater than 0; k is terminal current x1Sampling point time and neutral point current y0The number of sampling cycles spaced between sampling point times; f. ofsThe device sampling frequency.
In a preferred embodiment, the time difference method corresponding to the phase difference between the secondary current data of the current transformer on the direct computer side and the secondary current data of the current transformer on the neutral point side is as follows:
Figure BDA0002449285710000034
wherein Δ t is a time difference, x0、x1For a certain zero-crossing time t of terminal current signal0Two adjacent sampling values in front and back, and x0≥0，x1Less than 0; at t0After the time, the zero-crossing time t at which the neutral point current sampling value changes from positive or zero to negative for the first time1The front and the rear two adjacent sampling values are y0、y1And y is0≥0，y1Less than 0; k is terminal current x1Sampling point time and neutral point current y0The number of sampling cycles spaced between sampling point times; f. ofsThe device sampling frequency.
In a preferred scheme, the method for synchronizing the secondary sampling values of the current transformers of different types of the generator set according to claim 1 is characterized in that: the resampling interpolation algorithm comprises the following steps: linear interpolation, curve fitting interpolation or quadratic interpolation.
In a preferred embodiment, the quadratic interpolation algorithm specifically includes the following steps:
Figure BDA0002449285710000035
in the formula, [ t ]0,i(t0)]、[t1,i(t1)]、[t2,i(t2)]Three continuous sampling points with equal sampling intervals for terminal current waveform, wherein t is t0+ Δ t, L (t) is the result of the calculation of the sample value at the interpolated sample time t.
The application also provides a corresponding synchronous protection device for secondary sampling values of different types of current transformers of the generator set, wherein different types of current transformers are arranged on the generator end side and the neutral point side of the generator; the protection device includes:
the data acquisition unit is used for acquiring secondary current data of the current transformer at the generator terminal side and the neutral point side of the protection device when the generator performs a short-circuit characteristic test;
the time difference calculation unit is used for calculating the phase difference of secondary current data of the current transformer at the end side and the neutral point side and converting the phase difference into a time difference; or the time difference corresponding to the phase difference of the secondary current data of the current transformer at the computer end side and the neutral point side is directly calculated;
and the synchronization unit is used for compensating the sampling delay difference of different current channels according to the time difference of the time difference calculation unit and realizing the synchronization of the sampling values of the two current channels by combining a corresponding resampling interpolation algorithm.
In a preferred embodiment, the method for phase difference between secondary current data of the current transformer on the computer side and the current transformer on the neutral point side includes: zero crossing point method or fourier phasor method.
In a preferred embodiment, the resampling interpolation algorithm includes: linear interpolation, curve fitting interpolation or quadratic interpolation.
The invention has the beneficial effects that: when a short-circuit test is used, the current of the generator end and the current of the neutral point are close to the rated current, the currents are very large, the primary current is definitely completely synchronous, and the short-circuit current is a high-current calibration source and is used for synchronous calibration. The method does not need to accurately calculate the time delay of each sampling channel, and is simple, reliable and easy to realize by using experimental data to complete the synchronous processing of the current channel sampling values of different types of current transformers.
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Fig. 1 is a first flowchart of an embodiment of a method provided by the present invention.
Fig. 2 is a flow chart of a second embodiment of the method of the present invention.
FIG. 3 is a schematic diagram of the principle of phase difference calculation based on zero crossing, where Δ T is represented in time form of the phase difference, TsAnd n is the number of sampling cycles (n is an integer or decimal) corresponding to the phase difference of the two paths of waveforms.
Fig. 4 is a phase difference calculation method. In the figure, TsFor a sampling period, i +1, j +1 are respectively the sampling point serial numbers before and after the zero crossing point of the A, B signal, TAFor positive half-wave duration, T, within the zero-crossing sampling period of the A signalBThe negative half-wave duration in the sampling period of the zero crossing point of the B signal.
Fig. 5 is a schematic illustration of interpolation. t is t0、t1、t2The three continuous sampling point moments with equal sampling intervals are obtained, and t is the interpolation point moment.
Fig. 6 is a schematic diagram of an embodiment of the apparatus provided by the present invention.
Detailed Description
The invention is further described below with reference to the accompanying drawings:
fig. 1 is a first flowchart of an embodiment of a method provided in the present invention. The generator end side and the neutral point side of the generator are provided with different types of current transformers, and secondary signals of the current transformers are respectively connected into the protection device. Different types of current transformers include: an electromagnetic current transformer, an active electronic current transformer or a passive electronic current transformer.
The method for synchronizing the secondary sampling values of the current transformers of different types of the motor set as shown in FIG. 1 comprises the following steps:
step 1: and recording secondary current data of the current transformer at the generator end side and the neutral point side of the protection device introduced when the generator performs a short-circuit characteristic test.
The method for testing the short-circuit characteristic of the generator comprises the following steps: the generator is short-circuited at the outlet end of the stator three-phase winding at the rated rotating speed, the rotating speed is maintained unchanged, and the excitation current of the generator is gradually increased until the stator current of the generator reaches the rated value.
Step 2: and converting the phase difference of the secondary current data of the current transformer at the computer end side and the neutral point side into a time difference. Preferably, the time difference can be used as a curing parameter for the protective device.
The method for detecting the phase difference of the secondary current data of the current transformer on the computer side and the neutral point side comprises the following steps: zero crossing point method or fourier phasor method.
The method for converting the phase difference into the time difference comprises the following steps:
Figure BDA0002449285710000051
where at is the time difference and at is,
Figure BDA0002449285710000052
is a phase difference of fnIs the nominal frequency.
And step 3: and compensating the sampling delay difference of different current channels according to the time difference, and combining a corresponding resampling interpolation algorithm to realize the synchronization of the sampling values of the two current channels. The resampling interpolation algorithm comprises the following steps: linear interpolation, curve fitting interpolation or quadratic interpolation.
The zero-crossing method described above includes two methods, a positive zero-crossing method and a negative zero-crossing method.
(1) Positive zero crossing method
Figure BDA0002449285710000061
In the formula (I), the compound is shown in the specification,
Figure BDA0002449285710000062
is the phase difference; x is the number of0、x1For a certain zero-crossing time t of terminal current signal0Two adjacent sampling values in front and back, and x0≤0，x1Is greater than 0; at t0After the time, the zero-crossing time t at which the neutral point current sampling value changes from negative or zero to positive for the first time1The front and the rear two adjacent sampling values are y0、y1And y is0≤0，y1Is greater than 0; k is terminal current x1Sampling point time and neutral point current y0The number of sampling cycles spaced between sampling point times; f. ofsSampling frequency for the device; f. ofnIs the nominal frequency.
(2) Negative zero crossing method
Figure BDA0002449285710000063
In the formula (I), the compound is shown in the specification,
Figure BDA0002449285710000064
is the phase difference; x is the number of0、x1For a certain zero-crossing time t of terminal current signal0Two adjacent sampling values in front and back, and x0≥0，x1Less than 0; at t0After the time, the zero-crossing time t at which the neutral point current sampling value changes from positive or zero to negative for the first time1The front and the rear two adjacent sampling values are y0、y1And y is0≥0，y1Less than 0; k is terminal current x1Sampling point time and neutral point current y0The number of sampling cycles spaced between sampling point times; f. ofsSampling frequency for the device; f. ofnIs the nominal frequency.
The quadratic interpolation algorithm is specifically as follows:
Figure BDA0002449285710000065
in the formula, [ t ]0,i(t0)]、[t1,i(t1)]、[t2,i(t2)]Three continuous sampling points with equal sampling intervals for terminal current waveform, wherein t is t0+ Δ t, L (t) is the result of the calculation of the sample value at the interpolated sample time t.
Step 2 of example 1 is modified as shown in the flow chart two of the method example of fig. 2. The method specifically comprises the following steps:
step 21: and recording secondary current data of the current transformer at the generator end side and the neutral point side of the protection device introduced when the generator performs a short-circuit characteristic test.
Step 22: and directly calculating the time difference corresponding to the phase difference of the secondary current data of the current transformer at the end side and the neutral point side. Preferably, the time difference can be used as a curing parameter for the protective device.
The method for directly calculating the time difference according to the sampling points by adopting a zero-crossing method comprises the following two steps:
the method comprises the following steps:
Figure BDA0002449285710000071
wherein Δ t is a time difference, x0、x1For a certain zero-crossing time t of terminal current signal0Two adjacent sampling values in front and back, and x0≤0，x1Is greater than 0; at t0After the time, the zero-crossing time t at which the neutral point current sampling value changes from negative or zero to positive for the first time1The front and the rear two adjacent sampling values are y0、y1And y is0≤0，y1Is greater than 0; k is terminal current x1Sampling point time and neutral point current y0The number of sampling cycles spaced between sampling point times; f. ofsThe device sampling frequency.
The second method comprises the following steps:
Figure BDA0002449285710000072
wherein Δ t is a time difference, x0、x1For a certain zero-crossing time t of terminal current signal0Two adjacent sampling values in front and back, and x0≥0，x1＜0；At t0After the time, the zero-crossing time t at which the neutral point current sampling value changes from positive or zero to negative for the first time1The front and the rear two adjacent sampling values are y0、y1And y is0≥0，y1Less than 0; k is terminal current x1Sampling point time and neutral point current y0The number of sampling cycles spaced between sampling point times; f. ofsThe device sampling frequency.
Step 23: and compensating the sampling delay difference of different current channels according to the time difference, and combining a corresponding resampling interpolation algorithm to realize the synchronization of the sampling values of the two current channels.
The third embodiment is described in more detail below with reference to fig. 3, 4 and 5: during generator short circuit characteristic test, stator three-phase winding is short circuited, increases the unit excitation, when stator current risees to rated current, manual or automatic start record ripples on protection device, then does the analysis calculation to terminal current in the waveform and neutral point current channel waveform data:
since the two paths of current are secondary currents of different current transformers, a certain phase difference inevitably exists, and a schematic diagram of the phase difference is shown in fig. 3. The purpose of this step calculation is to calculate Δ t in the graph. The specific calculation method is as follows:
as shown in fig. 4, first, two current waveforms (assuming that a signal is a generator-side current waveform and B signal is a neutral-point current waveform) are found respectively, which have similar zero-crossing points (from negative to positive) in time sequence, the serial numbers of two sampling points before and after the zero-crossing point of the generator-side current are i and i +1, respectively, and the corresponding sampling values are x0And x1The serial numbers of two sampling points before and after the zero crossing point of the current of the neutral point are respectively j and j +1, and the corresponding sampling values are respectively y0And y1. Therefore, the method of calculating the time difference Δ t corresponding to the phase difference between the two waveforms is:
Figure BDA0002449285710000081
in the formula, K is the sampling period number spaced between the sampling point time of terminal current i +1 and the sampling point time of neutral point current j,i.e., K ═ j- (i + 1); f. ofsThe device sampling frequency.
Suppose K is 1, fs＝2400，x0＝-0.04，x1＝0.12，y0＝-0.1，y1When the value is 0.05, the calculation result is:
Figure BDA0002449285710000082
according to the calculation method, the adjacent zero-crossing points of the current channels at the end and the neutral point are calculated to obtain a group of calculation result sequences, such as 0.001007s, 0.0010008s, 0.001009s and … …. Calculating the average value of the calculated value sequence to obtain delta tmean。
Will be Δ tmeanThe method is used for compensating the sampling delay difference of different current channels and realizing the synchronization of the sampling values of the two current channels by combining with a corresponding resampling interpolation algorithm. The interpolation method can adjust the phases of the current of the machine end and the current of the neutral point at the same time, and interpolate the current of the machine end and the current of the neutral point respectively to obtain respective new sampling value sequences. Or adjusting the phase of the current at the terminal and calculating a new sampling point sequence by interpolation by taking the current at the neutral point as a reference.
Taking the neutral point current as a reference, the adopted resampling interpolation algorithm can adopt a linear interpolation method or a secondary interpolation algorithm, and the secondary interpolation algorithm is adopted in consideration of the interpolation calculation precision as follows:
Figure BDA0002449285710000083
wherein t is t1-Δtmean，[t0,i(t0)]、[t1,i(t1)]、[t2,i(t2)]L (t) is the calculation result of the sampling value in the new sampling sequence, and the serial number of the sampling value corresponds to t of the current waveform of the neutral point1The sampled values at the time are as shown in fig. 5.
This application has proposed synchronous protection device embodiment of corresponding generating set different grade type current transformer secondary sampling value simultaneously, includes as shown in fig. 6:
the data acquisition unit is used for acquiring secondary current data of the current transformer at the generator terminal side and the neutral point side of the protection device when the generator performs a short-circuit characteristic test;
the time difference calculation unit is used for calculating the phase difference of secondary current data of the current transformer at the end side and the neutral point side and converting the phase difference into a time difference; or the time difference corresponding to the phase difference of the secondary current data of the current transformer at the computer end side and the neutral point side is directly calculated;
and the synchronization unit is used for compensating the sampling delay difference of different current channels according to the time difference of the time difference calculation unit and realizing the synchronization of the sampling values of the two current channels by combining a corresponding resampling interpolation algorithm.
In a preferred embodiment, the method for phase difference between secondary current data of the current transformer on the computer side and the current transformer on the neutral point side includes: zero crossing point method or fourier phasor method.
In a preferred embodiment, the resampling interpolation algorithm includes: linear interpolation, curve fitting interpolation or quadratic interpolation.
The above embodiments are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modifications made on the basis of the technical scheme according to the technical idea of the present invention fall within the protection scope of the present invention.

Claims (15)

1. The method for synchronizing the secondary sampling values of different types of current transformers of the generator set is characterized by comprising the following steps: different types of current transformers are arranged on the generator end side and the neutral point side of the generator, and secondary signals of the current transformers are respectively connected into the protection device; the method comprises the following steps:
recording secondary current data of a current transformer at the generator terminal side and the neutral point side of the protection device when the generator performs a short-circuit characteristic test;
converting the phase difference of secondary current data of the current transformers at the computer end side and the neutral point side into a time difference; or the time difference corresponding to the phase difference of the secondary current data of the current transformer at the computer end side and the neutral point side is directly calculated;
and compensating the sampling delay difference of different current channels according to the time difference, and combining a corresponding resampling interpolation algorithm to realize the synchronization of the sampling values of the two current channels.
2. The method for synchronizing the secondary sampling values of the current transformers of different types of the generator set according to claim 1, is characterized in that: and taking the time difference as a curing parameter of the protection device.
3. The method for synchronizing the secondary sampling values of the current transformers of different types of the generator set according to claim 1, is characterized in that: the different types of current transformers include: an electromagnetic current transformer, an active electronic current transformer or a passive electronic current transformer.
4. The method for synchronizing the secondary sampling values of the current transformers of different types of the generator set according to claim 1, is characterized in that: the method for testing the short-circuit characteristic of the generator comprises the following steps: the generator is short-circuited at the outlet end of the stator three-phase winding at the rated rotating speed, the rotating speed is maintained unchanged, and the excitation current of the generator is gradually increased until the stator current of the generator reaches the rated value.
5. The method for synchronizing the secondary sampling values of the current transformers of different types of the generator set according to claim 1, is characterized in that: the method for phase difference of secondary current data of the current transformer on the computer side and the neutral point side comprises the following steps: zero crossing point method or fourier phasor method.
6. The method for synchronizing the secondary sampling values of the current transformers of different types of the generator set according to claim 5, wherein the method comprises the following steps: the zero crossing point method specifically comprises the following steps:
Figure FDA0002449285700000021
in the formula (I), the compound is shown in the specification,
Figure FDA0002449285700000022
is the phase difference; x is the number of0、x1For a certain zero-crossing time t of terminal current signal0Two adjacent sampling values in front and back, and x0≤0，x1Is greater than 0; at t0After the time, the zero-crossing time t at which the neutral point current sampling value changes from negative or zero to positive for the first time1The front and the rear two adjacent sampling values are y0、y1And y is0≤0，y1Is greater than 0; k is terminal current x1Sampling point time and neutral point current y0The number of sampling cycles spaced between sampling point times; f. ofsSampling frequency for the device; f. ofnIs the nominal frequency.
7. The method for synchronizing the secondary sampling values of the current transformers of different types of the generator set according to claim 5, wherein the method comprises the following steps: the zero crossing point method specifically comprises the following steps:
Figure FDA0002449285700000023
in the formula (I), the compound is shown in the specification,
Figure FDA0002449285700000024
is the phase difference; x is the number of0、x1For a certain zero-crossing time t of terminal current signal0Two adjacent sampling values in front and back, and x0≥0，x1Less than 0; at t0After the time, the zero-crossing time t at which the neutral point current sampling value changes from positive or zero to negative for the first time1The front and the rear two adjacent sampling values are y0、y1And y is0≥0，y1Less than 0; k is terminal current x1Sampling point time and neutral point current y0The number of sampling cycles spaced between sampling point times; f. ofsSampling frequency for the device; f. ofnIs the nominal frequency.
8. The method for synchronizing the secondary sampling values of the current transformers of different types of the generator set according to claim 1, is characterized in that: the method for converting the phase difference into the time difference comprises the following steps:
Figure FDA0002449285700000025
where at is the time difference and at is,
Figure FDA0002449285700000026
is a phase difference of fnIs the nominal frequency.
9. The method for synchronizing the secondary sampling values of the current transformers of different types of the generator set according to claim 1, is characterized in that: the time difference method corresponding to the phase difference of the secondary current data of the current transformer at the end side of the direct computer and the neutral point side comprises the following steps:
Figure FDA0002449285700000027
wherein Δ t is a time difference, x0、x1For a certain zero-crossing time t of terminal current signal0Two adjacent sampling values in front and back, and x0≤0，x1Is greater than 0; at t0After the time, the zero-crossing time t at which the neutral point current sampling value changes from negative or zero to positive for the first time1The front and the rear two adjacent sampling values are y0、y1And y is0≤0，y1Is greater than 0; k is terminal current x1Sampling point time and neutral point current y0The number of sampling cycles spaced between sampling point times; f. ofsThe device sampling frequency.
10. The method for synchronizing the secondary sampling values of the current transformers of different types of the generator set according to claim 1, is characterized in that: the time difference method corresponding to the phase difference of the secondary current data of the current transformer at the end side of the direct computer and the neutral point side comprises the following steps:
Figure FDA0002449285700000031
wherein Δ t is a time difference, x0、x1For a certain zero-crossing time t of terminal current signal0Two adjacent sampling values in front and back, and x0≥0，x1Less than 0; at t0After the time, the zero-crossing time t at which the neutral point current sampling value changes from positive or zero to negative for the first time1The front and the rear two adjacent sampling values are y0、y1And y is0≥0，y1Less than 0; k is terminal current x1Sampling point time and neutral point current y0The number of sampling cycles spaced between sampling point times; f. ofsThe device sampling frequency.
11. The method for synchronizing the secondary sampling values of the current transformers of different types of the generator set according to claim 1, is characterized in that: the resampling interpolation algorithm comprises the following steps: linear interpolation, curve fitting interpolation or quadratic interpolation.
12. The method for synchronizing the secondary sampling values of the current transformers of different types of the generator set according to claim 11, wherein the method comprises the following steps: the quadratic interpolation algorithm is specifically as follows:
Figure FDA0002449285700000032
in the formula, [ t ]0,i(t0)]、[t1,i(t1)]、[t2,i(t2)]Three continuous sampling points with equal sampling intervals for terminal current waveform, wherein t is t0+ Δ t, L (t) is the result of the calculation of the sample value at the interpolated sample time t.
13. The generator set comprises a generator set, a generator end side and a neutral point side, wherein the generator end side and the neutral point side are provided with different types of current transformers; the method is characterized in that: the protection device includes:
the data acquisition unit is used for acquiring secondary current data of the current transformer at the generator terminal side and the neutral point side of the protection device when the generator performs a short-circuit characteristic test;
the time difference calculation unit is used for calculating the phase difference of secondary current data of the current transformer at the end side and the neutral point side and converting the phase difference into a time difference; or the time difference corresponding to the phase difference of the secondary current data of the current transformer at the computer end side and the neutral point side is directly calculated;
and the synchronization unit is used for compensating the sampling delay difference of different current channels according to the time difference of the time difference calculation unit and realizing the synchronization of the sampling values of the two current channels by combining a corresponding resampling interpolation algorithm.
14. The synchronous protection device for the secondary sampling values of the current transformers of different types of the generator set according to claim 13, is characterized in that: the method for phase difference of secondary current data of the current transformer on the computer side and the neutral point side comprises the following steps: zero crossing point method or fourier phasor method.
15. The synchronous protection device for the secondary sampling values of the current transformers of different types of the generator set according to claim 13, is characterized in that: the resampling interpolation algorithm comprises the following steps: linear interpolation, curve fitting interpolation or quadratic interpolation.
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