NL2035105B1 - Crane electrical load stabilisation - Google Patents
Crane electrical load stabilisation Download PDFInfo
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- NL2035105B1 NL2035105B1 NL2035105A NL2035105A NL2035105B1 NL 2035105 B1 NL2035105 B1 NL 2035105B1 NL 2035105 A NL2035105 A NL 2035105A NL 2035105 A NL2035105 A NL 2035105A NL 2035105 B1 NL2035105 B1 NL 2035105B1
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- power
- flywheel
- power consumption
- power supply
- setpoint
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- 230000006641 stabilisation Effects 0.000 title description 2
- 238000000034 method Methods 0.000 claims description 7
- 230000001965 increasing effect Effects 0.000 claims description 5
- 238000012935 Averaging Methods 0.000 claims description 4
- 230000003247 decreasing effect Effects 0.000 claims description 4
- 230000001276 controlling effect Effects 0.000 claims 9
- 238000010521 absorption reaction Methods 0.000 claims 2
- 230000000087 stabilizing effect Effects 0.000 claims 2
- 230000001105 regulatory effect Effects 0.000 claims 1
- 238000005259 measurement Methods 0.000 description 18
- 230000007423 decrease Effects 0.000 description 8
- 238000006243 chemical reaction Methods 0.000 description 6
- 230000008929 regeneration Effects 0.000 description 6
- 238000011069 regeneration method Methods 0.000 description 6
- 239000003990 capacitor Substances 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- 238000005461 lubrication Methods 0.000 description 4
- 230000002829 reductive effect Effects 0.000 description 4
- 238000004088 simulation Methods 0.000 description 4
- 230000002457 bidirectional effect Effects 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 238000007599 discharging Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000004146 energy storage Methods 0.000 description 3
- 230000003019 stabilising effect Effects 0.000 description 3
- 230000009471 action Effects 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 239000000523 sample Substances 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 238000011217 control strategy Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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- 238000005381 potential energy Methods 0.000 description 1
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- 230000036962 time dependent Effects 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B66—HOISTING; LIFTING; HAULING
- B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
- B66C13/00—Other constructional features or details
- B66C13/12—Arrangements of means for transmitting pneumatic, hydraulic, or electric power to movable parts of devices
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B66—HOISTING; LIFTING; HAULING
- B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
- B66C13/00—Other constructional features or details
- B66C13/18—Control systems or devices
- B66C13/22—Control systems or devices for electric drives
- B66C13/23—Circuits for controlling the lowering of the load
- B66C13/26—Circuits for controlling the lowering of the load by AC motors
- B66C13/28—Circuits for controlling the lowering of the load by AC motors utilising regenerative braking for controlling descent of heavy loads and having means for preventing rotation of motor in the hoisting direction when load is released
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J15/00—Systems for storing electric energy
- H02J15/007—Systems for storing electric energy involving storage in the form of mechanical energy, e.g. fly-wheels
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for AC mains or AC distribution networks
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
- H02J3/30—Arrangements for balancing of the load in a network by storage of energy using dynamo-electric machines coupled to flywheels
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Mechanical Engineering (AREA)
- Automation & Control Theory (AREA)
- Control And Safety Of Cranes (AREA)
Abstract
_ 22 _ ABSTRACT A crane system is configured to carry a load and comprises an electric motor, a mains power supply connection, a flywheel configured to store energy, the mains power supply connection 5 being connected to the motor and to the flywheel, and a controller. The controller is configured to: - determine a mains power consumption setpoint; - measure a mains power consumption at the mains power supply connection, being a sum of power consumptions by the crane and the flywheel; 10 - control the flywheel to regulate the mains power consumption to the mains power consumption setpoint, and - derive a reactive power from the measured power supply voltage and the measured power supply current, and control a reactive power compensation device to at least partly compensate the reactive power. 15 Fig. 3
Description
P35987NL00
Title: Crane electrical load stabilisation
The present invention relates to a crane system configured to carry a load, to a method of stabilising a power consumption of a crane, and to a use of a flywheel energy storage system.
Chinese patent application CN110098629A discloses a system using flywheel battery and chemical battery energy storage for harbour crane brake energy regeneration, and is applied to the occasion of harbour crane brake energy regeneration. The system comprises a crane frequency converter DC bus, an electric energy storing flywheel battery control unit, an electric energy storing chemical battery control unit and a main control system; the main control system is used to monitor the work state of a crane and controls the flywheel battery control unit and the chemical battery control unit; the crane frequency converter DC bus transmits a control signal to the main control system; and the main control system receives the control signal transmitted by the crane frequency converter DC bus, and controls the flywheel battery control unit and the chemical battery control unit. The system realize energy storage and frequency modulation by control of the flywheel battery control unit and the chemical battery control unit by the control system, electric energy generated by braking is stored and used to supplement electric energy in the hoisting process, and a reversible energy conversion process is realized.
When lowering the load, the crane, more specifically an electric motor of the crane, may act as a generator and may correspondingly regenerate electrical energy.
Harbour cranes may be used to carry heavy loads, such as ISO containers. In order to carry such heavy loads, a high power electrical motor may be required which high power electrical motor may require a power source with a high output power, such as a mains connection or diesel generator, in order to satisfy power needs of the harbour crane.
The invention aims to facilitate a powering of a crane, such as a harbour crane.
According to an aspect of the invention, there is provided a crane system comprising a crane configured to carry a load, a power supply connection configured to receive power from a power supply, the power supply connection being connected to the crane,
a flywheel configured to store energy, the power supply connection being further connected to the flywheel, and a controller for controlling the flywheel, wherein the controller is configured to: - determine a power consumption setpoint defining a setpoint of a power consumption from the power supply at the power supply connection; - measure a power supply voltage and a power supply current at the power supply connection and determine the power consumption at the power supply connection from the measured power supply voltage and power supply current, the power consumption being a sum of power consumptions by the crane and the flywheel; - control the flywheel to regulate the power consumption at the power supply connection according to the power consumption setpoint, and - wherein the crane system further comprises a reactive power compensation device, and wherein the controller is further configured to derive a reactive power at the power supply connection from the measured power supply voltage and the measured power supply current, and to control the reactive power compensation device to at least partly compensate the reactive power.
Harbour cranes tend to be used to raise and lower loads. When raising a load, energy is consumed, while when lowering the load, or braking the load, part of the consumed energy is recuperated and may be stored in a buffer such as a battery or flywheel. When raising the load or another load, the recuperated energy may be drawn from the buffer and used to reduce a power demand from a power supply, such as an electrical mains or a diesel powered electrical generator. The recuperation may provide some degree of energy saving, as recuperated energy would otherwise have been dissipated.
The inventors of the present patent application have realised that, although the recuperation of energy and storage thereof in a buffer may provide some saving of energy, and may reduce a peak power demand from the power supply, overall requirements on the power supply of the harbour crane remain high. For example, a high power electrical generator, such as a diesel powered generator, would be required in order to generate sufficient electrical power to power the harbour crane.
The inventors have accordingly employed a control strategy which may enable to power the (harbour) crane with lower requirements on the power supply.
A flywheel is connected to the power supply connection which establishes an electrical connection with the power supply, such as a mains, e.g. a three phase AC mains or a generator, such as a diesel-powered generator. The flywheel is configured to store kinetic energy by rotation of a rotatable wheel of the flywheel. The flywheel comprises an electric motor configured to drive the rotatable wheel of the flywheel. Powering the electric motor may accelerate the rotatable wheel of the flywheel thereby increasing a flywheel velocity. Hence, electrical energy consumed by the electric motor is at least partly converted into kinetic energy.
The flywheel further comprises a generator driven by the rotatable wheel of the flywheel, the generator configured to generate electrical power. As the generator is driven by the rotatable wheel of the flywheel, the generator generates electrical energy, while the load of the generator reduces a velocity of the rotatable wheel of the flywheel. Hence, kinetic energy consumed by the generator is at least partly converted into electrical energy. Thus, the flywheel may be used as a bidirectional conversion and storage, whereby electrical energy may be converted into kinetic energy and vice versa, and whereby kinetic energy is stored by rotation of the rotatable wheel at a substantially constant velocity. In an embodiment, the electric motor and the generator may be integral, i.e. the electric motor may act as a generator. In another embodiment, the flywheel may comprise an electric motor and a generator, both connected to the rotatable wheel of the flywheel.
According to an aspect of the invention, a power consumption setpoint is determined. The power consumption setpoint defines a setpoint power drawn at the power supply connection.
The mains power consumption setpoint may define an amplitude and phase of the setpoint power. The power consumption setpoint defines a value of the electrical power which is desired to be drawn from the power supply, such as the mains power network, at a substantially constant rate, e.g. at a substantially constant current.
The power supply may be an alternating current, AC, power supply. Accordingly, the power supply voltage may be an AC voltage and the current drawn from the power supply may be an
AC current. When referring to a magnitude of a voltage or current, or when referring to a comparison of currents, in the case of AC voltages and/or currents, this is to be understood as a comparison of a time average or an effective value of the voltages respectively the currents.
The time average may be a time average over a repetition period of the AC voltage respectively current. For example, the power supply may be a mains power supply, i.e. a mains power grid.
As another example, the power supply may be a generator, such as a diesel powered generator, a hydrogen powered generator, etc.
The crane system comprises a controller which controls the flywheel. Thereto, the controller determines the power consumption at the power supply connection. For example, the controller may comprise a power measurement device connected to the power supply connection and configured to measure the power supply current and the power supply voltage and to determine the power consumption on the basis of the measured power supply current and power supply voltage. As both the crane and the flywheel are powered via the mains power connection, the power consumption is a sum of power consumptions by the crane and by the flywheel. The controller controls the flywheel to regulate the power consumption at the power supply connection, i.e. the sum of power consumptions by the crane and by the flywheel, to the setpoint. A feedback loop is formed as the charging or discharging by the flywheel affects the power consumption, namely by the power consumed by or recuperated from the flywheel.
Thus, the power drawn from the power supply is formed by a resulting net contribution from the power consumed by(or possible recuperated by) the crane and the power consumed by or recuperated by the flywheel. As the feedback controller seeks to control the flywheel to regulate the power drawn from the power supply to the setpoint SET, i.e. the setpoint power consumption from the power supply, the feedback controller seeks to control the flywheel to retain the overall power consumption from the power supply, at the value determined by the setpoint SET. As a result, changes in the power drawn by the crane will at least partly be compensated by the flywheel, as the feedback controller drives the flywheel to keep the overall power consumption at the setpoint value. Thus, as the power drawn by the crane increases, the power drawn by the flywheel will decrease or even change into a recuperation of power, to retain the overall net power consumption in accordance with the setpoint value determined by setpoint SET. Likewise, as the power drawn by the crane decreases or even changes into a regeneration e.g. by a lowering of the load by the crane, the power drawn by the flywheel will increase, to retain the overall net power consumption in accordance with the setpoint value determined by setpoint SET.
An operation of the electric motor and/or other electric systems of the crane may result in a generation of reactive power, i.e. a current that is not in phase with the power supply voltage of the power supply. The reactive power may be generated by the electric motor of the crane and/or other electric systems of the crane and may form a load of the power supply. Reactive power may be generated by the electric motor of the crane under various circumstances, such as for example a low load condition of the crane, a regeneration of energy by lowering the load,
etc. The controller is configured to determine a reactive power at the power supply connection from the measured power supply voltage and power supply current. The reactive power may be determined from a phase relation between the power supply voltage and the power supply current. The controller may be configured to drive the reactive power compensation device to at least partly compensate the reactive power.
The reactive power compensation device may comprise a capacitive load and/or an inductive load. For example, the reactive power compensation device comprises a plurality of capacitors and switches to connect the capacitors to the power supply connection. Depending on an amount of reactive power, the control device may control the switches to connect at least one of the capacitors to the power supply connection. Similarly, the reactive power compensation device comprises a plurality of inductors and switches to connect the inductors to the power supply connection. Depending on an amount of reactive power, the control device may control the switches to connect at least one of the inductors to the power supply connection.
As another example, the power reactive power compensation device may comprise a converter, such as a bi-directional AC/DC converter which converts AC (Alternating Current) at the power supply connection into DC (Direct Current) at a DC bus and vice versa. The electric motor/generator of the flywheel, which is configured to convert electrical energy into kinetic energy of the rotating mass of the flywheel and vice versa , may for example be driven via a bi- directional DC/AC converter which is connected to the DC bus and configured to convert the
DC at the DC bus into AC for powering the electric motor of the flywheel, and vice versa. The
AC/DC converter that connects between the DC bus and the power supply connection may be configured to compensate reactive power. The converter is connected to the controller and configured to be driven by the controller to provide a compensating reactive power to at least partly compensate the reactive power generated by the crane.
The controller may drive the flywheel as follows: In case the controller has determined that the power consumption exceeds the power consumption setpoint, the controller drives the flywheel to decrease the flywheel velocity. Thus, the flywheel is driven to recuperate energy, whereby a power need from the power supply is decreased. As a result, the power supply current (which includes the current consumed by the flywheel or in the present case recuperated from the flywheel) may decrease. In case the controller has determined from the comparison that the power supply consumption is below the power consumption setpoint, the controller drives the flywheel to increase the flywheel velocity. As a result, the power supply current {which includes the current consumed by the flywheel or recuperated from the flywheel) may increase.
Thus, a closed loop feedback may be created, whereby the power drawn from the power supply is measured, compared to a setpoint and the flywheel is controlled to consume energy in case the current drawn from the power supply is below the setpoint and to recuperate energy in case the current drawn from the power supply is above the setpoint.
In an embodiment, the controller being configured to derive a flywheel power consumption setpoint from the power consumption and the power consumption setpoint and to drive the flywheel in accordance with the flywheel power consumption setpoint. The flywheel power consumption setpoint may enable to interface with an existing flywheel, which may be driven on the basis of a flywheel power consumption setpoint.
For example, the flywheel power consumption setpoint expresses a setpoint of power delivered to or by the flywheel. Thus, in case the setpoint would be zero, the flywheel maintains a substantially constant velocity, thus storing a substantially constant amount of energy. A positive of negative value of the setpoint may define an amount of power to be drawn from or absorbed by the flywheel. For example, the flywheel power consumption setpoint may be proportional to a power to be drawn from the flywheel respectively stored by the flywheel. The controller may generate the flywheel power consumption setpoint from the power consumption and the power consumption setpoint in any suitable way. In particular, the controller may comprise a Proportional, P, a Proportional Integrating, PI, a Proportional Differentiating, PD, or a Proportional Integrating Differentiating, PID, control unit to provide a desired closed loop behaviour, or a feed forward control, enabling to drive the flywheel to quickly and accurately obtain a desired closed loop, i.e. feedback loop, behaviour. Thus, the resulting current, i.e. the resulting power consumption drawn from the mains, may be maintained closely to the power consumption setpoint, this being able to take account of dynamic changes in load of the crane in an effective way.
The power consumption setpoint may be determined in various ways. In an embodiment, the controller is configured to determine the power consumption setpoint from a time averaged power consumption of the crane. The time averaging may be performed over at least one load cycle of the crane. A load cycle may be understood as a cycle of raising and lowering a load by the crane. Thereto, the power consumption of the crane may be measured, possibly including regeneration of energy by lowering of the load by the crane, and averaged over the at least one load cycle.
For example, the time averaged power consumption of the crane may comprise a time averaged expected power consumption of the crane, thus providing a suitable value for the setpoint before having raised the load. For example, the expected power consumption may be simulated taking account of load weight, load raising and lowering velocity, load lifting range, electric motor efficiency, etc.
As a further example, the time averaged power consumption of the crane may comprise a time averaged measured power consumption of the crane. An accurate determination of power consumption may be performed on the basis of power consumption measurements. A combination of estimation (simulation) with measurements may be used, for example using measurements of power consumption to adjust one or more parameters in a simulation model, thus enabling to enhance an accuracy of the simulation model.
A total amount of energy stored by the flywheel may be defined as a state of charge of the flywheel. The state of charge of the flywheel may be limited in range. For example a maximum state of charge may be set by a maximum safe operating velocity (i.e. rotational velocity) of a rotor of the flywheel. The maximum state of charge may be limited by safety constraints and/or lifetime constraints to avoid e.g. disproportional wear or overload of e.g. a bearing of the rotatable rotor of the flywheel. A minimum state of charge may be determined by a minimum rotational velocity of the rotor of the flywheel. The minimum rotational velocity may for example be set to maintain some margin from a standstill of the rotatable rotor of the flywheel, being a zero stored energy condition. In an embodiment, the controller is configured to adjust the power consumption setpoint as a function of a state of charge of the flywheel. In particular, at a high or low state of charge of the flywheel, the power consumption setpoint may be adjusted, e.g. for safety reasons or to prevent the flywheel from gradually running out of its intended operating range between a minimum state of charge and a maximum state of charge.
For example, the controller may be configured to decrease the power consumption setpoint in case the state of charge of the flywheel is above a maximum state of charge threshold. For example, the power consumption setpoint is decreased proportionally to an excess of the state of charge above the maximum state of charge threshold. Thereby, the state of charge may be brought back into the desired operating range in a controlled way.
Similarly, as a further example, the controller may be configured to increase the power consumption setpoint in case the state of charge of the flywheel is below a minimum state of charge threshold. For example, the power consumption setpoint is increased proportionally to an excess of the state of charge below the minimum state of charge threshold.
In an embodiment, the flywheel is connected in parallel to the power supply connection. The electric motor of the crane may be connected to the power supply connection by a suitable converter such as an Alternating Current/Direct Current, AC/DC, and a Direct
Current/Alternating Current, DC/AC, converter. The flywheel may likewise be connected to the power supply by a suitable converter such as an Alternating Current/Direct Current, AC/DC, and a Direct Current/Alternating Current, DC/AC, converter. By connecting both the electric motor of the crane and the flywheel in parallel, via their respective converters, to the mains, a relatively easy retrofitting may be accomplished in that existing driving electronics of the crane may not require further modification.
In order to obtain an accurate measurement of the power consumption, in an embodiment, the power supply connection comprises a power supply current measurement device to measure the power supply current and wherein the controller is connected to the power supply current measurement device to receive a signal representative of the measured power supply current.
The crane may be driven by a crane controller, which may be responsive to load setpoint defining a desired operation of the crane. The load setpoint may for example define a raising, lowering, etc. by the crane. For example, the load setpoint forms a setpoint trajectory determining a load cycle of the crane. The power consumption setpoint may be based on the load setpoint, thus taking account of a setpoint trajectory of the crane. Accordingly, in an embodiment, the controller may be configured to determine the power consumption setpoint from a load setpoint of the electric motor. For example, the controller may be configured to time average the load setpoint of the electric motor (i.e. the load setpoint of the crane) and to determine the power consumption setpoint from the time averaged load setpoint of the electric motor.
In an embodiment, the flywheel comprises a converter configured to convert AC electrical power into DC electrical power at a DC power bus, and vice versa. An AC to DC and DC to
AC conversion may be used to be able to convert an AC power at an AC frequency of the power supply, e.g. the mains power, into an AC drive of the flywheel at a frequency associated with an operational condition of the flywheel.
In an embodiment, the power supply is a mains power supply. In an embodiment, a maximum value of the flywheel power consumption setpoint is in a range of 0,003 MW to 2 MW per flywheel. Accordingly, a maximum of the power absorbed by the flywheel or recuperated from the flywheel is 0,003 MW to 2 MW per flywheel.
According to a further aspect of the invention, there is provided a method of stabilising a power consumption of a crane connected by a power supply connection to a power supply, the method comprising: - connecting a flywheel to the power supply connection, - determining a power consumption setpoint defining a setpoint of a power consumption from the power supply at the power supply connection; - measuring a power supply voltage and a power supply current at the power supply connection and determining the power consumption at the power supply connection from the measured power supply voltage and power supply current, the power consumption being a sum of power consumptions by the crane and the flywheel; - controlling the flywheel to regulate the power consumption at the power supply connection according to the power consumption setpoint, and - deriving a reactive power at the power supply connection from the measured power supply voltage and the measured power supply current, and controlling a reactive power compensation device to at least partly compensate the reactive power.
According to a yet further aspect of the invention, there is provided a use of a flywheel configured to store energy, the flywheel being connected to a power supply connection to exchange electrical energy with the flywheel, and a controller for controlling the flywheel, wherein the controller is configured to: - determine a power consumption setpoint defining a setpoint of the power consumption from the power supply at the power supply connection; - measure a power supply voltage and a power supply current at the power supply connection and determine the power consumption at the power supply connection from the measured power supply voltage and power supply current, the power consumption being a sum of power consumptions by the crane and the flywheel; - control the flywheel to regulate the power consumption at the power supply connection according to the power consumption setpoint, and derive a reactive power at the power supply connection from the measured power supply voltage and the measured power supply current, and control a reactive power compensation device to at least partly compensate the reactive power,
for stabilising a power consumption of a crane connected to the power supply connection.
A peak load on the mains power network or other power supply may be significantly reduced by the present invention, as during a peak load by the crane, the flywheel is used to recuperate energy, thus to reduce a load on the mains power network or other power supply. During a remainder of the load cycle, the flywheel is used to store energy. A power consumption from the power supply may be kept at a substantially constant level over a load cycle of the crane:
The power consumption may be kept constant at a level equal to an average, effective power consumption of the crane over the load cycle time. Effectively, during peak load of the crane, e.g. during raising the load, the crane may demand power in excess of the average power consumption, which power in excess of the average power consumption is drawn from the flywheel. During a remainder of the load cycle, the crane may demand power lower than the average power consumption, a difference between the power drawn by the crane and the power drawn from the power supply is stored in the flywheel. A peak load on the power supply may be significantly reduced, enabling to make use of a smaller power supply connection. The inventors have found that, by the present invention, a peak power demand may be reduced by e.g. a factor of 3 — 5, or even by a factor of 5 — 10 in case of intermittent use with time between successive operations by the crane and with variation in crane load.
Further features, advantages and effects of the invention may follow from the enclosed drawing and below description, depicting and describing non-limiting embodiments, wherein: - Figure 1 depicts a schematic view of a flywheel; - Figure 2 depicts a schematic view of a crane system comprising a flywheel; - Figure 3 depicts a control diagram; - Figure 4 depicts load cycle of the crane and the flywheel; - Figure 5 depicts a resulting load on the power supply; and - Figure 6 depicts a power consumption setpoint as a function of a state of charge of the flywheel
Throughout the figures, the same or similar items are indicated by the same or similar reference numerals.
Figure 1 depicts a perspective view of a flywheel. The flywheel comprises the following parts:
A drive unit provides for a control and monitoring of a power flow between infeed and motor, converting energy measurement to a torque setpoint for the motor.
An electric motor EMR. The motor converts electrical power to kinetic energy. Motor, axis, and bearing may be monitored with vibration and temperature sensors.
A storage control cabinet. The storage control cabinet may contain all control elements such as a PLC, a Human Machine Interface HMI and a low voltage power distribution.
A lubrication system LUB which may be used to lubricate a rotor and axis of the flywheel. The lubrication system may also be used for cooling purposes.
A vacuum system VAC, which may be used to generate a vacuum or a low pressure environment in the housing so to reduce air friction for the rotating rotor.
A rotor RTR and rotor casing; The rotor is rotatable about the axis and used to store kinetic energy by rotation of the rotor about the axis
An amount of kinetic energy stored by the flywheel may be determined by a mass and diameter of the rotor, as well as by its rotational velocity. The higher a rotational velocity of the rotor, the more kinetic energy is stored.
As the motor is powered to drive the rotor, the rotor accelerates causing an increase in kinetic energy stored by the flywheel, thereby converting electric energy provided to the motor into kinetic energy. Further, the motor may be used to convert kinetic energy into electric energy as follows: mechanically loading the rotor by the flywheel may reduce a rotational velocity of the flywheel, while the motor is used as a generator to generate electrical power. Thus, kinetic energy is converted into electric energy. The motor is controlled by the drive unit to form a load on the rotor of the flywheel to convert kinetic energy into electric energy, to accelerate the flywheel, i.e. increase a rotational speed of the rotor to convert electric energy into kinetic energy, or to remain in a rest state, whereby no energy is exchanged, i.e. the flywheel is neither accelerated nor decelerated, hence maintains at substantially a same level of kinetic energy. A conversion efficiency from electric energy to kinetic energy and from kinetic energy to electric energy may largely be determined by an efficiency of the electric motor as a motor in the case of accelerating the flywheel and as a generator in the case of decelerating the flywheel. As an efficiency of an electric motor and generator is generally relatively large, the conversion efficiency may in general be high. The flywheel may thus be used to absorb, to store and to recuperate energy. Losses of stored kinetic energy, i.e. dissipation of stored energy, may be minimized by the vacuum system which may reduce friction by the rotating rotor in respect of air, and by a suitable lubrication of the rotor about the axis of the flywheel.
Figure 2 depicts a crane system which comprises a crane CR, such as a harbour crane and a flywheel FL. The crane is connected to a power supply connection, such as in the present example a mains power supply connection MPC configured to be connected to a power supply such as in the present example an electric mains power supply MPS, such as an AC mains.
The flywheel is likewise connected to the mains power supply connection, in the present example via the converter CNV and blind current compensation device BCC. The converter
CNV may for example comprise a bidirectional AC/DC converter to convert AC at the power supply into DC at a DC bus and a bidirectional DC/AC converter to convert DC at the DC bus into an AC drive of the motor/generator connected to the rotating mass of the flywheel.
Thus, both the crane and the flywheel are powered from a same power source, i.e. a same power supply. Although in Figure 2 the crane CR and the flywheel are connected to the mains power supply, such as the AC mains, at a single, i.e. same connection, it may also be understood that dual, parallel connections are used to connected the crane respectively the flywheel to the mains power supply. At the mains power supply connection, a current measurement device CMD is arranged, such as a current probe, e.g. a magnetic probe, which provides a measurement signal representative of a current through the mains power supply connection. Similarly, a voltage measurement device VMD is arranged at the mains power supply connection to measure the mains power supply voltage. In case of a 3 phase power supply, 3 current measurement signals may be provided, one per phase, representing the respective currents at the 3 phases. Similarly, 3 voltage measurement signals represent the respective voltages at the 3 phases.
The signal(s) representative of the current are provided to a controller CTR, which controller controls the flywheel FL. The controller is further configured to generate a setpoint signal, the setpoint signal is formed by a setpoint power consumption from the mains at the mains power supply connection. Thus the setpoint signal defines a setpoint of the power consumption from the mains power supply. The setpoint is preferably formed by a value which is constant in time, e.g. constant over a load cycle of the crane. The load cycle of the crane may be defined as a trajectory of the load of the crane over a cycle of raising and lowering a load LD. The raising of the load may be associated with an increase in power consumption by the crane and the lowering of the load may be associated with a reduction in the power consumption of the crane, the reduction e.g. due to recuperation of energy as the load is lowered, recuperating potential energy by lowering a mass of the load carried by the crane.
Figure 3 depicts a control diagram of the controller based on which a control of the flywheel will be explained.
As depicted in Figure 3, and as explained above with reference to Figure 2, the current measurement device CMD measures a current at the mains power supply connection, i.e. measures a current drawn from, respectively delivered to, the mains power supply MPC. The power supply current may for example be a three phase current. Similarly, the voltage at the mains power supply connection MPC is measured by the voltage measurement device VMD. A signal representative of the measured current and a signal representative of the measured voltage are provided to a power measurement unit which determines a power consumption at the mains power supply connection from the measured voltage and current. A grid power signal which represents the mains power consumption, is output by GP on the basis of the determined power consumption.
A state of charge of the flywheel is derived at SOC, the state of charge representing an energy stored by the flywheel. The energy stored by the flywheel may be dependent on a mass and dimensions of the flywheel as well as on a rotational velocity of the flywheel. As, for a given flywheel, the mass and dimensions may be constant, the state of charge may largely depend on the rotational velocity of the flywheel, hence may e.g. be derived from a signal representing a rotational velocity of the flywheel. The state of charge may be output to a state of charge to grid power conversion SPC which generates a grid power setpoint from the determined state of charge. The grid power setpoint is output at SET.
A feedback controller FB is provided with the grid power setpoint at one input thereof. The feedback controller is further provided with the measured grid power GP at another input thereof. The feedback controller may form a proportional regulator, and may optionally comprise integrating (I) and/or differentiating (D), thus may comprise e.g. a P, PI, PD, or a PID regulator.
The feedback controller FB provides, via a switch SWP, a controller output signal to the flywheel, the controller output signal forming a flywheel power consumption setpoint FLS. The flywheel is accordingly driven at the flywheel power consumption setpoint. The flywheel is driven according to a positive or negative sign of the setpoint to absorb, i.e. store, energy or to recuperate energy. A zero value of the flywheel power consumption setpoint provides that the flywheel maintains a same state of charge, i.e. maintains at a same level of energy without charging or discharging.
The switch SWP may disconnect the regulator output signal from the flywheel power consumption setpoint, e.g. for safety reasons or during start-up or power down of the flywheel, in case of an error, etc.
A feedback loop is formed as the charging or discharging by the flywheel affects the mains power supply current namely by the current drawn by or recuperated from the flywheel. Thus, the current drawn from the mains power supply is formed by a resulting current from the current consumed by (or possibly recuperated by) the crane and the current consumed by or recuperated by the flywheel. As the feedback controller seeks to control the flywheel to regulate the current drawn from the mains power supply to the setpoint SET, i.e. the setpoint power consumption from the mains power supply, the feedback controller seeks to control the flywheel to retain the overall current consumption from the mains power supply, i.e. the overall power consumption from the mains power supply, at the value determined by the setpoint SET. As a result, changes in the power drawn by the crane will at least partly be compensated by the flywheel, as the feedback controller drives the flywheel to keep the overall power consumption at the setpoint value. Thus, as the power drawn by the crane increases, the power drawn by the flywheel will decrease or even change into a recuperation of power, to retain the overall net power consumption in accordance with the setpoint value determined by setpoint SET.
Likewise, as the power drawn by the crane decreases or even changes into a regeneration e.g. by a lowering of the load by the crane, the power drawn by the flywheel will increase, to retain the overall net power consumption in accordance with the setpoint value determined by setpoint SET.
A large range of control may be provided, as a level of power absorbed by or regained from the flywheel may extend over a wide range. As a result, substantial changes in operating conditions of the crane (weight of load, velocity of lifting or lowering the load, etc.) may be accommodated by the flywheel. Moreover, a dynamic response of the flywheel to changes in the flywheel setpoint may be fast, enabling the flywheel to relatively quickly respond to dynamics in the load conditions by the crane.
The feedback controller may further enhance dynamics, i.e. high frequency performance, by providing a differentiating action in the feedback controller. Static, low frequency, performance may be enhanced by providing an integrating action in the feedback controller.
The controller may further be configured to control a variety of variables such as flywheel torque, flywheel vacuum, flywheel oil supply (lubrication), flywheel oil cooling, etc.
Figure 4 depicts an example of a load cycle of the crane, illustrating a power consumption of the crane versus time, whereby the crane alternatingly raises and lowers loads, resulting in a periodic change of power consumption by the crane. As a result, the power consumption by the crane from the mains power supply may exhibit a similar pattern.
Figure 4 further depicts a state of charge SOC of the flywheel, a mains power consumption before compensation MPNC, and a mains power consumption after compensation MPWC. The mains power consumption before compensation and the mains power consumption after compensation are both expressed in terms of apparent power. As can be seen in Figure 4, over time, the state of charge of the flywheel increases, whereby power is absorbed by the flywheel, and decreases, whereby power is drawn from the flywheel. The power consumption after compensation, i.e. in accordance with the invention, is more constant as compared to the power consumption before compensation.
Figure 5 depicts a net result of the compensation of the load cycle by the flywheel. The changes over time in the power consumption of the crane are at least partly compensated by the power drawn by and delivered by the flywheel and the reactive power is at least partly compensated by the converter CNV. As a result, a net effective load on the mains power supply is substantially constant. A power factor after compensation is depicted at PFC. Reactive power at the power supply connection, after compensation, is depicted by the uninterrupted line
RPWC.
The setpoint SET of the feedback controller may be determined from a power consumption of the crane over a time period, such as a load cycle or plural load cycles of the crane. The (time dependent) power consumption may be averaged over the time period, to arrive at a desired, effective power consumption. Assuming a certain mains power supply voltage, independent from mains power current drawn from the mains power supply, the averaging may be performed on the power consumption or on the current consumption, as they are directly related one to the other. The time averaging may be performed on a measured consumption by the crane at an operation of the crane or on a simulated consumption derived from a simulation of an operation of the crane.
The determining the setpoint SET according to the time averaged power consumption of the crane may enable to keep a state of charge of the flywheel at a level around a predetermined level, thus largely avoiding a drift of the state of charge over time away from the predetermined level. For example, the predetermined state of charge of the flywheel is between 10% and 90% of a maximum state of charge, i.e. 10% to 90% of a maximum of kinetic energy to be stored in the flywheel.
As the actual power consumption over time may differ somewhat from the time averaged power consumption, the average state of charge of the flywheel may tend to drift away over time, the mains power consumption setpoint SET may be adjusted based on the state of charge SOC of the flywheel. As depicted in Figure 6, in case the state of charge of the flywheel exceeds above a maximum threshold MAX, the mains power consumption setpoint SET may be decreased below its nominal value NOM, having the net effect that the mains power consumption is reduced, causing the state of charge of the flywheel to reduce over time. Similarly, as depicted in figure 8, in case the state of charge of the flywheel exceeds below a minimum threshold MIN, the mains power consumption setpoint may be increased, having the net effect that the mains power consumption is increased, causing the state of charge of the flywheel to increase over time. Thus, the state of charge of the flywheel is allowed to fluctuate as needed between the minimum threshold and the maximum threshold, e.g. forming a desired operating range. As the state of charge drifts away out of this range, the mains power consumption may be adjusted so as to provide that the state of charge returns to the range between the minimum threshold and the maximum threshold.
The mains power consumption setpoint may further be determined from a setpoint of the electric motor, i.e. a setpoint of the crane. The setpoint of the crane may for example form a setpoint trajectory. An expected load by the electric motor of the crane may be derived from the setpoint. The load setpoint of the electric motor may for example be time averaged and the mains power consumption setpoint determined from the time averaged load setpoint of the electric motor.
The flywheel system comprises a converter to convert AC mains electrical power into DC electrical power at a DC power bus and a converter to convert the DC electrical power at the
DC bus into an AC motor drive of the motor that drives the rotor of the flywheel. As the crane, i.e. the electric motor of the crane, recuperates energy, e.g. by lowering the load, the electric motor of the crane may generate an amount of reactive power. The converter may be driven to compensate reactive power as the electric motor regenerates electrical energy.
The compensation of reactive power may be included in the feedback loop by the feedback controller, as follows: At the mains power connection, mains power supply current and voltage is measured by the voltage measurement device VMD and the current measurement device
CMD respectively, and reactive power may be derived from a phase relation between the measured power supply current and the measured power supply voltage.. In case the measured current and voltage are out of phase, the controller may drive the converter CNV connected to the flywheel to compensate the reactive power, thus bringing the mains current and voltage at the mains power connection more in phase with each other, reducing a reactive load component on the mains power supply. The converter may hence form the reactive power compensation device. As another example of the reactive power compensation device, a switchable capacitor or a switchable inductor may be provided, whereby the controller controls at least one switch of the reactive power compensation device to connect the capacitor or inductor to the power supply connection to at least partly compensate the reactive power.
Claims (18)
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL2035105A NL2035105B1 (en) | 2023-06-15 | 2023-06-15 | Crane electrical load stabilisation |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL2035105A NL2035105B1 (en) | 2023-06-15 | 2023-06-15 | Crane electrical load stabilisation |
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110098629A (en) | 2019-06-05 | 2019-08-06 | 大连亨利科技有限公司 | Flying wheel battery and chemical cell stored energy application are in harbor crane brake energy regeneration system |
| WO2022023720A1 (en) * | 2020-07-27 | 2022-02-03 | Punch Flybrid Limited | Power generation control with an energy storage system |
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2023
- 2023-06-15 NL NL2035105A patent/NL2035105B1/en active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110098629A (en) | 2019-06-05 | 2019-08-06 | 大连亨利科技有限公司 | Flying wheel battery and chemical cell stored energy application are in harbor crane brake energy regeneration system |
| WO2022023720A1 (en) * | 2020-07-27 | 2022-02-03 | Punch Flybrid Limited | Power generation control with an energy storage system |
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| Title |
|---|
| ABB: "PowerStore Renewable microgrid stabilization", 29 September 2014 (2014-09-29), pages 1 - 8, XP093113627, Retrieved from the Internet <URL:https://figliodellafantasia.files.wordpress.com/2014/09/powerstore_brochure_abb.pdf> [retrieved on 20231219] * |
| GUEST POST: "ABB Adds Flywheel to Remote Kodiak Island Microgrid | Microgrid Knowledge", 12 September 2014 (2014-09-12), pages 1 - 7, XP093113645, Retrieved from the Internet <URL:https://www.microgridknowledge.com/infrastructure/article/11433426/abb-adds-flywheel-to-remote-kodiak-island-microgrid> [retrieved on 20231219] * |
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