Method for starting the power generation system, and the power generation system

Abstract

To provide a starting method of a power generation system which can stably start an induction generator and achieves low cost, and to provide the power generation system.SOLUTION: A starting method of a power generation system includes: a turbine starting step for increasing a main flow rate which is a flow rate of an organic medium entering a turbine by adjusting an opening of a flow control valve; a power generator motoring step for switching a switching device from an inhibition state to a permission state and starting power supply from a power system to an induction generator when rotation speed of the induction generator, which increases due to execution of the turbine starting step, reaches target rotation speed; a turbine speed increase step for adjusting the opening of the flow control valve and further increasing the main flow rate after the power generator motoring step is performed; and a power generation starting step for staring supply of power to the power system by the induction generator switched to the power generator from an electric motor when the rotation speed of the induction generator exceeds synchronous rotation speed larger than the target rotation speed.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a method for starting a power generation system using an organic Rankine cycle and a power generation system.

Background Art

[0002] In the power generation system disclosed in Patent Document 1, an organic fluid evaporated in an evaporator drives a power turbine, and power generation is performed by a generator. The generated power is led to an in-ship system after the frequency is adjusted by an inverter device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above power generation system, since an inverter device is attached to the generator, there is a possibility of increasing the cost. Further, when the generator performs motoring as the power generation system is started, it is preferable that the generator stably switches from the motoring mode to the power generation mode. However, the above patent documents do not disclose a specific configuration.

[0005] An object of the present disclosure is to provide a method for starting a power generation system that can stably start an induction generator and achieve cost reduction, and a power generation system.

Means for Solving the Problems

[0006] A method for starting a power generation system according to at least one embodiment of the present disclosure is a method for starting a power generation system including a condenser, an evaporator, and a turbine, wherein the power generation system A circulation line for the organic medium, which serves as a heat transfer medium, to flow sequentially through the condenser, the evaporator, and the turbine, A bypass line for guiding the organic medium discharged from the evaporator to the condenser, bypassing the turbine, A flow control valve for adjusting the ratio between the bypass flow rate of the organic medium flowing through the bypass line and the main flow rate, which is the flow rate of the organic medium flowing into the turbine, An induction generator connected to the turbine, A switching device configured to switch between an permitted state that allows conduction between the induction generator and the power system and a prohibited state that prohibits the conduction, Equipped with, The induction generator is installed in parallel with a main generator having a larger capacity than the induction generator, which constitutes the power system. The method for starting the power generation system is as follows: A turbine startup step that increases the main flow rate by adjusting the opening degree of the flow control valve, The rotational speed of the induction generator, which increases by the execution of the turbine startup step, reaches the target rotational speed. When this is reached, the generator motoring step involves switching the switching device from the prohibited state to the permitted state and starting the supply of power from the power system to the induction generator, After the execution of the generator motoring step, a turbine speed-increasing step is performed in which the opening degree of the flow control valve is adjusted to further increase the main flow rate, A power generation start step in which, when the rotational speed of the induction generator exceeds a synchronous rotational speed greater than the target rotational speed, the induction generator, which has switched from motor mode to generator mode, starts supplying power to the power system; It is equipped with.

[0007] A power generation system according to one embodiment of this disclosure is A power generation system comprising a condenser, an evaporator, and a turbine, A circulation line for the organic medium, which serves as a heat transfer medium, to flow sequentially through the condenser, the evaporator, and the turbine, A bypass line for guiding the organic medium discharged from the evaporator to the condenser, bypassing the turbine, A flow control valve for adjusting the ratio between the bypass flow rate of the organic medium flowing through the bypass line and the main flow rate, which is the flow rate of the organic medium flowing into the turbine, An induction generator connected to the turbine, A switching device configured to switch between an permitted state that allows conduction between the induction generator and the power system and a prohibited state that prohibits the conduction, Controller and Equipped with, The induction generator is installed in parallel with a main generator having a larger capacity than the induction generator, which constitutes the power system. The aforementioned controller, A turbine startup control unit for increasing the main flow rate by controlling the opening degree of the flow control valve, When the rotational speed of the induction generator, which is increased by the opening control of the turbine starting control unit, reaches the target rotational speed, the generator motoring control unit switches the switching device from the prohibited state to the permitted state, The system includes a turbine speed-increasing control unit that, after the switching device has switched to the permitted state, adjusts the opening of the flow control valve to further increase the main flow rate so that the rotational speed of the induction generator exceeds a synchronous rotational speed greater than the target rotational speed. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide a method for starting a power generation system that can stably start an induction generator while also achieving cost reduction, as well as a power generation system itself. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of a power generation system according to one embodiment. [Figure 2] This graph schematically shows the change in rotational speed over time of an induction generator performing a startup operation according to one embodiment. [Figure 3]It is a schematic diagram showing the functional configuration of a controller according to an embodiment. [Figure 4] It is a flowchart showing a method for starting a power generation system according to an embodiment. [Figure 5] It is a flowchart showing a method for operating a power generation system when a trip occurs according to an embodiment. [Figure 6] It is a flowchart showing a method for operating a power generation system when an overload occurs according to an embodiment

Mode for Carrying Out the Invention

[0010] Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure, but are merely illustrative examples. For example, expressions representing relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial" not only strictly represent such arrangements, but also represent a state of relative displacement with tolerances or angles and distances that can obtain the same function. For example, expressions representing that things such as "identical", "equal", and "homogeneous" are in an equal state not only strictly represent an equal state, but also represent a state in which there are tolerances or differences that can obtain the same function. For example, expressions representing shapes such as a rectangular shape or a cylindrical shape not only represent shapes such as a rectangular shape or a cylindrical shape in a strictly geometric sense, but also represent shapes including concave and convex portions, chamfered portions, etc. within a range where the same effect can be obtained. On the other hand, the expressions "comprising", "including", or "having" for a component are not exclusive expressions that exclude the existence of other components. Note that the same reference numerals may be given to the same configurations and the description may be omitted.

[0011] <Overall Configuration of Power Generation System 1> Figure 1 is a schematic diagram of a power generation system 1 according to one embodiment of the present disclosure. The power generation system 1 in this example comprises a power grid 5, a main generator 2 connected to the power grid 5, an emergency generator 3 installed in parallel with the main generator 2 via the power grid 5, and a predetermined device 7 configured to receive power from the power grid 5. The predetermined device 7 can be anything that operates by the supply of power, and is one or more drive devices such as motors. The power generation system 1 may be installed on a ship or on land, but the following example illustrates a power generation system 1 installed on a ship. Note that the emergency generator 3 is not an essential component of the present disclosure.

[0012] The power system 5 includes a busbar 8 and switching devices 9A to 9C. Switching device 9A is configured to switch the conduction state between the busbar 8 and the main generator 2. Similarly, switching device 9B is configured to switch the conduction state between the busbar 8 and the emergency generator 3, and switching device 9C is configured to switch the conduction state between the busbar 8 and a predetermined device 7. Switching devices 9A to 9C are, as an example, circuit breakers configured to switch between an permitted state that allows conduction and a prohibited state that prohibits conduction.

[0013] The power generation system 1 further comprises a power generation system 10 configured to utilize an organic medium, such as R-245fa or R1233zd(E) (i.e., HFO-1233zd(E)), as a heat transfer medium. The power generation system 10 comprises an induction generator 15 configured to rotate integrally with the turbine 13. The induction generator 15 is provided in parallel with the main generator 2 and the emergency generator 3 via the busbar 8 of the power grid 5. The capacity of the main generator 2 is greater than the capacity of the induction generator 15 and the capacity of the emergency generator 3. During normal operation of the power generation system 1, a predetermined device 7 receives power from both the main generator 2 and the induction generator 15, but the frequency of power supply depends on the frequency of the main generator 2, and therefore the induction generator 15 does not require a converter or inverter.

[0014] <Configuration of power generation system 10> The power generation system 10 comprises a condenser 11, an evaporator 12, and a turbine 13. The condenser 11 is configured to condense an organic medium using cooling water, such as natural water (more specifically, seawater). The evaporator 12 is configured to evaporate the organic medium using heat, for example, hot water. The turbine 13 is configured to rotate using a gaseous organic medium as the working fluid.

[0015] The power generation system 10 further includes a circulation line 20 for the organic medium to flow sequentially through the condenser 11, evaporator 12, and turbine 13. The circulation line 20 includes a condenser-evaporator line 23 connected to the condenser 11 and evaporator 12, an evaporator-turbine line 21 connected to the evaporator 12 and turbine 13, and a turbine-condenser line 22 connected to the turbine 13 and condenser 11. The condenser-evaporator line 23 is provided with a pump device 16 for sending the organic medium discharged from the condenser 11 to the evaporator 12.

[0016] The power generation system 10 further includes a bypass line 25 for guiding the organic medium discharged from the evaporator 12 to the condenser 11, bypassing the turbine 13. The inlet 25A of the bypass line 25 is connected to the evaporator-turbine line 21 between the evaporator 12 and the turbine 13, and the outlet 25B of the bypass line 25 is connected to the turbine-condenser line 22 between the turbine 13 and the condenser 11.

[0017] The power generation system 10 includes a flow control valve 30 for adjusting the ratio between the bypass flow rate, which is the flow rate of the organic medium flowing through the bypass line 25, and the main flow rate, which is the flow rate of the organic medium flowing into the turbine 13. The flow control valve 30 illustrated in Figure 1 includes a first flow control valve 31 provided in the evaporator turbine line 21 and a bypass flow control valve 35 provided in the bypass line 25. The first flow control valve 31 is located between the inlet 25A of the bypass line 25 and the turbine 13. By controlling the opening degree of the first flow control valve 31 and the bypass flow control valve 35, the main flow rate is adjusted, and the rotational speed of the turbine 13 is controlled. In this example, the power generation system 10 further includes an on-off valve 29 provided in the evaporator turbine line 21 between the inlet 25A and the first flow control valve 31.

[0018] The power generation system 10 further includes a switching device 14 for switching the conduction state between the induction generator 15 and the busbar 8 of the power system 5. The switching device 14 is, for example, a circuit breaker configured to switch between an permitted state that allows conduction and a prohibited state that prohibits conduction.

[0019] The rotational speed of the induction generator 15 changes by adjusting the main flow rate through the opening control of the flow control valve 30. When the rotational speed of the induction generator 15 falls below the synchronous rotational speed and the switching device 14 switches from the prohibited state to the permitted state, the induction generator 15 is driven as an electric motor by receiving power from the power system 5. That is, the induction generator 15 motorizes. As a result, the rotational speed of the induction generator 15 increases to the synchronous rotational speed. Here, the synchronous rotational speed is the rotational speed of the induction generator 15 that corresponds to the frequency of the power system 5. The synchronous rotational speed may also be the rated rotational speed of the induction generator 15.

[0020] On the other hand, when the switching device 14 maintains the permitted state and the rotational speed of the induction generator 15 exceeds the synchronous rotational speed, the electromotive force generated in the stator coil of the induction generator 15 by the rotation of the rotor of the induction generator 15 exceeds the potential of the bus bar 8 that has been supplying power to the induction generator 15, and the direction of power flow between the induction generator 15 and the power system 5 is switched. At this time, the induction generator 15 supplies power to the power system 5 as a generator. The power is supplied to a predetermined device 7.

[0021] FIG. 2 is a graph showing the change over time in the rotational speed of the induction generator 15 in the startup operation of the power generation system 10. The horizontal axis of the graph indicates time, and the vertical axis indicates the rotational speed of the induction generator 15. The outline of the startup operation of the power generation system 10 in this example is as follows. At the start of startup, the switching device 14 is in the prohibited state. First, as the organic medium flows into the turbine 13, the induction generator 15 starts to rotate (0 ≦ t < t1). Triggered by the rotational speed of the induction generator 15 reaching a target rotational speed lower than the synchronous rotational speed (t = t1), the switching device 14 switches to the permitted state. In this case, the induction generator 15 starts motoring by the power supply from the power system 5. When the rotational speed of the induction generator 15 further increases and exceeds the synchronous rotational speed (t > t2) by controlling the opening degree of the flow control valve 30, the induction generator 15 supplies power to the power system 5 as a generator. Thus, by increasing the rotational speed of the turbine 13 with the organic medium before the start of motoring, it is possible to suppress the voltage drop of the power system 5 and reduce the inrush current of the induction generator 15 at the start of motoring.

[0022] Note that, as an example, the target rotational speed is a rotational speed of 95% or more and less than 100% with respect to the synchronous rotational speed. In this case, together with suppressing the voltage drop of the power system 5 and reducing the inrush current of the induction generator 15 described above, it is also possible to reduce the starting torque of the turbine 13.

[0023] <Heat source system of the evaporator 12> Returning to Figure 1, the power generation system 10 includes a hot water supply line 121 for supplying hot water to the evaporator 12 as a heat source for evaporating the organic medium, a hot water discharge line 122 for the hot water discharged from the evaporator 12 to flow through, a hot water bypass line 125 connected to the hot water supply line 121 and the hot water discharge line 122 so as to bypass the evaporator 12, and a hot water flow control valve 127. The hot water flow control valve 127 is configured to change the ratio between the main hot water flow rate, which is the flow rate of hot water flowing into the evaporator 12, and the hot water bypass flow rate, which is the flow rate of hot water flowing through the hot water bypass line 125. In this example, the hot water flow control valve 127 is a three-way valve provided at the connection point between the hot water bypass line 125 and the hot water supply line 121. In other examples, the hot water flow control valve 127 may be a flow control valve provided on both the hot water supply line 121 and the hot water flow control valve 127.

[0024] The hot water flowing through the hot water supply line 121 is water heated by the heating device 70. In this example, the heating device 70 is a heat exchanger configured to heat water through heat exchange between the water and the exhaust gas discharged from the marine main engine 79. In other words, the hot water supply line 121 in this example is configured to supply hot water heated by the exhaust gas discharged from the marine main engine 79 to the evaporator 12. However, as mentioned above, the power generation system 10 may be installed on land, in which case the heating device 70 may be, for example, a boiler, and the marine main engine 79 is not an essential component of this disclosure. Also, the boiler may be installed on a ship, and jacket water, which is the cooling water for the engine, may be used as the heat source.

[0025] If the opening of the flow control valve 30 remains constant, the more the amount of heat contained in the hot water flowing into the evaporator 12 increases, the greater the main flow rate of the organic medium flowing from the evaporator 12 to the turbine 13, and the greater the output power of the induction generator 15 (i.e., the load on the induction generator 15). The controller 90, a component of the power generation system 10, is configured to control the opening of the hot water flow control valve 127 when it determines that the power measured by the power meter 91 exceeds a specified power, thereby increasing the hot water bypass flow rate and decreasing the main hot water flow rate (details will be described later).

[0026] <Controller 90> The mechanical configuration of the controller 90 is as follows. The controller 90 is composed of a computer and includes a processor, memory (storage medium), and an external communication interface. The processor is a CPU, GPU, MPU, DSP, or a combination thereof. In other embodiments, the processor may be implemented by an integrated circuit such as a PLD, ASIC, FPGA, or MCU. The memory is configured to store various data temporarily or permanently and is implemented by, for example, at least one of RAM, ROM, or flash memory. The processor executes various control processes according to the instructions of the program loaded into the memory. These control processes include the process by which the processor sends control signals to the switching devices 9A~9C,14, the flow control valve 30, the hot water flow control valve 127, and the on / off valve 29, and the process by which the processor acquires measurement results from the power meter 91 and the rotation speed meter 98.

[0027] Figure 3 is a schematic diagram showing the functional configuration of a controller 90 according to one embodiment of the present disclosure. The controller 90 includes a turbine start control unit 81, a generator motoring control unit 82, and a turbine speed increase control unit 83.

[0028] The turbine startup control unit 81 is configured to increase the main flow rate of the organic medium flowing into the turbine 13 by controlling the opening degree of the flow control valve 30 when the power generation system 10 starts up. More specifically, the turbine startup control unit 81 is configured to send a control signal to increase the opening degree of the first flow control valve 31 and a control signal to decrease the opening degree of the bypass flow control valve 35. When these control signals are sent, the induction generator 15 starts up together with the turbine 13, and the rotational speed of the induction generator 15 increases. In addition, the turbine startup control unit 81 in this example also performs the process of sending an open signal to the on-off valve 29. When the on-off valve 29 receives the open signal, it switches from the closed state to the open state.

[0029] The generator motoring control unit 82 is configured to switch the switching device 14 from a prohibited state to an permitted state when the rotational speed of the induction generator 15, which is increased by the opening control of the turbine starting control unit 81, reaches the target rotational speed. More specifically, the generator motoring control unit 82 is configured to determine whether the measurement result of the rotational speed meter 98 has reached the target rotational speed. When the generator motoring control unit 82 determines that the measurement result has reached the target rotational speed, a control signal is transmitted from the generator motoring control unit 82 to the switching device 14 to switch from a prohibited state to an permitted state. When this control signal is transmitted, since the rotational speed of the induction generator 15 is below the synchronous rotational speed, the induction generator 15 performs motoring using power supplied from the power system 5 (more specifically, power supplied from the main generator 2). After that, the rotational speed of the induction generator 15 increases to the synchronous rotational speed.

[0030] The turbine speed-increasing control unit 83 is configured to further increase the main flow rate of the organic medium flowing into the turbine 13 by adjusting the opening of the flow control valve 30 so that the rotational speed of the induction generator 15 exceeds the synchronous rotational speed, after the switching device 14 switches from the prohibited state to the permitted state. More specifically, the turbine speed-increasing control unit 83 is configured to send a control signal to the first flow control valve 31 to further increase its opening and a control signal to the bypass flow control valve 35 to further decrease its opening. In a more detailed example, the first flow control valve 31 is set to fully open. As a result of the further increase in the main flow rate of the organic medium flowing into the turbine 13, the rotational speed of the induction generator 15 exceeds the synchronous rotational speed. The induction generator 15 switches from motor mode to generator mode, and power is supplied from the induction generator 15 to the power system 5.

[0031] According to the above configuration, the timing at which power for motoring is supplied from the power system 5 to the induction generator 15 is after the rotational speed of the induction generator 15 has reached the target rotational speed. This reduces the inrush current of the induction generator 15 at the start of motoring, allowing the induction generator 15 to start stably. In addition, the effects of reducing the voltage drop in the power system 5 and reducing the starting torque of the turbine 13 are also obtained. Furthermore, the increase in the amount of organic refrigerant flowing through the turbine speed-increasing control unit 83 causes the rotational speed of the induction generator 15 to exceed the synchronous rotational speed, and the induction generator 15 switches from an electric motor to a generator. At this time, since the organic medium flows continuously into the turbine 13, fluctuations in the generator's rotational speed around the synchronous rotational speed are suppressed. Moreover, at the start of power generation by the induction generator 15, the induction generator 15 can supply power to a predetermined device 7 together with the main generator 2. At this time, the induction generator 15 does not supply power to the predetermined device 7 on its own, so an inverter and converter for the induction generator 15 can be eliminated, making the power generation system 10 inexpensive. Based on the above, a power generation system 10 is realized that can stably start the induction generator 15 while also achieving low costs.

[0032] The inrush current of the induction generator 15 is the peak current flowing through the stator coil of the induction generator 15 at the moment motoring begins. After a certain amount of time has passed since motoring began, the current flowing through the stator coil becomes smaller than the peak current.

[0033] The description of the controller 90 configuration continues. Although not essential components of this disclosure, the controller 90 may further include a trip determination unit 84, a shutoff control unit 85, and a turbine deceleration control unit 86.

[0034] The trip determination unit 84 is configured to determine whether to trip the power generation system 10. More specifically, the trip determination unit 84 is configured to determine whether the trip conditions for the power generation system 10 have been met. As an example, if at least one of the following events (A) to (C) occurs, it is determined that the trip conditions have been met. (A) The power generation system 10 was subjected to vibrations exceeding a specified level. (B) A trip command is input to the controller 90. (C) The switching device 14 has switched from the permitted state to the prohibited state.

[0035] The trip control unit 85 is configured to switch the switching device 14 from the permitted state to the prohibited state when the trip determination unit 84 determines that the power generation system 10 has been tripped. More specifically, when the trip condition is met, a control signal is sent from the trip control unit 85 to the switching device 14 to switch from the permitted state to the prohibited state. When the switching device 14 switches to the prohibited state, the power supply from the induction generator 15 stops.

[0036] In this example, the cutoff control unit 85 does not perform control processing when event (C) occurs (because the switching device 14 has already been switched to the disabled state). In other words, the cutoff control unit 85 in this example switches the switching device 14 to the disabled state only when at least one of events (A) to (C) occurs.

[0037] Furthermore, when the switching device 14 switches from the permitted state to the prohibited state, the main generator 2 supplies power to the designated equipment 7 while supplementing the power that was supplied by the induction generator 15. This power supply by the main generator 2 is performed without the controller 90 performing any special control processing.

[0038] The turbine reduction control unit 86 is configured to reduce the turbine 13 by controlling the opening of the flow control valve 30 when the trip condition of the power generation system 10 is met. More specifically, the turbine reduction control unit 86 is configured to send a control signal to the bypass flow control valve 35 to increase its opening and a control signal to the first flow control valve 31 to decrease its opening. When these control signals are sent, the bypass flow rate of the organic medium increases and the main flow rate of the organic medium decreases, so the turbine 13 is reduced.

[0039] In this example, a control signal to set the opening to 0% is sent from the turbine reduction control unit 86 to the first flow control valve 31. In other words, the turbine 13 is stopped by the control processing of the turbine reduction control unit 86. Furthermore, the turbine reduction control unit 86 in this example is configured to send a closing signal to the on-off valve 29 when the trip condition is met. With this configuration, the on-off valve 29 is closed when the trip condition is met, and the inflow of organic medium into the turbine 13 is reliably prevented. Also, in this example, the on-off valve 29 and the first flow control valve 31 are provided between the inlet 25A of the bypass line 25 and the turbine 13 (see Figure 1), so the turbine 13 can quickly perform the stopping operation in response to the control processing of the turbine reduction control unit 86.

[0040] Furthermore, in this example, the hot water flow control valve 127 is opened when the trip condition for the power generation system 10 is met. The hot water bypass flow rate increases, and the amount of heat input to the evaporator 12 is reduced.

[0041] According to the above configuration, the turbine reduction control unit 86 controls the opening degree of the flow control valve 30 when the trip condition is met. This allows the process of reducing the turbine 13 to be executed immediately in the event of a trip in the power generation system 10. Furthermore, even if the power generation system 10 stops generating power due to a trip in the power generation system 10, the main generator 2 continues to supply power while supplementing the power that the induction generator 15 was supplying, so that the specified equipment 7 can continue to operate.

[0042] The description of the controller 90 configuration will continue. Although not essential components of this disclosure, the controller 90 may further include an overload determination unit 87 and a generator load reduction control unit 88.

[0043] The overload determination unit 87 is configured to determine whether the output power of the induction generator 15 exceeds a specified power based on the measurement results of the power measuring instrument 91. The specified power is a threshold value for determining whether the output power (i.e., load) of the induction generator 15 is excessive. The generator load reduction control unit 88 is configured to control the opening degree of the hot water flow control valve 127 when it determines that the output power of the induction generator 15 exceeds the specified power, thereby reducing the main hot water flow rate into the evaporator 12 and increasing the hot water bypass flow rate. In this example, the main hot water flow rate and the hot water bypass flow rate are controlled through the opening degree control of the hot water flow control valve 127, which is a three-way valve.

[0044] If the amount of heat contained in the hot water flowing into the evaporator 12 increases due to an increase in the output of the marine main engine 79, the amount of heat input from the hot water to the evaporator 12 will increase. As a result, the main flow rate of the organic medium flowing into the turbine 13 will increase, and there is a risk that the output power of the induction generator 15 will become excessive. In this regard, with the above configuration, if it is determined that the output power of the induction generator 15 exceeds the specified power, the main hot water flow rate is reduced, thereby preventing the load on the induction generator 15 from becoming excessive.

[0045] Furthermore, if the power generation system 10 is an ORC system instead of the waste heat ORC system shown in Figure 1, a seawater supply line is provided instead of the hot water supply line 121, a seawater bypass line is provided instead of the hot water bypass line 125, a seawater control valve is provided instead of the hot water flow control valve 127, and liquid LNG is supplied to the condenser 11 instead of cooling water. The temperature of the seawater flowing through the seawater supply line is kept almost constant. The vaporized LNG discharged from the condenser 11 is supplied to the customer. Since the amount of LNG required by the customer changes, the amount of organic medium condensed in the condenser 11 also changes. Therefore, when an ORC system is applied, the process by which the seawater control valve is controlled when an overload occurs is different from the process by which the hot water flow control valve 127 is controlled in the waste heat ORC system.

[0046] Specifically, if the demand for LNG at the customer's site decreases, the amount of liquid LNG supplied to the condenser 11 will also decrease. In this case, the amount of heat contained in the circulation line 20 will increase, and if this amount of heat exceeds a predetermined value, an overload will occur in the induction generator 15. At this time, the seawater control valve is activated to release seawater into the seawater bypass line, reducing the amount of heat input to the evaporator 12 (the amount of heat input to the circulation line 20).

[0047] <How to start power generation system 10> The method for starting the power generation system 10 will be described with reference to Figures 3 and 4. Figure 4 is a flowchart of the operation method of the power generation system 10 according to one embodiment of the present disclosure. The operation method includes the method for starting the power generation system 10. At least a part of the operation method is realized by the control processing of the processor constituting the controller 90. In the following description, "step" may be abbreviated as "S" and the processor of the controller 90 may be abbreviated as "processor". Before the start of the operation method of the power generation system 10, the turbine 13 is stopped and the switching device 14 is in a disabled state.

[0048] First, a turbine startup step (S11) is performed, which increases the main flow rate of the organic medium flowing into the turbine 13 by adjusting the opening of the flow control valve 30. S11 is performed by a processor, and the processor that performs S11 is an example of a turbine startup control unit 81. As a result of performing S11, the rotational speed of the turbine 13 gradually increases.

[0049] Next, the generator motoring step (S13) is executed. In S13, when the rotational speed of the induction generator 15 reaches the target rotational speed, the switching device 14 switches from the prohibited state to the permitted state, and power supply from the power system 5 to the induction generator 15 begins. At this timing, the induction generator 15 starts as an electric motor. S13 is executed by the processor, and the processor that executes S13 is an example of the generator motoring control unit 82.

[0050] Next, a turbine speed-increasing step (S15) is performed, which adjusts the opening of the flow control valve 30 to further increase the main flow rate flowing into the turbine 13. S15 is performed by a processor, and the processor that performs S15 is an example of the turbine speed-increasing control unit 83. The execution of S15 further increases the rotational speed of the induction generator 15. The first flow control valve 31 is fully opened when the output of the induction generator 15 reaches its maximum relative to the amount of heat input from the hot water supply line 121 to the evaporator 12. The first flow control valve 31 is fully opened when t≧t2 in Figure 2.

[0051] After the execution of S15, the power generation start step (S17) is executed. In S17, the induction generator 15, which has switched from motor to generator mode because its rotational speed exceeds the synchronous rotational speed, starts supplying power to the power system 5. S17 is a step that is realized after the execution of S15, and the processor does not require any special control processing in S17. After the execution of S17, the flowchart in Figure 4 ends.

[0052] <Operation method of power generation system 10 when a trip occurs> Figure 5 is a flowchart showing the operation method of the power generation system 10 in the event of a trip.

[0053] If it is determined that the trip condition has been met, the switching device 14 is switched from the permitted state to the prohibited state (S21). S21 is executed by the processor, and the processor that executes S21 is an example of the trip control unit 85.

[0054] Next, a turbine deceleration step (S23) is performed in which the opening degree of the flow control valve 30 is controlled to increase the bypass flow rate of the organic medium and reduce the main flow rate of the organic medium flowing into the turbine 13. In S23 of this example, the turbine 13 stops and the induction generator 15 also stops. S23 is executed by a processor, and the processor that executes S23 is an example of a turbine deceleration control unit 86.

[0055] Next, the opening degree of the hot water flow control valve 127 is controlled (S24), increasing the hot water bypass flow rate and reducing the amount of heat input to the evaporator 12.

[0056] Next, a power supply continuation step (S25) is performed in which the main generator 2 continues to supply power to the designated equipment 7 while supplementing the power that was supplied to the designated equipment 7 by the induction generator 15. S25 is performed automatically as a result of the execution of S21. S25 does not require any special control processing by the processor. After that, the flowchart in Figure 5 ends.

[0057] <Operation method of power generation system 10 when overload occurs> Figure 6 is a flowchart showing the operation method of the power generation system 10 when an overload occurs. First, it is determined whether the load on the induction generator 15 is excessive based on the measurement results of the power meter 91 (S27). S27 is executed by the processor, and the processor that executes S27 is an example of the overload determination unit 87. If it is determined that the load on the induction generator 15 is not excessive (S27: NO), the flowchart in Figure 6 ends. After this, the operation of the power generation system 10 continues.

[0058] If it is determined that the load on the induction generator 15 is excessive (S27: YES), the generator load reduction step (S29) is executed. In S29, the opening degree of the hot water flow control valve 127 is controlled to reduce the main hot water flow rate into the evaporator 12 and increase the hot water bypass flow rate. S29 is executed by the processor, and the processor that executes S29 is an example of the generator load reduction control unit 88. After that, the flowchart in Figure 6 ends.

[0059] As described above, the flow control valve 30 (see Figure 1) includes a first flow control valve 31 provided in the evaporator turbine line 21 between the inlet 25A of the bypass line 25 and the turbine 13, and a bypass flow control valve 35 provided in the bypass flow control valve 35. Then, in the turbine startup step (S11) and the turbine speed increase step (S15), the opening degree of the bypass flow control valve 35 is decreased and the opening degree of the first flow control valve 31 is increased. With the above configuration, since the first flow control valve 31 is positioned directly in front of the turbine 13, the main flow rate of the organic medium flowing into the turbine 13 can be controlled with high precision in each of S11 and S15.

[0060] <Summary> The contents described in some of the embodiments above can be understood, for example, as follows:

[0061] 1) A power generation system (10) according to one embodiment of the present disclosure is A method for starting a power generation system comprising a condenser (11), an evaporator (12), and a turbine (13), The aforementioned power generation system A circulation line (20) for the organic medium, which serves as a heat transfer medium, to flow sequentially through the condenser, the evaporator, and the turbine, A bypass line (25) for guiding the organic medium discharged from the evaporator to the condenser, bypassing the turbine, A flow control valve (30) for adjusting the ratio between the bypass flow rate of the organic medium flowing through the bypass line and the main flow rate, which is the flow rate of the organic medium flowing into the turbine, An induction generator (15) connected to the turbine, A switching device (14) is configured to switch between an permitted state that allows conduction between the induction generator and the power system (5) and a prohibited state that prohibits the conduction, Equipped with, The induction generator is installed in parallel with a main generator (2) which has a larger capacity than the induction generator and constitutes the power system. The method for starting the power generation system is as follows: A turbine startup step (S11) is performed by adjusting the opening degree of the flow control valve to increase the main flow rate, When the rotational speed of the induction generator, which increases as a result of the execution of the turbine starting step, reaches the target rotational speed, the switching device is switched from the prohibited state to the permitted state, and power supply from the power system to the induction generator is started in a generator motoring step (S13), After the execution of the generator motoring step, a turbine speed-increasing step (S15) is performed in which the opening degree of the flow control valve is adjusted to further increase the main flow rate, When the rotational speed of the induction generator exceeds a synchronous rotational speed greater than the target rotational speed, the induction generator, which has switched from motor mode to generator mode, begins supplying power to the power system in a power generation start step (S17). It is equipped with.

[0062] According to the configuration described in 1) above, the timing at which power for motoring is supplied from the power grid to the induction generator is after the induction generator's rotational speed reaches the target rotational speed. This reduces the inrush current of the induction generator at the start of motoring, allowing the induction generator to start stably. In addition, the effects of reducing the voltage drop in the power grid and reducing the turbine starting torque are also obtained. Furthermore, the increase in the amount of organic refrigerant flow in the turbine speed-increasing step causes the induction generator's rotational speed to exceed the synchronous rotational speed, and the induction generator switches from an electric motor to a generator. In the power generation start step, the induction generator can supply power to predetermined equipment together with the main generator. At this time, since the induction generator does not supply power to predetermined equipment on its own, an inverter and converter for the induction generator can be eliminated, making the power generation system inexpensive. Thus, a power generation system startup method is realized that allows for stable startup of the induction generator while achieving low costs.

[0063] 2) In some embodiments, the method for starting the power generation system described in 1) above, If a specified trip condition is met after the execution of the power generation start step, the system further includes a turbine reduction step (S23) in which the opening degree of the flow control valve is controlled to increase the bypass flow rate and decrease the main flow rate.

[0064] According to the configuration described in 2) above, the step of decelerating the turbine can be immediately executed in response to a trip in the power generation system.

[0065] 3) In some embodiments, a method for starting the power generation system described in 1) or 2) above, In the power generation start step, the induction generator, together with the main generator, supplies power to a predetermined device (7) connected to the power system. The method for starting the power generation system is as follows: When the specified trip conditions are met and the switching device switches to the prohibited state, the main generator includes a power supply continuation step (S25) in which it continues to supply power to the specified equipment while supplementing the power that was supplied by the induction generator.

[0066] According to the configuration described in 3) above, even if the power generation system stops generating power due to a trip in the power generation system, the specified equipment can continue to operate by power supply from the main generator.

[0067] 4) In some embodiments, a method for starting the power generation system described in 1) or 3) above, The aforementioned power generation system A hot water supply line (121) for supplying hot water heated by exhaust gas discharged from a marine main engine (79) to the evaporator as a heat source for evaporating the organic medium, A hot water discharge line (122) through which the hot water discharged from the evaporator flows, A hot water bypass line (25) is connected to the hot water supply line and the hot water discharge line so as to bypass the evaporator, A hot water flow control valve (127) for changing the ratio between the main hot water flow rate, which is the flow rate of the hot water flowing into the evaporator, and the hot water bypass flow rate, which is the flow rate of the hot water flowing through the hot water bypass line, Equipped with, The method for starting the power generation system is as follows: The system further includes a generator load reduction step (S29) in which, if it is determined that the output power of the induction generator exceeds a specified power, the opening degree of the hot water flow control valve is controlled to reduce the main hot water flow rate and increase the hot water bypass flow rate.

[0068] When the output of a marine main engine increases, the amount of heat contained in the hot water flowing into the evaporator increases. As a result, the amount of heat input from the hot water to the evaporator increases, which can lead to an increase in the main flow rate of the organic medium into the turbine, potentially causing the induction generator's output power to become excessive. In this regard, according to the configuration of 4) above, if it is determined that the induction generator's output power exceeds the specified power, the main hot water flow rate is reduced, thereby preventing the induction generator from becoming overloaded.

[0069] 5) In some embodiments, a method for starting a power generation system as described in any of 1) to 4) above, The circulation line is an evaporator-turbine line connected to the evaporator and the turbine, and includes an evaporator-turbine line (21) to which the inlet (25A) of the bypass line is connected between the evaporator and the turbine. The aforementioned flow control valve is A first flow control valve (31) is provided in the evaporator turbine line between the inlet of the bypass line and the turbine, A bypass flow control valve (35) provided in the bypass line and Includes, In each of the turbine startup step and the turbine speed-increasing step, the opening of the bypass flow control valve is reduced and the opening of the first flow control valve is increased.

[0070] According to the configuration in 5) above, since the first flow control valve is positioned directly in front of the turbine, the flow rate can be precisely controlled in both the turbine startup step and the turbine speed-increasing step.

[0071] 6) A power generation system (10) according to at least one embodiment of the present disclosure is A power generation system comprising a condenser (11), an evaporator (12), and a turbine (13), A circulation line (20) for the organic medium, which serves as a heat transfer medium, to flow sequentially through the condenser, the evaporator, and the turbine, A bypass line (25) for guiding the organic medium discharged from the evaporator to the condenser, bypassing the turbine, A flow control valve (30) for adjusting the ratio between the bypass flow rate of the organic medium flowing through the bypass line and the main flow rate, which is the flow rate of the organic medium flowing into the turbine, An induction generator (15) connected to the turbine, A switching device (14) is configured to switch between an permitted state that allows conduction between the induction generator and the power system (5) and a prohibited state that prohibits the conduction, Controller (90) and Equipped with, The induction generator is installed in parallel with a main generator (2) which has a larger capacity than the induction generator and constitutes the power system. The aforementioned controller, A turbine startup control unit (81) for increasing the main flow rate by controlling the opening degree of the flow control valve, When the rotational speed of the induction generator, which is increased by the opening control of the turbine starting control unit, reaches the target rotational speed, the generator motoring control unit (82) switches the switching device from the prohibited state to the permitted state, The system includes a turbine speed-increasing control unit (83) for adjusting the opening of the flow control valve to further increase the main flow rate so that the rotational speed of the induction generator exceeds a synchronous rotational speed greater than the target rotational speed, after the switching device has switched to the permitted state.

[0072] According to the configuration in 6) above, the same effects and benefits as in 1) above can be obtained. [Explanation of symbols]

[0073] 1: Power generation system 2: Main generator 3: Emergency generator 5: Power system 7:Equipment 8 :Bus bar 9A~9C: Switching device 10: Power generation system 11: Condenser 12: Evaporator 13: Turbine 14: Switching device 15: Induction Generator 16: Pumping equipment 20: Circulation Line 21: Evaporator Turbine Line 22: Turbine condenser line 23: Condenser-evaporator line 25: Bypass Line 25A: Entrance 25B:Exit 29: Shut-off valve 30: Flow control valve 31: First-flow control valve 35: Bypass flow control valve 70: Heating equipment 79: Marine main engine 81: Turbine Startup Control Unit 82: Generator Motoring Control Unit 83: Turbine Speed ​​Increase Control Unit 84: Trip detection unit 85: Interruption control unit 86: Turbine Deceleration Control Unit 87: Overload judgment section 88: Generator load reduction control unit 90: Controller 91: Power Measuring Instruments 98: Rotation speed measuring instrument 121: Hot water supply line 122: Hot water discharge line 125: Hot water bypass line 127:Hot water flow control valve

Claims

1. A method for starting a power generation system comprising a condenser, an evaporator, and a turbine, The aforementioned power generation system A circulation line for the organic medium, which serves as a heat transfer medium, to flow sequentially through the condenser, the evaporator, and the turbine, A bypass line for guiding the organic medium discharged from the evaporator to the condenser, bypassing the turbine, A flow control valve for adjusting the ratio between the bypass flow rate of the organic medium flowing through the bypass line and the main flow rate, which is the flow rate of the organic medium flowing into the turbine, An induction generator connected to the turbine, A switching device configured to switch between an permitted state that allows conduction between the induction generator and the power system and a prohibited state that prohibits the conduction, Equipped with, The induction generator is installed in parallel with a main generator having a larger capacity than the induction generator, which constitutes the power system. The method for starting the power generation system is as follows: A turbine startup step that increases the main flow rate by adjusting the opening degree of the flow control valve, When the rotational speed of the induction generator, which increases as a result of the execution of the turbine starting step, reaches the target rotational speed, the switching device is switched from the prohibited state to the permitted state, and power supply from the power system to the induction generator is started in a generator motoring step. After the execution of the generator motoring step, a turbine speed-increasing step is performed in which the opening degree of the flow control valve is adjusted to further increase the main flow rate, A power generation start step in which, when the rotational speed of the induction generator exceeds a synchronous rotational speed greater than the target rotational speed, the induction generator, which has switched from motor mode to generator mode, starts supplying power to the power system; Equipped with How to start up the power generation system.

2. If a specified trip condition is met after the execution of the power generation start step, the system further includes a turbine reduction step that controls the opening of the flow control valve to increase the bypass flow rate and decrease the main flow rate. A method for starting up a power generation system according to claim 1.

3. In the power generation start step, the induction generator, together with the main generator, supplies power to predetermined equipment connected to the power system. The method for starting the power generation system is as follows: When the specified trip conditions are met and the switching device switches to the prohibited state, the system includes a power supply continuation step in which the main generator continues to supply power to the specified equipment while supplementing the power that was supplied by the induction generator. A method for starting a power generation system according to claim 1 or 2.

4. The aforementioned power generation system A hot water supply line for supplying hot water heated by exhaust gas discharged from a marine main engine to the evaporator as a heat source for evaporating the organic medium, A hot water discharge line through which the hot water discharged from the evaporator flows, A hot water bypass line is connected to the hot water supply line and the hot water discharge line so as to bypass the evaporator, A hot water flow control valve for changing the ratio between the main hot water flow rate, which is the flow rate of the hot water flowing into the evaporator, and the hot water bypass flow rate, which is the flow rate of the hot water flowing through the hot water bypass line. Equipped with, The method for starting the power generation system is as follows: The system further includes a generator load reduction step in which, if it is determined that the output power of the induction generator exceeds a specified power, the opening degree of the hot water flow control valve is controlled to reduce the main hot water flow rate and increase the hot water bypass flow rate. A method for starting a power generation system according to claim 1 or 2.

5. The circulation line is an evaporator-turbine line connected to the evaporator and the turbine, and includes an evaporator-turbine line to which the inlet of the bypass line is connected between the evaporator and the turbine. The aforementioned flow control valve is A first flow control valve is provided in the evaporator turbine line between the inlet of the bypass line and the turbine, A bypass flow control valve provided in the bypass line and Includes, In each of the turbine startup step and the turbine speed-increasing step, the opening of the bypass flow control valve is reduced, and the opening of the first flow control valve is increased. A method for starting a power generation system according to claim 1 or 2.

6. A power generation system comprising a condenser, an evaporator, and a turbine, A circulation line for the organic medium, which serves as a heat transfer medium, to flow sequentially through the condenser, the evaporator, and the turbine, A bypass line for guiding the organic medium discharged from the evaporator to the condenser, bypassing the turbine, A flow control valve for adjusting the ratio between the bypass flow rate of the organic medium flowing through the bypass line and the main flow rate, which is the flow rate of the organic medium flowing into the turbine, An induction generator connected to the turbine, A switching device configured to switch between an permitted state that allows conduction between the induction generator and the power system and a prohibited state that prohibits the conduction, Controller and Equipped with, The induction generator is installed in parallel with a main generator having a larger capacity than the induction generator, which constitutes the power system. The aforementioned controller, A turbine startup control unit for increasing the main flow rate by controlling the opening degree of the flow control valve, When the rotational speed of the induction generator, which is increased by the opening control of the turbine starting control unit, reaches the target rotational speed, the generator motoring control unit switches the switching device from the prohibited state to the permitted state, After the switching device switches to the permitted state, the turbine speed increasing control unit adjusts the opening of the flow control valve to further increase the main flow rate so that the rotational speed of the induction generator exceeds a synchronous rotational speed greater than the target rotational speed. A power generation system equipped with the following features.

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