U.S. patent application number 15/106257 was filed with the patent office on 2016-10-20 for apparatus and method for supplying hybrid power in marine plant.
This patent application is currently assigned to DAEWOO SHIPBUILDING & MARINE ENGINEERING CO., LTD.. The applicant listed for this patent is DAEWOO SHIPBUILDING & MARINE ENGINEERING CO., LTD.. Invention is credited to Ho Young JUNG, Dong Jae SHIN.
Application Number | 20160308362 15/106257 |
Document ID | / |
Family ID | 53517860 |
Filed Date | 2016-10-20 |
United States Patent
Application |
20160308362 |
Kind Code |
A1 |
JUNG; Ho Young ; et
al. |
October 20, 2016 |
APPARATUS AND METHOD FOR SUPPLYING HYBRID POWER IN MARINE PLANT
Abstract
The present invention relates to an apparatus and method for
supplying hybrid power using a regenerative power generated in a
marine plant. An embodiment of the present invention provides a
hybrid power supply apparatus in a marine plant, the hybrid power
supply apparatus comprising: a generator; an AC/DC converter which
converts an alternating current produced by the generator into a
direct current and supplies the direct current to a DC bus; a power
load which is connected to the DC bus and generates a regenerative
power; a first DC/DC converter which is connected to the DC bus; a
first power storage unit which is connected to the first DC/DC
converter and stores power; and a first resistor unit which is
connected to the first DC/DC converter and consumes power when the
first power storage unit's capacity is full.
Inventors: |
JUNG; Ho Young; (Geoje-si,
KR) ; SHIN; Dong Jae; (Geoje-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DAEWOO SHIPBUILDING & MARINE ENGINEERING CO., LTD. |
Seoul |
|
KR |
|
|
Assignee: |
DAEWOO SHIPBUILDING & MARINE
ENGINEERING CO., LTD.
Seoul
KR
|
Family ID: |
53517860 |
Appl. No.: |
15/106257 |
Filed: |
December 18, 2014 |
PCT Filed: |
December 18, 2014 |
PCT NO: |
PCT/KR2014/012539 |
371 Date: |
June 17, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02J 2300/10 20200101;
H02M 3/04 20130101; H02P 3/18 20130101; Y02E 60/60 20130101; H02J
7/34 20130101; E21B 3/02 20130101; H02J 1/106 20200101; H02J 1/102
20130101; H02J 3/32 20130101; H02J 3/381 20130101; Y02E 60/16
20130101; H02M 7/04 20130101; H02J 3/36 20130101; H02J 7/345
20130101; H02J 3/28 20130101; H02J 1/00 20130101; H02J 2310/12
20200101; H02J 3/30 20130101 |
International
Class: |
H02J 3/38 20060101
H02J003/38; E21B 3/02 20060101 E21B003/02; H02P 3/18 20060101
H02P003/18 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 18, 2013 |
KR |
10-2013-0158009 |
Jun 19, 2014 |
KR |
10-2014-0075132 |
Jun 19, 2014 |
KR |
10-2014-0075136 |
Claims
1. A hybrid power supply apparatus for an offshore plant,
comprising: a power generator; an AC/DC converter converting
alternating current produced by the power generator into direct
current and supplying the direct current to a DC bus; an electric
power load connected to the DC bus and generating regenerative
power; a first DC/DC converter connected to the DC bus; a first
power storage unit connected to the first DC/DC converter and
storing electric power; and a first resistor connected to the first
DC/DC converter and consuming electric power when the first power
storage unit is full.
2. The hybrid power supply apparatus according to claim 1, wherein
the first DC/DC converter measures voltage of the DC bus, and
allows the first power storage unit to store electric power when
the voltage of the DC bus is maintained at a first threshold value
or higher for a first period of time.
3. The hybrid power supply apparatus according to claim 2, wherein
the first DC/DC converter measures the voltage of the DC bus, and
allows the first resistor to consume electric power when the
voltage of the DC bus is maintained at the first threshold value or
higher for a second period of time, and wherein the second period
of time is longer than the first period of time.
4. The hybrid power supply apparatus according to claim 2, further
comprising: a second power storage unit and a second resistor.
5. The hybrid power supply apparatus according to claim 4, wherein
the DC bus is connected to a second DC/DC converter, and the second
power storage unit and the second resistor are connected to the
second DC/DC converter.
6. The hybrid power supply apparatus according to claim 1, wherein
the first power storage unit is an ultracapacitor.
7. The hybrid power supply apparatus according to claim 1, wherein
the electric power load is a draw-works.
8. The hybrid power supply apparatus according to claim 1, wherein
the electric power load is a top drive.
9. A hybrid power supply method for an offshore plant, comprising:
measuring, by a DC/DC converter, voltage of a DC bus; storing, by a
first power storage unit, electric power when the voltage of the DC
bus is maintained at a first threshold value or higher for a first
period of time; and consuming, by a resistor, electric power when
the voltage of the DC bus is maintained at the first threshold
value or higher for a second period of time, wherein the DC bus is
connected to a first electric power load generating regenerative
power and the second period of time is longer than the first period
of time.
10. The hybrid power supply method according to claim 9, wherein
the DC/DC converter measures the voltage of the DC bus, and allows
electric power to flow from the DC bus to the first power storage
unit such that the first power storage unit stores electric power,
when the voltage of the DC bus is maintained at the first threshold
value or higher for the first period of time.
11. The hybrid power supply method according to claim 10, wherein
the DC/DC converter measures the voltage of the DC bus, and allows
electric power to flow from the DC bus to the resistor such that
the resistor consumes electric power when the voltage of the DC bus
is maintained at the first threshold value or higher for the second
period of time.
12-16. (canceled)
17. The hybrid power supply apparatus according to claim 1, further
comprising a first DC/AC converter connecting the electric power
load with the DC bus, wherein the first DC/AC converter detects
whether regenerative power is generated in the electric power load,
and sends a control signal to the first DC/DC converter when
regenerative power is generated in the electric power load, and the
first DC/DC converter allows electric power to be supplied from the
DC bus to the first power storage unit in response to the control
signal such that the first power storage unit stores electric
power.
18. The hybrid power supply apparatus according to claim 17,
wherein the first DC/DC converter allows electric power to be
supplied from the DC bus to the first resistor such that the first
resistor consumes electric power when detecting that the first
power storage unit is full.
19-22. (canceled)
23. The hybrid power supply method according to claim 9, further
comprising: detecting, by a first DC/AC converter, whether
regenerative power is generated in the first electric power load;
storing, by the first power storage unit, regenerative power
generated in the first electric power load; detecting, by a second
DC/AC converter, whether regenerative power is generated in a
second electric power load; and storing, by a second power storage
unit, regenerative power generated in the second electric power
load; wherein the first DC/AC converter and the second DC/AC
converter are connected to a DC bus, the first electric power load
is connected to the first DC/AC converter, and the second electric
power load is connected to the second DC/AC converter.
24-30. (canceled)
Description
TECHNICAL FIELD
[0001] The present invention relates to hybrid power supply for an
offshore plant, and, more particularly, to a hybrid power supply
apparatus and method using regenerative power generated in an
offshore plant.
BACKGROUND ART
[0002] With rapid industrialization and industrial development,
consumption of resources such as petroleum has increased, and
stable production and supply of oil have become a crucial global
problem.
[0003] For this reason, development of smaller marginal fields or
deep-sea oil fields, which has been ignored due to lack of economic
feasibility, is now emerging. Thus, development of offshore plants
provided with oil drilling equipment suitable for use in such oil
fields is actively carried out along with development of seabed
mining technology.
[0004] An offshore plant is provided with various types of
drilling-related equipment such as a Derrick crane system, a
draw-works, a top drive, a mud pump, a cement pump, a riser, and a
drill pipe.
[0005] The draw-works performs lifting of the drill pipe, insertion
of a casing, and the like, and includes a drum and a motor. The
drum is powered by the motor so as to wind or unwind a wire rope
for controlling lifting of the drill pipe. The rotational speed of
the motor can be adjusted so as to adjust the rotational speed of
the drum, thereby enabling adjustment of the speed of the drill
pipe.
[0006] The top drive provides power for drilling and pipe fastening
in drilling operation.
[0007] Offshore plants are divided into a stationary platform
anchored at one point of nearshore to perform drilling operations
and a floating offshore plant capable of performing drilling
operation at ocean depths of 3,000 m or more.
[0008] The floating offshore plant is provided with a plurality of
thrusters as a main propulsion device or a propulsion device for
computer-aided dynamic positioning. The thrusters are located at
the bottom of a ship to change an operating direction of a
propeller and are commonly used to allow the ship to navigate or to
sail in a canal or enter/leave a port under its own power without a
tug. The thruster is powered by a thrust motor connected
thereto.
[0009] FIG. 1 is a diagram of a typical power supply system known
in the art.
[0010] Referring to FIG. 1, AC power generated by a power generator
110 is supplied to an AC bus, to which a first AC/DC converter 121,
a second AC/DC converter 122, and a third AC/DC converter 123 are
connected.
[0011] The first AC/DC converter 121 converts alternating current
supplied from the AC bus into direct current and supplies the
direct current to a first DC bus 131, and a DC/AC converter 141
converts direct current supplied from the first DC bus 131 into
alternating current and supplies the alternating current to a first
thruster motor 151.
[0012] The second AC/DC converter 122 converts alternating current
supplied from the AC bus into direct current and supplies the
direct current to a second DC bus 132, and a DC/AC converter 142
converts direct current supplied from the second DC bus 132 into
alternating current and supplies the alternating current to a
second thruster motor 152.
[0013] The third AC/DC converter 123 converts alternating current
supplied from the AC bus into direct current and supplies the
direct current to a third DC bus 133, and a plurality of DC/AC
converters 143 to 148 are connected to the third DC bus 133. The
plurality of DC/AC converters 143 to 148 convert direct current
supplied from the third DC bus 133 into alternating current and
supply the alternating current to corresponding ones of a plurality
of draw-works motors 153, 154, 155, 158, 159 and a plurality of top
drive motors 156, 157.
[0014] Since the draw-works motors 153, 154, 155, 158, 159 and the
top drive motors 156, 157 are configured to repeatedly lift or
lower drilling equipment such as a drill pipe, a brake is
frequently put on the motors to bring the motors to a sudden stop
or to rotate the motors in a reverse direction during rotation at
rated load, and, for the thruster motors 151, 152, a brake is also
frequently put on the motors to bring the motors to a sudden stop
or to rotate the motors in the reverse direction during rotation at
rated load. When a brake is put on the motors, regenerative power
is generated in the motors. In addition, when a thruster is rotated
due to a disturbance, regenerative power is also generated in the
thruster motors.
[0015] When regenerative power is generated in the draw-works
motors, the top drive motors, or the thruster motors, voltage of a
DC bus connected to the draw-works motors, the top drive motors, or
the thruster motors is increased, and, when the voltage is
increased beyond a degree which the DC bus can accommodate, the DC
bus is tripped.
[0016] Thus, the typical power supply system is provided with
resistors 161 to 166 to consume regenerative power as heat, thereby
preventing the DC bus from tripping.
[0017] FIG. 2 is a graph showing power consumption of each
component of a typical power supply system known in the art.
[0018] Referring to FIG. 2, electric power produced by a power
generator is supplied to a first load 220 and an AC/DC converter
260 through a distributor. The AC/DC converter 260 converts
alternating current into direct current and supplies the direct
current to a second load 240 while supplying the direct current to
a draw-works 230 through a DC/AC converter. Each of the first load
220 and the second load 240 is a load that consumes a constant
level of electric power. On the contrary, power consumption of the
draw-works 230 changes continuously, and, in FIG. 2, a negative
value of electric power means that regenerative power is generated.
Regenerative power generated in the draw-works 230 is consumed by
the second load or a resistor 250.
[0019] In FIG. 2, it can be seen that abrupt change in power
consumption of the draw-works 230 causes abrupt change in power
output of the power generator 210. A diesel power generator
consumes more fuel and discharges more exhaust gas in the case
where power output is abruptly changed than in the case where power
output is maintained at a constant level.
[0020] In order to supply suitable electric power corresponding to
abrupt change in power consumption of the draw-works motors, the
top drive motors, and the thruster motors, it is necessary to
rapidly change power output of the power generator. However, the
power generator has difficulty providing suitable electric power
corresponding to abrupt change in power consumption of the
draw-works motors, the top drive motors, and the thruster motors
due to low responsiveness thereof. If suitable power supply to the
draw-works motors, the top drive motors, and the thruster motors is
not achieved, a dangerous situation can occur due to
characteristics of drilling operation. Further, when power supply
to the draw-works motors or the top drive motors is suddenly
interrupted upon loss of power, a dangerous situation can also
occur.
[0021] In other words, typical power supply systems have problems
such as energy waste due to consumption of regenerative power by
resistors, increase in fuel consumption and exhaust gas due to
abrupt change in power output of a power generator, difficulty in
suitable electric power supply to draw-works motors, top drive
motors, and thruster motors, and danger upon loss of power.
DISCLOSURE
Technical Problem
[0022] It is an aspect of the present invention to provide a hybrid
power supply apparatus and method for an offshore plant which can
efficiently utilize regenerative power, maintain power output of a
generator at a constant level, supply suitable electric power
corresponding to abrupt change in power consumption of electric
loads, and supply electric power upon sudden loss of power.
Technical Solution
[0023] In accordance with one aspect of the present invention,
there is provided a hybrid power supply apparatus for an offshore
plant, including: a power generator; an AC/DC converter converting
alternating current produced by the power generator into direct
current and supplying the direct current to a DC bus; an electric
power load connected to the DC bus and generating regenerative
power; a first DC/DC converter connected to the DC bus; a first
power storage unit connected to the first DC/DC converter and
storing electric power; and a first resistor connected to the first
DC/DC converter and consuming electric power when the first power
storage unit is full.
[0024] The first DC/DC converter may measure voltage of the DC bus,
and may allow the first power storage unit to store electric power
when the voltage of the DC bus is maintained at a first threshold
value or higher for a first period of time.
[0025] The first DC/DC converter may measure the voltage of the DC
bus, and may allow the first resistor to consume electric power
when the voltage of the DC bus is maintained at the first threshold
value or higher for a second period of time, and wherein the second
period of time is longer than the first period of time.
[0026] The hybrid power supply apparatus may further include: a
second power storage unit and a second resistor.
[0027] The DC bus may be connected to a second DC/DC converter, and
the second power storage unit and the second resistor may be
connected to the second DC/DC converter.
[0028] The first power storage unit may be an ultracapacitor.
[0029] The electric power load may be a draw-works.
[0030] The electric power load may be a top drive.
[0031] In accordance with another aspect of the present invention,
there is provided a hybrid power supply method for an offshore
plant, including: measuring, by a DC/DC converter, voltage of a DC
bus; storing, by a power storage unit, electric power when the
voltage of the DC bus is maintained at a first threshold value or
higher for a first period of time; and consuming, by a resistor,
electric power when the voltage of the DC bus is maintained at the
first threshold value or higher for a second period of time,
wherein the DC bus is connected to an electric power load
generating regenerative power and the second period of time is
longer than the first period of time.
[0032] The DC/DC converter may measure the voltage of the DC bus,
and may allow electric power to flow from the DC bus to the power
storage unit such that the power storage unit stores electric
power, when the voltage of the DC bus is maintained at the first
threshold value or higher for the first period of time.
[0033] The DC/DC converter may measure the voltage of the DC bus,
and may allow electric power to flow from the DC bus to the
resistor such that the resistor consumes electric power when the
voltage of the DC bus is maintained at the first threshold value or
higher for the second period of time.
[0034] The power storage unit may be an ultracapacitor.
[0035] The electric power load may be a draw-works.
[0036] The electric power load may be a top drive.
[0037] In accordance with a further aspect of the present
invention, there is provided a hybrid power supply apparatus for an
offshore plant, including: a power generator; an AC/DC converter
converting alternating current produced by the power generator into
direct current and supplying the direct current to a DC bus; a
first electric power load connected to the DC bus via a first DC/AC
converter and generating regenerative power; a first power storage
unit storing regenerative power when regenerative power is
generated in the first electric power load; a first resistor
consuming electric power when the first power storage unit is full;
a second electric power load connected to the DC bus via a second
DC/AC converter and generating regenerative power; a second power
storage unit storing regenerative power when regenerative power is
generated in the second electric power load; and a second resistor
consuming electric power when the second power storage unit is
full.
[0038] The hybrid power supply apparatus may further include: a
first DC/DC converter connected to the DC bus; and a second DC/DC
converter connected to the DC bus, wherein the first power storage
unit and the first resistor are connected to the first DC/DC
converter, and the second power storage unit and the second
resistor are connected to the second DC/DC converter.
[0039] The first DC/AC converter may detect whether regenerative
power is generated in the first electric power load, and send a
control signal to the first DC/DC converter when regenerative power
is generated in the first electric power load, and the first DC/DC
converter may allow electric power to be supplied from the DC bus
to the first power storage unit in response to the control signal
such that the first power storage unit stores electric power.
[0040] The first DC/DC converter may allow electric power to be
supplied from the DC bus to the first resistor such that the first
resistor consumes electric power when detecting that the first
power storage unit is full.
[0041] The first power storage unit may be an ultracapacitor.
[0042] The first electric power load may be a draw-works.
[0043] The first electric power load may be a top drive.
[0044] The hybrid power supply apparatus may further include: a
first DC/DC converter connected to the DC bus; a second DC/DC
converter connected to the DC bus; a third DC/DC converter
connected to the DC bus; and a fourth DC/DC converter connected to
the DC bus, wherein the first power storage unit may be connected
to the first DC/DC converter, the first resistor may be connected
to the second DC/DC converter, the second power storage unit may be
connected to the third DC/DC converter, and the second resistor may
be connected to the fourth DC/DC converter.
[0045] In accordance with yet another aspect of the present
invention, there is provided a hybrid power supply method for an
offshore plant, including: detecting, by a first DC/AC converter,
whether regenerative power is generated in a first electric power
load; storing, by a first power storage unit, regenerative power
generated in the first electric power load; detecting, by a second
DC/AC converter, whether regenerative power is generated in a
second electric power load; and storing, by a second power storage
unit, regenerative power generated in the second electric power
load, wherein the first DC/AC converter and the second DC/AC
converter may be connected to a DC bus, the first electric power
load may be connected to the first DC/AC converter, and the second
electric power load may be connected to the second DC/AC
converter.
[0046] The DC bus may be connected to a first DC/DC converter and a
second DC/DC converter; the first power storage unit and a first
resistor may be connected to the first DC/DC converter; and the
second power storage unit and a second resistor may be connected to
the second DC/DC converter.
[0047] The hybrid power supply method may further include: sending,
by the first DC/AC converter, a control signal indicative of
generation of regenerative power in the first electric power load
to the first DC/DC converter; and allowing, by the first DC/DC
converter, electric power to be supplied from the DC bus to the
first power storage unit in response to the control signal such
that the first power storage unit stores electric power.
[0048] The hybrid power supply method may further include:
detecting, the first DC/DC converter, that the first power storage
unit is full; and allowing, by the first DC/DC converter, electric
power to be supplied from the DC bus to the first resistor such
that the first resistor consumes.
[0049] The hybrid power supply method may further include:
consuming, by the second resistor, electric power when the second
power storage unit is full.
[0050] The first power storage unit may be an ultracapacitor.
[0051] The first electric power load may be a draw-works.
[0052] The first electric power load may be a top drive.
Advantageous Effects
[0053] According to embodiments of the present invention, it is
possible to provide a hybrid power supply apparatus and method
which allow regenerative power generated in a draw-works motor, a
top drive motor, and a thruster motor to be stored in a power
storage unit and supply electric power stored in the power storage
unit upon abrupt increase in power consumption of the draw-works
motor, the top drive motor, and the thruster motor to efficiently
utilize regenerative power while maintaining power output of a
power generator at a constant level to reduce exhaust gas.
[0054] In addition, it is possible to provide a hybrid power supply
apparatus and method which use an ultracapacitor having high
responsiveness as a power storage unit, thereby supplying suitable
electric power corresponding to abrupt change in power consumption
of electric loads.
[0055] Further, it is possible to provide a hybrid power supply
apparatus and method which can utilize electric power stored in a
power storage unit to safely shut down drilling equipment such as a
draw-works or a top drive upon transients or loss of power.
[0056] Furthermore, it is possible to provide a hybrid power supply
apparatus and method which can reduce the number of DC/DC
converters by connecting a power storage unit and a resistor to a
single DC/DC converter, thereby reducing equipment size and
costs.
[0057] Furthermore, it is possible to provide a hybrid power supply
apparatus and method which can operate a set of an electric power
load, a power storage unit, and a resistor in an individual manner
by allocating a dedicated power storage unit and a dedicated
resistor to a specific electric power load.
DESCRIPTION OF DRAWINGS
[0058] FIG. 1 is a diagram of a typical power supply system known
in the art.
[0059] FIG. 2 is a graph showing power consumption of each
component of a typical power supply system known in the art.
[0060] FIG. 3 is a diagram of a hybrid power supply apparatus for
an offshore plant according to a first embodiment of the present
invention.
[0061] FIG. 4 is a diagram of a hybrid power supply apparatus for
an offshore plant according to a second embodiment of the present
invention.
[0062] FIG. 5 is a diagram of a hybrid power supply apparatus for
an offshore plant according to a third embodiment of the present
invention.
[0063] FIG. 6 is a flowchart of a process of supplying electric
power to a power storage unit in a hybrid power supply method for
an offshore plant according to an embodiment of the present
invention.
[0064] FIG. 7 is a flowchart of a process of supplying electric
power from the power storage unit to a DC bus upon power shortage
in the hybrid power supply method for an offshore plant according
to the embodiment of the present invention.
[0065] FIG. 8 is a flowchart of a process of supplying electric
power from the power storage unit to the DC bus upon loss of power
in the hybrid power supply method for an offshore plant according
to the embodiment of the present invention.
[0066] FIG. 9 is a graph showing power consumption of each
component of the power supply apparatus according to the
embodiments of the present invention.
EMBODIMENTS
[0067] Hereinafter, embodiments of the present invention will be
described with reference to the accompanying drawings. It should be
noted that like components will be denoted by like reference
numerals throughout the specification and the accompanying
drawings. In addition, descriptions of details apparent to those
skilled in the art will be omitted for clarity.
[0068] First, a hybrid power supply apparatus for an offshore plant
according to embodiments of the present invention will be described
with reference to FIGS. 3 to 5. FIG. 3 is a diagram of a hybrid
power supply apparatus for an offshore plant according to a first
embodiment of the present invention, FIG. 4 is a diagram of a
hybrid power supply apparatus for an offshore plant according to a
second embodiment of the present invention, and FIG. 5 is a diagram
of a hybrid power supply apparatus for an offshore plant according
to a third embodiment of the present invention.
[0069] Referring to FIGS. 3 to 5, a hybrid power supply apparatus
for an offshore plant according to the first embodiment of the
present invention includes a power generator 310, an AC/DC
converter 320, a DC bus 321, a variable frequency drive (VFD)
controller 330, DC/DC converters 351 to 353, electric power loads
361 to 363, power storage units 371 to 373, resistors 381 to 383,
and a sensor 391.
[0070] The power generator 310 is a device producing electric power
for an offshore plant and is connected to the AC/DC converter 320
via an AC bus. Alternatively, electric power produced by the power
generator 310 may be supplied to the AC/DC converter 320 after
being altered to a voltage suitable for use in electric power
loads. The power generator 310 is an AC Generator and can produce
AC power.
[0071] The AC/DC converter 320 converts AC power produced by the
power generator 310 into direct current and supplies the direct
current to the DC bus 321.
[0072] The DC bus 321 supplies electric power to electric power
loads connected to the DC bus 321. Electric power loads using DC
power may be connected directly to the DC bus 321, and electric
power loads using AC power may be connected to the DC bus 321 via
DC/AC converters (341 to 343).
[0073] The electric power loads 361 to 363 of FIG. 3 are electric
power loads using AC power and are connected to the DC bus 321 via
the DC/AC converters 341 to 343, respectively. The DC/AC converters
341 to 343 convert direct current supplied from the DC bus 321 into
alternating current and supply the alternating current to the
electric power loads 361 to 363, respectively.
[0074] The electric power loads 361 to 363 may be draw-works motors
or top drive motors.
[0075] Although, in FIG. 3, three draw-works motors 361 to 363, as
the electric power loads, are shown as being connected to the DC
bus 321, it should be understood that the present invention is not
limited thereto and a varying number of draw-works motors and top
drive motors may be connected to the DC bus 321.
[0076] Since the draw-works motors 361 to 363 are configured to
repeatedly lift or lower drilling equipment such as a drill pipe, a
brake is frequently put on the motors to bring the motors to a
sudden stop or to rotate the motors in a reverse direction during
rotation at rated load.
[0077] The power storage units 371 to 373 receive electric power
from the DC bus 321 so as to store the electric power when a
voltage of the DC bus 321 is maintained at a first threshold value
or higher for a first period of time, and the power storage units
supply electric power to the DC bus 321 when the voltage of the DC
bus 321 is maintained at a second threshold value or less for a
second period of time. For example, assuming that the DC bus 321 is
a 720 V DC bus and is tripped at 750 V or higher, the first
threshold value may be set to 740 V.
[0078] The DC/DC converters 351 to 353 measure the voltage of the
DC bus 321, and supply electric power from the DC bus 321 to the
power storage units 371 to 373 such that the power storage units
371 to 373 store electric power when the voltage of the DC bus is
maintained at the first threshold value or higher for the first
period of time, whereas the DC/DC converters allow electric power
to flow from the power storage units 371 to 373 to the DC bus 321
to supply electric power from the power storage units 371 to 373 to
the DC bus 321 when the voltage of the DC bus is maintained at the
second threshold value or less for the second period of time.
[0079] When regenerative power is generated in the electric power
loads 361 to 363, the voltage of the DC bus 321 is increased, and,
when power consumption of the electric power loads 361 to 363 is
abruptly increased, the voltage of the DC bus 321 drops.
[0080] In other words, when regenerative power is generated in the
electric power loads 361 to 363 causing increase in the voltage of
the DC bus 321 and the voltage of the DC bus 321 is maintained at
the threshold value or higher for the first period of time, the
DC/DC converters 351 to 353 supply electric power to the power
storage units 371 to 373 such that the power storage units 371 to
373 store electric power, thereby allowing regenerative power
generated in the electric power loads 361 to 363 to be stored in
the power storage units 371 to 373.
[0081] When power consumption of the electric power loads 361 to
363 is abruptly increased causing drop in the voltage of the DC bus
321 and the voltage of the DC bus 321 is maintained at the second
threshold value or less for the second period of time, the DC/DC
converters 351 to 353 allow electric power to flow from the power
storage units 371 to 373 to the DC bus 321 such that the DC bus 321
receives electric power from the power storage units 371 to 373.
The power storage units 371 to 373 may be at least of an
ultracapacitor, a capacitor, a battery, and a flywheel.
Particularly, when the power storage units 371 to 373 are
ultracapacitors, it is possible to rapidly supply electric power to
the electric power loads 361 to 363 upon a sudden increase in power
consumption of the electric power loads 361 to 363 since such an
ultracapacitor has higher responsiveness than the power generator
310.
[0082] In addition, the power storage units 371 to 373 can supply
electric power to the DC bus 321 upon transients or loss of power.
When a sensor for detecting transients or loss of power 391 senses
a transient or loss of power and sends detection signals to the
DC/DC converters 351 to 353, the DC/DC converters 351 to 353 allow
electric power to be supplied from the power storage units 371 to
373 to the DC bus 321.
[0083] The sensor 391 may be mounted on at least one of a
switchboard and the DC bus 321.
[0084] Drilling equipment such as a draw-works and a top drive can
cause a dangerous situation upon abrupt interruption of power
supply. Thus, the power storage units 371 to 373 supply electric
power to the DC bus 321 upon transients or loss of power to safely
shut down the drilling equipment.
[0085] The resistors 381 to 383 consume electric power when the
voltage of the DC bus 321 is maintained at the first threshold
value or higher for a third period of time. Here, the third period
of time is longer than the first period of time.
[0086] When regenerative power is generated in the electric power
loads 361 to 363 causing increase in the voltage of the DC bus 321
and the voltage of the DC bus is maintained at the threshold value
or higher for the first period of time, the power storage units 371
to 373 store electric power. When the power storage units 371 to
373 are full, the voltage of the DC bus 321 does not drop and is
continuously maintained at the first threshold value or higher.
Thus, if the voltage of the DC bus 321 is maintained at the first
threshold value or higher for the third period of time, it can be
determined that the power storage units 371 to 373 are full. When
regenerative power is continuously generated even after the power
storage units 371 to 373 are full, the voltage of the DC bus 321
continuously increases, thereby causing the DC bus 321 to be
tripped. Thus, when the voltage of the DC bus 321 is maintained at
the first threshold value or higher for the third period of time,
the DC/DC converters 351 to 353 allow the resistors 381 to 383 to
consume electric power.
[0087] Although FIGS. 3 to 5 show three power storage units 371 to
373 and three resistors 381 to 383, it should be understood that
the present invention is not limited thereto and may include
varying numbers of power storage units and resistors.
[0088] As shown in FIG. 3, the power storage units 371 to 373 and
the corresponding resistors 381 to 383 may be connected to the DC
bus 321 in pairs. In other words, a first power storage unit 371
and a first resistor 381 are connected to the DC bus 321 via a
first DC/DC converter 351; a second power storage unit 372 and a
second resistor 382 are connected to the DC bus 321 via a second
DC/DC converter 352; and a third power storage unit 373 and a third
resistor 383 are connected to the DC bus 321 via a third DC/DC
converter 353. When the power storage unit and the resistor are
connected to the same DC/DC converter, as in FIG. 3, it is possible
to reduce the number of required DC/DC converters and the overall
size of the apparatus.
[0089] Alternatively, the plural power storage units 371 to 373 and
the plural resistors 381 to 383 may be connected to the DC bus 321
via separate DC/DC converters 451 to 456, respectively, as shown in
FIG. 4. In other words, a first power storage unit 371 is connected
to the DC bus 321 via a first DC/DC converter 451; a second power
storage unit 372 is connected to the DC bus 321 via a second DC/DC
converter 452; a third power storage unit 373 is connected to the
DC bus 321 via a third DC/DC converter 453; a first resistor 381 is
connected to the DC bus 321 via a fourth DC/DC converter 454; a
second resistor 382 is connected to the DC bus 321 via a fifth
DC/DC converter 455; and a third resistor 383 is connected to the
DC bus 321 via a sixth DC/DC converter 456. When the plural power
storage units 371 to 373 and the plural resistors 381 to 383 are
connected to separate DC/DC converters 451 to 456, respectively, as
in FIG. 4, it is possible to operate the plural power storage units
371 to 373 and the plural resistors 381 to 383 in an individual
manner.
[0090] Alternatively, a single power storage unit 371 to 373 and a
single resistor 381 to 383 may be dedicated to a single electric
power load 361 to 363, as shown in FIG. 5. In other words, when
regenerative power is generated in a first electric power load 361,
a first power storage unit 371 stores the regenerative power and a
first resistor 381 does not consume electric power until the first
power storage unit 371 is full. When regenerative power is
generated in a second electric power load 362, a second power
storage unit 372 stores the regenerative power and a second
resistor 382 does not consume electric power until the second power
storage unit 372 is full. When regenerative power is generated in a
third electric power load 363, a third power storage unit 373
stores the regenerative power and a third resistor 383 does not
consume electric power until the third power storage unit 372 is
full.
[0091] When regenerative power is generated in the first electric
power load 361, a first DC/AC converter 341 detects generation of
regenerative power in the first electric power load 361 and sends a
control signal to the first DC/DC converter 351. In response to the
control signal, the first DC/DC converter 351 allows electric power
to be supplied from the DC bus 321 to the first power storage unit
371 such that the first power storage unit 371 can store electric
power. Then, the first DC/DC converter 351 detects whether the
first power storage unit 371 is full, and, when the first power
storage unit 371 is full, the first DC/DC converter allows the
first resistor 381 to consume electric power. Although the first
power storage unit 371 and the first resistor 381 are shown as
being connected to the same DC/DC converter 351, it should be
understood that the first power storage unit 371 and the first
resistor 381 may be connected to different DC/DC converters.
[0092] Next, a hybrid power supply method for an offshore plant
according to an embodiment of the present invention will be
described with reference to FIGS. 6 to 8. FIG. 6 is a flowchart of
a process of supplying electric power to a power storage unit in a
hybrid power supply method for an offshore plant according to an
embodiment of the present invention, FIG. 7 is a flowchart of a
process of supplying electric power from the power storage unit to
a DC bus upon power shortage in the hybrid power supply method for
an offshore plant according to the embodiment of the present
invention, and FIG. 8 is a flowchart of a process of supplying
electric power from the power storage unit to the DC bus upon loss
of power in the hybrid power supply method for an offshore plant
according to the embodiment of the invention.
[0093] Referring to FIG. 6, voltage of a DC bus is measured (S610);
electric power is stored in a power storage unit when the voltage
of the DC bus 321 is maintained at a first threshold value or
higher for a first period of time (S620); and electric power is
consumed by a resistor when the voltage of the DC bus 321 is
maintained at the first threshold value or higher for a second
period of time (S630).
[0094] Referring to FIG. 7, the voltage of the DC bus is measured
(S710); and electric power stored in the power storage unit is
supplied to the DC bus when the voltage of the DC bus is maintained
at a second threshold value or less for a third period of time
(S720).
[0095] When a sensor 391 detects loss of power (S810), the sensor
391 sends a control signal to a DC/DC converter (S820), and the
DC/DC converter allows the power storage unit to supply electric
power to the DC bus in response to the control signal from the
sensor 391 (S830).
[0096] Next, power consumption of each component of the power
supply apparatus according to the embodiments of the invention will
be described with reference to FIG. 9. FIG. 9 is a graph showing
power consumption of each component of the power supply apparatus
according to the embodiments of the invention.
[0097] As shown in FIG. 9, it can be seen that, when regenerative
power is generated in the electric power load, the power storage
unit stores the generated regenerative power, and, when power
consumption of the electric power load is suddenly increased, the
power storage unit supplies electric power to the electric power
load, thereby maintaining power output of the power generator at a
constant level.
[0098] Although some embodiments have been described herein, it
should be understood by those skilled in the art that these
embodiments are given by way of illustration only, and that various
modifications, variations and alterations can be made without
departing from the spirit and scope of the invention. Therefore,
the embodiments disclosed herein should not be construed as
limiting the technical scope of the present invention, but should
be construed as illustrating the idea of the present invention. The
scope of the present invention should be interpreted according to
the appended claims as covering all modifications or variations
derived from the appended claims and equivalents thereof.
* * * * *