Electric energy metering method and equipment for broadband characteristic of power system

Abstract

The invention relates to an electric energy metering method for broadband characteristics of an electric power system. The electric energy metering method comprises the following steps: acquiring electric quantity data corresponding to current and voltage by using a filter built in a power grid system; preprocessing the electric quantity data to obtain effective electric quantity data; calculating the effective electric quantity data through a preset power formula to obtain average power of a sampling period; decomposing the electric quantity data of the electric power system to obtain a wavelet packet frequency band; carrying out adaptive harmonic extraction on the wavelet packet frequency band to obtain a sampling frequency spectrum; and obtaining an electric energy metering value of the power system according to the sampling frequency spectrum and time integration. In the technical scheme of the invention, the result shows that the amplitude and phase information of the waveform are well reserved by the extracted waveform, and electric energy metering can be carried out on each frequency component by direct integration; similarly, the method is used for processing other wavelet packet frequency bands, the same effect is remarkable, and the metering error can be controlled within 3%.

Description

Technical Field

[0001] The present invention relates to the field of electric power technology, and in particular to an electric energy metering method, system, readable storage medium, and computer equipment for broadband characteristics of an electric power system. Background Art

[0002] For new power systems with impact loads and a high proportion of renewable energy generation, their internal electrical characteristics often show nonlinear characteristics. The research on harmonic compensation and management of power systems at home and abroad is relatively in-depth, but the impact of nonlinear voltage and current waveforms in the power grid on power metering is not clear. A large amount of harmonics injected into the system not only greatly affects the quality of power, but also reduces the accuracy of power metering. Relevant domestic research has shown that traditional electromagnetic energy meters and inductive energy meters will produce certain errors when measuring nonlinear loads containing a large amount of harmonics due to deficiencies in their own principles and structural designs. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0004] To this end, the object of the present invention is to provide an electric energy metering method and device for the broadband characteristics of the power system, which can directly obtain metering data based on the extracted information and improve the accuracy and reliability of the metering.

[0005] To achieve the above-mentioned purpose, the technical solution of the first aspect of the present invention provides an electric energy metering method for the broadband characteristics of the power system, comprising the following steps:

[0006] The electric quantity data corresponding to the current and voltage are collected by using the filter built into the power grid system;

[0007] Preprocessing the power data to obtain effective power data, wherein the preprocessing includes amplification and filtering to eliminate noise and interference;

[0008] The effective power data is calculated using a preset power formula to obtain an average power of a sampling period;

[0009] Decomposing the electric quantity data of the electric power system to obtain wavelet packet frequency bands;

[0010] Performing adaptive harmonic extraction on the wavelet packet frequency band to obtain a sampling spectrum;

[0011] The electric energy measurement value of the power system is obtained by integrating the sampled spectrum over time.

[0012] In this technical solution, the electric power metering method and equipment for the electric power system proposed by the present invention has a maximum harmonic metering error of 2.03%. The results show that the extracted waveform retains the amplitude and phase information of the waveform well, and direct integration can be used to measure the electric power of each frequency component; similarly, this method is used to process the remaining wavelet packet frequency bands, and the effect is also significant, and the metering error can be controlled within 3%.

[0013] In the above technical solution, preferably, the effective power data is calculated by a preset power formula to obtain the average power of a sampling period, including the following steps:

[0014] Calculate the instantaneous power of the sampling point according to the effective power data by using a preset instantaneous power formula;

[0015] The average power of a sampling period is calculated according to the instantaneous power.

[0016] In the above technical solution, preferably, the expression of the preset instantaneous power formula is: p(n)=u(n)i(n), wherein u(n) is the voltage data in the electric quantity data at the sampling point n, i(n) is the current data in the electric quantity data at the sampling point n, and p(n) is the instantaneous power at the sampling point n;

[0017] The expression of the average power P is: Where N is the number of sampling points in one sampling period.

[0018] In the above technical solution, preferably, performing adaptive harmonic extraction on the wavelet packet frequency band to obtain a sampling spectrum comprises the following steps:

[0019] Modifying the wavelet packet frequency band according to the average power;

[0020] Selecting a harmonic frequency band of a preset frequency from the modified wavelet packet frequency band;

[0021] The sampling spectrum is obtained by performing decomposition according to the fundamental wave period data corresponding to the harmonic frequency band.

[0022] In the above technical solution, preferably, the expression of the sampling spectrum is:

[0023] u (4) (t)=4.5sin(2π1250t+25°)+4.2sin(2π1350t+245°)+3.8sin(2π1450t+145°);

[0024] i (4)(t)=1.4sin(2π1250t+135°)+2.1sin(2π1350t+15°)+1.0sin(2π1450t+220°);

[0025] Where t is the sampling time.

[0026] In the above technical solution, preferably, the electric energy metering value W Tc The expression is:

[0027]

[0028] In the above technical solution, preferably, the wavelet packet frequency band is modified according to the average power to remove the wavelet packet frequency band corresponding to the first and last two fundamental wave periods and calculate the average power.

[0029] The technical solution of the second aspect of the present invention provides an electric energy metering system for the broadband characteristics of the power system, comprising:

[0030] The power acquisition module is configured to collect power data corresponding to current and voltage using a filter built into the power grid system;

[0031] A preprocessing module is configured to preprocess the power data to obtain effective power data, wherein the preprocessing includes amplification and filtering to eliminate noise and interference;

[0032] A power calculation module is configured to calculate the effective power data using a preset power formula to obtain an average power of a sampling period;

[0033] A frequency band decomposition module is configured to decompose the electric quantity data of the electric power system to obtain a wavelet packet frequency band;

[0034] An adaptive extraction module is configured to perform adaptive harmonic extraction on the wavelet packet frequency band to obtain a sampling spectrum;

[0035] The electric energy calculation module is configured to obtain the electric energy measurement value of the power system according to the sampling spectrum according to time integration.

[0036] The technical solution of the third aspect of the present invention provides a readable storage medium on which a computer program is stored. When the program is executed by a processor, the steps of the electric energy metering method for the broadband characteristics of the power system provided by the technical solution of the first aspect are implemented.

[0037] The technical solution of the fourth aspect of the present invention provides a computer device, including a storage medium and a processor; the storage medium is used to store a computer program; the processor is used to execute the computer program to implement the steps of the electric energy metering method for the wide-band characteristics of the power system provided by the technical solution of the first aspect above.

[0038] Compared with the prior art, the advantages of the electric energy metering method and device for the broadband characteristics of the power system provided by the present invention are: the electric energy metering method and device for the power system proposed by the present invention have a maximum harmonic metering error of 2.03%. The results show that the extracted waveform retains the amplitude and phase information of the waveform well, and direct integration can measure the electric energy of each frequency component; similarly, this method is used to process the remaining wavelet packet bands, and the effect is also significant, and the metering error can be controlled within 3%; the electric energy metering method and device developed by the present invention based on broadband measurement technology are reasonable and accurate, and the metering formula is derived by discrete instantaneous sampling values, which avoids a large amount of calculation and a long delay. The wavelet packet band decomposition and adaptive harmonic extraction are used to achieve accurate metering of broadband signals, correct the distortion caused by the endpoint effect, and improve the accuracy of the metering result; it can achieve two-way metering of harmonic energy, including the judgment of energy value and flow direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0040] Figure 1 A flowchart of an electric energy metering method according to an embodiment of the present invention is shown;

[0041] Figure 2 A flowchart of step S3 according to an embodiment of the present invention is shown;

[0042] Figure 3 A flowchart of step S5 according to an embodiment of the present invention is shown;

[0043] Figure 4 The structure block diagram of the electric energy metering system involved in the embodiment of the present invention is shown;

[0044] Figure 5 shows an instantaneous power waveform diagram involved in an embodiment of the present invention;

[0045] Figure 6 The fourth frequency band u of the wavelet packet involved in the embodiment of the present invention is shown. (4) (t), i (4) (t) waveform diagram;

[0046] Figure 7 shows a voltage band extraction waveform diagram;

[0047] Figure 8 shows a voltage band extracted spectrum diagram;

[0048] Fig. 9 shows a current frequency band extraction waveform diagram;

[0049] Fig.10 A spectrum diagram of the current extraction waveform is shown. DETAILED DESCRIPTION

[0050] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0051] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0052] like Figure 1 As shown, according to an embodiment of the present invention, a method for measuring electric energy with respect to broadband characteristics of an electric power system includes the following steps:

[0053] S1, using the filter built into the power grid system to collect the corresponding current and voltage data;

[0054] In this step, a filter is added to the electric energy meter in the power grid system to measure only the fundamental electric energy, weakening the adverse effect of harmonics on the measurement. The voltage and current waveform signals are collected using sensors to achieve full information measurement of the waveform.

[0055] S2, preprocessing the power data to obtain effective power data, wherein the preprocessing includes amplification and filtering to eliminate noise and interference, thereby ensuring the accuracy and stability of the signal;

[0056] S3, calculating the effective power data using a preset power formula to obtain an average power of a sampling period;

[0057] S4, decomposing the electric quantity data of the electric power system to obtain a wavelet packet frequency band;

[0058] S5, performing adaptive harmonic extraction on the wavelet packet frequency band to obtain a sampling spectrum;

[0059] S6, obtaining the electric energy measurement value of the power system according to the sampling spectrum according to time integration.

[0060] In this embodiment, the electric power metering method and device for the electric power system proposed by the present invention has a maximum harmonic metering error of 2.03%. The results show that the extracted waveform retains the amplitude and phase information of the waveform well, and direct integration can be used to measure the electric power of each frequency component. Similarly, this method is used to process the remaining wavelet packet frequency bands, and the effect is also significant, and the metering error can be controlled within 3%.

[0061] like Figure 2 As shown, in the above embodiment, preferably, S3, calculating the effective power data by a preset power formula to obtain the average power of a sampling period includes the following steps:

[0062] S31, calculating the instantaneous power of the sampling point according to the effective power data by using a preset instantaneous power formula;

[0063] In this step, the metering period is set to 10 fundamental wave periods, so the metering period T c = 0.2s, to fully measure the harmonic information within 50 times, determine the ADC sampling frequency f s The frequency is 12.8kHz, and 10 sampling cycles are taken, so the data length N = 2560. The voltage and current data of the same sampling point are u(n) and i(n), and the instantaneous power of the sampling point n can be obtained.

[0064] S32: Calculate the average power of a sampling period according to the instantaneous power.

[0065] In the above embodiment, preferably, the expression of the preset instantaneous power formula is: p(n)=u(n)i(n), wherein u(n) is the voltage data in the electric quantity data at the sampling point n, i(n) is the current data in the electric quantity data at the sampling point n, and p(n) is the instantaneous power at the sampling point n;

[0066] For a metering cycle, the instantaneous power waveform is as follows: Figure 5 As shown, the expression of the average power P is: Where N is the number of sampling points in one sampling period.

[0067] like Figure 3 As shown, in the above embodiment, preferably, S5, performing adaptive harmonic extraction on the wavelet packet frequency band to obtain a sampling spectrum includes the following steps:

[0068] S51, modifying the wavelet packet frequency band according to the average power;

[0069] In this step, due to the endpoint effect, there is partial distortion at both ends of the extracted data, so this partial error is corrected by removing the first and last two fundamental wave cycles and calculating the average power.

[0070] S52, selecting a harmonic frequency band of a preset frequency from the modified wavelet packet frequency band;

[0071] S53, performing decomposition according to the fundamental wave period data corresponding to the harmonic frequency band to obtain the sampling spectrum.

[0072] In this embodiment, the overall signal of the power system is decomposed into wavelet packets, and the selected specific frequency bands are rearranged, and adaptive harmonic extraction is performed on each frequency band. Due to the endpoint effect, there is partial distortion at both ends of the extracted data, so this partial error is corrected by removing the first and last two fundamental wave periods and calculating the average power. After the correction, the extracted signals of each frequency band of voltage and current are frequency matched respectively, and the same frequency signal is directly used according to the electric energy metering formula to calculate the specific harmonic power of this metering period. Since the extracted waveform signals themselves have amplitude and phase information, the calculated electric energy is positive and negative. Positive electric energy indicates that the load side is obtaining electric energy from the power grid, and negative electric energy value indicates that energy is injected into the power grid. Therefore, the value and flow direction of each harmonic energy can be obtained, and bidirectional measurement of each harmonic can be achieved.

[0073] In this embodiment, the electric energy metering method and device developed by the present invention based on broadband measurement technology are reasonable and accurate, and the metering formula is derived by using discrete instantaneous sampling values, thereby avoiding large calculation amount and long delay. Wavelet packet frequency band decomposition and adaptive harmonic extraction are used to achieve accurate measurement of broadband signals, correct the distortion caused by endpoint effects, and improve the accuracy of metering results.

[0074] In the above embodiment, preferably, the preset frequency includes: a voltage and current signal with a sampling frequency of 12.8kHz, each frequency band can contain 8 harmonics after decomposition, the fourth wavelet packet frequency band is set to contain 25th, 27th, and 29th harmonics, and 10 fundamental wave period data are selected for decomposition. Therefore, the expression of the sampling spectrum corresponding to the voltage signal and the current signal is:

[0075] u (4) (t)=4.5sin(2π1250t+25°)+4.2sin(2π1350t+245°)+3.8sin(2π1450t+145°);

[0076] i (4) (t)=1.4sin(2π1250t+135°)+2.1sin(2π1350t+15°)+1.0sin(2π1450t+220°);

[0077] Where t is the sampling time.

[0078] In this embodiment, the u of the fourth frequency band of the wavelet packet is selected.(4) (t), i (4) The waveform of (t) is as follows Figure 6 The waveforms of the selected frequency bands are extracted each time, and the extracted waveforms of voltage and current are shown in Figure 7 , Figure 8 The corresponding spectrum is shown in Fig. 9 , Fig.10 shown.

[0079] In the above embodiment, preferably, the electric energy metering value W Tc The expression is:

[0080]

[0081] In the above embodiment, preferably, the wavelet packet frequency band is modified according to the average power by removing the wavelet packet frequency band corresponding to the first and last two fundamental wave periods and calculating the average power.

[0082] The simulation data statistics of the 4th frequency band of wavelet packet decomposition are shown in Table 1. The maximum error of harmonic measurement is 2.03%. The results show that the extracted waveform retains the amplitude and phase information of the waveform well, and direct integration can measure the electric energy of each frequency component. Similarly, this method is used to process the remaining wavelet packet frequency bands, and the effect is also significant. The measurement error can be controlled within 3%, indicating that the electric energy measurement algorithm developed by this patent based on broadband measurement technology is reasonable and accurate.

[0083] Table 1 Statistics of simulation data of metrology algorithm

[0084]

[0085]

[0086] like Figure 4 As shown, according to another embodiment of the present invention, an electric energy metering system 100 for broadband characteristics of an electric power system includes:

[0087] The power acquisition module 1 is configured to collect power data corresponding to current and voltage using a filter built into the power grid system;

[0088] A preprocessing module 2 is configured to preprocess the power data to obtain effective power data, wherein the preprocessing includes amplification and filtering to eliminate noise and interference;

[0089] The power calculation module 3 is configured to calculate the effective power data through a preset power formula to obtain the average power of a sampling period;

[0090] A frequency band decomposition module 4 is configured to decompose the electric quantity data of the electric power system to obtain a wavelet packet frequency band;

[0091] An adaptive extraction module 5 is configured to perform adaptive harmonic extraction on the wavelet packet frequency band to obtain a sampling spectrum;

[0092] The electric energy calculation module 6 is configured to obtain the electric energy measurement value of the power system according to the sampling spectrum according to time integration.

[0093] In this embodiment, the electric energy metering system of the power system proposed by the present invention has a maximum harmonic metering error of 2.03%. The results show that the extracted waveform retains the amplitude and phase information of the waveform well, and direct integration can be used to measure the electric energy of each frequency component. Similarly, this method is used to process the remaining wavelet packet frequency bands, and the effect is also significant, and the metering error can be controlled within 3%.

[0094] Based on the above Figures 1 to 3 The method shown, accordingly, an embodiment of the present application also provides a computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, the steps of the electric energy metering method for the wide-band characteristics of the power system in any of the above embodiments are implemented.

[0095] Based on this understanding, the technical solution of the present application can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (which can be a CD-ROM, USB flash drive, mobile hard disk, etc.), including a number of instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute the methods of various implementation scenarios of the present application.

[0096] Based on the above Figures 1 to 3 The method shown, and Figure 4 In the virtual device embodiment shown, in order to achieve the above-mentioned purpose, the embodiment of the present application also provides a computer device, including a storage medium and a processor; the storage medium is used to store a computer program; the processor is used to execute the computer program to implement the steps of the electric energy metering method for the wide-band characteristics of the power system in any of the above-mentioned embodiments.

[0097] Optionally, the computer device may further include a user interface, a network interface, a camera, a radio frequency (RF) circuit, a sensor, an audio circuit, a WI-FI module, etc. The user interface may include a display, an input unit such as a keyboard, etc., and the optional user interface may also include a USB interface, a card reader interface, etc. The network interface may optionally include a standard wired interface, a wireless interface (such as a Bluetooth interface, a WI-FI interface), etc.

[0098] Those skilled in the art will appreciate that the computer device structure provided in this embodiment does not limit the computer device, and may include more or fewer components, or a combination of certain components, or different component arrangements.

[0099] The storage medium may also include an operating system and a network communication module. The operating system is a program that manages and saves the hardware and software resources of the computer device, and supports the operation of information processing programs and other software and / or programs. The network communication module is used to realize communication between the components inside the storage medium, and communication with other hardware and software in the physical device.

[0100] In the present invention, the terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance; the term "plurality" refers to two or more, unless otherwise clearly defined. The terms "installed", "connected", "connected", "fixed", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; "connected" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0101] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by terms such as “upper”, “lower”, “left”, “right”, “front” and “back” are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific direction, be constructed and operated in a specific orientation, and therefore, cannot be understood as a limitation on the present invention.

[0102] In the description of this specification, the description of the terms "one embodiment", "some embodiments", "specific embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for measuring electric energy based on broadband characteristics of a power system, characterized in that: The following steps are involved: The electric quantity data corresponding to the current and voltage are collected by using the filter built into the power grid system; Preprocessing the power data to obtain effective power data, wherein the preprocessing includes amplification and filtering to eliminate noise and interference; The effective power data is calculated using a preset power formula to obtain an average power of a sampling period; Decomposing the electric quantity data of the electric power system to obtain wavelet packet frequency bands; Performing adaptive harmonic extraction on the wavelet packet frequency band to obtain a sampling spectrum; The electric energy measurement value of the power system is obtained by integrating the sampled spectrum over time.

2. The electric energy metering method for the broadband characteristics of the electric power system according to claim 1, characterized in that: The effective power data is calculated by a preset power formula to obtain the average power of a sampling period, including the following steps: Calculate the instantaneous power of the sampling point according to the effective power data by using a preset instantaneous power formula; The average power of a sampling period is calculated according to the instantaneous power.

3. The electric energy metering method for the broadband characteristics of the electric power system according to claim 2, characterized in that: The expression of the preset instantaneous power formula is: p(n)=u(n)i(n), wherein u(n) is the voltage data in the electric quantity data at sampling point n, i(n) is the current data in the electric quantity data at sampling point n, and p(n) is the instantaneous power at sampling point n; The expression of the average power P is: Where N is the number of sampling points in one sampling period.

4. The electric energy metering method for the broadband characteristics of the electric power system according to claim 3, characterized in that: Adaptively extracting harmonics from the wavelet packet frequency band to obtain a sampling spectrum comprises the following steps: Modifying the wavelet packet frequency band according to the average power; Selecting a harmonic frequency band of a preset frequency from the modified wavelet packet frequency band; The sampling spectrum is obtained by performing decomposition according to the fundamental wave period data corresponding to the harmonic frequency band.

5. The electric energy metering method for the broadband characteristics of the electric power system according to claim 4, characterized in that: The expression of the sampled spectrum is: u (4) (t)=4.5sin(2π1250t+25°)+4.2sin(2π1350t+245°)+3.8sin(2π1450t+145°); i (4) (t)=1.4sin(2π1250t+135°)+2.1sin(2π1350t+15°)+1.0sin(2π1450t+220°); Where t is the sampling time.

6. The electric energy metering method for the broadband characteristics of the electric power system according to claim 5, characterized in that: The electric energy measurement value W Tc The expression is:

7. The electric energy metering method for the broadband characteristics of the electric power system according to claim 4, characterized in that: The wavelet packet frequency band is modified according to the average power to remove the wavelet packet frequency band corresponding to the first and last two fundamental wave periods and calculate the average power.

8. An electric energy metering system for the broadband characteristics of the power system, characterized in that: include: The power acquisition module is configured to collect power data corresponding to current and voltage using a filter built into the power grid system; A preprocessing module is configured to preprocess the power data to obtain effective power data, wherein the preprocessing includes amplification and filtering to eliminate noise and interference; A power calculation module is configured to calculate the effective power data using a preset power formula to obtain an average power of a sampling period; A frequency band decomposition module is configured to decompose the electric quantity data of the electric power system to obtain a wavelet packet frequency band; An adaptive extraction module is configured to perform adaptive harmonic extraction on the wavelet packet frequency band to obtain a sampling spectrum; The electric energy calculation module is configured to obtain the electric energy measurement value of the power system according to the sampling spectrum according to time integration.

9. A readable storage medium, characterized in that: A computer program is stored thereon, and when the program is executed by a processor, the steps of the electric energy metering method for the broadband characteristics of the electric power system as described in any one of claims 1 to 7 are implemented.

10. A computer device, characterized in that: The method comprises a storage medium and a processor; the storage medium is used to store a computer program; the processor is used to execute the computer program to implement the steps of the electric energy metering method for the broadband characteristics of the power system as described in any one of claims 1 to 7.

Images