JP4305949B2 - Method for switching control mode of gas turbine power generator - Google Patents

Description

  The present invention relates to a control mode switching method for a gas turbine power generator.

In a gas turbine power generator that rotates a generator with a gas turbine, isochronous control and rotational speed droop control are known as rotational speed control methods for controlling the rotational speed of the gas turbine.
FIG. 4A is a block diagram of isochronous control. Isochronous control is also referred to as integral control. The difference (deviation) between the control target value (N _gref ) and the actually controlled value (N _g ) is multiplied by the proportional gain K _p to _{obtain the} proportional control amount. This is a control that integrates the value multiplied by the integral gain _Ki (sometimes called the reset gain) and moves the actuator using the value obtained by adding the value and the proportional control amount as the control amount. Change. The control amount (integrated control fuel flow rate W _f ) by this isochronous control is expressed by equation (1) shown in the figure, and N _gref = N _g during complete integration control.
FIG. 4B is a block diagram of the rotational speed droop control. The rotational speed droop control is also called proportional control, and the control amount is obtained by multiplying the difference (deviation) between the control target value (N _gref ) and the actually controlled value (N _g ) by the proportional gain (K _p ). This is a control to calculate. The control amount (integrated control fuel flow rate Wf) by this rotational speed droop control is expressed by the equation (2) shown in the figure, and W _fss is selected so that N _gref = N _g during no load and rated rotational speed operation. Is done. For this reason, N _gref > N _g during load operation.

A gas turbine power generator is used for both an isolated operation separated from an electric power system of an electric power company and a system combined operation linked to the electric power system. During the single operation, isochronous control using the control target value (N _gref ) as a synchronous frequency is used so that the frequency of the generated power maintains a desired frequency.

On the other hand, rotation speed droop control is used during system entry operation. The reason for this is that when the generator is linked to a power company or another generator via a power line, the generator and the motor (the engine such as a gas turbine) that drives the generator are made of elastic material such as rubber. Can be considered to be combined. Then, by setting the control target value (N _gref ) of the prime mover to be, for example, about 4% higher than the synchronous frequency (N _g ), energy flows into the system from the gas turbine power generation device to be increased in speed. In this case, the actual rotational speed is the rotational speed (synchronous frequency) of the system. The higher the control target value (N _gref ), the higher the output. That is, it can be said that the rotational speed of the prime mover and the output power are in a substantially proportional relationship. Therefore, fluctuations in the rotational speed lead to fluctuations in output power.

  Note that Patent Documents 1 to 3 are disclosed as prior arts related to the present invention.

  The "gas turbine control device" of Patent Document 1 maintains a predetermined combustor inlet temperature even during idling or the like, and enables low NOx combustion. As shown in FIG. In a gas turbine in which variable guide vanes 52 and 53 are provided at the inlet of the power turbine 51 and a fuel pre-evaporation premixing chamber is provided at the inlet of the combustor 54, the accelerator opening detecting means 55 and the inlet of the combustor 54 are provided. The air temperature detection means 56, the target rotation speed calculation means 58 for calculating the target rotation speed of the gas generator shaft 57 from the accelerator opening, and the combustor 54 so that the rotation speed of the gas generator shaft 57 becomes the target rotation speed. The fuel control means 59 for controlling the fuel of the power turbine, and the power turbine inlet variable guide vane 53 are driven so as to keep the rotational speed of the power turbine 51 at a predetermined rotational speed when the accelerator opening is equal to or smaller than the set value. A rotation speed control unit 60 for Gosuru is intended to provide an inlet air temperature control means 61 for driving and controlling the compressor inlet variable guide vanes 52 so as to keep the inlet air temperature of the combustor 54 during this control to a predetermined temperature.

  Patent Document 2 discloses a gas turbine rotational speed control method and rotational speed control device that provides a rotational speed command for the output shaft rotational speed of a gas turbine even if a low-level selector and a high-level selector are provided in front of an integrator. As shown in FIG. 6, in the feedback control method for the rotational speed of the gas turbine comprising the low level selection means and the high level selection means, as shown in FIG. The rotation speed deviation is set to zero, and the second integration means 64 performs control according to the control request amount of the rotation speed control calculation result and other control calculation results.

  The “gas turbine generator control device” of Patent Document 3 is intended to reduce fuel consumption while suppressing the voltage waveform distortion rate, and sets a target engine speed Nset corresponding to the load L as shown in FIG. Target engine speed setting means 72 for controlling, engine speed control means 74 for feedback-controlling the fuel injection amount so that the engine speed N approaches the target engine speed Nset, and a target voltage for setting the target voltage waveform distortion rate Dset It comprises waveform distortion rate setting means 75 and target engine speed correction means 76 for correcting the target engine speed Nset in accordance with the set target voltage waveform distortion rate Dset.

JP-A-5-106469 JP-A-8-93503 Japanese Patent Laid-Open No. 10-8997

  The above-described control modes of isochronous control and rotational speed droop control need to be able to be switched in a short time as needed during operation of the gas turbine power generation device. At the time of this switching, in the case where the rotational speed control is performed, a control that does not change the generator rotational speed and the output power by changing the rotational speed target value is required.

However, conventionally, when switching from the rotational speed droop control mode (proportional control) to isochronous control (integral control), a method of appropriately selecting the initial value of integration as an anti-windup of integration was applied. At the time of switching, fluctuations in the rotational speed control fuel flow were caused, resulting in fluctuations in the rotational speed and fluctuations in output power.
The anti-windup is an operation for setting the initial value of integration so that the control amount does not change when switching from proportional control to integral control.

  In other words, conventionally, only the integration is initialized when the control mode is switched, so when switching from the integral control to the proportional control, switching is performed in a state where there is no deviation in the rotational speed. Since the required fuel flow rate is calculated due to the decrease in the rotation speed, the rotation speed fluctuates.

  The present invention has been developed to solve the above-described problems. That is, the object of the present invention is to switch the control mode of the isochronous control and the rotational speed droop control in a short time as needed during the operation of the gas turbine power generator, and to change the generator rotational speed and the output power. It is an object of the present invention to provide a control mode switching method for a gas turbine power generator capable of reducing the above.

According to the present invention, there is provided a control mode switching method for a gas turbine power generator,
(A) In switching from isochronous control to rotational speed droop control, the value obtained by subtracting the steady fuel flow W _fss from the current control fuel flow W _fref and dividing this by the proportional gain K _p is used as the rotational speed deviation after switching. Add to the current actual speed Ng,
(B) In switching from rotational speed droop control to isochronous control, the rotational speed target value _Ngref is maintained at the current actual rotational speed Ng, the steady fuel flow rate _Wfss is subtracted from the current control fuel flow rate _Wfref , and integration is performed. There is provided a control mode switching method for a gas turbine power generator characterized in that the initial value of a calculation unit is used.

  According to a preferred embodiment of the present invention, in (C) switching from isochronous control to output droop control, the integration control is continuously applied as it is, and the value obtained by dividing the current output power by the maximum power is multiplied by the speed addition rate. The value is the rotation speed deviation.

Further, according to the reference example , the rotation speed droop control target value calculation means calculates the rotation speed target value N _gref in the rotation speed droop control mode from the current fuel flow rate W _f , the steady fuel flow rate W _fss, and the current rotation speed Ng. And
The output droop control target value calculation means calculates the rotation speed target value N _gref in the output droop control mode from the current output power P and the rated rotation speed N,
According to the selected control mode, the rotation speed target value N _gref is selected by the rotation speed target value selection means,
Rotational speed target value integration means integrates the rotational speed target value based on the speed increase / decrease command for increasing / decreasing the rotational speed, and this integrated value is selected by the rotational speed target value selection means when the governor mode transitions. Initialized with
The deviation ΔN between the revolution target value N _gref and the current revolution Ng is calculated by the revolution deviation calculator.
An integral calculator multiplies the deviation ΔN between the rotational speed target value and the current rotational speed by a proportional gain, further multiplies that value by the integral gain Ki, adds the previous value and performs integration, and with an integral initialization pulse, There is provided a control mode switching method for a gas turbine power generator characterized by initializing an integrated value with a value which does not break a current state.

Furthermore, a proportional computing unit, the rotational speed target value and the present rotational speed deviation ΔN multiplied by a proportional gain Kp, and adds the constant fuel flow rate W _fss to that value, calculates a fuel flow W _fref in-loop control,
The fuel flow rate adder calculates the fuel flow rate W _fref for rotational speed control by adding the fuel flow rates from the proportional calculator and the integral calculator.

## The present invention makes it possible to avoid fluctuations by calculating an appropriate value in real time at the time of control mode switching and at the time of initializing the rotation speed and at the time of integration initialization.

That is, according to the above-described method of the present invention, when switching from isochronous to the rotational speed droop control mode, a _{value obtained} by subtracting the steady fuel flow rate (W _fss ) from the current fuel flow rate (W _fref ) is generated by the rotational speed deviation. Since it is the fuel flow rate, the value divided by the droop gain (K _p ) is the actually required rotational speed deviation.

  Further, in switching from the rotational speed droop to the isochronous control mode, the rotational speed target value calculator maintains the current rotational speed, so that target value = current value. On the other hand, since the initial integral value has no deviation in the rotational speed, the fuel flow rate produced by the proportional computation unit is only the steady fuel flow rate. Therefore, the integral computation unit is the current fuel flow rate minus this steady fuel flow rate. It only has to be created.

  Furthermore, when switching from isochronous to output droop mode, integration control is used as it is, so initialization is not necessary, but it is necessary to set the rotational speed deviation to a standard speed addition rate (for example, 4%) during maximum output operation. Since the current output power is maintained, if the value obtained by dividing the current output power by the maximum power and the speed addition rate (4%) is used as the rotation speed deviation, the output power does not fluctuate. The control mode can be switched.

Therefore, the following effects can be obtained by the method of the present invention.
(1) Since the fluctuation of the rotation speed can be suppressed when the control mode is switched to the single operation, the power generation frequency does not fluctuate.
(2) It is possible to suppress fluctuations in output power when switching the control mode to grid-linked operation.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a control mode switching method of the gas turbine power generator. As shown in this figure, the method of the present invention comprises steps S1 to S9.

In step S1, the rotational speed loop control target value calculating means calculates the rotational speed target value N _gref in the rotational speed loop control mode from the current fuel flow W _f and the constant fuel flow rate W _fss and the current rotational speed Ng. In this step S1, a steady fuel flow W _fss subtracted from the current control fuel flow W _fref, which was added to the current actual rotational speed N _g as the rotation speed deviation after switching the divided by the proportional gain K _p To calculate the rotation speed target value N _gref .

In step S2, the output droop control target value calculation means calculates the rotation speed target value N _gref in the output droop control mode from the current output power P and the rated rotation speed N. In step S2, the integration control is continuously applied as it is, and a value obtained by multiplying the current output power by the maximum power and the speed addition rate (for example, 4%) is set as the rotation speed deviation.

  In step S3, one of the engine operation control modes is selected by the governor mode selection means, and the rotation speed target value for causing the rotation speed target value selection means and integral initialization to be performed when the control mode is changed. Generate a selection pulse.

In step S4, the rotation speed target value selection means selects the rotation speed target value _Ngref of the gas turbine according to the selected control mode. Note that when the control mode is switched to the isochronous control the rotational speed loop control is to maintain the rotational speed target value N _gref to the current actual rotational speed N _g, steady fuel flow from the current fuel flow W _fref W _fss Is used as the initial value of the integral calculation unit.

  In step S5, the rotational speed target value integrating means integrates the rotational speed target value based on the speed increase / decrease command for increasing and decreasing the rotational speed, and selects the rotational speed target value when the governor mode is changed. Initialize with the value selected by the means.

  In step S6, the rotation speed deviation calculator calculates a deviation ΔN between the rotation speed target value Ngref and the current rotation speed Ng.

In step S7, the integral calculator, the rotation speed target value and the present rotational speed deviation ΔN multiplying the integral gain K _i, performs integration by adding the previous value, and the integration reset pulse, the integrated value currently Initialize with a value that does not break the state of. This integration is performed until the rotational speed deviation ΔN disappears.

In step S8, a proportional computing unit, the rotational speed target value and the present rotational speed deviation ΔN multiplied by a proportional gain K _p, by adding the constant fuel flow Wfss that value, calculates a fuel flow W _fref in loop control To do.
In step S9, the fuel flow rate adder adds the fuel flow rates from the proportional calculator and the integral calculator to calculate the fuel flow rate W _fref for the rotational speed control.

  The above-described control mode transition direction, rotation speed target value initialization, and integral initialization necessity are tabulated as follows. In this table, Ngcent is a rotational speed corresponding to the synchronous rotational speed of the system, and means the rated rotational speed in FIG.

(1) When switching from isochronous to the rotational speed droop control mode, the fuel flow produced by the rotational speed deviation is the fuel flow produced by the rotational speed deviation, which is obtained by subtracting the steady fuel flow (W _fss ) from the current fuel flow (W _fref ). The value divided by (K _p ) is the rotational speed deviation actually required.
(2) In switching from the rotational speed droop to the isochronous control mode, the rotational speed target value calculator maintains the current rotational speed, so that target value = current value. On the other hand, since the initial integral value has no deviation in the rotational speed, the fuel flow rate produced by the proportional computation unit is only the steady fuel flow rate. Therefore, the integral computation unit is the current fuel flow rate minus this steady fuel flow rate. It only has to be created.
(3) When switching from isochronous to output droop mode, integration control is used as it is, so initialization is not necessary. However, the current output power is required to set the rotation speed deviation to the standard 4% during maximum output operation. Therefore, if the value obtained by dividing the current output power by the maximum power and multiplying by 4% is used as the rotational speed deviation, the control mode can be switched without causing fluctuations in the output power.
The output droop is a mode for calculating the fuel flow rate from the deviation of the output power in order to control the output power. The governor mode is synonymous with the rotation speed control mode.

FIG. 2 shows a first embodiment of the present invention. This example shows changes in the rotation speed target value N _gref and the actual rotation speed N _gp when the rotation speed droop control mode is switched to the isochronous control mode. In this figure, the horizontal axis is time (unit: 0.25 sec), the left vertical axis is the control fuel flow rate W _fref and load (unit: kW / h), and the right vertical axis is the rotation speed target value N _gref and the actual rotation speed N _gp . Number of revolutions (rpm).
From this figure, even when the rotational speed droop control mode is switched to the isochronous control mode by an emergency shut-off or the like, the fluctuation of the actual rotational speed N _gp is small even though the load Load changes suddenly, and is about 0.5 to 0.6. It can be seen that the predetermined rotation speed is stabilized in seconds. In the conventional example, manual switching of the operator is required in this case, and at least about 10 seconds are required until the rotational speed is stabilized.

FIG. 3 is another embodiment of the present invention. This example shows changes in the rotational speed target value N _gref and the actual rotational speed N _gp when the isochronous control mode during the single load operation is switched to the rotational speed droop control mode. In this figure, the horizontal axis is time (unit: 0.25 sec), the left vertical axis is the control fuel flow rate W _fref and load (unit: kW / h), and the right vertical axis is the rotation speed target value N _gref and the actual rotation speed N _gp . Number of revolutions (rpm).
When synchronizing with the system from a single load operation and performing resynchronization, a reverse power state occurs if the phase is delayed from the delayed side, but reverse power drip can be avoided by immediately entering a speed increase command. Further, at the time of switching, the target rotational speed is raised so that the fuel flow rate does not change. However, when the rotational speed is not correctly 100% in the isochronous control mode, the output changes. .

  In addition, this invention is not limited to embodiment mentioned above, Of course, it can change variously in the range which does not deviate from the summary of this invention.

It is a block diagram which shows the control mode switching method of this invention. It is an Example of this invention. It is another Example of this invention. It is explanatory drawing of isochronous control and rotation speed droop control. 10 is a schematic diagram of Patent Document 1. FIG. It is a schematic diagram of patent document 2. FIG. It is a schematic diagram of patent document 3. FIG.

Claims (2)

A method for switching a control mode of a gas turbine power generator,
(A) In switching from isochronous control to rotational speed droop control, the value obtained by subtracting the steady fuel flow W _fss from the current control fuel flow W _fref and dividing this by the proportional gain K _p is used as the rotational speed deviation after switching. Add to the current actual speed Ng,
(B) In switching from rotational speed droop control to isochronous control, the rotational speed target value _Ngref is maintained at the current actual rotational speed Ng, the steady fuel flow rate _Wfss is subtracted from the current control fuel flow rate _Wfref , and integration is performed. A control mode switching method for a gas turbine power generator, characterized in that the initial value of a calculation unit is used. (C) In switching from isochronous control to output droop control, the integration control continues to be applied, and the value obtained by dividing the current output power by the maximum power multiplied by the speed addition rate is used as the rotational speed deviation. The method for switching a control mode of a gas turbine power generator according to claim 1.

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