Turbine rotation speed control system

Abstract

This turbine rotation speed control system is for controlling the rotation speed of a turbine of a turbine generator and comprises a control device which is configured to control the valve opening degree of an input control valve for regulating the amount of input energy of the turbine. The control device is configured to perform proportional control of the valve opening degree of the input control valve, while the turbine generator is not connected to an external power system, on the basis of a deviation between a target rotation speed and an actually measured rotation speed of the turbine. The control device is also configured to be capable of executing a target rotation speed control mode, during execution of the proportional control, for reducing the target rotation speed when the actually measured rotation speed of the turbine exceeds a first threshold value, and for increasing the target rotation speed when the actually measured rotation speed of the turbine falls below a second threshold value.

Description

Turbine Rotation Speed Control System

[0001] This disclosure relates to a turbine rotation speed control system. This application claims priority based on Japanese Patent Application No. 2025-008343 filed with the Japan Patent Office on January 21, 2025, and incorporates its content herein by reference.

[0002] Patent Document 1 describes controlling a turbine so as to maintain a constant rotation speed of the turbine in a state where a gas turbine generator is not connected to an external power grid (a state where a circuit breaker is open) in a power generation plant including the gas turbine generator.

[0003] Japanese Patent Application Laid-Open No. 2001-197789

[0004] By the way, as a method of controlling the rotation speed of a turbine in a state where a turbine generator is not connected to an external power grid, a method of controlling the valve opening degree of an input amount adjustment valve (for example, a fuel supply valve in the case of a gas turbine) for adjusting the input energy to the turbine based on the deviation between the target rotation speed and the measured rotation speed of the turbine can be considered.

[0005] However, in this method, even if the target rotation speed of the turbine is set based on the assumed load of the turbine generator (the total of the assumed loads of auxiliary machines in the power generation plant, etc.), when the actual load of the turbine generator is different from the assumed load, or when the energy amount per unit amount of the energy medium input to the turbine is different from the assumed amount (for example, in the case of a gas turbine, when the calorific value of the fuel is different from the assumed calorific value), etc., the rotation speed of the turbine may fluctuate and deviate significantly from the target rotation speed. For example, as shown in FIG. 6, when the rotation speed of the turbine becomes an excessively high value or an excessively low value compared to the rated rotation speed, there is a risk that an overcurrent trip of the auxiliary machine will occur, or the supply voltage of the auxiliary machine will become excessively low. Also, when attempting to connect (re-arrange) the turbine generator to an external power grid in a state where the rotation speed of the turbine is lower than the rated rotation speed, there is a possibility that a reverse current trip (a trip that automatically occurs when a current flows from the power grid side into the generator side) will occur in the turbine generator.

[0006] In view of the circumstances described above, at least one embodiment of the present disclosure aims to provide a turbine speed control system that can suppress the turbine speed from deviating significantly from a desired speed when the turbine generator is not connected to an external power grid.

[0007] To achieve the above objective, a turbine speed control system according to at least one embodiment of the present disclosure is a turbine speed control system for controlling the rotational speed of a turbine of a turbine generator, comprising a control device configured to control the valve opening of an input quantity control valve for adjusting the amount of input energy to the turbine, wherein the control device is configured to perform proportional control of the valve opening of the input quantity control valve based on the deviation between the target rotational speed and the actual rotational speed of the turbine when the turbine generator is not connected to an external power system, and the control device is configured to execute a target rotational speed adjustment mode during the execution of the proportional control, which decreases the target rotational speed when the actual rotational speed of the turbine exceeds a first threshold and increases the target rotational speed when the actual rotational speed of the turbine falls below a second threshold.

[0008] According to at least one embodiment of the present disclosure, a turbine speed control system is provided that can suppress the turbine speed from deviating significantly from a desired speed when the turbine generator is not connected to an external power grid.

[0009] This figure shows the schematic configuration of a power plant 2 according to one embodiment of the present disclosure. This is a block diagram showing an example of the hardware configuration of the control device 40. This figure shows an example of the control flow of the control device 40 when transitioning from a state where the circuit breaker 10 is closed (a state in which the gas turbine generator 4 is connected to the external power system 30) to a state where the circuit breaker 10 is open (a state in which the gas turbine generator 4 is disconnected from the external power system 30). This is a flowchart for explaining the target rotational speed adjustment mode. This figure shows an example of the time change of the target rotational speed of the turbine 24 during the period when transitioning from grid-connected operation to in-house standalone operation for the turbine rotational speed control system 12. This figure shows an example of the time change of the target rotational speed of the turbine 24 during the period when transitioning from grid-connected operation to in-house standalone operation for the comparative form. This figure shows the schematic configuration of a power plant 2 according to another embodiment. This figure shows an example of the control flow of the control device 40 when transitioning from a state where the load circuit breaker 34 is closed (a state in which the gas turbine generator 4 is under load) to a state where the load circuit breaker 34 is open (a state in which the load on the gas turbine generator 4 is cut off).

[0010] Hereinafter, several embodiments of this disclosure will be described with reference to the attached drawings. However, the dimensions, materials, shapes, relative arrangements, etc., of the components described as embodiments or shown in the drawings are not intended to limit the scope of the invention, but are merely illustrative examples. For example, expressions describing relative or absolute arrangements such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" should not only strictly represent such arrangements, but also represent states where there is a tolerance, or a relative displacement of an angle or distance sufficient to achieve the same function. For example, expressions describing things as being in an equal state such as "identical," "equal," and "homogeneous" should not only strictly represent states of equality, but also represent states where there is a tolerance, or a difference sufficient to achieve the same function. For example, expressions describing shapes such as a square shape or a cylindrical shape should not only represent geometrically precise shapes such as square shapes or cylindrical shapes, but also represent shapes including concave and concave parts, chamfered parts, etc., to the extent that the same effect can be achieved. On the other hand, expressions such as "to possess," "to be equipped with," "to have," "to include," or "to have" a single component are not exclusive expressions that exclude the existence of other components.

[0011] Figure 1 is a diagram showing the schematic configuration of a power plant 2 according to one embodiment. The power plant 2 shown in Figure 1 includes a gas turbine generator 4, a plurality of auxiliary machines 6, an in-house power system 8, a circuit breaker 10, and a turbine speed control system 12, etc.

[0012] The gas turbine generator 4 includes a gas turbine 14 and a generator 16. The gas turbine 14 includes a compressor 20 that compresses air to produce compressed air, a combustor 22 that burns fuel gas using the compressed air produced by the compressor 20 to produce combustion gas, and a turbine 24 that rotates using the combustion gas produced by the combustor 22. In the illustrated exemplary embodiment, the generator 16 is provided with a wattmeter 31 for measuring the actual load of the gas turbine generator 4.

[0013] A fuel supply line 23 is connected to the combustor 22, and fuel gas is supplied to the combustor 22 from the fuel supply line 23. The fuel supply line 23 is equipped with a fuel supply valve 25 for adjusting the amount of fuel gas supplied to the combustor 22.

[0014] The compressor 20 and the turbine 24 are connected via a shaft 26 and rotate together. The turbine 24 and the generator 16 are also connected via a shaft 28, and the rotational energy of the turbine 24 is transmitted to the generator 16, causing the generator 16 to produce electricity. The following description will focus on the case where the generator 16 is a synchronous generator.

[0015] The multiple auxiliary devices 6 are equipment that assists in the operation of the gas turbine generator 4, and include, for example, a lubricating oil pump for supplying lubricating oil to the turbine 24 and generator 16, a cooling device for cooling the turbine 24 and generator 16, and a fuel pump for supplying fuel to the combustor 22. The multiple auxiliary devices 6 are connected to the generator 16 via the plant's power system 8, and part or all of the electricity generated by the generator 16 is supplied to the multiple auxiliary devices 6 via the plant's power system 8 to drive the multiple auxiliary devices 6.

[0016] The internal power system 8 is connected to the external power system 30 via a circuit breaker 10. The internal power system 8 is a power system for supplying power to equipment used inside the power plant 2, and is configured to supply power to multiple auxiliary machines 6, as well as, for example, lighting and air conditioning inside the power plant 2. The external power system 30 is a system for supplying power generated at the power plant 2 to the outside of the power plant 2, and is, for example, the power transmission network of a power company.

[0017] The circuit breaker 10 is configured to switch between a state in which the in-house power system 8 and the external power system 30 are connected, and a state in which the in-house power system 8 and the external power system 30 are disconnected.

[0018] The turbine speed control system 12 is a system for controlling the rotational speed of the turbine 24 of the gas turbine generator 4, and comprises a fuel supply valve 25, a tachometer 29 capable of measuring the rotational speed of the turbine 24, and a control device 40 capable of controlling the valve opening of the fuel supply valve 25. The details of the control device 40 will be described below.

[0019] Figure 2 is a block diagram showing an example of the hardware configuration of the control device 40. The control device 40 is configured using a computer that includes, for example, a processor 91, RAM (Random Access Memory) 92, ROM (Read Only Memory) 93, HDD (Hard Disk Drive) 94, input I / F 96, and output I / F 98, all of which are connected to each other via a bus 95. The control device 40 is also configured by the computer executing programs that realize each of the functions of the control device 40. The functions of each part of the control device 40 described below are realized, for example, by loading a program held in ROM 93 into RAM 92 and executing it with the processor 91, as well as by reading and writing data in RAM 92 and ROM 93. The hardware constituting the control device 40 may be concentrated in one location or distributed across multiple locations.

[0020] Figure 3 shows an example of the control flow of the control device 40 when the operating state of the gas turbine generator 4 is changed from grid-connected operation to in-house isolated operation. Here, grid-connected operation means operating the gas turbine generator 4 with the circuit breaker 10 closed and the gas turbine generator 4 connected to the external power system 30. In grid-connected operation, a portion of the electricity generated by the gas turbine generator 4 is supplied to the equipment inside the power plant 2 connected to the in-house power system 8 (multiple auxiliary machines 6, etc.), and the remainder is supplied to the external power system 30. In-house isolated operation means operating the gas turbine generator 4 with the circuit breaker 10 open and the gas turbine generator 4 not connected to the external power system 30 (i.e., the gas turbine generator 4 is disconnected from the external power system 30). In in-house isolated operation, the electricity generated by the gas turbine generator 4 is not supplied to the external power system 30, but only to the equipment inside the power plant 2 connected to the in-house power system 8 (multiple auxiliary machines 6, etc.).

[0021] As shown in Figure 3, in S101, the control device 40 operates the gas turbine generator 4 in grid connection mode. In grid connection mode, the control device 40 controls the valve opening of the fuel supply valve 25 based on, for example, the load requirement of the gas turbine generator 4. In this case, the control device 40 may, for example, perform PI control of the valve opening of the fuel supply valve 25 based on the deviation between the load requirement of the gas turbine generator 4 and the actual load of the gas turbine generator 4 measured by the wattmeter 31, thereby causing the actual load of the gas turbine generator 4 to follow the load requirement. In grid connection mode in S101, since the generator 16 is a synchronous generator, the rotational speed of the generator 16, i.e., the rotational speed of the turbine 24, is constrained by the frequency of the external power system 30 and remains constant.

[0022] In S102, the control device 40 determines whether to maintain grid-connected operation or switch to stationary operation based on a signal indicating the open / closed state of the circuit breaker 10. If the control device 40 receives a circuit breaker open signal indicating the open state of the circuit breaker 10, it decides to switch to stationary operation and proceeds to S103. If the control device 40 receives a circuit breaker closed signal indicating the closed state of the circuit breaker 10, it returns to S101 and continues grid-connected operation.

[0023] In S103, the control device 40 switches from grid-connected operation to in-house isolated operation and starts proportional control of the valve opening of the fuel supply valve 25, as described below. The control device 40 calculates the deviation ΔN between the target rotational speed Ns of the turbine 24 and the actual rotational speed Nm of the turbine 24 measured by the tachometer 29, and performs proportional control (P control) of the valve opening of the fuel supply valve 25 based on the deviation ΔN. In the above proportional control, the target rotational speed Ns is a set value, and the control device 40 may control the valve opening of the fuel supply valve 25 based on, for example, the following equation (a): u = Kp × ΔN ... (a)

[0024] Here, u is the control output from the control device 40 to the fuel supply valve 25, and may be, for example, the amount of change in the valve opening of the fuel supply valve 25, or the valve opening of the fuel supply valve 25. Kp is the proportional gain, and ΔN is the deviation between the target rotational speed Ns and the actual rotational speed Nm (i.e., the value obtained by subtracting Nm from Ns). Note that in S103, unlike S105 which will be described later, the above proportional control is performed with the target rotational speed Ns fixed (while maintaining the target rotational speed Ns as a fixed value that does not depend on the actual rotational speed Nm). Furthermore, in the following description, unless otherwise specified, "proportional control" means proportional control of the valve opening of the fuel supply valve 25 based on the deviation ΔN between the target rotational speed Ns and the actual rotational speed Nm.

[0025] In S104, the control device 40 determines whether a predetermined time has elapsed since receiving the circuit breaker open signal indicating the open state of the circuit breaker 10. That is, in S104, the control device 40 determines whether a predetermined time has elapsed since the connection between the gas turbine generator 4 and the external power system 30 was disconnected (or, to put it another way, whether a predetermined time has elapsed since the switch from grid-connected operation to stationary operation within the plant). The predetermined time in S104 is a time set in advance, taking into consideration that the rotational speed of the turbine 24 becomes unstable immediately after the circuit breaker 10 opens, and is the time required from the time the circuit breaker 10 opens until the rotational speed of the turbine 24 stabilizes to a level that does not cause control problems. This predetermined time is a predetermined time, such as 60 seconds, and may be, for example, 10 seconds or more and 120 seconds or 30 seconds or more and 90 seconds or less.

[0026] In S104, if it is determined that a predetermined time has not elapsed since receiving the circuit breaker open signal indicating the open state of the circuit breaker 10 (i.e., if it is determined that a predetermined time has not elapsed since the connection between the gas turbine generator 4 and the external power system 30 was disconnected, or in other words, if it is determined that a predetermined time has not elapsed since the switch from grid-connected operation to in-house standalone operation), the system returns to S103 and continues the proportional control described above, fixing the target rotational speed Ns.

[0027] In S104, if it is determined that a predetermined time has elapsed since receiving the circuit breaker open signal indicating the open state of the circuit breaker 10 (i.e., if it is determined that a predetermined time has elapsed since the connection between the gas turbine generator 4 and the external power system 30 was disconnected, or in other words, if it is determined that a predetermined time has elapsed since the system switched from grid-connected operation to in-house standalone operation), the process proceeds to S105.

[0028] In S105, the control device 40 executes the target rotational speed adjustment mode while continuing the proportional control described above that was started in S103. Details of the target rotational speed adjustment mode will be described later.

[0029] In S106, a decision is made based on a signal indicating the open / closed state of the circuit breaker 10 to determine whether to continue in-house operation or switch to grid-connected operation. If the control device 40 receives a circuit breaker open signal in S106 indicating that the circuit breaker 10 is open, in-house operation is continued, and the process returns to S105 to continue the target rotation speed adjustment mode described later. If the control device 40 receives a circuit breaker closed signal in S106 indicating that the circuit breaker 10 is closed, the process switches to grid-connected operation. In this case, the process may return to S101 again.

[0030] Figure 4 is a flowchart illustrating the target rotational speed adjustment mode of S105 in Figure 3. As will be described in detail below, the target rotational speed adjustment mode is a mode in which the target rotational speed Ns used in the proportional control of the valve opening of the fuel supply valve 25 is adjusted based on the actual rotational speed Nm of the turbine 24 measured by the tachometer 29.

[0031] First, in S201, the control device 40 determines whether the measured rotational speed Nm of the turbine 24, as measured by the rotational speed meter 29, exceeds the first threshold N1.

[0032] In S201, if the control device 40 determines that the measured rotational speed Nm of the turbine 24, as measured by the rotational speed meter 29, exceeds the first threshold N1, then in S202, the value obtained by subtracting the first predetermined value n1 from the currently set target rotational speed Ns (= Ns - n1) is set (updated) as the new target rotational speed Ns, and the process proceeds to S206.

[0033] On the other hand, in S201, if the control device 40 determines that the measured rotational speed Nm of the turbine 24 measured by the tachometer 29 does not exceed the first threshold N1, then in S203, the control device 40 determines whether or not the measured rotational speed Nm of the turbine 24 measured by the tachometer 29 is below the second threshold N2.

[0034] Furthermore, the first threshold N1 is greater than the second threshold N2, and each of the first threshold N1 and the second threshold N2 is greater than the rated rotational speed Nr of the turbine 24. Also, the second threshold N2 may satisfy, for example, 1.0003Nr < N2 < 1.013Nr, or 1.001Nr < N2 < 1.007Nr. Also, the difference between the first threshold N1 and the second threshold N2 may satisfy, for example, 0.0005Nr < N1 - N2 < 0.01Nr, or 0.001Nr < N1 - N2 < 0.005Nr.

[0035] In S203, if the control device 40 determines that the measured rotational speed Nm of the turbine 24, as measured by the rotational speed meter 29, is below the second threshold N2, then in S204, the control device 40 sets (updates) the value obtained by adding the second predetermined value n2 to the currently set target rotational speed Ns (= Ns + n2) as the new target rotational speed Ns, and proceeds to S206.

[0036] The second predetermined value n2 may be the same value as the first predetermined value n1. Also, the first predetermined value n1 may satisfy, for example, 0.0002Nr < n1 < 0.003Nr, or 0.0003Nr < n1 < 0.0017Nr. Also, the second predetermined value n2 may satisfy, for example, 0.0002Nr < n2 < 0.003Nr, or 0.0003Nr < n2 < 0.0017Nr.

[0037] Furthermore, in S203, if the control device 40 determines that the measured rotational speed Nm of the turbine 24, as measured by the tachometer 29, is not below the second threshold N2, then in S205, the currently set target rotational speed Ns is set (maintained) as the new target rotational speed Ns, and the process proceeds to S206.

[0038] In S206, proportional control (P control) of the valve opening of the fuel supply valve 25 is performed based on the deviation between the target rotational speed Ns newly set in S202, S204, or S205 and the actual rotational speed Nm of the turbine 24 measured by the tachometer 29.

[0039] As described above, in the target rotational speed adjustment mode shown in Figure 4, the control device 40, while performing proportional control of the valve opening of the fuel supply valve 25, decreases the target rotational speed Ns when the measured rotational speed Nm of the turbine 24 exceeds the first threshold N1, and increases the target rotational speed Ns when the measured rotational speed Nm of the turbine 24 falls below the second threshold N2. In this target rotational speed adjustment mode, the target rotational speed Ns is the target rotational speed for proportional control, and the true target rotational speed that the rotational speed Nm of the turbine 24 follows is the value obtained by dividing the sum of N1 and N2 by 2, i.e., (N1 + N2) / 2.

[0040] According to the above target rotational speed adjustment mode, the steady-state deviation of the turbine 24's rotational speed can be reduced compared to general proportional control that uses a fixed value as the target rotational speed of the turbine 24. For example, even if the actual load of the gas turbine generator 4 differs from the assumed load, or if the calorific value of the fuel supplied to the combustor 22 differs from the assumed calorific value, as shown in Figure 5, the rotational speed of the turbine 24 can be quickly returned to a desired range (the range between the first threshold N1 and the second threshold N2), and the rotational speed of the turbine 24 can be prevented from deviating significantly from the desired value (i.e., the value obtained by dividing the sum of N1 and N2 by 2). Therefore, the supply voltage of the auxiliary equipment 6 can be stabilized, and the occurrence of overcurrent trips of the auxiliary equipment 6 can be suppressed. Furthermore, by setting the second threshold N2, which is the lower limit of the above range, to a value greater than the rated rotational speed Nr of the turbine 24, the risk of reverse power trips occurring when the gas turbine generator 4 is reconnected to the external power system 30 can be reduced.

[0041] Figure 7 is a diagram showing the schematic configuration of a power plant 2 according to another embodiment. In the power plant 2 according to the embodiment shown in Figure 7, reference numerals common to the components of the power plant 2 shown in Figure 1 indicate the same components as those shown in the power plant 2 shown in Figure 1, unless otherwise specified, and their explanation is omitted.

[0042] In some embodiments, as shown in Figure 7, for example, the power plant 2 is equipped with a load circuit breaker 34. The load circuit breaker 34 is installed between the in-house power system 8 and the generator 16. When the load circuit breaker 34 is open, the generator 16 and the in-house power system 8 are electrically disconnected, and the load on the gas turbine generator 4 is cut off. When the load circuit breaker 34 is closed, the generator 16 and the in-house power system 8 are electrically connected, and the load is applied to the gas turbine generator 4. In other words, the load circuit breaker 34 is configured to switch between a state in which the generator 16 and the in-house power system 8 are electrically connected and a state in which the generator 16 and the in-house power system 8 are electrically disconnected.

[0043] FIG. 8 is a diagram showing an example of a control flow of the control device 40 when shifting from a state where the load breaker 34 is closed (a state where a load is applied to the gas turbine generator 4) to a state where the load breaker 34 is opened (a state where the load of the gas turbine generator 4 is interrupted) in the power generation plant 2 shown in FIG. 7.

[0044] In S301, when the load breaker 34 is opened and the load of the gas turbine generator 4 is interrupted, the control device 40 receives a load breaker open signal indicating that the state of the load breaker 34 has switched from the closed state to the open state from the load breaker 34.

[0045] In S302, the control device 40 starts proportional control of the valve opening degree of the fuel supply valve 25. The control device 40 calculates a deviation ΔN between the target rotational speed Ns of the turbine 24 and the actually measured rotational speed Nm of the turbine 24 measured by the rotational speed meter 29, and performs proportional control (P control) of the valve opening degree of the fuel supply valve 25 based on the above formula (a). In S302, unlike S304 described later, the proportional control is executed while fixing the target rotational speed Ns (while maintaining the target rotational speed Ns at a fixed value independent of the actually measured rotational speed Nm). In the following description as well, "proportional control" means proportional control of the valve opening degree of the fuel supply valve 25 based on the deviation ΔN between the target rotational speed Ns and the actually measured rotational speed Nm, unless otherwise specified.

[0046] In S303, the control device 40 determines whether or not a predetermined time (first predetermined time) has elapsed since receiving the load breaker open signal. That is, in S303, the control device 40 determines whether or not a predetermined time has elapsed since the load of the gas turbine generator 4 was interrupted (or rather, whether or not a predetermined time has elapsed since the gas turbine generator 4 was electrically disconnected from the in-house power system 8). The predetermined time in S303 is a time set in advance in consideration of the fact that the rotational speed of the turbine 24 becomes unstable immediately after the load breaker 34 is opened, and is the time required for the rotational speed of the turbine 24 to become stable to such an extent that there are no control problems after the load breaker 34 is opened. This predetermined time is, for example, a predetermined time such as 30 seconds, and may be, for example, a time of 10 seconds or more and 80 seconds or less, or a time of 15 seconds or more and 60 seconds or less.

[0047] In S303, when it is determined that a predetermined time has not elapsed since the reception of the load breaker opening signal (that is, when it is determined that a predetermined time has not elapsed since the load of the gas turbine generator 4 was interrupted), the process returns to S302 and the target rotational speed Ns is continuously fixed to continue the proportional control described above.

[0048] In S303, when it is determined that a predetermined time has elapsed since the reception of the load breaker opening signal, the process proceeds to S304.

[0049] In S304, while continuing the proportional control started in S302, the control device 40 starts the target rotational speed adjustment mode. Since this target rotational speed adjustment mode is the same as the target rotational speed adjustment mode described using FIG. 4 (the mode in which the target rotational speed Ns is decreased when the measured rotational speed Nm of the turbine 24 exceeds the first threshold value N1, and the target rotational speed Ns is increased when the measured rotational speed Nm of the turbine 24 falls below the second threshold value N2), a detailed description of the target rotational speed adjustment mode is omitted here.

[0050] In S305, the control device 40 determines whether or not a predetermined time (second predetermined time) has elapsed since the start of the target rotational speed adjustment mode. The predetermined time in S305 may be a time preset in consideration of the time until the rotational speed of the turbine 24 stabilizes within a desired range (that is, the range between the above N1 and the above N2) by the target rotational speed adjustment mode. This predetermined time is, for example, a predetermined time such as 150 seconds, and may be, for example, a time of 10 seconds or more and 300 seconds or less, or may be a time of 60 seconds or more and 200 seconds or less.

[0051] In S305, when it is determined that a predetermined time has not elapsed since the start of the target rotational speed adjustment mode, the process returns to S304 to continue the target rotational speed adjustment mode. In S305, when it is determined that a predetermined time has elapsed since the start of the target rotational speed adjustment mode, the target rotational speed adjustment mode is terminated in S306. After terminating the target rotational speed adjustment mode in S306, the proportional control may be continued while fixing the target rotational speed Ns (while maintaining the target rotational speed Ns at a fixed value independent of the measured rotational speed Nm).

[0052] This disclosure is not limited to the embodiments described above, but also includes modified forms of the embodiments described above, as well as forms that combine these forms as appropriate.

[0053] For example, the above-described embodiment illustrates a turbine speed control system for controlling the rotational speed of a gas turbine generator. However, the turbine speed control system of this disclosure is also applicable to a turbine speed control system for controlling the rotational speed of a steam turbine in a steam turbine generator. In this case, the input volt adjustment valve for adjusting the amount of input energy to the turbine (the amount of energy input to the turbine) is a steam control valve for adjusting the flow rate of steam supplied to the steam turbine, and the control flow described using Figures 3 and 4 or the control flow described using Figures 8 and 4 can be applied to the control of the valve opening of the steam control valve.

[0054] The contents described in each of the above embodiments can be understood, for example, as follows:

[0055] [1] A turbine speed control system according to at least one embodiment of the present disclosure (for example, the turbine speed control system 12 described above) is a turbine speed control system for controlling the rotational speed of a turbine (for example, the turbine 24 described above) of a turbine generator (for example, the gas turbine generator 4 described above), comprising a control device (for example, the control device 40 described above) configured to control the valve opening of an input quantity control valve (for example, the fuel supply valve 25 described above) for adjusting the amount of input energy to the turbine, wherein the control device is configured to perform proportional control of the valve opening of the input quantity control valve based on the deviation (for example, the deviation ΔN described above) between a target rotational speed (for example, the target rotational speed Ns described above) and an actual rotational speed (for example, the actual rotational speed Nm described above) of the turbine when the turbine generator is not connected to an external power system (for example, the external power system 30 described above), The control device is configured to execute a target rotation speed adjustment mode during the execution of proportional control, in which the measured rotation speed of the turbine exceeds a first threshold (for example, the first threshold N1 described above), and the target rotation speed increases when the measured rotation speed of the turbine falls below a second threshold (for example, the second threshold N2 described above).

[0056] According to the turbine rotation speed control system described in [1] above, in the target rotation speed adjustment mode, the target rotation speed is reduced when the measured rotation speed of the turbine exceeds the first threshold, and the target rotation speed is increased when the measured rotation speed of the turbine falls below the second threshold. This makes it possible to reduce the steady-state deviation of the turbine rotation speed compared to general proportional control that uses a fixed value as the target rotation speed of the turbine. For example, when the actual load of the turbine generator differs from the assumed load, or when the amount of energy contained per unit amount of the energy medium input to the turbine differs from the assumed amount, even if the rotation speed of the turbine deviates from the desired range (the range between the first threshold and the second threshold), it is possible to quickly return to the desired range and suppress large deviations of the turbine rotation speed from the desired value (i.e., the value obtained by dividing the sum of the first threshold and the second threshold by 2).

[0057] [2] In some embodiments, in the turbine speed control system described in [1] above, the control device is configured to execute the target speed adjustment mode after a predetermined time has elapsed since the connection between the turbine generator and the external power system was disconnected.

[0058] Immediately after disconnecting the turbine generator from the external power system, the turbine's rotational speed becomes unstable. Therefore, if the target rotational speed adjustment mode is executed within a predetermined time after disconnecting the turbine generator from the external power system, it becomes difficult to control the turbine's rotational speed. For this reason, as described in [2] above, by executing the target rotational speed adjustment mode after a predetermined time has elapsed since disconnecting the turbine generator from the external power system, it is easy to suppress the turbine's rotational speed from deviating significantly from the desired value (i.e., the value obtained by dividing the sum of the first threshold and the second threshold by 2).

[0059] [3] In some embodiments, in the turbine speed control system described in [2] above, the control device is configured to fix the target speed and perform the proportional control for a period of time from the time the connection between the turbine generator and the external power system is disconnected until the predetermined time has elapsed.

[0060] According to the turbine rotation speed control system described in [3] above, during the period when the turbine rotation speed becomes unstable immediately after disconnecting the turbine generator from the external power system (the predetermined period), the target rotation speed is fixed and the proportional control is performed, and after that period, the target rotation speed adjustment mode is performed, so that the turbine rotation speed can be easily prevented from deviating significantly from the desired value (i.e., the value obtained by dividing the sum of the first threshold and the second threshold by 2).

[0061] [4] In some embodiments, in the turbine speed control system described in any of [1] to [3] above, the first threshold is greater than the second threshold.

[0062] According to the turbine rotation speed control system described in [4] above, even if the turbine rotation speed deviates from the range between the first threshold and the second threshold, it is possible to quickly return it to that range and prevent the turbine rotation speed from deviating significantly from the desired value (i.e., the value obtained by dividing the sum of the first threshold and the second threshold by 2).

[0063] [5] In some embodiments, in the turbine speed control system described in any of [1] to [4] above, the first threshold is greater than the rated speed of the turbine (for example, the rated speed Nr described above).

[0064] According to the turbine rotation speed control system described in [5] above, even if the turbine rotation speed deviates from the range between the first threshold and the second threshold, which is greater than the rated rotation speed, it is possible to quickly return to that range and suppress the turbine rotation speed from deviating significantly from the desired value (i.e., the value obtained by dividing the sum of the first threshold and the second threshold by 2).

[0065] [6] In some embodiments, in the turbine speed control system described in any of [1] to [5] above, the second threshold is greater than the rated speed of the turbine (for example, the rated speed Nr described above).

[0066] According to the turbine speed control system described in [6] above, even if the turbine speed falls below a second threshold that is greater than the rated speed, it can be quickly restored to a speed above the second threshold. Therefore, the risk of the turbine speed falling below the rated speed can be reduced, and the risk of reverse power tripping when the turbine generator is reconnected to an external power grid can be reduced.

[0067] [7] In some embodiments, in the turbine speed control system described in any of [1] to [6] above, the first threshold is greater than the second threshold, and the second threshold is greater than the rated speed of the turbine (for example, the rated speed Nr described above).

[0068] According to the turbine speed control system described in [7] above, even if the turbine speed falls below a second threshold that is greater than the rated speed, it can be quickly restored to a speed above the second threshold. Therefore, the risk of the turbine speed falling below the rated speed can be reduced, and the risk of reverse power tripping when the turbine generator is reconnected to an external power grid can be reduced.

[0069] [8] In some embodiments, in the turbine speed control system described in [7] above, if the second threshold is N2 and the rated speed of the turbine is Nr, then 1.0003Nr < N2 < 1.013Nr is satisfied.

[0070] According to the turbine speed control system described in [8] above, the risk of overcurrent tripping of auxiliary equipment and the risk of reverse power tripping when the turbine generator is reconnected to an external power grid can be reduced.

[0071] [9] In some embodiments, in the turbine speed control system described in [8] above, if the first threshold is N1, then 0.0005Nr < N1 - N2 < 0.01Nr is satisfied.

[0072] According to the turbine rotation speed control system described in [9] above, the effects of [8] above can be obtained, and the rotation speed of the turbine can be stabilized quickly.

[0073]

[10] In some embodiments, in the turbine rotation speed control system described in any of [1] to [9] above, the control device is configured to subtract a first predetermined value (for example, the first predetermined value n1 described above) from the target rotation speed when the measured rotation speed of the turbine exceeds the first threshold in the target rotation speed adjustment mode, and to add a second predetermined value (for example, the second predetermined value n2 described above) to the target rotation speed when the measured rotation speed of the turbine falls below the second threshold.

[0074] According to the turbine rotation speed control system described in

[10] above, the turbine rotation speed can be quickly stabilized by appropriately setting the first predetermined value and the second predetermined value.

[0075]

[11] In some embodiments, in the turbine rotation speed control system described in

[10] above, if the first predetermined value is n1, the second predetermined value is n2, and the rated rotation speed of the turbine is Nr, then the following conditions are met: 0.0002Nr < n1 < 0.003Nr and 0.0002Nr < n2 < 0.003Nr.

[0076] According to the turbine rotation speed control system described in

[11] above, the rotation speed of the turbine can be stabilized quickly.

[0077]

[12] In some embodiments, in the turbine speed control system described in any of [1] to

[11] above, the control device is configured to execute the target speed adjustment mode after a first predetermined time has elapsed since the load on the turbine generator was cut off.

[0078] Immediately after the load on the turbine generator is cut off, the turbine's rotational speed becomes unstable. Therefore, if the target rotational speed adjustment mode is executed during the period between the cutoff of the turbine generator's load and the appropriate time elapsed, it becomes difficult to control the turbine's rotational speed. For this reason, as described in

[12] above, by executing the target rotational speed adjustment mode after a predetermined time has elapsed since the load on the turbine generator was cut off, it is easy to suppress the turbine's rotational speed from deviating significantly from the desired value (i.e., the value obtained by dividing the sum of the first threshold and the second threshold by 2).

[0079]

[13] In some embodiments, in the turbine rotation speed control system described in any of [1] to

[11] above, the control device is configured to terminate the target rotation speed adjustment mode when a second predetermined time has elapsed from the start of the target rotation speed adjustment mode.

[0080] In the turbine speed control system described in

[13] above, the proportional control may be continued after the target speed adjustment mode has been terminated by fixing the target speed of the turbine.

[0081] 2: Power plant 4: Gas turbine generator 6: Auxiliary equipment 8: In-house power system 10: Circuit breaker 12: Turbine speed control system 14: Gas turbine 16: Generator 20: Compressor 22: Combustor 23: Fuel supply line 24: Turbine 25: Fuel supply valve 26: Shaft 28: Shaft 29: Tachometer 30: External power system 31: Power meter 34: Load breaker 40: Control device 91: Processor 92: RAM 93: ROM 94: HDD 95: Bus 96: Input I / F 98: Output I / F N1: First threshold N2: Second threshold Nm: Measured rotational speed Nr: Rated rotational speed Ns: Target rotational speed n1: First predetermined value n2: Second predetermined value ΔN: Deviation

Claims

1. A turbine speed control system for controlling the rotational speed of a turbine of a turbine generator, comprising a control device configured to control the valve opening of an input quantity control valve for adjusting the amount of input energy to the turbine, wherein the control device is configured to perform proportional control of the valve opening of the input quantity control valve based on the deviation between the target rotational speed and the actual rotational speed of the turbine when the turbine generator is not connected to an external power system, and the control device is configured to execute a target rotational speed adjustment mode during the execution of the proportional control, wherein the target rotational speed decreases when the actual rotational speed of the turbine exceeds a first threshold, and the target rotational speed increases when the actual rotational speed of the turbine falls below a second threshold.

2. The turbine speed control system according to claim 1, wherein the control device is configured to execute the target speed adjustment mode after a predetermined time has elapsed since the connection between the turbine generator and the external power system was disconnected.

3. The turbine speed control system according to claim 2, wherein the control device is configured to fix the target speed and perform the proportional control during the period from the disconnection of the turbine generator and the external power system until the predetermined time has elapsed.

4. The turbine speed control system according to claim 1, wherein the first threshold is greater than the second threshold.

5. The turbine speed control system according to claim 1, wherein the first threshold is greater than the rated speed of the turbine.

6. The turbine speed control system according to claim 1, wherein the second threshold is greater than the rated speed of the turbine.

7. The turbine speed control system according to claim 1, wherein the first threshold is greater than the second threshold, and the second threshold is greater than the rated speed of the turbine.

8. The turbine speed control system according to claim 7, wherein, if the second threshold is N2 and the rated speed of the turbine is Nr, the condition 1.0003Nr < N2 < 1.013Nr is satisfied.

9. The turbine rotation speed control system according to claim 8, wherein the first threshold value is N1, and the following conditions are met: 0.0005Nr < N1 - N2 < 0.01Nr.

10. The turbine rotation speed control system according to claim 1, wherein the control device is configured to subtract a first predetermined value from the target rotation speed when the measured rotation speed of the turbine exceeds the first threshold in the target rotation speed adjustment mode, and to add a second predetermined value to the target rotation speed when the measured rotation speed of the turbine falls below the second threshold.

11. A turbine speed control system according to claim 10, wherein, if the first predetermined value is n1, the second predetermined value is n2, and the rated speed of the turbine is Nr, the following conditions are met: 0.0002Nr < n1 < 0.003Nr and 0.0002Nr < n2 < 0.003Nr.

12. The turbine speed control system according to claim 1, wherein the control device is configured to execute the target speed adjustment mode after a first predetermined time has elapsed since the load on the turbine generator was shut off.

13. The turbine speed control system according to claim 12, wherein the control device is configured to terminate the target speed adjustment mode when a second predetermined time has elapsed since the start of the target speed adjustment mode.

Images