Starting method of power generation system and power generation system

Abstract

A method for starting a power generation system includes: a turbine starting step of increasing a main flow rate, which is a flow rate of an organic medium flowing into a turbine, by adjusting an opening degree of a flow rate control valve; a generator electric rotation step for switching the switching device from a prohibited state to a permitted state and starting the supply of power from the power system to the induction generator when the rotational speed of the induction generator, which has been increased by executing the turbine starting step, reaches a target rotational speed; a turbine speed increasing step of further increasing the main flow amount by adjusting the opening degree of the flow rate adjusting valve after the generator electric rotation step is executed; and 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 is switched from the motor to the generator, starts supplying power to the power system.

Description

Technical Field

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

[0002] This application claims priority based on Japanese Patent Application No. 2023-054454 filed with the Japan Patent Office on March 30, 2023, and incorporates its content herein. Background Art

[0003] In the power generation system disclosed in Patent Document 1, an organic fluid evaporated by an evaporator drives a power turbine, and power is generated by a generator. The generated power is adjusted in frequency by an inverter device and then guided to an in-ship system.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2011-231636 Summary of the Invention

[0007] Technical Problem to be Solved by the Invention

[0008] In the above power generation system, since an inverter device is installed in the generator, there is a possibility of cost increase. Also, when the generator performs electric rotation as the power generation system starts, it is preferable for the generator to stably switch from the electric rotation mode to the power generation mode. However, a specific structure is not disclosed in the above patent document.

[0009] An object of the present invention is to provide a method for starting a power generation system and a power generation system that can stably start an induction generator and achieve cost reduction.

[0010] Means for Solving the Technical Problem

[0011] A method for starting a power generation system according to at least one embodiment of the present invention is a method for starting a power generation system including a condenser, an evaporator, and a turbine, the power generation system including:

[0012] A circulation pipeline for causing an organic medium as a heat medium to flow sequentially through the condenser, the evaporator, and the turbine;

[0013] A bypass pipeline for causing the organic medium discharged from the evaporator to bypass the turbine and guiding it to the condenser;

[0014] A flow rate regulating valve for adjusting the ratio of the bypass flow rate of the organic medium flowing through the bypass pipeline to the main flow rate of the organic medium flowing into the turbine;

[0015] An induction generator, connected to the turbine; and

[0016] A switching device configured to switch between a permitted state that permits conduction between the induction generator and the power system and a prohibited state that prohibits the conduction

[0017] The induction generator and a main generator that constitutes the power system and has a larger capacity than the induction generator are arranged side by side

[0018] The startup method of the power generation system includes:

[0019] A turbine startup step of increasing the main flow rate by adjusting the opening degree of the flow rate regulating valve

[0020] A generator motor rotation step of, when the rotational speed of the induction generator increased by performing the turbine startup step reaches a target rotational speed, switching the switching device from the prohibited state to the permitted state and starting power supply from the power system to the induction generator

[0021] A turbine speed increasing step of, after performing the generator motor rotation step, adjusting the opening degree of the flow rate regulating valve to further increase the main flow rate; and

[0022] A power generation start step of, when the rotational speed of the induction generator exceeds a synchronous rotational speed greater than the target rotational speed, the induction generator switching from a motor to a generator and starting to supply power to the power system

[0023] The power generation system according to an embodiment of the present invention includes a condenser, an evaporator, and a turbine, and the power generation system includes:

[0024] A circulation pipeline for allowing an organic medium as a heat medium to flow through the condenser, the evaporator, and the turbine in sequence

[0025] A bypass pipeline for allowing the organic medium discharged from the evaporator to bypass the turbine and guiding it to the condenser

[0026] A flow rate regulating valve for adjusting the ratio of the bypass flow rate of the organic medium flowing through the bypass pipeline to the main flow rate of the organic medium flowing into the turbine

[0027] An induction generator, connected to the turbine

[0028] A switching device configured to switch between a permitted state that permits conduction between the induction generator and the power system and a prohibited state that prohibits the conduction, and

[0029] A controller

[0030] The induction generator is arranged side by side with the main generator that constitutes the power system and has a larger capacity than the induction generator.

[0031] The controller includes:

[0032] A turbine start control unit for increasing the main flow rate by controlling the opening degree of the flow rate regulating valve;

[0033] A generator electric rotation control unit for switching the switching device from the prohibited state to the permitted state when the rotational speed of the induction generator increased by the opening degree control of the turbine start control unit reaches the target rotational speed; and

[0034] A turbine speed increase control unit for further increasing the main flow rate by adjusting the opening degree of the flow rate regulating valve so that the rotational speed of the induction generator exceeds the synchronous rotational speed greater than the target rotational speed after the switching device is switched to the permitted state.

[0035] Advantageous Effects of the Invention

[0036] According to the present invention, it is possible to provide a starting method for a power generation system and a power generation system that can stably start an induction generator and achieve cost reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic diagram of a power generation system according to an embodiment.

[0038] Figure 2 is a graph schematically showing the change over time of the rotational speed of an induction generator performing a starting operation according to an embodiment.

[0039] Figure 3 is a schematic diagram showing the functional structure of a controller according to an embodiment.

[0040] Figure 4 is a flowchart showing a starting method for a power generation system according to an embodiment.

[0041] Figure 5 is a flowchart showing an operation method of a power generation system when a trip occurs according to an embodiment.

[0042] Figure 6 is a flowchart showing an operation method of a power generation system when an overload occurs according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0043] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the constituent parts described as embodiments or shown in the drawings are not intended to limit the scope of the present invention thereto, and are merely illustrative examples.

[0044] For example, expressions indicating relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial" not only represent such arrangements in a strict sense, but also represent a state of relative displacement with an angle or distance having a tolerance or to an extent that can achieve the same function.

[0045] For example, expressions indicating that things are in the same state such as "identical", "equal", and "homogeneous" not only represent the same state in a strict sense, but also represent a state with a difference having a tolerance or to an extent that can achieve the same function.

[0046] For example, expressions indicating shapes such as a quadrilateral shape or a cylindrical shape not only represent the quadrilateral shape, cylindrical shape, etc. in a strict geometric sense, but also represent shapes including concavo-convex portions, chamfered portions, etc. within a range where the same effect can be obtained.

[0047] On the other hand, the expression "comprising", "including", or "having" a constituent element is not an exclusive expression excluding the existence of other constituent elements.

[0048] In addition, the same reference numerals are given to the same structures, and the description may sometimes be omitted.

[0049] <Overall Structure of Power Generation System 1>

[0050] Figure 1 It is a schematic diagram of a power generation system 1 according to an embodiment of the present invention. The power generation system 1 of this example includes a power system 5, a main generator 2 connected to the power system 5, an emergency generator 3 arranged side by side with the main generator 2 via the power system 5, and a specified device 7 configured to receive power supply from the power system 5. The specified device 7 can be any device as long as it is a device that operates by receiving power supply. As an example, it is one or more driving devices such as a motor. The power generation system 1 can be installed on a ship or on land, but the power generation system 1 installed on a ship will be exemplified below. In addition, the emergency generator 3 is not an essential constituent element of the present invention.

[0051] The power system 5 includes a bus bar 8 and switching devices 9A to 9C. The switching device 9A is configured to switch the conduction state between the bus bar 8 and the main generator 2. Similarly, the switching device 9B is configured to switch the conduction state between the bus bar 8 and the emergency generator 3, and the switching device 9C is configured to switch the conduction state between the bus bar 8 and the specified equipment 7. As an example, the switching devices 9A to 9C are circuit breakers configured to switch between a permitted state allowing conduction and a prohibited state prohibiting conduction.

[0052] The power generation system 1 further includes a power generation system 10 configured to use an organic medium, which may be, for example, R-245fa or R1233zd (E) (i.e., HFO-1233zd (E)), as a heat medium. The power generation system 10 includes an induction generator 15 configured to rotate integrally with the turbine 13. The induction generator 15 is arranged in parallel with the main generator 2 and the emergency generator 3 via the bus bar 8 of the power system 5. In addition, the capacity of the main generator 2 is larger than the capacities of the induction generator 15 and the emergency generator 3. When the power generation system 1 is operating normally, the specified equipment 7 receives power supplies from the main generator 2 and the induction generator 15 respectively. However, since the frequency of the power supply depends on the frequency of the main generator 2, the induction generator 15 does not require a converter and an inverter.

[0053] <Structure of the power generation system 10>

[0054] The power generation system 10 includes a condenser 11, an evaporator 12, and a turbine 13. The condenser 11 is configured to condense the organic medium using cooling water such as natural water (more specifically, seawater). The evaporator 12 evaporates the organic medium using, for example, the heat held by warm water. The turbine 13 is configured to rotate using the gaseous organic medium as a working medium.

[0055] The power generation system 10 further includes a circulation pipeline 20 for allowing the organic medium to flow through the condenser 11, the evaporator 12, and the turbine 13 in sequence. The circulation pipeline 20 includes a condenser-evaporator pipeline 23 connecting the condenser 11 and the evaporator 12, an evaporator-turbine pipeline 21 connecting the evaporator 12 and the turbine 13, and a turbine-condenser pipeline 22 connecting the turbine 13 and the condenser 11. A pump device 16 for transporting the organic medium discharged from the condenser 11 to the evaporator 12 is provided on the condenser-evaporator pipeline 23.

[0056] The power generation system 10 further includes a bypass pipeline 25 for guiding the organic medium discharged from the evaporator 12 around the turbine 13 to the condenser 11. The inlet 25A of the bypass pipeline 25 is connected to the evaporator-turbine pipeline 21 between the evaporator 12 and the turbine 13, and the outlet 25B of the bypass pipeline 25 is connected to the turbine-condenser pipeline 22 between the turbine 13 and the condenser 11.

[0057] The power generation system 10 is provided with a flow rate regulating valve 30 for adjusting the ratio of the flow rate of the organic medium flowing through the bypass pipe 25, i.e., the bypass flow rate, and the flow rate of the organic medium flowing into the turbine 13, i.e., the main flow rate. Figure 1 The flow rate regulating valve 30 illustrated in Figure 1 includes a first flow rate regulating valve 31 provided in the evaporator turbine pipe 21 and a bypass flow rate regulating valve 35 provided in the bypass pipe 25. The first flow rate regulating valve 31 is located between the inlet 25A of the bypass pipe 25 and the turbine 13. By controlling the opening degrees of the first flow rate regulating valve 31 and the bypass flow rate regulating valve 35 respectively, the main flow rate is adjusted and the rotational speed of the turbine 13 is controlled. In addition, the power generation system 10 of this example is further provided with an on-off valve 29 provided in the evaporator turbine pipe 21 between the inlet 25A and the first flow rate regulating valve 31.

[0058] The power generation system 10 is further provided with a switching device 14 for switching the conduction state between the induction generator 15 and the bus bar 8 of the power system 5. As an example, the switching device 14 is a circuit breaker configured to switch between a permitted state where conduction is permitted and a prohibited state where conduction is prohibited.

[0059] The rotational speed of the induction generator 15 changes due to the adjustment of the main flow rate controlled by the opening degree of the flow rate regulating valve 30. When the rotational speed of the induction generator 15 is lower than the synchronous speed, if the switching device 14 is switched from the prohibited state to the permitted state, the induction generator 15 receives power supply from the power system 5 and is driven as a motor. That is, the induction generator 15 performs electric rotation. As a result, the rotational speed of the induction generator 15 increases to the synchronous speed. Here, the synchronous speed is the rotational speed of the induction generator 15 corresponding to the frequency of the power system 5. The synchronous speed may also be the rated rotational speed of the induction generator 15.

[0060] On the other hand, if the switching device 14 maintains the permitted state and the rotational speed of the induction generator 15 exceeds the synchronous speed, the electromotive force generated in the stator coil of the induction generator 15 due to the rotation of the rotor of the induction generator 15 exceeds the potential of the bus bar 8 that supplies power to the induction generator 15, and the flow direction of the power 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. This power is supplied to the specified equipment 7.

[0061] Figure 2It is a graph showing the change over time of the rotational speed of the induction generator 15 during the startup operation of the power generation system 10. The horizontal axis of this graph represents time, and the vertical axis represents 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 a prohibited state. First, the induction generator 15 starts to rotate as the organic medium flows into the turbine 13 (0 ≤ t < t1). When the rotational speed of the induction generator 15 reaches a target speed lower than the synchronous speed (t = t1), the switching device 14 switches to an allowed state. In this case, the induction generator 15 starts to rotate electrically by the power supply from the power system 5. If the rotational speed of the induction generator 15 further increases and exceeds the synchronous speed due to the opening control of the flow rate regulating valve 30 (t > t2), 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 starting the electric rotation, 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 the electric rotation.

[0062] In addition, as an example, the target speed is a speed that is 95% or more and less than 100% of the synchronous speed. In this case, it is possible to suppress the voltage drop of the power system 5 and reduce the inrush current of the induction generator 15 described above, and at the same time, it is also possible to reduce the starting torque of the turbine 13.

[0063] <Heat source system of the evaporator 12>

[0064] Return to Figure 1 The power generation system 10 includes: a warm water supply pipe 121 for supplying warm water, which is an evaporation heat source of the organic medium, to the evaporator 12; a warm water discharge pipe 122 for allowing the warm water discharged from the evaporator 12 to flow; a warm water bypass pipe 125 connected to the warm water supply pipe 121 and the warm water discharge pipe 122 so as to bypass the evaporator 12; and a warm water flow rate regulating valve 127. The warm water flow rate regulating valve 127 is configured to change the ratio of the flow rate of the warm water flowing into the evaporator 12, that is, the main warm water flow rate, and the flow rate of the warm water flowing through the warm water bypass pipe 125, that is, the warm water bypass flow rate. The warm water flow rate regulating valve 127 in this example is a three-way valve provided at the connection position of the warm water bypass pipe 125 and the warm water supply pipe 121. The warm water flow rate regulating valve 127 related to other examples may also be a flow rate regulating valve provided separately for the warm water supply pipe 121 and the warm water flow rate regulating valve 127.

[0065] The warm water flowing through the warm water supply pipe 121 is water heated by the heating device 70. The heating device 70 in this example is a heat exchanger configured to heat water through heat exchange between the exhaust gas discharged from the marine main engine 79 and water. That is, the warm water supply pipe 121 in this example is configured to supply the warm water heated by the exhaust gas discharged from the marine main engine 79 to the evaporator 12. However, as described above, the power generation system 10 can also be installed on land. In this case, the heating device 70 can also be a boiler or the like, and the marine main engine 79 is not an essential component of the present invention. Moreover, the boiler can be installed on the ship, or the cooling water of the engine, that is, the jacket water, can be used as the heat source.

[0066] If the opening degree of the flow rate regulating valve 30 is constant, the more the holding heat of the warm water flowing into the evaporator 12 increases, the more the main flow rate of the organic medium flowing from the evaporator 12 into the turbine 13 increases, and the greater the output power of the induction generator 15 (that is, the load of the induction generator 15) becomes. The controller 90, which is a component of the power generation system 10, is configured to control the opening degree of the warm water flow rate regulating valve 127 to increase the warm water bypass flow rate and decrease the main warm water flow rate (the detailed content will be described later) when it is determined that the power measured by the power measuring device 91 exceeds the specified power.

[0067] <Controller 90>

[0068] The mechanical structure of the controller 90 is as follows. The controller 90 is composed of a computer and includes a processor, a memory (storage medium), and an external communication interface. The processor is a CPU, GPU, MPU, DSP, or a combination thereof, etc. The processors in other embodiments can also be implemented by integrated circuits such as PLD, ASIC, FPGA, or MCU. The memory is configured to store various data temporarily or non-temporarily, and is implemented, for example, by at least one of RAM, ROM, or flash memory. According to the instructions of the program loaded into the memory, the processor executes various control processes. These control processes include: the process in which the processor sends control signals to the switching devices 9A to 9C, 14, the flow rate regulating valve 30, the warm water flow rate regulating valve 127, and the on-off valve 29; and the process in which the processor obtains the measurement results from the power measuring device 91 and the rotational speed measuring device 98.

[0069] Figure 3 It is a schematic diagram showing the functional structure of the controller 90 according to an embodiment of the present invention. The controller 90 includes a turbine start control unit 81, a generator electric rotation control unit 82, and a turbine speed increase control unit 83.

[0070] The turbine start 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 starting the power generation system 10. More specifically, the turbine start control unit 81 is configured to send a control signal for increasing the opening degree to the first flow control valve 31 and send a control signal for decreasing the opening degree to the bypass flow control valve 35. When these control signals are sent, the induction generator 15 starts together with the turbine 13, and the rotational speed of the induction generator 15 increases. In addition, the turbine start control unit 81 of this example also executes the process of sending an opening signal to the on-off valve 29. The on-off valve 29 input with the opening signal switches from the closed state to the open state.

[0071] The generator motor rotation control unit 82 is configured to switch the switching device 14 from the prohibited state to the permitted state when the rotational speed of the induction generator 15 increased by the opening degree control of the turbine start control unit 81 reaches the target rotational speed. More specifically, the generator motor rotation control unit 82 is configured to determine whether the measurement result of the rotational speed measuring device 98 reaches the target rotational speed. And when the generator motor rotation control unit 82 determines that the measurement result reaches the target rotational speed, a control signal for switching from the prohibited state to the permitted state is sent from the generator motor rotation control unit 82 to the switching device 14. When this control signal is sent, since the rotational speed of the induction generator 15 is below the synchronous rotational speed, the induction generator 15 executes motor rotation by the power supplied from the power system 5 (more specifically, by the power supplied from the main generator 2). Then, the rotational speed of the induction generator 15 increases to the synchronous rotational speed.

[0072] The turbine speed increase control unit 83 is configured to adjust the opening degree 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 is switched from the prohibited state to the permitted state, in order to further increase the main flow rate of the organic medium flowing into the turbine 13. More specifically, the turbine speed increase control unit 83 is configured to send a control signal for further increasing the opening degree to the first flow control valve 31 and send a control signal for further decreasing the opening degree to the bypass flow control valve 35. As a more detailed example, the first flow control valve 31 is fully opened. The main flow rate of the organic medium flowing into the turbine 13 further increases, and as a result, the rotational speed of the induction generator 15 exceeds the synchronous rotational speed. The induction generator 15 switches from a motor to a generator, and power is supplied from the induction generator 15 to the power system 5.

[0073] According to the above structure, the moment when electric power for electric rotation is supplied from the power system 5 to the induction generator 15 is after the rotational speed of the induction generator 15 reaches the target rotational speed. Therefore, it is possible to reduce the inrush current of the induction generator 15 at the start of electric rotation, and the induction generator 15 can be started stably. Also, it is possible to obtain the reduction effect of the voltage drop in the power system 5 and the reduction effect of the starting torque of the turbine 13 together. Moreover, when the rotational speed of the induction generator 15 exceeds the synchronous rotational speed by increasing the main flow rate of the organic refrigerant by the turbine speed increase control unit 83, the induction generator 15 switches from a motor to a generator. At this time, the organic medium continues to flow into the turbine 13, so the increase and decrease of the rotational speed of the generator with the synchronous rotational speed as the boundary are suppressed. Further, when power generation starts by the induction generator 15, the induction generator 15 can supply power to the specified device 7 together with the main generator 2. At this time, the induction generator 15 does not supply power to the specified device 7 alone, so it is possible to eliminate the need for an inverter and a converter for the induction generator 15, and thus the cost of the power generation system 10 can be reduced. As a result, it is possible to realize a power generation system 10 that can start the induction generator 15 stably and has achieved cost reduction.

[0074] In addition, 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 of starting electric rotation. If a certain time elapses from the start of electric rotation, the current flowing through the stator coil becomes smaller than the peak current.

[0075] The structure of the controller 90 will be further described. Although not an essential component of the present invention, the controller 90 may further include a trip determination unit 84, a disconnection control unit 85, and a turbine deceleration control unit 86.

[0076] The trip determination unit 84 is configured to determine whether to trip the power generation system 10. More specifically, it is configured such that the trip determination unit 84 determines whether the trip condition of the power generation system 10 is satisfied. As an example, if at least one of the following events (A) to (C) occurs, it is determined that the trip condition is satisfied.

[0077] (A) Vibration exceeding a specified level is applied to the power generation system 10.

[0078] (B) A trip command is input to the controller 90

[0079] (C) The switching device 14 is switched from the permitted state to the prohibited state

[0080] The open - circuit control unit 85 is configured to set the switching device 14 from the permitted state to the prohibited state when it is determined by the trip determination unit 84 that the power generation system 10 should trip. More specifically, when the trip condition is satisfied, a control signal for switching from the permitted state to the prohibited state is sent from the open - circuit control unit 85 to the switching device 14. If the switching device 14 is switched to the prohibited state, the power supply based on the induction generator 15 stops.

[0081] In addition, the open - circuit control unit 85 of this example does not perform control processing when the event of the above (C) occurs (because the switching device 14 has already been switched to the prohibited state). That is, only when at least one of the events (A) or (B) among the above (A) - (C) occurs, the open - circuit control unit 85 of this example switches the switching device 14 to the prohibited state.

[0082] Moreover, when the switching device 14 is switched from the permitted state to the prohibited state, the main generator 2 supplies the power that was previously supplied by the induction generator 15 and simultaneously supplies power to the specified device 7. The controller 90 performs such power supply of the main generator 2 without performing special control processing.

[0083] The turbine speed - reduction control unit 86 is configured to reduce the speed of the turbine 13 by controlling the opening degree of the flow - rate regulating valve 30 when the trip condition of the power generation system 10 is satisfied. More specifically, the turbine speed - reduction control unit 86 is configured to send a control signal for increasing the opening degree to the bypass flow - rate regulating valve 35 and send a control signal for decreasing the opening degree to the first flow - rate regulating valve 31. 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 decelerates.

[0084] In addition, in this example, a control signal for setting the opening degree to 0% is sent from the turbine speed - reduction control unit 86 to the first flow - rate regulating valve 31. That is, the turbine 13 stops through the control processing of the turbine speed - reduction control unit 86. Moreover, the turbine speed - reduction control unit 86 of this example is configured to send a closing signal to the on - off valve 29 when the trip condition is satisfied. According to this structure, as the trip condition is satisfied, the on - off valve 29 is closed, thus reliably preventing the inflow of the organic medium into the turbine 13. And, in this example, the on - off valve 29 and the first flow - rate regulating valve 31 are provided between the inlet 25A of the bypass pipe 25 and the turbine 13 (refer to Figure 1 )), so the turbine 13 can quickly perform a stop action following the control processing of the turbine speed - reduction control unit 86.

[0085] Moreover, in this example, when the trip condition of the power generation system 10 is satisfied, the warm - water flow - rate regulating valve 127 opens. The warm - water bypass flow rate increases, and the heat input to the evaporator 12 decreases.

[0086] According to the above structure, as the trip condition is satisfied, the turbine deceleration control unit 86 controls the opening degree of the flow control valve 30. Thus, as the power generation system 10 trips, the process of decelerating the turbine 13 can be immediately executed. Moreover, even when the power generation system 10 stops generating electricity as the power generation system 10 trips, the main generator 2 continues to supply power while supplementing the power supplied by the induction generator 15, so that the specified equipment 7 can continue to operate.

[0087] The structure of the controller 90 will be further described. Although not an essential component of the present invention, the controller 90 may further include an overload determination unit 87 and a generator load reduction control unit 88.

[0088] 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 result of the power meter 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 warm water flow control valve 127 to reduce the main warm water flow rate flowing into the evaporator 12 and increase the warm water bypass flow rate when it is determined that the output power of the induction generator 15 exceeds the specified power. In this example, the main warm water flow rate and the warm water bypass flow rate are controlled by controlling the opening degree of the warm water flow control valve 127 which is a three-way valve.

[0089] When the heat held by the warm water flowing into the evaporator 12 increases due to an increase in the output of the marine main engine 79, the heat input from the warm water to the evaporator 12 increases. As a result, the main flow rate of the organic medium flowing into the turbine 13 increases, and thus the output power of the induction generator 15 may become excessive. Regarding this point, according to the above structure, when it is determined that the output power of the induction generator 15 exceeds the specified power, the main warm water flow rate decreases, so that the load of the induction generator 15 can be prevented from becoming excessive.

[0090] In addition, when the power generation system 10 is an ORC system instead of a waste heat ORC system as Figure 1 described above, a seawater supply pipeline is provided instead of the warm water supply pipeline 121, a seawater bypass pipeline is provided instead of the warm water bypass pipeline 125, a seawater control valve is provided instead of the warm 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 pipeline remains almost constant. The vaporized LNG discharged from the condenser 11 is supplied to the demand side. Since the amount of LNG required at the demand side changes, the amount used to condense the organic medium in the condenser 11 changes. Therefore, when the ORC system is applied, the process of controlling the seawater control valve during overload is different from the process of controlling the warm water flow control valve 127 in the waste heat ORC system.

[0091] Specifically, when the demand for LNG in the demand side decreases, the amount of liquid LNG supplied to the condenser 11 also decreases. In this case, the heat held in the circulation pipeline 20 increases. Therefore, if this held heat exceeds the specified value, an overload occurs in the induction generator 15. At this time, the control of the seawater control valve is executed to release seawater into the seawater bypass pipeline to reduce the heat input to the evaporator 12 (the heat input to the circulation pipeline 20).

[0092] <Method for Starting Power Generation System 10>

[0093] Reference Figure 3 、 Figure 4 , the starting method of the power generation system 10 will be described. Figure 4 is a flowchart showing the operation method of the power generation system 10 according to an embodiment of the present invention. This operation method includes the starting method of the power generation system 10. And at least a part of this operation method is realized by the control process of the processor constituting the controller 90. In the following description, "step" may sometimes be abbreviated as "S", and the processor of the controller 90 may be abbreviated as "processor". Before starting the operation method of the power generation system 10, the turbine 13 stops, and the switching device 14 is in a prohibited state.

[0094] First, a turbine start step (S11) of increasing the main flow rate of the organic medium flowing into the turbine 13 by adjusting the opening degree of the flow control valve 30 is executed. S11 is executed by the processor, and the processor executing S11 is an example of the turbine start control unit 81. By executing S11, the rotational speed of the turbine 13 gradually increases.

[0095] Next, a generator electric rotation step (S13) is executed. In S13, when the rotational speed of the induction generator 15 reaches the target rotational speed, the switching device 14 is switched from the prohibited state to the permitted state, and the power supply from the power system 5 to the induction generator 15 is started. At this moment, the induction generator 15 starts as a motor. S13 is executed by the processor, and the processor executing S13 is an example of the generator electric rotation control unit 82.

[0096] Next, a turbine speed increase step (S15) of further increasing the main flow rate flowing into the turbine 13 by adjusting the opening degree of the flow control valve 30 is executed. S15 is executed by the processor, and the processor executing S15 is an example of the turbine speed increase control unit 83. By executing S15, the rotational speed of the induction generator 15 further increases. In addition, the first flow control valve 31 becomes fully open when the output of the induction generator 15 becomes maximum with respect to the heat input to the evaporator 12 from the warm water supply pipeline 121. In Figure 2 when t≥t2, the full opening of the first stage flow control valve 31 appears.

[0097] After executing S15, the power generation start step (S17) is executed. In S17, the induction generator 15, which has switched from a motor to a generator because its rotational speed has exceeded the synchronous speed, starts supplying power to the power system 5. S17 is a step implemented after executing S15, and in S17, the processor does not require special control processing. After executing S17, Figure 4 the flowchart ends.

[0098] <Method of operating the power generation system 10 when a trip occurs>

[0099] Figure 5 It is a flowchart showing the method of operating the power generation system 10 when a trip occurs.

[0100] When it is determined that the trip condition is satisfied, 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 circuit breaker control unit 85.

[0101] Next, the turbine deceleration step (S23) is executed, in which the bypass flow rate of the organic medium is increased and the main flow rate of the organic medium flowing into the turbine 13 is decreased by controlling the opening degree of the flow control valve 30. In S23 of this example, the turbine 13 stops, and the induction generator 15 also stops. S23 is executed by the processor, and the processor that executes S23 is an example of the turbine deceleration control unit 86.

[0102] Next, the opening degree control of the warm water flow control valve 127 is executed (S24), the warm water bypass flow rate increases, and the heat input to the evaporator 12 decreases.

[0103] Next, the power supply continuation step (S25) is executed, in which the main generator 2 supplements the power that was previously supplied to the specified equipment 7 by the induction generator 15 while continuing to supply power to the specified equipment 7. S25 is automatically executed by executing S21. In S25, no special control processing by the processor is required. Then, Figure 5 the flowchart ends.

[0104] <Method of operating the power generation system 10 when an overload occurs>

[0105] Figure 6 It is a flowchart showing the method of operating 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 result 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. When it is determined that the load on the induction generator 15 is not excessive (S27: "No"), Figure 6 the flowchart ends. After that, the operation of the power generation system 10 continues.

[0106] When it is determined that the load on the induction generator 15 is excessive (S27: "Yes"), a generator load reduction step (S29) is executed. In S29, the opening degree of the warm water flow control valve 127 is controlled to reduce the main warm water flow rate flowing into the evaporator 12 and increase the warm 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. Then, Figure 6 The flowchart of

[0107] As described above, the flow control valve 30 (refer to Figure 1 ) includes a first flow control valve 31 provided in the evaporator turbine pipeline 21 between the inlet 25A of the bypass pipeline 25 and the turbine 13 and a bypass flow control valve 35 provided in the bypass flow control valve 35. Moreover, in the turbine start step (S11) and the turbine speed increase step (S15), the opening degree of the bypass flow control valve 35 is reduced and the opening degree of the first flow control valve 31 is increased. According to the above structure, since the first flow control valve 31 is arranged immediately 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 S11 and S15 respectively.

[0108] <Summary>

[0109] The content described in the above several embodiments is grasped as follows, for example.

[0110] 1) A start-up method for a power generation system (10) according to an embodiment of the present invention is a power generation system including a condenser (11), an evaporator (12), and a turbine (13), wherein

[0111] The power generation system includes:

[0112] A circulation pipeline (20) for causing an organic medium as a heat medium to flow through the condenser, the evaporator, and the turbine in sequence;

[0113] A bypass pipeline (25) for causing the organic medium discharged from the evaporator to bypass the turbine and guiding it to the condenser;

[0114] A flow control valve (30) for adjusting the ratio of the bypass flow rate of the organic medium flowing through the bypass pipeline and the main flow rate of the organic medium flowing into the turbine;

[0115] An induction generator (15) connected to the turbine; and

[0116] A switching device (14) configured to switch between a permitted state that permits conduction between the induction generator and the power system (5) and a prohibited state that prohibits the conduction,

[0117] The induction generator is arranged side by side with a main generator (2) that constitutes the power system and has a larger capacity than the induction generator.

[0118] The starting method of the power generation system includes:

[0119] A turbine starting step (S11) of increasing the main flow rate by adjusting the opening degree of the flow regulating valve;

[0120] A generator electric rotation step (S13) of, when the rotational speed of the induction generator increased by performing the turbine starting step reaches a target speed, switching the switching device from the prohibited state to the permitted state and starting the power supply from the power system to the induction generator;

[0121] A turbine speed increasing step (S15) of, after performing the generator electric rotation step, adjusting the opening degree of the flow regulating valve to further increase the main flow rate; and

[0122] A power generation start step (S17) of, when the rotational speed of the induction generator exceeds a synchronous speed greater than the target speed, the induction generator switched from a motor to a generator starts supplying power to the power system.

[0123] According to the structure of the above 1), the moment of supplying the electric rotation power from the power system to the induction generator is after the rotational speed of the induction generator reaches the target speed. Therefore, the inrush current of the induction generator at the start of electric rotation can be reduced, and the induction generator can be started stably. Also, the reduction effect of the voltage drop of the power system and the reduction effect of the starting torque of the turbine can be obtained together. Moreover, due to the increase in the main flow rate of the organic refrigerant in the turbine speed increasing step, the rotational speed of the induction generator exceeds the synchronous speed, and the induction generator switches from a motor to a generator. In the power generation start step, the induction generator can supply power to the specified equipment together with the main generator. At this time, the induction generator does not supply power to the specified equipment alone. Therefore, it can be configured that an inverter and a converter for the induction generator are not required, thereby reducing the cost of the power generation system. Thus, a starting method of a power generation system that can stably start the induction generator and achieve cost reduction can be realized.

[0124] 2) In several embodiments, according to the starting method of the power generation system described in the above 1), it further includes:

[0125] A turbine deceleration step (S23) of, when a specified trip condition is satisfied after performing the power generation start step, increasing the bypass flow rate and reducing the main flow rate by controlling the opening degree of the flow regulating valve.

[0126] According to the structure in 2) above, the step of decelerating the turbine along with the tripping of the power generation system can be immediately executed.

[0127] 3) In several embodiments, according to the starting method of the power generation system described in 1) or 2) above, wherein,

[0128] In the power generation start step, the induction generator and the main generator together supply power to a specified device (7) connected to the power system.

[0129] The starting method of the power generation system includes:

[0130] A power supply continuation step (S25), in the case where the switching device switches to the prohibited state when a specified tripping condition is satisfied, the main generator supplements the power that was once supplied by the induction generator and continues to supply power to the specified device.

[0131] According to the structure in 3) above, even when the power generation system stops generating electricity along with the tripping of the power generation system, the specified device can continue to operate through the power supply of the main generator.

[0132] 4) In several embodiments, according to the starting method of the power generation system described in 1) or 3) above, wherein,

[0133] The power generation system includes:

[0134] A warm water supply pipe (121) for supplying warm water heated by the exhaust gas discharged from the marine main engine (79) as an evaporation heat source for the organic medium to the evaporator;

[0135] A warm water discharge pipe (122) for the warm water discharged from the evaporator to flow through;

[0136] A warm water bypass pipe (25) connected to the warm water supply pipe and the warm water discharge pipe in a manner that bypasses the evaporator; and

[0137] A warm water flow regulating valve (127) for changing the ratio of the flow rate of the warm water flowing into the evaporator, i.e., the main warm water flow rate, and the warm water bypass flow rate of the warm water flowing through the warm water bypass pipe.

[0138] The starting method of the power generation system further includes:

[0139] A generator load reduction step (S29), in the case where it is determined that the output power of the induction generator exceeds a specified power, controlling the opening degree of the warm water flow regulating valve to reduce the main warm water flow rate and increase the warm water bypass flow rate.

[0140] When the heat content of the warm water flowing into the evaporator increases due to an increase in the output of the marine main engine, the heat input from the warm water to the evaporator increases. As a result, the main flow rate of the organic medium flowing into the turbine increases, and thus the output power of the induction generator may become excessive. Regarding this, according to the structure of the above 4), when it is determined that the output power of the induction generator exceeds the specified power, the main warm water flow rate decreases, so that the load of the induction generator can be prevented from becoming excessive.

[0141] 5) In several embodiments, according to the starting method of the power generation system described in any one of the above 1) to 4), wherein,

[0142] The circulation pipeline includes an evaporator-turbine pipeline connected to the evaporator and the turbine. The evaporator-turbine pipeline is an evaporator-turbine pipeline (21) having an inlet (25A) of the bypass pipeline connected between the evaporator and the turbine.

[0143] The flow rate regulating valve includes:

[0144] A first flow rate regulating valve (31) provided between the inlet of the bypass pipeline and the turbine; and

[0145] A bypass flow rate regulating valve (35) provided in the bypass pipeline.

[0146] In the turbine starting step and the turbine speed increasing step respectively, the opening degree of the bypass flow rate regulating valve is reduced and the opening degree of the first flow rate regulating valve is increased.

[0147] According to the structure of the above 5), the first flow rate regulating valve is arranged immediately in front of the turbine. Therefore, in the turbine starting step and the turbine speed increasing step respectively, the main flow rate can be controlled with high precision.

[0148] 6) The power generation system (10) according to at least one embodiment of the present invention includes a condenser (11), an evaporator (12) and a turbine (13). The power generation system includes:

[0149] A circulation pipeline (20) for allowing an organic medium as a heat medium to flow through the condenser, the evaporator and the turbine in sequence;

[0150] A bypass pipeline (25) for allowing the organic medium discharged from the evaporator to bypass the turbine and guiding it to the condenser;

[0151] A flow rate regulating valve (30) for adjusting the ratio of the bypass flow rate of the organic medium flowing through the bypass pipeline to the main flow rate of the organic medium flowing into the turbine;

[0152] An induction generator (15) connected to the turbine;

[0153] A switching device (14) configured to switch between a permitted state allowing conduction between the induction generator and the power system (5) and a prohibited state prohibiting the conduction, and

[0154] a controller (90),

[0155] wherein the induction generator and a main generator (2) constituting the power system and having a larger capacity than the induction generator are arranged side by side,

[0156] the controller includes:

[0157] a turbine start control unit (81) for increasing the main flow rate by controlling the opening degree of the flow rate regulating valve;

[0158] a generator motor rotation control unit (82) for switching the switching device from the prohibited state to the permitted state when the rotational speed of the induction generator increased by the opening degree control of the turbine start control unit reaches a target rotational speed; and

[0159] a turbine speed increase control unit (83) for further increasing the main flow rate by adjusting the opening degree of the flow rate regulating valve so that the rotational speed of the induction generator exceeds a synchronous rotational speed greater than the target rotational speed after the switching device is switched to the permitted state.

[0160] According to the structure of the above 6), the same effect as that of the above 1) can be obtained.

[0161] Symbol Explanation

[0162] 1 - power generation system, 2 - main generator, 3 - emergency generator, 5 - power system, 7 - equipment, 8 - busbar, 9A to 9C - switching device, 10 - power generation system, 11 - condenser, 12 - evaporator, 13 - turbine, 14 - switching device, 15 - induction generator, 16 - pump device, 20 - circulation pipeline, 21 - evaporator turbine pipeline, 22 - turbine condenser pipeline, 23 - condenser evaporator pipeline, 25 - bypass pipeline, 25A - inlet, 25B - outlet, 29 - on-off valve, 30 - flow rate regulating valve, 31 - first flow rate regulating valve, 35 - bypass flow rate regulating valve, 70 - heating equipment, 79 - marine main engine, 81 - turbine start control unit, 82 - generator motor rotation control unit, 83 - turbine speed increase control unit, 84 - trip determination unit, 85 - open circuit control unit, 86 - turbine deceleration control unit, 87 - overload determination unit, 88 - generator load reduction control unit, 90 - controller, 91 - power measuring device, 98 - rotational speed measuring device, 121 - warm water supply pipeline, 122 - warm water discharge pipeline, 125 - warm water bypass pipeline, 127 - warm water flow rate regulating valve.

Claims

1. A method for starting a power generation system, which is a method for starting a power generation system having a condenser, an evaporator, and a turbine, wherein the power generation system comprises: A circulation pipeline, used to make the organic medium as the heat medium flow through the condenser, the evaporator and the turbine in sequence; a bypass line for allowing the organic medium discharged from the evaporator to bypass the turbine and be directed to the condenser; a flow regulating valve for adjusting a ratio of a bypass flow of the organic medium flowing through the bypass line to a flow rate, i.e., a main flow rate, of the organic medium flowing into the turbine; an induction generator coupled to the turbine; and a switching device configured to switch between a permitted state for permitting conduction between the induction generator and the electric power system and a prohibited state for prohibiting the conduction, The induction generator and a main generator constituting the power system and having a larger capacity than the induction generator are arranged side by side. The starting method of the power generation system comprises: a turbine starting step, increasing the main flow by adjusting the opening of the flow regulating valve; a generator motoring step of switching the switching device from the prohibition state to the permission state to start supplying power from the power system to the induction generator when the rotation speed of the induction generator increased by executing the turbine starting step reaches a target rotation speed; a turbine speed increasing step, after executing the generator electric rotating step, adjusting the opening of the flow regulating valve to further increase the main flow; and In the power generation starting step, when the rotation speed of the induction generator exceeds a synchronous rotation speed that is greater than the target rotation speed, the induction generator starts supplying electric power to the power system by switching from a motor to a generator.

2. The method for starting a power generation system according to claim 1, further comprising: The turbine deceleration step increases the bypass flow rate and decreases the main flow rate by controlling the opening of the flow control valve when a predetermined trip condition is satisfied after the power generation start step is performed.

3. The method for starting a power generation system according to claim 1 or 2, wherein: In the power generation start step, the induction generator supplies power to a predetermined device connected to the power system together with the main generator. The starting method of the power generation system comprises: The power supply continuing step is to continue the power supply to the prescribed device while the main generator supplements the power supplied by the induction generator when the prescribed trip condition is satisfied and the switching device is switched to the prohibited state.

4. The method for starting a power generation system according to claim 1 or 2, wherein: The power generation system comprises: a warm water supply pipeline for supplying warm water heated by exhaust gas discharged from a marine main engine to the evaporator as a heat source for evaporating the organic medium; a warm water discharge pipeline, used for the warm water discharged from the evaporator to flow; a warm water bypass pipeline connected to the warm water supply pipeline and the warm water discharge pipeline in a manner of bypassing the evaporator; and a hot water flow regulating valve for changing the ratio of the flow rate of the hot water flowing into the evaporator, i.e., the main hot water flow rate, and the hot water bypass flow rate of the hot water flowing through the hot water bypass pipe; The starting method of the power generation system further includes: The generator load reducing step controls the opening of the hot water flow rate regulating valve to reduce the main hot water flow rate and increase the hot water bypass flow rate when it is determined that the output power of the induction generator exceeds a predetermined power.

5. The method for starting a power generation system according to claim 1 or 2, wherein: The circulation pipeline includes an evaporator-turbine pipeline connected to the evaporator and the turbine, wherein the evaporator-turbine pipeline is an evaporator-turbine pipeline connected to an inlet of the bypass pipeline between the evaporator and the turbine. The flow regulating valve comprises: a first flow regulating valve provided in the evaporator turbine pipeline between the inlet of the bypass pipeline and the turbine; and A bypass flow regulating valve is arranged in the bypass pipeline. In each of the turbine starting step and the turbine speed increasing step, the opening degree of the bypass flow rate regulating valve is reduced and the opening degree of the first flow rate regulating valve is increased.

6. A power generation system comprising a condenser, an evaporator and a turbine, the power generation system comprising: A circulation pipeline, used to make the organic medium as the heat medium flow through the condenser, the evaporator and the turbine in sequence; a bypass line for allowing the organic medium discharged from the evaporator to bypass the turbine and be directed to the condenser; a flow regulating valve for adjusting a ratio of a bypass flow of the organic medium flowing through the bypass line to a flow rate, i.e., a main flow rate, of the organic medium flowing into the turbine; an induction generator connected to the turbine; a switching device configured to switch between a permitted state for permitting conduction between the induction generator and the electric power system and a prohibited state for prohibiting the conduction, and Controller, The induction generator and a main generator constituting the power system and having a larger capacity than the induction generator are arranged side by side. The controller has: a turbine start control unit, used to increase the main flow by controlling the opening of the flow regulating valve; a generator motoring control section for switching the switching device from the prohibiting state to the allowing state when the rotation speed of the induction generator increased by the opening control of the turbine starting control section reaches a target rotation speed; and The turbine speed increasing control unit is configured to further increase the main flow rate by adjusting the opening of the flow regulating valve so that the rotation speed of the induction generator exceeds a synchronous rotation speed greater than the target rotation speed after the switching device is switched to the permission state.

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