Power generation system

Abstract

To save energy by suppressing power loss and excessive fuel consumption in a power generation system having a generator driven by a prime mover which is not dedicated to power generation.SOLUTION: The power generation system includes a shaft generator 2 driven by a main engine 1, a bus 5, a frequency conversion path 15 that connects the shaft generator 2 and the bus 5 via a frequency converter 14, a bypass path 16 that is provided in parallel with the frequency conversion path 15 and connects the shaft generator 2 and the bus 5 not via the frequency converter, and a switching unit 17 that switches between a state in which the shaft generator 2 and the bus 5 are connected via the bypass path 16 and a state in which the shaft generator 2 and the bus 5 are connected via the frequency conversion path 15 according to the rotational speed of the shaft generator 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power generation system. [Background technology]

[0002] A ship may be equipped with an engine (main engine) that drives the propulsion propeller and an engine (generator engine) dedicated to generating electricity that drives a generator. When such a ship is sailing, both the main engine and the generator engine are driven. The rotation speed of the main engine varies depending on the load on the main engine. On the other hand, the rotation speed of the generator engine is kept constant, and electricity (alternating current) of a constant frequency is always supplied to the loads on the ship.

[0003] A ship like the one described above may be equipped with a shaft generator driven by the power of the main engine. In this case, while the ship is sailing, the power of the main engine drives both the propeller and the shaft generator, and the electricity generated by the shaft generator is supplied to the onboard loads. While sailing, the required electricity is relatively small and can be met solely by the power generated by the shaft generator, so the generator engine can be stopped.

[0004] While a ship is sailing, the rotation speed of the main engine fluctuates, which in turn fluctuates the rotation speed of the shaft generator driven by the main engine, causing the frequency of the AC current generated by the shaft generator to fluctuate. Therefore, when a ship has a shaft generator, the frequency of the current generated by the shaft generator is usually converted to a predetermined reference frequency (e.g., 60 Hz or 50 Hz) using a frequency converter (inverter) and then supplied to the loads on the ship via a bus (see, for example, Figure 2 of Patent Document 1 listed below). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Utility Model Application Publication No. 63-183335 Summary of the Invention [Problem to be solved by the invention]

[0006] However, as described above, supplying the power generated by the generator to the bus via a frequency converter causes a power loss of about 5 to 8%.

[0007] For example, when the frequency of the current supplied to an electric pump or a fan is lowered, the capacity of the device decreases. If power is always supplied at the standard frequency to such electrical equipment, excessive power will be supplied when the required capacity is small.

[0008] Therefore, an object of the present invention is to achieve energy conservation by suppressing power loss and excessive power supply in a power generation system having a generator driven by a prime mover that is not dedicated to power generation. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention provides a generator driven by a prime mover that is not dedicated to power generation; The busbar and a frequency conversion path connecting the generator and the bus bar via a frequency converter; a bypass path provided in parallel with the frequency conversion path and connecting the generator and the bus without passing through a frequency converter; The present invention provides a power generation system including a switching means for switching between a state in which the generator and the busbar are connected via the bypass path and a state in which the generator and the busbar are connected via the frequency conversion path in accordance with the rotation speed of the generator.

[0010] As described above, in the present invention, in a power generation system using a generator (e.g., a shaft generator) driven by a prime mover that is not dedicated to power generation (e.g., a ship's main engine), a state in which the generator and the bus are connected via a frequency converter and a state in which the generator and the bus are bypass-connected without the frequency converter are switched depending on the rotation speed of the generator. When the rotation speed of the generator is within a predetermined range, the generator and the bus are directly connected via a bypass path, thereby reducing power loss caused by the use of a frequency converter. Furthermore, when the generator and the bus are directly connected via a bypass path, the frequency of the current supplied to the bus fluctuates with fluctuations in the rotation speed of the prime mover. In this case, if the frequency of the current supplied to the bus decreases, the power supplied to the electrical devices connected to the bus decreases collectively, thereby reducing the total power consumption of these electrical devices. On the other hand, when the rotation speed of the generator is outside the predetermined range, the generator and the bus are connected via a frequency conversion path, and the frequency of the current output from the generator is adjusted by the frequency converter, thereby enabling stable power supply to the electrical devices connected to the bus.

[0011] When the prime mover is a ship's main engine, connecting the generator to the bus via a bypass path causes the rotational speed of the generator to fluctuate with fluctuations in the rotational speed of the main engine, resulting in a fluctuation in the frequency of the current supplied to the bus. Because the rotational speed of the main engine fluctuates depending on the load on the main engine (the difference between the commanded ship speed and the actual ship speed), the frequency of the current supplied to the bus fluctuates depending on the load on the main engine. In the above-described power generation system, when the generator and the bus are connected via a bypass path, the rotational speed of the main engine may be set based on the fuel efficiency of the main engine rather than based solely on the load on the main engine. For example, when the load on the main engine is constant, the rotational speed of the main engine is usually kept constant. In this case, the rotational speed of the main engine may be intentionally reduced to reduce the frequency of the current supplied to the bus, thereby improving fuel efficiency.

[0012] Among the electrical equipment constituting the onboard loads, for example, electric pumps and ventilators, output decreases when the frequency of the current supplied thereto decreases. Therefore, if the rotation speed of the main engine is reduced too much and the frequency of the current supplied to these electrical equipment becomes too low, these electrical equipment may not perform as required, and the power generation system may become unstable. Therefore, in the above-mentioned power generation system, it is preferable to set the rotation speed of the main engine while monitoring the operating status of the electrical equipment constituting the onboard loads connected to the busbar, with the generator and the busbar connected via a bypass path.

[0013] In the above-mentioned power generation system, even when the load on the main engine is constant, the main engine speed may be reduced to improve fuel efficiency or increased to meet the power demand of the onboard load and the stability of the power generation system. However, increasing or decreasing the main engine speed in this way can unintentionally change the ship's speed. Therefore, it is preferable to use a controllable pitch propeller, whose blade pitch (blade angle) can be changed, as the propulsion propeller driven by the main engine, and to maintain a constant ship speed by changing the blade angle of the controllable pitch propeller when varying the main engine speed.

[0014] When a controllable pitch propeller is used as a propulsion propeller, lowering the rotation speed of the main engine can reduce the efficiency of the controllable pitch propeller, which can actually result in worse fuel consumption. Therefore, it is preferable that the above-mentioned power generation system use information obtained from a controllable pitch propeller efficiency map to set the rotation speed of the main engine and the blade angle of the controllable pitch propeller to maximize fuel consumption.

[0015] Reducing the rotation speed of the main engine can reduce the efficiency of the generator driven by the main engine, which can actually result in worse fuel economy. Therefore, it is preferable that the above-mentioned power generation system uses information obtained from the generator efficiency map to set the rotation speed of the main engine so as to maximize fuel economy. [Effects of the Invention]

[0016] As described above, the power generation system of the present invention can reduce power loss and excessive power supply, thereby achieving energy conservation. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a block diagram showing a power generation system for a ship according to an embodiment of the present invention. [Figure 2] This is a fuel consumption map of the main engine of the above ship. [Figure 3] 1 is an efficiency map of a controllable pitch propeller of the ship. [Figure 4] 10 is an efficiency map of the shaft generator of the ship. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0019] Fig. 1 shows a power generation system according to one embodiment of the present invention. This power generation system is installed on a ship and has, as power supply sources, a shaft generator 2 driven by a prime mover (main engine 1) that is not dedicated to power generation, a generator 4 driven by a generator engine 3, and a storage battery 8. The shaft generator 2, generator 4, and storage battery 8 are connected to a bus 5.

[0020] The main engine 1 can be, for example, a diesel engine that uses heavy oil, a gas engine that uses gas fuel, or a dual-fuel engine that can selectively use heavy oil and gas fuel. The main engine 1 is connected to the propeller propeller 6 and the shaft generator 2 via a transmission 7. The transmission 7 reduces or increases the speed of the rotation output from the main engine 1. In this embodiment, the rotation of the main engine 1 is reduced by the transmission 7 and transmitted to the propeller propeller 6, and is also increased by the transmission 7 and transmitted to the shaft generator 2. A clutch 13 is provided between the reduction gear 7 and the shaft generator 2. The rotation transmitted to the shaft generator 2 rotates the rotor of the shaft generator 2, generating electric power which is supplied to the bus 5.

[0021] A diesel engine, a gas engine, or the like can be used as the power generation engine 3. The power generation engine 3 rotates and drives the rotor of a generator 4 to generate electric power, which is then supplied to a bus 5. Note that a plurality of power generation engines 3 and generators 4 may be provided. Furthermore, if not particularly required, the power generation engines 3 and generators 4 may be omitted.

[0022] The storage battery 8 is connected to the bus bar 5 via a charging / discharging panel 11. When discharging, the AC current output from the storage battery 8 is converted to DC by the charging / discharging panel 11 and supplied to the bus bar 5. When charging, the AC current supplied from the bus bar 5 is converted to DC by the charging / discharging panel 11 and charged to the storage battery 8. If not particularly required, the storage battery 8 and the charging / discharging panel 11 may be omitted.

[0023] An onboard load 21 is connected to the busbar 5. The onboard load 21 is made up of a large number of electrical devices installed inside the ship, and includes, for example, electric pumps (fuel pumps, oil pumps, cooling water pumps, etc.) installed on the main engine 1 and the generator engine 3, and ventilators installed in various areas inside the ship (for example, the engine room). In addition, an external power source, for example, an onshore power source 22, can be connected to the busbar 5. When the ship is at anchor, by connecting the onshore power source 22 to the busbar 5, power can be supplied from the onshore power source 22 to the busbar 5.

[0024] An electric motor 10 that drives a bow thruster 9 is connected to the bus bar 5. This electric motor 10 is connected to the bus bar 5 via a control panel 12. The electric power (alternating current) supplied from the bus bar 5 is supplied to the electric motor 10 after the frequency, voltage, etc. are controlled by the control panel 12.

[0025] The power generation system of this embodiment has a frequency conversion path 15 that connects the shaft generator 2 and the bus bar 5 via a frequency converter 14, a bypass path 16 that connects the shaft generator 2 and the bus bar 5 without using a frequency converter, and switching means 17 that switches between the frequency conversion path 15 and the bypass path 16. The frequency conversion path 15 and the bypass path 16 are provided in parallel.

[0026] When the ship enters or leaves port, a large amount of power is required to drive the electric motor 10 that drives the bow thruster 9, and so power is supplied from the generator 4 and the storage battery 8 to the bus 5. At this time, by setting the clutch 13 to a power cut-off state, rotation is not transmitted from the main engine 1 to the shaft generator 2, and the shaft generator 2 is stopped. The rotation speed of the generator engine 3 is set so that the frequency of the AC current output from the generator 4 becomes the reference frequency. The DC current output from the storage battery 8 is converted to AC in the charge / discharge panel 11, adjusted to the reference frequency, and supplied to the bus 5. The reference frequency is set for each ship and is, for example, 60 Hz or 50 Hz. In this embodiment, the reference frequency is 60 Hz.

[0027] When the ship is at anchor, the onshore power source 22 is connected to the bus 5, and AC current of a reference frequency is supplied from this onshore power source 22 to the bus 5. At this time, the main engine 1, the shaft generator 2, and the power-generating engine 3 are stopped. In addition, the AC current supplied from the onshore power source 22 to the bus 5 may be converted to DC by the charge / discharge panel 11 and used to charge the storage battery 8.

[0028] When the ship is sailing at a constant speed, only the onboard loads 21 need to be supplied with power, so they do not require a large amount of power. Therefore, part of the power of the main engine 1 that drives the propulsion propeller 6 is used to drive the shaft generator 2, and the power generated thereby can cover the power consumption of the onboard loads 21. At this time, the generator engine 3 and generator 4 are stopped. In addition, the storage battery 8 does not supply power to the bus bar 5. When excessive power is supplied from the shaft generator 2 to the bus bar 4, it may be converted to direct current by the charge / discharge panel 11 and charged into the storage battery 8. In this way, when the ship is sailing at a constant speed, only power generated by the shaft generator 2 is supplied to the onboard loads 21.

[0029] While a ship is sailing, even if the ship speed is constant, the rotation speed of the main engine 1 fluctuates depending on the load on the main engine 1. This causes the rotation speed of the shaft generator 2 to fluctuate, and further causes the frequency of the AC current output from the shaft generator 2 to fluctuate. Conventionally, the AC current output from the shaft generator is converted to a constant reference frequency by a frequency converter and supplied to the bus, but this causes power loss in the frequency converter. Furthermore, if power at the reference frequency is always supplied to electrical equipment such as electric pumps and ventilators, excessive power will be supplied when the required capacity is small.

[0030] In this embodiment, by connecting the shaft generator 2 and the bus 5 via a bypass path 16 that does not have a frequency converter, it is possible to avoid power loss due to the frequency converter and achieve energy savings. Furthermore, when the rotation speed of the shaft generator 2 decreases due to fluctuations in the frequency of the main engine 1 and the frequency of the current supplied to the bus 5 decreases, the power supplied to the onboard loads 21 connected to the bus 5 decreases collectively, thereby reducing the total power consumption of these electrical devices.

[0031] However, if the frequency of the current supplied to the busbar 5 is too low, the power supplied to the onboard loads 21 will be insufficient, and some electrical equipment may not be able to perform at the required capacity. For example, if the frequency of the current supplied to an electric pump is too low, the pump will not be able to discharge fluids (fuel, lubricating oil, cooling water, etc.), which could result in unstable operation of equipment to which these fluids are supplied (e.g., the main engine 1). Furthermore, if the frequency of the current supplied to a ventilator is too low, the CO2 concentration in the area where the ventilator is installed (e.g., the engine room) will increase, which could reduce the combustion efficiency of the engine installed in the engine room.

[0032] Therefore, in this embodiment, the path connecting the shaft generator 2 and the bus 5 is switched by the switching means 17 depending on the rotational speed of the shaft generator 2. Specifically, a lower limit value of the rotational speed of the shaft generator 2 (referred to as the "lower limit rotational speed") is set in advance, and if the actual rotational speed of the shaft generator 2 is equal to or higher than the lower limit rotational speed while the ship is sailing, the switching means 17 connects the shaft generator 2 and the bus 5 via the bypass path 16. This avoids power loss due to the use of a frequency converter and allows a decrease in the frequency of the current output from the shaft generator 2, thereby achieving energy savings. On the other hand, if the actual rotational speed of the shaft generator 2 is lower than the lower limit rotational speed, the switching means 17 connects the shaft generator 2 and the bus 5 via the frequency conversion path 15. In this case, the frequency of the AC current output from the shaft generator 2 is converted to a reference frequency by the frequency converter 14 and supplied to the onboard loads 21 via the bus 5. This ensures that sufficient power is supplied to the electrical equipment of the onboard loads 21, preventing the power generation system from becoming unstable due to insufficient capacity of the electrical equipment.

[0033] On the other hand, if the output frequency of the shaft generator 2 is too high, excessive power will be supplied to the electrical equipment constituting the onboard load 21, which may result in breakdown of the electrical equipment. Therefore, an upper limit value for the rotational speed of the shaft generator 2 (referred to as the "upper limit rotational speed") is set in advance, and if the actual rotational speed of the shaft generator 2 is equal to or lower than the upper limit rotational speed while the ship is sailing, the switching means 17 connects the shaft generator 2 to the bus 5 via the bypass path 16. On the other hand, if the actual rotational speed of the shaft generator 2 exceeds the upper limit rotational speed, the switching means 17 connects the shaft generator 2 to the bus 5 via the frequency conversion path 15, and the frequency of the AC current output from the shaft generator 2 is converted to a reference frequency by the frequency converter 14 and supplied to the bus 5, thereby preventing breakdown of the electrical equipment.

[0034] The lower limit frequency of the shaft generator 2 is set to a value that is equal to or greater than the lower limit of the usable frequency range set by the electrical equipment that makes up the onboard loads 21, for example. In this embodiment, the lower limit frequency of the shaft generator 2 is set to 47.5 Hz. The upper limit frequency of the shaft generator 2 is set to a value that is equal to or less than the upper limit of the usable frequency range set by the electrical equipment that makes up the onboard loads 21. The upper limit frequency is set to, for example, 1.05 times the reference frequency, and is set to 63 Hz in this embodiment.

[0035] While the ship is sailing, the rotation speed of the main engine 1 varies depending on the load applied to the main engine 1 (the difference between the ship speed command and the actual ship speed), and the rotation speed of the shaft generator 2 and further the frequency of the current supplied to the bus bar 5 vary in conjunction with this variation in the rotation speed of the main engine 1. In this embodiment, the rotation speed of the main engine 1 is set not based only on the load applied to the main engine 1, but is set based on the fuel efficiency of the main engine 1. A method for setting the rotation speed based on the fuel efficiency of the main engine 1 will be described in detail below.

[0036] Figure 2 is a fuel consumption map that shows the fuel consumption when the rotation speed and output of the main engine 1 are varied. The dotted line in the figure is a marine characteristic curve that shows the relationship between the output and rotation speed (ship speed) of the main engine 1. The solid line (ellipse) in the figure is a line that connects areas of equal fuel consumption, with fuel consumption decreasing toward the center. For example, when the output of the main engine 1 is constant, as shown by the arrow in Figure 2, if the rotation speed of the main engine 1 is set to 900 min -1 From 750 min -1 and lowering the frequency of the current supplied to the bus 5 from 60 Hz to 50 Hz will improve fuel efficiency. Therefore, according to the fuel efficiency map in Figure 2, the lower the rotation speed of the main engine 1, the better the fuel efficiency will be, so even if the load on the main engine 1 is constant, fuel efficiency can be improved by lowering the rotation speed of the main engine 1.

[0037] However, simply lowering the rotation speed of the main engine 1 may not improve fuel efficiency. Therefore, when setting the rotation speed of the main engine 1, it is preferable to consider other factors in addition to the fuel efficiency map in Figure 2. Therefore, in this embodiment, the rotation speed of the main engine 1 is set taking into consideration the following factors.

[0038] (1) Power consumption of onboard loads From the viewpoint of reducing the power consumption of the onboard loads 21, it is preferable to reduce as much as possible the rotation speed of the main engine 1, i.e., the rotation speed of the shaft generator 2. In other words, by reducing the rotation speed of the main engine 1 and lowering the frequency of the AC current output from the shaft generator 2, the power supplied to the electrical devices that make up the onboard loads 21 is reduced collectively, thereby reducing the power consumption of these electrical devices and achieving energy conservation.

[0039] In this embodiment, the rotation speed of the main engine 1 is set while monitoring the operating status of each electrical device constituting the onboard loads 21. Specifically, a detection unit is provided to detect the operating status of each electrical device constituting the onboard loads 21. For example, if the electrical device is an electric pump, the detection unit may be a pressure gauge that detects the discharge pressure of the electric pump, a flow meter that detects the discharge flow rate of the electric pump, or a thermometer that measures the temperature of the fluid (e.g., cooling water) pumped by the electric pump. Furthermore, if the electrical device is a ventilator, the detection unit may be a thermometer that measures the temperature of the area where the ventilator is installed (such as an engine room or a hold), a barometer that measures the air pressure in that area, or a measuring device that measures the air properties in that area (e.g., CO concentration, NOx concentration, combustible gas concentration, etc. in that area).

[0040] Then, while the power generated by the shaft generator 2 is supplied to the onboard loads via the bypass path 16, the detector monitors whether the electrical equipment constituting the onboard loads 21 is performing as required. Specifically, it monitors whether the discharge pressure, discharge flow rate, or fluid temperature of the electric pump, as well as the temperature, air pressure, and air properties of the area where the ventilator is installed, are within the allowable ranges. If all the electrical equipment is performing as required, the rotation speed of the main engine 1 is reduced to reduce the power consumption of the onboard loads 21.

[0041] On the other hand, if any of the electrical equipment is not performing as required, the rotation speed of the main engine 1 is increased to increase the frequency of the AC current output from the shaft generator 2. At this time, the rotation speed of the main engine 1 may be increased all at once until the frequency of the AC current output from the shaft generator 2 reaches the reference frequency (60 Hz), or the frequency may be increased stepwise or continuously while feeding back the detection results of the detection unit until all of the electrical equipment is performing as required.

[0042] (2) Efficiency of controllable pitch propellers As described above, in this embodiment, even when the load on the main engine 1 is constant, the power consumption of the onboard load 21 can be reduced by lowering the rotational speed of the main engine 1 and lowering the rotational speed of the shaft generator 2, or the power generation system can be stabilized by increasing the rotational speed of the main engine 1 and raising the rotational speed of the shaft generator 2. However, increasing or decreasing the rotational speed of the main engine 1 in this manner unintentionally changes the boat speed. Therefore, in this embodiment, a controllable pitch propeller whose blade pitch (blade angle) can be changed is used as the propulsion propeller 6, and the boat speed is maintained constant by changing the blade angle of the controllable pitch propeller when the rotational speed of the main engine 1 is varied. This makes it possible to vary the rotational speed of the main engine 1 while maintaining a constant boat speed, thereby saving energy and stabilizing the power generation system.

[0043] However, when the rotation speed of the main engine 1 is set in conjunction with the blade angle of the controllable pitch propeller as described above, lowering the rotation speed of the main engine 1 can reduce the efficiency of the controllable pitch propeller and actually increase energy consumption. Figure 3 shows a controllable pitch propeller efficiency map (CPP efficiency map), with the horizontal axis representing the rotation speed of the controllable pitch propeller and the vertical axis representing the shaft horsepower (load) of the controllable pitch propeller. The solid line in the figure shows the relationship between the rotation speed of the controllable pitch propeller and the load when the blade angle θ is a predetermined value. The dotted line in the figure shows the relationship between the rotation speed of the controllable pitch propeller and the load when the ship speed Vs is a predetermined value. In this figure, for example, when the ship speed Vs = 13.5 knots, the load on the controllable pitch propeller is minimized (i.e., efficiency is maximized) when the blade angle θ is 18° and the rotation speed is approximately 280 rpm. As such, in the CPP efficiency map, a lower rotation speed does not necessarily result in better efficiency; there are blade angles and rotation speeds at which efficiency is maximized depending on the ship speed. Therefore, in this embodiment, the rotation speed of the main engine 1 and the blade angle of the controllable pitch propeller are set using information obtained from a CPP efficiency map such as that shown in FIG. 3 (the blade angle and rotation speed at which efficiency is maximized).

[0044] (3) Shaft generator efficiency map FIG. 4 is a map showing the efficiency of the shaft generator 2, where the horizontal axis is the load applied to the shaft generator 2 and the vertical axis is the efficiency (output / input) of the shaft generator 2. According to this shaft generator efficiency map, when the rotation speed of the main engine 1 is 900 min -1 When it's 855 minutes -1 According to this efficiency map of the shaft generator 2, if the rotation speed of the main engine 1 is reduced to reduce the rotation speed of the shaft generator 2, the efficiency of the shaft generator will decrease. Therefore, in this embodiment, the rotation speed of the main engine 1 is set using information obtained from the shaft generator efficiency map as shown in FIG. 4 (the relationship between the frequency of the main engine 1 and the efficiency of the shaft generator 2).

[0045] As described above, in the power generation system of this embodiment, in order to improve the fuel efficiency of the main engine 1 with the shaft generator 2 and the bus 5 connected via the bypass path 16, the optimal rotation speed of the main engine 1 and the blade angle of the controllable pitch propeller are set based on information on (1) the power consumption of the inboard loads 21, (2) the CPP efficiency map, and (3) the shaft generator efficiency map. For example, (1) the power consumption of the inboard loads 21 decreases as the rotation speed of the main engine 1 decreases. In addition, (2) the CPP efficiency map provides the rotation speed and blade angle at which the efficiency of the controllable pitch propeller is maximized at each ship speed. Furthermore, (3) the shaft generator efficiency map shows that a higher rotation speed of the main engine 1 results in better efficiency. By performing calculations using this information, the optimal values ​​of the rotation speed of the main engine 1 and the blade angle of the controllable pitch propeller are set to achieve the best fuel efficiency under the operating conditions at that time (ship speed, load on the main engine 1, etc.). By monitoring that all electrical equipment is performing as required and controlling the rotation speed of the main engine 1 and the blade angle of the controllable pitch propeller to approach the above-mentioned optimal values, fuel-efficient operation is possible.

[0046] When the ship is sailing at its normal speed range, it is preferable that the rotation speed of the shaft generator 2 be within the above range (above the lower limit rotation speed and below the upper limit rotation speed). For example, if the ship's normal speed range is low and the rotation speed of the main engine 1 at this time is low, the rotation speed of the shaft generator 2 may fall below the lower limit rotation speed. In this case, it is preferable to increase the speed-up ratio from the main engine 1 to the shaft generator 2 by the transmission 7 and increase the rotation speed input to the shaft generator 2, thereby keeping the rotation speed of the shaft generator 2 at the normal speed range within the above range.

[0047] The present invention is not limited to the above-described embodiment. Other embodiments of the present invention will be described below, but redundant description of points similar to those of the above-described embodiment will be omitted.

[0048] For example, when setting the optimum rotation speed of the main engine 1 with the shaft generator 2 and the bus 5 connected via the bypass path 16, one or two of (1) the power consumption of the onboard loads, (2) the CPP efficiency map, and (3) the shaft generator efficiency map may be taken into consideration. Alternatively, without taking into consideration any of (1) to (3), it may be possible to monitor only whether the actual rotation speed of the shaft generator 2 is within a predetermined range (above the lower limit frequency and below the upper limit frequency).

[0049] In the above embodiment, the rotation of the main engine 1 is reduced in speed by the transmission 7 and transmitted to the propulsion propeller 6, and the rotation of the main engine 1 is increased in speed by the transmission 7 and transmitted to the shaft generator 2 (propeller rotation speed < main engine rotation speed < shaft generator rotation speed). However, this is not limiting, and for example, the rotation of the main engine 1 may be reduced in speed by the transmission 7 and transmitted to the shaft generator 2 (main engine rotation speed > shaft generator rotation speed). Furthermore, the propulsion propeller 6 and the shaft generator 2 may be directly coupled to the main engine 1, so that propeller rotation speed = main engine rotation speed = shaft generator rotation speed.

[0050] The present invention is not limited to a power generation system having a generator (shaft generator 2) whose prime mover is the ship's main engine 1, but can also be applied to a power generation system having a generator driven by a prime mover that is not dedicated to power generation. For example, the present invention can be applied to a power generation system having a generator whose prime mover is an exhaust gas turbine or a boiler. [Explanation of symbols]

[0051] 1 Main engine (prime mover) Two-shaft generator 3. Generator engine 4. Generator 5 busbar 6 propellers 7 Reducer 8. Storage battery 9 Bow Thruster 10 Electric motor 11 Charge / discharge board 12 Control Panel 13. Clutch 14 Frequency converter 15 Frequency conversion path 16 Bypass Route 17 Switching means 21 Onboard Load 22 Onshore power supply

Claims

1. generators driven by prime movers that are not dedicated to generating electricity; The busbar and a frequency conversion path connecting the generator and the bus bar via a frequency converter; a bypass path provided in parallel with the frequency conversion path and connecting the generator and the bus without passing through a frequency converter; a switching means for switching between a state in which the generator and the bus bar are connected via the bypass path and a state in which the generator and the bus bar are connected via the frequency conversion path in accordance with the rotation speed of the generator.

2. The prime mover is a main engine of a ship, The power generation system according to claim 1 , wherein the rotation speed of the main engine is set based on the fuel efficiency of the main engine with the generator and the bus bar connected via the bypass path.

3. 3. The power generation system according to claim 2, wherein the rotation speed of the main engine is set while monitoring the operating conditions of electrical equipment constituting an onboard load connected to the bus bar, with the generator and the bus bar being connected via the bypass path.

4. The propulsion propeller driven by the main engine is a controllable pitch propeller, 4. The power generation system according to claim 2 or 3, wherein when the rotation speed of the main engine is varied with the generator and the bus bar connected via the bypass path, the blade angle of the controllable pitch propeller is changed to maintain a constant boat speed.

5. 5. The power generation system according to claim 4, wherein the rotation speed of the main engine and the blade angle of the controllable pitch propeller are set using information obtained from an efficiency map of the controllable pitch propeller.

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