NZ601881B - Phase identification system and method - Google Patents
Phase identification system and method Download PDFInfo
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- NZ601881B NZ601881B NZ601881A NZ60188112A NZ601881B NZ 601881 B NZ601881 B NZ 601881B NZ 601881 A NZ601881 A NZ 601881A NZ 60188112 A NZ60188112 A NZ 60188112A NZ 601881 B NZ601881 B NZ 601881B
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- Prior art keywords
- phase
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- voltage signal
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- 230000001131 transforming Effects 0.000 claims abstract description 25
- 238000001514 detection method Methods 0.000 claims abstract description 18
- 238000004364 calculation method Methods 0.000 claims description 5
- 238000002347 injection Methods 0.000 claims 1
- 239000007924 injection Substances 0.000 claims 1
- 230000005611 electricity Effects 0.000 abstract 1
- 238000004891 communication Methods 0.000 description 14
- 230000005540 biological transmission Effects 0.000 description 12
- 238000010586 diagram Methods 0.000 description 10
- 239000011159 matrix material Substances 0.000 description 9
- 238000006243 chemical reaction Methods 0.000 description 7
- 241001646071 Prioneris Species 0.000 description 6
- 230000001808 coupling Effects 0.000 description 4
- 238000010168 coupling process Methods 0.000 description 4
- 238000005859 coupling reaction Methods 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- 238000004804 winding Methods 0.000 description 4
- 230000003111 delayed Effects 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000006011 modification reaction Methods 0.000 description 2
- 230000002104 routine Effects 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 229940035295 Ting Drugs 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000003139 buffering Effects 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 238000004590 computer program Methods 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 230000003203 everyday Effects 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 238000002372 labelling Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
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- 238000005070 sampling Methods 0.000 description 1
- 230000001429 stepping Effects 0.000 description 1
- 230000001360 synchronised Effects 0.000 description 1
- 230000001702 transmitter Effects 0.000 description 1
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/02—Measuring effective values, i.e. root-mean-square values
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
- G01R29/18—Indicating phase sequence; Indicating synchronism
Abstract
Patent 601881 Disclosed is a phase identification system (70) for an electricity distribution network. The system (70) includes a power distribution station (12) having a phase distortion device (72). The phase distortion device (72) generates voltage distortions of a known harmonic frequency in at least one of three phase voltage signals of the power distribution station (12). The system also includes a phase detection device (22) configured to receive at least one of distorted three phase voltage signals and to identify a phase of the received voltage signal. The phase detection device (22) is comprised of a delay circuit, a transformation module and a phase determination module. The delay circuit generates a phase-shifted voltage signal of the received voltage signal. The transformation module transforms the received voltage signal and the phase-shifted voltage signal into d-q domain voltage signals of a known harmonic frequency reference frame. The phase determination module determines the phase of the received voltage signal by comparing an amplitude of a harmonic of the known harmonic frequency in the received voltage signal with a threshold value. at least one of three phase voltage signals of the power distribution station (12). The system also includes a phase detection device (22) configured to receive at least one of distorted three phase voltage signals and to identify a phase of the received voltage signal. The phase detection device (22) is comprised of a delay circuit, a transformation module and a phase determination module. The delay circuit generates a phase-shifted voltage signal of the received voltage signal. The transformation module transforms the received voltage signal and the phase-shifted voltage signal into d-q domain voltage signals of a known harmonic frequency reference frame. The phase determination module determines the phase of the received voltage signal by comparing an amplitude of a harmonic of the known harmonic frequency in the received voltage signal with a threshold value.
Description
Patent Form No. 5
NEW ZEALAND
Patents Act 1953
COMPLETE SPECIFICATION
TITLE: PHASE IDENTIFICATION SYSTEM AND METHOD
We General Electric Company of 1 River Road, Schenectady, New York, 12345, United States of
America, do hereby declare the invention, for which we pray that a patent may be granted to us, and
the method by which it is to be performed, to be particularly described in and by the ing
statement:
4003q
PHASE IDENTIFICATION SYSTEM AND METHOD
This application claims priority from United States Application No. 13/217,370
filed on 25 August 2011, the contents of which are to be taken as incorporated herein by this
reference.
BACKGROUND
The present invention relates generally to the field of three-phase power distribution
networks. More specifically, the invention relates to a system and method of identifying the
phase of a power line in a three-phase power distribution network.
Modern power distribution systems often deliver three phase voltage to users. That
is, a power line may, for example, include a plurality of conductors each designated as a
specific phase of voltage. Moreover, the power distribution system may be set up to e
such that the loads of the power line are balanced (e.g., the amount of power drawn from each
phase output of, for example, a three-phase transformer, is equal). r, over time, users
may be added and removed from the network, which may result in an imbalance in the phase
currents and voltage flow. That is, too many users may be connected to one phase of voltage
while too few are connected to a second and/or third phase. This may result in a non-optimal
utilization of the existing infrastructure. One manner of overcoming this load nce may
be to institute a rebalancing of the loads, for example, by moving customers from a more
highly used phase of voltage to a lesser used phase of voltage.
r, challenges exist in moving ers from one phase of voltage to
r. For instance, as customers are added to and subtracted from a power bution
network, the phase of voltage that a given er is connected to may be difficult to
ascertain without costly physical tracking (typically by a worker in the field) of a given power
line to the network. That is, while a load imbalance may be detected ly, the phase to
which the individual users are connected to may not be readily apparent without physically
tracking the power lines from a substation to the tive user locations. Accordingly, it
would be advantageous to ascertain the phase of voltage to which a user is connected to
without sending a person to one or more user sites to physically determine the voltage phase
being received at the various sites. Further, identifying correct phase of the loads enables
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entiation n single phase and three phase faults and in turn enables the accuracy of
outage management systems that rely on the phase information.
One of the methods of identifying phase is by using modems and telephone lines to
establish a communication link. A signal associated with the phase at a point in the network
where the phase of the line is known (the reference line) is transmitted over the
communication link to a point in the network where the phase of the line is not known (the
line under test). In another method, radio signals are used instead of modems and telephone
lines for communication. However, both these techniques require ation procedures and
special training to be used effectively. An additional method of ing the phase is by
means of precise time stamped measurements (usually using GPS) at the substation where the
phase is known and at the remote location where phase is unknown. By estimating the phase
difference between the two signals, the phase at the remote location can be ined.
However, this method needs y ications or information at two different
locations to identify the phase.
Accordingly, there is a need to provide an improved apparatus and method for the
identification of line phase of a power line in a power distribution network.
A nce herein to a patent document or other matter which is given as prior art is
not to be taken as an admission that that document or matter was known or that the
information it contains was part of the common general knowledge as at the priority date of
any of the claims.
BRIEF DESCRIPTION
In accordance with an aspect of the present invention, there is provided a phase
identification system, comprising: a power distribution station including a phase distortion
device to te voltage distortions of a known harmonic frequency in at least one of three
phase e signals of the power distribution station; and a phase detection device
configured to receive at least one of distorted three phase voltage signals and to identify a
phase of the received voltage signal, the phase detection device comprising: a delay circuit for
generating a phase shifted voltage signal of the received voltage signal; a transformation
module for transforming the ed voltage signal and the phase shifted voltage signal into
d-q domain voltage signals of a known harmonic frequency reference frame; and a phase
determination module for determining the phase of the ed voltage signal by comparing
an amplitude of a harmonic of the known ic frequency in the received voltage signal
with a threshold value.
In ance with another aspect of the present invention, there is provided a method
of identifying phase comprising: ting at least one of three phase voltage signals of a
power distribution system with a known harmonic frequency signal; receiving at least one of
distorted three phase voltage signals from a power distribution system; generating a phase
shifted e signal of the received voltage signal by time delaying the received voltage
signal; transforming the received voltage signal and the phase shifted voltage signal into d-q
domain voltage signals of a known harmonic frequency reference frame; and determining the
phase of the received e signal by ing an amplitude of a harmonic of the known
harmonic frequency in the received voltage signal with a threshold value.
DRAWINGS
These and other features, aspects, and advantages of the present invention will
become better understood when the ing detailed description is read with reference to the
accompanying drawings in which like characters represent like parts throughout the drawings,
wherein:
is a block diagram of a power grid, in accordance with an embodiment of the
present invention;
is a block diagram of a meter of the power grid of in accordance with
an embodiment of the present invention;
is a block diagram of a power distribution n of the power grid with a
phase distortion , in accordance with an embodiment of the present invention;
is a schematic of the phase distortion device of in accordance with an
embodiment of the present invention;
[0014] is a block diagram of a ter controller in accordance with an
embodiment of the present invention; and
is a block diagram of a phase detection device
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DETAILED DESCRIPTION
When introducing elements of various embodiments of the present invention, the
articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the
elements. The terms ising,” “including,” and “having” are intended to be inclusive and
mean that there may be additional elements other than the listed elements.
As used herein, the term “module” refers to software, re, or firmware, or any
combination of these, or any system, process, or functionality that performs or facilitates the
processes described herein.
illustrates a block diagram of power grid 10. The power grid 10 transmits
power from a power bution station 12 to power distribution network 16 via, for example,
one or more power lines 14. The power bution station 12 may, for example, include a
power plant including one or more power generators that may generate voltage for
transmission on the power grid 10. Additionally, or alternatively, the power distribution
station may include one or more power substations that may include one or more transformers
that operate to transform voltage from one voltage to another (e.g., step-down received
voltages from, for example, 100,000 volts to less than 10,000 volts) and/or one or more
distribution busses for further g the power. .
In one embodiment, the power lines 14 may include a plurality of transmission
paths for transmission of power from the power distribution station 12 to the power
distribution k 16. For e, the power lines 14 may transmit e in three
, e.g. phases A, B and C. Additionally, the power lines 14 may include a neutral line in
on to the paths for transmission of the three phases of voltage.
The power distribution network 16 may bute the three phase voltage to a
plurality of users. The distribution network 16 may include, for example, one or more taps 18.
The one or more taps may operate to split off one or more of the power line 14 to, for
example, a side street on which one or more users reside. The tap 18 may thus operate to split
one or more of the voltage phases A, B and C (“A-C”) to the users on this side street. The
power distribution network 16 may also include user lines 20. The user lines 20 may operate
as direct connections to the power lines 14. In one embodiment, each user line 20 may include
a ormer for stepping down the voltage from one level to another. The two voltage levels
may be 7200 volts and 240 volts, for example. Additionally, it should be noted that each of
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the user lines 20 may be connected to a single phase of voltage. That is, each user line 20 may
be connected to phase A, phase B, or phase C voltage. The 240 volt phase A, phase B, or
phase C e may be transmitted to a user with meters 22A-22G connected in the circuit.
Each of the meters 22A, 22B, 22C, 22D, 22E, 22F and 22G (“22A-22G”) may
operate to monitor the amount of energy being transmitted to and consumed by a particular
user. In one embodiment, one or more of the meters 22A-22G may be a portion of an
advanced metering tructure (AMI) such that the meters 22A-22G may measure and
record usage data in specified amounts over predetermined time periods (such as by the
minute or by the hour), as well as transmit the measured and recorded information to the
power distribution station 12. In another embodiment, the meters 22A-22G may allow for
transmission of onal information, such as power s, voltage phase information, or
other infrastructure information, to be sent to the power distribution station 12 for assessment.
illustrates a block diagram of a meter 22, which may be entative of any
of the meters 22A-22G. As illustrated, the meter 22 may include a sensor 24, signal
conversion circuitry 26, one or more processors 28, storage 30, and communication circuitry
32. In conjunction, the sensor 24, the signal conversion circuitry 26, one or more processors
28, the storage 30, and the communication circuitry 32 allow the meter 22 to determine and
transmit a signal indicative of the phase of voltage being received at the meter 22. In this
, the meter 22 may operate as a phase detection . Meter 22, in one embodiment,
is physically attached at the location where the power is being used. Additionally or
alternatively, the phase detection device may se a hand-held metering , and the
determination and/or transmission of a signal indicative of the phase of voltage being ed
may be performed by the hand-held metering device. In one embodiment, the sensor 24 may
include electrical components for receiving and measuring the current and voltage from the
user line 20. As noted above, this voltage may be in one of three phases, phase A, phase B, or
phase C, each 120 s out of phase with one another. The sensor 24 may transmit the
detected voltage and/or current as a signal to the signal conversion circuitry 26. Additionally,
the sensor 24 may detect distortions in voltage signals at the meter 22. As will be sed in
greater detail below, the tions in voltage signals may be used to obtain a determination of
the received phase of voltage at the meter 22.
The signal conversion circuitry 26 may include, for example, voltage conversion
circuitry to convert the voltage of the signal received from the sensor 24 from 240 volts to
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approximately 5 volts, for example. onally, the voltage conversion circuitry may, for
e, include at least one analog to digital converter for transforming signals received
from the sensor 24 (such as voltage signals or injected signals) from analog form into digital
s for processing by one or more processors 28.
[0024] The one or more processors 28 e at least part of the processing capability for
the meter 22. The one or more processors 28 may include one or more microprocessors, such
as one or more “general-purpose” microprocessors, one or more special-purpose
microprocessors and/or ASICS, or some combination of such processing components.
Additionally, programs or instructions executed by the one or more processors 28 may be
stored in any suitable media that includes one or more tangible, computer-readable media at
least tively storing the executed instructions or routines, such as, but not d to, the
storage device described below. As such, the meter 22 may include programs encoded on a
computer program product (such as storage 30), which may include instructions that may be
executed by the one or more processors 28 to enable the meter 22 to provide various
functionalities, ing determining the phase of voltage received at the meter 22 based on,
for example, distortions in the voltage signal.
The instructions and/or data to be processed by the one or more processors 28 may
be stored in a computer-readable medium, such as storage 30. The storage 30 may include a
volatile memory, such as random access memory (RAM), and/or a non-volatile , such
as read-only memory (ROM). In one embodiment, the e 30 may store firmware for the
meter 22 (such as various programs, applications, or routines that may be executed on the
meter 22). In addition, the storage 30 may be used for buffering or caching during operation
of the meter 22. The storage 30 may include, for example, flash memory, a hard drive, or any
other optical, magnetic, and/or solid-state storage media. The storage 30 may also be used to
store information for eventual transmission via communication circuitry 32. The ation
stored may include the phase information that can be used later for example during meter
reading by the utility.
Communication circuitry 32 may be utilized to transmit information from the meter
22 to, for e, the power distribution station 12 (. The information may, for
example, include one or more signals indicating the phase of voltage being received at the
meter 22, the voltage usage at the meter 22, and/or other information relating to the operation
of the meter 22. Accordingly, the communication try 32 may include, for example, a
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transceiver for itting and receiving information with the power distribution station 12
and/or other meters (e.g., G). The communication circuitry 32 may, instead, include a
transmitter, which may allow for transmission of information to, for example, the power
distribution station 12 and/or other meters, but will not receive information. The
communication circuitry 32 may further include wireless transmission and/or eiver
ts for wireless transmission and/or reception of information. Additionally and/or
alternatively, the communication circuitry 32 may be physically coupled to the power
distribution station 12 through a wired communication mode, power line carrier
communication (PLC) circuitry, for example. Regardless of the transmission medium,
through the use of ication circuitry 32, the meter 22 may be able to it collected
information including the phase of voltage being received at the meter 22.
is a block diagram 70 of a power distribution station 12 with a phase
distortion device 72 that may be utilized in conjunction with the meters 22 to determine the
phase of voltage being supplied to a given user. The power distribution station 12 may operate
to transmit three phase voltage across power lines 14, such that phase A voltage may be
transmitted across line 36, phase B voltage may be transmitted across line 38, and phase C
voltage may be transmitted across line 40. It should be noted that the phase line labeling of
phase A, phase B, and phase C for lines 36, 38, and 40 is only for purposes of e. In one
embodiment, the phase distortion device 72 includes a shunt current circuitry which is
configured to draw a harmonic t from any one of the phases and to distort the phase
e signals at the load point on a distribution network 16. When the harmonic current is
drawn from a phase, it s in harmonic voltage drop across the transmission line resulting
in distortions on power line voltage signal of that phase. It should be noted that even though
only one phase tion device 72 is shown in in some embodiments each of the
phases will have a separate phase distortion device 72 (i.e., 3 phase distortion devices for 3
phases).
The power line voltage signals may be distorted either on command or on a
schedule. For example, a utility may initiate a tion in response to the amount of
unbalance seen in the network. Additionally or alternatively, the distortion may be set to
occur at a constant frequency of occurrence such as, for e at a particular time every
day. The distorted phase voltage on a particular phase or a power line is then transmitted over
that particular power line, for e, 36, 38, or 40 and reach meter 22 in power distribution
network 16, and meter 22 identifies the distortion and hence the phase depending on a
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characteristic of the distortion received. In one embodiment, the meter 22 may also transmit
the identified phase information to the power distribution station 12 (.
is a schematic of the phase distortion device 72 of in accordance with
an embodiment of the present invention. The phase tion device is configured to draw
harmonic currents from a power line 74 and includes a coupling transformer 80, a single phase
DC to AC converter 82 and a pulse width modulation (PWM) generator 84 for providing
ing signals to single phase DC to AC converter 82. The coupling transformer 80
matches the voltage of the power line with the output of the single phase DC to AC ter
82 and also provides isolation between the power line and the single phase DC to AC
converter 82 The single phase DC to AC converter 82 includes a DC link 86 and
semiconductor switches 88. A primary winding 76 of coupling transformer 80 is shunt
ted to the power line 74 (i.e., primary g 76 is connected between power line 74
and a ground connection 75). A ary winding 87 of coupling transformer 80 is
connected across the output of single phase DC to AC ter 82. PWM generator 84
provides switching signals to single phase DC to AC converter 82 based on a reference voltage
signal Vref generated by a converter controller 100. The reference voltage is determined
based on the amount of active power the single phase DC to AC converter 82 requires and also
the harmonic current requirement for voltage distortion. The active power required by the
single phase DC to AC converter 82 is utilized for supporting losses of the converter and also
for maintaining voltage of the DC link 86.
In one embodiment, three different harmonic frequencies may be drawn from three
ent phases and the ing voltage distortion may be analyzed by the meter 22 at a load
point (not shown). The analysis of the voltage distortion can then determine the phase of the
power line to which the load is connected. There may be multiple methods to analyze the
e distortion, one of which will be described in the succeeding paragraphs.
is a block diagram of a converter controller 100 in accordance with an
embodiment of the present invention. Converter controller 100 generates reference voltage for
DC to AC converter 82 of based on a ed ic current to be drawn from the
power line. Converter controller 100 receives a current ic, a line voltage vc and DC link
voltage Vdc as inputs and provides reference voltage signal Vref as output. t ic is an
actual current drawn by DC to AC converter 82 from the power line 74 whereas voltage vc is a
voltage of the power line 74. Reference signals iref and Vdcref are determined by a system
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operator. The reference current iref is a harmonic current (e.g., 8th, 9th, 10th, etc.) that needs to
be drawn from the power line whereas the reference e Vdcref is the DC link voltage that
needs to be maintained for DC to AC converter 82. The reference current iref is phase shifted
by 90 degrees by a first phase shifter module 102 and then the reference current and the phase
shifted current are converted into d-q components idref and iqref by a first - to d-q domain
transformation module 104. As will be appreciated by those skilled in the art, the - to d-q
domain ormation module 104 may include a transformation matrix that transforms the
voltage signals from one reference frame to another reference frame based on an input phase
signal. In one embodiment, the transformation matrix may be given as:
cos t sin t
(1)
sin t cos t
where is a frequency in radians/second and t is time in seconds.
The first - to d-q domain transformation module 104 receives a saw tooth wave
signal as the phase signal from the saw tooth wave generator module 106 to convert the
reference currents into d-q reference currents idref and iqref. The saw tooth wave signal is
synchronized with the reference current signal and its frequency is the same as that of the
reference current signal i.e., the harmonic ncy.
The actual current ic drawn by DC to AC converter 82 is also converted into
measured d-q domain currents icd and icq by a second phase shifter module 108 and a second
- to d-q domain ormation means or matrix 110. Error signals iderror and iqerror
representing a difference between d-q domain reference currents idref and iqref and measured dq
domain currents and icd and icq are then fed to two proportional-integral (PI) controllers 112,
114 to te d-q domain reference voltage signals vdref and vqref. PI controllers 112, 114
basically generate appropriate voltage signals that should be generated by DC to AC converter
82 to compensate for differences between actual t and reference current. A d-q to -
domain transformation module 116 then generates a first or harmonic portion varef of a
reference voltage vref for drawing the reference current or the harmonic current iref from the
power line. The d-q to -domain transformation module includes an e transformation
matrix that may be equal to inverse of transformation matrix in equation 1.
A second or fundamental n vbref of the nce voltage vref is generated by a
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DC link voltage loop 118 which controls active power flow between the DC to AC converter
82 and the power line. The voltage loop 118 converts an error Vdcerror between a reference DC
link voltage Vdcref and the actual DC link voltage Vdc into a phase angle through a third PI
controller 120. The phase angle represents a delay angle by which a sine wave generated by
a sine wave module 124 should lag with respect to the line voltage vc so that a desired amount
of active power will be drawn to maintain the DC link voltage Vdc equal to the nce DC
link voltage . A theta generation module 122 determines a pha se of the line voltage vc
and the sine module 124 es the phase angles and to generate an appropriate sine
waveform representing the second n vbref of the reference voltage vref. The on of
the varef and the vbref then generates the reference voltage vref for the DC to AC converter 82.
is a block diagram of a phase detection device 140 which determines a phase
of the power line at the user end based on the distorted voltage in accordance with an
embodiment of the present invention. For example, when three different currents of three
different harmonic frequencies are drawn from three power lines it results into voltage
tions. The phase detection device 140 in each of the power line will then compute
amplitude of a particular harmonic voltage in the power line and determine the phase (i.e.,
phase A, phase B, or phase C) of the received voltage or the power line if the computed
amplitude is greater than a respective threshold value. The phase detection device 140 is
utilized in meter 22 of and can determine the phase of the power line irrespective of the
method of voltage distortion. Thus, the method of voltage distortion may include injecting
series harmonic voltages into the power line or drawing harmonic currents from a power line
as described earlier.
The phase detection device 140 es a domain transformation module 142
which converts an input signal V and a delayed input signal V into d-q domain s Vd
and Vq. The delayed input signal V is generated by a delay module 144. In one embodiment,
the delay module delays the input signal V by a delay angle equal to a 1/4th or 90 degrees of a
harmonic frequency i.e., 6 seconds for a frequency of 600 Hz. It should be noted that
the delay angle value 90 s is merely for representative purpose and in a discrete
embodiment the delay angle value may depend on a sampling frequency of the phase detection
device 140 and may be different than 90 degrees. The domain transformation matrix utilizes a
saw tooth wave signal representing the harmonic frequency from a harmonic angle generation
module 146 to generate d-q domain signals Vd and Vq. The harmonic frequency is equal to the
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frequency of one of the three harmonic ts drawn from three power lines. Thus, the
frequency of the saw tooth wave signal may be changed 2-3 times to detect which phase, the
power line belongs to. For example, the harmonic frequencies of injected voltages in each of
the phases are known and are stored in the phase ion device. When in one of the power
lines the amplitude of the particular harmonic voltage signal exceeds a threshold value then it
indicates presence of that harmonic distortion and then based on the harmonic frequency
information stored in the phase detection device, the phase of the power line can be easily
identified.
The d-q domain voltage signals Vd and Vq from domain transformation matrix 142
are then passed through low pass filters 148, 150 to eliminate any fundamental or higher
harmonic signals and to generate d-q domain harmonic signals Vdf and Vqf. As will be
appreciated by those skilled in the art the low pass filters 148, 150 may be implemented in an
analog domain or a digital . In one embodiment, a transfer function G(s) of the low
pass filter may be given as:
G(s) (1)
1 a1(s /c ) a 2
2 (s /c )
where K, a1 and a2 are nts and c is the cut off frequency of the low pass filter. In one
embodiment, the cut off frequency c of the low pass filter is lower than the fundamental
frequency and may be determined such that the output signal is substantially a constant value.
The amplitude of the harmonic voltage signal is then determined by an amplitude calculation
module 152 which identifies square root of ion of square values of d-q domain
harmonic signals and In one embodiment, to reduce computation complexity of the
amplitude calculation module 152, absolute values of d-q domain ic signals and
are first identified and then the absolute values are added to obtain the amplitude of the
harmonic signal.
[0038] In one embodiment, phase determination module 154 compares the amplitude of the
harmonic signal with a threshold value. If the amplitude exceeds the threshold value then the
phase determination module 154 fies that a harmonic current has been drawn from that
phase. For each of the power lines, harmonic ts of different frequencies are drawn from
the lines. In one embodiment, the ncies for each of the phases are fixed and are also
stored in the phase determination module 154. So when phase determination module 154 of
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that phase detects presence of the respective harmonic signal it identifies the phase of that
power line. Other ways of determining phase may include comparing the time for which the
amplitude of the harmonic signal exceeds the threshold value or comparing the number of
instances for which the amplitude of the harmonic signal exceeds the threshold value.
[0039] While only certain features of the invention have been illustrated and described
herein, many modifications and s will occur to those skilled in the art. It is, ore,
to be understood that the appended claims are intended to cover all such modifications and
changes as fall within the true spirit of the invention.
Where the terms “comprise”, ises”, “comprised” or ising” are used in
this specification (including the claims) they are to be interpreted as specifying the presence of
the stated features, integers, steps or ents, but not precluding the presence of one or
more other features, integers, steps or components, or group thereto.
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PARTS LIST
Power Grid
12 Power Distribution Station
14 Power Lines
16 Power Distribution Network
18 Power Line Taps
User Lines
22A-22G Meters
24 Sensor
26 Signal Conversion Circuitry
28 Processors
Storage
32 Communication Circuitry
36, 38, 40 Power Lines
70 Power Distribution Station with a Phase tion Device and Meters
72 Phase Distortion Device
74 Power Line
75 Ground Connection
76 Primary Winding
80 ng Transformer
82 Single Phase DC to AC Converter
C:\pof\word\SPEC-NZ18362-12.docx
84 Pulse Width tion (PWM) Generator
86 DC Link
87 Secondary Winding
88 Semiconductor Switches
100 Converter Controller
102 First Phase Shifter Module
104 - to d-q Domain Transformation Module
106 Saw Tooth Wave Generator Module
108 Phase Shifter Module
110 - to d-q Domain Transformation Means or Matrix
112, 114 tional-Integral (PI) Controllers
116 d-q to -Domain Transformation Matrix
118 DC Link Voltage Loop
120 PI Controller
124 Sine Wave Module
140 Phase Detection Device
142 Domain Transformation Module
144 Delay Module
146 Harmonic Angle Generation Module
C:\pof\word\SPEC-NZ18362-12.docx
148, 150 Low Pass Filters
152 Amplitude Calculation Module
154 Phase ination Module
C:\pof\word\SPEC-NZ18362-12.docx
Claims (12)
1. A phase identification system, comprising: a power distribution station ing a phase distortion device to generate voltage distortions of a known harmonic frequency in at least one of three phase voltage signals of the power distribution station; and a phase detection device ured to receive at least one of ted three phase voltage signals and to identify a phase of the received voltage , the phase detection device comprising: a delay circuit for generating a phase shifted e signal of the received voltage signal; a transformation module for orming the received voltage signal and the phase shifted voltage signal into d-q domain voltage signals of a known ic frequency reference frame; and a phase determination module for determining the phase of the received voltage signal by comparing an amplitude of a harmonic of the known harmonic frequency in the received voltage signal with a threshold value.
2. The phase fication system of claim 1, wherein the known harmonic frequency is different for different phase voltage signals.
3. The phase identification system of claim 2, wherein the threshold value is different for different harmonic frequencies.
4. The phase identification system of any one of claims 1 to 3, wherein the phase distortion devices comprises a voltage distortion t.
5. The phase identification system of claim 4, wherein the voltage distortion circuitry comprises a series voltage injection circuit for injecting harmonic es into a power of the power bution station.
6. The phase identification system of claim 4, wherein the voltage distortion circuitry comprises a shunt current circuitry for drawing harmonic currents from a power line of the power distribution station.
7. The phase identification system of claim 6, wherein the shunt current circuitry ses a single phase DC to AC converter for drawing a reference harmonic current from the power line of the power distribution station.
8. The phase identification system of any one of claims 1 to 7, further comprising an amplitude calculation module to calculate the amplitude of the ic of the known harmonic frequency in the received voltage signal by obtaining a square root of square values of d-q domain voltage signals.
9. The phase identification system of claim 1, further comprising an ude calculation module to calculate the amplitude of the harmonic of the known harmonic frequency in the received voltage signal by adding te values of d-q domain voltage signals.
10. A method of identifying phase comprising: distorting at least one of three phase voltage signals of a power distribution system with a known harmonic frequency signal; receiving at least one of distorted three phase e signals from a power distribution system; generating a phase shifted voltage signal of the received voltage signal by time delaying the received voltage signal; transforming the received voltage signal and the phase shifted voltage signal into dq domain voltage s of a known harmonic frequency reference frame; and determining the phase of the ed e signal by comparing an amplitude of a harmonic of the known harmonic frequency in the received voltage signal with a threshold value.
11. A phase identification system ntially as hereinbefore described with reference to any one of the embodiments shown in the drawings.
12. A method of identifying phase ntially as hereinbefore described with reference to any one of the embodiments shown in the drawings.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US13/217,370 US8810233B2 (en) | 2011-08-25 | 2011-08-25 | Phase identification system and method |
US13/217,370 | 2011-08-25 |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ601881A NZ601881A (en) | 2014-02-28 |
NZ601881B true NZ601881B (en) | 2014-06-04 |
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