U.S. patent application number 11/072107 was filed with the patent office on 2005-08-11 for circuit component and transformer device with controllable impedance and with systems equipped with such devices.
This patent application is currently assigned to Magtech AS. Invention is credited to Haugs, Espen, Strand, Frank.
Application Number | 20050174127 11/072107 |
Document ID | / |
Family ID | 19913051 |
Filed Date | 2005-08-11 |
United States Patent
Application |
20050174127 |
Kind Code |
A1 |
Haugs, Espen ; et
al. |
August 11, 2005 |
Circuit component and transformer device with controllable
impedance and with systems equipped with such devices
Abstract
The invention relates to a circuit component (L1) with
controllable impedance, comprising a body (1) of a magnetisable
material, a main winding (A1) wound round the body (1) about a
first axis and a control winding (A2) wound round the body (1)
about a second axis, at right angles to the first axis, where the
main winding (A1) is arranged for connection to a working circuit
in which the circuit component (L1) is to be employed and the
control winding (A2) is arranged for connection to a control unit
for controlling the impedance in the working circuit. The invention
also relates to various current and voltage regulating devices
comprising the circuit component or a similar transformer
device.
Inventors: |
Haugs, Espen; (Sperrebotn,
NO) ; Strand, Frank; (Moss, NO) |
Correspondence
Address: |
KIRKPATRICK & LOCKHART NICHOLSON GRAHAM LLP
(FORMERLY KIRKPATRICK & LOCKHART LLP)
75 STATE STREET
BOSTON
MA
02109-1808
US
|
Assignee: |
Magtech AS
Moss
NO
|
Family ID: |
19913051 |
Appl. No.: |
11/072107 |
Filed: |
March 4, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11072107 |
Mar 4, 2005 |
|
|
|
10299684 |
Nov 20, 2002 |
|
|
|
60332569 |
Nov 26, 2001 |
|
|
|
Current U.S.
Class: |
324/612 |
Current CPC
Class: |
G05F 1/32 20130101; Y02E
40/30 20130101; H01F 29/14 20130101; H02H 9/08 20130101; H02J 3/18
20130101; H02H 9/021 20130101 |
Class at
Publication: |
324/612 |
International
Class: |
G01R 027/28 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 20, 2001 |
NO |
20015690 |
Claims
1-9. (canceled)
10. A system for controlling the impedance of a transmission line,
comprising a measuring unit for measuring parameters concerning the
line's operation a processing unit with at least one input and one
output, where the input is connected to the measuring unit, and in
which processing unit the measurement values are compared with
desired operating values for the line in order to derive an output
signal constituting a control current signal, and a circuit
component with controllable impedance with a main winding for
connection to the transmission line and a control winding for
connection to the processing unit, with the result that the control
current signal is fed to the control winding from the processing
unit, thereby controlling the processing unit component's impedance
and the line's operation on the basis of the ratio between the
measurement results and the desired values.
11. A system according to claim 10, where the desired values for
the line are input manually by an operator.
12. A system according to claim 10, where the main winding is
arranged for connection in series with the transmission line and
the system further comprises a capacitor or a capacitor battery
connected in parallel with the circuit component's main winding for
series compensation of the transmission line.
13. A system according to claim 10, where the main winding is
arranged for connection in parallel with the transmission line and
the system further comprises a capacitor or a capacitor battery
connected in series with the circuit component's main winding for
shunt compensation of the transmission line.
14. A system for earth fault compensation, i.e. for regulating
earth fault impedance comprising a measuring unit for measuring
earth fault back current together with other parameters for an
electrical component, a processing unit with at least one input and
one output, where the input is connected to the measuring unit and
in which processing unit the measurement values are compared with
desired values for earth fault back current values in order to
derive an output signal constituting a control current signal, and
a circuit component with controllable impedance with a main winding
for connecting between the component and earth and a control
winding for connecting to the processing unit, with the result that
the control current signal is fed to the control winding from the
processing unit, thereby controlling the processing unit
component's impedance and earth fault current on the basis of the
ratio between the measurement results and the desired values.
15. A filter system for reducing harmonic currents, phase asymmetry
and flicker as well as for reactive compensation of an electrical
device, where the system comprises a measuring unit for measuring
parameters-concerning the device's operation, a processing unit
with at least one input and one output, where the input is
connected to the measuring unit, and in which processing unit the
measurement values are compared with desired operating values for
the component in order to derive an output signal constituting a
control current signal, and a filter connected to the component,
where the filter comprises a circuit component with controllable
impedance with a main winding for connection to the filter circuit
and a control winding for connection to the processing unit, with
the result that the control current signal is fed to the control
winding from the processing unit, thus controlling the processing
unit component's and thereby the filter's impedance and the
device's operation on the basis of the ratio between the
measurement results and the desired values.
16. A switch or current limiting system for an electrical device
such as, e.g. an electric motor, where the system comprises a
measuring unit for measuring parameters concerning the device's
operation, a processing unit with at least one input and one
output, where the input is connected to the measuring unit, and in
which processing unit the measurement values are compared with
desired operating values for the component in order to derive an
output signal constituting a control current signal, and a circuit
component connected between the power supply and the device, where
the circuit component has a controllable impedance with a main
winding for connection between the power supply and the device and
a control winding for connection to the processing unit, with the
result that the control current signal is fed to the control
winding from the processing unit, thereby controlling the
processing unit component's impedance and thereby the off/on
position of the switch substantially steplessly and thereby the
device's operation on the basis of the ratio between the
measurement results and the desired values.
17. A system according to claim 11, where the main winding is
arranged for connection in series with the transmission line and
the system further comprises a capacitor or a capacitor battery
connected in parallel with the circuit component's main winding for
series compensation of the transmission line
18. A system according to claim 11, where the main winding is
arranged for connection in parallel with the transmission line and
the system further comprises a capacitor or a capacitor battery
connected in series with the circuit component's main winding for
shunt compensation of the transmission line.
Description
[0001] The invention relates to a circuit component with a
controllable impedance of the type described in
PCT/NO001/00217.
[0002] In the said patent application a circuit component is
described comprising a body of magnetisable material, a main
winding that is wound round the body about a first axis and a
control winding that is wound round the body about a second axis.
By altering the current in the control winding it will be possible
to change the circuit component's reluctance and thereby the
impedance independently of frequency variations in the circuit in
which the main winding is connected.
[0003] The concept according to the invention therefore involves
providing a circuit component with controllable impedance as
indicated in patent claim 1, where the impedance control is
implemented by means of a control current. A major advantage of the
invention is that it does not require movable parts or complicated
circuits for controlling the impedance value.
[0004] The principle behind the invention is illustrated in FIG. 1.
In this figure there is illustrated a body 1 of a magnetisable
material, which may be ferrite or iron or other suitable
magnetisable materials. Around the body 1 is wound a main winding
A1, which will be connected to the circuit at the point where a
variable impedance requires to be introduced. A1 is wound in a
first direction, which in the case illustrated in FIG. 1A coincides
with the body's 1 circumference. A second winding, the control
winding A2, is also wound around the body 1, but the winding axis
is at right angles (perpendicular) to the winding axis for A1,
thereby largely avoiding transformative connection between A1 and
A2, with the only connection taking place within the magnetisable
material. In principle the connection will be manifested as a
change in the material's .mu..sub.r. Based on the known equations:
Rm=1/.mu..sub.r.mu..sub.0A, L=N.sup.2/Rm and X.sub.L=jwL, it can be
seen that a change in .mu..sub.r will lead to a change in L and
thereby in X.sub.L.
[0005] This characteristic of the invention is particularly useful
with regard to regulation, which at the present time is carried out
by means of power electronics.
[0006] A first application of the circuit component according to
the invention is for series compensation in transmission lines
(patent claim 2, FIG. 2). Series compensation is employed in the
case of a power line 12 where connection of various equipment
causes the line's total impedance to have an excessively high
inductive factor. In order to compensate for the inductive factor,
capacitors C1 are inserted. The component according to the
invention L1 will then be connected in series to the line 12 where
the compensation is to be performed (i.e. the main winding A1 in
the component L1 is connected in series to the line 12). At the
same time the component L1 will be connected in parallel to a
capacitor or a capacitor battery C1. By means of the control
winding A2 in L1 it will be possible to control the component's L1
impedance from a very low value (where the current in the line 12
passes through the component L1 and not through the capacitor C1)
to a high value (where the current in the line 12 largely passes
through the capacitor C1). A second application of series
compensation is in order to change the impedance value for a
transmission line and thereby control power flow between several
parallel lines. In the case illustrated in FIG. 1 it will be
possible by means of the component L1 according to the invention to
control the impedance in the line 12 and thereby the load
distribution between the lines 12 and 13. According to the prior
art it is possible by this means to perform load flow regulation
(current limiting or redistribution of power flow) and stability
control.
[0007] According to the prior art a series compensation of this
kind is carried out by means of a thyristor-controlled or
thyristor-connected series capacitor (CSCS, TSSC). A thyristor
group and control devices are therefore required in order to
activate the different thyristors. This is both cumbersome and
expensive.
[0008] The invention also relates to a system for controlling the
impedance of a transmission line according to patent claims 10 and
11, and in a special embodiment a system for series compensation of
transmission lines according to claim 12.
[0009] Such an embodiment of the invention comprises a measuring
unit 2 for measuring parameters concerning the line's operation (U,
I cos .phi., P, Q, S, f), a processing unit with inputs and outputs
where a first input is connected to the measuring unit so that the
results of the measurement are transmitted to the processing unit,
a second input is connected to an input unit for input of desired
values, and at least one output, where the output signal is
converted to a current control signal with a desired frequency
(this current may be direct current or alternating current) and
intensity, and a circuit component with controllable impedance
comprising a main winding for connecting to the transmission line
and a control winding for connecting to the processing unit, with
the result that the processing unit controls the component's
impedance on the basis of the ratio between the measurement results
and the desired values.
[0010] It is also possible to implement the invention as an "open
loop" control circuit where the impedance value is regulated on the
basis of desired values without any feedback for measurement
values.
[0011] A simplified block diagram for the invention is illustrated
in FIG. 3.
[0012] FIG. 3 illustrates a system according to the last-mentioned
embodiment of the invention. As stated, the system comprises a
measuring unit 2 for connecting to a transmission line 12, which
has to be series compensated, and which will measure the line's
operating parameters, such as voltage, current, cos .phi.). The
measured values are transmitted to a processing unit 4, which in an
embodiment of the invention is also fed with desired values. Based
on the input values the processing unit computes a desired value
for the impedance of the component L1 and thereby the necessary
control current value that will be applied to the control winding
A2 in the component.
[0013] Thus the invention constitutes a controllable series reactor
that may be employed in combination with a series battery.
[0014] The invention has great utilitarian value since it will lead
to increased network utilisation (increased load limits) as a
result of the ability to regulate power flow (in normal operation
or after a fault), or as a result of increased stability
limits.
[0015] With regard to the output of the circuit component, the
maximum output may preferably be of the order of 3000 A, with an
impedance of 10-50 ohm.
[0016] Regarding regulation requirements for the system, linear
control of the series inductance will be needed. The regulating
system (which in the described example is provided in the
processing unit 4) should be able to follow power changes with a
frequency of up to 10 Hz if the unit is to be used for stability
control. If it is to be used for compensation of subsynchronous
resonance it will have to be raised to 30-50 Hz.
[0017] As regards protection requirements when using the system,
traditional impedance/distance protection will be replaced by "wave
protection". If a series battery is used, this will result in the
need for metal-oxide diverters (MOD).
[0018] As far as system losses are concerned, the stationary losses
should be small but this is a minor consideration since the
component's total utility value is high. One of the advantages of
the system is that it involves a single component with
exceptionally low operating costs.
[0019] A second application of the circuit component according to
the invention is as a shunt compensator in transmission lines
(patent claim 3), i.e. as a controllable shunt reactor possibly in
combination with a shunt battery. According to the prior art this
kind of shunt compensation is performed by means of
thryistor-controlled reactors (TCR), with all the drawbacks this
entails. This application of the invention is illustrated in FIG.
4.
[0020] According to this embodiment of the invention the shunt
compensation is implemented by means of a circuit component L1 with
a main winding A1, which is connected on one side to a transmission
line 13 and on the other side is connected to a capacitor C1. The
capacitor C1 in turn is connected to earth. The compensation is
carried out by changing the impedance of the circuit component L1
by means of the control winding A2 and thereby changing the total
impedance of the series L1-C1. The total impedance for the series
connection will therefore vary from purely inductive (high value of
impedance for the component L1) to zero (series resonance between
L1 and C1) and thereafter to purely capacitive (low value of
impedance for the circuit component L1). At the same time it will
be possible to perform voltage regulation by means of this device,
where an unacceptably high voltage in the line will be able to be
compensated by increasing the total series impedance for the
component and the capacitor and vice versa for an unacceptably low
voltage.
[0021] Thus in a second embodiment, the system according to the
invention comprises a system for shunt compensation (patent claim
13), with a measuring unit, a processing unit and a controllable
circuit component where the main winding A1 is arranged for
connection in parallel with the transmission line 13, and where the
system further comprises a capacitor or a capacitor battery C1
connected in series with the circuit component's L1 main winding A1
for shunt compensation of the transmission line 13.
[0022] The function of this embodiment of the invention will be
reactive compensation and voltage regulation in the transmission
line.
[0023] It will lead to increased network utilisation (increased
load limits) as a result of better voltage regulation (in normal
operation or after a fault) and reactive reserve, or also as a
result of increased limits with regard to the voltage
stability.
[0024] With regard to output for the shunt reactor, this will be of
the order of 80-150 MV Ar (300 kV, 420 kV). The requirements for
regulation of the processing unit will be similar to those for an
SVC unit (band width 10-20 Hz).
[0025] This system has no special protection requirements, which
means that standard conductors (MOA) can be used.
[0026] As far as losses are concerned, these will correspond to or
be lower than those for ordinary reactors, i.e. reactors that
cannot regulate the impedance with iron core. Control current loss
will come in addition (3%). It is most relevant to compare this
aspect of the invention with a traditional thyristor-controlled
reactor (TCR).
[0027] A third application of the circuit component according to
the invention is for earth fault compensation (patent claim 4). The
prior art in this field comprises the use of a so-called Petersen
coil for limiting earth fault current. A Petersen coil is a reactor
with an iron core and air gap, which is connected between the
network's neutral point and earth. Petersen coils are extremely
expensive, in addition to which they have to be adjusted
mechanically. The Petersen coil has to be regulated at all times to
resonate with the rest of the system to which it is connected.
Impedance changes in the system will therefore lead to the need for
a new, mechanical adjustment of the coil. This is cumbersome and
expensive, and substantially limits the use of such a coil.
[0028] The said application of the invention is illustrated
schematically in FIGS. 5 and 6. FIG. 5 illustrates a three-phase
converter where the primary windings are connected in delta
configuration while the secondary windings are connected in radial
configuration. The circuit component L1 according to the invention
is therefore arranged between the radial configuration's zero point
and earth. By changing the impedance of the circuit component L1 it
will be possible to control the earth fault back or return
current.
[0029] The invention also comprises a system for earth fault
compensation (patent claim 14, FIG. 6), i.e. for regulating earth
fault impedance comprising a measuring unit 2 for measuring earth
fault back or return current together with other parameters for an
electrical component T1, a processing unit 4 with at least one
input and one output, where the input is connected to the measuring
unit 2, and in which processing unit the measurement values are
compared with desired values for earth fault back current values in
order to derive an output signal constituting a control current
signal, and a circuit component L1 with controllable impedance with
a main winding A1 for connecting between the component T1 and earth
and a control winding A2 for connecting to the processing unit 4,
with the result that the control current signal is fed to the
control winding A2 from the processing unit 4, thereby controlling
the processing unit 4 component's L1 impedance and earth fault
current on the basis of the ratio between the measurement results
and the desired values.
[0030] As regards the output of this system, this will preferably
be up to 200 A.
[0031] This embodiment has no special protection requirements, and
the losses will not be important since the voltage across the
circuit component will normally be low.
[0032] A fourth application of the circuit component is as a filter
(patent claim 5), for example as shunt or series compensation with
very rapid regulation.
[0033] This rapid regulation will be achieved by simply providing a
rapid change in the control current.
[0034] According to this embodiment the invention will comprise a
filter (FIG. 7 for band-pass filter, FIG. 8 for high-pass filter)
comprising a shunt or series compensator with a main winding for
connecting to the main circuit and a control winding for connecting
to a control unit. By means of the control current, the circuit
component included in the filter will be able to change the
filter's characteristics as required simply by changing the
characteristics of the control current.
[0035] A filter system according to the invention (patent claim 15)
will comprise a filter with a circuit component as mentioned
earlier together with a measuring and a processing unit for
controlling the component's inductance. The system's function will
be compensation in order to reduce harmonic, phase asymmetry and
flicker in addition to reactive compensation.
[0036] In this application the invention will provide better
voltage quality and increased reliability in HVDC converters.
[0037] As far as the output requirement is concerned, this will
vary depending on where the filter has to be used, but in general
it can be said that as a rule it will be of the order of 50-100
MVAr. The regulation of the system will have to be rapid, viz.
preferably from milliseconds to {fraction (1/10)} of a second.
[0038] The invention will therefore represent an alternative to the
known active filters (power electronics-based), passive filters and
hybrid solutions.
[0039] A fifth application of the circuit component is as a current
limiter (patent claim 16), "generator switch", such as for example
a controlled series reactor for current limiting in connection with
an electrical load device. This embodiment of the invention is
illustrated in FIG. 9. This embodiment is similar on the whole to
that illustrated in FIG. 3, except that the control will be
exclusively conducted on the basis of desired current values. Thus
the invention will also comprise a current limiting system, where
it will be possible to provide a switch by means of the circuit
component according to the invention. The switch will then be able
to move from an open state (i.e. very high impedance) to a closed
state (i.e. impedance equal to zero) steplessly by means of the
control current. By using a current limiter according to the
invention, it will be possible to reduce the current supplied to
the load device to a magnitude that can be handled by a circuit
breaker. In this manner it will be possible to replace power
switches (which are 20 times more expensive than circuit breakers
but which on the other hand are capable of interrupting high
current values) with circuit breakers in combination with current
limiters according to the invention.
[0040] In this case the function of the system will be current
limiting by introducing higher or lower impedance depending on the
requirement.
[0041] With regard to the utilitarian value of this invention, the
most important advantage will be that it will lead to a reduction
in the need for switch equipment.
[0042] In this case the output requirement will be independent
according to the purpose for which it is used.
[0043] As regards regulation requirements, it will not be necessary
to have a closed loop for regulation.
[0044] The losses in normal "on mode" will be approximately 0
loss.
[0045] The invention will represent an alternative to an Is
limiter.
[0046] We shall now present possible concrete applications of the
invention.
[0047] Series Reactor Flesaker-Tegneby
[0048] With regard to possible applications in the Norwegian main
network, the use as a series reactor may be cited as an example.
Limits for transmission capacity from west to east in Southern
Norway will often be determined by the capacity of 300 kV
Flesaker-Tegneby. The reason for this is that when central lines in
Eastern Norway drop out, this will lead to an increased load on the
line/cable between Flesaker and Tegneby. A controllable series
reactor will offer the possibility of reducing the power flow on
this connection in a fault situation, thereby permitting an
increase in the operative load limits in the Flesaker section.
[0049] Traction Power Supply
[0050] Power fluctuations are an increasing problem for the
traction power supply in Norway and in other countries employing
rotating converters. The converter sets in Norway consist mainly of
mechanically connected synchronous motor-synchronous generator sets
that supply the traction power network with single-phase
alternating voltage of approximately 15 kV and frequency equal to
162/3 Hz. Stability problems associated with the converter sets are
experienced more and more frequently as a result of the fact that
the locomotives are becoming more powerful and more rapidly
regulating.
[0051] The problem is due to an inherently poor damping in the
converter sets resulting in power fluctuations on the three-phase
side (the network side) and thereby a reduction in the quality of
electricity. In addition the fluctuations cause increased
mechanical wear on the actual sets.
[0052] A controlled series reactor in connection with the
transformer that supplies the converter sets from the network side
may be a very effective measure for stabilising its operation.
[0053] Portable Control Unit for a Variety of Applications
[0054] The need for stationary control units in the network will
naturally vary as a result of load changes, network development or
special temporary requirements. It may also be envisaged that even
though there will almost always be a need for a control unit, the
best position in the network will change with time. It may
therefore be difficult to defend such an investment in the network
since one does not know where or for how long there will be a need
for the component.
[0055] This provides the motivation for developing compact control
units, which are transportable, and which have great flexibility
with regard to applications. By flexible applications in this
context we mean both flexibility regarding control function and
connection to the network (different voltage levels, series or
shunt connection, etc.).
[0056] As a specific example one may envisage a unit mounted on a
semitrailer and consisting of controllable reactors, possibly in
combination with a capacitor battery, and with the necessary
equipment for protection and network connection. The control system
must be flexible and configurable, thus enabling the unit to be
used for different purposes, such as reactive compensation, active
voltage regulation and voltage quality improvement or damping of
power fluctuations.
[0057] Other concrete examples of applications of the invention
will be
[0058] Earth current compensation.
[0059] Use as a fault current limiter. Possibility of making
generator switches cheaper and smaller.
[0060] In a second embodiment the invention constitutes a circuit
component in the form of a transformer device (patent claim 7),
i.e. a circuit component where there are two main windings and one,
or possibly two control windings, thus permitting the transformer's
transformation ratio to be changed by means of one or more control
current(s).
[0061] Such an embodiment of the invention is illustrated in FIGS.
9 and 10. FIG. 9 illustrates two three-phase transformers
comprising adjustable circuit components. FIG. 10 illustrates the
principle behind this embodiment of the invention. Around the
magnetisable body 1 is an additional main winding A3 connected in
such a manner that the windings A1 and A3 together with the body 1
form a transformer. The control winding A2 is still present and
will regulate the transmission ratio of the transformer. It is also
possible to wind the main winding A3 around the same axis as the
control winding.
[0062] An important area of application for such a transformer will
be new systems for voltage regulation (patent claim 8) in
connection with transformers that will replace the known automatic
on-load tap changers. The function will therefore be mainly voltage
regulation. The advantages of increased utilisation of transformers
with a new "tap changer" are; reliability, maintenance, regulation,
equally valid in all kinds of network (distribution, regional and
central networks).
[0063] Amongst the advantages that will be obtained with the
invention is a faster and more precise voltage regulation (simpler
with coordinated control).
[0064] The output for a circuit component according to the
invention will be 200-2000 A.
[0065] With regard to regulation requirements, there will be no
need for rapid regulation, but a regulation of the order of 10
seconds to 1 minute will suffice.
[0066] As far as the losses are concerned, these can be compared to
those for conventional transformers.
[0067] A major advantage of this embodiment of the invention is
that it will lead to much lower maintenance costs compared with
today's tap changers.
[0068] As alternative solutions, i.e. solutions according to the
prior art, we may mention traditional automatic tap changers.
[0069] This embodiment of the invention can also be employed in
connection with a phase angle regulator (patent claim 9), which
will thereby comprise a transformer component according to the
invention. By regulating the control current it will be possible to
control the phase shift between the primary and the secondary side.
A phase angle regulator of this type is illustrated in FIG. 12. In
this case a variety of technical solutions can be envisaged, such
as an adjustable series transformer (a series-connected transformer
with voltage regulation). The function of the phase angle regulator
will be mainly load flow regulation, and possibly
stabilisation.
[0070] The introduction of this embodiment of the invention will
lead to increased network utilisation (increased load limits) as a
result of the possibility for rapid regulation of load flow (in
normal operation or after a fault) and improved stability.
[0071] The power transfer will be of the order of 200-1000 MVA (132
kV-420 kV).
[0072] Regulation will depend on the function (static power
distribution or also dynamic regulation and stabilisation). For
pure load flow regulation the band width requirement will be in the
area of seconds (0.1-1 Hz).
[0073] The protection requirements will be the same as for the
series compensation.
[0074] As far as losses are concerned, the stationary losses should
be low, but what is acceptable for each application will be
dependent on the component's total utilisation value.
[0075] A special advantage that may be mentioned in association
with this embodiment of the invention is greater flexibility in
operation of the network.
[0076] The alternative solutions according to the prior art will be
static series compensators (SSSC), phase distortion transformers,
UPFC.
[0077] The voltage and phase angle regulator may advantageously
form a part of a regulation system according to the invention,
where, as mentioned earlier, the system comprises a measuring unit,
a processing unit and possibly a unit for manual input of desired
values.
[0078] All the above-mentioned embodiments of the invention are
particularly suitable for use on the seabed or other high-pressure
locations.
* * * * *