CN115660457A - Distributed power grid electric energy quality evaluation method and device, terminal and storage medium - Google Patents
Distributed power grid electric energy quality evaluation method and device, terminal and storage medium Download PDFInfo
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Abstract
The invention relates to the technical field of power quality evaluation, in particular to a method, a device, a terminal and a storage medium for evaluating the power quality of a distributed power grid, wherein the method comprises the steps of firstly obtaining a bus waveform; then, the bus waveform is transformed to obtain fundamental waves and a plurality of harmonic waves; then determining the electric energy quality score of the bus according to the fundamental wave and the harmonic waves; then when the power quality score is lower than a threshold value, extracting harmonic waves influencing the power quality score as target harmonic waves; and finally, determining a target distributed power supply according to the target harmonic and the waveform of the feeder line. According to the method, the waveform is obtained through the bus, characteristics which influence the power quality and are generated by a distributed power supply end or a load end can be obtained, fundamental waves and harmonic waves are obtained through waveform transformation, the power quality of the bus is determined based on harmonic wave analysis, and various power quality characteristics can be extracted through harmonic wave analysis, so that the power quality scoring is more comprehensive.
Description
Technical Field
The invention relates to the technical field of power quality evaluation, in particular to a method, a device, a terminal and a storage medium for evaluating the power quality of a distributed power grid.
Background
The distributed power grid is mainly characterized by being provided with a plurality of distributed power sources. The distributed power supply is a novel power supply system completely different from the traditional power supply mode, and is a small modular environment-compatible independent power supply which is distributed nearby users in a decentralized mode and has the power generation power of thousands of watts to fifty megawatts in order to meet the needs of specific users or support the economic operation of the existing power distribution network; it is typically located near the user and includes bio-energy generation, gas turbines, solar and photovoltaic cells, fuel cells, wind energy generation, micro-computer gas turbines, internal combustion engines, and storage control technologies. The distributed energy sources can be connected with a power grid and can also work independently.
Compared with the traditional power grid, the distributed power grid can not only locally consume distributed energy to realize multi-energy complementation, but also exchange energy with a large power grid to participate in power grid auxiliary service and emergency control, so that the distributed power grid becomes one of important development trends under a novel energy system of three types and two networks. In recent years, the internal controllable units of the distributed power grid have the advantages of multi-energy complementation and energy management flexibility, so that the distributed power grid is rapidly popularized and copied at the tail end of a power system, and a new idea is provided for solving the problems of voltage stability, power balance, electric energy quality and the like of the traditional distribution network.
The distributed power grid mostly uses natural energy such as solar energy and wind energy, and the wind energy resources and the solar energy resources have obvious fluctuation and instability, so that the output power of each subsystem fluctuates, and the power generation quality of the distributed power grid is influenced. How to quickly find the problem points existing in the power quality of the distributed power grid and further find out the root causes of the problem points is a precondition for managing the power quality of the power grid and is also a technical difficulty.
Based on this, a method, a device, a terminal and a storage medium for evaluating the power quality of a distributed power grid need to be developed and designed.
Disclosure of Invention
The embodiment of the invention provides a method, a device, a terminal and a storage medium for evaluating the power quality of a distributed power grid, which are used for solving the problem that the service life of a battery is influenced by quick charging when battery parameters are undefined in the prior art.
In a first aspect, an embodiment of the present invention provides a method for evaluating power quality of a distributed power grid, including:
acquiring a bus waveform, wherein the bus waveform contains characteristics reflecting the power quality of a bus, and a distributed power supply is connected with the bus through a feeder;
transforming the bus waveform to obtain a fundamental wave and a plurality of harmonics, wherein the transforming decomposes the bus waveform by means of waveform decomposition;
determining a power quality score of the bus according to the fundamental wave and the plurality of harmonics;
when the power quality score is lower than a threshold value, extracting harmonic waves influencing the power quality score as target harmonic waves;
and determining a target distributed power supply according to the target harmonic and the waveform of the feeder line, wherein the target distributed power supply is a distributed power supply which influences the electric energy quality of the bus.
In one possible implementation, the transforming the bus waveform to obtain a fundamental wave and a plurality of harmonics includes:
sampling the bus waveform to obtain a bus waveform data set, wherein the bus waveform data set comprises a plurality of bus waveform sampling points;
constructing a plurality of wavelet base data sets, wherein the wavelet base data sets are obtained based on wavelet base function sampling, the wavelet base data sets comprise a plurality of wavelet base sampling points, and the wavelet base sampling points correspond to bus waveform sampling points;
obtaining a plurality of amplitude coefficients from the plurality of wavelet base data sets and the bus waveform data set, wherein an amplitude coefficient characterizes an amplitude of a fundamental wave or an amplitude of a harmonic;
and obtaining a fundamental wave and a plurality of harmonic waves according to the wavelet basis function and the plurality of amplitude coefficients.
In one possible implementation, the obtaining of the wavelet base data sets based on Harr wavelet basis function sampling, the obtaining of the plurality of amplitude coefficients from the plurality of wavelet base data sets and the generatrix waveform data set, comprises:
determining a plurality of amplitude coefficients from the plurality of wavelet base data sets, the bus waveform data set, and a first formula, wherein the first formula is:
in the formula, W k Is the amplitude coefficient of the kth harmonic, N is the total number of elements in the wavelet data set or the bus waveform data set, x n For the nth bus bar waveform sampling point,
to correspond to the k-th harmonicIs sampled at the nth wavelet basis, t n The sampling time interval of the nth sampling point in the wavelet data set or the bus waveform data set.
In one possible implementation, the transforming the bus waveform to obtain a fundamental wave and a plurality of harmonics includes:
sampling the bus waveform to obtain a bus waveform data set, wherein the bus waveform data set comprises a plurality of bus waveform sampling points;
obtaining a plurality of amplitude coefficients from a second formula and the bus waveform data set, wherein an amplitude coefficient characterizes an amplitude of a fundamental wave or an amplitude of a harmonic, the second formula being:
in the formula, W k Is the amplitude coefficient of the kth harmonic, N is the total number of elements in the wavelet data set or the bus waveform data set, x n Is the nth bus waveform sampling point, e is a natural constant, j is an imaginary unit, and the sampling time interval of the nth sampling point in the wavelet data set or the bus waveform data set is omega 0 Is the fundamental frequency;
and obtaining a fundamental wave and a plurality of harmonics according to the plurality of amplitude coefficients.
In one possible implementation, the waveform of the bus bar includes: a voltage waveform and a current waveform, the fundamental wave including: a voltage fundamental and a current fundamental, the plurality of harmonics including a plurality of current harmonics and a plurality of voltage harmonics, the determining a power quality score for the bus from the fundamental and the plurality of harmonics comprising:
obtaining a plurality of scoring factors, wherein the scoring factors comprise: the power factor is obtained based on a cosine value of a phase of a current fundamental wave and a phase difference of a voltage fundamental wave, the harmonic factor factors are obtained based on a ratio of amplitudes of harmonic waves to an amplitude of the fundamental wave, and the voltage fluctuation factor is obtained based on a ratio of a standard voltage value to an amplitude of the voltage fundamental wave;
and inputting the plurality of grading factors into a grading model to obtain the electric energy quality grade, wherein the grading model is provided with a plurality of input nodes, a plurality of conversion nodes and output nodes, each change node receives the output of the plurality of input nodes, and the output nodes receive the output of the plurality of conversion nodes.
In one possible implementation manner, the expression of the transfer function of the plurality of transformation nodes of the scoring model is:
in the formula, alpha and beta are respectively upper and lower limit coefficients, sigma is a threshold value, f (b) the output value of the transformation node, and b is the input value of the transformation node;
the scoring model adjusts an upper limit coefficient and a lower limit coefficient according to a plurality of historical samples and a plurality of historical quality scores, so that the scores output by the scoring model are consistent with the historical quality scores, wherein the historical samples correspond to the historical quality scores and comprise a plurality of historical scoring factors.
In one possible implementation manner, the determining a target distributed power source according to the target harmonic and the waveform of the feeder line includes:
obtaining a plurality of correlation coefficients according to the target harmonic and the waveforms of the plurality of feeder lines, wherein the correlation coefficients represent the correlation between the target harmonic and the waveforms of the feeder lines;
selecting a feeder line corresponding to the maximum correlation coefficient as a target distributed power supply;
wherein, the correlation coefficient is obtained by executing the following steps through each feeder line connected with the bus:
determining a correlation coefficient according to the target harmonic, the waveform of the feeder line and a third formula, wherein the third formula is as follows:
in the formula, epsilon m Is the correlation coefficient, w, of the m-th feeder line d (t) is the target harmonic, w m And (t) is the waveform of the feeder line.
In a second aspect, an embodiment of the present invention provides a distributed power grid power quality evaluation apparatus, including:
the bus waveform acquisition module is used for acquiring a bus waveform, wherein the bus waveform comprises characteristics reflecting the electric energy quality of a bus;
the waveform transformation module is used for transforming the bus waveform to obtain a fundamental wave and a plurality of harmonic waves, wherein the bus waveform is decomposed by the transformation in a waveform decomposition mode;
the grading module is used for determining the electric energy quality grade of the bus according to the fundamental wave and the harmonic waves;
the target harmonic extraction module is used for extracting the harmonic which affects the electric energy quality score as a target harmonic when the electric energy quality score is lower than a threshold value;
and the number of the first and second groups,
and the target distributed power supply determining module is used for determining a target distributed power supply according to the target harmonic and the waveform of a feeder line, wherein the feeder line is connected with the bus, and the target distributed power supply is the feeder line which influences the electric energy quality of the bus.
In a third aspect, an embodiment of the present invention provides a terminal, including a memory and a processor, where the memory stores a computer program operable on the processor, and the processor executes the computer program to implement the steps of the method according to the first aspect or any possible implementation manner of the first aspect.
In a fourth aspect, the present invention provides a computer-readable storage medium, which stores a computer program that, when executed by a processor, implements the steps of the method as described in the first aspect or any one of the possible implementations of the first aspect.
Compared with the prior art, the implementation mode of the invention has the following beneficial effects:
the embodiment of the method for evaluating the power quality of the distributed power grid comprises the following steps of firstly, obtaining a bus waveform, wherein the bus waveform comprises characteristics reflecting the power quality of a bus, and a distributed power supply is connected with the bus through a feeder line; then, transforming the bus waveform to obtain a fundamental wave and a plurality of harmonic waves, wherein the transforming decomposes the bus waveform in a waveform decomposition mode; then, determining the electric energy quality score of the bus according to the fundamental wave and the plurality of harmonics; then, when the power quality score is lower than a threshold value, extracting harmonic waves influencing the power quality score as target harmonic waves; and finally, determining a target distributed power supply according to the target harmonic wave and the waveform of the feeder line, wherein the target distributed power supply is a distributed power supply which influences the electric energy quality of the bus. The method of the invention obtains the waveform through the bus, so that the characteristics which influence the electric energy quality and are generated by a distributed power supply end or a load end can be obtained, fundamental waves and harmonic waves are obtained through waveform transformation, the electric energy quality of the bus is determined based on harmonic wave analysis, and various electric energy quality characteristics can be extracted through harmonic wave analysis, so that the electric energy quality score is more comprehensive, when the electric energy quality score is lower, the harmonic waves which influence the score are extracted, and a target distributed power supply which influences the electric energy quality is determined through the mode of comparing the harmonic waves with the waveform of a feeder line, thereby realizing the positioning of a problem source and providing a precondition for improving the electric energy quality.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without inventive labor.
Fig. 1 is a flowchart of a method for evaluating the power quality of a distributed power grid according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a distributed power grid structure provided by an embodiment of the present invention;
FIG. 3 is a functional block diagram of an evaluation model provided by an embodiment of the invention;
fig. 4 is a functional block diagram of a distributed power grid power quality evaluation device according to an embodiment of the present invention;
fig. 5 is a functional block diagram of a server provided in an embodiment of the present invention.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular system structures, techniques, etc. in order to provide a thorough understanding of the embodiments of the invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the following description is made with reference to the accompanying drawings.
The following is a detailed description of the embodiments of the present invention, which is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.
Fig. 1 is a flowchart of a distributed power grid power quality evaluation method according to an embodiment of the present invention.
As shown in fig. 1, it shows an implementation flowchart of the method for evaluating the power quality of the distributed power grid according to the embodiment of the present invention, and details are as follows:
in step 101, a bus waveform is obtained, wherein the bus waveform includes a characteristic reflecting the power quality of a bus, and a distributed power supply is connected with the bus through a feeder.
Illustratively, as shown in fig. 2, a distributed power grid is shown, in which a bus 201 supplies power mainly by means of a distributed power source 204 and a power transformer 203 to deliver power to a load 205, wherein the load 205 and the distributed power source 204 are connected to the bus 201 by a feeder 202.
In the embodiment of the present invention, the acquired waveform is the waveform of the bus 201, wherein in some application scenarios the waveform is a voltage waveform for analyzing voltage fluctuation and distortion, and in other application scenarios the waveform is a current waveform for analyzing current distortion, load factor and current harmonic, and furthermore, it is also possible that both waveforms are included for analyzing power factor, and those skilled in the art should understand that the example provided here is not limited for ease of understanding.
Step 102 comprises:
and transforming the bus waveform to obtain a fundamental wave and a plurality of harmonics, wherein the transformation decomposes the bus waveform by means of waveform decomposition.
In some embodiments, the transforming the bus waveform to obtain a fundamental wave and a plurality of harmonics includes:
sampling the bus waveform to obtain a bus waveform data set, wherein the bus waveform data set comprises a plurality of bus waveform sampling points;
constructing a plurality of wavelet base data sets, wherein the wavelet base data sets are obtained based on wavelet base function sampling, the wavelet base data sets comprise a plurality of wavelet base sampling points, and the wavelet base sampling points correspond to bus waveform sampling points;
obtaining a plurality of amplitude coefficients from the plurality of wavelet base data sets and the bus waveform data set, wherein the amplitude coefficients characterize the amplitude of the fundamental wave or the amplitude of the harmonic wave;
and obtaining a fundamental wave and a plurality of harmonic waves according to the wavelet basis function and the plurality of amplitude coefficients.
In some embodiments, the wavelet base data set is obtained based on Harr wavelet basis function sampling, the obtaining a plurality of magnitude coefficients from the plurality of wavelet base data sets and the bus waveform data set comprising:
determining a plurality of amplitude coefficients from the plurality of wavelet base data sets, the bus waveform data set, and a first formula, wherein the first formula is:
in the formula, W k Is the amplitude coefficient of the kth harmonic, N is the total number of elements in the wavelet data set or the bus waveform data set, x n For the nth bus bar waveform sampling point,
for the nth wavelet base sampling point, t, in the wavelet base data set corresponding to the kth harmonic n The sampling time interval of the nth sampling point in the wavelet data set or the bus waveform data set.
In some embodiments, the transforming the bus waveform to obtain a fundamental wave and a plurality of harmonics includes:
sampling the bus waveform to obtain a bus waveform data set, wherein the bus waveform data set comprises a plurality of bus waveform sampling points;
obtaining a plurality of amplitude coefficients from a second formula and the bus waveform data set, wherein an amplitude coefficient characterizes an amplitude of a fundamental wave or an amplitude of a harmonic, the second formula being:
in the formula, W k Is the amplitude coefficient of the kth harmonic, N is the total number of elements in the wavelet data set or the bus waveform data set, x n Is the nth bus waveform sampling point, e is a natural constant, j is an imaginary unit, and the sampling time interval of the nth sampling point in the wavelet data set or the bus waveform data set is omega 0 Is the fundamental frequency;
and obtaining a fundamental wave and a plurality of harmonics according to the plurality of amplitude coefficients.
Illustratively, there are various ways of transforming, e.g., fourier transform, windowed fourier transform, or wavelet transform, etc.
For the case of applying fourier transform, after a plurality of sampling data of the bus waveform are acquired, discrete fourier transform is applied to acquire amplitude coefficients corresponding to different harmonics, and the specific formula is as follows:
in the formula, W k Is the amplitude coefficient of the kth harmonic, N is the total number of elements in the wavelet data set or the bus waveform data set, x n Is the nth bus waveform sampling point, e is a natural constant, j is an imaginary unit, and the sampling time interval of the nth sampling point in the wavelet data set or the bus waveform data set is omega 0 Is the fundamental frequency.
After the amplitude coefficient is obtained, a waveform function corresponding to different harmonic times can be established.
In addition, the wavelet basis function may be used to determine the amplitude coefficient for each waveform by:
in the formula, W k Is the amplitude coefficient of the kth harmonic, N is the total number of elements in the wavelet data set or the bus waveform data set, x n For the nth bus bar waveform sampling point,
for the nth wavelet base sampling point, t, in the wavelet base data set corresponding to the kth harmonic n The sampling time interval of the nth sampling point in the wavelet data set or the bus waveform data set.
After the amplitude coefficient is obtained, the waveform function of each harmonic frequency can be determined through the amplitude coefficient and the wavelet basis function.
In step 103, a power quality score of the bus is determined according to the fundamental wave and the plurality of harmonics.
In some embodiments, the waveform of the bus bar comprises: a voltage waveform and a current waveform, the fundamental wave including: a voltage fundamental and a current fundamental, the plurality of harmonics including a plurality of current harmonics and a plurality of voltage harmonics, step 103 comprising:
obtaining a plurality of scoring factors, wherein the scoring factors comprise: the power factor is obtained based on a cosine value of a phase of a current fundamental wave and a phase difference of a voltage fundamental wave, the harmonic factor factors are obtained based on a ratio of amplitudes of harmonic waves to an amplitude of the fundamental wave, and the voltage fluctuation factor is obtained based on a ratio of a standard voltage value to an amplitude of the voltage fundamental wave;
and inputting the plurality of grading factors into a grading model to obtain the power quality grade, wherein the grading model is provided with a plurality of input nodes, a plurality of transformation nodes and output nodes, each transformation node receives the output of the plurality of input nodes, and the output nodes receive the output of the plurality of transformation nodes.
In some embodiments, the expression of the plurality of transform node transfer functions of the scoring model is:
in the formula, alpha and beta are respectively upper and lower limit coefficients, sigma is a threshold value, f (b) is the output value of a transformation node, and b is the input value of the transformation node;
the scoring model adjusts an upper limit coefficient and a lower limit coefficient according to a plurality of historical samples and a plurality of historical quality scores, so that the scores output by the scoring model are consistent with the historical quality scores, wherein the historical samples correspond to the historical quality scores and comprise a plurality of historical scoring factors.
Illustratively, as shown in FIG. 3, a scoring model is shown with input sectionsA point 301, a transformation node 302 and an output node 303, wherein the input node 301 receives an input scoring factor and multiplies the scoring factor by a corresponding weight coefficient, such as W in the figure 1 The weights, which are the first input scoring factors, multiplied by the first input scoring factors are input into the respective transformation nodes 302. The transfer function expression of the transformation node is as follows:
where α and β are upper and lower limit coefficients, σ is a threshold, f (b) is an output value of the transform node, and b is an input value of the transform node.
The output values of the plurality of transform nodes 302 are further processed by an output node 303 to obtain an output value.
The purpose of this structure is to construct a curve that can be fitted to a multidimensional construct by simply adjusting the weighting coefficients and the upper and lower limit coefficients as described above.
After the model is constructed, the adjustment to the coefficients is obtained based on historical quality scores of the historical samples and the corresponding samples. For example, some samples (for example, samples with dominant voltage fluctuation) affecting production and living are scored, while some samples bring some adverse effects but do not significantly reduce power consumption quality (for example, slight harmonic pollution), and the corresponding relationship between the samples and the scores can be adjusted to obtain a fit, that is, the model can output the correct scores of the samples after adjusting the coefficients of the model according to the corresponding relationship between the samples and the scores.
For the adjustment mode, a manual experience adjustment method can be adopted, and a genetic algorithm can be adopted to guide the output of the model to be consistent with the historical quality score.
It should be noted that after the harmonic is obtained, the power factor may be obtained through a cosine value of a phase difference between the current fundamental wave and the voltage fundamental wave, so as to serve as the power factor. The ratio of the amplitude of the harmonic wave to the amplitude of the fundamental wave can be used as a harmonic wave factor, and the ratio of the absolute value of the voltage difference obtained by subtracting the standard voltage value from the voltage amplitude to the standard voltage is used as a voltage fluctuation factor. These factors are input as inputs into the input nodes of the scoring model described above.
In step 104, when the power quality score is lower than a threshold, extracting a harmonic affecting the power quality score as a target harmonic.
In step 105, determining a target distributed power source according to the target harmonic and the waveform of the feeder line, wherein the target distributed power source is a distributed power source which affects the power quality of the bus.
In some embodiments, step 105 comprises:
obtaining a plurality of correlation coefficients according to the target harmonic and the waveforms of the plurality of feeder lines, wherein the correlation coefficients represent the correlation between the target harmonic and the waveforms of the feeder lines;
selecting a feeder line corresponding to the maximum correlation coefficient as a target distributed power supply;
the correlation coefficient is obtained by executing the following steps through each feeder line connected with the bus:
determining a correlation coefficient according to the target harmonic, the waveform of the feeder line and a third formula, wherein the third formula is as follows:
in the formula, σ m Is the correlation coefficient, w, of the m-th feeder line d (t) is the target harmonic, w m And (t) is the waveform of the feeder line.
For example, when the power quality score is low, harmonics which mainly affect the power quality score can be found, and as described above, the lower-valued factors in the scoring factors, and their corresponding harmonics, can be checked and used as the main harmonics which affect the score.
And respectively carrying out similarity comparison on the found harmonic waves and the waveforms of all the feeder lines to obtain a correlation coefficient, wherein the higher the coefficient is, the higher the possibility of generating the harmonic waves is.
A correlation coefficient calculation method is characterized by comprising the following formulas:
in the formula, epsilon m Is the correlation coefficient, w, of the m-th feeder line d (t) is the target harmonic, w m And (t) is the waveform of the feeder line.
The embodiment of the method for evaluating the power quality of the distributed power grid comprises the following steps of firstly, obtaining a bus waveform, wherein the bus waveform comprises characteristics reflecting the power quality of a bus, and a distributed power supply is connected with the bus through a feeder line; then, transforming the bus waveform to obtain a fundamental wave and a plurality of harmonics, wherein the transforming decomposes the bus waveform in a waveform decomposition manner; then, determining the electric energy quality score of the bus according to the fundamental wave and the plurality of harmonics; then, when the power quality score is lower than a threshold value, extracting harmonic waves influencing the power quality score as target harmonic waves; and finally, determining a target distributed power supply according to the target harmonic and the waveform of the feeder line, wherein the target distributed power supply is a distributed power supply which influences the power quality of the bus. The method of the invention obtains the waveform through the bus, so that the characteristics which influence the electric energy quality and are generated by a distributed power supply end or a load end can be obtained, fundamental waves and harmonic waves are obtained through waveform transformation, the electric energy quality of the bus is determined based on harmonic wave analysis, and various electric energy quality characteristics can be extracted through harmonic wave analysis, so that the electric energy quality score is more comprehensive, when the electric energy quality score is lower, the harmonic waves which influence the score are extracted, and a target distributed power supply which influences the electric energy quality is determined through the mode of comparing the harmonic waves with the waveform of a feeder line, thereby realizing the positioning of a problem source and providing a precondition for improving the electric energy quality.
It should be understood that the sequence numbers of the steps in the above embodiments do not mean the execution sequence, and the execution sequence of each process should be determined by the function and the inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.
The following are apparatus embodiments of the invention, and for details not described in detail therein, reference may be made to the corresponding method embodiments described above.
Fig. 4 is a functional block diagram of a distributed power grid power quality evaluation device according to an embodiment of the present invention, and referring to fig. 4, the distributed power grid power quality evaluation device 4 includes: the device comprises a waveform acquisition module 401, a waveform transformation module 402, a scoring module 403, a target harmonic extraction module 404 and a target distributed power source determination module 404.
The bus waveform obtaining module 401 is configured to obtain a bus waveform, where the bus waveform includes a characteristic that reflects power quality of a bus;
a waveform transformation module 402, configured to transform the bus waveform to obtain a fundamental wave and a plurality of harmonics, where the transformation decomposes the bus waveform by waveform decomposition;
a scoring module 403, configured to determine a power quality score of the bus according to the fundamental wave and the plurality of harmonics;
a target harmonic extraction module 404, configured to extract a harmonic that affects the power quality score as a target harmonic when the power quality score is lower than a threshold;
and a target distributed power source determining module 404, configured to determine a target distributed power source according to the target harmonic and a waveform of a feeder line, where the feeder line is connected to the bus, and the target distributed power source is a feeder line that affects the power quality of the bus.
Fig. 5 is a functional block diagram of a terminal according to an embodiment of the present invention. As shown in fig. 5, the terminal 5 of this embodiment includes: a processor 500 and a memory 501, the memory 501 having stored therein a computer program 502 executable on the processor 500. The processor 500 executes the computer program 502 to implement the above-mentioned steps of the method and embodiment for evaluating the power quality of the distributed power grid, such as the steps 101 to 105 shown in fig. 1.
Illustratively, the computer program 502 may be partitioned into one or more modules/units that are stored in the memory 501 and executed by the processor 500 to implement the present invention.
The terminal 5 may be a desktop computer, a notebook, a palm computer, a cloud server, or other computing devices. The terminal 5 may include, but is not limited to, a processor 500, a memory 501. It will be appreciated by those skilled in the art that fig. 5 is merely an example of a terminal 5 and does not constitute a limitation of the terminal 5, and may include more or fewer components than shown, or some components may be combined, or different components, e.g., the terminal may also include input output devices, network access devices, buses, etc.
The Processor 500 may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic device, discrete hardware component, or the like. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
The memory 501 may be an internal storage unit of the terminal 5, such as a hard disk or a memory of the terminal 5. The memory 501 may also be an external storage device of the terminal 5, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card) and the like provided on the terminal 5. Further, the memory 501 may also include both an internal storage unit and an external storage device of the terminal 5. The memory 501 is used for storing the computer program and other programs and data required by the terminal. The memory 501 may also be used to temporarily store data that has been output or is to be output.
It will be apparent to those skilled in the art that, for convenience and brevity of description, only the above-mentioned division of the functional units and modules is illustrated, and in practical applications, the above-mentioned function distribution may be performed by different functional units and modules according to needs, that is, the internal structure of the apparatus is divided into different functional units or modules to perform all or part of the above-mentioned functions. Each functional unit and module in the embodiments may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit, and the integrated unit may be implemented in a form of hardware, or may be implemented in a form of software functional unit. In addition, specific names of the functional units and modules are only for convenience of distinguishing from each other, and are not used for limiting the protection scope of the present application. The specific working processes of the units and modules in the system may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
In the above embodiments, the description of each embodiment is focused on, and for parts that are not described or illustrated in detail in a certain embodiment, reference may be made to the description of other embodiments.
Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
In the embodiments provided in the present invention, it should be understood that the disclosed apparatus/terminal and method may be implemented in other manners. For example, the above-described apparatus/terminal embodiments are merely illustrative, and for example, the division of the modules or units is only one type of logical function division, and other division manners may exist in actual implementation, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated modules/units, if implemented in the form of software functional units and sold or used as separate products, may be stored in a computer readable storage medium. Based on such understanding, all or part of the flow in the method according to the above embodiments may be implemented by a computer program, which may be stored in a computer readable storage medium and used by a processor to implement the steps of the method and apparatus embodiments. Wherein the computer program comprises computer program code, which may be in the form of source code, object code, an executable file or some intermediate form, etc. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, usb disk, removable hard disk, magnetic disk, optical disk, computer Memory, read-Only Memory (ROM), random Access Memory (RAM), electrical carrier wave signals, telecommunications signals, software distribution medium, and the like.
The above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may be modified or some technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the embodiments of the present invention, and they should be construed as being included therein.
Claims (10)
1. A distributed power grid power quality evaluation method is characterized by comprising the following steps:
acquiring a bus waveform, wherein the bus waveform contains characteristics reflecting the power quality of a bus, and a distributed power supply is connected with the bus through a feeder;
transforming the bus waveform to obtain a fundamental wave and a plurality of harmonics, wherein the transforming decomposes the bus waveform by means of waveform decomposition;
determining a power quality score of the bus according to the fundamental wave and the plurality of harmonics;
when the power quality score is lower than a threshold value, extracting harmonic waves influencing the power quality score as target harmonic waves;
and determining a target distributed power supply according to the target harmonic and the waveform of the feeder line, wherein the target distributed power supply is a distributed power supply which influences the electric energy quality of the bus.
2. The distributed power grid power quality evaluation method according to claim 1, wherein the transforming the bus waveform to obtain a fundamental wave and a plurality of harmonics comprises:
sampling the bus waveform to obtain a bus waveform data set, wherein the bus waveform data set comprises a plurality of bus waveform sampling points;
constructing a plurality of wavelet base data sets, wherein the wavelet base data sets are obtained based on wavelet base function sampling, the wavelet base data sets comprise a plurality of wavelet base sampling points, and the wavelet base sampling points correspond to bus waveform sampling points;
obtaining a plurality of amplitude coefficients from the plurality of wavelet base data sets and the bus waveform data set, wherein an amplitude coefficient characterizes an amplitude of a fundamental wave or an amplitude of a harmonic;
and obtaining a fundamental wave and a plurality of harmonic waves according to the wavelet basis function and the plurality of amplitude coefficients.
3. The distributed power grid power quality evaluation method according to claim 2, wherein the wavelet base data set is obtained based on Harr wavelet basis function sampling, and the obtaining of the plurality of amplitude coefficients according to the plurality of wavelet base data sets and the bus waveform data set comprises:
determining a plurality of amplitude coefficients from the plurality of wavelet base data sets, the bus waveform data set, and a first formula, wherein the first formula is:
in the formula, W k Is the amplitude coefficient of the kth harmonic, N is the total number of elements in the wavelet data set or the bus waveform data set, x n For the nth bus bar waveform sampling point,
for the nth wavelet base sampling point, t, in the wavelet base data set corresponding to the kth harmonic n The sampling time interval of the nth sampling point in the wavelet data set or the bus waveform data set.
4. The distributed power grid power quality evaluation method according to claim 1, wherein the transforming the bus waveform to obtain a fundamental wave and a plurality of harmonics comprises:
sampling the bus waveform to obtain a bus waveform data set, wherein the bus waveform data set comprises a plurality of bus waveform sampling points;
obtaining a plurality of amplitude coefficients from a second formula and the bus waveform data set, wherein an amplitude coefficient characterizes an amplitude of a fundamental wave or an amplitude of a harmonic, the second formula being:
in the formula, W k Is the amplitude coefficient of the kth harmonic, N is the total number of elements in the wavelet data set or the bus waveform data set, x n Is the nth bus waveform sampling point, e is a natural constant, j is an imaginary unit, and the sampling time interval of the nth sampling point in the wavelet data set or the bus waveform data set is omega 0 Is the fundamental frequency;
and obtaining a fundamental wave and a plurality of harmonics according to the plurality of amplitude coefficients.
5. The distributed power grid power quality evaluation method according to claim 1, wherein the waveform of the bus comprises: a voltage waveform and a current waveform, the fundamental wave including: a voltage fundamental and a current fundamental, the plurality of harmonics including a plurality of current harmonics and a plurality of voltage harmonics, the determining a power quality score for the bus from the fundamental and the plurality of harmonics comprising:
obtaining a plurality of scoring factors, wherein the scoring factors comprise: the power factor is obtained based on a cosine value of a phase of a current fundamental wave and a phase difference of a voltage fundamental wave, the harmonic factor factors are obtained based on a ratio of amplitudes of harmonic waves to an amplitude of the fundamental wave, and the voltage fluctuation factor is obtained based on a ratio of a standard voltage value to an amplitude of the voltage fundamental wave;
and inputting the plurality of grading factors into a grading model to obtain the electric energy quality grade, wherein the grading model is provided with a plurality of input nodes, a plurality of conversion nodes and output nodes, each change node receives the output of the plurality of input nodes, and the output nodes receive the output of the plurality of conversion nodes.
6. The distributed power grid power quality evaluation method according to claim 5, wherein the expression of the transfer functions of the plurality of transformation nodes of the scoring model is as follows:
in the formula, alpha and beta are respectively upper and lower limit coefficients, sigma is a threshold value, f (b) the output value of the transformation node, and b is the input value of the transformation node;
the scoring model adjusts an upper limit coefficient and a lower limit coefficient according to a plurality of historical samples and a plurality of historical quality scores, so that the scores output by the scoring model are consistent with the historical quality scores, wherein the historical samples correspond to the historical quality scores and comprise a plurality of historical scoring factors.
7. The distributed power grid power quality evaluation method according to any one of claims 1 to 6, wherein the determining a target distributed power source according to the target harmonic and the waveform of the feeder line comprises:
obtaining a plurality of correlation coefficients according to the target harmonic and the waveforms of the plurality of feeder lines, wherein the correlation coefficients represent the correlation between the target harmonic and the waveforms of the feeder lines;
selecting a feeder line corresponding to the maximum correlation coefficient as a target distributed power supply;
the correlation coefficient is obtained by executing the following steps through each feeder line connected with the bus:
determining a correlation coefficient according to the target harmonic, the waveform of the feeder line and a third formula, wherein the third formula is as follows:
in the formula, epsilon m Is the correlation coefficient, w, of the m-th feeder line d (t) is the target harmonic, w m And (t) is the waveform of the feeder line.
8. The utility model provides a distributed power grid electric energy quality evaluation device which characterized in that includes:
the bus waveform acquisition module is used for acquiring a bus waveform, wherein the bus waveform comprises characteristics reflecting the electric energy quality of a bus;
the waveform transformation module is used for transforming the bus waveform to obtain a fundamental wave and a plurality of harmonic waves, wherein the transformation decomposes the bus waveform in a waveform decomposition mode;
the grading module is used for determining the electric energy quality grade of the bus according to the fundamental wave and the harmonic waves;
the target harmonic extraction module is used for extracting the harmonic which affects the electric energy quality score as a target harmonic when the electric energy quality score is lower than a threshold value;
and the number of the first and second groups,
and the target distributed power supply determining module is used for determining a target distributed power supply according to the target harmonic and the waveform of a feeder line, wherein the feeder line is connected with the bus, and the target distributed power supply is the feeder line which influences the electric energy quality of the bus.
9. A terminal comprising a memory and a processor, the memory having stored therein a computer program operable on the processor, wherein the processor, when executing the computer program, performs the steps of the method according to any of claims 1 to 7.
10. A computer-readable storage medium, in which a computer program is stored which, when being executed by a processor, carries out the steps of the method according to any one of claims 1 to 7.
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