Power generation system

Abstract

To prevent failure of each generator at the time of switching a target frequency in a power generation system having a plurality of generators.SOLUTION: A power generation system includes: a plurality of generators 3; and a control part 1 that controls the generators 3 so that an output frequency of each of the generators 3 becomes a predetermined target frequency. The control part 1 can switch a target frequency 14 between a first frequency F1 and a second frequency F2 smaller than the first frequency F1. When an actual load power of each generator 3 reaches a starting point, the control part 1 increases the number of generators 3 to be operated. A starting point K2 when the target frequency 14 is the second frequency F2 is smaller than a starting point K1 when the target frequency 14 is the first frequency F1.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] A ship is equipped with a large number of electrical devices such as electric pumps, ventilators, etc. To supply power to these electrical devices, the ship is usually equipped with a generator driven by a power-generating engine (see, for example, Patent Document 1 below).

[0003] Normally, the output power of a generator is set with a margin to ensure that all electrical equipment operates normally under any conditions. Therefore, under normal operating conditions, each electrical equipment operates with more output than necessary. In order to optimize the output of each electrical equipment, it is effective to lower the frequency of the electricity supplied to each electrical equipment.

[0004] For example, if an inverter is provided for each electrical device and the output of the electrical device is optimized according to the situation, power consumption can be reduced, which makes it possible to reduce the fuel supplied to the generator engine and save energy. However, if an inverter is provided for each of the many electrical devices installed on a ship, costs will rise and control will become complicated.

[0005] Another method, for example, in Patent Document 1 listed below, is to switch the generator output frequency between the normal frequency (60 Hz) and a lower energy-saving frequency (57 Hz). Lowering the generator output frequency reduces the power consumption of each electrical device, which in turn reduces the demand for electricity on board the ship, making it possible to reduce the fuel used by the engine that drives the generator and thereby achieving energy conservation. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-12738 Summary of the Invention [Problem to be solved by the invention]

[0007] Incidentally, the power generation system described above often has multiple generators, and switches the number of generators in operation depending on the total power usage. For example, as shown in Figure 5, when the total power usage is low, only one generator is operated. Then, when the total power usage increases and the actual load power of that generator reaches a preset starting point K, the number of operating generators is increased by one to two. This causes the actual load power of each generator to decrease. Thereafter, when the total power usage increases further and the actual load power of each operating generator reaches starting point K, another generator is added to the operating system to make three. Note that starting point K is set to a value lower than the rated power Q of each generator.

[0008] In a power generation system such as that described above, if the output frequency of a generator can be switched between a normal frequency (60 Hz) and an energy-saving frequency (57 Hz) as in Patent Document 1, the output frequency may be switched while the generator is operating. For example, as shown by the dashed-dotted line in Figure 6, when only one generator is operating at energy-saving frequency F2', if the output frequency is switched from energy-saving frequency F2' to normal frequency F1', the actual load power of that generator will rise sharply. For example, if the frequency is switched from F2' to F1' when the actual load power of that generator is sufficiently smaller than the rated power Q (when the total power usage is P1), the actual load power of each generator will rise as shown by arrow A, but will not reach starting point K1', so there is no problem. On the other hand, if the frequency is switched from F2' to F1' when the actual load power of the generator reaches the starting point K1' or just before that (when the total power usage is P2), the actual load power of each generator will rise as shown by arrow B and exceed the rated power Q, causing the load on the generator to become excessive, which could result in the generator breaking down.

[0009] SUMMARY OF THE INVENTION It is therefore an object of the present invention to prevent generator failures when switching target frequencies in a power generation system having a plurality of generators. [Means for solving the problem]

[0010] In order to solve the above problem, the present invention provides a power generation system having a plurality of generators and a control unit that controls the generators so that the output frequency of each generator becomes a predetermined target frequency, wherein the control unit is capable of switching the target frequency between a first frequency F1 and a second frequency F2 that is lower than the first frequency F1, and the control unit increases the number of generators in operation when the actual load power of each generator reaches a starting point, and the starting point K2 when the target frequency is the second frequency F2 is lower than the starting point K1 when the target frequency is the first frequency F1.

[0011] In this way, in the present invention, the starting point K2 when operating at the relatively low second frequency F2 is set to be smaller than the starting point K1 when operating at the relatively high first frequency F1. As a result, even if the target frequency is switched from the second frequency F2 to the first frequency F1 when the actual load power of the generator operating at the second frequency F2 approaches the starting point K2, the actual load power of the generator is unlikely to exceed the starting point K1, which is larger than the starting point K2, and breakdown of the generator can be prevented.

[0012] In the power generation system, it is preferable that the difference between the starting point K2 and the starting point K1 is equal to or greater than the increase in the actual load power of each generator when the target frequency is switched from the second frequency F2 to the first frequency F1. Specifically, the control unit sets K2≦K1·(F2 / F1) 3 It is preferable to set the starting point K2 so as to satisfy the following. [Effects of the Invention]

[0013] As described above, according to the power generation system of the present invention, a situation in which the actual load power of the operating generator becomes excessive when the target frequency is switched can be avoided, thereby preventing breakdown of the generator. [Brief explanation of the drawings]

[0014] [Figure 1]1 is a block diagram of a power generation system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram of a control unit of the power generation system of FIG. [Figure 3] 2 is a graph showing the relationship between the total power consumption in the power generation system of FIG. 1 and the actual load power per generator in operation. [Figure 4] 10 is a graph showing the relationship between the total power consumption and the actual load power per generator during operation in a power generation system according to another embodiment of the present invention. [Figure 5] 1 is a graph showing the relationship between the total power consumption and the actual load power per generator during operation in a conventional power generation system. [Figure 6] 6 is a graph showing the relationship between the total power consumption and the actual load power per generator in operation when the frequency is switched in the power generation system of FIG. 5. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] A power generation system according to one embodiment of the present invention is mounted on a ship, and as shown in Fig. 1, includes a control unit 1, a prime mover 2, a generator 3, a switchboard 4, and electrical equipment 5. This power generation system has a plurality of generators 3 and prime movers 2, and each generator 3 is driven by a corresponding prime mover 2. This marine power generation system also includes a plurality of electrical equipment 5. The electrical equipment 5 is connected to the main bus of the switchboard 4 without going through a frequency control device such as an inverter, and may include, for example, an electric pump for supplying lubricating oil and cooling water to machinery mounted on the ship (such as a main engine that drives a propulsion propeller), a ventilator for ventilating and air-conditioning the interior of the ship, lighting inside the ship, or a drive motor for operating the bow thruster.

[0017] The prime mover 2 has a generator engine 2a and a governor 2b. The generator engine 2a uses, for example, gas fuel or liquid fuel as fuel. The governor 2b controls the rotation speed of the generator engine 2a based on instructions from the control unit 1. In this embodiment, the governor 2b has a governor motor that adjusts the amount of fuel supplied to the generator engine 2a. When the governor 2b increases the fuel supplied to the generator engine 2a, the rotation speed of the generator engine 2a increases, and when the governor 2b decreases the fuel supplied to the generator engine 2a, the rotation speed of the generator engine 2a decreases.

[0018] The generator 3 has a rotor and a stator, and when the rotor is rotated, electricity is generated in a coil provided on the stator. The rotor of the generator 3 is connected to the output shaft of the generator engine 2a, and they rotate integrally.

[0019] The switchboard 4 supplies the power generated by the generator 3 to each electrical device 5 via a bus. The switchboard 4 has a frequency measuring unit that measures the frequency (actual frequency) of the electricity flowing through the bus, and information on the actual frequency measured by this frequency measuring unit is transmitted to the control unit 1.

[0020] The rotation speed of the generator 3 is equal to the rotation speed of the generator engine 2a, and the rotation speed of the generator engine 2a is proportional to the frequency (output frequency) of the electricity generated by the generator 3. Furthermore, the output frequency of the generator 3 is equal to the frequency (actual frequency) of the electricity flowing through the bus bar of the switchboard 4. Therefore, the actual frequency can be measured by the frequency measurement unit provided in the switchboard 4 as described above, or can be calculated from the rotation speed of the generator engine 2a, the rotation speed or output frequency of the generator 3. In this embodiment, a frequency measurement unit is provided that measures the output frequency of the generator 3, and the frequency measured by the frequency measurement unit of the switchboard 4 and the output frequency measured by the frequency measurement unit of the generator 3 are transmitted to the control unit 1.

[0021] The marine power generation system is provided with a detection unit 6 that detects the operating status of each electrical device 5. For example, if the electrical device 5 is an electric pump, the detection unit 6 may be provided with 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. If the electrical device 5 is a ventilator, the detection unit 6 may be provided with 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 instrument that measures the air properties in that area (e.g., CO concentration, NOx concentration, combustible gas concentration, etc. in that area).

[0022] The control unit 1 controls the output frequency of the generator 3 by controlling the rotation speed of the prime mover 2. As shown in Fig. 2, the control unit 1 of this embodiment has a memory 1a, an output unit 1b, and a target frequency setting unit 1c.

[0023] The memory 1a stores an actual load factor 11, a target load factor 12, an actual frequency 13, and a target frequency 14.

[0024] The actual load factor 11 is the ratio of the current output to the individual rated output of each generator 3. For example, the output voltage and current of each generator 3 are measured at short time intervals, and the actual load factor 11 is calculated from these values. This actual load factor 11 is stored in the memory 1a, or the value of the actual load factor 11 already stored in the memory 1a is updated.

[0025] The target load factor 12 is a target value of the load factor of each generator 3, and is input by an input means provided in the control unit 1. The target load factor 12 is set appropriately according to the capacity of each generator 3, etc.

[0026] The actual frequency 13 is the actual frequency of the electricity generated by the generator 3. In this embodiment, the frequency of the electricity flowing through the bus is measured by a frequency measuring unit provided in the switchboard 4, and this frequency is stored in the memory 1a as the actual frequency 13, or the value of the actual frequency 13 already stored in the memory 1a is updated.

[0027] The target frequency 14 is a target value of the output frequency of the generator 3. In this embodiment, the frequency set by the target frequency setting unit 1c is stored as the target frequency 14 in the memory 1a.

[0028] The output unit 1b calculates a command value (driving time) for the governor 2b of the prime mover 2 based on the actual load rate 11, target load rate 12, actual frequency 13, and target frequency 14 stored in the memory 1a, and outputs the value to the governor 2b. That is, while monitoring the actual load rate 11 and the actual frequency 13, the output unit 1b drives the governor 2b of the prime mover 2 so that the actual load rate 11 and the actual frequency 13 approach the target load rate 12 and the target frequency 14, respectively.

[0029] In this embodiment, the target frequency 14 is not a fixed value but can be switched by the target frequency setting unit 1c. The target frequency 14 is set, for example, based on the operating status of each electrical device 5 detected by the detection unit 6. Specifically, if the discharge pressure, discharge flow rate, fluid flow rate, etc. of the electric pump measured by the detection unit 6, or the temperature, air pressure, air properties, etc. of the area where the ventilator is installed are within a predetermined range, it is determined that each electrical device 5 is operating normally, and a lower limit frequency (57 Hz) as the second frequency is set as the target frequency 14. On the other hand, if the values ​​detected by the detection unit 6 are outside the predetermined range, it is determined that each electrical device 5 is not operating normally (there is a shortage of power supply), and the normal frequency (60 Hz) as the first frequency is set as the target frequency 14. Note that the target frequency 14 may be automatically set by the target frequency setting unit 1c as described above, or, for example, a crew member may input either the normal frequency or the low frequency as the target frequency 14 into the control unit 1.

[0030] In this embodiment, the number of generators 3 to be operated is set based on the total power usage of all the electrical devices 5 (i.e., the sum of the rated power of the loads applied to each electrical device 5). Specifically, as shown in Fig. 3, when the total power usage is small, only one generator 3 is operated, and when the actual load power of that generator 3 reaches a predetermined starting point, the number of operating generators 3 is increased by one to two. When the total power usage further increases and the actual load power of each generator 3 reaches a predetermined starting point, the number of operating generators 3 is increased by another one to three.

[0031] In this embodiment, the starting point is set to be different when the target frequency is the normal frequency (60 Hz) and when it is a low frequency (57 Hz). Specifically, when the target frequency is the normal frequency F1 (see the solid line), the starting point is set to K1, which is smaller than the rated power Q of each generator 5, and when the target frequency is the low frequency F2 (see the dashed dotted line), the starting point is set to K2, which is smaller than K1.

[0032] By operating the generator 3 with the target frequency set to the low frequency F2, the output of each generator engine 2a is lower than when the target frequency is set to the normal frequency F1, so the amount of fuel supplied to each generator engine 2a is reduced, thereby achieving energy savings.

[0033] For example, if the target frequency is switched from the low frequency F2 to the normal frequency F1 just before the actual load power of a generator 3 operating at the low frequency F2 reaches the starting point K2, the output of each generator 3 will increase, and the actual load power of each generator 3 may exceed the starting point K2 (see arrow C). In this embodiment, the starting point K2 when the target frequency is the low frequency F2 is smaller than the starting point K1 when the target frequency is the normal frequency F1. Therefore, even if the actual load power of a generator 3 exceeds the starting point K2, it is less likely to exceed the starting point K1, and therefore it is possible to prevent an excessive load from being applied to the generator 3.

[0034] In particular, in this embodiment, the difference between the starting point K2 and the starting point K1 is set to be equal to or greater than the increase in the actual load power of each generator 3 when the target frequency is increased from the low frequency F2 to the normal frequency F1. Specifically, the starting point K2 is set to satisfy the following condition: K2≦K1·(F2 / F1) 3 As a result, even if the target frequency is switched from the low frequency F2 to the normal frequency F1 at the moment when the actual load power of the generator 3 in operation reaches the starting point K2, the actual load power of the generator 3 will not exceed the starting point K1, so it is possible to reliably avoid a situation in which an excessive load is applied to the generator 3 and the generator 3 breaks down.

[0035] The present invention is not limited to the above-described embodiment. Other embodiments of the present invention will be described below, but redundant explanations of the same points as those in the above-described embodiment will be omitted.

[0036] In the above embodiment, the target frequency can be switched between two levels: a regular frequency (60 Hz) and a low frequency (57 Hz), but the present invention is not limited to this and the target frequency may be switched between three or more levels including the regular frequency. For example, Fig. 4 shows a case where the target frequency can be switched between four levels: a regular frequency F1 (e.g., 60 Hz) and lower low frequencies F2, F3, and F4 (e.g., 57 Hz, 58 Hz, and 59 Hz).

[0037] In this case, it is preferable to set the starting point according to the magnitude of the target frequency. In the illustrated example, when the target frequency is the normal frequency F1 (see solid line), the starting point is set to K1, and when the target frequency is a low frequency F2 (see dashed line), F3 (see dashed two-dot line), or F4 (see dashed three-dot line), the starting points are set to K2, K3, or K4, which are smaller than K1. In the illustrated example, K2 <K3<K4<K1とされる。

[0038] The differences between the starting points K2, K3, K4 at the low frequencies F2, F3, F4 and the starting point K1 at the normal frequency F1 are set to be equal to or greater than the increase in the actual load power of each generator 3 when the target frequency is increased from the low frequencies F2, F3, F4 to the normal frequency F1. Specifically, the starting points K2, K3, K4 are set to satisfy the following relationship: K2≦K1·(F2 / F1) 3 , K3≦K1·(F3 / F1) 3 , K4≦K1·(F4 / F1) 3 is set to satisfy

[0039] The method for setting the target frequency is not limited to the above. For example, the target frequency may be set in three or five or more stages, in addition to the two or four stages described above. The target frequency may also be set in increments of 0.5 Hz or 0.1 Hz.

[0040] The method for setting the starting point K2 when the target frequency is the low frequency F2 is not limited to the above, and other methods may be used as long as the rated power Q is not exceeded when the normal frequency is restored. [Explanation of symbols]

[0041] 1. Control section 2. Prime Mover 2a Generator engine 2b Governor 3. Generator 4 Switchboard 5. Electrical Equipment 6. Detection unit F1 First frequency (common frequency) F2 Second frequency (low frequency)

Claims

1. A plurality of generators; A power generation system having a control unit that controls each generator so that the output frequency of the generator becomes a predetermined target frequency, the control unit is capable of switching the target frequency between a first frequency F1 and a second frequency F2 that is smaller than the first frequency F1, the control unit increases the number of the generators to be operated when the actual load power of each generator reaches a starting point; A power generation system in which a starting point K2 when the target frequency is the second frequency F2 is smaller than a starting point K1 when the target frequency is the first frequency F1.

2. 2. The power generation system according to claim 1, wherein the difference between the starting point K2 and the starting point K1 is equal to or greater than the increase in actual load power of each generator when the target frequency is switched from the second frequency F2 to the first frequency F1.

3. The control unit <h2 style=";text-align:left;direction:ltr">K2≦K1・(F2 / F1)<h2 style=";text-align:left;direction:ltr"> ３ The power generation system according to claim 1 , wherein the starting point K2 is set so as to satisfy the following equation.

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