Power control unit and propulsion system

Abstract

A power control unit (1) for a propulsion system (100) of a marine vessel, the propulsion system comprising an internal combustion engine (4) and a shaft (2) with a shaft generator (5), the power control unit (1) being configured to provide a fuel command to the internal combustion engine (4) based on a slow component of a speed error of the shaft (2), i.e. A slow component of a deviation of a shaft speed from a speed setpoint. A generator power command is provided to the axle generator (5) based on a fast component of the speed error of the shaft (2) and based on a grid state of a grid electrically connected to the axle generator (5). And the energy buffer (7) is used for storing electric power from the axle generator (5) and discharging the electric power to the axle generator (5) and the power grid (8). Therefore, a more stable engine control mechanism and avoidance of engine overload can be realized more easily.

Description

Technical Field

[0001] The present invention relates to a power control unit, a propulsion system having such a power control unit, and a method for controlling such a propulsion system. Background Technology

[0002] The propulsion system preferably includes an internal combustion engine, such as a large marine or ship engine or a stationary engine, with cylinders having an inner diameter of at least 200 mm. The engine is preferably a two-stroke engine or a two-stroke crosshead engine. The engine can be a diesel engine or a gas engine, a dual-fuel or multi-fuel engine. Combustion of liquid and / or gaseous fuels, as well as self-ignition or forced ignition, are possible in such engines.

[0003] The internal combustion engine can be a longitudinally scavenged two-stroke engine.

[0004] The term "internal combustion engine" also refers to large engines that can operate not only in diesel mode (characterized by self-ignition of fuel) but also in Otto mode (characterized by forced ignition of fuel), or in a combination of both. Furthermore, the term "internal combustion engine" specifically includes dual-fuel engines and large engines in which self-ignition of one fuel is used for forced ignition of another fuel. Forced ignition can be achieved by using a pre-combustion chamber, spark plugs, and / or igniting the fuel.

[0005] The engine speed is preferably below 800 RPM, especially for four-stroke engines, and more preferably below 200 RPM, especially for two-stroke engines, which indicates the designation of a low-speed engine.

[0006] The fuel can be diesel or marine diesel or heavy fuel oil or emulsion or slurry or methanol or ethanol, as well as gases such as liquefied natural gas (LNG), liquefied petroleum gas (LPG), natural gas (NG), petroleum gas (PG), etc.

[0007] Other possible fuels include: LBG (liquefied biogas), biofuels (such as oil made from algae or seaweed), ammonia, hydrogen, and synthetic fuels derived from CO2 (such as those produced via power-to-gas or power-to-liquid conversion).

[0008] Large ships, especially those used for transporting cargo, are typically powered by internal combustion engines, particularly diesel and / or gas engines, usually two-stroke crosshead engines.

[0009] Typically, for example, two-stroke internal combustion engines used for propulsion of marine vessels are equipped with shaft-driven generators.

[0010] Shaft-driven generators are used to generate electricity to power various equipment on board, such as pumps, gas reliquefaction facilities, refrigerated containers, and general hotel loads.

[0011] Typically, shaft-driven generators are connected to the AC grid via a variable frequency drive (VFD). According to DK202270114A1, the shaft-driven generator control system is configured to allow power consumption to differ from power generation during an initial period of at least 2 seconds, in order to maintain the inherent stability of the system.

[0012] It is known that internal combustion engines are controlled by automatically maintaining a given engine shaft speed due to metered fuel supply, particularly by a fuel supply control system.

[0013] However, shaft speed can vary due to changing external conditions, such as weather conditions or sudden changes in electrical load, which can lead to rapidly changing fuel supply. This can cause engine overload and / or system instability. Furthermore, the system's inertia may be too high, making it impossible for the engine to follow such rapidly changing fuel supply commands. Summary of the Invention

[0014] Therefore, the technical problem to be solved by the present invention is to provide a power control unit, a propulsion system, and a method for controlling the propulsion system, which at least partially avoids the disadvantages of prior art solutions and provides a more stable engine control mechanism and reduces the risk of engine overload.

[0015] According to a first aspect of the invention, this technical problem is solved by a power control unit for a propulsion system, the propulsion system comprising an internal combustion engine and a shaft for transmitting propulsive force from the engine.

[0016] The propulsion system is preferably a propulsion system for marine vessels. The internal combustion engine is preferably a large marine engine, more preferably a two-stroke engine and / or a two-stroke crosshead engine, and has at least one cylinder with an inner diameter of at least 200 mm.

[0017] The power control unit is configured to provide engine power commands for the internal combustion engine based on the shaft status.

[0018] In this application, the state of the shaft describes the dynamic characteristics of the shaft, such as the propeller speed, the shaft rotational speed (typically given in revolutions per minute), the rotational frequency, or the torque.

[0019] According to the invention, the power control unit includes a discriminator, such as a filter or an FFT-based discriminator, which is configured to derive fast and slow components from the state of the axis.

[0020] In this application, preferably, shaft state oscillations with a period of no more than 25 seconds can be considered "fast", and shaft state oscillations with a period of more than 25 seconds can be considered "slow".

[0021] The time-dependent signal corresponding to the axis state can be routed through a low-pass filter and / or a high-pass filter to obtain the slow component and / or the fast component, respectively.

[0022] The slow component corresponds to the slow change in the shaft state that occurs at low frequencies, while the fast component is associated with higher frequencies.

[0023] The slow component can depend on adjustable parameters of the internal combustion engine, such as load, fuel quantity, fuel type, and recirculated exhaust volume, or on slowly changing influencing factors, such as ambient temperature, ambient pressure, general wind direction, or ocean currents.

[0024] Fast components can depend on rapidly changing factors, such as ocean waves.

[0025] For control loops, it may be advantageous to distinguish between fast and slow components based on the control variable.

[0026] The discriminator is preferably a frequency discriminator capable of separating shaft state components within a range lower than or equal to a predetermined first frequency from shaft state components within a range higher than a predetermined second frequency. Therefore, the frequency discriminator is configured to separate slow shaft state components within a range lower than or equal to the first frequency from fast shaft state components within a range higher than the second frequency.

[0027] The predetermined first frequency can be equal to the predetermined second frequency. The discriminator may include a frequency filter implemented in a corresponding software component and may use a Fast Fourier Transform (FFT).

[0028] The power control unit can be configured to receive and / or store the first and / or second predetermined frequencies. The first and / or second predetermined frequencies are preferably advantageously within the range of typical ocean wave frequencies or several times higher than typical ocean wave frequencies, particularly in the range of 0.05 Hz to 0.1 Hz.

[0029] The first and / or second predetermined frequency can be determined during workshop or sea trials. The first and / or second predetermined frequency may depend on the type of fuel and / or load and / or engine type and / or propeller type.

[0030] The internal combustion engine is preferably a dual-fuel engine. The power control unit can be configured to switch between operation of a first fuel (e.g., LNG, LPG, methanol, ethanol, or ammonia) and operation of a second fuel (e.g., a diesel-like fuel). During operation of the first fuel, a first predetermined frequency and / or a second predetermined frequency can be set for the first fuel. During operation of the second fuel, a first predetermined frequency and / or a second predetermined frequency can be set for the second fuel. This allows for adjustment of the differentiation between slow and fast components based on the type of fuel used.

[0031] Because combustion duration depends on the fuel, an engine can be more or less sensitive to load changes. For example, the combustion duration of low-pressure gases is shorter than that of diesel fuel. Therefore, diesel engines are more robust than gas engines under varying load conditions.

[0032] Therefore, the first predetermined frequency and / or the second predetermined frequency typically depend on the fuel. For a dual-fuel engine, the power control unit can be configured to set the first predetermined frequency and / or the second predetermined frequency according to the fuel used, and in particular, to switch between the corresponding first predetermined frequency and / or second predetermined frequency according to the fuel used. The first predetermined frequency and / or the second predetermined frequency can be determined based on the first predetermined frequency and / or the second predetermined frequency stored in the memory of the power control unit or selected from a table of the stored first predetermined frequency and / or second predetermined frequency.

[0033] The power control unit may be part of the engine control system and / or drive control system and / or may be adapted to receive input from other parts of the internal combustion engine and take into account the input to provide engine power commands.

[0034] The power control unit is preferably configured to receive shaft status data indicating the state of the shaft.

[0035] This shaft status data can indicate the shaft's speed and / or torque.

[0036] The shaft status data can be represented by a first sensor signal provided by a first sensor. This sensor can be a speed sensor, such as a rev counter, or a torque sensor, which is arranged to measure the speed and / or torque of the shaft.

[0037] Typically, torque variations affect the shaft's rotational speed. Shaft speed can be used as a reference signal.

[0038] Torque adjustment is not the preferred method because torque measurement is not very accurate, while shaft speed measurement is very accurate. In particular, shaft speed can be measured with very high precision.

[0039] Engine power commands may include fuel commands for the internal combustion engine.

[0040] The fuel command can set the amount of fuel, such as diesel, heavy fuel oil, LNG, methanol, or ammonia, to be injected into the engine through the fuel supply system.

[0041] Fuel commands are typically provided based on shaft speed and / or shaft torque and / or shaft speed setpoint, which is stored in and / or received by the power control unit.

[0042] If the actual shaft speed differs from the shaft speed setpoint, the fuel quantity can be increased or decreased, depending on whether the speed is too high or too low. High-frequency variations in shaft speed can destabilize the control loop.

[0043] According to the invention, preferably, the fuel command is provided based on the slow component, without taking into account the fast component. This is what the term "based solely on the slow component" means (see below).

[0044] Alternatively or additionally, the engine power command may include commands for setting the variable compression ratio, exhaust gas recirculation rate, and / or ignition timing.

[0045] Preferably, the engine power command, and in particular the fuel command, is provided based on the slow component of the shaft's state, and especially wherein the engine power command is based only on the slow component of the shaft's state. In this context, "based only on the slow component" means that the fuel command is not based on the fast component.

[0046] The engine power command, and especially the fuel command, can be provided based on a slow component, wherein the frequency is below a first predetermined limit.

[0047] A control loop can be established based on the engine power command provided by the slow component, which is used to provide a more stable and / or at least more slowly varying fuel supply.

[0048] When considering the fast component of shaft speed to provide fuel commands associated with frequencies above a predetermined frequency, there is a risk that the fuel command will exceed the maximum permissible load for at least a short period of time, and this risk should be avoided.

[0049] Therefore, distinguishing between the fast and slow components helps keep the engine operating within its operating limits and / or under better conditions in terms of fuel efficiency, emissions, engine wear, etc. This helps improve the engine's economic and environmental efficiency.

[0050] Providing fuel commands that only consider the slow component of shaft conditions (such as shaft speed) can lead to reduced fuel consumption because it avoids excessive fuel spikes caused by transient effects.

[0051] In addition, it can prevent a drop in Lambda (air-fuel ratio).

[0052] By responding only to the slower-responding components, fuel can be saved.

[0053] The first and second frequencies can depend on the fuel type and compression ratio.

[0054] The power control unit can be configured to set a first predetermined frequency and / or a second predetermined frequency based on the compression ratio, particularly the geometric compression ratio of a VCR engine. The first predetermined frequency and / or the second predetermined frequency can be selected from a stored table of predetermined frequencies.

[0055] For example, in a VCR engine with a low compression ratio, speed oscillations may have a relatively small impact on fuel consumption. Therefore, identification does not need to react to small power changes and overloads.

[0056] However, if a high compression ratio is used, identification requires faster response tuning.

[0057] Small overload margins can be compensated for by the battery operating as a buffer and providing additional margin. Optimal compression ratios can be maintained more easily, and the battery can be used to temporarily bridge power demands if additional power is needed for propulsion (see below).

[0058] The propulsion system may also include a shaft-driven generator connected to the shaft, which is used to receive mechanical power from the shaft and / or to supply mechanical power to the shaft.

[0059] For these propulsion systems, the power control unit can be configured to provide a generator power command to the shaft-driven generator, the generator power command indicating the mechanical power to be received from and / or supplied to the shaft via the shaft-driven generator. Therefore, the output and / or supply of mechanical power can be controlled by the power control unit.

[0060] The generator power command can be based on the fast component of the shaft state, or more specifically, based only on the fast component of the shaft state. In this context, "based only on the fast component" means "not dependent on the slow component".

[0061] Therefore, shaft-driven generators can respond to control commands more instantly. Consequently, they are less prone to instability under rapidly changing conditions. Furthermore, since shaft-driven generators are typically electrically driven, they can deliver power almost instantly.

[0062] The generator power command can be provided based on a fast component, where the frequency is higher than a second predetermined limit.

[0063] The second predetermined limit may be the same as or different from the first predetermined limit.

[0064] Typically, the external torque applied to the shaft can be a variable propeller torque caused by propulsion torque, rudder motion, or wave load, as well as shaft-driven generator torque associated with variable electrical load.

[0065] The generator power command that causes the electrical load to change according to the fast component can affect the state of the shaft, especially the fast component, and can provide the basis for a closed-loop control loop that results in a more stable fast component and / or minimized fast oscillations.

[0066] The generator power command can be based on the fast component of the shaft speed. Typically, the electrical load of a shaft-driven generator can be directly controlled by torque, especially by the fast component.

[0067] The power control unit can be configured to receive electrical state data indicating the state of the power grid connected to the generator on the shaft, such as power demand. The power control unit is configured to provide generator power commands and / or engine power commands based on the received electrical state data.

[0068] The power grid status may include data on voltage, current, electrical load, electrical frequency, and electrical power of the power grid or a portion thereof.

[0069] The power grid may include electricity consumers and / or, for example, additional generators driven by auxiliary engines.

[0070] Specifically, the power grid may include an electrical buffer. The generator power command may be related to the power demand of the electrical consumer and / or the power demand or capacity of the electrical buffer.

[0071] The generator power command can be provided based on a fast component, where the frequency is higher than a second predetermined limit. This fast component can be a fluctuating signal. The electrical buffer can stabilize the power grid by compensating for fluctuating energy supply.

[0072] Not only shaft status but also grid status can be considered for providing generator power commands and / or engine power commands. In particular, when the grid requires more energy, a corresponding fuel command can be provided to the engine.

[0073] Although the electrical load of a shaft-driven generator can typically be controlled by the fast component of torque or shaft speed, it may be necessary to supply additional energy to the grid, particularly to the electrical buffer, for example, to meet slowly varying power demands. In such cases, the generator power command can also be based on the slow component. A portion of the power from the shaft can then be used to supply electrical energy. This can trigger a corresponding fuel command to supply the additional electrical energy.

[0074] The shaft-driven generator power command can set an appropriate electrical load that corresponds to the required power consumption of the ship's electrical grid.

[0075] The shaft-driven generator power command can set the appropriate electrical load to be buffered in the energy storage.

[0076] If needed, the power control unit can provide fuel commands based on electrical state data, for example, to generate more energy to be released to the shaft-driven generator and the power grid.

[0077] The power grid may include a regulator or electrical load control that controls the power grid, particularly based on the state of the power grid.

[0078] Data indicating the state of the power grid can also be provided to the grid regulator.

[0079] The regulator can provide the data to the power control unit, or the regulator can provide engine control commands through the power control unit (e.g., if the power grid requires more electrical energy than the shaft provides) or generator power commands (e.g., when more mechanical power is required due to the fast component of the shaft state).

[0080] The power control unit can be configured to provide engine power commands and / or generator power commands based on the deviation of the shaft state from a setpoint, particularly based on the deviation of the shaft speed from a speed setpoint and / or the deviation of the shaft torque from a torque setpoint. The setpoint can be stored in the power control unit and / or received by the power control unit.

[0081] This speed setpoint is a predetermined revolutions per minute on the propeller curve, which depends on the torque or load, and is used to determine the corresponding required amount of fuel.

[0082] The power control unit can be configured to provide engine power commands and / or generator power commands based on the deviation of the fast and / or slow components of the shaft state from the corresponding setpoint.

[0083] This setpoint can depend on the specific engine layout, the expected ship speed, and the expected acceleration curve.

[0084] The relationship between the deviation and the corresponding fuel command and / or the corresponding generator power command can be predetermined and can be stored and / or received by the engine power control unit.

[0085] The setpoints and permissible deviations can be determined during workshop testing, or they can be provided to the vessel remotely, for example, via a satellite data link.

[0086] This power control unit can be configured to continuously provide engine power commands and / or generator power commands not only during engine start-up and / or fuel-change operation and / or anticipated load-change operation, but throughout the entire engine operating range. This contributes to efficiency and fuel consumption, reduces component stress, and minimizes vibration.

[0087] According to a second aspect of the invention, the technical problem of the invention is also solved by a propulsion system comprising a power control unit according to a first aspect of the invention.

[0088] This propulsion system is especially used for propulsion systems of marine vessels.

[0089] The propulsion system includes the power control unit as described above. The propulsion system also includes an internal combustion engine, preferably a two-stroke engine and / or a two-stroke crosshead engine, the internal combustion engine having at least one cylinder with an inner diameter of at least 200 mm. The internal combustion engine is preferably a dual-fuel engine.

[0090] The propulsion system includes a shaft for transmitting propulsive force from the engine. The propulsion system also includes a first sensor for providing the power control unit with shaft status data indicating the state of the shaft, particularly indicating the shaft's speed and / or torque.

[0091] The power control unit is configured to provide an engine power command to the internal combustion engine, wherein the engine power command is particularly based on the slow component of the shaft state.

[0092] The propulsion system may also include a shaft-driven generator connected to the shaft, which is used to receive mechanical power from the shaft and / or to supply mechanical power to the shaft.

[0093] The power control unit can be configured to provide a generator power command to the shaft-driven generator, the generator power command indicating the mechanical power to be received from and / or supplied to the shaft via the shaft-driven generator, wherein the generator power command is particularly based on the fast component of the shaft state.

[0094] The power control unit can be divided into an engine control unit and an electrical control unit, or it can be an integrated controller. The power control unit can be part of an overall engine control unit.

[0095] The propulsion system may also include a second sensor for providing electrical status data to the power control unit, the electrical status data indicating the grid status of the power grid electrically connected to the shaft-driven generator.

[0096] The generator power command and / or the engine power command may be based on the electrical state data, such as the power demand of the ship's electrical consumers.

[0097] The propulsion system may also include an energy buffer, such as a battery, electrically connected to the shaft-driven generator and / or the power grid, the energy buffer being configured to store and release electrical energy. Thus, power can be received from the shaft and stored in the energy buffer, and / or extracted from the energy buffer and supplied to the shaft or an electrical consumer.

[0098] The electrical state data may include buffer data indicating the state of the energy buffer, such as the charge level, so that the power control unit can take the buffer data into account when providing generator power commands and / or engine power commands.

[0099] The generator power command can specify taking generator power from the shaft and transmitting it to the power grid and / or buffering it in an energy buffer, and / or providing electrical energy from the energy buffer and converting it into mechanical energy to be supplied to the shaft. Therefore, it is easier to meet power demands, which helps stabilize the system.

[0100] The propulsion system's electrical grid may include a regulator or electrical load control, which may be adapted to distribute electrical power to consumers, energy buffers, and shafts. The regulator may be adapted to provide commands for servicing the electrical grid and / or energy buffers based on the ship's power consumption requirements and the shaft's power input or output requirements.

[0101] For normal operation, the average electrical power supplied by the shaft-driven generator should equal the power required by the power grid. Transients can be covered by energy buffers.

[0102] The energy buffer can be any battery, preferably a high-power battery, such as lithium nickel cobalt manganese oxide (NMC) or lithium titanate or lithium titanium oxide (LTO) batteries.

[0103] The power capacity of this energy buffer should be at least 1% of the maximum internal combustion engine power. Repeated short charge / discharge cycles should have a negligible impact on the lifespan. As mentioned earlier, NMC and LTO are effective solutions. Lithium iron phosphate (LFP) batteries can also be used, but those with higher capacity should be used due to their lower discharge / charge current.

[0104] The propulsion system may include a power control unit that can be configured to provide generator power commands and / or engine power commands based on the deviation of the shaft state from a set point, particularly the fast and / or slow components of the shaft state.

[0105] The propulsion system advantageously includes a frequency discriminator configured to separate slow-axis state components in a range below or equal to a predetermined first frequency from fast-axis state components in a range above a predetermined second frequency.

[0106] Advantageously, the internal combustion engine can be a dual-fuel engine, and the frequency discriminator can be configured to set a first frequency and / or a second frequency depending on the fuel used. This makes it easier to adapt to different fuels as described above.

[0107] In another preferred embodiment, the propulsion system may include a wind-driven component, such as a Flettner rotor. A Flettner rotor is a vertical cylinder mounted on the ship that rotates and generates driving force due to the so-called Magnus effect. This wind-driven component can be mechanically driven to generate driving force, or it can be electrically driven. This driving force can be generated by the power grid and / or by a shaft-driven generator driven by an engine as described above. Wind-driven components, such as Flettner rotors, can reduce the ship's fuel consumption.

[0108] In propulsion systems that include such wind-driven components, ship propulsion is typically provided by both propeller-driven operation (i.e., using a ship propeller connected to a shaft) and thrust provided by the wind-driven components.

[0109] The propulsion system control unit can switch the ratio between propeller-driven operation and wind-assisted operation. During propeller-driven operation only, when the wind-driven element is set to passive, the power control unit can operate as described above.

[0110] During (partial) wind-assisted operation, when the wind-driven element is set to active, in addition to the transient components caused by waves, ocean currents, etc., the shaft may experience additional transient components, such as those caused by changes in wind. Sudden changes in wind direction and / or wind speed may affect the shaft's torque and / or speed. Sudden changes in driving force caused by sudden changes in wind may lead to sudden changes in the load on the engine, which could result in unexpected engine shutdown. This should be prevented.

[0111] Therefore, the power control unit can be configured to set the first and / or second frequencies based on propeller-driven operation and parameters related to the wind-driven components (such as wind speed, wind direction, and / or the mechanical driving force of the wind-driven elements).

[0112] This power control unit can switch between propeller-driven operation and wind-assisted operation. For each case, an appropriate first and / or second frequency can be determined and / or set.

[0113] According to a third aspect of the invention, the aforementioned technical problem is also solved by a method for controlling a propulsion system, particularly a propulsion system for marine vessels, as described above with respect to the second aspect of the invention.

[0114] The propulsion system includes an internal combustion engine, preferably a two-stroke engine and / or a two-stroke crosshead engine, the internal combustion engine having at least one cylinder with an inner diameter of at least 200 mm. The engine is preferably a dual-fuel engine.

[0115] The propulsion system also includes a shaft for transmitting propulsive force from the engine. The method includes the following steps.

[0116] Provide shaft status data, particularly indicating shaft speed and / or shaft torque. This shaft data can be derived from a signal from a first sensor, preferably as described above, and can be received by a power control unit of the propulsion system, preferably as described above.

[0117] Derive the fast and slow components from the state of the axis.

[0118] The fast and slow components are derived by a discriminator with software and / or hardware components.

[0119] The electronic signal of the first sensor can be filtered by electronic high-pass and / or low-pass filters, and / or the electronic sensor signal can be digitized and filtered by software such as FFT-based analysis.

[0120] Then, based on the state of the shaft, especially the slow component based on the state of the shaft, the engine power command and the preferred fuel command are given to the internal combustion engine.

[0121] Slow component control of internal combustion engines based on shaft state helps keep the system within its operating limits.

[0122] The propulsion system may also include a shaft-driven generator connected to the shaft for receiving mechanical power from and / or supplying mechanical power to the shaft. When receiving mechanical power from the shaft and thereby generating electrical energy, the shaft-driven generator acts as a "generator." When receiving electrical energy and supplying mechanical power to the shaft, the shaft-driven generator acts as an electric motor. Both functions should be included in the term "shaft-driven generator" as used herein. The method may include the step of providing a generator power command to the shaft-driven generator, indicating the amount of mechanical power to be received from and / or supplied to the shaft, particularly based on the fast component of the shaft's state.

[0123] The slow component can be used in the control loop of the internal combustion engine, while the fast component of the shaft state can be compensated by the power grid. Together, they achieve a more stable shaft state and engine operation.

[0124] Electrical state data indicating the state of the power grid connected to the generator on this shaft can be provided, for example, by the grid regulator. The generator power command and / or the engine power command can then be based on this grid state.

[0125] The state of the power grid can be characterized by the power consumption of the external power grid and / or the absorption and / or transmission capacity of the energy buffer.

[0126] In a further step, the power from the shaft can be stored in an energy buffer by means of the shaft-driven generator, particularly according to the fast component of the shaft state and preferably according to the grid state of the power grid electrically connected to the shaft-driven generator.

[0127] Additionally or alternatively, power from the energy buffer can be supplied to the shaft via the shaft-driven generator, particularly according to the fast component of the shaft condition and preferably according to the grid condition of the grid electrically connected to the shaft-driven generator.

[0128] When the fast component causes the shaft generator power to exceed the ship's electrical demand, the additional power can be supplied to the energy buffer.

[0129] When fast components cause the shaft-driven generator power to fall below the grid's power demand, the energy buffer can supply the missing power.

[0130] If the shaft speed decreases or the torque requirement increases, the power of the shaft-driven generator should be reduced so that no energy is released from the shaft, which is necessary for ship propulsion. As an alternative or supplement, power can be supplied to the shaft by a shaft-driven generator that acts as an electric motor.

[0131] Then the energy power provided by the electric buffer can be increased, so that the energy storage provides the missing power.

[0132] If the shaft speed increases or if the torque decreases, the power of the shaft-driven generator can be increased, and the energy storage can capture the power surplus.

[0133] It can provide setpoints for shaft conditions, especially speed setpoints and / or torque setpoints.

[0134] The engine power command and / or the generator power command can be provided based on the deviation of the shaft condition from the setpoint, particularly based on the deviation of the shaft speed from the speed setpoint. This makes it easier to keep the propulsion system within its ideal operating limits.

[0135] The internal combustion engine may be a dual-fuel engine, and the method may include the step of separating a slow-axis state component in a range below or equal to a predetermined first frequency from a fast-axis state component in a range above a predetermined second frequency using a frequency discriminator. The first frequency and / or the second frequency may depend on the fuel used.

[0136] The internal combustion engine may include a wind-driven component.

[0137] The method may include the steps of setting and / or determining a first frequency and / or a second frequency according to at least one of the following:

[0138] -The fuel used,

[0139] - The proportion of driving force generated by wind-driven components

[0140] - Parameters related to wind-driven components, such as wind direction and / or wind speed.

[0141] According to another aspect of the invention, the technical problem is also solved by a marine vessel that includes the propulsion system described above and preferably includes an electrical grid.

[0142] According to another aspect of the invention, the technical problem is also solved by a computer program product comprising instructions to cause a power control unit as described above with respect to the first aspect of the invention or a propulsion system as described above with respect to the second aspect of the invention to perform the steps of the method as described above with respect to the third aspect of the invention.

[0143] The computer program product can be stored on a computer-readable medium. Attached Figure Description

[0144] Other advantageous aspects of the invention will be explained below with reference to exemplary embodiments and the accompanying drawings. Functionally equivalent elements are provided with the same reference numerals. In the drawings, in an illustrative manner:

[0145] Figure 1 A schematic diagram of a propulsion system according to the prior art is shown;

[0146] Figure 2 A schematic diagram of the propulsion system according to the present invention is shown;

[0147] Figure 3 This shows the process of the shaft speed setpoint changing over time;

[0148] Figure 4a An exemplary process is shown where shaft speed error changes over time;

[0149] Figure 4b This illustrates an exemplary process for fuel command according to the prior art, which is... Figure 4a The shaft speed error shown is generated;

[0150] Figure 5a An exemplary process is shown where shaft speed error changes over time;

[0151] Figure 5b An exemplary process for fuel command according to the present invention is shown, which is performed by... Figure 5a The shaft speed error shown is generated. Detailed Implementation

[0152] Figure 1A schematic diagram of a propulsion system 100 according to the prior art is shown.

[0153] The propulsion system 100 includes an internal combustion engine 4 and a shaft 2 for transmitting propulsion from the engine 4.

[0154] The power control unit 1 is configured to provide engine power commands for the internal combustion engine 4 based on the state of the shaft 2. For example, the speed of the shaft is measured, and if the measured speed exceeds a permissible range relative to a predetermined shaft speed, more or less fuel is injected into the internal combustion engine 4 depending on whether the speed is too low or too high.

[0155] In addition, a shaft-driven generator 5 is connected to shaft 2 to receive mechanical power from shaft 2 and to supply electrical power to the power grid 8. Therefore, a portion of the shaft energy is branched off to supply power to the power grid 8.

[0156] The power grid 8 may include a consumer (not explicitly shown in the figure) and an energy buffer 7, particularly a battery.

[0157] The power grid 8 includes a regulator 6 that distributes the electrical power supplied by the shaft-driven generator 5 to the consumers and the battery 7 according to the state of the power grid 8. If the consumers, for example, do not require any energy, the battery can be charged. If the consumers require more energy than the shaft-driven generator 5 can supply, they can obtain energy from the battery 7.

[0158] According to existing technology, fuel control and grid control are independent of each other.

[0159] Figure 2 A schematic diagram of a propulsion system 100 according to the present invention is shown.

[0160] The propulsion system 100 includes an internal combustion engine 4 and a shaft 2 for transmitting propulsive force from the engine 4. The power control unit 1 is configured to provide an engine power command, including a fuel command for the internal combustion engine 4, based on the state of the shaft 2, specifically based on the slow component of the shaft speed error (i.e., the deviation from the speed setpoint).

[0161] According to the present invention, the power control unit 1 includes a discriminator 3 configured to derive fast and slow components from the state of the shaft 2. Only the slow component of the shaft state is used to determine the fuel command.

[0162] The shaft-driven generator 5 is connected to the shaft 2 for receiving mechanical power from the shaft 2 and for supplying electrical power to the power grid 8, and, when necessary, for receiving electrical power from the power grid 8 and for supplying mechanical power to the shaft 2.

[0163] Therefore, the shaft-driven generator 5 can be regarded as a bidirectional interface between the shaft 2 and the power grid 8.

[0164] The power grid 8 includes a consumer (not shown in the figure) and a battery that acts as an energy buffer 7.

[0165] The power grid 8 includes a regulator 6, which distributes the electrical power provided by the shaft generator 5 to the consumer and battery 7 according to the state of the power grid 8.

[0166] On the other hand, regulator 6 is connected to power control unit 1 to receive generator power commands.

[0167] Based on the status of the power grid 8 and the generator power command, when the electrical energy provided by the shaft generator 5 is insufficient for the power grid 8, the regulator 6 can provide a fuel command to the control unit 1 to increase the engine power.

[0168] The power control unit 1 is configured to provide a generator power command for the shaft-driven generator 5, which indicates the mechanical power to be received from and / or supplied to the shaft 2 via the shaft-driven generator 5.

[0169] The generator power command is based only on the fast component of the state of axis 2.

[0170] Therefore, rapid changes in shaft speed can be responded to not by changes in the amount of fuel injected into engine 4, but by changes in the mechanical energy absorbed or supplied by shaft-driven generator 5.

[0171] The propulsion system 100 includes a first sensor 11, specifically an shaft speed sensor that provides shaft status data to the control unit 1.

[0172] The power grid 8 includes a second sensor 10 for providing electrical state data to the regulator 6.

[0173] Figure 3 Examples show the process of the shaft speed setpoint changing with time (straight line) and the process of the shaft speed changing with time (oscillating line).

[0174] The expected shaft speed can be increased at the beginning, then kept constant, and then increased further at a gentler slope.

[0175] Figure 4a An exemplary process for shaft speed error according to the prior art is shown.

[0176] In such cases, for example due to ocean waves, the shaft velocity error has a rapidly changing component (oscillation).

[0177] Fuel commands typically attempt to follow this behavior, such as Figure 4b As shown. However, due to the system's inertia, the system may fail to keep up.

[0178] Figure 4b This illustrates an exemplary process for fuel command according to the prior art, which is... Figure 4a The shaft speed error shown is generated. Due to the rapidly changing shaft speed error, the fuel command oscillates and may exceed the system's load limits.

[0179] The oscillation of fuel command may even amplify the shaft speed oscillation, which could further worsen the situation.

[0180] Figure 5a An exemplary process is shown in which the shaft speed error changes over time in the propulsion device according to the present invention.

[0181] In this figure, the curve named ControlError includes rapid oscillations and involves shaft speed error, while the curve named ControlErrorPS is smoother and only involves the slow component of shaft speed error.

[0182] In this example, the shaft speed error also changes rapidly due to the waves, as can be seen in the ControlError curve with rapid oscillations.

[0183] However, due to engine 4 (see Figure 2 The fuel command responds only to the slow component of the shaft speed error (i.e., the ControlErrorPS curve) rather than its fast component, allowing the system to control more smoothly. Figure 5b I saw it in the middle.

[0184] Figure 5b An exemplary process for fuel command according to the present invention is shown, which is performed by... Figure 5a The slow component of the shaft speed error shown (i.e., the ControlErrorPS curve) is generated.

[0185] Because the fuel command is set considering only the slow component of the shaft speed, it does not oscillate rapidly and instead oscillates within a relatively small range. This helps to keep the fuel command mostly within the limits represented by the upper and lower bandwidth lines.

[0186] The frequency limit used to distinguish between the fast and slow components is preferably set to minimize fuel consumption along the shaft speed setpoint over time.

Claims

1. A power control unit (1) for a propulsion system (100), the propulsion system comprising an internal combustion engine (4), particularly a dual-fuel two-stroke engine, and a shaft (2) for transmitting propulsive force from the internal combustion engine (4), the internal combustion engine having at least one cylinder having an inner diameter of at least 200 mm. in, The power control unit (1) is configured to provide engine power commands for the internal combustion engine (4) based on the state of the shaft (2), and The power control unit (1) includes a discriminator (3) configured to derive fast and slow components from the state of the shaft (2).

2. The power control unit (1) according to claim 1, wherein, The discriminator is a frequency discriminator configured to separate slow axis state components in a range below or equal to a predetermined first frequency from fast axis state components in a range above a predetermined second frequency.

3. The power control unit (1) according to claim 1 or 2, wherein, The power control unit is configured to receive shaft status data indicating the state of the shaft (2), and in particular, the shaft status data indicates the speed of the shaft (2) and / or the torque of the shaft (2).

4. The power control unit (1) according to any one of the preceding claims, wherein, The engine power command includes a fuel command for the internal combustion engine (4).

5. The power control unit (1) according to any one of the preceding claims, wherein, The power control unit is configured to provide the engine power command based on the slow component of the state of the shaft (2), and in particular, the engine power command is based only on the slow component of the state of the shaft (2).

6. The power control unit (1) according to any one of the preceding claims, wherein, The propulsion system (100) also includes a shaft-driven generator (5) connected to the shaft (2), the shaft-driven generator being used to receive mechanical power from the shaft (2) and / or to supply mechanical power to the shaft (2), and Among them, the power control unit (1) is configured as follows: - Provide a generator power command for the shaft-driven generator (5), the generator power command indicating the mechanical power to be received from and / or supplied to the shaft (2) via the shaft-driven generator (5), In particular, the generator power command is based on the fast component of the state of shaft (2), especially only on the fast component of the state of shaft (2).

7. The power control unit (1) according to claim 6, wherein, The power control unit is configured to receive electrical state data, which indicates the state of the power grid electrically connected to the shaft-driven generator (5), and The power control unit (1) is configured to provide generator power commands and / or engine power commands based on the received electrical state data.

8. The power control unit (1) according to any one of the preceding claims, wherein, The power control unit is configured to provide engine power commands and / or generator power commands based on the deviation of the state of the shaft (2) from the set point, and especially based on the deviation of the speed of the shaft (2) from the speed set point.

9. The power control unit (1) according to any one of claims 2 to 8, wherein, The power control unit is configured for a propulsion system (100) including a dual-fuel engine and is configured to set a first frequency and / or a second frequency according to the fuel used.

10. A propulsion system (100), particularly for marine vessels, said propulsion system comprising a power control unit (1) according to any one of the preceding claims, and further comprising... - Internal combustion engine (4), preferably a dual-fuel two-stroke engine, said internal combustion engine having at least one cylinder having an inner diameter of at least 200 mm, - Shaft (2), used to transmit propulsion from engine (4), and - A first sensor (11) is used to provide shaft status data indicating the state of the shaft to the power control unit (1), the shaft status data specifically indicating the speed and / or torque of the shaft (2). in, The power control unit (1) includes a discriminator (3) configured to derive fast and slow components from the state of the shaft (2), and wherein the power control unit (1) is configured to provide an engine power command to the internal combustion engine (4) based on the state of the shaft (2). The engine power command is particularly based on the slow component of the state of shaft (2).

11. The propulsion system (100) according to claim 10, wherein, The propulsion system also includes - A shaft-driven generator (5) connected to the shaft (2), the shaft-driven generator being used to receive mechanical power from the shaft (2) and / or to supply mechanical power to the shaft (2), The power control unit (1) is configured to provide a generator power command to the shaft-driven generator (5), the generator power command indicating the mechanical power to be received from and / or supplied to the shaft (2) via the shaft-driven generator (5), and The generator power command is particularly based on the fast component of the state of shaft (2).

12. The propulsion system (100) according to claim 11, wherein, The propulsion system also includes a second sensor (10) for providing electrical state data to the power control unit (1), the electrical state data indicating the grid state of the power grid (8) electrically connected to the shaft-driven generator (5), and The generator power command and / or engine power command are based on the electrical state data.

13. The propulsion system (100) according to claim 12, wherein, The propulsion system also includes an energy buffer (7) electrically connected to the shaft-driven generator (5) and / or the power grid (8) and configured to store and release electrical energy. The electrical state data includes buffer data indicating the state of the energy buffer (7), and the power control unit (1) is configured to take the buffer data into account to provide generator power commands and / or engine power commands.

14. The propulsion system (100) according to any one of claims 10 to 13, wherein, The power control unit (1) is configured to provide generator power commands and / or engine power commands based on the deviation of the state of the shaft (2) from the set point, especially based on the deviation of the speed of the shaft (2) from the speed set point and / or based on the deviation of the torque of the shaft (2) from the torque set point.

15. The propulsion system (100) according to any one of claims 10 to 14, wherein, The discriminator is a frequency discriminator configured to separate slow axis state components in a range below or equal to a predetermined first frequency from fast axis state components in a range above a predetermined second frequency.

16. The propulsion system (100) according to claim 15, wherein, The internal combustion engine (4) is a dual-fuel engine, and wherein the frequency discriminator is configured to set a first frequency and / or a second frequency according to the fuel used.

17. The propulsion system (100) according to any one of claims 15 to 16, wherein, The propulsion system also includes a wind-driven component, particularly a Flexner rotor, wherein the frequency discriminator is configured to set a first frequency and / or a second frequency based on parameters associated with the wind-driven component.

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