Harmonics Measurement in Power Grids

Abstract

The subject-matter relates to a method, performed by at least one apparatus, including: determining of a correction factor for at least one first voltage transformer arranged in a power grid, the correction factor being indicative of a correction for obtaining correct measured values measured by the at least one first voltage transformer, wherein the determining of the correction factor of the at least one first voltage transformer being performed at least partially based on a first measured voltage of the at least one first voltage transformer and a second measured voltage of the at least one first voltage transformer, wherein the second voltage of the at least one first voltage transformer is determined at least partially based on a known transfer function of at least one second voltage transformer and the first voltage of the at least one first voltage transformer is determined without taking into account the known transfer function of the at least one second voltage transformer; determining a calibration factor for the at least one first voltage transformer based at least in part on the determined correction factor; and outputting or causing the output of the determined calibration factor. The subject matter further relates to a correspondingly configured apparatus and a system.

Claims

1. A method performed by at least one apparatus, comprising: determining of a correction factor for at least one first voltage transformer arranged in a power grid, the correction factor being indicative of a correction for obtaining correct measured values measured by the at least one first voltage transformer, wherein the determining of the correction factor of the at least one first voltage transformer being performed at least partially based on a first measured voltage of the at least one first voltage transformer and a second measured voltage of the at least one first voltage transformer, wherein the second measured voltage of the at least one first voltage transformer is determined at least partially based on a known transfer function of at least one second voltage transformer and the first measured voltage of the at least one first voltage transformer is determined without taking into account the known transfer function of the at least one second voltage transformer, thereby the second measurement of the first transformer is multiplied by the quotient from the frequency-dependent measurements of the second transformer divided by the previously recorded frequency-dependent first measurements of the first transformer, this quotient being referred to as the transfer function, and the correction factor for a frequency range from 50 Hz to 10 kHz being determined by means of the at least one second voltage transformer; determining a calibration factor for the at least one first voltage transformer based at least in part on the determined correction factor; and outputting or causing the output of the determined calibration factor.

2. The method according to claim 1, further comprising: determining a corrected transfer function for the at least one first voltage transformer, wherein the corrected transfer function is determined at least in part based on the determined calibration factor; and outputting or causing the output of the corrected transfer function.

3. The method according to claim 1, wherein the at least one second voltage transformer is temporarily comprised by the power grid.

4. The method according to claim 1, wherein the determining of the first voltage and/or the second voltage of the at least one first voltage transformer is carried out at all three phases of a voltage measuring point existing in the power grid.

5. The method according to claim 1, wherein for all occurring switching states of the power grid and/or operating states of one or more components of the power grid the steps of the method according to one of the claims 1 to 4 are carried out.

6. The method according to claim 3, wherein the at least one second voltage transformer is temporarily arranged in or comprised by the power grid for a measuring period of approximately one day to 6 months.

7. (canceled)

8. The method according to claim 1, wherein the determining of the correction factor is performed for all electrically close inductive voltage transformers.

9. The method according to claim 1, wherein the electrically near at least one first voltage transformer is calibrated for an extended frequency range at least partially based on the respective determined calibration factor, wherein the electrically near at least one first voltage transformer is comprised by the power grid and is at an identical busbar as the at least one second voltage transformer or via a cable directly connected with the at least one second voltage transformer.

10. The method according to claim 1, wherein the at least one second voltage transformer is a capacitive or a measured inductive voltage transformer.

11. The method according to claim 2, wherein the corrected transfer function for the at least one first voltage transformer is re-adjusted at least partially based on the correction factor.

12. The method according to claim 2, wherein the determined correction factor and/or the corrected transfer function are stored in a memory.

13. An apparatus arranged to execute and/or control the method according to claim 1 or comprising respective means for executing and/or controlling the steps of the method.

14. A system comprising one or more apparatuses arranged to execute and/or control the method according to claim 1 or having means to execute and/or control the steps of the method.

15. A computer program comprising program instructions which cause a processor to execute and/or control the method according to claim 1 when the computer program is executed by the processor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0073] In the drawing shows

[0074] FIG. 1 an exemplary system according to an example embodiment;

[0075] FIG. 2 a flow chart of an exemplary method based on an example embodiment;

[0076] FIG. 3 a schematic illustration of an example embodiment of an apparatus which can, for example, execute and/or perform the method according to all exemplary aspects; and

[0077] FIG. 4 different example embodiments of a storage medium.

DESCRIPTION OF THE INVENTION

[0078] FIG. 1 shows an exemplary system 100 of an example embodiment according to the fourth aspect of the present invention. The system 100 comprises in the present case two of first voltage transformers 150, a second voltage transformer 160, a grid unit 191 comprised by a voltage measuring point 190, a server 170 which, for example, executes and/or controls a network control system and/or executes and/or controls a simulation software, a server 110 which, for example, performs and/or controls the present method according to the first aspect of the present invention, an optional database 120, in the present case two WTGs 130 which feed electrical energy into the power grid 140, and a communication network 180 (e.g. the Internet), via which at least server 170 can communicate with server 110. Alternatively, server 170 and server 110 can be directly connected to each other and communicate, for example, via a wired communication connection (e.g. according to the Local Area Network (LAN) standard). Alternatively, the server 110 can be comprised by the server 170 so that a concrete (i.e. tangible) server executes and/or controls e.g. both a network control system of the power grid 140 and the method according to the first aspect of the invention.

[0079] In example embodiments of the present invention, for example, a correction factor is determined, e.g. by the server 110, by first determining a first voltage from one or both of the first voltage transformers 150. Then, for example, the second voltage transformer 160 is temporarily installed in the power grid, e.g. on the same busbar as the other two first voltage transformers 150. Alternatively, the second voltage transformer 160 can replace one of the first two voltage transformers 150 (not shown schematically in FIG. 1).

[0080] The first voltage of the at least one first voltage transformer 150 and a second voltage of the at least one first voltage transformer 150 is determined, for example, by determining the first (frequency-dependent) voltage, e.g. before the second voltage transformer 160 is placed in the power grid 140. The second (frequency-dependent) voltage is determined after the second voltage transformer 160 has been placed in and comprised by the power grid 140. The second voltage of the at least one first voltage transformer 150 is determined at least partially based on a previously known transfer function of the at least one second voltage transformer 160, e.g. corresponds to the correct voltage measured at the at least one first voltage transformer 150.

[0081] After the first and second voltages have been determined, they are transmitted, for example, from the grid unit 191 to the server 110, e.g. via the server 170 connected to the power grid 140 and the communication network 180 (e.g. the Internet). Accordingly, at least the grid unit 191 can establish a communication connection via the communication network 180 to the server 110 and use it for transmitting, for example, the first and second voltage from at least one of the first two voltage transformers 150. The server 110 then determines a correction factor of the at least one first voltage transformer 150 at least partially based on the first and the second determined voltage.

[0082] At least partly based on the determined correction factor, the server 110, for example, determines a calibration factor. This calibration factor for the at least one first voltage transformer 150 can be determined, for example, by making the correct voltage correspond to the voltage determined from the first voltage, the correct voltage and the second voltage, for example according to the following formula:

Calibration factor for the at least one first voltage transformer 150=first voltage*(correct voltage/second voltage),

[0083] where the respective voltages can be determined e in each case depending on the frequency.

[0084] The determined calibration factor is then output, e.g. from the server 110 to the server of the network control system 170, which can use the calibration factor to determine the correct voltage at at least one of the first voltage transformers 150. Based on the correct voltage, the server of the network control system 170 can, for example, quickly and reliably measure any harmonics that may occur or have already occurred in the power grid 140, so that, for example, suitable measures can be taken in good time to eliminate or avoid harmonics in the power grid 140, e.g. by a non-uniform feed of electrical energy into the power grid 140 by the WTG 130.

[0085] FIG. 2 shows a flowchart 200 of an example method according to an example embodiment in accordance with the first aspect of the invention. The flowchart 200 can be performed and/or controlled by the server 110 according to FIG. 1. Alternatively or additionally, the flowchart 200 can be performed and/or controlled by the grid unit 191 according to FIG. 1.

[0086] In a first step 201, a correction factor is determined for at least one first voltage transformer (e.g. one of the voltage transformers 150 according to FIG. 1) arranged in a power grid (e.g. power grid 140 according to FIG. 1).

[0087] The correction factor is indicative of a correction for obtaining correct measured values measured by the at least one first voltage transformer (e.g. one of the voltage transformers 150 according to FIG. 1), wherein the determining of the correction factor of the at least one first voltage transformer is based at least partially on a first voltage of the at least one first voltage transformer and a second voltage of the at least one first voltage transformer, wherein the second voltage of the at least one first voltage transformer is determined at least partially based on a known transfer function of at least one second voltage transformer (e.g. voltage transformer 160 according to FIG. 1) and the first voltage of the at least one first voltage transformer is determined, wherein the correction factor of the at least one first voltage transformer is determined without taking into account the previously known transfer function of the at least one second voltage transformer.

[0088] In a second step 202, a calibration factor for the at least one first voltage transformer (e.g. voltage transformer 150 according to FIG. 1) is determined at least partially based on the determined correction factor.

[0089] In a third step 203 an output or initiation of the output of the determined calibration factor is performed, e.g. from the server 110 according to FIG. 1 to the server of the network control system 170 according to FIG. 1.

[0090] FIG. 3 shows a schematic representation of an example embodiment of an apparatus 300, which can be used in the context of all exemplary aspects. The apparatus 300 represents, for example, the server 110 according to FIG. 1, or the server of the network control system 170 according to FIG. 1, or the grid unit 191 according to FIG. 1, which is comprised by the voltage measuring point of the power grid (power grid 140 according to FIG. 1).

[0091] The apparatus 300 can, for example, execute and/or control the method according to all aspects. For this purpose, the apparatus can, for example, have and/or comprise means for executing and/or controlling the method according to all aspects. Furthermore, the present method according to all aspects can be executed and/or performed by several (i.e. at least two) apparatuses 300.

[0092] The apparatus 300 can, for example, execute the flow chart 200 of FIG. 2.

[0093] The apparatus 300 comprises a processor 310 with assigned main memory 311 and program memory 312, for example, the processor 310 executes program instructions stored in program memory 312. The program instructions execute and/or control the method (e.g. according to steps 201 to 203 of FIG. 2). Thus, program memory 312 comprises a computer program and represents a computer program product for its storage. Apparatus 300 represents an example of an apparatus of a system (e.g. the system 100 according to FIG. 1).

[0094] For example, program memory 312 can be a persistent memory such as read-only memory (ROM). For example, Program Memory 312 can be permanently connected to the processor 310, but alternatively it can also be detachably connected to the processor 310, for example as a memory card, floppy disk, or optical data storage medium (such as a CD or DVD). Additional information can also be stored in program memory 312, or in a separate memory.

[0095] Main memory 311 is used, for example, to store temporary results during the execution of program instructions. This is volatile memory, such as random access memory (RAM).

[0096] The processor 310 is also operatively connected to a communication interface 313, which allows, for example, information exchange with other devices (see e.g. the arrows in FIG. 1). By means of the communication interface 313, for example, a certain calibration information can be output (step 203 of FIG. 2).

[0097] The apparatus 300 can comprise further components. If the apparatus 300 represents the apparatus for executing and/or performing an objective method (e.g. server 110 according to FIG. 1), an optional determining unit (not shown in FIG. 3) is provided, which is set up, for example, to determine a correction factor (step 201 according to FIG. 2) and is operatively connected to the processor 310. Furthermore, a determining unit (not shown in FIG. 3) is optionally provided, which is set up, for example, to determine a calibration factor (step 202 according to FIG. 2) and is operatively connected to the processor 310.

[0098] Optionally, the apparatus 300 may have a user interface (e.g. an input/output device 314) which allows, for example, the displaying of information (e.g. optical reproduction). For example, the user interface is a display device (e.g. a liquid crystal display (LCD), or a light emitting diode (LED) display or similar). In addition, the user interface can be used to record one or more user inputs, e.g. a keyboard, mouse, or touch-sensitive display device.

[0099] FIG. 4 shows different examples of storage media on which an example embodiment of a computer program according to the invention can be stored. The storage medium can be, for example, a magnetic, electrical, optical and/or other type of storage medium. The storage medium may, for example, be part of a processor (e.g. processor 310 of FIG. 3), for example (a non-volatile or volatile) program memory of the processor or a part thereof (such as program memory 312 of FIG. 3). Example embodiments of a storage medium are a flash memory 410, an SSD hard disk 411, a magnetic hard disk 412, a memory card 413, a memory stick 414 (e.g. a USB stick), a CD-ROM or DVD 415, or a floppy disk 416.

[0100] The example embodiments of the present invention described in this specification and the optional features and properties mentioned in each case should also be understood as disclosed in all combinations. In particular, unless explicitly stated otherwise, the description of a feature included in an example embodiment shall not be understood in the present case to mean that the feature is indispensable or essential for the function of the example. The sequence of the method steps described in this specification in the individual flowcharts is not mandatory; alternative sequences of method steps are conceivable. The method steps can be implemented in various ways, for example, implementation in software (through program instructions), hardware or a combination of both to implement the method steps is conceivable.

[0101] Terms used in the claims such as comprise, have, include, contain and the like do not exclude further elements or steps. The expression at least partially covers both the partially case and the completely case. The wording and/or should be understood to mean that both the alternative and the combination should be disclosed, i.e. A and/or B means (A) or (B) or (A and B). The use of the indefinite subject-matter does not exclude a plural. A single apparatus may perform the functions of several units or apparatuses mentioned in the claims. Reference signs indicated in the claims are not to be regarded as limitations of the means and steps used.