JP5022823B2 - Gas engine control device - Google Patents

Description

  The present invention relates to a control device for a pilot ignition type premixed lean combustion engine.

  A so-called cogeneration system that generates electric power by driving a generator with a gas engine and generates hot water, steam, or the like by using exhaust heat of the gas engine is becoming widespread. The gas engine is supplied with a mixed gas in which fuel gas and air are mixed in advance at an air-fuel ratio (for example, fuel: air = 1: 20) lower than the stoichiometric air-fuel ratio (fuel: air = 1: 15), A pilot ignition type premixed lean combustion engine may be used in which this is burned by a pilot ignition type. Since such an engine is driven with a fuel gas less than the stoichiometric air-fuel ratio, there is an advantage that fuel efficiency is good. Patent Document 1 is exemplified as an air-fuel ratio control technique for a lean combustion engine.

In general, engine output control is performed by adjusting the opening degree of a fuel gas supply throttle by a governor controller. In the cogeneration system, the power control device generates a control signal according to the target value of the generator output, and the governor controller executes the opening degree adjustment according to the control signal.
JP-A-5-39737

  By the way, in an engine in which a mixed gas close to the stoichiometric air-fuel ratio is used, PID control is usually adopted as a control method of the governor controller in order to efficiently bring the engine output close to the target value. That is, when the deviation between the current output value and the target value is large, the control signal is expanded so that the pulse width of the control signal is widened to approach the target value quickly, and when the deviation is small, the pulse width is reduced to converge to the target value. Done.

  However, if such PID control is applied to a pilot ignition type premixed lean combustion engine, the output control may not be performed well. In other words, even if the throttle opening is adjusted by the governor controller in the engine, the responsiveness is poor, and even if a control pulse having a pulse width corresponding to the deviation between the output value and the target value is given by PID control, it responds to this. There was a problem that the output control performed could not be performed sufficiently. For this reason, in the cogeneration system, when the governor controller is directly controlled by a command from the power control device, problems such as engine stall may occur.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a gas engine control device capable of efficiently performing output control of a pilot ignition type premixed lean combustion engine.

Gas engine control apparatus according to claim 1 of the present invention is a device for controlling the premixed lean burn engine of pilot ignition system for use in a gas cogeneration system, gas supplies premixed fuel gas to the engine A gas flow control valve provided in the flow path, a control valve controller for adjusting the opening of the gas flow control valve, a sequencer for outputting a control signal for causing the control valve controller to perform an opening adjustment operation, An output control device that gives an operation command for canceling the deviation to the sequencer when a deviation occurs between a direct or indirect output value of the engine and a predetermined target value, and the output control device Are the increase command to bring the current output value lower than the target value closer to the target value and the current output value higher than the target value as the operation command. The sequencer can provide a lowering command that approaches a value to the sequencer, the sequencer outputs a pulse signal having a constant width as the control signal, and the control valve controller performs the opening adjustment operation at the time of the pulse width. The sequencer outputs the pulse signal at a first interval when the increase command is given from the output control device, and outputs the first signal when the decrease command is given. The pulse signal is output at a second interval shorter than the interval.

  According to this configuration, the control valve controller performs the opening adjustment operation of the gas flow control valve based on the pulse signal having a constant width output from the sequencer at the first interval. Therefore, the opening of the gas flow rate control valve does not suddenly increase, and even if the fuel gas is diluted more than the stoichiometric air-fuel ratio, the fuel concentration in the engine does not change abruptly. In other words, when the increase command is given, the in-cylinder pressure of the engine increases, so that an environment in which a stall (misfire) is likely to occur is generated. However, since the opening of the gas flow control valve is increased at a constant pace, It becomes difficult to occur.

  On the other hand, when the lowering command is given, a pulse signal is given to the control valve controller at a second interval shorter than the first interval. This is because the in-cylinder pressure of the engine is lowered when the lowering command is issued, so that misfire is not likely to occur, and the opening of the gas flow control valve can be reduced at a faster pace than when the raising command is issued. Thereby, the arrival time to the target value in the case of the lowering command can be shortened.

  In the above configuration, it is preferable that the generator further includes a generator driven by the engine, and the output control device generates the increase command or the decrease command based on an output state of the generator. . According to this configuration, output control of the engine is performed according to the output of the generator (for example, output voltage or generated power). For this reason, it becomes easy to apply this invention to a cogeneration system etc.

  In the above configuration, it is desirable that the sequencer outputs the pulse width of the pulse signal as a pulse width shorter than the fixed width at a timing immediately before reaching the target value. According to this configuration, the pulse signal given to the control valve controller immediately before reaching the target value has a short pulse width. Therefore, occurrence of overshoot or the like can be suppressed.

According to the gas engine control device of the present invention, the output control of the pilot ignition type premixed lean combustion engine used in the gas cogeneration system can be efficiently performed without causing misfire. In addition, by incorporating a sequencer, there is also an advantage that output control of a premixed lean combustion engine can be performed while diverting an existing PID control device.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram schematically showing the configuration of a cogeneration apparatus S to which the present invention is applied. The cogeneration apparatus S includes a pilot ignition type premixed lean combustion type gas engine system 10 and a gas engine control apparatus 20 that controls the operation of the gas engine system 10.

  The gas engine system 10 includes a gas engine 11, a generator 12, first and second heat exchangers 131 and 132, a fuel gas source 141, an air source 142, a carburetor 15, a gas throttle 16, a pilot oil source 171, and an oil control valve. 172 and the cooling water supply source 18 are comprised.

  The gas engine 11 is a pilot ignition type multi-cylinder gas engine that employs a common rail injection device 111. That is, the gas engine 11 is provided with a sub chamber, receives supply of a mixed gas in which fuel gas and air are mixed in advance at an air fuel ratio (for example, fuel: air = 1: 20 or so) lower than the stoichiometric air fuel ratio, and A method of stably igniting a lean air-fuel mixture by injecting a small amount of liquid fuel (pilot oil) into the room is employed.

  The common rail injection device 111 includes a common rail pipe, an electronic injection valve, and the like, accumulates the pilot oil compressed by a high-pressure pump in the common rail pipe, and injects the pilot oil into the sub chamber via the electronic injection valve. By adopting such a common rail injection device 111, optimal control of the injection amount and injection timing becomes possible for each individual cylinder. For this control, the common rail injection device 111 is provided with a pressure sensor 112.

  The gas engine 11 is provided with a first exhaust gas conduit 113 and a second exhaust gas conduit 114 for discharging combustion exhaust gas of fuel gas. These first and second exhaust gas pipes 113 and 114 are piped through the first and second heat exchangers 131 and 132, respectively, in order to recover the heat of the exhaust gas. Water is supplied to the first and second heat exchangers 131 and 132, and hot water is generated by exchanging heat between the water and the exhaust gas. Note that the temperature of the exhaust gas flowing through the first and second exhaust gas conduits 113 and 114 is monitored by a temperature sensor 115 for controlling the carburetor 15.

  The generator 12 is driven by the gas engine 11 to generate electric power, and supplies this electric power to a predetermined electric power system. The generator 12 includes a turbine, and the rotating shaft of the turbine is connected to the output rotating shaft of the gas engine 11. The generator 12 includes an exciter 121 that supplies a field current to a rotor coil mounted on the turbine.

  The fuel gas source 141 supplies fuel gas burned in the cylinder of the gas engine 11. The air source 142 supplies air to generate a mixed gas diluted to a predetermined air-fuel ratio. The carburetor 15 receives the supply of fuel gas and air from the fuel gas source 141 and the air source 142, adjusts the mixing ratio of both, and generates a mixed gas (premixed diluted gas). The carburetor 15 is controlled by a carburetor controller 25 described later, and the air-fuel ratio of the mixed gas can be adjusted.

  The gas throttle 16 (gas flow rate control valve) is installed in a gas flow path for supplying premixed fuel gas to the gas engine 11. The opening degree of the gas throttle 16 is adjusted by a governor controller 23 described later in order to adjust the rotational speed of the gas engine 11 in accordance with the load, and the supply amount of the premixed fuel gas to the gas engine 11 is controlled. The

The pilot oil source 171 supplies pilot oil supplied to the sub chamber of the gas engine 11 for pilot ignition. The oil control valve 172 is a control valve that controls the amount of pilot oil supplied to the gas engine 11. The oil control valve 172 is controlled by a pilot oil controller 173 based on the pressure of the common rail injection device 111 detected by the pressure sensor 112. The cooling water supply source 18 supplies cooling water used for cooling the gas engine 11.

  Next, the gas engine control device 20 includes a power control device 21 (output control device), a sequencer 22, a governor controller 23 (control valve controller), for operation control of the gas engine system 10 having the above-described configuration. An automatic voltage regulator (AVR) 24 and a carburetor controller 25 are provided.

  The power control device 21 controls the generated voltage and frequency of the generator 12, and causes the sequencer 22 to cancel the deviation when a deviation occurs between the output value of the generator 12 and a predetermined target value. Give a directive. Specifically, the 1st detection means 31 which detects the system voltage and frequency of the electric power system 30 to which the output terminal of the generator 12 is connected, and the 2nd detection means 32 which detects the output voltage and frequency of the generator 12 are detected. Based on the measured value, the power control device 21 outputs a control signal for controlling the generated voltage and frequency of the generator 12 to the automatic voltage adjusting device 24 and a control signal for controlling the output of the gas engine 11 to the carburetor controller 25. Output. Furthermore, when the output target value of the generator 12 is given, an increase command is given if the current output value is lower than the output target value, and a decrease command is given if the current output value is higher than the output target value. This is given to the sequencer 22.

  The sequencer 22 outputs a control signal for causing the governor controller 23 to perform the opening adjustment operation of the gas throttle 16. When an operation command is given from the power control device 21, the sequencer 22 generates a constant pulse including a pulse signal having a constant width and outputs the constant pulse to the governor controller 23 as the control signal.

  The governor controller 23 performs an operation of adjusting the opening of the gas throttle 16 in order to adjust the rotational speed of the gas engine 11 according to the load. The governor controller 23 performs the opening adjustment operation of the gas throttle 16 during the time of the pulse width of the pulse signal given from the sequencer 22. In this opening adjustment operation, when the output of the gas engine 11 is stabilized to a certain fixed value, or when the output of the gas engine 11 is increased to a certain target value (load UP), the output of the gas engine 11 is set to a certain target value. This is executed when the load is lowered (load DOWN).

Automatic voltage regulator 24 is a device for adjusting the supply field current to the rotor coil of the generator 12 from the exciter 121. That is, the automatic voltage regulator 24 controls the field current according to the value and frequency of the system voltage and the generator output voltage detected by the first and second detection means 31 and 32, thereby generating the generator output voltage and power. It is what controls the rate.

  The carburetor controller 25 controls the carburetor 15 to adjust the air-fuel ratio of the mixed gas in order to control the output of the generator.

  FIG. 2 is a block diagram illustrating functional configurations of the power control device 21 and the sequencer 22 described above. The power control device 21 functionally includes an output monitoring unit 211, a synchronization verification unit 212, and a generator output control unit 213. The sequencer 22 includes a pulse width setting unit 221 and an interval setting unit 222.

  The output monitoring unit 211 receives detection signals from the first detection unit 31 and the second detection unit 32 at a predetermined sampling period, receives information on the system voltage and frequency of the power system 30, and the output voltage (power generation) of the generator 12. Machine voltage) and frequency information.

  The synchronization verification unit 212 checks the phase difference between the system voltage and the generator voltage acquired by the output monitoring unit 211, and verifies the synchronization state of both. A signal relating to this synchronization state is given to the automatic voltage regulator 24. The automatic voltage regulator 24 generates a field current control signal corresponding to the phase difference between the system voltage and the generator voltage, and supplies this to the exciter 121. Thereby, the synchronization between the system voltage and the generator voltage is maintained.

  The generator output control unit 213 compares the actual generator voltage obtained at the present time based on the information acquired by the output monitoring unit 211 with the generator voltage given as the output target value, and It is determined whether there is a deviation for operating the sequencer 22. When the deviation exceeds a predetermined threshold, if the current output value is lower than the output target value, the “increase command” is used. If the current output value is higher than the output target value, “decrease” is performed. “Command” is given to the sequencer 22 as an operation command. The generator output control unit 213 also provides the generator output information to the carburetor controller 25.

  The pulse width setting unit 221 sets the pulse width of the pulse signal given to the governor controller 23. Unlike the interval described later, the pulse width is basically set to a constant width in both the “raising command” and the “lowering command”. However, the pulse width setting unit 221 sets the pulse width of the pulse signal to a pulse width shorter than the predetermined width at the timing immediately before reaching the target value. This is to prevent the output from rising (or dropping) too much and to suppress overshoot and the like.

  The interval setting unit 222 sets an interval of pulse signals to be given to the governor controller 23. The interval setting unit 222 sets a first interval of a predetermined time as the generation interval of the pulse signal when the “up command” is given from the generator output control unit 213. On the other hand, when the “decrease command” is given, the pulse signal generation interval is set to a second interval shorter than the first interval by a predetermined time.

  A specific example of the pulse signal will be illustrated. The pulse width can be selected from a range of about 0.1 to 10 seconds, for example. Note that the pulse width at the timing immediately before reaching the target value may be set to about 0.1 sec, for example. Further, the first interval at the time of “up command” can be selected from a range of about 2 to 20 seconds, for example. On the other hand, the second interval at the time of “decrease command” can be selected from a range of about 1 to 10 seconds, for example.

  The governor controller 23 adjusts the opening of the gas throttle 16 based on such a pulse signal. That is, the opening adjustment operation of the gas throttle 16 is executed during the time of the pulse width of the pulse signal. When the “up command” is given, instead of the PID signal as in the prior art, the pulse signal of the first interval having a constant width and a relatively long time is given to the governor controller 23, so that the opening of the gas throttle 16 increases rapidly. The fuel concentration in the gas engine 11 does not change abruptly even if the fuel gas is previously diluted. Accordingly, in the case of the “increase command”, the in-cylinder pressure of the engine increases, so that it becomes an environment where a stall (misfire) is likely to occur. However, the opening of the gas throttle 16 is increased at a certain relatively long first interval. Misfires are less likely to occur.

  On the other hand, in the case of a “lowering command”, a pulse signal is given to the governor controller 23 at a second interval shorter than the first interval. This is because the in-cylinder pressure of the gas engine 11 decreases when the “down command” is issued, so that misfire does not easily occur, and the opening of the gas throttle 16 can be reduced at a faster pace than when the “up command”. Thereby, the arrival time to the target value in the case of the “decrease command” can be shortened.

  Here, the difference between general PID control and constant pulse control according to the embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a block diagram schematically showing a gas engine control device employing the PID control method. In this case, the power control device 21 'gives a PID control signal to the governor controller 23', and the opening degree of the gas throttle 16 is adjusted based on the PID control signal.

  FIG. 4 is a chart showing an example of a PID control signal given to the governor controller 23 ′ based on PID control. Here, the PID control signal in the case of the “raising command” is illustrated. This PID control signal is also a pulse signal, but the duty ratio is changed according to the current deviation from the target value.

  As shown in FIG. 4, when the target value is assumed to be 100% load, if the current output value of the generator 12 is in the range of 0% to 50% load, the deviation is large, so the pulse signal is assigned to one cycle. It is turned on only for the period of time t11 that occupies most of the time, and is turned off for the remaining time t12. During this period t11, the governor controller 23 'performs an operation of raising the governor, that is, an operation of opening the gas throttle 16. This is because the target value is quickly approached. Hereinafter, when the load is in the range of 50% to 75%, the power is turned on only for a period t21 shorter than the time t11 and the remaining time t22 is turned off. Further, when the load is in the range of 75% to 100%, the power is turned on only for a period t31 shorter than the time t21 and the remaining time t32 is turned off.

  Such PID control is an effective control method for an engine having excellent responsiveness. However, in the case of an engine using a mixed gas having a low fuel gas concentration as an energy source, such as the premixed lean combustion type gas engine 11 targeted by the present embodiment, Responsiveness is poor and PID control often fails. In other words, even if the duty ratio is finely adjusted in accordance with the deviation, such a response cannot be obtained, and the desired control cannot be realized in many cases. In addition, by giving a pulse signal with a long ON period at the time of “raising command” having a large deviation, misfire may occur due to a response delay of the engine.

  In view of such a problem, in the present embodiment, control with a constant pulse is performed. FIG. 5 is a block diagram schematically showing a gas engine control device that employs the constant pulse control system of the present embodiment. As described above, according to the present embodiment, the power control device 21 gives an operation command to the sequencer 22 when there is a deviation from the target value, and the sequencer 22 receives the command to the governor controller 23 with a constant pulse width. Gives the control signal. Then, the opening degree of the gas throttle 16 is adjusted based on such a constant pulse control signal.

  FIG. 6 is a chart showing an example of control signals given to the sequencer 22 and the governor controller 23 based on constant pulse control. Here, the control signal in the case of the “raising command” is illustrated. As in FIG. 4, when the target value is 100% load, if there is a deviation from the target value, the power control device 21 generates an operation signal for the sequencer 22. This sequencer operation signal is turned OFF when the deviation is eliminated. If the parameter is changed so that the PID control signal output of the power control device 21 ′ of FIG. 3 is turned ON when there is a deviation, the existing PID control power control device can be used in this embodiment. It can be used as the power control device 21.

The control signal output from the sequencer 22 to the governor controller 23 is a pulse signal having a constant duty ratio regardless of the magnitude of deviation from the target value. That is, the output value of the generator 12 the current 0% to 50% load, 50% to 75% load, in any of the 75% to 100% load may, ON time ₌ t a, at OFF time = _{t b} is constant is there. However, only the timing of the pulse width just before reaching the target value, in order to prevent such overshoot, ON time is shorter t _end than t _a. It should be noted that, in the case of "lowering Directive", the time of t _b is shortened.

  According to such constant pulse control, the premixed lean combustion gas engine 11 is driven by a fuel gas smaller than the stoichiometric air-fuel ratio and tends to show a slow response to the opening adjustment of the gas throttle 16. A suitable load transfer control can be realized. Moreover, even if it takes a little time to reach the target value compared to the case where PID control can be applied, the opening degree of the gas throttle 16 does not change abruptly. There is also an advantage that it does not easily occur.

  The operation of the gas engine control device 20 described above will be described based on the flowchart shown in FIG. When the operation of the gas engine 11 is started, the output monitoring unit 211 of the power control device 21 receives information on the system voltage and frequency, the generator from the first detection unit 31 and the second detection unit 32 at a predetermined sampling period. Information on voltage and frequency is acquired (step S1). And the generator output control part 213 calculates | requires the actual generator output in the present time (step S2).

  Subsequently, the generator output control unit 213 compares the current generator output and the current output target value, and determines whether or not there is a deviation exceeding a predetermined threshold value between the two (step) S3). When there is substantially no deviation (NO in step S3), the process returns to step S1 and the operation of the gas engine 11 is continued as it is. On the other hand, if there is a deviation (YES in step S3), the generator output control unit 213 gives the sequencer 22 an operation command with an “up command” or “down command” (step S4).

  The sequencer 22 determines whether the operation command is an “up command” or a “down command” (step S5), and in the case of the “up command”, the interval setting unit 222 has a predetermined time set in advance. A pulse signal generation interval is set as the first interval (step S6). On the other hand, in the case of the “decrease command”, the interval setting unit 222 sets the pulse signal generation interval to a second interval that is shorter than the first interval by a predetermined time (step S7). The pulse width is set to a constant width by the pulse width setting unit 221 regardless of the “up command” and the “down command”.

  The constant pulse signal set in this way is given from the sequencer 22 to the governor controller 23 (step S8). Thereby, the opening adjustment operation of the gas throttle 16 is executed. Thereafter, the generator output control unit 213 monitors the degree of reaching the target value based on the voltage information acquired by the output monitoring unit 211. At this time, it is determined whether it is the timing immediately before reaching the target value (step S9).

  If it is not immediately before the target value (NO in step S9), the process returns to step S8 and the process is repeated. On the other hand, if it is immediately before the target value (YES in step S9), the pulse width setting unit 221 sets the pulse width to a width shorter than the pulse width of the constant pulse signal (for example, the minimum pulse width that can be set). (Step S10). Thereafter, an operation stop command is given from the generator output control unit 213 to the sequencer 22, and the deviation elimination operation is completed.

  As described above, in order to express the present invention, the present invention has been described appropriately and sufficiently through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Accordingly, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not limited to the scope of the claims. To be construed as inclusive.

  For example, in the above embodiment, an example is shown in which control is performed based on an output value that is indirect to the gas engine 11, which is a generator output, but the output of the gas engine 11 itself is monitored to perform constant pulse control. May be. Further, the gas throttle 16 is exemplified as the gas flow rate control valve and the governor controller 23 is exemplified as the control valve controller. However, these are only examples, and may be replaced with other things that perform the same operation.

It is a block diagram which shows roughly the structure of the cogeneration apparatus S to which this invention was applied. It is a block diagram which shows the function structure of an electric power control apparatus and a sequencer. It is a block diagram which shows simply the gas engine control apparatus by which the PID control system was employ | adopted. It is a chart which shows the example of the PID control signal given to a governor controller based on PID control. It is a block diagram which shows simply the gas engine control apparatus by which the constant pulse control system of this embodiment was employ | adopted. It is a chart which shows the example of the control signal given to a governor controller based on constant pulse control. It is a flowchart which shows operation | movement of a gas engine control apparatus.

Explanation of symbols

10 Gas Engine System 11 Gas Engine (Premixed Lean Combustion Gas Engine)
12 generator 121 exciter 131 heat exchanger 141 fuel gas source 142 air source 15 carburetor 16 gas throttle (gas flow control valve)
171 Pilot oil source 18 Cooling water supply source 20 Gas engine control device 21 Power control device (output control device)
211 Output Monitoring Unit 212 Synchronization Verification Unit 213 Generator Output Control Unit 22 Sequencer 221 Pulse Width Setting Unit 222 Interval Setting Unit 23 Governor Controller (Control Valve Controller)
24 automatic voltage regulator 25 carburetor controller 30 power system

Claims (3)

An apparatus for controlling a pilot ignition type premixed lean combustion engine used in a gas cogeneration system ,
A gas flow rate control valve provided in a gas flow path for supplying premixed fuel gas to the engine;
A control valve controller for adjusting the opening of the gas flow control valve;
A sequencer that outputs a control signal for causing the control valve controller to perform an opening adjustment operation;
An output control device that provides an operation command for canceling the deviation to the sequencer when a deviation occurs between a direct or indirect output value of the engine and a predetermined target value;
The output control device sends, as the operation command, an instruction to raise the current output value lower than the target value to the target value, and a command to lower the current output value higher than the target value to the target value. It is possible to give
The sequencer outputs a pulse signal having a constant width as the control signal, and the control valve controller executes the opening adjustment operation in the time of the pulse width,
The sequencer outputs the pulse signal at a first interval when the raising command is given from the output control device, and a second interval shorter than the first interval when the lowering command is given. To output the pulse signal,
A gas engine control device. Further comprising a generator driven by the engine;
The gas engine control device according to claim 1, wherein the output control device generates the increase command or the decrease command based on an output state of the generator.   2. The gas engine control device according to claim 1, wherein the sequencer outputs a pulse width of a pulse signal as a pulse width shorter than the fixed width at a timing immediately before reaching the target value.

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