Control device, power generation system and control method

Abstract

Provides turbocharger control in response to a drop in engine speed. [Solution] The control device controls an intake air release valve provided in an intake air release pipe branching 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, and is equipped with a means for controlling the exhaust bypass valve based on a target intake air pressure of air or a mixed gas of fuel and air supplied from the turbocharger to the engine, and a means for opening the intake air release valve when a drop in engine speed occurs.

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 burned together with fuel in the combustion chamber is supplied to the turbocharger through an exhaust pipe and then discharged outside the system. In a high-power diesel engine or a premixed gas engine, an intake air discharge pipe that discharges part 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 are provided, and the amount of air flowing through these pipes is controlled to achieve highly efficient operation. For example, Patent Document 1 discloses a control that achieves an intake air pressure according to the operating conditions of the engine 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, power generation equipment connected to the grid is expected to play a role in maintaining the grid. When the voltage and frequency of the grid fluctuate, various effects occur on the power generation equipment connected to the grid. For example, when the grid frequency drops, the rotation speed of the engine generator connected to the grid drops. When the rotation speed of the engine generator drops, the operating point of the turbocharger that supplies compressed air to the engine generator shifts to the small wind force side, and the probability of surging increases. In addition, in the case of a premixed gas engine with intake before the turbocharger, the volume from the mixer that mixes fuel and air to the combustion chamber is large, and when a load shedding occurs, the premixed gas present in the piping from the mixer to the combustion chamber may be supplied to the combustion chamber, causing an overshoot. When the engine rotation speed drops due to a drop in the grid frequency or load shedding, various problems may occur on the turbocharger side. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-240585 A Summary of the Invention [Problem to be solved by the invention]

[0005] It is necessary to control the turbocharger in response to the drop 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 branched off from the middle of 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, and controls the exhaust bypass valve based on a target intake air pressure of air or a mixed gas of fuel and air to be supplied from the turbocharger to the engine. Valve and a means for controlling said intake air release valve when a reduction in engine speed occurs. Take Control and a means for detecting the presence of the The means for controlling the exhaust bypass valve controls 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, and while controlling the opening degree of the exhaust bypass valve, When the engine speed drops, the intake air release valve Take Control means for opening said intake air release valve; When the means for controlling the air release valve opens the air release valve, the means for controlling the opening degree of the exhaust bypass valve controls the opening degree of the exhaust bypass valve so as to ensure the target intake pressure; While the means for controlling the exhaust bypass valve controls the opening degree of the exhaust bypass valve so as to ensure the target intake pressure, When a predetermined condition is met, the intake air release valve is Take Control The means closes the intake air release valve. In the same manner, a case where a drop in the engine speed occurs refers to a case where a frequency of an electric power system to which a generator that generates electricity by driving the engine is connected drops, a load shedding occurs, or a load addition occurs, and the means for controlling the exhaust bypass valve reduces the opening of the exhaust bypass valve so that the target supply pressure can be ensured when the frequency of the electric power system drops or when the load addition occurs, and increases the opening of the exhaust bypass valve so that the target supply pressure can be ensured when the load shedding occurs, and the predetermined condition is satisfied when a certain time has elapsed since the intake air release valve was opened, or when a drop in the frequency of the electric power system or a fluctuation in the required power output of the generator has stabilized.

[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 connecting the turbocharger to the engine, an air intake discharge pipe branching off from the air intake pipe, an air intake discharge valve provided in the air intake discharge pipe, an exhaust bypass pipe that bypasses the turbocharger and discharges exhaust gas emitted by the engine, an exhaust bypass valve provided in the exhaust bypass pipe, and the above-mentioned control device.

[0009] 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 branched off 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 control method comprising the steps of: controlling an opening degree of the exhaust bypass valve based on a target intake air pressure of air or a mixed gas of fuel and air to be supplied from the turbocharger to the engine; While controlling the opening degree of the exhaust bypass valve The engine speed drops and, Open the air supply release valve, When the air supply release valve is opened, controlling an opening degree of the exhaust bypass valve so as to ensure the target intake pressure; While controlling the opening of the exhaust bypass valve so as to ensure the target intake pressure, When a predetermined condition is met, the intake air release valve is closed. In the same manner, a case where a drop in the engine speed occurs refers to a case where a frequency of an electric power system to which a generator that generates electricity by driving the engine is connected drops, a load shedding occurs, or a load introduction occurs. When controlling the aperture of the exhaust bypass valve so as to ensure the target supply pressure, if the frequency of the electric power system drops or if the load introduction occurs, the aperture of the exhaust bypass valve is reduced so as to ensure the target supply pressure, and if the load shedding occurs, the aperture of the exhaust bypass valve is increased so as to ensure the target supply pressure. The predetermined condition is met when a certain time has elapsed since the supply air release valve was opened, or when a drop in the frequency of the electric power system or a fluctuation in the required power output of the generator stabilizes. Effect of the Invention

[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 engine speed that occurs when the system frequency drops or when load is rejected. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic diagram showing a configuration of a power generation system according to a first embodiment. [Diagram 2] 5 is a diagram illustrating a situation in which a decrease in engine speed occurs in the first embodiment. FIG. [Diagram 3] FIG. 4 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. [Diagram 5] FIG. 4 is a second diagram showing an example of control according to the first embodiment. [Figure 6] FIG. 11 is a third diagram showing an example of control according to the first embodiment. [Figure 7] 5 is a flowchart showing 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. 11 is a diagram illustrating an example of control according to the second embodiment. [Figure 10] 10 is a flowchart showing 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 PREFERRED EMBODIMENTS

[0012] First Embodiment Hereinafter, the power generation system 1 of the first embodiment and its control will be described with reference to the drawings. (Power generation system configuration) 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 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 and the engine 6, and 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 pressure and a temperature sensor 12 for measuring the intake temperature, and the values ​​measured by these sensors are transmitted to the control device 100. An intake air discharge pipe 3 that branches the air flow to the engine 6 is connected to the intake air pipe 2b, and a part of the air in the intake air pipe 2b can be discharged to the outside of the system through the intake air discharge pipe 3. The intake air discharge pipe 3 is provided with an intake air discharge valve 3a that adjusts the amount of air discharged. The opening degree of the intake air discharge valve 3a is controlled by the control device 100. The exhaust pipe 9b connects the engine 6 and 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, and the opening degree of the exhaust bypass valve 4a 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 in 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) in the power plant, and the generator 7 and the on-site equipment are switched between connected and disconnected by turning on (connected) and off (disconnected) the circuit breaker 16b. Circuit breaker signals indicating whether the circuit breakers 16a and 16b are in a connected state or disconnected state are 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 composed of 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, the control device 100 temporarily opens the intake air release valve 3a when a drop in the frequency of the system 20 (a drop in the rotation speed of the engine 6), a load shedding, or the like occurs, thereby 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. In addition, as shown in FIG. 2, the frequency f (the 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 to the small air volume side, the surging margin of the turbocharger 5 decreases, and the probability of surging occurring increases. FIG. 3 shows a schematic characteristic curve of the turbocharger 5. The vertical axis of the graph in FIG. 3 is the pressure ratio, and the horizontal axis is the flow rate of air supplied by the turbocharger 5. Line 30 represents the boundary between the operating region (left side of 30) where surging occurs in the turbocharger 5 and the operating region (right side of 30) where surging does not occur, and 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 changes from line 32 to line 31. Then, the distance to line 30 becomes shorter (i.e., the surging margin decreases), and the probability of surging occurring increases. In particular, in a premixed gas engine, when surging occurs, the mixed gas flows back into the intake chamber due to blowback, and in the next cycle, the blown back mixture and fuel gas are supplied into the combustion chamber, the excess air ratio decreases, and Pmi (mean effective pressure) increases. As a result, abnormal combustion such as pre-ignition and knocking occurs, which may damage the combustion chamber. In general, in order to ensure the surging margin of the turbocharger 5, the diffuser is narrowed. However, if an attempt is made to ensure the surging margin of the turbocharger 5 by installing a diffuser manufactured in this way, the efficiency of the turbocharger 5 decreases overall, including in a state where no frequency drop occurs during rated operation. The decrease in efficiency of the turbocharger 5 leads to a decrease in the thermal efficiency of the engine 6. Therefore, in this embodiment, in a state where the engine speed decreases, the intake air release valve 3a is temporarily opened to release air outside the system through the intake air release pipe 3, thereby gaining the surging margin, and in other situations, the intake air release valve 3a is closed to operate the turbocharger 5 with high efficiency. Line 33 in Fig. 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 the 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. In addition, 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 when frequency drops) Next, the control of the intake air release valve 3a and the exhaust bypass valve 4a when the frequency of the system 20 (the rotation speed of the engine 6) drops will be described with reference to FIG. 4. Graph 41 in FIG. 4 shows the transition of the system frequency. Graph 42 shows the transition of the opening degree of the exhaust bypass valve 4a. Graph 43 shows the transition of the opening degree of the intake air release valve 3a. The same position on the horizontal axis of the graphs 41 to 43 indicates the same time. The control device 100 controls the opening degree of the exhaust bypass valve 4a so that the pressure measured by the pressure sensor 11 always becomes the target intake air pressure calculated from a map of Pme (net mean effective pressure) and intake air pressure, regardless of the system frequency. For example, the control device 100 calculates Pme by substituting the rotation speed measured by the rotation speed sensor 13 and the output measured by the output sensor 14 into the formula for Pme, and calculates the target intake air pressure according to Pme using a map, table, function, or the like that specifies the relationship between Pme and the target intake air pressure. Then, the control device 100 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 according to the target air intake pressure, and controls the exhaust bypass valve 4a. A graph 42 shows the transition of the opening degree 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 value or when it detects that the rate of frequency drop is equal to or greater than the predetermined threshold value, it performs control to open the intake air release valve 3a in order to suppress surging. The following three examples will be described as methods for controlling the intake air release valve 3a. (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 becomes larger 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 and the output (or output range) of the engine 6 with 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 system frequency drops due to fluctuations in the renewable energy power source or the like, the surging margin is ensured by any one of the controls (1) to (3). On the other hand, since the amount of air supplied to the engine 6 side drops, the opening degree of the exhaust bypass valve 4a is reduced to ensure the intake 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 system 20 measured by the frequency sensor 15, and perform control to open the intake air release valve 3a described above when it detects that the rotation speed drops to a predetermined threshold value or that the rate of decrease in the rotation speed is equal to or greater than the predetermined threshold value. The control device 100 may also close the intake air release valve 3a after the drop in the system frequency stops, for example.

[0017] (Control when load is applied) Next, referring to FIG. 5, the control when a load is applied during islanding operation separated from the grid 20 and during transition from grid operation to islanding operation will be described. Graph 51 in FIG. 5 shows the transition of the required power generation amount. Graph 52 shows the transition of the opening degree of the exhaust bypass valve 4a. Graph 53 shows the transition of 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 the load is applied, 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 FIG. 4.

[0018] As described with reference to Fig. 2, a drop in frequency also occurs when a load is applied, and the surging margin decreases. When the control device 100 receives a signal from the circuit breaker 16b indicating that the circuit breaker 16b should be turned on, the control device 100 performs control to open the intake air release valve 3a in order to suppress surging. The following two examples will be described as methods for controlling the intake air release valve 3a. (1) Open at a constant 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 constant 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) Opens according to output. When the control device 100 acquires 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 holds a table in which the output of the engine 6 and the opening degree of the intake air release valve 3a correspond to each other (the lower the output, the larger the opening degree), and by referring to 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 the intake air release valve 3a 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 for load application is detected during isolated operation, the intake air release valve 3a is temporarily opened to ensure a surging margin. On the other hand, since the amount of air supplied to the engine 6 side decreases, the opening degree of the exhaust bypass valve is reduced to ensure the intake air pressure.

[0019] (Control during load reduction) Next, referring to FIG. 6, control in the case where a large load reduction occurs when the system is operated independently of the grid 20 or when the system shifts from grid operation to independent operation will be described. Graph 61 in FIG. 6 shows the transition of the required power generation amount. Graph 62 shows the transition of the opening degree of the exhaust bypass valve 4a. Graph 63 shows the transition of the opening degree 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 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 has been described with reference to FIG. 4.

[0020] As explained with reference to Fig. 2, a drop in frequency also occurs during load shedding, 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 performs control to open the intake air release valve 3a in order to suppress surging. The following two examples will be explained as a method of controlling the intake air release valve 3a. These controls are similar to those explained with reference to Fig. 5. (1) Open at a constant 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 constant 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) Opens in response to output When the control device 100 acquires a circuit breaker signal (OFF) at time T1, it 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 fixed 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 to provide a surging margin and avoid surging.

[0021] (operation) Next, control of the intake air release valve 3a and the exhaust bypass valve 4a of this embodiment will be described with reference to FIG. 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 judges 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 judges 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 signal 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 be temporarily opened (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 rotation 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 rotation 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 the system frequency or a fluctuation in the required power output becomes stable. 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 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 is continued. When the operation of the turbocharger 5 is to be stopped (step S4; Yes), the processing in 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 output such as a drop in the system frequency or a sudden load change, instead of opening the intake air release valve 3a to release the air to be supplied to the engine 6, the air flow rate supplied to the turbocharger 5 is maintained (or increased). This prevents the operating line of the turbocharger 5 from shifting to the small air volume side, and the surging margin of the turbocharger 5 from decreasing, thereby suppressing the occurrence of surging. In addition, by opening the intake air release valve 3a only in a situation where a drop in the rotation speed of the engine 6 is predicted or estimated, the turbocharger 5 can be operated without decreasing its operating efficiency in other situations. In addition, there is no need to modify the hardware, such as by installing a diffuser that is designed to deal with surging, in preparation for a drop in the system frequency, which rarely occurs, and the system can be easily introduced because it can deal with a drop in the engine rotation speed only by controlling the valve.

[0023] Second Embodiment Hereinafter, the power generation system 1' according to the second embodiment and its control will be described with reference to the drawings. FIG. 8 is a schematic diagram showing the configuration of the power generation system according to the second embodiment. FIG. 8 shows a schematic diagram of the power generation system 1' including a premixed gas engine with intake before the turbocharger. Unlike the gas engine shown in FIG. 1, a mixer 2c is provided in front of the compressor 5a, and 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 the intake pipe 2d. The mixed gas compressed by the compressor 5a is cooled by the cooler 10 and supplied to the combustion chamber 6a of the engine 6 through the intake pipe 2e. The exhaust gas burned by the engine 6 is collected in an exhaust collecting pipe 9c and supplied to the exhaust turbine 5b through the exhaust pipe 9b. The other configurations are the same as those described in FIG. 1. Also, sensors are not shown in FIG. 8. In the case of a premixed gas engine with intake before the turbocharger as 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 an overshoot in the output of the engine 6. Therefore, in the second embodiment, the intake air release valve 3a is opened at the time of load rejection to release the mixed gas, thereby suppressing the overshoot.

[0024] (Control during load shedding) With reference to FIG. 9, the control in the case of switching to an isolated operation by isolating 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 the graphs 91 to 93 indicates the same time. When the control device 100' acquires a circuit breaker signal indicating that the circuit breaker 16a or the circuit breaker 16b is turned off, the control device 100' performs control to suppress overshoot. When the control device 100' acquires 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). In addition, the control device 100' performs control to open the air supply release valve 3a. The following two types of examples will be described as a method of 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. 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 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 a circuit breaker signal (OFF) at time T1, it opens the intake air release valve 3a in response to the output measured by the output sensor 14. The control device 100' may, for example, close the intake air release valve 3a after opening it for a certain period of 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 at the time of load shedding or emergency stop. In addition, after performing the control described in FIG. 9, the operation may be continued and the system 20 may be reconnected.

[0025] (operation) Next, control of the intake air release valve 3a and the exhaust bypass valve 4a of this embodiment will be described with reference to FIG. 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' judges whether or not a load shedding has occurred (step S12). For example, the control device 100' judges whether or not a load shedding has occurred based on a circuit breaker signal issued by the circuit breaker 16a. If there is no load shedding (step S12; No), the process of step S1 is continued. If there is a load shedding (step S12; Yes), the control device 100' controls to open the intake air release valve 3a (step S13). For example, the control device 100' may (1) open the intake air release valve 3a at a constant opening degree, or (2) open the intake air release valve 3a at an opening degree according to the output of the engine 6. In addition, when a certain time has elapsed since the control device 100' detected the load shedding, the control device 100' fully opens the exhaust bypass valve 4a (step S14).

[0026] (effect) According to the second embodiment, it is possible to suppress overshooting of the output of the engine 6 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-mentioned control devices 100, 100' are implemented in the computer 900. The above-mentioned 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 in the main memory device 902, and executes the above-mentioned processing in accordance with the program. The CPU 901 secures a storage area in the main memory device 902 in accordance with the program. The CPU 901 secures 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 included as an example of a processor.

[0029] A program for realizing all or part of the functions of the control devices 100 and 100' may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read 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. In addition, if a WWW system is used, the term "computer system" also includes a homepage providing environment (or display environment). In addition, the term "computer-readable recording medium" refers to a portable medium such as a CD, DVD, or USB, or a storage device such as a hard disk built into a computer system. In addition, 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 processing. In addition, the above program may be for realizing part of the above-mentioned functions, or may be capable of realizing the above-mentioned functions in combination with a program already recorded 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 gist of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents as described in the claims, as well as in the scope and gist of the invention.

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

[0032] (1) A control device according to a first aspect is a control device that controls an intake air release valve provided in an intake air 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 discharged by the engine, and includes: a means for controlling an opening degree of the exhaust bypass valve based on a target intake air pressure of air or a mixed gas of fuel and air supplied from the turbocharger to the engine; and a means for opening the intake air 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 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 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 operate 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 degree when a drop in 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 of (1) to (2), wherein the means for opening the intake air release valve opens the intake air release valve to 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 of (1) to (4), in which a case where a decrease in the engine speed occurs is any one of a case where a frequency of a power grid to which a generator that generates electricity by driving the engine is connected decreases, a case where a load shedding occurs, and a case where 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 connecting the turbocharger and the engine, an air intake discharge pipe branching off from the air intake pipe, an air intake discharge valve provided in the air intake discharge pipe, an exhaust bypass pipe that bypasses the turbocharger and discharges exhaust gas emitted by the engine, an exhaust bypass valve provided in the exhaust bypass pipe, and the control device described in claim 1 or claim 2.

[0038] (7) A control method according to a seventh aspect is a control method for controlling an intake air release valve provided in an intake air release pipe branched off from the middle of 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 discharged by the engine, the control method controlling an opening degree of the exhaust bypass valve based on a target intake air pressure of air or a mixed gas of fuel and air supplied from the turbocharger to the engine, and opening the intake air release valve when a drop in engine speed occurs. [Explanation of symbols]

[0039] REFERENCE SIGNS LIST 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 for controlling an intake air release valve provided in an intake air release pipe branched off 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 the exhaust bypass valve based on a target boost pressure of air or a mixed gas obtained by mixing fuel and air, which is supplied from the turbocharger to the engine; means for controlling the intake air release valve when a drop in engine speed occurs; Equipped with the means for controlling the exhaust bypass valve controls 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, When a decrease in engine speed occurs while controlling the opening degree of the exhaust bypass valve, the means for controlling the intake air release valve opens the intake air release valve, when the means for controlling the intake air release valve opens the intake air release valve, the means for controlling the exhaust bypass valve controls an opening degree of the exhaust bypass valve so as to ensure the target intake air pressure; When a predetermined condition is satisfied while the exhaust bypass valve control means is controlling the opening degree of the exhaust bypass valve so as to ensure the target intake air pressure, the intake air release valve control means closes the intake air release valve, The case where the engine speed is reduced is any one of the cases where the frequency of a power grid to which a generator that generates electricity by driving the engine is connected is reduced, where a load rejection occurs, and where a load is added. the means for controlling the exhaust bypass valve reduces an opening degree of the exhaust bypass valve so as to ensure the target air supply pressure when the frequency of the power grid drops and when the load is introduced, and increases an opening degree of the exhaust bypass valve so as to ensure the target air supply pressure when the load is rejected; The predetermined condition being satisfied means that a certain time has elapsed since the air intake release valve was opened, or that a drop in the frequency of the power grid or a fluctuation in the required power output of the generator has stabilized. Control device.

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 a rotation speed of the engine and an 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 controlling the air intake release valve includes: When a decrease in engine speed occurs, the intake air release valve is opened at a constant opening degree. The control device according to claim 1 or 2.

4. The means for controlling the air intake release valve includes: when a decrease in 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. an engine, a generator driven by the engine, a turbocharger that supplies compressed air to the engine, an air intake pipe connecting the turbocharger and the engine, an air intake discharge pipe branching off from the air intake pipe, an air intake discharge valve provided in the air intake discharge pipe, an exhaust bypass pipe that bypasses the turbocharger and discharges exhaust gas discharged by the engine, 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:

6. A control method for controlling an intake air release valve provided in an intake air release pipe branched off 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 the steps of: 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; When the engine speed decreases while controlling the opening degree of the exhaust bypass valve, the intake air release valve is opened, when the intake air release valve is opened, an opening degree of the exhaust bypass valve is controlled so as to ensure the target intake air pressure; when a predetermined condition is satisfied while controlling the opening degree of the exhaust bypass valve so as to ensure the target intake pressure, the intake air release valve is closed; The case where the engine speed is reduced is any one of the cases where the frequency of a power grid to which a generator that generates electricity by driving the engine is connected is reduced, where a load rejection occurs, and where a load is added. when controlling the opening degree of the exhaust bypass valve so as to ensure the target air supply pressure, if the frequency of the power grid drops and if the load is introduced, the opening degree of the exhaust bypass valve is reduced so as to ensure the target air supply pressure, and if the load is cut off, the opening degree of the exhaust bypass valve is increased so as to ensure the target air supply pressure; The predetermined condition being satisfied means that a certain time has elapsed since the air intake release valve was opened, or that a drop in the frequency of the power grid or a fluctuation in the required power output of the generator has stabilized. Control methods.

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