Control device, power generation system, and control method

Abstract

To provide control of a supercharger that copes with a reduction in engine rotation speed.SOLUTION: A control device controls a supply air release valve provided in a supply air release pipe branched from the middle of a supply air pipe connecting a supercharger and an engine, and an exhaust air bypass valve provided in an exhaust air bypass pipe for discharging exhaust gas discharged by the engine, by bypassing the supercharger, and comprises means for controlling the exhaust air bypass valve on the basis of a target supply air pressure of air to be supplied to the engine from the supercharger, or mixed gas made by mixing fuel and air, and means for opening the supply air release valve when a reduction in rotation speed of the engine occurs.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a control device, a power generation system, and a control method. [Background technology]

[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. Furthermore, in the case of premixed gas engines with front-intake turbochargers, 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 between the mixer and 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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-240585 Summary of the Invention [Problem to be solved by the invention]

[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 problems. [Means for solving the problem]

[0007] The control device disclosed herein is a control device that 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, and includes: means for controlling the opening of the exhaust bypass valve based on a target intake air 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] The power generation system of the present disclosure 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 above-mentioned control device.

[0009] Furthermore, according to a control method of the present disclosure, there is provided a control method for controlling an intake air release valve provided in an intake air release pipe branching off midway through an intake air 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 degree of the exhaust bypass valve based on a target intake air 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. [Effects of the Invention]

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

[0011] [Figure 1] 1 is a schematic diagram showing a configuration of a power generation system according to a first embodiment. [Figure 2] 5A and 5B are diagrams illustrating a situation in which a decrease in engine speed occurs in the first embodiment. [Figure 3] FIG. 3 is a diagram showing characteristics of the turbocharger according to the first embodiment. [Figure 4] FIG. 2 is a first diagram showing an example of control according to the first embodiment. [Figure 5] FIG. 4 is a second diagram showing an example of control according to the first embodiment. [Figure 6] FIG. 10 is a third diagram illustrating an example of control according to the first embodiment. [Figure 7] 4 is a flowchart illustrating an example of control according to the first embodiment. [Figure 8] FIG. 4 is a schematic diagram showing the configuration of a power generation system according to a second embodiment. [Figure 9] FIG. 10 is a diagram illustrating an example of control according to the second embodiment. [Figure 10] 10 is a flowchart illustrating an example of control according to the second embodiment. [Figure 11]FIG. 2 is a schematic block diagram showing the configuration of a computer according to each embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] First Embodiment The power generation system 1 of the first embodiment and its control will be described below with reference to the drawings. (Power generation system configuration) As shown in FIG. 1, a 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. The 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 the intake air pressure and a temperature sensor 12 for measuring the intake air temperature. Values ​​measured by these sensors are sent 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 some 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 a control device 100. An exhaust pipe 9b connects the engine 6 to the exhaust turbine 5b. An exhaust outlet pipe 9a is a flow path for discharging exhaust gas from the exhaust gas outlet of the exhaust turbine 5b. An 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. An exhaust bypass valve 4a is provided in the exhaust bypass pipe 4, and the opening degree of the exhaust bypass valve 4a is controlled by a control device 100. The engine 6 is provided with a rotation speed sensor 13 that measures the engine 6 rotation speed and an output sensor 14 that measures the engine 6 output. The values ​​measured by these sensors are sent 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 are switched between connected and disconnected by turning the circuit breaker 16a on (connected) and off (disconnected).Furthermore, 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 the measurement values ​​from the sensors 11 to 15 and the 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. Also, 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, increasing the surging margin and avoiding surging.

[0013] In the power generation system 1, when the system frequency drops, the rotation speed of the engine 6 drops. Furthermore, as shown in Figure 2, the frequency f (rotation speed of the engine 6) also drops after a load is applied or removed. When the rotation speed of the engine 6 drops, 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. Figure 3 shows a schematic diagram of the characteristic curve of the turbocharger 5. The vertical axis of the graph in Figure 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). Line 32 represents the operating line of the turbocharger 5 during rated operation. When the rotation speed of the engine 6 drops, the operating line of the turbocharger 5 shifts from line 32 to line 31. This shortens the distance to line 30 (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. Then, 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 a diffuser manufactured in this manner is used to ensure the surging margin of the turbocharger 5, the efficiency of the turbocharger 5 as a whole decreases, including in states where no frequency drop occurs, such as during rated operation. A decrease in the efficiency of the turbocharger 5 reduces 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 the engine speed does not decrease, 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. Also, opening the exhaust bypass valve 4a can improve the thermal efficiency of the engine and the overall efficiency of the plant. For example, opening the exhaust bypass valve 4a can increase the temperature of the exhaust gas discharged from the exhaust outlet pipe 9a, which is effective from the viewpoint of exhaust heat recovery.

[0014] (Control when frequency drops) 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 according 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 of the exhaust bypass valve 4a, calculates the opening of the exhaust bypass valve 4a according to the target air intake pressure, and controls the exhaust bypass valve 4a. Graph 42 shows the progress of the opening of the exhaust bypass valve 4a under such control.

[0015] The control device 100 monitors the frequency of the system 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 performs control to open the intake air release valve 3a to suppress surging. Three examples of the method for controlling the intake air release valve 3a are described below. (1) Open at a fixed opening When the control device 100 detects a drop in the system frequency at time T1, it opens the intake air release valve 3a at a fixed opening. Graph 43 shows this control. (2) Opens in stages according to the rotation speed. When the control device 100 detects a drop in the system frequency at time T1, it opens the intake air release valve 3a in stages according to the rotation speed measured by the rotation speed sensor 13. For example, the control device 100 holds a table that associates the rotation speed (or range of rotation speed) 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 by referring to this table, reads the valve opening degree that corresponds to the rotation speed measured by the rotation speed sensor 13 and controls the intake air release valve 3a. (3) Opens in stages 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 in stages 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 holds a table that associates the rotation speed (or rotation speed range) of the engine 6, the output (or output range) of the engine 6, and the opening degree of the intake air release valve 3a, and by referring to this table, reads the valve opening degree that corresponds 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, since 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 frequency of the grid 20 measured by the frequency sensor 15, and to perform control to open the intake air release valve 3a when it detects that the rotation speed has dropped to a predetermined threshold or that the rate of decrease in the rotation speed is equal to or greater than the predetermined threshold. The control device 100 may also close the intake air release valve 3a after the drop in the grid frequency has stopped, for example.

[0017] (Control when load is applied) Next, referring to FIG. 5, we will explain the control when load is applied during islanding operation separated from the grid 20 and when switching from grid operation to islanding operation. Graph 51 in FIG. 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 intake 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 intake pressure calculated from a map of Pme and air intake pressure. This control is as explained in FIG. 4.

[0018] As explained with reference to Figure 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 performs control to open 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 then closes the intake air release valve 3a after the predetermined time has elapsed. Graph 53 shows this control. (2) Opens 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 stores a table that associates 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, reads 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 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 circuit breaker signal indicating load application is detected during islanding operation, the control device 100 temporarily opens the intake air release valve 3a to ensure a surging margin. Meanwhile, because the amount of air supplied to the engine 6 decreases, the control device 100 reduces the opening degree of the exhaust bypass valve to ensure intake pressure.

[0019] (Control during load reduction) Next, with reference to FIG. 6, control in the case where a large load reduction occurs during islanding operation when the system is disconnected from 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 opening degree of exhaust bypass valve 4a. Graph 63 shows the change in the opening degree of 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, control device 100 constantly controls the opening degree of exhaust bypass valve 4a so that the pressure measured by 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 Figure 2, a drop in frequency also occurs during load shedding, reducing the surge tolerance. When the control device 100 receives a signal from the circuit breaker 16a indicating that the circuit breaker 16a should be turned off, it performs control to open 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. These controls are similar to those explained with reference to Figure 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 then closes the intake air release valve 3a after the predetermined time has elapsed. Graph 63 shows this control. (2) Opens in response to output When the control device 100 acquires the circuit breaker signal (OFF) at time T1, the control device 100 opens the intake air release valve 3a in response to the output measured by the output sensor 14. 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 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, with reference to FIG. 7, the control of the intake air release valve 3a and the exhaust bypass valve 4a of this embodiment will be described. FIG. 7 is a flowchart showing 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 the target boost pressure calculated from a map of Pme and boost pressure (step S1). This control is continued while the turbocharger 5 is in operation. Next, the control device 100 determines whether there is a drop in the system 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 fixed opening, (2) open the intake air release valve 3a at an opening corresponding to the rotational speed of the engine 6, (3) open the intake air release valve 3a at an opening corresponding to the output of the engine 6, or (4) open the intake air release valve 3a at an opening corresponding to the rotational speed and output of the engine 6. The control device 100 may also close the intake air release valve 3a after a certain time has elapsed since opening the intake air release valve 3a, or may close the intake air release valve 3a after a drop in the system frequency or fluctuations in the 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 onward 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] (effect) According to the first embodiment, when the rotation speed of the engine 6 decreases due to a change 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. Furthermore, 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. Furthermore, 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 just 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 showing 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 "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 burned 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 not shown in 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 rejection 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 the output of the engine 6 to overshoot. Therefore, in the second embodiment, the intake air release valve 3a is opened during load rejection to release the mixed gas, thereby suppressing the overshoot.

[0024] (Control during load shedding) With reference to FIG. 9, the control when switching to islanded operation by disconnecting from the grid 20 (load rejection) will be described. Graph 91 in FIG. 9 shows the transition of the required power generation amount. Graph 92 shows the transition of the opening degree of the exhaust bypass valve 4a. Graph 93 shows the transition of 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′ also 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 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 93 shows this control. (2) Opens in response to output When the control device 100′ acquires the circuit breaker signal (OFF) at time T1, the control device 100′ opens the intake air release valve 3a in response 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, or may close the intake air release valve 3a after the exhaust bypass valve 4a is fully opened. This control can be applied during load rejection or emergency shutdown. Furthermore, 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, with reference to FIG. 10, the control of the intake air release valve 3a and the exhaust bypass valve 4a of this embodiment will be described. FIG. 10 is a flowchart showing 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 the target boost pressure calculated from a map of Pme and boost pressure (Step S11). This control is continued 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 fixed opening, or (2) open the intake air release valve 3a at an opening corresponding to the output of the engine 6. Furthermore, when a certain time has elapsed since the load dump 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 due to load shedding or the like.

[0027] FIG. 11 is a schematic block diagram showing the configuration of a computer according to the embodiment. The computer 900 includes a CPU 901, a main memory device 902, an auxiliary memory 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 memory device 903 in the form of a program. The CPU 901 reads the program from the auxiliary memory device 903, loads it into the main memory device 902, and executes the above-described processing in accordance with the program. The CPU 901 allocates a storage area in the main memory device 902 in accordance with the program. The CPU 901 allocates a storage area in the auxiliary memory device 903 for storing data being processed in accordance with the program.

[0028] In another embodiment, the computer 900 may include a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device) in addition to or instead of the above configuration. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Array). 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. Furthermore, if a WWW system is used, the term "computer system" also includes a homepage provision environment (or display environment). Furthermore, 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. Furthermore, if the program is distributed to the computer 900 via a communication line, the computer 900 that receives the program may load the program into the main storage device 902 and execute the above-described processing. Furthermore, the program may be for implementing part of the above-described functions, or may be capable of implementing the above-described functions 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 off 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, and includes: 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. This makes it possible to avoid surging and output overshoot that occur when the engine speed drops.

[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 the boost pressure from the turbocharger to the engine, and controls the exhaust bypass valve so as to achieve the calculated boost pressure. This allows the engine to be operated efficiently.

[0034] (3) A control device according to a third aspect is a control device according to (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 the engine speed occurs. This makes it possible to avoid surging and output overshoot that occur when the engine speed drops.

[0035] (4) A control device according to a fourth aspect is a control device according to (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 the engine speed occurs. This makes it possible to avoid surging and output overshoot that occur when the engine speed drops.

[0036] (5) A control device according to a fifth aspect is a control device according to any one of (1) to (4), in which the engine speed decreases 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. This makes it possible to predict and estimate a 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. [Explanation of symbols]

[0039] 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 pipe, 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 air release valve provided in an intake air release pipe branched from an intake air 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 discharged by the engine, a means for controlling an opening degree of the exhaust bypass valve based on a target intake pressure of air or a mixed gas obtained by mixing fuel and air and supplied from the turbocharger to the engine; means for opening the intake air release valve when a drop in engine speed occurs; A control device comprising:

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

3. The means for opening the air supply release valve comprises: When a decrease in the engine speed occurs, the intake air release valve is opened at a constant opening. The control device according to claim 1 or 2.

4. The means for opening the air supply release valve comprises: When a decrease in the engine speed occurs, the intake air release valve is opened at an opening degree corresponding to the engine speed and / or the engine output. The control device according to claim 1 or 2.

5. The case where the engine speed decreases is one of the cases where the frequency of the power grid to which the generator that generates electricity by driving the engine is connected decreases, where a load rejection occurs, and where a load is added. The control device according to claim 1 or 2.

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

7. A control method for controlling an intake air release valve provided in an intake air release pipe branched from an intake air 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 discharged by the engine, the method comprising: controlling an opening degree of the exhaust bypass valve based on a target intake pressure of air or a mixed gas obtained by mixing fuel and air, which is supplied from the turbocharger to the engine; opening the intake air release valve when a drop in engine speed occurs; Control method.

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