JPH04303103A - Turbine control method and device - Google Patents

Abstract

PURPOSE:To prevent a turbine under constant load control from being brought into a high-frequency operating condition, and also to avoid the unnecessary stop of the turbine operation. CONSTITUTION:A turbine control device is constituted in such a way that the turbine speed signal is monitored by a monitoring circuit 2, and when it is judged by this monitoring circuit 2 that the number of revolutions of the turbine has reached a predetermined limit value, the turbine output is reduced at a prescribed rate of change until a set value is attained through a flip-flop 10, an analog memory 13, a change-rate controller 14, a subtracter 15, a proportional-plus-integral subtracter 16, and a low-value selecting circuit 20.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbine control method and apparatus applied to generators using gas turbines or steam turbines installed in areas with unstable power supply systems, such as developing countries.

0002

2. Description of the Related Art There are two known methods for controlling a gas turbine generator during power generation operation, which can be roughly divided into two types.

(1) Speed governor control (also referred to as governor control or governor free control) When a plurality of generators are connected and installed in parallel in a power system, their rotational speed is determined by the frequency of the power system. In other words, in areas where the basic frequency of the power system is 50 cycles, the basic rotation speed of generators installed in parallel is 50 cycles (
times/second) x 60 (seconds/minute) = 3,000 RPM (times/minute). The frequency of a power supply system is determined by the load (demand) connected to it and the power supplied by the generator. If there is an oversupply of electricity from the generator, the frequency will increase,
If there is excess demand, the frequency will drop.

[0004] Speed governor control is a method that adjusts the power generation output according to fluctuations in the power system frequency (that is, the rotational speed of the turbine generator) to keep the power system frequency almost constant. This is a control method commonly used in private generator turbines.

(2) Constant load control (also called load limit control) When a large-capacity gas turbine or steam turbine performs speed governor control, it increases or decreases its own output in accordance with frequency fluctuations in the power supply system. Temperature changes may become drastic, which may be undesirable. In particular, in the case of recent large-capacity gas turbines,
Because the aim is to achieve high efficiency, the combustion temperature is high, and the design and manufacturing of the compressor turbine must be extremely precise, which increases the problem of contact between various parts due to differences in the elongation of metal due to temperature differences. Therefore, these turbines are operated in a thermally uniform state, that is, under constant load operation. In addition, constant load control is increasingly used to control the turbine in order to maintain the generator output at a predetermined set value. In this case, control of the power system frequency as a whole has conventionally been performed by hydroelectric power plants, and recently by some thermal steam turbine power plants.

[0006] In Japan, Europe, and the United States, where power system frequency is often controlled, the frequency rarely fluctuates significantly from the fundamental frequency (50 cycles or 60 cycles). On the other hand, in developing countries, the power capacity of the power supply system is small, so the frequency of the power supply system often fluctuates relatively largely due to changes in load. Along with this frequency variation, the rotation speed of the turbine generator also varies. Typically,
Turbines are designed to be safest at the basic rotational speed, so if the rotational speed fluctuates more than this, problems such as turbine blade excitation may occur, resulting in undesirable results.

Therefore, conventionally, when the rotation speed of a turbine generator drops significantly below the basic rotation speed, the generator is disconnected from the power supply system to protect itself, and when the rotation speed increases significantly above the basic rotation speed, the generator is disconnected from the power supply system to protect itself. stops itself as overspeed,
The method used was to disconnect the generators at the same time.

[0008]

[Problems to be Solved by the Invention] In the above-mentioned conventional turbine control method using the constant load control method, the turbine generator is stopped only when the power system frequency increases significantly.
They were only protecting themselves. However, in reality, there is a rotational speed at which it is not desirable for the turbine to continue operating at that frequency for a long period of time, even if it is lower than the rotational speed (frequency) at which automatic stopping is performed.

[0009] Furthermore, once the turbine is stopped, it takes 15 to 30 minutes to start it again in the case of a large-capacity turbine.
This often takes more than a minute, which is not desirable from the standpoint of power system operation.

The present invention has been made in view of these conventional problems, and it is an object of the present invention to prevent a turbine under constant load control from being placed in a high frequency operating state, and to avoid unnecessary shutdown of the turbine. It is an object of the present invention to provide a turbine control method and device that can control the turbine.

[0011]

[Means for Solving the Problems] In order to solve the above problems, a turbine control method according to the present invention monitors the frequency of a power supply system in which a plurality of coupled generators are arranged in parallel, and It is characterized in that when the turbine operation increases to a predetermined limit value, an alarm is issued and the generator output is decreased at a predetermined rate of change until it reaches the set value.

Further, the turbine control device according to the present invention includes:
means for monitoring a turbine rotational speed signal; and means for reducing the output of the turbine at a predetermined rate of change until a set value is reached when the means determines that the turbine rotational speed has reached a predetermined limit value. It is characterized by having the following. Among the multiple control signals that control the output of the turbine,
It may further include means for selecting and outputting the smallest value.

[0013]

[Operation] In the present invention, when the rotational speed of the turbine, that is, the frequency of the power supply system increases to a predetermined limit value for turbine operation, that is, a value that is unfavorable for turbine operation, during operation of the turbine generator, an alarm is issued. is uttered,
At the same time, the generator output decreases at a predetermined rate of change until it reaches the set value.

The present invention provides a combined power generation plant in which, for example, a gas turbine generator generates steam in an exhaust heat recovery boiler using exhaust heat of the gas turbine, and this steam drives a steam turbine generator to generate electric power. Applies to. In such a plant, if the output of the gas turbine generator is unnecessarily reduced, the temperature of the exhaust gas decreases and the temperature of the steam generated from the boiler decreases, resulting in an unfavorable state for the steam turbine. When the present invention is applied,
Since the gas turbine is not immediately stopped even if the rotation speed of the gas turbine reaches a limit value, such a problem is avoided. Furthermore, when the power system frequency decreases during load runback and a new amount of heat generation is required, the load can be increased again at the operator's discretion.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a gas turbine control system to which the present invention is applied. This gas turbine control device has inputs such as a generator rotational speed signal 1 from the gas turbine generator, a generator output signal 3, a generator status signal 5 that is turned on during power generation operation, and manual input by the operator. load increase command signal 6, load decrease command signal 11, rotation speed control output 1
7. Exhaust gas temperature control output 18, surge limit output 19
etc. are input. Note that the control signals such as the rotation speed control output 17, the exhaust gas temperature control output 18, and the surge limit output 19 are merely examples, and the outputs may be different depending on the turbine generator control method.

The rotational speed control signal 1 is input to a monitor circuit 2 . This monitor circuit 2 detects that the rotation speed of the generator (basic rotation speed is 3,000 RPM) is a limit value, for example 3.0 RPM.
When the RPM exceeds 90 RPM, the output turns on (“H” level)
This is a circuit whose output turns off ("L" level) when the RPM falls below 3,090 RPM. The output of the monitor circuit 2 is input to an AND (logical product) circuit 7, and the logical product with the generator status signal 5 is taken.

On the other hand, the generator output signal 3 is input to a monitor circuit 4. This monitor circuit 4 has a generator output of, for example, 3.
This is a circuit whose output turns on ("H" level) when the power exceeds 0 MW, and turns off ("L" level) when it falls below 30 MW. The output of monitor circuit 4 is NOT (
After being inverted by a negation circuit 8, it is input to one input terminal of an OR (logical sum) circuit 9. The load increase command signal 6 is input to the other input terminal of the OR circuit 9 .

The output of the AND circuit 7 is the flip-flop 1
0 is input to the set input terminal S, and the output of the OR circuit 9 is input to the reset input terminal R of the flip-flop 10. The flip-flop 10 outputs an "H" level when the signal input to the terminal S is at the "H" level, and maintains this state until the signal input to the terminal R reaches the "H" level. The circle mark attached to the symbol of terminal S indicates that priority is given to set. flip flop 1
The output of 0 is input to one input terminal of the OR circuit 12. The load reduction command signal 11 is input to the other input terminal of the OR circuit 12 .

Load increase command signal 6 and load decrease command signal 1
1 is also input to the + and - side input terminals of the analog memory 13, respectively. The analog memory 13 increases its output at a predetermined rate of change when the signal input to the + side input terminal is at the "H" level, and when the signal input to the - side input terminal is at the "H" level. It is configured to reduce its output from time to time at a predetermined rate of change.

The output of analog memory 13 is input to rate of change controller 14 . Even when the input signal changes rapidly, the rate of change controller 14 changes its output signal to follow (match) the input signal at a predetermined rate of change. The output of this change rate controller 14 is input to the + side input terminal of the subtracter 15. The generator output signal 3 is input to the negative input terminal of the subtracter 15 .

The output of the subtracter 15 is input to a proportional-integral subtractor 16, from which a constant load control output is obtained. The low value selection circuit 20 outputs the smallest value among the load constant control output, rotation speed control output 17, exhaust gas temperature control output 18, and surge limit output 19 from the proportional-integral subtractor 16, which are its inputs. The circuit generates a fuel valve control output 21 as an output. In reality, a forced open signal for ignition/warm-up, a misfire prevention signal, a signal processing circuit when using a plurality of fuels, etc. are further added to the latter stage of the circuit shown in FIG. 1, and are used as operation signals for the control valve.

Next, the operation of the gas turbine control system of this embodiment will be explained. Now, during power generation operation of a gas turbine generator, the frequency of the power supply system in which multiple generators are connected and installed in parallel increases, for example, to 51.5 cycles (the rotational speed of the gas turbine generator is 3,090 RPM). If this exceeds the current level (equivalent), this will be detected by the monitor circuit 2, and the output of the monitor circuit 2 will become "H" level, indicating that the generator is currently in high frequency operation and a load runback (reducing operation) will be performed. An alarm signal is sent to the outside.

Output of this monitor circuit 2 (“H” level)
is input to the set input terminal S of the flip-flop 10 via the AND circuit 7, so that the load reduction signal is stored in the flip-flop 10. The output (load reduction signal) of the flip-flop circuit 10 is supplied to the negative input terminal of the analog memory 13 via the OR circuit 12. As a result, the analog memory 13, the rate of change controller 14,
Subtractor 15, proportional-integral subtractor 16 and low value selection circuit 2
0, the output of the generator is reduced at a constant rate of change. Further, when the load increase command signal 11 is inputted by manual operation by an operator, load reduction control is performed in the same manner.

Next, when the output of the generator decreases to a certain set value by such load reduction control, the output of the monitor circuit 4 that monitors the generator output signal 3 becomes "L" level, and the NOT circuit 8 becomes “H” level, so OR
By inputting the "H" level to the reset input terminal R of the flip-flop 10 via the circuit 9, the load reduction control is stopped. Further, when the load increase command signal 6 is input by manual operation by the operator, the load reduction control is similarly stopped, and then the load increase control is performed.

[0025] The flip-flop 10 is configured such that the rotation speed of the gas turbine generator once reaches 3,090 RPM during power generation operation.
If the rotation speed exceeds 3,090 RPM, the output will remain at the "H" level, and the output will not be output until the generator output falls below 30 MW or the load increase command signal 11 is input. It becomes “L” level.

The reason for this is that in an actual system, even if the power system frequency increases and the load reduction function of the present invention is activated, the capacity of the entire power system is extremely large.
If only the generator output is reduced, the contribution to the reduction in the power system frequency may not be very high, so if the generator output starts to decrease, it is better to lower it to 30 MW so that the operator can understand the situation and take countermeasures. This is based on the idea that it can be simplified.

[0027] If the rotation speed falls below 3,090 RPM and the operator determines that the generator output should stop decreasing,
All you have to do is press the load increase button on the control panel and input the load increase command signal 6. Of course, if there is a risk that the power system frequency will fall below the rated value due to the load reduction function of the present invention, it is also possible to adopt a configuration in which the flip-flop 10 is not provided. Note that although a gas turbine was used in the above description, the present invention can also be applied to a steam turbine or the like.

[0028]

[Effects of the Invention] As explained above, according to the present invention, when the rotation speed of the turbine generator increases to an unfavorable rotation speed (limit value) during power generation operation, it is determined that the turbine generator is in a high frequency operation state. , transmits an alarm signal to perform load runback, reduces the set value of constant load control at a predetermined rate of change, and controls the turbine output based on this, thereby operating the power supply system in a favorable direction, In addition, it becomes possible to shift the operating state to a more favorable direction for the own turbine.

[Brief explanation of the drawing]

FIG. 1 A block diagram of a turbine control device according to an embodiment of the present invention.

[Explanation of symbols]

2...Monitor circuit for generator rotation speed 4
... Generator output monitor circuit 7 ... AND circuit
8...NOT circuit 9, 12...OR circuit
10...Flip-flop 13...Analog memory
14... Rate of change controller 15... Subtractor
16...Proportional-integral subtractor 20...Low value selection circuit

Claims (3)

[Claims] Claim 1: Monitors the frequency of a power supply system consisting of a plurality of coupled generators installed in parallel, and when this frequency increases to a predetermined limit value for turbine operation, issues an alarm and A turbine control method characterized by reducing machine output at a predetermined rate of change until it reaches a set value. 2. Means for monitoring the rotational speed of a turbine, and when it is determined by the means that the rotational speed of the turbine has reached a predetermined limit value, the output of the turbine is changed in a predetermined manner until the output of the turbine reaches a predetermined value. A turbine control device characterized by comprising: means for reducing the rate. 3. Claim 2, further comprising a low value selection circuit for selecting and outputting the smallest value among a plurality of control outputs for controlling the output of the turbine.
The turbine control device described.