Control device, power generation system, and control method

Abstract

The present invention provides control of a supercharger in response to a reduction in engine RPM. This control device is for controlling an air supply / release valve which is provided in an air supply / release pipe that is branched off from the middle of an air supply pipe connecting a supercharger and an engine and an exhaust bypass valve which is provided in an exhaust bypass pipe for discharging exhaust gas discharged by the engine while bypassing the supercharger. The control device comprises: a means for controlling the exhaust bypass valve on the basis of a target air supply pressure of air supplied from the supercharger to the engine or a mixed gas in which a fuel and the air are mixed; and a means for opening the air supply / release valve when a reduction in RPM of the engine occurs.

Description

Control device, power generation system, and control method

[0001] This disclosure claims priority to Japanese Patent Application No. 2024-022143, filed on February 16, 2024, the contents of which are incorporated herein by reference.

[0002] In a turbocharged engine, the turbocharger supplies compressed air to the combustion chamber. The air combusted with fuel in the combustion chamber is supplied to the turbocharger through an exhaust pipe and then discharged outside the system. High-power diesel engines and premixed gas engines are provided with an intake air discharge pipe that discharges a portion of the air supplied from the turbocharger to the engine outside the system, and an exhaust bypass pipe that bypasses the exhaust gas flow path from the engine to the turbocharger, and highly efficient operation is achieved by controlling the amount of air flowing through these pipes. For example, Patent Document 1 discloses control that achieves an intake air pressure according to the engine operating conditions by adjusting the amount of air flowing through the intake air discharge pipe (intake air bypass passage) and the exhaust bypass pipe.

[0003] With the increase in renewable energy sources, grid-connected power generation facilities are being called upon to maintain the grid. Fluctuations in grid voltage and frequency have various effects on grid-connected power generation facilities. For example, a drop in grid frequency reduces the rotational speed of engine generators connected to the grid. A decrease in engine generator rotational speed shifts the operating point of the turbocharger, which supplies compressed air to the engine generator, toward the smaller wind speed side, increasing the probability of surging. In the case of a premixed gas engine with front-intake intake, the volume from the mixer that mixes fuel and air to the combustion chamber is large. When a load shedding event occurs, the premixed gas present in the piping from the mixer to the combustion chamber may be supplied to the combustion chamber, causing overshoot. When engine rotational speed decreases due to a drop in grid frequency or load shedding, various malfunctions may occur on the turbocharger side.

[0004] Japanese Patent Application Laid-Open No. 2005-240585

[0005] It is necessary to control the turbocharger in response to the decrease in engine speed.

[0006] The present disclosure provides a control device, a power generation system, and a control method that can solve the above-mentioned problems.

[0007] According to one aspect of the present disclosure, a control device controls an intake air release valve provided in an intake air release pipe branching off from midway through an intake pipe connecting a turbocharger and an engine, and an exhaust bypass valve provided in an exhaust bypass pipe that bypasses the turbocharger and discharges exhaust gas emitted by the engine, and includes: means for controlling an opening degree of the exhaust bypass valve based on a target intake pressure of air or a mixed gas of fuel and air that is supplied from the turbocharger to the engine; and means for opening the intake air release valve when a decrease in engine speed occurs.

[0008] According to one aspect of the present disclosure, a power generation system includes an engine, a generator driven by the engine, a turbocharger that supplies compressed air to the engine, an air intake pipe connecting the turbocharger to the engine, an air intake release pipe branching off from the air intake pipe, an air intake release valve provided in the air intake release pipe, an exhaust bypass pipe that discharges exhaust gas emitted by the engine bypassing the turbocharger, an exhaust bypass valve provided in the exhaust bypass pipe, and the above-mentioned control device.

[0009] According to one aspect of the present disclosure, a control method controls an intake air release valve provided in an intake air release pipe branching off midway through an intake pipe connecting a turbocharger to an engine, and an exhaust bypass valve provided in an exhaust bypass pipe that bypasses the turbocharger and discharges exhaust gas emitted by the engine, the control method controlling an opening degree of the exhaust bypass valve based on a target intake pressure of air or a mixed gas of fuel and air that is supplied from the turbocharger to the engine, and opening the intake air release valve when a decrease in engine speed occurs.

[0010] According to the above-described control device, power generation system, and control method, it is possible to suppress the occurrence of surging, overshoot, and the like caused by a drop in the engine speed that occurs when the system frequency drops or load is shedding.

[0011] FIG. 1 is a schematic diagram showing the configuration of a power generation system according to a first embodiment. FIG. 2 is an explanatory diagram of a situation in which a decrease in engine rotation speed occurs according to the first embodiment. FIG. 3 is a diagram showing the characteristics of a turbocharger according to the first embodiment. FIG. 4 is a first diagram showing an example of control according to the first embodiment. FIG. 5 is a second diagram showing an example of control according to the first embodiment. FIG. 6 is a third diagram showing an example of control according to the first embodiment. A flowchart showing an example of control according to the first embodiment. FIG. 7 is a schematic diagram showing the configuration of a power generation system according to a second embodiment. A diagram showing an example of control according to the second embodiment. A flowchart showing an example of control according to the second embodiment. FIG. 8 is a schematic block diagram showing the configuration of a computer according to each embodiment.

[0012] First Embodiment A power generation system 1 according to a first embodiment and its control will be described below with reference to the drawings. (Configuration of the Power Generation System) As shown in FIG. 1 , the power generation system 1 according to the first embodiment includes an air pipe 2a, an intake pipe 2b, an intake air discharge pipe 3, an exhaust bypass pipe 4, a turbocharger 5, an engine 6, a generator 7, a fuel supply pipe 8, an exhaust outlet pipe 9a, an exhaust pipe 9b, and a cooler 10. The turbocharger 5 includes a compressor 5a and an exhaust turbine 5b. Air is supplied to the compressor 5a through the air pipe 2a. The intake pipe 2b connects the compressor 5a to the engine 6. Air compressed by the compressor 5a is cooled by the cooler 10 and supplied to the engine 6 through the intake pipe 2b. Fuel is supplied to the engine 6 through the fuel supply pipe 8. The intake pipe 2b is provided with a pressure sensor 11 for measuring intake air pressure and a temperature sensor 12 for measuring intake air temperature. Values ​​measured by these sensors are transmitted to a control device 100. An intake air release pipe 3, which branches the air flow to the engine 6, is connected to the intake air pipe 2b, and a portion of the air in the intake air pipe 2b can be released to the outside of the system through the intake air release pipe 3. The intake air release pipe 3 is provided with an intake air release valve 3a that adjusts the amount of air released. The opening degree of the intake air release valve 3a is controlled by the control device 100. The exhaust pipe 9b connects the engine 6 to the exhaust turbine 5b. The exhaust outlet pipe 9a is a flow path for discharging exhaust gas from the exhaust gas outlet of the exhaust turbine 5b. The exhaust bypass pipe 4 branches off from the exhaust pipe 9b, bypasses the exhaust turbine 5b, and is connected to the exhaust outlet pipe 9a. The exhaust bypass pipe 4 is provided with an exhaust bypass valve 4a, the opening degree of which is controlled by the control device 100. The engine 6 is provided with a rotation speed sensor 13 that measures the rotation speed of the engine 6 and an output sensor 14 that measures the output of the engine 6. The values ​​measured by these sensors are transmitted to the control device 100. The generator 7 is driven by the engine 6 to generate electricity. The generator 7 is connected to the grid 20 and supplies the generated power to the grid 20. A circuit breaker 16a is provided on the line connecting the generator 7 to the grid 20, and the generator 7 and the grid 20 can be switched between connected and disconnected by turning the circuit breaker 16a on (connected) and off (disconnected).When the power generation system 1 is operated independently without being connected to the grid 20, a circuit breaker 16b is provided on the line connecting the generator 7 to the on-site equipment in order to supply the generated power to equipment (not shown) within the power plant. By turning the circuit breaker 16b on (connected) or off (disconnected), the generator 7 and the on-site equipment are switched between connected and disconnected. Circuit breaker signals indicating whether the circuit breakers 16a and 16b are in a connected state or a disconnected state are each transmitted to the control device 100. The frequency sensor 15 measures the grid frequency. The frequency of the grid 20 measured by the frequency sensor 15 is transmitted to the control device 100. The control device 100 is configured as a computer, and acquires measurement values ​​from the sensors 11 to 15 and circuit breaker signals from the circuit breakers 16a and 16b to control the intake air release valve 3a and the exhaust bypass valve 4a. For example, the control device 100 calculates a target boost pressure for efficiently operating the engine 6 based on the boost pressure, rotation speed, and output, and controls the opening of the exhaust bypass valve 4a based on this target boost pressure, thereby controlling the amount of air supplied to the engine 6 to a target value. For example, when a drop in the frequency of the system 20 (a drop in the rotation speed of the engine 6) or a load shedding occurs, the control device 100 temporarily opens the intake air release valve 3a to increase the surging margin and avoid surging.

[0013] In the power generation system 1, when the system frequency decreases, the rotation speed of the engine 6 decreases. As shown in FIG. 2 , the frequency f (rotation speed of the engine 6) also decreases after load application or load rejection. When the rotation speed of the engine 6 decreases, the operating line of the turbocharger 5 shifts toward the small airflow side, reducing the surging margin of the turbocharger 5 and increasing the probability of surging. FIG. 3 schematically shows the characteristic curve of the turbocharger 5. The vertical axis of the graph in FIG. 3 represents the pressure ratio, and the horizontal axis represents the flow rate of air supplied by the turbocharger 5. Line 30 represents the boundary between the operating region where surging occurs in the turbocharger 5 (left side of 30) and the operating region where surging does not occur (right side of 30), and line 32 represents the operating line of the turbocharger 5 during rated operation. When the rotation speed of the engine 6 decreases, the operating line of the turbocharger 5 changes from line 32 to line 31. As a result, the distance to line 30 becomes shorter (i.e., the surging margin decreases), increasing the probability of surging. In particular, in a premixed gas engine, when surging occurs, the mixed gas flows back into the intake chamber due to blowback. In the next cycle, the blown-back mixture and fuel gas are supplied to the combustion chamber, reducing the excess air ratio and increasing the mean effective pressure (Pmi). This can lead to abnormal combustion, such as pre-ignition or knocking, which can damage the combustion chamber. A typical approach to ensuring the surging margin of the turbocharger 5 is to narrow the diffuser. However, if an attempt is made to ensure the surging margin of the turbocharger 5 by installing a diffuser manufactured in this manner, the overall efficiency of the turbocharger 5 decreases, including in states where no frequency drop occurs, such as during rated operation. A decrease in the efficiency of the turbocharger 5 leads to a decrease in the thermal efficiency of the engine 6. Therefore, in this embodiment, when the engine speed drops, the intake air release valve 3a is temporarily opened to release air outside the system through the intake air release pipe 3, thereby increasing the surging margin. In other situations, the intake air release valve 3a is closed to operate the turbocharger 5 at high efficiency. Line 33 in Figure 3 is the operating line of the turbocharger 5 when the intake air release valve 3a is opened. As shown in the figure, the surging margin can be increased by opening the intake air release valve 3a. Opening the intake air release valve 3a can increase the surging margin, but the efficiency of the turbocharger 5 decreases. Therefore, in a state where there is no decrease in engine speed, the intake air release valve 3a is closed to prevent a decrease in the efficiency of the turbocharger 5.On the other hand, the turbocharger efficiency and surging margin of the exhaust bypass valve 4a are generally constant regardless of the valve opening degree. By opening the exhaust bypass valve 4a, the thermal efficiency of the engine and the overall efficiency of the plant can be improved. For example, by opening the exhaust bypass valve 4a, the temperature of the exhaust gas discharged from the exhaust outlet pipe 9a can be increased, which is effective from the viewpoint of exhaust heat recovery.

[0014] (Control During Frequency Drop) Next, control of the intake air release valve 3a and the exhaust bypass valve 4a when the frequency of the system 20 (the rotational speed of the engine 6) drops will be described with reference to FIG. 4. Graph 41 in FIG. 4 shows the change in the system frequency. Graph 42 shows the change in the opening degree of the exhaust bypass valve 4a. Graph 43 shows the change in the opening degree of the intake air release valve 3a. The same position on the horizontal axis of graphs 41 to 43 indicates the same time. Regardless of the system frequency, the control device 100 always controls the opening degree of the exhaust bypass valve 4a so that the pressure measured by the pressure sensor 11 becomes the target boost pressure calculated from a map of Pme (break mean effective pressure) and boost pressure. For example, the control device 100 calculates Pme by substituting the rotational speed measured by the rotational speed sensor 13 and the output measured by the output sensor 14 into the formula for Pme, and then calculates the target boost pressure corresponding to Pme using a map, table, function, or the like that defines the relationship between Pme and the target boost pressure. The control device 100 then refers to a correspondence table between the target air intake pressure and the opening degree of the exhaust bypass valve 4a, calculates the opening degree of the exhaust bypass valve 4a corresponding to the target air intake pressure, and controls the exhaust bypass valve 4a. Graph 42 shows the progress of the opening degree of the exhaust bypass valve 4a under such control.

[0015] The control device 100 monitors the frequency of the grid 20 measured by the frequency sensor 15, and when the frequency drops to a predetermined threshold or when it detects that the rate of frequency drop is equal to or greater than the predetermined threshold, it controls the opening of the intake air release valve 3a to suppress surging. Three examples of the method for controlling the intake air release valve 3a will be described below. (1) Open at a constant opening: When the control device 100 detects a drop in the grid frequency at time T1, it opens the intake air release valve 3a at a constant opening. Graph 43 shows this control. (2) Open in stages according to the rotational speed: When the control device 100 detects a drop in the grid frequency at time T1, it opens the intake air release valve 3a in stages according to the rotational speed measured by the rotational speed sensor 13. For example, the control device 100 stores a table correlating the rotation speed (or rotation speed range) of the engine 6 with the opening degree of the intake air release valve 3a (the opening degree increases as the rotation speed decreases), and references this table to read the valve opening degree corresponding to the rotation speed measured by the rotation speed sensor 13, and controls the intake air release valve 3a. (3) Stepwise Opening According to Rotation Speed ​​and Output When the control device 100 detects a drop in the system frequency at time T1, it opens the intake air release valve 3a stepwise according to the rotation speed measured by the rotation speed sensor 13 and the output measured by the output sensor 14. For example, the control device 100 stores a table correlating the rotation speed (or rotation speed range) and output (or output range) of the engine 6 with the opening degree of the intake air release valve 3a, and references this table to read the valve opening degree corresponding to the values ​​measured by the rotation speed sensor 13 and the output sensor 14, and controls the intake air release valve 3a.

[0016] When the grid frequency drops due to fluctuations in the renewable energy power source or the like, a surging margin is ensured by one of the controls (1) to (3). Meanwhile, because the amount of air supplied to the engine 6 decreases, the opening of the exhaust bypass valve 4a is reduced to ensure the intake air pressure. The control device 100 may be configured to monitor the rotation speed measured by the rotation speed sensor 13 instead of the grid frequency measured by the frequency sensor 15, and to perform control to open the intake air release valve 3a when the rotation speed drops to a predetermined threshold value or when it detects that the rate of decrease in the rotation speed is equal to or greater than the predetermined threshold value. The control device 100 may close the intake air release valve 3a, for example, after the drop in the grid frequency has stopped.

[0017] (Control when load is applied) Next, referring to Figure 5, control when load is applied during islanding operation separated from the grid 20 and when a load is applied during a transition from grid operation to islanding operation will be described. Graph 51 in Figure 5 shows the change in the required power generation amount. Graph 52 shows the change in the opening degree of the exhaust bypass valve 4a. Graph 53 shows the change in the opening degree of the air supply release valve 3a. The same position on the horizontal axis of graphs 51 to 53 indicates the same time. Before and after load application, the control device 100 constantly controls the opening degree of the exhaust bypass valve 4a so that the pressure measured by the pressure sensor 11 becomes the target air supply pressure calculated from a map of Pme and air supply pressure. This control is as described in Figure 4.

[0018] As explained with reference to FIG. 2, a drop in frequency also occurs when a load is applied, reducing the surging margin. When the control device 100 receives a signal from the circuit breaker 16b indicating that the circuit breaker 16b should be turned on, it controls the opening of the intake air release valve 3a to suppress surging. The following two examples will be explained as methods for controlling the intake air release valve 3a. (1) Open at a fixed opening: When the control device 100 receives a circuit breaker signal (on) at time T1, it opens the intake air release valve 3a at a fixed opening for a predetermined time, and closes the intake air release valve 3a after the predetermined time has elapsed. Graph 53 shows this control. (2) Open according to output: When the control device 100 receives a circuit breaker signal (on) at time T1, it opens the intake air release valve 3a according to the output measured by the output sensor 14. For example, the control device 100 may store a table correlating the output of the engine 6 with the opening degree of the intake air release valve 3a (the lower the output, the larger the opening degree). The control device 100 references this table to read the valve opening degree corresponding to the output measured by the output sensor 14 and opens the intake air release valve 3a. For example, the control device 100 may open the intake air release valve 3a for a certain period of time and then close the intake air release valve 3a, or may close the intake air release valve 3a after the output measured by the output sensor 14 reaches a predetermined value. In this way, when a load-applied circuit breaker signal is detected during isolated operation, the intake air release valve 3a is temporarily opened to ensure a surging margin. Meanwhile, because the amount of air supplied to the engine 6 decreases, the opening degree of the exhaust bypass valve is reduced to ensure intake pressure.

[0019] (Control During Load Reduction) Next, with reference to FIG. 6 , control when a large load reduction occurs during islanding operation separated from the grid 20 or when switching from grid operation to islanding operation will be described. Graph 61 in FIG. 6 shows the change in the required power generation amount. Graph 62 shows the change in the aperture of the exhaust bypass valve 4a. Graph 63 shows the change in the aperture of the air supply release valve 3a. The same position on the horizontal axis of graphs 61 to 63 indicates the same time. Before and after load shedding, the control device 100 constantly controls the aperture of the exhaust bypass valve 4a so that the pressure measured by the pressure sensor 11 becomes the target air supply pressure calculated from a map of Pme and air supply pressure. This control has been described with reference to FIG. 4 .

[0020] As explained with reference to FIG. 2, a drop in frequency also occurs during load rejection, reducing the surging margin. When the control device 100 receives a signal from the circuit breaker 16a indicating that the circuit breaker 16a should be turned off, it controls the opening of the intake air release valve 3a to suppress surging. The following two examples are given as methods for controlling the intake air release valve 3a. These controls are similar to those explained with reference to FIG. 5. (1) Open at a fixed opening: When the control device 100 receives a circuit breaker signal (off) at time T1, it opens the intake air release valve 3a at a fixed opening for a predetermined time, and closes the intake air release valve 3a after the predetermined time has elapsed. Graph 63 shows this control. (2) Open according to output: When the control device 100 receives a circuit breaker signal (off) at time T1, it opens the intake air release valve 3a according to the output measured by the output sensor 14. For example, the control device 100 may close the intake air release valve 3a after opening it for a certain period of time, or may close the intake air release valve 3a after the output measured by the output sensor 14 reaches a predetermined value. In this way, when a load shedding circuit breaker signal is detected, the control device 100 temporarily opens the intake air release valve 3a, thereby providing a surge margin and preventing surging.

[0021] (Operation) Next, control of the intake air release valve 3a and the exhaust bypass valve 4a according to this embodiment will be described with reference to FIG. 7 . FIG. 7 is a flowchart illustrating an example of control according to the first embodiment. The control device 100 controls the exhaust bypass valve 4a so that the boost pressure becomes a target boost pressure calculated from a map of Pme and boost pressure (step S1). This control is performed continuously while the turbocharger 5 is in operation. Next, the control device 100 determines whether there is a drop in the grid frequency or a fluctuation in the required power generation output (step S2). For example, the control device 100 determines whether there is a drop in the frequency or a fluctuation in the required power generation output based on the measurement value of the frequency sensor 15 or the circuit breaker signals issued by the circuit breakers 16a and 16b. If there is no drop in the frequency or the like (step S2; No), the process proceeds to step S4. If there is a drop in the frequency or the like (step S2; Yes), the control device 100 controls the intake air release valve 3a to temporarily open (step S3). For example, the control device 100 may (1) open the intake air release valve 3a at a constant opening degree, (2) open the intake air release valve 3a at an opening degree corresponding to the rotational speed of the engine 6, (3) open the intake air release valve 3a at an opening degree corresponding to the output of the engine 6, or (4) open the intake air release valve 3a at an opening degree corresponding to the rotational speed and output of the engine 6. The control device 100 may close the intake air release valve 3a when a certain time has elapsed since opening the intake air release valve 3a, or may close the intake air release valve 3a when a drop in system frequency or fluctuations in required power output have stabilized. Even during the opening and closing control of the intake air release valve 3a, the control device 100 continues to control the exhaust bypass valve 4a in step S1. The control device 100 repeatedly performs the processes from step S2 onwards until the operation of the turbocharger 5 is stopped (step S4; No). During this time, the control of the exhaust bypass valve 4a in step S1 continues. If the operation of the supercharger 5 is to be stopped (step S4; Yes), the processing of FIG. 7 is ended.

[0022] (Effects) According to the first embodiment, when the rotation speed of the engine 6 decreases due to fluctuations in the required power generation output, such as a drop in the system frequency or a sudden load change, the air flow rate supplied to the turbocharger 5 is maintained (or increased) instead of opening the intake air release valve 3a to release the air supplied to the engine 6. This shifts the operating line of the turbocharger 5 to the small air volume side, preventing a decrease in the surging margin of the turbocharger 5 and suppressing the occurrence of surging. By opening the intake air release valve 3a only in situations where a drop in the rotation speed of the engine 6 is predicted or estimated, the turbocharger 5 can be operated without reducing its operating efficiency in other situations. There is no need to modify the hardware, such as by installing a diffuser with a surging countermeasure, to prepare for a drop in the system frequency, which rarely occurs, and the system can be easily introduced because it can respond to a drop in engine rotation speed simply by controlling the valve.

[0023] Second Embodiment A power generation system 1′ according to a second embodiment and its control will be described below with reference to the accompanying drawings. FIG. 8 is a schematic diagram illustrating the configuration of a power generation system according to the second embodiment. FIG. 8 illustrates a schematic diagram of a power generation system 1′ including a premixed gas engine with intake before the turbocharger. Unlike the gas engine illustrated in FIG. 1 , a mixer 2c is provided upstream of the compressor 5a. An air pipe 2a and a fuel supply pipe 8 are connected to the mixer 2c, and the fuel gas and air are mixed in the mixer 2c. The mixed gas (referred to as a mixed gas) is supplied to the compressor 5a of the turbocharger 5 through an intake pipe 2d. The mixed gas compressed by the compressor 5a is cooled in a cooler 10 and supplied to the combustion chamber 6a of the engine 6 through an intake pipe 2e. Exhaust gas combusted by the engine 6 is collected in an exhaust manifold 9c and supplied to the exhaust turbine 5b through an exhaust pipe 9b. The other configurations are the same as those described in FIG. 1. Sensors are omitted from FIG. 8 . In the case of a premixed gas engine with intake before the turbocharger shown in Fig. 8, the volume of the piping from the mixer 2c to the combustion chamber 6a is large, and this space is filled with mixed gas during operation. If a load dump occurs in this state, the mixed gas present between the mixer 2c and the combustion chamber 6a may be supplied to the combustion chamber and burned, causing an overshoot in the output of the engine 6. Therefore, in the second embodiment, the intake air release valve 3a is opened during load dump to release the mixed gas, thereby suppressing the overshoot.

[0024] (Control During Load Shedding) With reference to FIG. 9 , the control when separating from the grid 20 (load shedding) and transitioning to islanded operation will be described. Graph 91 in FIG. 9 shows the change in the required power generation amount over time. Graph 92 shows the change in the opening degree of the exhaust bypass valve 4a. Graph 93 shows the change in the opening degree of the air supply release valve 3a. The same position on the horizontal axis of graphs 91 to 93 indicates the same time. When the control device 100′ receives a circuit breaker signal indicating that the circuit breaker 16a or the circuit breaker 16b should be turned off, the control device 100′ performs control to suppress overshoot. When the control device 100′ receives a circuit breaker signal (off) at time T1, the control device 100′ performs control to fully open the exhaust bypass valve 4a after a predetermined time has elapsed (graph 92). The control device 100′ performs control to open the air supply release valve 3a. The following two examples will be described as methods for controlling the air supply release valve 3a. These controls are similar to those described with reference to FIG. 5 . (1) Open at a constant opening degree. When the control device 100′ receives a circuit breaker signal (OFF) at time T1, it opens the intake air release valve 3a at a constant opening angle for a predetermined time and closes the intake air release valve 3a after the predetermined time has elapsed. Graph 93 illustrates this control. (2) Opening According to Output. When the control device 100′ receives a circuit breaker signal (OFF) at time T1, it opens the intake air release valve 3a according to the output measured by the output sensor 14. For example, the control device 100′ may close the intake air release valve 3a after opening it for a predetermined time, close the intake air release valve 3a after the output measured by the output sensor 14 reaches a predetermined value, or close the intake air release valve 3a after the exhaust bypass valve 4a is fully opened. This control can be applied during load shedding or emergency shutdown. After performing the control described in FIG. 9, operation may be continued and the system may be reconnected to the grid 20.

[0025] (Operation) Next, control of the intake air release valve 3a and the exhaust bypass valve 4a according to this embodiment will be described with reference to FIG. 10 . FIG. 10 is a flowchart illustrating an example of control according to the second embodiment. The control device 100′ controls the exhaust bypass valve 4a so that the boost pressure of the mixed gas becomes a target boost pressure calculated from a map of Pme and boost pressure (step S11). This control is performed continuously while the turbocharger 5 is in operation. Next, the control device 100′ determines whether a load dump has occurred (step S12). For example, the control device 100′ determines whether a load dump has occurred based on a circuit breaker signal issued by the circuit breaker 16a. If a load dump has not occurred (step S12; No), the control device 100′ continues the processing of step S1. If a load dump has occurred (step S12; Yes), the control device 100′ controls the intake air release valve 3a to open (step S13). For example, the control device 100′ may (1) open the intake air release valve 3a at a constant opening, or (2) open the intake air release valve 3a at an opening corresponding to the output of the engine 6. When a certain time has elapsed since the load shedding was detected, the control device 100' fully opens the exhaust bypass valve 4a (step S14).

[0026] (Effect) According to the second embodiment, it is possible to prevent the output of the engine 6 from overshooting due to fluctuations in the required power generation output, such as load shedding.

[0027] 11 is a schematic block diagram showing the configuration of a computer according to an embodiment. The computer 900 includes a CPU 901, a main storage device 902, an auxiliary storage device 903, an input / output interface 904, and a communication interface 905. The above-described control devices 100 and 100′ are implemented in the computer 900. The above-described functions are stored in the auxiliary storage device 903 in the form of a program. The CPU 901 reads the program from the auxiliary storage device 903, loads it into the main storage device 902, and executes the above-described processing in accordance with the program. The CPU 901 allocates a storage area in the main storage device 902 in accordance with the program. The CPU 901 allocates a storage area in the auxiliary storage device 903 for storing data being processed in accordance with the program.

[0028] In another embodiment, the computer 900 may include a custom large-scale integrated circuit (LSI) such as a programmable logic device (PLD) in addition to or instead of the above configuration. Examples of PLDs include programmable array logic (PAL), generic array logic (GAL), complex programmable logic device (CPLD), and field programmable gate array (FPGA). In this case, some or all of the functions realized by the processor 91 may be realized by the integrated circuit. Such an integrated circuit is also an example of a processor.

[0029] A program for implementing all or part of the functions of the control device 100, 100' may be recorded on a computer-readable recording medium, and the program may be loaded into a computer system and executed to perform processing by each functional unit. The term "computer system" as used herein includes hardware such as an OS and peripheral devices. If a WWW system is used, the term "computer system" also includes a homepage provision environment (or display environment). The term "computer-readable recording medium" refers to portable media such as CDs, DVDs, and USBs, as well as storage devices such as hard disks built into the computer system. If the program is distributed to the computer 900 via a communication line, the computer 900 may load the program into the main storage device 902 and execute the processing described above. The program may be for implementing part of the functions described above, or may be capable of implementing the functions described above in combination with a program already stored in the computer system.

[0030] As described above, several embodiments according to the present disclosure have been described, but all of these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents as defined in the claims, as well as in the scope and spirit of the invention.

[0031] <Additional Notes> The control device, power generation system, and control method described in each embodiment can be understood, for example, as follows.

[0032] (1) A control device according to a first aspect controls an intake release valve provided in an intake release pipe branched from an intake pipe connecting a turbocharger to an engine, and an exhaust bypass valve provided in an exhaust bypass pipe that bypasses the turbocharger and discharges exhaust gas emitted by the engine, the control device comprising: means for controlling an opening degree of the exhaust bypass valve based on a target intake pressure of air or a mixed gas of fuel and air that is supplied from the turbocharger to the engine; and means for opening the intake release valve when a reduction in engine speed occurs. This makes it possible to avoid surging and output overshoot that occur when the engine speed reduces.

[0033] (2) A control device according to a second aspect is the control device of (1), wherein the means for controlling the exhaust bypass valve calculates the boost pressure corresponding to the break mean effective pressure of the engine based on a break mean effective pressure calculated from the engine speed and the output of the engine and information defining the relationship between the break mean effective pressure and a boost pressure from the turbocharger to the engine, and controls the exhaust bypass valve so as to achieve the calculated boost pressure. This enables the engine to be operated efficiently.

[0034] (3) A control device according to a third aspect is the control device of (1) to (2), wherein the means for opening the intake air release valve opens the intake air release valve at a constant opening when a decrease in engine speed occurs, thereby making it possible to avoid surging and output overshoot that occur when the engine speed decreases.

[0035] (4) A control device according to a fourth aspect is the control device of (1) to (2), wherein the means for opening the intake air release valve opens the intake air release valve at an opening degree corresponding to the engine speed and / or the engine output when a decrease in engine speed occurs, thereby making it possible to avoid surging and output overshoot that occur when the engine speed decreases.

[0036] (5) A fifth aspect of the control device is the control device of (1) to (4), wherein the case where the engine speed decreases is when the frequency of the power grid to which the generator that generates electricity by driving the engine is connected decreases, when a load shedding occurs, or when a load is added, thereby making it possible to predict and estimate the decrease in engine speed.

[0037] (6) A power generation system according to a sixth aspect includes an engine, a generator driven by the engine, a turbocharger that supplies compressed air to the engine, an air intake pipe that connects the turbocharger to the engine, an air intake release pipe that branches off from the air intake pipe, an air intake release valve provided in the air intake release pipe, an exhaust bypass pipe that discharges exhaust gas emitted by the engine, bypassing the turbocharger, an exhaust bypass valve provided in the exhaust bypass pipe, and the control device according to claim 1 or claim 2.

[0038] (7) A control method according to a seventh aspect is a control method for controlling an intake release valve provided in an intake release pipe branched off midway through an intake pipe connecting a turbocharger to an engine, and an exhaust bypass valve provided in an exhaust bypass pipe that bypasses the turbocharger and discharges exhaust gas emitted by the engine, in which the opening of the exhaust bypass valve is controlled based on a target intake pressure of air or a mixed gas of fuel and air that is supplied from the turbocharger to the engine, and the intake release valve is opened when a decrease in engine speed occurs.

[0039] According to the above-described control device, power generation system, and control method, it is possible to suppress the occurrence of surging, overshoot, and the like caused by a drop in the engine speed that occurs when the system frequency drops or load is shedding.

[0040] DESCRIPTION OF SYMBOLS 1, 1'... Power generation system 2a... Air pipe 2b... Air intake pipe 2c... Mixer 2d... Air intake pipe 2e... Air intake pipe 3... Air intake release pipe 3a... Air intake release valve 4... Exhaust bypass pipe 4a... Exhaust bypass valve 5... Turbocharger 5a... Compressor 5b... Exhaust turbine 6... Engine 7... Generator 8... Fuel supply pipe 9a... Exhaust outlet pipe 9b... Exhaust pipe 9c... Exhaust manifold 10... Cooler 11... Pressure sensor 12... Temperature sensor 13... Rotation speed sensor 14... Output sensor 15... Frequency sensor 16a, 16b... Circuit breaker 20... System 100, 100'... Control device 901... CPU 902... Main memory device 903... Auxiliary memory device 904... Input / output interface 905... Communication interface

Claims

1. A control device that controls an intake release valve provided in an intake release pipe branched off from the middle of an intake pipe connecting a turbocharger to an engine, and an exhaust bypass valve provided in an exhaust bypass pipe that bypasses the turbocharger and discharges exhaust gas emitted by the engine, the control device comprising: means for controlling the opening of the exhaust bypass valve based on a target intake pressure of air or a mixed gas of fuel and air that is supplied from the turbocharger to the engine; and means for opening the intake release valve when a decrease in engine speed occurs.

2. A control device according to claim 1, wherein the means for controlling the exhaust bypass valve calculates the boost pressure corresponding to the net mean effective pressure of the engine based on a net mean effective pressure calculated from the engine speed and output of the engine and information defining the relationship between the net mean effective pressure and the boost pressure from the turbocharger to the engine, and controls the exhaust bypass valve so as to achieve the calculated boost pressure.

3. A control device as set forth in claim 1 or claim 2, wherein the means for opening the intake and release valve opens the intake and release valve at a constant opening when a decrease in engine speed occurs.

4. A control device as described in claim 1 or claim 2, wherein the means for opening the intake and release valve opens the intake and release valve at an opening degree corresponding to the engine speed and / or the engine output when a decrease in the engine speed occurs.

5. A control device as described in claim 1 or claim 2, wherein a decrease in the engine speed occurs when the frequency of the power grid to which the generator that generates electricity by driving the engine is connected decreases, when a load shedding occurs, or when a load is added.

6. A power generation system comprising an engine, a generator driven by the engine, a turbocharger that supplies compressed air to the engine, an air intake pipe connecting the turbocharger to the engine, an air intake release pipe branching off from the air intake pipe, an air intake release valve provided in the air intake release pipe, an exhaust bypass pipe that discharges exhaust gas emitted by the engine bypassing the turbocharger, an exhaust bypass valve provided in the exhaust bypass pipe, and a control device as described in claim 1 or claim 2.

7. A control method for controlling an intake release valve provided in an intake release pipe branching off from the intake pipe connecting a turbocharger to an engine, and an exhaust bypass valve provided in an exhaust bypass pipe that bypasses the turbocharger and discharges exhaust gas emitted by the engine, the control method controlling the opening of the exhaust bypass valve based on a target intake pressure of air or a mixed gas of fuel and air supplied from the turbocharger to the engine, and opening the intake release valve when a drop in engine speed occurs.

Images