CN104123402B - The method and apparatus for calculating the line loss of distribution network - Google Patents
The method and apparatus for calculating the line loss of distribution network Download PDFInfo
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Abstract
The invention discloses a kind of method and apparatus for the line loss for calculating distribution network, the distribution network includes at least one branched line and at least one load point.Methods described includes：The reference load curve of the load point is adjusted based on the power measurement values of at least one load point, to produce the prediction load curve of at least one load point, the reference load curve is the power of load point consumption relative to the curve of time；And the line loss of distribution network is calculated based on the prediction load curve of at least one load point.By methods described and equipment, the line loss of distribution network can be more accurately calculated.
Description
Technical Field
The present invention relates to power distribution networks, and in particular to a method and apparatus for calculating line losses of a power distribution network.
Background
In the grid, power is transmitted through a backbone network, and the power is distributed to end users via a distribution network after transformation. When electric power is transmitted in a distribution network, electric energy losses, i.e. line losses of the distribution network, will occur due to the impedance of the lines in the network, which will result in economic losses for the electric power company. Therefore, managing and reducing line loss is a problem that power companies need to solve. To solve this problem, the line losses of the distribution network need to be calculated.
Two line loss calculation methods have been proposed, namely a statistical line loss calculation method and a theoretical line loss calculation method. In the statistical line loss calculation method, a total amount of power supplied to the distribution network and a total amount of power consumed by an end user are measured by an electricity meter, and a difference between the two is calculated as a line loss of the distribution network. However, in current distribution networks, the measuring equipment is not sufficient, and only a single area can be measured for a certain period of time, so this method cannot calculate line loss for a long time and for a plurality of areas. Furthermore, the line losses calculated by this method are also inaccurate, due to the time difference between the measurements made on the distribution network and the end user. In the theoretical line loss calculation method, the line loss of the distribution network is calculated using circuit theory based on parameters (e.g., voltage, impedance, etc.) of the distribution network and the load of the distribution network. Conventional theoretical line loss calculation methods include a root mean square current method, an average current method, and the like. Compared with the statistical line loss calculation method, the theoretical line loss calculation method can calculate the line loss for a long time and in a plurality of areas, and the calculation result is more accurate.
However, there are challenges in calculating line losses for a power distribution network using a theoretical line loss calculation method, thereby affecting the accuracy of such a method. First, in this method, it is necessary to select a certain day as a representative day and then calculate the line loss of the distribution network based on the load situation of the distribution network on the representative day and the like. However, since the load situation of different date types (e.g., weekdays and holidays) is very different, the selected representative day cannot represent each day of the year, which makes it not easy to select an appropriate representative day. Secondly, in order to accurately grasp the load situation of the distribution network within a day, it is necessary to install a measurement meter for each load point of the distribution network to measure its load in real time. However, such real-time measuring devices are currently only equipped in the backbone (> 220 kV) and not in the distribution network. Furthermore, even if some distribution networks are equipped with measuring devices, these measuring devices are often energy measuring devices, which can only measure energy consumption data over a period of time, but not power data, and therefore their measurement results cannot be used to calculate the theoretical line loss. In addition, although some power distribution networks are equipped with current/voltage/power measurement devices, due to limitations in communication means and cost, these devices can only provide measurement data at very low frequencies, resulting in an inability to obtain sufficient measurements to calculate line losses.
For example, in the root mean square method, the root mean square of the current values of the distribution network at 24 full points of the representative day is used to calculate the line loss Δ a of the distribution network by the following equation (1):
wherein,I1、I2、…、I24the current values of the distribution network at 24 integral points, R the resistance of the distribution network and t the time, respectively. This method uses the root mean square of a limited number of current measurements as the current value of the distribution network, which deviates significantly from the actual current value, so that the calculated line losses are not accurate.
Disclosure of Invention
The present invention has been made in view of the above problems. An object of the present invention is to provide a method and apparatus for calculating a line loss of a power distribution network, which can calculate a line loss of a power distribution network more accurately.
According to an aspect of the present invention, there is provided a method of calculating line losses of an electrical distribution network comprising at least one branch line and at least one load point, the method comprising: adjusting a reference load curve for the at least one load point based on the power measurement for the load point to produce a predicted load curve for the at least one load point, the reference load curve being a plot of power consumed by the load point versus time; and calculating a line loss of the power distribution network based on the predicted load curve of the at least one load point.
According to another aspect of the present invention, there is provided an apparatus for calculating line loss of an electricity distribution network including at least one branch line and at least one load point, the apparatus comprising: a curve generating device configured to adjust a reference load curve of the at least one load point based on the power measurement value of the at least one load point to generate a predicted load curve of the at least one load point, the reference load curve being a curve of power consumed by the load point with respect to time; and a loss calculation device configured to calculate a line loss of the power distribution network based on the predicted load curve of the at least one load point.
In the method and apparatus according to the above aspect of the invention, the actual power measurement value of a load point of the power distribution network is used to adjust the load curve of the load point so that the adjusted load curve more accurately reflects the power load at the load point, whereby the line loss of the power distribution network calculated based on the adjusted load curve is more accurate.
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The above and other objects, features and advantages of the present disclosure will become more apparent by describing in greater detail exemplary embodiments thereof with reference to the attached drawings, in which like reference numerals generally represent like parts throughout.
FIG. 1 illustrates a block diagram of an exemplary computer system/server 12 suitable for use in implementing embodiments of the present invention.
Figure 2 schematically shows an example of a simple power distribution network.
Fig. 3 shows an example of a pre-stored load curve.
Fig. 4 is a flow chart illustrating a method of calculating line loss of a power distribution network according to an embodiment of the present invention.
Fig. 5 is a diagram exemplarily illustrating a method of adjusting a reference load curve of the load point 1 shown in fig. 2.
Fig. 6 schematically shows a predicted load curve obtained by adjusting the reference load curve of the load point 2 shown in fig. 2.
Fig. 7 is a block diagram illustrating an apparatus for calculating line loss of a power distribution network according to an embodiment of the present invention.
Detailed Description
Preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
As will be appreciated by one skilled in the art, the present invention may be embodied as a system, method or computer program product. Accordingly, the present disclosure may be embodied in the form of: may be embodied entirely in hardware, entirely in software (including firmware, resident software, micro-code, etc.) or in a combination of hardware and software, and may be referred to herein generally as a "circuit," module "or" system. Furthermore, in some embodiments, the invention may also be embodied in the form of a computer program product in one or more computer-readable media having computer-readable program code embodied in the medium.
Any combination of one or more computer-readable media may be employed. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.
A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated data signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may also be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.
Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.
Computer program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C + + or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet service provider).
The present invention is described below with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable medium that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable medium produce an article of manufacture including instruction means (instructions) which implement the function/act specified in the flowchart and/or block diagram block or blocks.
The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.
FIG. 1 illustrates a block diagram of an exemplary computer system/server 12 suitable for use in implementing embodiments of the present invention. The computer system/server 12 shown in FIG. 1 is only one example and should not be taken to limit the scope of use or the functionality of embodiments of the present invention.
As shown in FIG. 1, computer system/server 12 is in the form of a general purpose computing device. The components of computer system/server 12 may include, but are not limited to: one or more processors or processing units 16, a system memory 28, and a bus 18 that couples various system components including the system memory 28 and the processing unit 16.
Bus 18 represents one or more of any of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, and a processor or local bus using any of a variety of bus architectures. By way of example, such architectures include, but are not limited to, Industry Standard Architecture (ISA) bus, micro-channel architecture (MAC) bus, enhanced ISA bus, Video Electronics Standards Association (VESA) local bus, and Peripheral Component Interconnect (PCI) bus.
Computer system/server 12 typically includes a variety of computer system readable media. Such media may be any available media that is accessible by computer system/server 12 and includes both volatile and nonvolatile media, removable and non-removable media.
The system memory 28 may include computer system readable media in the form of volatile memory, such as Random Access Memory (RAM) 30 and/or cache memory 32. The computer system/server 12 may further include other removable/non-removable, volatile/nonvolatile computer system storage media. By way of example only, storage system 34 may be used to read from and write to non-removable, nonvolatile magnetic media (not shown in FIG. 1, and commonly referred to as a "hard drive"). Although not shown in FIG. 1, a magnetic disk drive for reading from and writing to a removable, nonvolatile magnetic disk (e.g., a "floppy disk") and an optical disk drive for reading from or writing to a removable, nonvolatile optical disk (e.g., a CD-ROM, DVD-ROM, or other optical media) may be provided. In these cases, each drive may be connected to bus 18 by one or more data media interfaces. Memory 28 may include at least one program product having a set (e.g., at least one) of program modules that are configured to carry out the functions of embodiments of the invention.
A program/utility 40 having a set (at least one) of program modules 42 may be stored, for example, in memory 28, such program modules 42 including, but not limited to, an operating system, one or more application programs, other program modules, and program data, each of which examples or some combination thereof may comprise an implementation of a network environment. Program modules 42 generally carry out the functions and/or methodologies of the described embodiments of the invention.
The computer system/server 12 may also communicate with one or more external devices 14 (e.g., keyboard, pointing device, display 24, etc.), with one or more devices that enable a user to interact with the computer system/server 12, and/or with any devices (e.g., network card, modem, etc.) that enable the computer system/server 12 to communicate with one or more other computing devices. Such communication may be through an input/output (I/O) interface 22. Also, the computer system/server 12 may communicate with one or more networks (e.g., a Local Area Network (LAN), a Wide Area Network (WAN) and/or a public network, such as the Internet) via the network adapter 20. As shown, network adapter 20 communicates with the other modules of computer system/server 12 via bus 18. It should be appreciated that although not shown in the figures, other hardware and/or software modules may be used in conjunction with the computer system/server 12, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage systems, among others.
Hereinafter, a method and apparatus for calculating line loss of a power distribution network according to an embodiment of the present invention will be described in detail.
As described above, the power distribution network distributes the power delivered through the backbone network to the end user, which may include at least one branch line and at least one load point, wherein the electric devices of the end user are connected to the respective branch line at each load point to receive the power, in other words, the load point is a point at which the electric devices of the end user are connected to the respective branch circuit (or power distribution network). Figure 2 schematically shows an example of a simple power distribution network. As shown in fig. 2, the power distribution network may include 2 load points and 2 branch lines, and the consumers of end users 1 and 2 are connected to branch lines 1 and 2 at load points 1 and 2, respectively, and thus to the power distribution network, wherein the branch lines may have an impedance z1 and the branch line 2 may have an impedance z 2. In more complex distribution networks, there may be more load points and corresponding branch lines.
Since each branch line of the power distribution network has an impedance, energy consumption will inevitably occur when current flows through the branch line, resulting in line loss of the power distribution network. In an embodiment of the invention, the current of each branch line may be calculated based on the load curve of each load point, and then the line loss of the power distribution network may be calculated based on the current and the impedance of each branch circuit. As is known in the art, a load curve for a load point refers to a plot of power consumed by the load point versus time. The power consumed by the load point refers to the power consumed at the load point when viewed from the side of the power distribution network, i.e. the power consumed by the end user connected to the load point.
During daily operations, the utility company measures the power consumed by different types of end users for various time periods (e.g., weekdays, weekends, holidays, etc.), for different regions (e.g., metropolitan, small cities, rural areas, etc.), and plots the power against time based on the measured power values to obtain load curves for the various end users, which are pre-stored for use when needed. As is well known in the art, the power consumed by an end user varies depending on the type, geographic location and environment of the user, time, etc. Types of end users include, for example, industrial users, commercial users, and residential users. Industrial users can be further classified into electrolytic aluminum industrial users, food industrial users, and the like, for example. Commercial users may be further classified, for example, as office building users, shopping mall users, and the like. Thus, these pre-stored load profiles may correspond to different end user types, different geographical locations, different date types, different weather, and/or different environments, etc. Fig. 3 shows an example of a prestored load curve, which is, for example, a load curve of an industrial consumer. As shown in fig. 3, the power consumed by the end user varies continuously throughout the day, and the curve has two power peaks.
In an embodiment of the invention, for each load point of the power distribution network, a load curve may be selected from pre-stored load curves. The shape of the load curve may then be adjusted taking into account a number of factors, and the adjusted load curve used in the calculation of line loss.
In particular, for each load point, the load curve may be selected according to the characteristics of the end user to which the load point corresponds (i.e., the end user connected to the load point). The characteristics may include, for example, at least one of a type of end user, a geographic location, and environmental information. For example, first, a main type of the end user corresponding to the load point may be determined, and the main type may include, for example, the industrial user, the commercial user, or the residential user, etc., as described above. The subtype of the end user may then be determined based on the main type of the end user. As described above, for industrial users, the sub-types thereof may include electrolytic aluminum industrial users, food industrial users, and the like, and for commercial users, the sub-types thereof may include office building users, shopping mall users, and the like. Next, the geographic location (e.g., a heavily populated city or a sparsely populated country) and environmental information (e.g., indoor or outdoor, windy or non-windy, etc.) of the end user may be determined. After the attributes of the end user are determined, a load curve that matches the respective attributes (or a portion thereof) may be selected from a plurality of pre-stored load curves. For example, if a line loss on a working day is to be calculated and the end user corresponding to the load point is located in an office building of a city, a load curve obtained based on end users having the same attribute may be selected from a plurality of load curves stored in advance.
Then, the shape of the selected load curve may be adjusted according to at least one of the type of the date on which the line loss is to be calculated and the weather condition of the date, and the adjusted load curve is used as a reference load curve of the load point. In particular, as is well known in the art, the power consumed by an end user is also related to the type of date for which the line loss is to be calculated and the weather conditions for that date. For example, the same end user may consume different amounts of power on weekdays and weekends. Furthermore, the power consumed by the same end user on different days (e.g., sunny and cloudy days) is also different. Thus, in an embodiment of the invention, the shape of the selected load curve is also adjusted in dependence on at least one of the type of date on which the line loss is to be calculated and the weather conditions for that date, such that the load curve reflects the effect of the type of date and weather on the power consumed by the end user.
For example, assume that the user-selected load curve for an office building has two power peaks, one corresponding to the morning time and the other corresponding to the afternoon time. If the load curve is statistically obtained for weekends and the type of date on which the line loss is to be calculated is weekdays, the load curve as a whole can be boosted by a certain amount since office users consume more power at each moment in the weekend than on weekends. Further, if the air temperature on the date corresponding to the load curve (referred to as the first air temperature for convenience of description) is lower than the air temperature on the date on which the line loss is to be calculated (referred to as the second air temperature for convenience of description), the difference between the power consumed by the office user during the operation time and the non-operation time is higher than that during the low temperature, and therefore, the two power peaks of the load curve can be raised by a certain amount.
The amount of boost load curve and the amount of boost power peak may be determined in a number of ways. In a first way, the quantity can be roughly estimated empirically by the user and used to adjust the load curve. In a second way, the load curve can be adjusted by determining the quantities more accurately from historical data. Specifically, two load curves respectively corresponding to a weekday and a weekend may be found from load curves for the same type of user that are stored in advance by the electric power company based on historical data, and then an overall difference value of the two curves is calculated to determine a power difference due to different date types as an amount of lifting the load curves; further, it is possible to find load curves corresponding to the first and second air temperatures, respectively, from load curves stored in advance for the same type of user, and then calculate the height difference of the corresponding peaks of the two curves as the amount of raising the power peak. Of course, besides the above-mentioned ways, other ways may be adopted to adjust the curve, and the details are not described here.
In an embodiment of the present invention, for the load points of the power distribution network, the adjusted load curve described above may be used as its reference load curve to perform the calculation of the line loss according to an embodiment of the present invention. Of course, in other embodiments, the load curve selected according to the characteristics of the end user corresponding to the load point may be directly used as the reference load curve for the subsequent calculation without performing the above adjustment operation.
Next, a method of calculating line loss of a power distribution network according to an embodiment of the present invention will be described with reference to fig. 4. As described above, the power distribution network may include at least one branch line and at least one load point.
As shown in fig. 4, in step S401, the reference load curve of the at least one load point is adjusted based on the power measurement value of the load point to generate a predicted load curve of the at least one load point. As described above, the reference load curve is a plot of power consumed by the load point versus time.
As described above, it is difficult to obtain real-time power measurements of load points in the power distribution network, but power measurements at certain times may be obtained, and in embodiments of the invention, reference load curves of load points may be adjusted based on these power measurements for line loss calculations of the power distribution network.
In particular, after obtaining the power measurement value of the at least one load point, an anchor point on a reference load curve of the load point may be moved to a measurement point corresponding to the power measurement value, the anchor point being a point in time that is the same as the measurement point, i.e. a point on the load curve that has the same lateral coordinate as the measurement point. Then, the portion of the reference load curve other than the anchor point may be moved while maintaining the shape characteristic of the reference load curve. It will be appreciated that the anchor point may be other points on the load curve, such as points located near the measurement point in the abscissa direction, as desired.
This adjustment method is exemplarily described below with reference to fig. 5. Curve 1 shown in fig. 5 is a reference load curve for load point 1 of the power distribution network shown in fig. 2. In this example, assume that the power of load point 1 is measured 4 times during the day, and accordingly 4 power measurements are obtained, the four power measurements corresponding to measurement points 1-4 (shown with diamonds), respectively. As shown in fig. 5, the reference load curve for load point 1 deviates significantly from the measurement points 1-4, and therefore, an adjustment of the reference load curve is required.
Specifically, first, the anchor point on the reference load curve for that load point may be moved to the measurement point corresponding to the power measurement value. In the example shown in fig. 5, points on the load curve having the same abscissa as the measurement points 1 to 4, respectively, are set as anchor points 1 to 4 (shown by circles), and the anchor points 1 to 4 are moved onto the measurement points 1 to 4, respectively, as indicated by arrows.
Then, it is possible to move the portions of the reference load curve other than the anchor points, i.e., the portions between the respective anchor points on the curve, while maintaining the shape characteristics of the reference load curve. The shape characteristic of the reference load curve refers to a characteristic that can determine the shape or the general shape of the load curve, such as the number and location of power peaks and/or power valleys. The purpose of maintaining the shape characteristic of the reference load curve is to make the shape of the adjusted load curve (i.e. the predicted load curve) substantially the same as the shape of the reference load curve, since the reference load curve should be substantially the same as the actual load curve at the load point, although it may deviate from the actual load curve at the load point in a specific value.
Can be used in various waysTo move the portion of the moving reference load curve other than the anchor point. In one approach, the portion between anchor point 1 and anchor point 2 may be divided into a plurality of sections (for convenience of description, n sections are assumed, where n ≧ 2 and the larger the better), wherein the power peak or power valley of the reference load curve preferably lies in one section. The power values of the n segments can then be divided by the ratio d, respectively1、d2、…dnWherein the ratio d1、d2、…dnThe ratio d of the value of (1) at the anchor point to the power value of the measurement point 1LAnd the ratio d of the power values of the anchor point 2 and the measurement point 2rAnd d isL、d1、d2、…dn、drIn an equal ratio series. In this way, by dividing the power value of each section between anchor point 1 and anchor point 2 by a different ratio, the portion between anchor point 1 and anchor point 2 can be moved. The sections between other anchor points may be similarly moved while maintaining the characteristics of the reference load curve. In another mode, dL、d1、d2、…dn、drMay be in an arithmetic progression. In yet another mode, d1、d2、…dnCan take dLAnd drAnd is incremented by (d)L<drTime) or decreasing (d)L>drTime) other values.
By adjusting the reference load curve for a load point as described above, the adjusted reference load curve (i.e., the predicted load curve) can be made to pass through all the measurement points obtained for that load point, so that the predicted load curve is closer to the actual load curve for that load point.
The above process may be repeated for each of the remaining load points of the power distribution network to determine a predicted load curve thereof. In the example shown in fig. 2, an example of the predicted load curve of the load point 2 determined in the above-described manner is shown in fig. 6.
Returning to fig. 4, in step S402, a line loss of the power distribution network is calculated based on the predicted load curve of the at least one load point.
In brief, based on the predicted load curve of the at least one load point, the current on the at least one branch line may be calculated, and then the line loss of the electricity distribution network may be calculated by an approximate time integration operation based on the current on the at least one branch line.
In particular, power flow calculation methods known in the art may be used to calculate line losses of the power distribution network based on the predicted load curve. In the following, a method of calculating the line loss of an electrical distribution network based on a predicted load curve will be exemplarily explained in connection with an example of the electrical distribution network shown in fig. 2, the predicted load curves of load points 1 and 2 shown in fig. 2 being shown in fig. 5 and 6, respectively.
As shown in FIG. 2, assume that the output voltage at the backbone bus is U0The complex power and voltage at load point 1 are S1And U1The complex power and voltage at load point 2 are S2And U2. Further, as described above, the impedances of the branch line 1 and the branch line 2 are z, respectively1And z2. Here, U0、z1And z2Are known. For the sake of simplicity, the complex powers S of load point 1 and load point 2 are ignored here1And S2Part of reactive power in, thus, S1Can be simplified to P1，S2Can be simplified to P2Wherein P is1And P2Active power for load points 1 and 2, which can be determined from the predicted load curves for load points 1 and 2, respectively, and, correspondingly, impedance z1And z2Can be respectively simplified into resistors r1And r2。
As can be seen from the circuit theory, at any time, it is only necessary to determine the current I of the branch lines 1 and 21And I2The power loss P of the distribution network can be calculated by the following equation (2)loss：
The line loss E of the power distribution network over a period of time can then be determined by integrating the power loss over time tlossAs shown in the following formula (3):
mathematically, the power loss P is calculated for a sufficient number of moments in the time periodlossIn the case of (3), the above formula (3) can be simplified as:
where m is the number of times, e.g., 24 or more, and i is an integer.
As an example, an iterative method may be used to determine the currents I of the branch lines 1 and 2 based on the predicted load curve1And I2. Specifically, for any time, U will be1The values during each iteration are noted …, mixing U with2The values during each iteration are noted … are provided. Furthermore, assume that the current on the line between the end user 1 and the load point 1 is IL1Its value during each iteration is noted as …, the current on the line between end user 2 and load point 2 is IL2Its value during each iteration is noted as …。
Initially, can be provided withThen
Then, the need forBy reduced amountAnd need toBy reduced amount
From this, the next iteration can be determined
For theAnddetermine it relative to U in the last iteration1And U2Value of (i.e. 1)And) Is greater than a predetermined threshold. If the rate of change is greater than a predetermined threshold, based onAndthe above iterative process continues until the rate of change is not greater than a predetermined threshold. Otherwise, when the rate of change is not greater than a predetermined threshold, the iterative process is stopped and I is used1And I2As the current value in the branch line. The predetermined threshold value can be selected according to actual needs, for example, 10－6。
The above calculation process is repeated for each time instant, thereby calculating the current values in the respective branch lines of the power distribution network at that time instant. Then, by the above equations (2) and (4), the line loss of the distribution network can be calculated.
An apparatus for calculating line losses of an electrical distribution network according to an embodiment of the present invention is described below with reference to fig. 7. The apparatus may perform the method described above with reference to fig. 4 by various means described below.
As shown in fig. 7, the line loss calculation apparatus 700 may include a curve selection device 701, a curve adjustment device 702, a curve generation device 703, and a loss calculation device 704.
The curve selection device 701 selects one load curve from the pre-stored load curves for each load point of the power distribution network. Specifically, the curve selecting means 701 may select a load curve for each load point according to the characteristics of the end user corresponding to the load point. As mentioned above, the characteristics may comprise, for example, at least one of a type of end user, a geographical location, and environmental information.
The profile adjusting means 702 adjusts the shape of the load profile selected by the profile selecting means 701 in accordance with at least one of the type of the date on which the line loss is to be calculated and the weather condition of the date. The curve adjusting means 702 may perform this adjustment operation in the manner described above, and a detailed description thereof is omitted here to avoid redundancy.
It should be appreciated that although the curve selection means 701 and the curve adjustment means 702 are shown as part of the apparatus 700 in fig. 7, in the apparatus 700 these two means may not be provided, but the above selection and adjustment operations may be performed manually, for example by a user, and the resulting reference load curve provided to the apparatus 700. Furthermore, in other embodiments, only the curve selection means 701 may be provided without the curve adjustment means 702, so that the load curve selected by the curve selection means 701 is directly used as the reference load curve for the subsequent calculation.
The curve generating device 703 adjusts the reference load curve of the at least one load point based on the power measurement of the at least one load point to generate a predicted load curve of the at least one load point. As described above, the reference load curve is a plot of power consumed by the load point versus time. The curve generating device 703 may adjust the reference load curve in the manner described above with reference to fig. 4 and 5 to generate the predicted load curve. Specifically, after receiving the power measurement value of the at least one load point from the outside, the curve generating device 703 may move an anchor point on a reference load curve of the load point to a measurement point corresponding to the power measurement value, where the anchor point is a point having the same time as the measurement point, that is, a point having the same lateral coordinate as the measurement point on the load curve. Then, the portion of the reference load curve other than the anchor point may be moved while maintaining the shape characteristic of the reference load curve. The shape characteristic of the reference load curve refers to a characteristic that can determine the shape or the general shape of the load curve, such as the number and location of power peaks and/or power valleys. It will be appreciated that the anchor point may be other points on the load curve, such as points located near the measurement point in the abscissa direction, as desired.
The loss calculation means 704 calculates a line loss of the power distribution network based on the predicted load curve of the at least one load point. In brief, the loss calculating means 704 may calculate the current on the at least one branch line based on the predicted load curve of the at least one load point, and may then calculate the line loss of the power distribution network by (approximate) time integration operation based on the current on the at least one branch line. The loss calculating device 704 may calculate the line loss of the power distribution network by the method described above with reference to fig. 2 and 4, which is not described herein again.
In the above method and apparatus for calculating a line loss according to an embodiment of the present invention, a load point reference load curve obtained based on historical data is optimized according to a measurement point such that a resulting predicted load curve is closer to an actual load curve of the load point. Furthermore, the above-described method of calculating line loss according to an embodiment of the present invention actually calculates line loss of a power distribution network by (approximate) integration operation over time, and the calculation result is more accurate than the conventional method of calculating line loss by the above equation (1) based on several current measurement values. Furthermore, the application of the above-described method and apparatus according to embodiments of the present invention is not limited to specific times and areas, and thus the line loss of the distribution network may be calculated for long periods of time and for multiple areas.
The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terms used herein were chosen in order to best explain the principles of the embodiments, the practical application, or technical improvements to the techniques in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.
Claims (8)
1. A method of calculating line losses of an electrical distribution network comprising at least one branch line and at least one load point, the method comprising:
adjusting a reference load curve for the at least one load point based on the power measurement for the load point to produce a predicted load curve for the at least one load point, the reference load curve being a plot of power consumed by the load point versus time; and
calculating a line loss for the power distribution network based on the predicted load curve for the at least one load point;
wherein adjusting the reference load curve for the at least one load point based on the power measurement for that load point comprises:
moving an anchor point on a reference load curve to a measurement point corresponding to the power measurement value, the anchor point being the same point in time as the measurement point; and
and moving the part except the anchor point on the reference load curve under the condition of keeping the shape characteristic of the reference load curve.
2. The method of claim 1, further comprising:
and selecting a load curve from a plurality of pre-stored load curves as the reference load curve according to at least one of the type, the geographical position and the environmental information of the user corresponding to the at least one load point.
3. The method of claim 1, further comprising:
selecting a load curve from a plurality of pre-stored load curves according to at least one of the type, the geographic position and the environmental information of the user corresponding to the at least one load point; and
adjusting the shape of the selected load curve as the reference load curve according to at least one of a type of a date for which the line loss is to be calculated and a weather condition of the date.
4. The method of any of claims 1-3, wherein calculating the line loss of the power distribution network based on the predicted load curve of the at least one load point comprises:
calculating a current on the at least one branch line based on a predicted load curve of the at least one load point;
calculating a line loss of the power distribution network by an approximate time integration operation based on the current on the at least one branch line.
5. An apparatus for calculating line losses of an electrical distribution network comprising at least one branch line and at least one load point, the apparatus comprising:
a curve generating device configured to adjust a reference load curve of the at least one load point based on the power measurement value of the at least one load point to generate a predicted load curve of the at least one load point, the reference load curve being a curve of power consumed by the load point with respect to time; and
a loss calculation device configured to calculate a line loss of the power distribution network based on the predicted load curve of the at least one load point;
wherein the curve generating means moves an anchor point on a reference load curve to a measurement point corresponding to the power measurement value, and moves a portion of the reference load curve other than the anchor point, while maintaining a shape characteristic of the reference load curve, to adjust the reference load curve, wherein the anchor point is a point having the same time as the measurement point.
6. The apparatus of claim 5, further comprising:
a profile selection device configured to select a load profile from a plurality of pre-stored load profiles as the reference load profile according to at least one of a type, a geographical location, and environmental information of a user corresponding to the at least one load point.
7. The apparatus of claim 5, further comprising:
a curve selection device configured to select a load curve from a plurality of pre-stored load curves according to at least one of a type, a geographical location, and environmental information of a user corresponding to the at least one load point; and
a curve adjusting device configured to adjust a shape of the selected load curve as the reference load curve in accordance with at least one of a type of a date on which the line loss is to be calculated and a weather condition of the date.
8. The apparatus according to one of claims 5 to 7, wherein the loss calculation means calculates the current on the at least one branch line based on a predicted load curve of the at least one load point and calculates the line loss of the electricity distribution network by an approximate time integration operation based on the current on the at least one branch line.
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| CN102033999A (en) * | 2010-12-10 | 2011-04-27 | 天津天大求实电力新技术股份有限公司 | Load distribution based method for calculating recently planned annual line loss of medium-voltage distribution network |
| CN102663504A (en) * | 2012-04-06 | 2012-09-12 | 山东电力集团公司枣庄供电公司 | Power distribution network line loss evaluation method based on charge probability distribution function |
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| CN102033999A (en) * | 2010-12-10 | 2011-04-27 | 天津天大求实电力新技术股份有限公司 | Load distribution based method for calculating recently planned annual line loss of medium-voltage distribution network |
| CN102663504A (en) * | 2012-04-06 | 2012-09-12 | 山东电力集团公司枣庄供电公司 | Power distribution network line loss evaluation method based on charge probability distribution function |
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