A meter area identification method based on nonlinear power consumption load

Abstract

The present application relates to the technical field of power internet of things, and particularly relates to a meter area identification method based on nonlinear power load, which selects a time period when the power load level of a meter area is in a trough in the meter area to be identified by using the physical characteristic that the energized working period of the nonlinear power load will raise the energy of noise signals in the voltage sampling data of the meters in a larger distance on the same power supply line, then connects a nonlinear power load with larger power to some selected positions in the power supply line of the meter area, and makes these loads intermittently energized by using the timing power supply function of a programmable timing socket, so that each meter in the power information collection network belonging to the meter area collects voltage data in the time period and extracts the harmonic noise components to perform signal energy comparison and analysis, thereby realizing the identification of the meter area affiliation of the meter.

Description

Technical Field

[0001] This invention relates to the field of power Internet of Things (IoT) technology, and specifically to a method for identifying meter distribution areas based on nonlinear power load. Background Technology

[0002] In the operation and management of low-voltage distribution networks, the electricity management department manages and maintains operations based on the transformer substation (or transformer area). A transformer substation comprises all the electrical equipment along its power supply lines. Management personnel frequently need to verify user records to ensure accuracy and provide correct management data for marketing management. This includes information such as the substation affiliation of user records, the power phase and operating phase sequence of user equipment, etc. This data is fundamental for ensuring load balance within the substation, reducing load imbalance losses, and ensuring accurate line losses within the substation. It is a basic element for the construction of a smart grid.

[0003] Most existing transformer substation user identification devices identify substation information based on whether direct communication is used via power line carrier technology. However, this technology is easily affected by factors such as "shared high voltage", "shared ground", and "shared cable trench". As a result, the carrier signal cannot be completely isolated by the transformer and can still couple to other transformers, causing crosstalk in cross-substation communication, which leads to a decrease in the accuracy of substation identification. Summary of the Invention

[0004] The purpose of this invention is to provide a method for identifying electricity meter distribution areas based on nonlinear electrical loads, aiming to solve the cross-area crosstalk problem of traditional distribution area identification technology based on power line carrier technology and improve the accuracy of distribution area identification.

[0005] To achieve the above objectives, the present invention provides a method for identifying electricity meter zones based on nonlinear electrical loads, comprising the following steps:

[0006] Management personnel manually select the location for power line connection;

[0007] Nonlinear electrical loads are connected to the power supply line access points respectively;

[0008] Management personnel will intermittently synchronize power supply and power outages;

[0009] Before the identification time begins, the administrator sends a transformer area identification command to all meters in the subnet;

[0010] Each meter collects voltage sampling data according to the requirements of the transformer area identification command;

[0011] The meter makes a decision based on the voltage sampling data and reports the decision result.

[0012] The judgment result will be reconfirmed;

[0013] The identification of electricity meters in the still-to-be-determined area and neighboring areas;

[0014] For meters that cannot be identified after being compared with neighboring transformer substations, the substation affiliation is determined manually.

[0015] The meter distribution area identification method based on nonlinear electrical load is based on a two-layer hybrid communication network architecture, which includes a master station system, several distribution transformers and several distribution areas. The master station system is a remote communication network, and the number of distribution transformers and distribution areas corresponds one-to-one.

[0016] The power supply line at the power supply line access location belongs to a specific distribution transformer, and there are multiple electricity meters in the physical space adjacent to the power supply line.

[0017] The nonlinear electrical loads are all connected to the power supply line through a digital timing socket whose power-on and power-off times can be manually configured.

[0018] During the process of intermittently synchronizing power supply and power cut-off by management personnel, the management personnel select a period of time with a low power load level by using the power meter data of the main power meter of the transformer area, and then manually configure all digital timer sockets to intermittently synchronize power supply and power cut-off during that period.

[0019] The process of intermittently synchronizing power supply and power outage involves each device being powered on for T seconds and then powered off for 3T seconds, with a total of K / 4 power-on cycles, where K is divisible by 4, and the identification time is T×K seconds.

[0020] The transformer substation identification command includes the equipment number of the distribution transformer, the start time of the identification period, the end time of the identification period, and the duration T of an identification sub-period.

[0021] The judgment result is used to explain the substation affiliation of the electricity meter, including two specific situations: substation affiliation to transformer A and substation affiliation unknown, where A is the number of the distribution transformer.

[0022] In the process of reconfirming the judgment results, if a meter's two judgment results show that it belongs to the transformer A's substation more than once, then the final judgment result is that it belongs to the transformer A's substation. For meters whose two judgment results both show that the substation affiliation is unclear, the main station will add these meters to the substation undetermined list.

[0023] This invention provides a method for identifying electricity meter distribution areas based on nonlinear electrical loads. It utilizes the physical characteristic that the operation of nonlinear electrical loads during their energizing periods increases the energy of noise signals in the voltage sampling data of meters over a considerable distance on the same power supply line. Within the distribution area to be identified, a time period when the load level is at its lowest is selected. Then, a high-power nonlinear electrical load is connected to selected locations along the power supply line of that area. These loads are then intermittently energized using a programmable timer socket. Each meter belonging to the electricity information collection network of that distribution area collects voltage data during this time period and extracts harmonic noise components for signal energy comparison and analysis, thereby enabling the meter to identify its own distribution area affiliation. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a flowchart illustrating a method for identifying meter zones based on nonlinear electrical loads according to the present invention.

[0026] Figure 2 This is a schematic diagram of a two-layer hybrid communication network architecture for a meter station area identification method based on nonlinear electrical load in this invention.

[0027] Figure 3 This is a distribution diagram of the energization and de-energization periods of the nonlinear electrical load according to the present invention. Detailed Implementation

[0028] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0029] Please see Figure 1 This invention proposes a method for identifying electricity meter zones based on nonlinear electrical loads, comprising the following steps:

[0030] S1: Management personnel manually select the location for power line connection;

[0031] S2: Connect nonlinear electrical loads at the respective power supply line access points;

[0032] S3: Management personnel will intermittently synchronize power supply and power outage;

[0033] S4: Before the identification time begins, the administrator sends a transformer area identification command to all meters in the subnet;

[0034] S5: Each meter collects voltage sampling data according to the requirements of the transformer area identification command;

[0035] S6: The meter makes a decision based on the voltage sampling data and reports the decision result;

[0036] S7: The judgment result is reconfirmed;

[0037] S8: Identify the electricity meters in the still-to-be-determined transformer area and the adjacent transformer areas;

[0038] S9: For meters that cannot be identified after being compared with neighboring transformer substations, the substation affiliation is determined manually.

[0039] Nonlinear electrical loads are common in low-voltage distribution networks. Various power converters generate harmonic voltages and currents. Under stable operating conditions, the converter's switching valves simultaneously alter the voltage and current waveforms at both the AC and DC terminals. This waveform distortion generates harmonics in the circuit. Certain lighting fixtures also generate harmonics in the power system. Gas discharge lamps, especially fluorescent lamps, exhibit severe nonlinearity, producing a large number of odd-order harmonic currents. In fluorescent lamps, voltage builds up every half-cycle until the lamp is lit. When lit, the fluorescent lamp exhibits negative resistance, and its current is limited by an inductive nonlinear ballast, resulting in current distortion. Rotating electrical machines are also a major source of harmonics in power systems. The coils of rotating electrical machines are embedded in slots. Since these slots cannot be perfectly sinusoidally distributed, the resulting magnetomotive force is distorted, and the defects in the winding distribution generate spatial harmonics. Furthermore, similar to transformers, magnetic saturation in motors also generates harmonics.

[0040] During the dynamic operation of a radio station area, the amplitude and frequency of the AC voltage and current electrical quantities on its power supply line are not ideal sinusoidal waveforms with fixed amplitude and frequency; in fact, they are all real variables, referred to as time-varying amplitude-frequency signals. The voltage signal can be expressed as:

[0041] V(t)=A(t)cos[2πf(t)+θ]+ω(t) (1)

[0042] Where t represents time, V(t) represents the voltage curve amplitude, A(t) represents the amplitude, f(t) represents the curve frequency, θ represents the initial phase, and ω(t) represents the noise signal caused by various factors on the power supply line. The amplitude and frequency parameters generally change slowly over time, while the occurrence of noise is highly random and cannot be effectively predicted.

[0043] In addition to traditional metering and data collection functions, smart meters also communicate with neighboring meters via embedded communication modules. The electricity consumption information collection system is a key component of the smart power Internet of Things (IoT) system; please refer to [link to relevant documentation]. Figure 2 The entire system adopts a two-layer hybrid network architecture to achieve bidirectional data transmission between the main station system and its subordinate communication nodes. The lower layer is called the local communication network, with the concentrator as the cluster head. It is usually based on a station area as the basic unit, and the communication nodes within the station area form a multi-hop distributed self-organizing network. The upper layer is called the remote communication network, which is a centralized one-hop access network. The concentrators of each station area access the base station through 3G / 4G / 5G operator cellular communication modes.

[0044] The essence of the problem of meter area identification is to determine which power transformer the power supply line to which the smart meter belongs. This is based on the physical phenomenon that nonlinear electrical loads will generate a large number of harmonic noise signals on the power supply line they are connected to and transmit them over long distances along the line.

[0045] Furthermore, the present invention will be further described in conjunction with specific implementation steps:

[0046] Step S1: To locate all the meters belonging to a certain transformer A, the management personnel manually locate some power line access points beforehand. These locations must meet the following conditions:

[0047] 1) The power supply line belongs to transformer A;

[0048] 2) There are many electricity meters located near the physical space of the power supply line;

[0049] Step S2: The management personnel, as identified in Step S1, connect one non-linear electrical load to each of these locations. Each load is connected to the power supply line via a digital timer socket with manually configurable power-on and power-off times. The non-linear electrical loads should be selected with the highest possible power while ensuring compliance with the electrical safety requirements of the distribution area.

[0050] Step S3: The management personnel use the electricity meter data from the main power meter in the distribution area to select a period with low electricity load. Then, through manual configuration, all digital timer sockets are intermittently powered on and off synchronously during this period. Specific details are as follows... Figure 3 As shown:

[0051] Each device operates for T seconds after each power-on cycle, and then is powered off for 3T seconds. A total of K / 4 power-on cycles are performed (Note: K is divisible by 4), meaning the total recognition time is T×K seconds.

[0052] Step S4: Before the recognition time begins, the administrator will... Figure 2 The communication network of the electricity information collection system shown sends a transformer area identification command to all meters in the local communication subnet of the neighboring transformer A. The command will include relevant parameters of the identification time period, including the equipment number of transformer A, the start time of the identification time period, the end time of the identification time period, and the time length T of one identification sub-time period.

[0053] Step S5: After receiving the identification command, each meter collects voltage sampling data within the identification period of the transformer area according to relevant parameters. Let the voltage data sampling frequency of the meter be P sample points / second, then the voltage sampling data of that meter within the identification period of the transformer area is recorded as:

[0054]

[0055] The electricity meter will perform the following processing measures on the data it collects:

[0056] Using voltage sampling data of T seconds as the basic unit of data processing, it is assumed that the parameters (including amplitude, frequency and initial phase) of the sine wave signal in equation (1) are relatively stable within 1 second, and a numerical evaluation is performed on them. At present, the power quality of the domestic power distribution network is relatively good, and the nonlinear electrical load in the line will not cause serious distortion of the sine wave. Therefore, the energy of the noise term in equation (1) is significantly lower than the energy of the sine wave, that is, the signal-to-noise ratio of the signal in equation (1) is very high. At the same time, there are many publicly published mature algorithms for sine wave parameter estimation. Therefore, no specific parameter estimation algorithm is provided here. It is assumed that in the k-th time period, the evaluation values ​​of the three parameters corresponding to the sine wave of T seconds are as follows: and

[0057] For the sampling data D of the kth time period in equation (2) k =[d kTP-TP+1 ,x kTP-TP+1 ,...,x kTP In the time domain, the sinusoidal signal component is directly subtracted, and the remaining signal is considered to be the noise signal in the line.

[0058]

[0059] Calculate the energy of the remaining signal in each time period, denoted as .

[0060] For the energy data of the remaining signals mentioned above, the following differential calculation is performed, grouping them into pairs: Δ n =E 2n-1 -E 2n n=1,...,K / 2

[0061] Regarding the above data Δ n Given n = 1, ..., K / 2, calculate the odd-numbered subsequences [Δ1, Δ3, ..., Δ...]. K / 2-1 ] and even subsequences [Δ2, Δ4, ..., Δ K / 2 The number of elements in the array with a value greater than 0 is denoted as λ1 and λ2.

[0062] Step S6: Finally, based on the values ​​of λ1 and λ2, the meter makes the following decision:

[0063]

[0064] After the judgment is made, the electricity meter will be used through Figure 1 The communication network of the electricity information collection system shown reports its own judgment results to the main station;

[0065] Step S7: By analyzing the difference between the total electricity metering data of transformer A and the sum of the metering data of those transformer substations that reported as belonging to transformer A, if the difference falls within a reasonable range of substation line loss, it indicates that the meters belonging to transformer A have been found. If the difference is too large, it indicates that some meters have not yet been found, and the line connection positions of these non-linear loads can be adjusted appropriately before another round of substation identification. After completion, if a meter's result in belonging to transformer A at least once in two judgments, the final judgment result is that it belongs to transformer A. For meters whose substation affiliation is unclear in both judgments, the main station adds these meters to the substation pending determination list.

[0066] Step S8: The main site will use the same steps to identify the distribution area of ​​neighboring transformers that have overlapping power supply lines with transformer A. If the affiliation of the meters in the distribution area to be determined has been determined, they will be removed from the list.

[0067] Step S9: After the main station completes the identification of transformer A and its neighboring transformers, if there are still meters on the list of undetermined transformer areas, the information of these meters is sent to the management personnel, and the affiliation of the transformer areas is determined manually.

[0068] Specifically, the theoretical basis of the meter area identification scheme of the present invention is: for a meter installed on a certain power supply line, if a large-power nonlinear electrical load is also connected within a certain range of its line, then... Figure 3 During the identification period shown, in the sub-period of power-on operation, the operation of nonlinear electrical loads will generate harmonic signals on the power supply line and cause a certain degree of distortion of the sinusoidal waveform signal. Although the harmonic characteristics generated by different nonlinear electrical loads are quite different and it is difficult to define a model, they can all be uniformly represented in the time domain as an increase in the energy value of the noise signal in equation (1). Therefore, its energy value is very likely to be greater than the noise energy value of its adjacent time period with the same electron-out time period. As for two adjacent electron-out time periods, since there is no artificial directional intervention, there are many factors affecting the noise signal energy in the voltage sampling signal of the meter and the randomness is very strong. Therefore, statistically speaking, the probability of the difference between the two noise energy values ​​being positive or negative is 0.5, that is...

[0069] pr(E 2n-1 -E 2n >0 | The 2n-1 and 2nth time periods are both power outage periods)

[0070] =pr(E 2n-1 -E 2n ≤0|The (2n-1)th and 2nth time periods are both power outage periods) = 0.5

[0071] and pr(E) 2n-1 -E 2n >0 | The (2n-1)th and 2nth time periods are the power-on and power-off periods, respectively) >0.5

[0072] The symbol pr(x|y) represents the probability of event x occurring given that event y is true.

[0073] Therefore, for an electricity meter, if its parameter (3) is... No significantly greater than If the probability value exceeds 0.15, it means that during the identification period, the voltage sampling signal of the meter was basically unaffected by the harmonic signals of the nonlinear electrical load. Therefore, there are two possibilities:

[0074] 1) The meter and the non-linear load do not belong to the same transformer;

[0075] 2) Or the meter and the nonlinear load belong to the same transformer, but the meter line is installed outside the influence range of the harmonic signals of these nonlinear loads.

[0076] In this case, the possibility of 2) can be greatly reduced by appropriately adjusting the line connection location of the nonlinear electrical load during the second identification process.

[0077] In summary, the transformer substation identification method of the present invention utilizes the physical characteristic that nonlinear electrical loads will raise the energy of noise signals in the voltage sampling data of meters over a large distance on the same power supply line during the energized operation period. By designing a special time pattern for the energized and de-energized operation of a nonlinear electrical load, it can accurately determine whether the meter is affected by the nonlinear electrical load, and thereby identify the substation affiliation between the meter and the transformer.

[0078] Furthermore, to verify the accuracy of the identification algorithm, this invention also proposes a specific embodiment, which is tested in an old residential community, where the entire community is powered by two back-to-back transformers (denoted as transformer A and transformer B), and the power supply lines of the two transformers are intersected in some areas of the community.

[0079] First, manual methods were used to identify the transformer substations of 756 meters in the two substations. Of these, 350 meters belonged to transformer A and 406 meters belonged to transformer B. The test was conducted in the first week of winter, when local residents were generally not using air conditioning.

[0080] To minimize noise interference from other electrical loads, all tests were conducted in the early morning hours. The nonlinear electrical loads used in the tests were existing water pumps and blower motors in the underground parking lot of the two communities (Note: the line access locations of these devices could not be adjusted). The duration of each operation was T = 30 seconds, the sampling frequency of the electricity meter voltage was P = 7200 sample points / second, and the time for identifying the transformer area was 4 hours. The test lasted four days. On the first day, transformer A was identified in the early morning, and 345 meters were determined to belong to the transformer A area. After comparison, all these determinations were correct. On the second day, transformer B was identified in the early morning, and 399 meters were determined to belong to the transformer B area. After comparison, all these determinations were also correct. Subsequently, the testers added a small 3kW motor as a new non-linear electrical load. On the third day, it was connected to the power supply line of transformer A in the cross-distribution area of ​​the two transformers. On the fourth day, it was connected to the power supply line of transformer B in the cross-distribution area of ​​the two transformers. Five more meters were determined to belong to the transformer A area, and the determinations were correct. Fifteen more meters were determined to belong to the transformer B area, and the determinations were correct. Finally, only two meters remained on the list of meters to be determined.

[0081] This experiment involved 756 electricity meters, and the substation affiliation of 754 of them was determined with a 100% accuracy rate, thus verifying the reliability of the present invention.

[0082] The above description discloses only one preferred embodiment of the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art will understand that all or part of the processes of the above embodiments can be implemented, and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for identifying electricity meter zones based on nonlinear electrical load, characterized in that, Includes the following steps: Management personnel manually select the location for power line connection; Nonlinear electrical loads are connected to the power supply line access points respectively; The power supply line at the power supply line access location belongs to a specific distribution transformer, and there are multiple electricity meters in the physical space adjacent to the power supply line; All nonlinear electrical loads are connected to the power supply line through a digital timing socket with manually configurable power-on and power-off times. Management personnel will intermittently synchronize power supply and power outages; The process of intermittently synchronizing power supply and power outage is as follows: each device is powered on for T seconds and then powered off for 3T seconds, and a total of K / 4 power-on operations are performed, where K is divisible by 4, and the identification time is T×K seconds. Before the identification time begins, the administrator sends a transformer area identification command to all meters in the subnet; The transformer substation identification command includes the equipment number of the distribution transformer, the start time of the identification period, the end time of the identification period, and the duration T of an identification sub-period. Each meter collects voltage sampling data according to the requirements of the transformer area identification command; After receiving the identification command, each meter collects voltage sampling data for the identification period of the transformer area according to relevant parameters. Let the voltage data sampling frequency of the meter be P sample points / second, then the voltage sampling data of the meter during the identification period of the transformer area is recorded as: During sampling, voltage sampling data in T seconds is used as the basic unit of data processing. The parameters of the sinusoidal signal are extracted for numerical evaluation, including amplitude, frequency and initial phase. Assuming that in the k-th time interval, the evaluation values ​​of the three parameters corresponding to the sine wave with a time interval of T seconds are as follows: and For the sampling data D in the k-th time period k =[d kTP-TP+1 ,x kTP-TP+1 ,...,x kTP In the time domain, the sinusoidal signal component is directly subtracted, and the remaining signal is considered as noise in the line. Calculate the energy of the remaining signal in each time period, denoted as . For the energy data of the remaining signals mentioned above, the following differential calculation is performed, grouping them into pairs: Δ n =E 2n-1 -E 2n n=1,...,K / 2 Regarding the above data Δ n Given n = 1, ..., K / 2, calculate the odd-numbered subsequences [Δ1, Δ3, ..., Δ...]. K / 2-1 ] and even subsequences [Δ2, Δ4, ..., Δ K / 2 The number of elements in the array with a value greater than 0 is denoted as λ1 and λ2. The meter makes a decision based on the voltage sampling data and reports the decision result. Based on the values ​​of λ1 and λ2, the meter makes the following decision: The judgment result will be reconfirmed; The identification of electricity meters in the still-to-be-determined area and neighboring areas; For meters that cannot be identified after being compared with neighboring transformer substations, the substation affiliation is determined manually. The meter distribution area identification method based on nonlinear electrical load is based on a two-layer hybrid communication network architecture, which includes a master station system, several distribution transformers and several distribution areas. The master station system is a remote communication network, and the number of distribution transformers and distribution areas corresponds one-to-one.

2. The meter area identification method based on nonlinear electrical load as described in claim 1, characterized in that, During the intermittent synchronous power supply and power cut-off process, the management personnel use the power meter data of the main power meter in the distribution area to select a period of time with a low power load level, and then manually configure all digital timer sockets to intermittently synchronize power supply and power cut-off during that period.

3. The meter area identification method based on nonlinear electrical load as described in claim 1, characterized in that, The judgment result is used to explain the substation affiliation of the electricity meter, including two specific situations: substation affiliation to transformer A and substation affiliation that is unclear, where A is the number of the distribution transformer.

4. The meter area identification method based on nonlinear electrical load as described in claim 1, characterized in that, During the reconfirmation of the judgment results, if a meter's two judgment results show that it belongs to transformer A's substation more than once, then the final judgment result is that it belongs to transformer A's substation. For meters whose two judgment results both show that the substation affiliation is unclear, the main station will add these meters to the substation pending determination list.

Images