BACKGROUND
The invention generally relates to power conversion systems and, more
particularly, to power conversion systems being able to withstand certain switch
failures.
With the rising cost and scarcity of conventional energy sources and
concerns about the environment, there is a significant interest in alternative energy
sources such as solar power and wind power. The alternative energy sources are used
to generate power by employing different power conversion systems for different
alternative sources of energy. A power conversion system generally includes at least
one power converter for converting generated power from at least one power source
to usable power for transmission to a power grid.
The power conversion system includes one or more stages of power
conversion to provide the usable power. Each stage includes a plurality of switches
that convert the input power from the power source. The switches are susceptible to
damage due to various conditions such as current overloading. The failure of anyone
of the switches in a conventional power converter leads to temporary suspension of
the operation of the whole power converter until the failed switch is replaced. The
temporary suspension of the power converter results in power production losses and
reduced operational time. Furthermore, the failure also negatively impacts the power
converter's availability rating when it is still largely functional although not able to
operate due to the failure of a single component.
The failure of a switch may also result In an explosion that creates
undesired projectiles of debris from the exploded switch. The undesired projectiles
may damage the adjacent switches.
Hence, there is a need for an improved system to address the
aforementioned issues.
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BRIEF DESCRIPTION
In one embodiment, a power converter is provided. The power
converter includes switches electrically coupled to each other and configured to
convert input power to output power, wherein each of the switches is sufficiently
isolated to protect adjacent switches upon failure of one or more of the switches. The
power converter also includes a controller for reconfiguring operation of the switches
to provide at least a partial operating mode upon failure of the one or more switches.
In another embodiment, a power conversion system is provided. The
power conversion system includes a DC-DC power converter comprising at least two
legs coupled in parallel, each leg comprising at least two switches couplable at a
midpoint to a DC power source and sufficiently isolated to protect adjacent switches
upon failure of one or more of the switches. The power conversion system also
includes a controller for controlling operating time of the switches of the at least two
legs to provide a combined DC output power and, upon failure of at least one of the
switches in one of the at least two legs, adjusting the operating time of at least the
switches of the remainder of the at least two legs to provide a reduced combined DC
output power.
In yet another embodiment, a power conversion system comprising a
DC-AC power converter is provided. The DC-AC power converter includes at least
two phase legs coupled in parallel, each leg comprising at least two sets of switches
coupled in series, wherein each of the at least two sets comprises a plurality of
switches electrically coupled in parallel to each other and sufficiently isolated to
protect adjacent switches upon failure of one or more of the switches. The power
conversion system also includes a controller for controlling a combined AC output
power by adjusting AC output power generated from each phase leg upon failure of at
least one of the switches in at least one of the two sets of switches.
DRAWINGS
These and other features, aspects, and advantages of the present
invention will become better understood when the following detailed description is
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read with reference to the accompanying drawings in which like characters represent
like parts throughout the drawings, wherein:
FIG. I is a schematic representation of a power converter including a
plurality of sufficiently isolated switches in accordance with an embodiment of the
invention.
FIG. 2 is a more detailed schematic representation of a switch
sufficiently isolated by a blast shield provided in a power converter in accordance
with an embodiment of the invention.
FIG. 3 is a schematic representation of a power conversion system
including an adaptive DC-DC converter comprising exactly two switches sufficiently
isolated by blast shield in each leg of the adaptive DC-DC power converter in
accordance with an embodiment of the invention.
FIG. 4 is a schematic representation of a power conversion system
including an adaptive DC-DC power converter and an adaptive DC-AC power
converter.
DETAILED DESCRIPTION
Unless defined otherwise, technical and scientific terms used herein
have the same meaning as is commonly understood by one of ordinary skill in the art
to which this disclosure belongs. The terms "first", "second", and the like, as used
herein do not denote any order, quantity, or importance, but rather are used to
distinguish one element from another. Also, the terms "a" and "an" do not denote a
limitation of quantity, but rather denote the presence of at least one of the referenced
items. The term "or" is meant to be inclusive and mean one, some, or all of the listed
items. The use of "including," "comprising" or "having" and variations thereof herein
are meant to encompass the items listed thereafter and equivalents thereof as well as
additional items. The terms "connected" and "coupled" are not restricted to physical
or mechanical connections or couplings, and can include electrical connections or
couplings, whether direct or indirect. Furthermore, the terms "circuit" and "circuitry"
4
and "controller" may include either a single component or a plurality of components,
which are either active and/or passive and are connected or otherwise coupled
together to provide the described function.
Embodiments of the present invention include an adaptive power
converter that includes switches electrically coupled to each other and configured to
convert input power to output power. Each of the switches is sufficiently isolated to
protect adjacent switches upon failure of one or more switches. The power converter
also includes a controller for reconfiguring operation of the switches to provide at
least a partial operating mode upon failure of the one or more switches.
FIG. 1 is a schematic representation of a power conversion system 10
comprising a power converter 12 including a plurality of sufficiently isolated switches
14 in accordance with an embodiment of the invention. The switches 14 are
electrically coupled to each other and convert input power to an output power. Each
of the switches 14 is sufficiently isolated to protect adjacent switches upon failure of
one or more of the switches. In one embodiment, each of the plurality of switches is
sufficiently isolated by a blast shield. In other embodiments, the switches may be
separated by compartments or sufficient physical distance, for example. For purposes
of example, the invention will be discussed in greater detail below with respect to the
blast shield.
FIG. 2 is a schematic representation of a blast shield-encased switch
14. The blast shield-encased switch 14 comprises a power switch 18 mounted on a
heat sink 20. Power switch 18 may comprise a semiconductor switch, for example.
In one more specific embodiment, the switch 18 comprises an insulated gate bipolar
transistor. The switch 18 is further encased in a blast shield 16 that protects the
adjacent switches from damage by restricting any explosion caused upon failure of the
encased switch. In one embodiment, the blast shield comprises a fiber material, a
composite material, or combinations thereof. In a more specific embodiment, the
blast shield 16 comprises woven para-aramid synthetic fibers such as Kevlar™ fibers,
fiberglass material, other high strength composite materials, or combinations thereof.
5
Referring back to FIG. 1, the switches 14 convert the input power to
the output power. In a non-limiting example, the input power may include DC power
or AC power, and the output power includes AC power. In one embodiment, the
switches 14 are electrically coupled in such a manner that the input power is
converted to the output power in two stages including a first stage 22 including one of
an AC-DC conversion stage or a DC-DC conversion stage and a second stage 24
including a DC-AC conversion stage. In a specific embodiment, the first stage 22
comprises an AC-DC power conversion stage in wind turbine applications, and the
first stage comprises a DC-DC conversion stage in solar power applications. In an
exemplary embodiment, each stage includes three legs.
The first stage 22 of power conversion in the power converter 12 is
electrically coupled to a power source 26. In one embodiment, the power source 26
may include a solar power source, a wind power source, a battery, or a fuel cell. The
first stage 22 receives the input power from the power source 26 and converts the
input power to a combined DC power. The second stage 24 of power conversion in
the power converter 12 receives the combined DC power and converts the combined
DC power to the output power that is fed to a power grid 28.
The power converter 12 includes a controller 30 that controls the
operation of the switches 14 to convert the input power to the output power. While in
operation, one or more of the switches 14 may be damaged. The blast shields 16
(shown in FIG. 2) protect the adjacent switches from damage and limit the explosion
of the damaged switch or switches. The controller 30 reconfigures the operation of
the undamaged switches to operate the power converter 12 in at least a partial
operating mode until the failed switch has been replaced. In one embodiment, the
power converter includes an inverter operating at at least one megawatt.
FIG. 3 is a schematic representation of a power conversion system 10
including an adaptive DC-DC converter 32 comprising two switches 14, each switch
sufficiently isolated by a blast shield in each leg of the adaptive DC-DC converter 32
in accordance with an embodiment of the invention. For better understanding of the
invention, the operation of the power converter 12 described above would be
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discussed with respect to a solar power conversion system 10 comprising the DC-DC
converter 32 in the first stage 22 and a DC-AC converter 34 in the second stage 24 of
the power converter 12. The solar power conversion system 10 includes a solar
power source 26 that generates input DC power that is fed to the DC-DC converter 32
in the power converter 12. The DC-DC converter 32 in the specific example
comprises at least two legs (shown as three legs 36, 38 and 40 for purposes of
example) that are coupled in parallel. Each leg includes at least two blast shield
encased switches 14 couplable at midpoint to the solar power source 26. In one
embodiment, each leg includes exactly two blast shield-encased switches 14. In
another embodiment, more than two switches may be used per leg. The DC-DC
converter 32 is coupled to the controller 30 that controls the operation of the switches
14 by interleaving DC output power generated from each of the at least three legs 36,
38 and 40 to provide the combined DC output power.
During operation, upon failure of at least one of the switches 42, the
controller 30 adjusts the switching time of the remaining switches to provide a
reduced combined DC output power. In the specific embodiment, wherein, each leg
includes exactly two switches 14 and at least one of the switches 42 in the at least one
leg 38 have failed, the entire leg 38 is rendered unusable, and the controller 30 adjusts
the gating of the remaining legs 36 and 40 to provide the reduced combined DC
output power. In this embodiment, although one of the legs 38 has failed, the
remaining legs 36 and 40 may still operate at full capacities and provide the reduced
combined DC power that is generated by the remaining legs 38 and 40. In this
embodiment, the controller 30 operates each the remaining switches to provide a
balanced level of DC output power from each of the remaining legs 36 and 40.
Furthermore, if a leg fails completely and has to be removed from operation, to
provide a reduced or minimum DC ripple, the controller redistributes the operating
time of the remaining switches such that the remaining switches operate at equidistant
times without leaving an unaccounted time slot of the failed leg. In cases where all or
too many legs have switch failures such that it is not possible to provide a balanced
level of DC output power, the controller 30 may need to shut down the operation of
the DC-DC converter 32.
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The combined DC output power from the DC-DC converter 32 is then
transmitted to the DC-AC converter 34 to convert the combined DC output power to
the output power.
FIG. 4 is a schematic representation of the solar power conversion
system 10 including an adaptive DC-DC converter 32 and an adaptive DC-AC
converter 34 wherein redundant switches are included in accordance with another
embodiment of the invention. In the embodiment of FIG. 4, the DC-DC converter 32
and the DC-AC converter 34 each comprise two sets 44 and 46 of switches
electrically coupled in parallel in each leg of the respective power converters 32 and
34.
The DC-DC converter 32 includes two sets 44 and 46 of blast shield
encased switches 14 electrically coupled in parallel in each leg of the DC-DC
converter 32 and converts the input DC power to the combined DC output power.
The controller 30 controls the operations of the plurality of blast shield encased
switches 14 to convert the input power to the combined DC power. The controller 30
reconfigures the switching operation of the switches 14 to adjust the combined DC
power upon failure of at least one of the switches 48 in at least one of the sets 44 and
46 in one or more legs of the DC-DC converter 32. When only a switch, such as
switch 48 in FIG. 4, fails in a given set 44, then the entire leg need not be shut down
in this embodiment. Instead, the gating may be adjusted to account for the loss of the
switch and also adjust the values of expected current flows used within the DC-DC
converter 32 controls. In this embodiment, when one of the switches such as 48 has
failed, the leg 36 (FIG. 3) operates at a reduced capacity and the remaining legs 36
(FIG. 3) and 40 (FIG. 3) may optionally operate at full capacities to provide the
reduced combined DC power. If an entire set 44 or 46 in one leg of DC-DC converter
32 fails, then the leg is not usable, and the adjustments discussed with respect to FIG.
3 may be used. In cases where all or too many sets of legs have switch failures such
that it is not possible to provide a balanced level of DC output power, the controller
30 may need to shut down the operation ofthe DC-DC converter 32.
8
The DC-AC converter 34 receives the combined DC power from the
DC-DC converter 32 and converts the combined DC power to an AC power. The
DC-AC converter 34 includes at least two legs coupled in parallel. Each leg includes
at least two sets 50 and 52 of blast shield encased switches coupled in series. Each of
the at least two sets 50 and 52 includes a plurality of blast shield encased switches 14
electrically coupled in parallel to each other. Controller 30 controls the switches 14 to
provide a combined AC output power. In operation, upon failure of at least one of the
switches 54 in at least one of the two sets of switches 52, the controller 30 adjusts the
AC output power generated from each phase leg to provide a reduced combined AC
power. In one embodiment, as the amount of voltage that the affected leg may
produce is reduced, to balance the output voltage, the controller 30 may also operates
the remaining legs at reduced power to provide a more balanced AC output power. In
a specific embodiment, the controller 30 shuts down the operation of the DC-AC
converter 34 upon failure of each of the switches of at least one set among the two
sets 50 and 52. In cases where all or too many sets of legs have partial switch failures
such that it is not possible to provide a balanced level of AC output power, the
controller 30 may need to shut down the operation of the DC-AC converter 34.
The various embodiments of the solar power generation system
described above provide a more efficient and reliable solar power generation system.
The system described above enables more operational time for the power converter
and reduces damages in the power converter resulting in less maintenance.
It is to be understood that a skilled artisan will recognize the
interchangeability of various features from different embodiments and that the various
features described, as well as other known equivalents for each feature, may be mixed
and matched by one of ordinary skill in this art to construct additional systems and
techniques in accordance with principles of this disclosure. It is, therefore, 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.
While only certain features of the invention have been illustrated and
described herein, many modifications and changes will occur to those skilled in the
9
art. It is, therefore, 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.

WE CLAIM:
1. A power converter comprising:
a plurality of switches electrically coupled to each other for converting input
power to output power, wherein each of the plurality of switches is sufficiently
isolated to protect adjacent switches upon failure of one or more of the plurality of
switches; and
a controller for reconfiguring operation of the plurality of switches to provide
at least a partial operating mode upon failure of the one or more switches.
2. The power converter of claim 1, wherein the plurality of switches are
electrically coupled to form a two stage power converter.
3. The power converter of claim 2, wherein the two stages comprise a
first stage comprising an AC-DC conversion stage or a DC-DC conversion stage and
a second stage comprising a DC-AC conversion stage.
4. The power converter of claim 2, wherein each stage of the power
converter comprises three legs.
5. The power converter of claim 1, wherein the plurality of switches
comprises insulated gate bipolar transistors.
6. The power converter of claim 1, wherein the plurality of switches are
sufficiently isolated by enclosing each of the plurality of switches in a blast shield.
11
7. The power converter of claim 6, wherein the blast shield comprises a
fiber material, a composite material, or combinations thereof.
8. A power conversion system comprising:
a DC-DC power converter comprising at least two legs coupled in parallel,
each leg comprising at least two switches couplable at a midpoint to a DC power
source and sufficiently isolated to protect adjacent switches upon failure of one or
more of the switches; and
a controller for controlling operating time of the switches of the at least two
legs to provide a combined DC output power and, upon failure of at least one of the
switches in one of the at least two legs, adjusting the operating time of at least the
switches of the remainder of the at least two legs to provide a reduced combined DC
output power.
9. The system of claim 8, wherein each leg of the power converter
comprises exactly two switches, and wherein, upon failure of at least one of the
switches in at least one leg, the controller is configured to adjust the operating time of
the remaining legs to provide the reduced combined DC power.
10. The system of claim 8, wherein each leg of the DC-DC power
converter comprises a first set of switches coupled in parallel on one side of the
midpoint and a second set of switches coupled in parallel on the other side of the
midpoint.
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11. The system of claim 8, wherein the controller is further configured for
operating each of the remaining switches to provide a reduced level of DC output
power ripple.
12. The system of claim 8, wherein the DC-DC power converter is coupled
to a solar power source.
13. The system of claim 8, wherein each of the at least two switches are
sufficiently isolated by enclosing each of the switches in a blast shield.
14. A power conversion system comprising:
a DC-AC power converter comprising at least two phase legs coupled in
parallel, each leg comprising at least two sets of switches coupled in series, wherein
each of the at least two sets comprises a plurality of switches electrically coupled in
parallel to each other and sufficiently isolated to protect adjacent switches upon
failure of one or more of the switches; and
a controller for controlling a combined AC output power by adjusting AC
output power generated from each phase leg upon failure of at least one of the
switches in at least one of the two sets of switches.
15. The system of claim 14, wherein the controller is configured to operate
the leg comprising at least one of the failed switches to provide reduced AC output
power.
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16. The system of claim 14, wherein the controller is further configured to
operate remaining switches of the at least one set of each leg to provide a balanced
AC output power to provide a reduced combined AC power.
17. The system of claim 14, wherein the controller is configured to shut
down the operation of the DC-AC power converter when each of the plurality of
switches of at least one set among the two sets have failed.
18. The system of claim 14, wherein the DC-AC power converter is
coupled to a renewable power generation source.
19. The system of claim 14, further comprising blast shields for isolating
each of the switches.
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v MANISHA S~-NAIR
Agent for the Applicant [IN/PA-740]
LEX ORBIS
Intellectual Property Pnctice
7091710, Tolstoy House,
15-17, Tolstoy Marg,
New Delhi-II 000 I