Shaft generator system

Abstract

A shaft generator system for use with a two-stroke uniflow scavenged crosshead type internal combustion engine is disclosed. The shaft generator system comprises a shaft generator, a first circuit for converting AC current from a first frequency to a second frequency, and a shaft generator control system configured to receive a first signal indicative of power consumption. The shaft generator control system is operatively connected to the shaft generator and configured to control power generation of the shaft generator based on the first signal. The shaft generator control system is configured to allow the power consumption to be different from the power generation for a first period of time of at least 2 seconds.

Description

Technical Field

[0001] The present invention relates to a shaft-driven generator system for use with a two-stroke single-flow scavenging crosshead internal combustion engine, and a propulsion and power generation combination system for propelling ships. Background Technology

[0002] Two-stroke internal combustion engines used for ship propulsion have been equipped with shaft-driven generators for many years. Shaft-driven generators are used to generate electricity for various shipboard equipment, such as propellers, pumps, gas reliquefaction machinery, refrigerated containers, and general shipboard electrical loads.

[0003] Traditionally, shaft-driven generators are directly connected to the ship's AC power grid, thus closely linking the main engine speed to the AC grid frequency. This connection helps stabilize both engine speed and grid frequency.

[0004] Shaft-driven generators are typically connected to the engine via a speed-increasing transmission to allow the AC grid frequency to differ from the engine's rpm.

[0005] However, speed-up transmissions can be expensive, and in order to provide a stable AC grid frequency, the engine's available rpm is limited to a few discrete values ​​depending on the speed-up transmission ratio.

[0006] To address the aforementioned issues, shaft-driven generators are connected to power-consuming devices via frequency conversion equipment (AC to DC and DC to AC).

[0007] This decouples the main engine speed from the grid frequency. This is a more versatile solution because the shaft-driven generator can operate at a wide range of engine speeds without affecting the grid frequency.

[0008] However, by decoupling the engine speed from the grid frequency, the inherent stability of the system is lost.

[0009] To prevent the engine from becoming unstable, the maximum power output of this shaft-driven generator is limited at certain engine speeds.

[0010] Therefore, providing an improved shaft-driven generator system remains a problem. Summary of the Invention

[0011] According to a first aspect, the present invention relates to a shaft-driven generator system for use with a two-stroke, single-flow scavenging crosshead internal combustion engine, the two-stroke, single-flow scavenging crosshead internal combustion engine including an engine shaft, at least one cylinder, a cylinder head, a piston, an engine fuel control system, a fuel supply system, and a scavenging system. The cylinder has cylinder walls, the cylinder head is disposed on the top of the cylinder and has an exhaust valve, the piston is movably disposed within the cylinder along a central axis between bottom dead center and top dead center, the scavenging system has a scavenging inlet disposed at the bottom of the cylinder, and the fuel supply system is configured to inject fuel into a main combustion chamber defined between the piston and the cylinder head based on a control signal provided by the engine fuel control system, wherein the shaft-driven generator system includes:

[0012] A shaft-driven generator configured to generate AC current having a first frequency, the first frequency depending on the RPM of the shaft; a first circuit for converting the AC current from the first frequency to a second frequency; and a shaft-driven generator control system configured to receive a first signal indicating power consumption, wherein the shaft-driven generator control system is operatively connected to the shaft-driven generator and configured to control the power generation of the shaft-driven generator based on the first signal.

[0013] The shaft-driven generator control system is configured to allow power consumption to differ from power generation during a first time period of at least 2 seconds.

[0014] Therefore, by introducing intentional hysteresis into the shaft-driven generator control system, the instability effects caused by constant power generation constraints can be significantly reduced. This allows the shaft-driven generator to generate more power without causing the 2-stroke engine to become unsustainable.

[0015] The internal combustion engine is preferably a large, low-speed, turbocharged, two-stroke, single-flow scavenging crosshead internal combustion engine with a power output of at least 400 kW per cylinder, used for propelling ships or stationary power plants. The internal combustion engine may include a turbocharger driven by the exhaust gases produced by the engine and configured to compress the scavenging gases.

[0016] The internal combustion engine preferably includes a plurality of cylinders, such as 4 to 14 cylinders. The internal combustion engine may further include a cylinder head, an exhaust valve, a piston, a fuel valve, and a scavenging inlet for each of the plurality of cylinders.

[0017] The internal combustion engine can be any type of two-stroke, single-flow scavenging crosshead internal combustion engine, such as a single-fuel or dual-fuel engine. The fuel supply system can be configured to inject liquid fuel and / or fuel gas into the cylinders. The liquid fuel can be any type of liquid fuel, such as heavy fuel oil or marine diesel. The fuel gas can be any type of fuel gas, such as liquefied natural gas (LNG), methane, ammonia, ethane, and liquefied petroleum gas (LPG). The engine can have a Diesel cycle and / or an Otto cycle. As an example, if the engine is a dual-fuel engine, it can have an Otto cycle mode when operating with fuel gas and a Diesel cycle mode when operating with alternative fuels (such as heavy fuel oil or marine diesel).

[0018] The shaft-driven generator control system may include a processing unit. The processing unit can be any processing unit, such as a central processing unit (CPU), graphics processing unit (GPU), microcontroller unit (MCU), field-programmable gate array (FPGA), or any combination thereof. The processing unit may include one or more physical processors and / or may be a combination of multiple individual processing units. The first time period may have a duration of at least 5 seconds or 10 seconds; that is, the shaft-driven generator control system can be configured to allow power consumption to differ from power generation for a time period of at least 5 seconds or at least 10 seconds.

[0019] The first signal can be a signal measured using a sensor. The sensor can be arranged in the first circuit or in the AC power grid connected to the first circuit. The sensor can be configured to measure the voltage at the first circuit or the AC power grid. If the voltage begins to drop, it can indicate that the power generation is too low, and correspondingly, if the voltage begins to rise, it can indicate that the power generation is too high.

[0020] A shaft-driven generator control system can be configured to change the amount of electricity generated by altering the generator torque. For example, if the demand for electricity increases, the shaft-driven generator control system can be configured to gradually increase the generator torque, and if the demand for electricity decreases, gradually decrease the generator torque.

[0021] In some embodiments, the shaft-driven generator system is configured to allow the difference between power consumption and power generation during a first time period to be at least 10% of the rated power of the shaft-driven generator.

[0022] Rated shaft generator power is the maximum power that a shaft generator can produce.

[0023] In some embodiments, the first circuit includes an AC-to-DC rectifier, a DC grid, and a DC-to-AC converter. The AC-to-DC rectifier is configured to receive an AC current at a first frequency from a shaft-driven generator, convert the received AC current into a DC current, and provide the converted DC current to the DC grid. The DC-to-AC converter is configured to receive the converted DC current from the DC grid, convert the converted DC current into an AC current with a second frequency, and provide the AC current with the second frequency to the AC grid.

[0024] In some embodiments, the shaft-driven generator system includes an additional power source configured to deliver electrical energy when power consumption exceeds the power generation of the shaft-driven generator.

[0025] Therefore, by providing an additional power source, sufficient power can be supplied to the shipboard equipment even when the power generation from the shaft generator is less than the power consumption.

[0026] The additional power source can be an energy storage device, such as a chemical battery, a supercapacitor, or a flywheel energy storage system configured to receive and transmit electrical energy. Alternatively / additionally, the additional power source can be a generator set comprising an internal combustion engine and a generator. The internal combustion engine is preferably a medium-speed or high-speed four-stroke engine that allows for rapid control of the amount of electricity generated. The generator set can be further connected to the flywheel, thereby allowing the generator set to also absorb excess electricity generated by the shaft-driven generator.

[0027] In some embodiments, the additional power source is also configured to receive electrical energy when the power generated by the shaft-driven generator exceeds the power consumption.

[0028] The auxiliary power source can be directly controlled by the shaft-driven generator control system. Alternatively, the auxiliary power source may include a dedicated control system configured to control the auxiliary power source, for example, to control the auxiliary power source to receive or transmit electrical energy. The dedicated control system can be communicatively connected to the shaft-driven generator control system and configured to receive control signals from the shaft-driven generator control system; for example, the shaft-driven generator control system can send control signals to the dedicated control system, thereby instructing the dedicated control system to control the auxiliary power source to receive or transmit electrical energy.

[0029] Alternatively / additionally, a dedicated control system can be configured to independently estimate the difference between the power generation and power consumption of the shaft-driven generator, and to control an additional power source to receive or transmit electrical energy. The dedicated control system can estimate this difference by receiving a signal corresponding to the first signal.

[0030] In some embodiments, the additional power source is capable of transmitting and / or receiving power with an effect of at least 100kW, at least 250kW, or at least 500kW.

[0031] In some embodiments, the additional power source is capable of delivering at least 0.25 kWh, 0.5 kWh, or 1 kWh without receiving power from the shaft-driven generator.

[0032] In some embodiments, the additional power source can receive at least 0.25 kWh, 0.5 kWh, or 1 kWh without supplying power to the shaft-driven generator system.

[0033] In some embodiments, the additional power source is capable of delivering at least 0.25 kWh, 0.5 kWh, or 1 kWh without receiving power from the shaft-driven generator, wherein the minimum power is at least 100 kW, at least 250 kW, or at least 500 kW.

[0034] In some embodiments, the shaft-driven generator control system is configured to receive a signal indicating the state of an additional power source and control the shaft-driven generator based on the signal. For example, the shaft-driven generator control system may be configured to receive a second signal indicating the state of an additional power source and control the shaft-driven generator based on the second signal.

[0035] Therefore, it can be ensured that the additional power source will not run out and will be available at all times.

[0036] The second signal can indicate the ability of the additional power source to supply power to the system. Additionally / alternatively, the second signal can indicate the ability of the additional power source to absorb power from the system. For example, if the additional power source is an energy storage device, the second signal can indicate the energy level of the energy storage device; for instance, if the energy storage device is a chemical battery, the energy level can be estimated by measuring the battery voltage using a voltage sensor. The shaft-driven generator control system can be configured to periodically estimate the energy level of the energy storage device and control the power generation of the shaft-driven generator based on this periodic estimation. For example, if the energy level of the energy storage device is lower than a desired target, the shaft-driven generator control system can be configured to control the shaft-driven generator to generate more power than consumed, thereby restoring the energy level of the energy storage device to the desired level. Conversely, if the energy level of the energy storage device is higher than a desired target, the shaft-driven generator control system can be configured to control the shaft-driven generator to generate less power than used, thereby utilizing the excess energy from the energy storage device.

[0037] As another example, if the additional power source is a generator set, the second signal can indicate the power output of the generator set's engine. If the generator set's engine is operating close to its rated power (maximum power), the shaft-driven generator control system can control the shaft-driven generator to increase the amount of electricity being generated. If the generator set includes a flywheel, the second signal can indicate the flywheel's speed. If the flywheel's speed is close to its maximum speed, the shaft-driven generator control system can control the shaft-driven generator to produce less electrical energy than it consumes, thereby converting the flywheel's kinetic energy into electrical energy and reducing the flywheel's speed.

[0038] In some embodiments, the additional electrical energy source is connected to the DC grid and configured to receive electrical energy from the DC grid and / or supply electrical energy to the DC grid.

[0039] Therefore, since it is not necessary to match the frequency and phase of the AC power grid, it becomes easier to receive electrical energy from the system and to supply electrical energy to the system.

[0040] In some embodiments, the DC-to-AC converter is configured to change the second frequency when the amount of power consumed is higher than and / or lower than the amount of power generated by the shaft-driven generator.

[0041] If the amount of power consumed is higher than the amount of power generated by the shaft-driven generator, the DC-to-AC converter can be configured to reduce the second frequency. Conversely, if the amount of power consumed is lower than the amount of power generated by the shaft-driven generator, the DC-to-AC converter can be configured to increase the second frequency.

[0042] In some embodiments, the shaft-driven generator control system is operatively connected to the engine fuel control system of a two-stroke single-flow scavenging crosshead internal combustion engine and is configured to receive information from and / or send information to the engine fuel control system.

[0043] In some embodiments, the shaft-driven generator control system is configured to provide information related to power demand to the engine fuel control system.

[0044] Therefore, the engine fuel control system can respond more quickly to changes in power consumption, thereby allowing the engine speed to remain more stable.

[0045] In some embodiments, the shaft-driven generator control system is configured to send a control signal to the engine fuel control system in response to a detected change in power consumption. This control signal instructs the engine fuel control system to change the amount of fuel supplied to the cylinders before the engine fuel control system detects a difference between the nominal engine speed and the actual engine speed.

[0046] As an example, if the shaft-driven generator control system detects an increase in power consumption, it can send a control signal to the engine fuel control system, instructing it to increase the amount of fuel supplied to the cylinders before detecting a decrease in actual engine speed. Conversely, if the shaft-driven generator control system detects a decrease in power consumption, it can send a control signal to the engine fuel control system, instructing it to decrease the amount of fuel supplied to the cylinders before detecting an increase in actual engine speed.

[0047] In some embodiments, the shaft-driven generator control system is configured to receive information related to engine speed, and wherein the shaft-driven generator control system is further configured to control the power generation of the shaft-driven generator based on the received information related to engine speed.

[0048] In some embodiments, information related to engine speed enables the shaft-driven generator control system to determine the difference between the nominal engine speed and the actual engine speed, and wherein the shaft-driven generator control system is configured to control the shaft-driven generator to reduce power generation when the actual engine speed is lower than the nominal engine speed and to increase power generation when the actual engine speed is higher than the nominal engine speed.

[0049] Therefore, shaft-driven generator systems can be directly used to stabilize the speed of 2-stroke engines.

[0050] The nominal engine speed is the desired engine speed selected by the engine operator. If an increase in power generation results in generating more power than is used, the excess power can be transferred to an additional power source as described above and / or to one or more damping resistors to be converted into heat. Conversely, if a decrease in power generation results in generating less power than is used, an additional power source can be used to deliver additional electrical energy.

[0051] According to a second aspect, the present invention relates to a propulsion and power generation combined system for propelling a ship and generating electrical energy, the propulsion and power generation combined system comprising a shaft-driven generator system as disclosed with respect to the first aspect and a two-stroke single-flow scavenging crosshead internal combustion engine, the two-stroke single-flow scavenging crosshead internal combustion engine comprising an engine shaft, at least one cylinder, a cylinder head, a piston, an engine fuel control system, a fuel supply system, and a scavenging system, the cylinder having cylinder walls, the cylinder head disposed on top of the cylinder and having an exhaust valve, the piston being movably disposed within the cylinder along a central axis between bottom dead center and top dead center, the scavenging system having a scavenging inlet disposed at the bottom of the cylinder, the fuel supply system being configured to inject fuel into a main combustion chamber defined between the piston and the cylinder head based on a control signal provided by the engine fuel control system, wherein the shaft-driven generator is connected to the shaft of the two-stroke single-flow scavenging crosshead internal combustion engine.

[0052] In some embodiments, the shaft-driven generator control system is operatively connected to the engine fuel control system of a two-stroke single-flow scavenging crosshead internal combustion engine and is configured to receive information from or send information to the engine fuel control system, wherein the shaft-driven generator control system is configured to provide information related to power demand to the engine fuel control system, and the engine fuel control system is further configured to control the amount of fuel injected into the main combustion chamber based on the information related to power demand.

[0053] Therefore, the engine fuel control system can adapt to changes in electricity demand more quickly, thus allowing for more stable control of engine speed.

[0054] Different aspects of the invention can be implemented in various ways, including, for example, shaft-driven generator systems and propulsion and power generation combined systems, each producing one or more of the benefits and advantages described in conjunction with at least one of the aspects described above, and each having one or more preferred embodiments corresponding to the preferred embodiments described in conjunction with at least one of the aspects described above and / or disclosed in the dependent claims. Furthermore, it will be understood that embodiments described in conjunction with one of the aspects described herein can be equally applied to the other aspects. Attached Figure Description

[0055] The above and / or additional objects, features, and advantages of the invention will be further illustrated by the following illustrative and non-limiting detailed description of embodiments of the invention with reference to the accompanying drawings, in which:

[0056] Figure 1 A two-stroke engine and a generator system for generating electrical energy according to an embodiment of the present invention are illustrated schematically.

[0057] Figure 2 A schematic diagram of a propulsion and power generation system is shown. Detailed Implementation

[0058] In the following description, reference is made to the accompanying drawings, which illustrate by way of showing how the invention can be practiced.

[0059] Figure 1A two-stroke engine 100 and a generator system 190 for generating electrical energy are schematically illustrated according to an embodiment of the present invention. The engine 100 is a two-stroke, single-flow scavenging crosshead internal combustion engine 100. The engine 100 includes a scavenging system 111, an exhaust gas receiver 108, a fuel supply system, an engine shaft 151, and a turbocharger 109. The engine has a plurality of cylinders 101 (only a single cylinder is shown in the cross-section). Each cylinder 101 has a cylinder wall 115 and includes a scavenging inlet 102 disposed at the bottom of the cylinder 101. The engine further includes a cylinder head 112 and a piston 103 for each cylinder. The cylinder head 112 is disposed on top of the cylinder 101 and has an exhaust valve 104. The piston 103 is movably disposed within the cylinder along a central axis 113 between bottom dead center and top dead center. The fuel supply system may optionally include one or more fuel gas valves 105 (shown schematically only) configured to inject fuel gas into cylinder 101 during the compression stroke, such that the fuel gas can be mixed with scavenging air and the mixture of scavenging air and fuel gas can be compressed before ignition. The fuel gas valves 105 may be at least partially disposed in the cylinder wall, between cylinder head 112 and scavenging air inlet 102. The engine may further optionally include an external ignition unit 114, such as an ignition injector configured to inject self-igniting fuel. The ignition injector may be configured to inject self-igniting fuel directly into the combustion chamber, a pre-combustion chamber assembly, or a pre-combustion chamber disposed in cylinder head 112. The pre-combustion chamber assembly may include an inner pre-combustion chamber and an outer pre-combustion chamber, the outer pre-combustion chamber communicating with the main combustion chamber 150 through a first opening and fluidly connected to the inner pre-combustion chamber, wherein the inner pre-combustion chamber is provided with the ignition injector. Scavenging inlet 102 is fluidly connected to the scavenging system. Piston 103 is shown in its lowest position (bottom dead center). Piston 103 has a piston rod connected to a crankshaft (not shown). Fuel gas valve 105 is configured to inject fuel gas into the cylinder during the compression stroke, allowing the fuel gas to mix with the scavenging gas and allowing the mixture of scavenging gas and fuel gas to be compressed before ignition. Scavenging system 111 includes scavenging receiver 110 and air cooler 106. Instead of or attached to fuel gas valve 105, fuel supply system may optionally include one or more fuel injectors 116 disposed in cylinder head 112, which are configured to inject fuel under high pressure, such as high-pressure gas or self-igniting liquid fuel, at the end of the compression stroke. If the fuel supply system includes only one or more fuel injectors 116 configured to inject self-igniting liquid fuel, an external ignition unit 114 is not required. Engine 100 can be a dual-fuel engine having an Otto cycle mode when using fuel gas and a Diesel cycle mode when using alternative fuels (such as heavy fuel oil or marine diesel).However, engine 100 may also be a single fuel system with only a Diesel cycle mode. Engine 100 further includes an engine fuel control system 160. The fuel supply system is configured to inject fuel into the main combustion chamber defined between piston 103 and cylinder head 112 based on control signals provided by the engine fuel control system 160, thereby controlling the speed and power output of engine 100. Engine control system 160 may receive a nominal engine speed 161. The nominal engine speed is typically set by the engine operator. Engine fuel control system 160 may receive, for example, sensor signals indicating the actual engine speed from a sensor used to measure the speed of engine shaft 151. Engine fuel control system 160 may be configured to control the fuel supply system to increase the amount of fuel injected into the combustion chamber when the actual engine speed is lower than the nominal engine speed 161, and to decrease the amount of fuel injected into the main combustion chamber when the actual engine speed is higher than the nominal engine speed 161. The shaft-driven generator system 190 includes: a shaft-driven generator 170 configured to generate AC current with a first frequency, the first frequency depending on the revolutions per minute (RPM) of the shaft 151; a first circuit 172 for converting the AC current from the first frequency to a second frequency; and a shaft-driven generator control system 171 configured to receive a first signal 182 indicating power consumption. The shaft-driven generator control system 171 is operatively connected to the shaft-driven generator 170 and configured to control the power generation of the shaft-driven generator 170 based on the first signal 182. The first circuit 171 is configured to supply power to an AC grid 173, where the power can be used by shipboard equipment such as propellers, pumps, gas reliquefaction machinery, refrigerated containers, and general marine power-consuming loads. The shaft-driven generator control system 171 is configured to allow power consumption to differ from power generation for a period of at least 2 seconds. Therefore, by introducing an intentional hysteresis in the shaft-driven generator control system, instability effects caused by variations in power consumption can be significantly reduced. This allows the shaft-driven generator to produce more power without causing the 2-stroke engine to become unstable to unacceptable levels. The first signal 182 is shown as originating from the first circuit 172, for example, from a sensor arranged to be connected to the first circuit 170. However, the first signal 182 could originate from other parts of the system, such as from the AC power grid 173.

[0060] Figure 2A schematic diagram of a propulsion and power generation system 199 for propelling a ship and generating electrical energy is shown. System 199 includes a shaft-driven generator system 190 and a two-stroke, single-flow scavenging crosshead internal combustion engine 100. Engine 100 includes an engine shaft, at least one cylinder, a cylinder head, a piston, an engine fuel control system 160, a fuel supply system, and a scavenging system. The cylinder has cylinder walls, the cylinder head is disposed on top of the cylinder and has an exhaust valve, and the piston is movably disposed within the cylinder along a central axis between bottom dead center and top dead center. The scavenging system has a scavenging inlet disposed at the bottom of the cylinder. The fuel supply system is configured to inject fuel into the main combustion chamber defined between the piston and the cylinder head based on a control signal provided by the engine fuel control system 160. The shaft-driven generator system 190 includes: a shaft-driven generator 170 configured to generate AC current having a first frequency, the first frequency depending on the RPM of the shaft; a first circuit 172 for converting the AC current from the first frequency to a second frequency; and a shaft-driven generator control system 171 configured to receive a first signal 182 indicating power consumption. The shaft-driven generator 170 is connected to an engine shaft 151. The engine shaft is further connected to a propeller (not shown). The engine shaft can be connected to the propeller via a clutch (not shown). The shaft-driven generator control system 171 is operatively connected to the shaft-driven generator 170 and configured to control the power generation of the shaft-driven generator 170 based on the first signal 182 (e.g., by providing a control signal 185 to the shaft-driven generator 170). The shaft-driven generator control system 171 is configured to allow power consumption to differ from power generation for a period of at least 2 seconds. The first circuit 172 includes an AC-to-DC rectifier 174, a DC grid 175, and a DC-to-AC converter 176. AC-to-DC rectifier 174 is configured to receive AC current at a first frequency from shaft-driven generator 170, convert the received AC current into DC current, and provide the converted DC current to DC grid 175. DC-to-AC converter 176 is configured to receive the converted DC current from DC grid 175, convert the DC current into AC current at a second frequency, and provide the AC current at the second frequency to AC grid 173, where the current can be used by AC-consuming device 178. A first signal can be recorded by sensor 180 that senses power consumption. As an example, sensor 180 can be a voltage sensor for measuring the voltage of DC grid 175, indicating that power generation is too low if the voltage begins to drop, and correspondingly, indicating that power generation is too high if the voltage begins to rise. Shaft-driven generator system 190 includes an auxiliary power source 177 configured to deliver energy when power consumption exceeds the power generation of shaft-driven generator 170. Auxiliary power source 177 is connected to DC grid 175.The auxiliary power source 177 can be an energy storage device, such as a chemical battery, a supercapacitor, or a flywheel energy storage system configured to receive and transmit electrical energy. Alternatively / additionally, the auxiliary power source 177 can be a generator set including an auxiliary internal combustion engine and a generator. The auxiliary internal combustion engine is preferably a medium-speed or high-speed four-stroke engine that allows for rapid control of the amount of electricity generated. The generator set can be further connected to the flywheel, thereby allowing the generator set to also absorb excess electricity generated by the shaft-driven generator 170, i.e., the generator of the generator set can also be used as an electric motor to accelerate the flywheel. The auxiliary power source 177 can be configured to receive electrical energy when the power generation exceeds the power consumption. The shaft-driven generator control system 171 is configured to receive a second signal 183 indicating the state of the auxiliary power source 177 and to control the shaft-driven generator based on the second signal 183. The second signal 183 can indicate the ability of the auxiliary power source 177 to provide power to the system. Additionally / alternatively, the second signal 183 can indicate the ability of the auxiliary power source 177 to absorb power from the system. As an example, if the auxiliary power source 177 is an energy storage device, the second signal 183 can indicate the energy level of the energy storage device. For example, if the energy storage device is a chemical battery, the energy level can be estimated by measuring the battery voltage using voltage sensor 181. The shaft-driven generator control system 171 can be configured to control the shaft-driven generator 170 based on the second signal 183, such that the auxiliary power source 177 can deliver a predetermined amount of power at any time, for example, delivering at least 0.25 kWh, 0.5 kWh, or 1 kWh without receiving power from the shaft-driven generator 170. Additionally / alternatively, the shaft-driven generator control system 171 can be configured to control the shaft-driven generator 170 based on the second signal 183, such that the auxiliary power source 177 can receive a predetermined amount of power at any time, for example, receiving at least 0.25 kWh, 0.5 kWh, or 1 kWh without supplying power to the DC grid 175. The shaft-driven generator control system 171 is operatively connected to the engine fuel control system 160 and configured to receive and / or send information to the engine fuel control system 160. Therefore, the engine fuel control system can respond more quickly to changes in power consumption, thereby maintaining a more stable engine speed. The shaft-driven generator control system can be configured to provide the engine fuel control system 160 with information related to power demand. The shaft-driven generator control system 171 can be configured to receive information related to engine speed. The shaft-driven generator control system 171 can be configured to control the power generation of the shaft-driven generator 170 based on the received information related to engine speed. The information related to engine speed allows the shaft-driven generator control system 171 to determine the difference between the nominal engine speed and the actual engine speed.The shaft-driven generator control system can be configured to control the shaft-driven generator 170 to reduce power generation when the actual engine speed is lower than the nominal engine speed, and to increase power generation when the actual engine speed is higher than the nominal engine speed. Therefore, the shaft-driven generator system can be directly used to stabilize the speed of a 2-stroke engine.

[0061] While some embodiments have been described in detail and illustrated, the invention is not limited thereto, but can be practiced in other ways within the scope of the subject matter defined in the appended claims. Specifically, it should be understood that other embodiments can be utilized and structural and functional changes can be made without departing from the scope of the invention.

[0062] In an apparatus claim that enumerates several means, some of these means may be implemented by one and the same hardware. The mere fact that certain measures are recited in mutually different dependent claims or described in different embodiments does not indicate that combinations of these measures cannot be advantageously used.

[0063] It should be emphasized that, when used in this specification, the term "comprising / including" is used to indicate the presence of the stated features, integers, steps, or components, but does not exclude the presence or addition of one or more other features, integers, steps, components, or groups thereof.

Claims

1. A shaft-driven generator system for use with a two-stroke, single-flow scavenging crosshead internal combustion engine, the two-stroke, single-flow scavenging crosshead internal combustion engine comprising an engine shaft connected to a propeller of a ship, at least one cylinder, a cylinder head, a piston, an engine fuel control system, a fuel supply system, and a scavenging system, the cylinder having cylinder walls, the cylinder head disposed on top of the cylinder and having an exhaust valve, the piston being movably disposed within the cylinder along a central axis between bottom dead center and top dead center, the scavenging system having a scavenging inlet disposed at the bottom of the cylinder, and the fuel supply system being configured to inject fuel into a main combustion chamber defined between the piston and the cylinder head based on a control signal provided by the engine fuel control system, wherein, The shaft-driven generator system includes: A shaft-driven generator configured to generate AC current having a first frequency, the first frequency depending on the RPM of the shaft; a first circuit for converting the AC current from the first frequency to a second frequency; and a shaft-driven generator control system configured to receive a first signal indicating power consumption. The characteristic is that the shaft-driven generator control system is operably connected to the shaft-driven generator and configured to control the power generation of the shaft-driven generator based on the first signal, and The shaft-driven generator control system is configured to allow power consumption to differ from power generation for a first time period of at least 2 seconds. The engine fuel control system is configured to maintain the engine speed at the nominal engine speed by increasing the amount of fuel injected into the combustion chamber when the actual engine speed is lower than the nominal engine speed, and decreasing the amount of fuel injected into the main combustion chamber when the actual engine speed is higher than the nominal engine speed. The selection of the nominal engine speed is independent of power consumption. The shaft-driven generator system also includes an auxiliary power source configured to deliver electrical energy when power consumption is higher than the power generation of the shaft-driven generator, thereby allowing power consumption to differ from the power generation of the shaft-driven generator.

2. The shaft-driven generator system according to claim 1, wherein, The first circuit includes an AC-to-DC rectifier, a DC grid, and a DC-to-AC converter. The AC-to-DC rectifier is configured to receive AC current at the first frequency from the shaft-driven generator, convert the received AC current into DC current, and provide the converted DC current to the DC grid. The DC-to-AC converter is configured to receive the converted DC current from the DC grid, convert the converted DC current into AC current at the second frequency, and provide the AC current at the second frequency to the AC grid.

3. The shaft-driven generator system according to claim 1, wherein, The additional power source is capable of delivering at least 0.25 kWh, 0.5 kWh, or 1 kWh without receiving power from the shaft-driven generator.

4. The shaft-driven generator system according to claim 2, wherein, The additional power source is connected to the DC grid and is configured to receive electrical energy from the DC grid and / or supply electrical energy to the DC grid.

5. The shaft-driven generator system according to any one of claims 1 to 2, wherein, The shaft-driven generator control system is operatively connected to the engine fuel control system of the two-stroke single-flow scavenging crosshead internal combustion engine and is configured to receive information from and / or send information to the engine fuel control system.

6. The shaft-driven generator system according to claim 5, wherein, The shaft-driven generator control system is configured to provide the engine fuel control system with information related to power demand.

7. The shaft-driven generator system according to claim 5, wherein, The shaft-driven generator control system is configured to receive information related to engine speed, and further configured to control the power generation of the shaft-driven generator based on the received information related to engine speed.

8. The shaft-driven generator system according to claim 7, wherein, The information related to engine speed enables the shaft-driven generator control system to determine the difference between the nominal engine speed and the actual engine speed, and wherein the shaft-driven generator control system is configured to control the shaft-driven generator to reduce power generation when the actual engine speed is lower than the nominal engine speed, and to increase power generation when the actual engine speed is higher than the nominal engine speed.

9. A propulsion and power generation combined system for propelling a ship and generating electrical energy, the propulsion and power generation combined system comprising a shaft-driven generator system according to any one of claims 1 to 2, and a two-stroke single-flow scavenging crosshead internal combustion engine, the two-stroke single-flow scavenging crosshead internal combustion engine comprising an engine shaft connected to a propeller, at least one cylinder, a cylinder head, a piston, an engine fuel control system, a fuel supply system, and a scavenging system, the cylinder having cylinder walls, the cylinder head disposed on top of the cylinder and having an exhaust valve, the piston being movably disposed within the cylinder along a central axis between bottom dead center and top dead center, the scavenging system having a scavenging inlet disposed at the bottom of the cylinder, the fuel supply system being configured to inject fuel into a main combustion chamber defined between the piston and the cylinder head based on a control signal provided by the engine fuel control system, wherein, The shaft-driven generator is connected to the shaft of the two-stroke, single-flow scavenging crosshead internal combustion engine.

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