CN116165427B - Power distribution low-voltage transformer area topology signal identification circuit and identification method - Google Patents
Power distribution low-voltage transformer area topology signal identification circuit and identification method Download PDFInfo
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Abstract
The invention discloses a topology signal identification circuit and an identification method for a distribution low-voltage transformer area, and relates to the technical field of low-voltage distribution systems, wherein the circuit comprises three open-close type current transformers respectively matched with three-phase currents of a tested end, a small current transformer respectively connected with the three open-close type current transformers, an AD module and a CPU module; three-phase currents of the tested end are respectively connected to the primary sides of three open-close type current transformers, the secondary sides of the open-close type current transformers are connected to the primary sides of corresponding small current transformers, the secondary sides of the three small current transformers are connected into a current sum mode through parallel connection, the current sum mode is connected to an AD module, the AD module is electrically connected with a CPU module through an SPI bus, and collected signals are subjected to differential value, filtering, window function Fourier transformation and the like through the CPU module, so that identification of topological signals of a distribution low-voltage station area with low cost, high reliability and accuracy and high practicability is achieved.
Description
Technical Field
The invention relates to the technical field of low-voltage power distribution systems, in particular to a power distribution low-voltage transformer area topology signal identification circuit and an identification method.
Background
In an electric power system, a bay refers to a power supply range or area of one transformer, and a low-voltage bay generally refers to a power supply range or area from a low-voltage side of one transformer to a user electricity meter side of its final service, in which a large number of electric devices such as overhead lines, cables, transformers, circuit breakers, electricity meters, sensors, and the like are contained, and a large number of carrier facilities for housing the electric devices such as a box transformer, a JP cabinet (i.e., a compensation distribution cabinet for a low-voltage distribution system), a branch box, a meter box, and the like. The topology of the power line of the low-voltage area of the power equipment and the carrier facility can accurately and truly reflect the connection relation in the low-voltage area, and is important for the power management department to improve the power supply reliability management level and the power supply service capability.
Considering that the distribution low-voltage transformer areas are wide in distribution, large in quantity and complex in electrical connection, especially for old communities and remote areas, due to historical reasons, irregular electrical connection exists, and the electrical topology condition of the distribution low-voltage transformer areas is difficult to accurately grasp. In recent years, with the increase of investment of a power distribution network, the degree of automation of a low-voltage distribution area is developed to a certain extent, however, if work such as line loss analysis, area heavy load management, fault positioning and rush repair is performed, accurate area electric topology information needs to be acquired. Therefore, the accurate topological relation of the transformer area has important significance for information acquisition, operation and maintenance of the power system.
At present, the existing topology identification technology of the distribution low-voltage transformer area generally adopts a small current injection method which is widely applied and has higher accuracy, namely a signal transmitting end injects a 833.3Hz topology characteristic current signal into a low-voltage distribution system, and whether a tested end can detect the topology characteristic current signal is used as a basis of whether a topological relation exists between the tested end and the signal transmitting end or not, so that the topology identification of the distribution low-voltage transformer area is realized. However, the existing identification circuit and identification method for the topological characteristic current signal (i.e. topological signal) of the distribution low-voltage area have the following problems:
(1) The device is expensive and has high cost. The topological characteristic current signal injected into the low-voltage distribution system is limited by factors such as device capacity, device heating, incapability of influencing the operation of the low-voltage distribution system and the like, and the signal amplitude is smaller and is generally within 0.5A. Under the condition of larger primary side load current, in order to accurately detect topological characteristic current signals, a high-precision 24-bit AD chip is generally adopted for signal acquisition processing. Since it is not possible to predict which phase the transmitting end is in, each current channel needs to use a 24-bit AD chip to acquire signals, i.e. a 24-bit AD chip having at least 3 acquisition channels is required. However, the 24-bit AD chip containing at least 3 channels is very expensive, and meanwhile, because the data volume required for calculating and analyzing the topology signals is very large, the requirement on the calculation capacity of the CPU is high, and a high-performance CPU is also required to be specially configured for collecting and calculating the related information of the topology signals in the design process;
(2) The signal processing algorithm has weak anti-interference capability. The conventional method for injecting the topological characteristic current signals of 833.3Hz into the power grid of the distribution low-voltage transformer area by using a small current injection method can generate two topological characteristic current signals of 783.3Hz and 883.3Hz after the power grid frequencies are overlapped. The characteristics of unbalanced three phases, large load fluctuation and the like of the low-voltage distribution system are very outstanding, and the characteristics of directivity, intermittence, mutation, rich harmonic and the like of tide are more outstanding due to the fact that distributed photovoltaic is introduced into part of distribution low-voltage areas in recent years, so that collected signals need to be processed. At present, a rectangular long data window is generally used to calculate a modulus value of any one of two characteristic frequencies through discrete fourier transform (Discrete Fourier Transform, DFT) so as to determine whether a topological relation exists between a tested end and a signal transmitting end. However, it is found that when large electric equipment is turned on and harmonic and inter-harmonic signals with close frequencies are generated, calculation of output topological characteristic current signal modulus values is affected, and larger errors may be caused, so that topology identification of a distribution low-voltage area fails.
Disclosure of Invention
In order to solve the problems still existing in the existing distribution low-voltage transformer area topology signal acquisition circuit, the invention provides a distribution low-voltage transformer area topology signal identification circuit and an identification method, and identification of topology characteristic current signals with low cost, high reliability and accuracy and strong practicability is realized.
To achieve the above object, one or more embodiments of the present invention provide the following technical solutions:
the invention provides a topology signal identification circuit for a distribution low-voltage transformer area.
A topology signal identification circuit for a distribution low voltage station, comprising: three open-close type current transformers respectively matched with three-phase current of a tested end, a small current transformer respectively connected with the three open-close type current transformers, an AD module and a CPU module;
three-phase current of the tested end is respectively connected to the primary sides of three open-close type current transformers, the secondary sides of the open-close type current transformers are connected to the primary sides of corresponding small current transformers, and after the secondary sides of the three small current transformers are connected into a current sum mode in parallel, the current sum mode is connected to an AD module which is electrically connected with the CPU module through an SPI bus.
According to a further technical scheme, the open-close type current transformer adopts an open iron core structural design, cables of a certain phase at a tested end are sleeved in a centralized mode through an inner hole, rated current of the primary side of the open-close type current transformer is selected according to actual load size, and rated current of the secondary side of the open-close type current transformer is 5A.
According to a further technical scheme, the AD module comprises a 24-bit AD chip with a single channel and is used for converting the acquired analog topology characteristic current signals into digital topology characteristic current signals.
According to a further technical scheme, the CPU reads 24-bit sampling data of a single channel in the AD module and is used for processing the sampled value of the read topological characteristic current signal.
According to a further technical scheme, the processing of the sampled value of the read topological characteristic current signal comprises the following steps:
updating the sampling sequence of the topological characteristic current signal of the current sampling period through the linear difference value;
the updated topological characteristic current signal sampling sequences are respectively filtered through two narrow-band bandpass filters with different passband, and two sampling sequences are respectively obtained;
respectively passing the two acquired sampling sequences through a hanning window to obtain a final sampling sequence;
and performing Fourier transformation on the two obtained final sampling sequences respectively, and calculating to obtain the modulus of the topological characteristic current signal.
According to a further technical scheme, the two narrow-band-pass FILTERs are a first digital FILTER FILTER1 and a second digital FILTER FILTER2 respectively, and the passband of the first digital FILTER FILTER1 isThe passband of the second digital FILTER2 is, wherein ,/>For the transmission frequency of the topology signal, < > for>For AD sampling frequency, +.>Is the rated frequency of the power grid.
Further technical proposal, acquiring a sampling sequence of the current sampling periodSampling sequence for the current sampling period by means of a linear difference +.>Updating to obtain updated sampling sequence +.>Sampling sequence->After passing the first digital FILTER1 and the second digital FILTER2, respectively, a sampling sequence is obtained +.>Andtwo sampling sequences to be acquired +.> and />Respectively multiplying the obtained values with the corresponding values of the hanning windows to obtain the most significantFinal sampling sequence->、/>The multiplication is as follows:
；
；
wherein ,for the sequence number in the data window, +.>=0,1,2,…,N-1，NIs the data window length.
Further technical scheme still includes:
and judging whether a topological relation exists between the tested end and the topological signal transmitting end based on the high-low and high-low change rules of the topological characteristic current signal module value of each sampling period, and completing the identification of the topological signal.
The second aspect of the invention provides a method for identifying topology signals of a distribution low-voltage transformer area.
A topology signal identification method for a distribution low-voltage area comprises the following steps:
collecting three-phase current sums of a tested end, and obtaining a topological characteristic current signal detected by the tested end through analog-to-digital conversion;
processing the topological characteristic current signal of each sampling period to obtain a module value of the topological characteristic current signal of each sampling period;
and judging whether a topological relation exists between the tested end and the topological signal transmitting end based on the high-low and high-low change rules of the topological characteristic current signal module value of each sampling period, and completing the identification of the topological signal.
According to a further technical scheme, the processing of the topological characteristic current signal of each sampling period comprises the following steps:
updating the sampling sequence of the topological characteristic current signal of the current sampling period through the linear difference value;
the updated topological characteristic current signal sampling sequences are respectively filtered through two narrow-band bandpass filters with different passband, and two sampling sequences are respectively obtained;
respectively passing the two acquired sampling sequences through a hanning window to obtain a final sampling sequence;
and performing Fourier transformation on the two obtained final sampling sequences respectively, and calculating to obtain the modulus of the topological characteristic current signal.
The one or more of the above technical solutions have the following beneficial effects:
(1) The power distribution low-voltage transformer area topology signal identification circuit and the identification method provided by the invention realize identification of topology characteristic current signals with low cost, high reliability and accuracy and strong practicability.
(2) In the invention, each phase of small current transformer used for collecting topology signals is connected into a current sum form, and under the three-phase symmetrical condition, the power frequency signal and the integer harmonic signal are mutually counteracted to be zero, so that the topology characteristic current signal is reserved, and the anti-interference capability of the topology signal identification circuit is improved; meanwhile, no matter which phase the topological characteristic current signal transmitting end is in, the current and the form can be sensed, therefore, only a 24-bit AD chip with a single-channel acquisition channel is used, the requirements of acquisition and calculation of single-channel 24-bit AD data on the memory and the calculation capability of a CPU are greatly reduced, the CPU for acquisition and calculation of topological signals is not required to be specially configured, and the cost and the board layout area are greatly reduced.
(3) In the invention, the current period sampling sequence is subjected to difference value operation based on the current period and the last period sampling sequence, and steady-state or little-change fundamental waves and integer harmonics can be partially filtered or mostly filtered, so that the influence of the fundamental waves and integer harmonics on a final calculation result is weakened, and the identification accuracy is improved.
(4) The most important point of topology identification of the distribution low-voltage transformer area is accuracy rather than rapidity, and the frequency of a topology signal is known in advance, so that irrelevant frequency components are removed by designing a narrow-band bandpass filter, and the accuracy of data is improved although the processing time is increased; meanwhile, the Hanning window (namely the hanning window) is added to the sampling data instead of the common rectangular window, so that the frequency spectrum leakage is reduced, and the attenuation speed of irrelevant frequency components is improved; considering that the signals of the two frequency components finally obtained are part of the characteristic topological signal, the amplitude of the topological signal is more accurately represented by the root mean square of the modulus values of the two frequency components after Fourier transformation, so that the accuracy of topology identification is ensured.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
Fig. 1 is a schematic structural diagram of a topology signal identification circuit for a distribution low-voltage transformer area according to an embodiment of the present invention;
fig. 2 is a flowchart of a method for performing topology signal processing by a CPU module according to a first embodiment of the present invention.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present invention. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.
Example 1
In order to solve the problems of high cost, weak anti-interference capability and poor compatibility of the existing topology signal acquisition and identification circuit of the distribution low-voltage transformer area, the embodiment discloses a topology signal identification circuit of the distribution low-voltage transformer area, as shown in fig. 1, comprising: three open-close type current transformers respectively matched with three-phase current of a tested end, a small current transformer respectively connected with the three open-close type current transformers, an AD module and a CPU module;
three-phase current of the tested end is respectively connected to the primary sides of three open-close type current transformers, the secondary sides of the open-close type current transformers are connected to the primary sides of corresponding small current transformers, and after the secondary sides of the three small current transformers are connected into a current sum mode in parallel, the current sum mode is connected to an AD module which is electrically connected with the CPU module through an SPI bus.
In this embodiment, each phase of the three-phase current of the tested end is configured with an open-close current transformer, that is, the tested end includes A, B, C three-phase tested cables, the three open-close current transformers all adopt an open core structure design, cables of a certain phase of the tested end are sleeved in a centralized manner through the inner hole, the open-close current transformers can be quickly and conveniently installed and removed without disconnecting the tested cables, and the current collection is convenient and safe.
The current of the tested end is connected to the primary side of the open-close type current transformer, the rated current of the primary side of the open-close type current transformer is selected according to the actual load size, a certain margin is reserved, and 250A, 400A or 600A is generally selected; the rated current of the secondary side of the open-close type current transformer is 5A, so that the open-close type current transformer is convenient to adapt to other devices in the acquisition and identification circuit, and is also convenient to be compatible with the acquisition and identification devices provided by different manufacturers.
Configuring small current transformers connected with the three open-close type current transformers respectively, wherein the secondary side of each open-close type current transformer is connected with the primary side of the corresponding small current transformer, and the specification of the small current transformer is 5A:2.5mA. The secondary side of the first small current transformer of each phase then receives the form of a current sum, i.e+/>+/>And then accessing the AD module.
In the above scheme, since the total current in the parallel circuit is equal to the sum of the current of each branch, the secondary sides of the three small current transformers are connected in parallel at D, E points to form a current sum, and then are connected into the AD module. The secondary side of the three-phase second small current transformer receives current and form, i.e+/>+/>, wherein ,/>The current of the secondary side of the small current transformer corresponding to the tested end A is +.>For the current of the secondary side of the small current transformer corresponding to the tested end B, +.>The current of the secondary side of the small current transformer corresponding to the tested end C. If the load is balanced and there is no characteristic current, then +.>=0; if the load is balanced and there is a characteristic current, then +.>Is equal to the characteristic current value. Therefore, the method filters out the fundamental wave and integer harmonic component of the power frequency well, and improves the reliability and anti-interference capability of the characteristic current detection。
Meanwhile, the secondary sides of the three small current transformers are connected with current and form, no matter which phase the sending end is in which phase the topological characteristic current signal is injected, the current and form can be obtainedTherefore, the current and the analog quantity are connected into an AD module (analog quantity input module), the AD module only needs to configure a 24-bit AD chip with one channel to carry out analog-to-digital conversion of the topological characteristic current signal, namely, the AD module comprises a 24-bit AD chip with a single channel, the acquired analog topological characteristic current signal is converted into a digital topological characteristic current signal through the AD module and then is input into a CPU module, the CPU reads the sampling data of the AD through a high-speed SPI bus (SPI, serialPeripheral interface, serial peripheral interface), and the CPU only needs to read and operate the 24-bit AD data of one channel, so that the requirements on hardware configuration and calculation capability of the CPU are greatly reduced, even a special CPU for collecting and calculating the topological signal is not needed, and the cost and the board arrangement complexity are greatly saved.
As another implementation mode, the distribution low-voltage transformer area topology signal recognition device is formed based on a distribution low-voltage transformer area topology signal recognition circuit, wherein a small current transformer, an AD module and a CPU module can be arranged inside the device, and an open-close type current transformer which is respectively and electrically connected with the small current transformer is arranged outside the device.
In the CPU module, the input topological characteristic current signal is processed, and the topological identification of the distribution low-voltage transformer area is realized based on the comparison of the module value of the topological characteristic current signal and the topological characteristic current signal injected by the signal transmitting end.
Specifically, the CPU module processes a sampling value of an input topology characteristic current signal, as shown in fig. 2, and specifically includes the following steps:
and S1, updating a sampling sequence of the topological characteristic current signal in the current sampling period through the linear difference value. Specifically, a sampling sequence of the current sampling period is obtainedAnd the sampling sequence of the last sampling period +.>Updating the sampling sequence corresponding to the current sampling period to +.>，kRepresenting the sampling point and at the same time the sampling sequence of the current sampling period before updating +.>The value of (2) is assigned to the sampling sequence of the last sampling period +.>To update the sampling sequence of the last sampling period>. In this embodiment, the sampling frequency of the topology signal injected from the signal transmitting terminal is set5000Hz, i.e. 5000 points per second, then at the rated frequency of the grid of 50Hz, the number of sampling points per weekly wave +.>=5000/50=100, at this time, a FIFO buffer may be set to buffer a certain number of sample values, and at the nominal frequency, the sample sequence value at the current time is +.>The 100 points are the sampling sequence value of the sampling time corresponding to the last cycle>. If the three phases of the three-phase load are unbalanced and steady, the influence of the power frequency and integer harmonic signals on the final calculated value can be weakened by utilizing the difference value, and the topological characteristic current signal is not an integer multiple of the power grid frequency, so that the information of the topological characteristic current signal is not influenced by the difference value operation.
However, the load of the low-voltage power distribution system is complex and variable, and the characteristic frequency value of the topology signal is very obvious: because the topology characteristic current signal of 833.3Hz is superimposed into the grid rated at 50Hz, two characteristic frequencies will be produced with the grid frequency unchanged: 833.3+50= 883.3Hz and 833.3-50= 783.3Hz. Since the grid frequency generally fluctuates between 45 and 55Hz, but in practice there is little variation around 50 Hz. From the above analysis, in the present embodiment, by providing a narrow band pass filter in software, information in the vicinity of both the 883.3Hz and 783.3Hz bands is retained, while all other information is filtered out.
And S2, respectively filtering the updated topological characteristic current signal sampling sequences through two narrow-band bandpass filters with different passband, and respectively obtaining two sampling sequences. Specifically, the two narrowband band-pass FILTERs are digital narrowband band-pass FIR FILTERs, the FIR (FiniteImpulse Response) FILTER is a finite length unit impulse response FILTER, and in order to distinguish the two narrowband band-pass FILTERs, the two narrowband band-pass FILTERs are divided into a first digital FILTER1 and a second digital FILTER2, that is, the two narrowband band-pass FILTERs are respectively the first digital FILTER1 and the second digital FILTER2. The passband of the first digital FILTER1 isThe passband of the second digital FILTER2 is +.>, wherein ,/>For the transmission frequency of the topology signal, < > for>For AD sampling frequency, +.>Is the rated frequency of the power grid. Although adding a narrow band pass filter for filtering increases the time cost, topology identification is not a frequent occurrence for the identification deviceEvents, and the accuracy of topology identification is much more important than efficiency.
Then, considering that the computing power and memory space of the embedded real-time CPU are at a premium, the computation must be performed by truncating a sequence of samples of a certain length. The rectangular window adopted in the prior art is simplest and most widely applied, but is inferior in side lobe amplitude and stop band attenuation speed under the condition of the same window length, so that frequency spectrum leakage and data distortion are easier to cause, and therefore, the rectangular window is replaced by a hanning window (one of Hanning window and window functions), the effect is better, the hardware resource cost is low, and the calculation speed is hardly influenced.
And step S3, respectively passing the two acquired sampling sequences through a hanning window (i.e. a hanning window) to obtain a final sampling sequence. In particular, the method comprises the steps of,after passing through the first digital FILTER1 the sampling sequence is obtained +.>After passing through the second digital FILTER2, a sampling sequence is obtained>Two sampling sequences to be acquired +.>、Multiplying the sample with the corresponding value of the hanning window to obtain the final sampling sequence +.>、/>The multiplication refers to:
；
；
wherein ,for the sequence number in the data window, +.>=0,1,2,…,N-1，NIs the data window length.
And after the linear difference value, the narrow-band bandpass filtering and the hanning window are optimized, executing a step S4, respectively carrying out Fourier transform on the two obtained final sampling sequences, calculating to obtain a module value of the topological characteristic current signal, and comparing the module value of the output topological characteristic current signal with the topological characteristic current signal injected by the signal transmitting end to realize the topological identification of the distribution low-voltage station area.
Specifically, for two final sample sequences obtained、/>Respectively pass through two characteristic frequencies as+/>、/>-/>And the lengths (i.e. the lengths of the above indicated data windows) are all Fourier transforms of N, respectively calculating the corresponding signal modulus +.>Sum signal modulus->Both of these modulus values are used to characterize the topology signal, and therefore the total modulus value of the topology-characterized current signal is calculated>And outputting the total module value as the final module value of the topological characteristic current signal.
After the calculation is completed, the sampling sequence with the length of N is sampled and />And (3) emptying, and carrying out the calculation again after the sampling sequence of the topological characteristic current signal is accumulated again to be N in length. Through the program built in the CPU, the matching degree of the current signal module value and the signal injection signal of the signal sending end is distinguished based on the high-low and high-low change rule of the topological characteristic current signal module value of each sampling period output by the tested end obtained for a long time, and whether the tested end and the signal sending end have a topological relation is judged.
Specifically, the signal transmitting end transmits a plurality of topological characteristic current signals with the same time length, and the tested end obtains the modulus of the topological characteristic current signals with the corresponding time length. If the module value of the topological characteristic current signal obtained at the two frequencies of 783.3Hz and 883.3Hz is larger in each time length, if the module value obtained by calculation is larger than a first set value, the topological relation exists between the transmitting end and the tested end, wherein the first set value is 90% of the module value of the topological characteristic current signal sent by the signal transmitting end; otherwise, if the module value of the topological characteristic current signal obtained at the two frequencies of 783.3Hz and 883.3Hz is extremely small and smaller than the second set value in each time length, no topological relation exists between the sending end and the tested end, wherein the second set value is 10% of the module value of the topological characteristic current signal sent by the signal sending end. For example, the topology characteristic current signal sent by the sending end is a topology characteristic current signal of 10 power grid frequency periods, in the 10 power grid frequency periods, the tested end having the topology relationship with the sending end has larger modulus values (larger than a first set value) at two frequencies of 783.3Hz and 883.3Hz, and the modulus values calculated by the tested end having no topology relationship at the two frequency points are extremely small (smaller than a second set value). It should be noted that the first setting value and the second setting value may be set according to the specific situation.
Further, whether the topological relation exists between the sending end and the tested end can be judged by setting a threshold (namely a set value) of a modulus value.
As another implementation mode, whether the tested end and the signal sending end have a topological relation is judged based on a long-term obtained high-low change rule of the topological characteristic current signal module value output by the tested end. Specifically, the signal transmitting end transmits a plurality of topological characteristic current signals with the same time length in time sequence, the tested end acquires a plurality of topological characteristic current signals with the corresponding time length in time sequence, and if the sequence change rule of the transmitted topological characteristic current signals is the same as the module value sequence change rule of the received topological characteristic current signals, the topological relation exists between the transmitting end and the tested end, otherwise, the topological relation does not exist. For example, the signal transmitting end discontinuously transmits a plurality of topological characteristic current signals with the same time length in time sequence, records that the transmitted topological characteristic current signal is 1, records that the non-transmitted topological characteristic current signal is 0, and then transmits a sequence change rule of the topological characteristic current signal as 1,0, 1.
As another implementation manner, the circuit further includes a communication module, and the communication module is electrically connected with the CPU module, and sends the module value of the collected topology characteristic current signal to the remote host, so that relevant personnel can observe the topology characteristic current signal conveniently.
The identification circuit of the embodiment realizes the identification of the topological characteristic current signal with low cost, high reliability and accuracy and strong practicability.
Example two
The embodiment discloses a power distribution low-voltage area topology signal identification method, which is realized on the basis of the power distribution low-voltage area topology signal identification circuit provided by the embodiment I and comprises the following steps:
collecting three-phase current sums of a tested end, and obtaining a topological characteristic current signal detected by the tested end through analog-to-digital conversion;
processing the topological characteristic current signal of each sampling period to obtain a module value of the topological characteristic current signal of each sampling period;
and judging whether a topological relation exists between the tested end and the topological signal transmitting end based on the high-low and high-low change rules of the topological characteristic current signal module value of each sampling period, and completing the identification of the topological signal.
Wherein, the processing the topological characteristic current signal of each sampling period comprises:
updating the sampling sequence of the topological characteristic current signal of the current sampling period through the linear difference value;
the updated topological characteristic current signal sampling sequences are respectively filtered through two narrow-band bandpass filters with different passband, and two sampling sequences are respectively obtained;
respectively passing the two acquired sampling sequences through a hanning window to obtain a final sampling sequence;
and performing Fourier transformation on the two obtained final sampling sequences respectively, and calculating to obtain the modulus of the topological characteristic current signal.
The steps involved in the second embodiment correspond to those of the first embodiment, and reference is made to the relevant description of the first embodiment for the implementation manner. It will be appreciated by those skilled in the art that the modules or steps of the invention described above may be implemented by general-purpose computer means, alternatively they may be implemented by program code executable by computing means, whereby they may be stored in storage means for execution by computing means, or they may be made into individual integrated circuit modules separately, or a plurality of modules or steps in them may be made into a single integrated circuit module. The present invention is not limited to any specific combination of hardware and software.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
While the foregoing description of the embodiments of the present invention has been presented in conjunction with the drawings, it should be understood that it is not intended to limit the scope of the invention, but rather, it is intended to cover all modifications or variations within the scope of the invention as defined by the claims of the present invention.
While the foregoing description of the embodiments of the present invention has been presented in conjunction with the drawings, it should be understood that it is not intended to limit the scope of the invention, but rather, it is intended to cover all modifications or variations within the scope of the invention as defined by the claims of the present invention.
Claims (7)
1. A topology signal identification circuit for a distribution low-voltage transformer area, comprising: three open-close type current transformers respectively matched with three-phase current of a tested end, a small current transformer respectively connected with the three open-close type current transformers, an AD module and a CPU module;
three-phase currents at the tested end are respectively connected to the primary sides of three open-close type current transformers, the secondary sides of the open-close type current transformers are connected to the primary sides of corresponding small current transformers, the secondary sides of the three small current transformers are connected into a current sum mode through parallel connection, and then are connected to an AD module which is electrically connected with the CPU module through an SPI bus;
the CPU module reads 24-bit sampling data of a single channel in the AD module and is used for processing the sampling value of the read topological characteristic current signal;
the processing of the sampled value of the read topological characteristic current signal comprises the following steps:
updating the sampling sequence of the topological characteristic current signal of the current sampling period through the linear difference value;
the updated topological characteristic current signal sampling sequences are respectively filtered through two narrow-band bandpass filters with different passband, and two sampling sequences are respectively obtained;
respectively passing the two acquired sampling sequences through a hanning window to obtain a final sampling sequence;
and performing Fourier transformation on the two obtained final sampling sequences respectively, and calculating to obtain the modulus of the topological characteristic current signal.
2. The topological signal identification circuit for the distribution low-voltage transformer area is characterized in that the open-close type current transformer adopts an open iron core structural design, cables of a certain phase at a tested end are sleeved in a centralized manner through an inner hole, rated current of a primary side of the open-close type current transformer is selected according to actual load, and rated current of a secondary side of the open-close type current transformer is 5A.
3. The distribution low-voltage transformer area topology signal identification circuit of claim 1, wherein said AD module comprises a single channel 24-bit AD chip for converting the collected analog topology characteristic current signal into a digital topology characteristic current signal.
4. The topology signal identification circuit of claim 1, wherein the two narrowband bandpass FILTERs are a first digital FILTER1 and a second digital FILTER2, respectively, and the passband of the first digital FILTER1 is,/>The passband of the second digital FILTER2 is +.>,/>, wherein ,/>For the transmission frequency of the topology signal, < > for>For AD sampling frequency, +.>Is the rated frequency of the power grid.
5. A power distribution low voltage district topology signal identification circuit as recited in claim 1, wherein a sampling sequence of a current sampling period is obtainedSampling sequence for the current sampling period by means of a linear difference +.>Updating to obtain updated sampling sequence +.>Sampling sequence->After passing the first digital FILTER1 and the second digital FILTER2, respectively, a sampling sequence is obtained +.> and />Two sampling sequences to be acquired +.>Andmultiplying the sample with the corresponding value of the hanning window to obtain the final sampling sequence +.>、/>The multiplication is as follows:
=/>；
=/>；
wherein ,nfor the sequence number within the data window,n=0,1,2,…,N-1，Nis the data window length.
6. The power distribution low voltage district topology signal identification circuit of claim 1, further comprising:
and judging whether a topological relation exists between the tested end and the topological signal transmitting end based on the high-low and high-low change rules of the topological characteristic current signal module value of each sampling period, and completing the identification of the topological signal.
7. A topology signal identification method for a distribution low-voltage area is characterized by comprising the following steps:
collecting three-phase current sums of a tested end, and obtaining a topological characteristic current signal detected by the tested end through analog-to-digital conversion;
processing the topological characteristic current signal of each sampling period to obtain a module value of the topological characteristic current signal of each sampling period;
judging whether a topological relation exists between a tested end and a topological signal transmitting end or not based on the high-low and high-low change rules of the topological characteristic current signal module value of each sampling period, and completing the identification of the topological signal;
the processing of the topological characteristic current signal of each sampling period comprises the following steps:
updating the sampling sequence of the topological characteristic current signal of the current sampling period through the linear difference value;
the updated topological characteristic current signal sampling sequences are respectively filtered through two narrow-band bandpass filters with different passband, and two sampling sequences are respectively obtained;
respectively passing the two acquired sampling sequences through a hanning window to obtain a final sampling sequence;
and performing Fourier transformation on the two obtained final sampling sequences respectively, and calculating to obtain the modulus of the topological characteristic current signal.
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