JP7620480B2 - Apparatus and method for detecting clutch condition in a single-shaft combined cycle power plant - Google Patents

Description

The present invention relates to a clutch state detection device and method for a single-shaft combined cycle power plant.

A single-shaft combined cycle power plant has a common rotating shaft that connects a gas turbine, a generator, and a steam turbine. Some such power plants have a clutch installed on the rotating shaft between the generator and the steam turbine, and this clutch switches the power transmission between the generator and the steam turbine between connected and disconnected states.

In a typical startup operation of a single-shaft combined cycle power plant equipped with a clutch as described above, first, the power transmission between the generator and the steam turbine is interrupted by the clutch. Next, the gas turbine is rotated, and the generator is rotated by the rotation of the gas turbine. Then, after the gas turbine reaches the rated rotation speed, the generator is connected in parallel to the power grid.

After the parallel operation, steam generated in the heat recovery boiler by the exhaust gas from the gas turbine is supplied to the steam turbine, which drives and rotates it. When the steam turbine reaches its rated rotational speed, the clutch switches the power transmission between the generator and the steam turbine to a connected state, and the rotational power of the steam turbine is also transmitted to the generator. The clutch is usually configured to mechanically and automatically switch to a connected state when the steam turbine reaches its rated rotational speed.

Figure 4 is a graph illustrating the general start-up operation described above. In particular, the graph in Figure 4 shows the state after the gas turbine has reached its rated rotational speed and the generator has been paralleled. The horizontal axis of the graph shown is time, and the vertical axis is turbine rotational speed. The line indicated by the symbol R1 indicates the rotational speed of the gas turbine, the line indicated by the symbol R2 indicates the rotational speed of the steam turbine, and the line indicated by the symbol MW indicates the generator output.

When the gas turbine rotation speed R1 reaches and is maintained at the rated rotation speed, the generator output MW becomes essentially a constant value. Then, at a predetermined timing in this state (at "ST start" on the time axis in Figure 4), the steam turbine is rotated and driven. Thereafter, the steam turbine rotation speed R2 gradually increases and is then maintained at the rated rotation speed. Then, as shown by "clutch connected" on the time axis, the clutch switches the power transmission between the generator and steam turbine to a connected state. As a result, the power of the steam turbine is also transmitted to the generator, and the generator output MW increases.

In order to perform good control in a single-shaft combined cycle power plant equipped with a clutch as described above, a function for accurately detecting clutch engagement and disengagement is required. Figure 5 shows the schematic configuration of an example of a clutch state detection device that can be used in a single-shaft combined cycle power plant.

The clutch state detection device in FIG. 5 includes a speed difference detection unit 201 and a holding circuit unit 202. This clutch state detection device focuses on the fact that the gas turbine rotation speed R1 and the steam turbine rotation speed R2 match when the clutch is engaged, and the speed difference detection unit 201 detects the rotation speed difference (GT/ST rotation speed difference) between the gas turbine rotation speed R1 and the steam turbine rotation speed R2. The holding circuit unit 202 receives the detection result from the speed difference detection unit 201 and enters a set state when the GT/ST rotation speed difference is small, and enters a reset state when the GT/ST rotation speed difference is large. For example, when the holding circuit unit 202 is in the set state, the clutch is engaged, and when it is in the reset state, the clutch is disengaged.

However, in the configuration shown in FIG. 5, the clutch engagement state may be detected even when the rotational speed of the gas turbine and steam turbine is reduced after the clutch is disengaged. FIG. 6 is a graph illustrating an example of how the clutch state detection device shown in FIG. 5 detects the clutch engagement state when the rotational speed of the gas turbine and steam turbine is reduced.

In the example of Figure 6, after the clutch is disengaged, first the steam turbine is stopped, then the gas turbine is stopped, and their respective rotational speeds R1, R2 gradually decrease. Then, because the turbine time constant of the gas turbine is smaller than the time constant of the steam turbine, even though the gas turbine was stopped later, its reduced rotational speed R1 catches up with the reduced rotational speed R2 of the steam turbine. In this case, after the gas turbine is stopped but before the steam turbine is stopped, the GT/ST rotational speed difference becomes large, and the clutch is detected as disengaged, but after the steam turbine is stopped, the GT/ST rotational speed difference becomes small, and the clutch is detected as engaged.

During normal startup operation, when power transmission between the generator and steam turbine is connected, the steam supply is increased to increase the output of the steam turbine. For example, if the process of increasing the steam supply is automated so that it begins in response to detection of a clutch connected state, a situation may arise in which the output of the steam turbine increases in response to the clutch connected state detected during deceleration as described above. In this case, undesirable operation may occur.

JP 2003-13709 A

The problem that the present invention aims to solve is to provide a clutch state detection device and method that can detect the clutch state of a single-shaft combined cycle power plant in a desired manner.

In one embodiment, the clutch state detection device for a single-shaft combined cycle power plant is a clutch state detection device for a single-shaft combined cycle power plant in which a gas turbine, a generator, and a steam turbine are connected by a shared rotating shaft, and power transmission between the generator and the steam turbine is switched between an engaged state and an unengaged state by a clutch. This clutch state detection device includes a speed difference detection unit that detects whether the rotational speed difference between the rotational speed of the gas turbine and the rotational speed of the steam turbine is equal to or less than a predetermined value, a steam pressure detection unit that detects whether the inlet steam pressure of the steam turbine is equal to or greater than a predetermined pressure, and a determination unit that determines that the clutch is engaged when the speed difference detection unit detects that the rotational speed difference is equal to or less than the predetermined value and the steam pressure detection unit detects that the inlet steam pressure is equal to or greater than the predetermined pressure.

In one embodiment, the clutch state detection device for a single-shaft combined cycle power plant is a clutch state detection device for a single-shaft combined cycle power plant in which a gas turbine, a generator, and a steam turbine are connected by a shared rotating shaft, and power transmission between the generator and the steam turbine is switched between an engaged state and an unengaged state by a clutch. This clutch state detection device includes a speed difference detection unit that detects whether the rotational speed difference between the rotational speed of the gas turbine and the rotational speed of the steam turbine is equal to or less than a predetermined value, a power generation output detection unit that detects whether the power generation output of the generator has increased, and a determination unit that determines that the clutch is engaged when the speed difference detection unit detects that the rotational speed difference is equal to or less than a predetermined value and the power generation output detection unit detects that the power generation output has increased.

In one embodiment, the clutch state detection method in a single-shaft combined cycle power plant is a clutch state detection method in a single-shaft combined cycle power plant in which a gas turbine, a generator, and a steam turbine are connected by a shared rotating shaft, and power transmission between the generator and the steam turbine is switched between an engaged state and an unconnected state by a clutch. This method includes a speed difference detection process for detecting whether the rotational speed difference between the rotational speed of the gas turbine and the rotational speed of the steam turbine is equal to or less than a predetermined value, a steam pressure detection process for detecting whether the inlet steam pressure of the steam turbine is equal to or greater than a predetermined pressure, and a determination process for determining that the clutch is engaged when the speed difference detection process detects that the rotational speed difference is equal to or less than the predetermined value and the steam pressure detection process detects that the inlet steam pressure is equal to or greater than the predetermined pressure.

In one embodiment, the clutch state detection method in a single-shaft combined cycle power plant is a clutch state detection method in a single-shaft combined cycle power plant in which a gas turbine, a generator, and a steam turbine are connected by a shared rotating shaft, and power transmission between the generator and the steam turbine is switched between an engaged state and an unconnected state by a clutch. This method includes a speed difference detection step for detecting whether the rotational speed difference between the rotational speed of the gas turbine and the rotational speed of the steam turbine is equal to or less than a predetermined value, a power generation output detection step for detecting whether the power generation output of the generator has increased, and a determination step for determining that the clutch is engaged when the speed difference detection step detects that the rotational speed difference is equal to or less than a predetermined value and the power generation output detection step detects that the power generation output has increased.

According to the present invention, the state of the clutch of a single-shaft combined cycle power plant can be detected in a desired manner.

1 is a diagram illustrating a schematic configuration of a single-shaft combined cycle power plant including a clutch state detection device according to a first embodiment. 1 is a diagram illustrating a schematic configuration of a clutch state detection device according to a first embodiment; FIG. 13 is a diagram illustrating a schematic configuration of a clutch state detection device according to a second embodiment. FIG. 1 is a graph illustrating a typical start-up operation of a single-shaft combined cycle power plant. FIG. 1 is a diagram showing a schematic configuration of an example of a clutch state detection device that can be used in a single-shaft combined cycle power plant. 6 is a graph illustrating an example of how the clutch state detection device illustrated in FIG. 5 detects a clutch engagement state during deceleration. FIG.

Each embodiment will be described in detail below with reference to the attached drawings.

First Embodiment
FIG. 1 shows a schematic diagram of a single-shaft combined cycle power plant 1 including a clutch state detection device 100 according to a first embodiment.

The single-shaft combined cycle power plant 1 in FIG. 1 includes a gas turbine 2, a generator 3, and a steam turbine 4. The gas turbine 2, the generator 3, and the steam turbine 4 share a single rotating shaft 5 and are connected by this rotating shaft 5. This forms the power train of the single-shaft combined cycle power plant 1.

The gas turbine 2, the generator 3, and the steam turbine 4 are arranged on the rotating shaft 5 such that the generator 3 is located between the gas turbine 2 and the steam turbine 4. A clutch 6 is provided in the portion of the rotating shaft 5 between the generator 3 and the steam turbine 4, and the clutch 6 is configured to switch the power transmission between the generator 3 and the steam turbine 4 between a connected state and a disconnected state.

When the rotational speed of the gas turbine 2 and generator 3 matches the rotational speed of the steam turbine 4, the clutch 6 engages with the part on the generator 3 side and the part on the steam turbine 4 side, and when the speed difference between the rotational speed of the gas turbine 2 and generator 3 and the rotational speed of the steam turbine 4 becomes greater than a certain level, the part on the generator 3 side and the part on the steam turbine 4 side separate, and the clutch 6 enters a disconnected state.

When the clutch 6 is in an engaged state, the rotation of the steam turbine 4 is transmitted to the generator 3 via the clutch 6, and power transmission between the generator 3 and the steam turbine 4 is in a connected state. On the other hand, when the clutch 6 is in a disengaged state, the rotation of the steam turbine 4 is not transmitted to the generator 3 via the clutch 6, and power transmission between the generator 3 and the steam turbine 4 is in a disconnected state.

When the power transmission between the generator 3 and the steam turbine 4 is connected, the rotational power of the gas turbine 2 and the rotational power of the steam turbine 4 can be transmitted to the generator 3 simultaneously, thereby increasing the power generation output. The structure of the clutch 6 is not particularly limited, and for example, a meshing clutch such as a helical spline engagement, a friction clutch, etc. can be used.

Fuel f is supplied to the gas turbine 2 via a fuel control valve 7, and steam Sh and Sr from a heat recovery steam generator (not shown) or the like are supplied to the steam turbine 4 via steam control valves 8 and 9.

In this embodiment, the steam turbine 4 has, as an example, a high-pressure turbine 10, an intermediate-pressure turbine 11, and a low-pressure turbine 12. The high-pressure turbine 10 is supplied with high-pressure steam Sh from the heat recovery boiler via a high-pressure steam control valve 8, and is rotated by the high-pressure steam Sh. The heat recovery boiler generates high-pressure steam using the heat of the exhaust gas from the gas turbine 2, and supplies it to the high-pressure turbine 10.

The intermediate pressure turbine 11 is supplied with reheated steam Sr via the reheat steam control valve 9 and rotates with the reheated steam Sr. The reheated steam Sr is generated, for example, by heating the steam discharged by the high pressure turbine 10 with a reheater (not shown). The pressure of such reheated steam Sr is lower than the pressure of the high pressure steam.

On the other hand, the low-pressure turbine 12 is configured to rotate by the steam discharged by the intermediate-pressure turbine 11. Note that the steam turbine 4 is not limited to the example shown in the figure, and may be, for example, one composed of a high-pressure turbine and a low-pressure turbine, or one composed of a single turbine.

A first steam pressure sensor 13 is provided in the steam flow path between the steam inlet formed in the casing of the intermediate pressure turbine 11 and the reheat steam control valve 9, and a second steam pressure sensor 14 is provided in the steam flow path between the steam inlet formed in the casing of the high pressure turbine 10 and the high pressure steam control valve 8. The first steam pressure sensor 13 detects the inlet steam pressure of the intermediate pressure turbine 11 flowing into the steam inlet of the intermediate pressure turbine 11, and the second steam pressure sensor 14 detects the inlet steam pressure of the high pressure turbine 10 flowing into the steam inlet of the high pressure turbine 10.

In addition, in this embodiment, a first speed sensor 15 that detects the rotational speed of the gas turbine 2 and a second speed sensor 16 that detects the rotational speed of the steam turbine 4 are further provided. The first speed sensor 15 is disposed on the generator 3 and gas turbine 2 side with respect to the clutch 6, and the second speed sensor 16 is disposed on the steam turbine 4 side with respect to the clutch 6. Each of these sensors 15, 16 may be, for example, a rotary encoder, etc.

The start-up operation of the single-shaft combined cycle power plant 1 described above is performed in the same procedure as the general start-up operation described above. That is, at the time of start-up, first, the power transmission between the generator 3 and the steam turbine 4 is interrupted by the clutch 6. Next, the gas turbine 2 is rotated, and the generator 3 is rotated by the rotation of the gas turbine 2. Then, after the gas turbine 2 reaches the rated rotation speed, the generator 3 is paralleled to the power grid. Then, after the paralleling, high-pressure steam Sh generated in the heat recovery boiler by the exhaust gas of the gas turbine 2 is supplied to the steam turbine 4, and the steam turbine 4 is rotated.

Here, the high-pressure steam control valve 8 gradually increases the valve opening so that the rotation speed of the steam turbine 4 rises toward the rated rotation speed, thereby increasing the supply amount of high-pressure steam Sh. When the supply amount of high-pressure steam Sh is increased in this way, the inlet steam pressure of the high-pressure turbine 10 increases in proportion to the supply amount. The reheat steam control valve 9 also gradually increases the valve opening so that the rotation speed of the steam turbine 4 rises toward the rated rotation speed, thereby increasing the supply amount of reheat steam Sr. When the supply amount of reheat steam Sr is increased in this way, the inlet steam pressure of the intermediate pressure turbine 11 also increases in proportion to the supply amount. Then, when the steam turbine 4 reaches the rated rotation speed, the clutch 6 switches the power transmission between the generator 3 and the steam turbine 4 to a connected state, and the power of the steam turbine 4 is also transmitted to the generator 3.

The clutch state detection device 100 according to this embodiment is described below.

Figure 2 shows a schematic configuration of the clutch state detection device 100. As shown in Figure 2, the clutch state detection device 100 according to this embodiment has a speed difference detection unit 101, a steam pressure detection unit 102, and a determination unit 103.

The clutch state detection device 100 is composed of, for example, a PLC (Programmable Logic Controller) including a processor, and may realize various functions (the functions of the speed difference detection unit 101, the steam pressure detection unit 102, and the judgment unit 103) by reading and executing necessary programs from a memory unit. The memory unit is realized, for example, by a semiconductor memory element such as a RAM (Random Access Memory), a flash memory, a hard disk, an optical disk, etc.

The term "processor" refers to circuits such as a central processing unit (CPU), an application specific integrated circuit (ASIC), a programmable logic device (SPLD, CPLD), or a field programmable gate array (FPGA). On the other hand, the clutch state detection device 100 can also be configured as an IC chip having a logic circuit.

The speed difference detection unit 101 detects whether the rotational speed difference between the rotational speed of the gas turbine 2 and the rotational speed of the steam turbine 4 is equal to or less than a predetermined value, and the steam pressure detection unit 102 detects whether the inlet steam pressure of the steam turbine 4 is equal to or greater than a predetermined pressure. The determination unit 103 determines that the clutch 6 is in an engaged state when the speed difference detection unit 101 detects that the rotational speed difference is equal to or less than the predetermined value and the steam pressure detection unit 102 detects that the inlet steam pressure is equal to or greater than the predetermined pressure.

In detail, the speed difference detection unit 101 acquires information on the rotation speed R1 of the gas turbine 2 detected by the first speed sensor 15 and information on the rotation speed R2 of the steam turbine 4 detected by the second speed sensor 16, and compares the rotation speed difference between the rotation speed R1 of the gas turbine 2 and the rotation speed R2 of the steam turbine 4 with a first predetermined value (predetermined value) and a second predetermined value (another predetermined value) that is greater than the first predetermined value.

Then, when the speed difference detection unit 101 detects that the rotation speed difference is equal to or less than a first predetermined value, it inputs a "GT/ST rotation speed difference small" signal indicating that the rotation speed difference is small to the determination unit 103, and when the speed difference detection unit 101 detects that the rotation speed difference is equal to or more than a second predetermined value, it inputs a "GT/ST rotation speed difference large" signal indicating that the rotation speed difference is large to the determination unit 103.

The speed difference detection unit 101 is not limited to the above embodiment, and may be configured to compare the rotation speed difference with a predetermined value, and if the rotation speed difference is equal to or greater than the predetermined value, input a signal indicating a "small GT/ST rotation speed difference" to the determination unit 103, and if the rotation speed difference is less than the predetermined value, input a signal indicating a "large GT/ST rotation speed difference" to the determination unit 103.

The steam pressure detection unit 102 is configured to acquire information on the inlet steam pressure P1 of the intermediate pressure turbine 11 detected by the first steam pressure sensor 13 and information on the inlet steam pressure P2 of the high pressure turbine 10 detected by the second steam pressure sensor 14, compare the inlet steam pressure P1 of the intermediate pressure turbine 11 with a first predetermined pressure, and compare the inlet steam pressure P2 of the high pressure turbine 10 with a second predetermined pressure.

In detail, when the steam pressure detection unit 102 detects that the inlet steam pressure P1 of the intermediate pressure turbine 11 is equal to or higher than the first predetermined pressure as a predetermined pressure and the inlet steam pressure P2 of the high pressure turbine 10 is equal to or higher than the second predetermined pressure as a predetermined pressure, the steam pressure detection unit 102 judges that "the inlet steam pressure of the steam turbine 4 is equal to or higher than the predetermined pressure." When the steam pressure detection unit 102 judges that the inlet steam pressure of the steam turbine 4 is equal to or higher than the predetermined pressure, the steam pressure detection unit 102 inputs a "ST output present" signal to the judgment unit 103. Note that this "ST output present" signal is generated as a signal indicating that the inlet steam pressure of the steam turbine 4 is rising due to an increase in the amount of steam supply.

On the other hand, when the steam pressure detection unit 102 does not determine that the inlet steam pressure of the steam turbine 4 is equal to or greater than the predetermined pressure as described above, it inputs a "no ST output" signal to the determination unit 103. When the inlet steam pressure of the steam turbine 4 is not determined to be equal to or greater than the predetermined pressure, in this embodiment, this means that the inlet steam pressure P1 of the intermediate pressure turbine 11 is less than the first predetermined pressure and/or the inlet steam pressure P2 of the high pressure turbine 10 is less than the second predetermined pressure.

The steam pressure detection unit 102 may be configured to input a "ST output present" signal to the determination unit 103 when it detects that either the inlet steam pressure P1 of the intermediate pressure turbine 11 is equal to or greater than the first predetermined pressure, or the inlet steam pressure P2 of the high pressure turbine 10 is equal to or greater than the second predetermined pressure. In this case, the steam pressure detection unit 102 may be configured to acquire only information on the inlet steam pressure P1 of the intermediate pressure turbine 11. The steam pressure detection unit 102 may also be configured not to generate a "ST output absent" signal.

The determination unit 103 in this embodiment has a logical AND gate unit 104, a logical OR gate unit 105, and a holding circuit unit 106.

The logical AND gate unit 104 is configured to input the input signal In1 to the holding circuit unit 106 when an AND condition is met in which both the "GT/ST rotation speed difference small" signal from the speed difference detection unit 101 and the "ST output present" signal from the steam pressure detection unit 102 are obtained, and not to input the input signal In1 to the holding circuit unit 106 when the AND condition is not met.

The logical OR gate unit 105 is configured to input the input signal In2 to the holding circuit unit 106 when an OR condition is met in which at least one of the "GT/ST rotation speed difference large" signal from the speed difference detection unit 101 and the "no ST output" signal from the steam pressure detection unit 102 is acquired, and not to input the input signal In2 to the holding circuit unit 106 when no signal is acquired.

The holding circuit unit 106 is configured to be in a set state when it receives an input signal In1 from the logical AND gate unit 104, and to be in a reset state when it receives an input signal In2 from the logical OR gate unit 105. When the holding circuit unit 106 is in the set state, it generates a signal indicating that the clutch 6 is in an engaged state ("clutch engaged" in FIG. 2), and when it is in the reset state, it generates a signal indicating that the clutch 6 is in a disengaged state ("clutch disengaged" in FIG. 2). By referring to these signals, it is possible to determine the current state of the clutch 6.

In this embodiment, the holding circuit unit 106 uses a flip-flop circuit configuration, but the configuration is not particularly limited.

The operation of the clutch state detection device 100 will be explained below with reference to the start-up operation shown in Figure 4 and the state during deceleration after the clutch is disengaged shown in Figure 6.

First, in the start-up operation according to FIG. 4, after the gas turbine 2 reaches the rated rotation speed, high-pressure steam Sh, etc. generated in the heat recovery boiler by the exhaust gas of the gas turbine 2 is supplied to the steam turbine 4, which rotates and drives the steam turbine 4. Then, the rotation speed of the steam turbine 4 gradually increases, and when the rotation speed of the steam turbine 4 reaches the rated rotation speed, the clutch 6 connects the power transmission between the generator 3 and the steam turbine 4.

As described above, the rotational speed of the steam turbine 4 gradually increases, and the rotational speed difference between the rotational speed R1 of the gas turbine 2 and the rotational speed R2 of the steam turbine 4 becomes smaller. At this time, when the speed difference detection unit 101 detects that the rotational speed difference is equal to or less than the first predetermined value, the clutch state detection device 100 inputs a "GT/ST rotational speed difference small" signal indicating that the rotational speed difference is small from the speed difference detection unit 101 to the determination unit 103 (speed difference detection process).

As described above, when the rotation speed of the steam turbine 4 gradually increases toward the rated rotation speed, the inlet steam pressure P1 of the intermediate pressure turbine 11 and the inlet steam pressure P2 of the high pressure turbine 10 gradually increase. When the steam pressure detection unit 102 detects that the inlet steam pressure P1 of the intermediate pressure turbine 11 is equal to or greater than the first predetermined steam pressure and the inlet steam pressure P2 of the high pressure turbine 10 is equal to or greater than the second predetermined pressure, the clutch state detection device 100 determines that the inlet steam pressure of the steam turbine 4 is equal to or greater than the predetermined pressure, and inputs a "ST output available" signal from the steam pressure detection unit 102 to the determination unit 103 (steam pressure detection process).

As described above, when the "GT/ST rotation speed difference small" signal and the "ST output present" signal are input to the judgment unit 103 (more specifically, the logical product gate unit 104), a logical product is established in the logical product gate unit 104, and the clutch state detection device 100 inputs the input signal In1 from the logical product gate unit 104 to the holding circuit unit 106. At this time, the holding circuit unit 106 is set, and generates a signal indicating that the clutch 6 is in an engaged state. As a result, the clutch state detection device 100 judges that the current state of the clutch 6 is in an engaged state, and more specifically, judges that the clutch 6 is in an engaged state at the time of startup (judgment process).

On the other hand, when the speed is reduced after the clutch is disengaged as shown in FIG. 6, the steam turbine 4 is first stopped after the clutch is disengaged, and then the gas turbine 2 is stopped, and the rotation speed R1 of the gas turbine 2 and the rotation speed R2 of the steam turbine 4 gradually decrease. Then, even though the gas turbine 2 is stopped later, the rotation speed R1 of the gas turbine 2 catches up with the reduced rotation speed R2 of the steam turbine 4.

At this time, in the clutch state detection device 100, after the gas turbine 2 is stopped and before the steam turbine 4 is stopped, the speed difference detection unit 101 detects that the rotational speed difference between the rotational speed R1 of the gas turbine 2 and the rotational speed R2 of the steam turbine 4 is equal to or greater than the second predetermined value. Then, a signal indicating that the rotational speed difference is large is input from the speed difference detection unit 101 to the determination unit 103. As a result, in the clutch state detection device 100, a logical sum is established in the logical sum gate unit 105 in the determination unit 103, and the input signal In2 is input from the logical sum gate unit 105 to the holding circuit unit 106. At this time, the holding circuit unit 106 is reset, a signal indicating that the clutch 6 is in a disengaged state is generated, and the clutch state detection device 100 determines that the current state of the clutch 6 is in a disengaged state.

When the rotation speed R2 of the steam turbine 4 decreases, the inlet steam pressure P1 of the intermediate pressure turbine 11 and the inlet steam pressure P2 of the high pressure turbine 10 gradually decrease. Therefore, the clutch state detection device 100 detects at a certain timing that the inlet steam pressure P1 of the intermediate pressure turbine 11 is less than the first predetermined pressure and/or the inlet steam pressure P2 of the high pressure turbine 10 is less than the second predetermined pressure using the steam pressure detection unit 102. At this time, a "no ST output" signal is input from the steam pressure detection unit 102 to the determination unit 103. This also resets the holding circuit unit 106, generates a signal indicating that the clutch 6 is in a disengaged state, and the clutch state detection device 100 determines that the current state of the clutch 6 is in a disengaged state.

In addition, when the rotation speed R1 of the gas turbine 2 catches up with the reduced rotation speed R2 of the steam turbine 4, the speed difference detection unit 101 detects that the rotation speed difference between the rotation speed R1 of the gas turbine 2 and the rotation speed R2 of the steam turbine 4 is equal to or less than the first predetermined value, and a "GT/ST rotation speed difference small" signal indicating that the rotation speed difference is small is input from the speed difference detection unit 101 to the determination unit 103.

However, when the rotation speed R2 of the steam turbine 4 decreases, the inlet steam pressure P1 of the intermediate pressure turbine 11 and the inlet steam pressure P2 of the high pressure turbine 10 decrease. Therefore, the clutch state detection device 100 does not detect that the inlet steam pressure P1 of the intermediate pressure turbine 11 is equal to or higher than the first predetermined pressure and the inlet steam pressure P2 of the high pressure turbine 10 is equal to or higher than the second predetermined pressure. Therefore, the "ST output present" signal is not input to the logical product gate unit 104 of the judgment unit 103. Therefore, a logical product is not established in the logical product gate unit 104, and the input signal In1 is not input from the logical product gate unit 104 to the holding circuit unit 106. Therefore, the reset state of the holding circuit unit 106 is maintained, and it is not detected that the clutch 6 is in an engaged state.

The clutch state detection device 100 according to the present embodiment described above includes a speed difference detection unit 101 that detects whether the rotational speed difference between the rotational speed R1 of the gas turbine 2 and the rotational speed of the steam turbine 4 is equal to or less than a predetermined value (in this example, a first predetermined value), a steam pressure detection unit 102 that detects whether the inlet steam pressure of the steam turbine 4 is equal to or greater than a predetermined pressure (in this example, the inlet steam pressure P1 of the intermediate pressure turbine ≧ the first predetermined pressure, and the inlet steam pressure P2 of the high pressure turbine ≧ the second predetermined pressure), and a determination unit 103 that determines that the clutch 6 is in an engaged state when the speed difference detection unit 101 detects that the rotational speed difference is equal to or less than the predetermined value and the steam pressure detection unit 102 detects that the inlet steam pressure is equal to or greater than the predetermined pressure.

In other words, this clutch state detection device 100 determines whether the clutch 6 is engaged or not by considering not only whether the rotational speed difference between the rotational speed R1 of the gas turbine 2 and the rotational speed R2 of the steam turbine 4 has become smaller, but also whether the inlet steam pressure has become larger.

This allows the state of the clutch 6 to be detected in a desired manner. Specifically, the clutch 6 engagement state can be detected in a manner that detects only the clutch 6 engagement state at startup and excludes detection of the clutch 6 engagement state during deceleration. In particular, in this embodiment, the clutch 6 determines the clutch engagement state based on an increase in the inlet steam pressure as one of the criteria, which is advantageous in terms of responsiveness of the determination.

In addition, the speed difference detection unit 101 in this embodiment also detects whether the rotational speed difference is equal to or greater than another predetermined value (second predetermined value) that is greater than the predetermined value (first predetermined value), and determines that the rotational speed difference is large when the rotational speed difference is equal to or greater than the other predetermined value. Then, the determination unit 103 determines that the clutch 6 is in a disengaged state when the speed difference detection unit 101 detects that the rotational speed difference is equal to or greater than the other predetermined value.

In this way, when the speed difference detection unit 101 uses two judgment criteria (a predetermined value and another predetermined value) to judge whether the rotational speed difference is small or large, it is possible to avoid undesired detection of a small or large rotational speed difference due to a rotational speed detection error. Therefore, it is possible to improve the reliability of the clutch state judgment performed by the judgment unit 103.

In addition, in this embodiment, the judgment unit 103 judges that the clutch 6 is in a disengaged state when the speed difference detection unit 101 does not detect that the rotational speed difference is equal to or less than a predetermined value (more specifically, when the rotational speed difference is not detected to be equal to or less than a first predetermined value and is detected to be equal to or greater than a second predetermined value) and/or when the steam pressure detection unit 102 does not detect that the inlet steam pressure is equal to or greater than a predetermined pressure (more specifically, when the inlet steam pressure P1 of the intermediate pressure turbine is equal to or greater than the first predetermined pressure and the inlet steam pressure P2 of the high pressure turbine is equal to or greater than the second predetermined pressure).

In this manner, in a configuration in which the determination unit 103 determines that the clutch 6 is in a disengaged state when at least one of the two conditions is satisfied, the responsiveness when determining the disengaged state of the clutch 6 can be improved.

In addition, when the steam pressure detection unit 102 in this embodiment detects that the inlet steam pressure of the steam turbine 4 is rising when it detects that the inlet steam pressure P1 of the intermediate pressure turbine is greater than or equal to the first predetermined pressure and the inlet steam pressure P2 of the high pressure turbine is greater than or equal to the second predetermined pressure, the steam pressure detection unit 102 inputs an "ST output present" signal, which indicates that the inlet steam pressure of the steam turbine 4 is rising, to the determination unit 103. The "ST output present" signal is an index for determining the clutch engagement state, and in this embodiment, the determination criterion for generating this signal is when two conditions are met simultaneously. This improves the reliability of determining the clutch engagement state.

Second Embodiment
Next, a second embodiment will be described with reference to Figures 1 and 3. Figure 3 shows a schematic configuration of a clutch state detection device 110 according to the second embodiment. The clutch state detection device 110 shown in Figure 3 has a speed difference detection unit 111, a power generation output detection unit 112, and a determination unit 113. The clutch state detection device 110 is applied to the single-shaft combined cycle power plant 1 shown in Figure 1, and the components described in Figure 1 may be used in the following description of the clutch state detection device 110, but detailed description thereof will be omitted.

In this embodiment, the speed difference detection unit 111 detects whether the rotational speed difference between the rotational speed of the gas turbine 2 and the rotational speed of the steam turbine 4 is equal to or less than a predetermined value, and the power generation output detection unit 112 detects whether the power generation output of the generator 3 has increased. Then, the determination unit 113 determines that the clutch 6 is in an engaged state when the speed difference detection unit 101 detects that the rotational speed difference is equal to or less than a predetermined value and the power generation output detection unit 112 detects that the power generation output has increased.

In detail, the speed difference detection unit 111 acquires information on the rotation speed R1 of the gas turbine 2 detected by the first speed sensor 15 and information on the rotation speed R2 of the steam turbine 4 detected by the second speed sensor 16, and compares the rotation speed difference between the rotation speed R1 of the gas turbine 2 and the rotation speed R2 of the steam turbine 4 with a first predetermined value (predetermined value) and a second predetermined value (another predetermined value) that is greater than the first predetermined value.

Then, when the speed difference detection unit 111 detects that the rotation speed difference is equal to or less than a first predetermined value, it inputs a "GT/ST rotation speed difference small" signal indicating that the rotation speed difference is small to the determination unit 103, and when the rotation speed difference is equal to or greater than a second predetermined value, it inputs a "GT/ST rotation speed difference large" signal indicating that the rotation speed difference is large to the determination unit 113.

The power generation output detection unit 112 sequentially calculates the difference between the power generation outputs of the generator 3 at, for example, two different points in time, and determines that the power generation output has increased when the calculated difference is equal to or greater than a predetermined output value. When the power generation output detection unit 112 determines that the power generation output has increased, it inputs a "generator output increase" signal indicating that the power generation output has increased to the determination unit 103. In this embodiment, it is assumed that the "generator output increase" signal is generated when the power generation output increases to a level at which the clutch 6 transitions from a disconnected state to a connected state. In this embodiment, the power generation output detection unit 112 is configured to sequentially acquire information on the power generation output MW of the generator 3 in order to sequentially calculate the difference between the power generation outputs of the generator 3 at two different points in time.

The processing of the power generation output detection unit 112 is not limited to the above-mentioned manner, and for example, it may be possible to determine whether the power generation output of the generator 3 has increased by comparing the increase rate of the power generation output over a specified period of time, an integral value, etc., with a corresponding threshold value.

In addition, in this embodiment, the judgment unit 113 is composed of a logical product gate unit 114 and a holding circuit unit 116. The logical product gate unit 114 is configured to input the input signal In1 to the holding circuit unit 116 when an AND condition is met in which both a "small GT/ST rotation speed difference" signal from the speed difference detection unit 111 and an "increased generator output" signal from the power generation output detection unit 112 are obtained, and not to input the input signal In1 to the holding circuit unit 116 when the AND condition is not met.

As described above, the holding circuit unit 116 is configured to receive the input signal In1 from the logical product gate unit 114 or the signal "GT/ST rotation speed difference large" from the speed difference detection unit 111. The holding circuit unit 116 is configured to enter a set state when it receives the input signal In1 from the logical product gate unit 114, and to enter a reset state when it receives the signal "GT/ST rotation speed difference large" from the speed difference detection unit 111.

When the holding circuit unit 116 is in the set state, it generates a signal indicating that the clutch 6 is in an engaged state ("Clutch engaged" in FIG. 3), and when the holding circuit unit 116 is in the reset state, it generates a signal indicating that the clutch 6 is in a disengaged state ("Clutch disengaged" in FIG. 3). By referring to these signals, it is possible to determine the current state of the clutch 6.

The operation of the clutch state detection device 110 will be explained below with reference to the start-up operation shown in Figure 4 and the state during deceleration after the clutch is disengaged shown in Figure 6.

First, in the start-up operation shown in FIG. 4, the rotational speed R2 of the steam turbine 4 gradually increases, so that the rotational speed difference between the rotational speed R1 of the gas turbine 2 and the rotational speed R2 of the steam turbine 4 becomes smaller. At this time, when the speed difference detection unit 111 detects that the rotational speed difference is equal to or less than the first predetermined value, the clutch state detection device 110 inputs a "GT/ST rotational speed difference small" signal indicating that the rotational speed difference is small from the speed difference detection unit 111 to the determination unit 113.

When the rotational speed of the steam turbine 4 reaches the rated rotational speed, the clutch 6 is engaged and the rotational power of the steam turbine 4 is transmitted to the generator 3, thereby increasing the power generation output. As a result, the power generation output detection unit 112 detects that the difference in the power generation output of the generator at two different points in time is equal to or greater than a predetermined output value, and inputs a "generator output increase" signal indicating that the power generation output has increased to the determination unit 103.

As described above, when the "GT/ST rotation speed difference small" signal and the "generator output increase" signal are input to the judgment unit 103 (more specifically, the logical product gate unit 114), a logical product is established in the logical product gate unit 114, and the clutch state detection device 110 inputs the input signal In1 from the logical product gate unit 114 to the holding circuit unit 116. At this time, the holding circuit unit 116 is set and generates a signal indicating that the clutch 6 is in an engaged state. As a result, the clutch state detection device 110 determines that the current state of the clutch 6 is in an engaged state, and more specifically, determines that the clutch 6 is in an engaged state at the time of startup.

On the other hand, when the speed is reduced after the clutch is disengaged as shown in FIG. 6, the steam turbine 4 is first stopped after the clutch is disengaged, and then the gas turbine 2 is stopped, and the rotation speed R1 of the gas turbine 2 and the rotation speed R2 of the steam turbine 4 gradually decrease. Then, even though the gas turbine 2 is stopped later, the rotation speed R1 of the gas turbine 2 catches up with the reduced rotation speed R2 of the steam turbine 4.

At this time, in the clutch state detection device 110, after the steam turbine 4 is stopped and before the gas turbine 2 is stopped, the speed difference detection unit 111 detects that the rotational speed difference between the rotational speed R1 of the gas turbine 2 and the rotational speed R2 of the steam turbine 4 is equal to or greater than the second predetermined value. Then, a "GT/ST rotational speed difference large" signal indicating that the rotational speed difference is large is input from the speed difference detection unit 111 to the determination unit 113. As a result, in the clutch state detection device 110, the holding circuit unit 116 in the determination unit 113 is reset, a signal indicating that the clutch 6 is in a disengaged state is generated, and the clutch state detection device 110 determines that the current state of the clutch 6 is in a disengaged state.

On the other hand, when the rotation speed R1 of the gas turbine 2 subsequently catches up with the reduced rotation speed R2 of the steam turbine 4, the speed difference detection unit 111 detects that the rotation speed difference between the rotation speed R1 of the gas turbine 2 and the rotation speed R2 of the steam turbine 4 is equal to or less than the first predetermined value, and a "GT/ST rotation speed difference small" signal indicating that the rotation speed difference is small is input from the speed difference detection unit 111 to the determination unit 113 (more specifically, the logical AND gate unit 114).

However, when the rotation speed R1 of the gas turbine 2 decreases, the gas turbine 2 is disconnected, and the power generation output is 0. Therefore, in the clutch state detection device 110, the power generation output detection unit 112 does not input a signal of "generator output increase" to the judgment unit 103 (more specifically, the logical product gate unit 114). Therefore, the logical product is not established in the logical product gate unit 114, and the input signal In1 is not input from the logical product gate unit 114 to the holding circuit unit 106. Therefore, the reset state of the holding circuit unit 106 is maintained, and it is not detected that the clutch 6 is in an engaged state. In this embodiment, when the speed is reduced after the clutch is disengaged, the steam turbine 4 is stopped, and then the generator 3 is disconnected from the power grid, and then the gas turbine 2 is stopped.

The clutch state detection device 110 according to the second embodiment described above determines whether the clutch 6 is in an engaged state, taking into consideration not only whether the rotational speed difference between the rotational speed R1 of the gas turbine 2 and the rotational speed R2 of the steam turbine 4 has become small, but also whether the power generation output has increased at the level at which the clutch 6 transitioned from the disengaged state to the engaged state. This allows the state of the clutch 6 to be detected in a desired manner, as in the first embodiment. That is, specifically, the engagement state of the clutch 6 can be detected in a manner that detects only the engagement state of the clutch 6 at start-up and excludes detection of the engagement state of the clutch 6 during deceleration. In particular, in this embodiment, whether the power generation output has increased at the level at which the clutch 6 transitioned from the disengaged state to the engaged state is determined from the actual power generation output MW, which is advantageous in terms of the reliability of the determination.

Although the embodiment has been described above, the above embodiment is presented as an example and is not intended to limit the scope of the invention. This new embodiment can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. Such embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

1... Single-shaft combined cycle power plant, 2... Gas turbine, 3... Generator, 4... Steam turbine, 5... Rotating shaft, 6... Clutch, 7... Fuel control valve, 8... High-pressure steam control valve, 9... Reheat steam control valve, 10... High-pressure turbine, 11... Intermediate-pressure turbine, 12... Low-pressure turbine, 13... First steam pressure sensor, 14... Second steam pressure sensor, 15... First speed sensor, 16... Second speed sensor, 100, 110... Clutch state detection device, 101, 111... Speed difference detection unit, 102... Steam pressure detection unit, 103, 113... Judgment unit, 104, 114... Logical AND gate unit, 105... Logical OR gate unit, 106, 116... Holding circuit unit, 112... Power generation output detection unit

Claims (10)

A clutch state detection device for a single-shaft combined cycle power plant in which a gas turbine, a generator, and a steam turbine are connected by a common rotating shaft, and power transmission between the generator and the steam turbine is switched between a connected state and a disconnected state by a clutch,
a speed difference detection unit that detects whether a rotational speed difference between the rotational speed of the gas turbine and the rotational speed of the steam turbine is equal to or smaller than a predetermined value;
a steam pressure detection unit that detects whether an inlet steam pressure of the steam turbine is equal to or higher than a predetermined pressure;
and a determination unit that determines that the clutch is in an engaged state when the speed difference detection unit detects that the rotational speed difference is equal to or less than the predetermined value and the steam pressure detection unit detects that the inlet steam pressure is equal to or more than the predetermined pressure, thereby not determining that the clutch is in an engaged state when the rotational speed difference is equal to or less than the predetermined value during slowing down of the gas turbine or the steam turbine. the speed difference detection unit is configured to detect whether the rotation speed difference is equal to or greater than another predetermined value that is greater than the predetermined value,
2. The clutch state detection device for a single-shaft combined cycle power plant according to claim 1, wherein the determination unit determines that the clutch is in a disengaged state when the speed difference detection unit detects that the rotational speed difference is equal to or greater than the other predetermined value. The clutch state detection device for a single-shaft combined cycle power plant according to claim 1 or 2, wherein the determination unit determines that the clutch is in a disengaged state when the speed difference detection unit does not detect that the rotational speed difference is equal to or less than a predetermined value, and/or when the steam pressure detection unit does not detect that the inlet steam pressure is equal to or greater than the predetermined pressure. The steam turbine has a high-pressure turbine rotated by high-pressure steam generated in a heat recovery boiler by exhaust gas from the gas turbine, and another turbine rotated by steam having a pressure lower than that of the high-pressure steam,
4. The clutch state detection device for a single-shaft combined cycle power plant according to claim 1, wherein the steam pressure detection unit determines that the inlet steam pressure of the steam turbine is equal to or higher than the specified pressure when it detects that the inlet steam pressure of the other turbine is equal to or higher than a first specified pressure as the specified pressure, or when it detects that the inlet steam pressure of the other turbine is equal to or higher than a first specified pressure as the specified pressure and the inlet steam pressure of the high-pressure turbine is equal to or higher than a second specified pressure as the specified pressure. The clutch state detection device for a single-shaft combined cycle power plant according to claim 4, wherein the other turbine is an intermediate pressure turbine that is rotated by reheated steam that heats the steam discharged by the high pressure turbine. A clutch state detection device for a single-shaft combined cycle power plant in which a gas turbine, a generator, and a steam turbine are connected by a common rotating shaft, and power transmission between the generator and the steam turbine is switched between a connected state and a disconnected state by a clutch,
a speed difference detection unit that detects whether a rotational speed difference between the rotational speed of the gas turbine and the rotational speed of the steam turbine is equal to or smaller than a predetermined value;
a power generation output detection unit for detecting whether or not a power generation output of the generator has increased;
and a determination unit that determines that the clutch is in an engaged state when the speed difference detection unit detects that the rotational speed difference is equal to or less than a predetermined value and the power generation output detection unit detects that the power generation output has increased, and thereby does not determine a state in which the rotational speed difference is equal to or less than the predetermined value during slowing down of the gas turbine or the steam turbine, as the clutch being in an engaged state . the speed difference detection unit is configured to detect whether the rotation speed difference is equal to or greater than another predetermined value that is greater than the predetermined value,
7. The clutch state detection device for a single-shaft combined cycle power plant according to claim 6, wherein the determination unit determines that the clutch is in a disengaged state when the speed difference detection unit detects that the rotational speed difference is equal to or greater than the other predetermined value. The clutch state detection device for a single-shaft combined cycle power plant according to claim 6 or 7, wherein the power generation output detection unit calculates the difference between the power generation outputs of the generator at two different points in time, and determines that the power generation output has increased when the difference is equal to or greater than a predetermined output value. A clutch state detection method for a single-shaft combined cycle power plant in which a gas turbine, a generator, and a steam turbine are connected by a common rotating shaft, and power transmission between the generator and the steam turbine is switched between a connected state and a disconnected state by a clutch, comprising:
a speed difference detection step of detecting whether a rotational speed difference between the rotational speed of the gas turbine and the rotational speed of the steam turbine is equal to or smaller than a predetermined value;
a steam pressure detection step of detecting whether or not an inlet steam pressure of the steam turbine is equal to or higher than a predetermined pressure;
a determination step of determining that the clutch is in an engaged state when the speed difference detection step detects that the rotational speed difference is equal to or less than the predetermined value and the steam pressure detection step detects that the inlet steam pressure is equal to or more than the predetermined pressure, thereby not determining that the clutch is in an engaged state when the rotational speed difference is equal to or less than the predetermined value during slowing down of the gas turbine or the steam turbine. A clutch state detection method for a single-shaft combined cycle power plant in which a gas turbine, a generator, and a steam turbine are connected by a common rotating shaft, and power transmission between the generator and the steam turbine is switched between a connected state and a disconnected state by a clutch, comprising:
a speed difference detection step of detecting whether a rotational speed difference between the rotational speed of the gas turbine and the rotational speed of the steam turbine is equal to or smaller than a predetermined value;
a power generation output detection step of detecting whether or not the power generation output of the generator has increased;
a determination step of determining that the clutch is in an engaged state when the speed difference detection step detects that the rotational speed difference is equal to or less than a predetermined value and when the power generation output detection step detects that the power generation output has increased , thereby not determining that the clutch is in an engaged state when the rotational speed difference is equal to or less than the predetermined value during slowing down of the gas turbine or the steam turbine .

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