JP4237606B2 - Turbine controller - Google Patents

Description

  The present invention relates to a turbine control device, and more particularly to a turbine control device that is controlled by a main steam stop valve when the turbine is started and is switched to a steam control valve during normal load operation.

  When the turbine starts, the steam is controlled by the main steam stop valve to start the turbine, and during normal load operation, the steam switching control from the main steam stop valve to the steam control valve is performed to control the steam by the steam control valve. It has been broken. In this valve switching control, a throttle operation command is output from the turbine controller to the steam control valve, and the steam control valve is narrowed to a position equivalent to the control steam amount of the main steam stop valve.

  This narrowing control of the steam control valve is performed by monitoring the steam pressure before and after the main steam stop valve. That is, the steam pressure after the main steam stop valve rises according to the narrowing of the steam control valve, so that the differential pressure ratio between the steam pressure before the main steam stop valve and the steam pressure after the main steam stop valve becomes less than the specified differential pressure ratio. The valve is switched by fully opening the main steam stop valve.

  By narrowing down the valve switching operation at a low speed, it is possible to suppress a decrease in generator output due to main steam pressure loss. However, if the steam control valve is throttled at a low speed from the beginning, it takes time to complete the valve switching, which is not desirable for a thermal power plant that frequently starts and stops according to electric power demand. Therefore, the differential pressure ratio between the steam pressure before the main steam stop valve and the steam pressure after the main steam stop valve is calculated, and the operation amount to narrow down the steam control valve according to this differential pressure ratio is high speed, medium speed, low speed, fine speed. Valve switching control is performed to narrow down the steam control valve by switching in stages.

  As such a valve switching control method, there is a turbine starter described in Patent Document 1. Here, an appropriate opening degree at which the steam control valve does not generate output fluctuation is determined from the main steam pressure and temperature immediately before the start of the valve switching control, and the generator output, and the generator is controlled continuously in the closing direction until the opening degree + α. Output fluctuation is suppressed.

JP-A-5-195713

  In the prior art described in Patent Document 1 or the like, when the steam control valve is narrowed down, the steam pressure before the main steam stop valve is constant while the steam pressure after the main steam stop valve is increased. The switching point of the manipulated variable depending on the magnitude of the differential pressure ratio before and after this main steam stop valve depends on the main steam pressure of the boiler specified in the plant operation when performing valve switching control from the main steam stop valve to the steam control valve. It is set.

  However, when the main steam pressure of the boiler is lower than normal, the differential pressure ratio is small, so the switching point of the operation amount for narrowing down the steam control valve becomes faster, and the speed is increased before the steam control valve opening is sufficiently narrowed. The operation amount is switched to the medium speed operation amount. The change characteristic of the steam pressure after the main steam stop valve when the steam control valve is narrowed is that the change amount of the steam pressure after the main steam stop valve is smaller as the steam control valve is closer to full open, and the steam control valve is closer to full close. Accordingly, the amount of change in the steam pressure after the main steam stop valve increases. For this reason, if the operation amount for narrowing down the steam control valve is switched from the high speed operation amount to the medium speed operation amount before the opening degree of the steam control valve is sufficiently narrowed, there is a problem that the narrowing time of the steam control valve becomes long. is there.

  An object of the present invention is to provide a turbine control device that performs a steam control valve throttle control that does not delay the valve switching time regardless of the state of the steam pressure before the main steam stop valve, in view of the above-described problems of the prior art. is there.

In order to achieve the above object, the present invention provides a turbine control in which steam is controlled by a main steam stop valve at the time of starting the turbine, and steam is controlled by a steam control valve at the subsequent stage of the main steam stop valve during normal load operation. In the apparatus, in order to perform valve switching control from the main steam stop valve to the steam control valve, a differential pressure ratio calculation circuit that calculates a differential pressure ratio between the steam pressure before the main steam stop valve and the steam pressure after the main steam stop valve; The operation amount output circuit that outputs the operation amount to the steam control valve by switching the operation amount of the steam control valve in a stepwise manner according to the magnitude of the differential pressure ratio, and the valve that corrects the operation amount that is applied to the operation amount output circuit. An operation amount correction circuit that avoids extending the switching time is provided. Thereby, even when the steam pressure before the main steam stop valve is lower than normal, the operation amount of the steam control valve can be made equal to that in the normal case.

  Further, the operation amount correction circuit calculates a ratio of a change amount of the steam pressure before the main steam stop valve with respect to a specified value of the steam pressure before the main steam stop valve as a ratio, and a comparison for switching a throttle operation amount of the steam control valve. The switching setting signal used for is multiplied by the ratio.

  Further, the operation amount correction circuit calculates a change amount of the steam pressure before the main steam stop valve with respect to a specified value of the steam pressure before the main steam stop valve as a ratio, and performs comparison for switching the throttle operation amount of the steam control valve. The differential pressure ratio signal to be used is multiplied by the ratio.

  Further, the operation amount output circuit is configured to output the operation amount to the steam control valve by switching the operation amount of the steam control valve to high speed, medium speed, low speed, and fine speed according to the magnitude of the differential pressure ratio. The quantity correction circuit generates a target differential pressure corresponding to the steam pressure value before the main steam stop valve, and a signal that compares the target differential pressure with the differential pressure between the steam pressure before the main steam stop valve and the steam pressure after the main steam stop valve. And the switching timing is determined using the differential pressure ratio and a signal compared with the high-speed switching set value.

  According to the present invention, even if the steam pressure before the main steam stop valve is lowered due to fluctuations in the main steam pressure of the boiler, the valve switching control without delay can be performed, so that there is an effect of stabilizing the plant start-up time.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a turbine control apparatus according to an embodiment of the present invention. The turbine control device 3 controls a steam control valve 4 and a main steam stop valve 5 connected between the steam turbine 2 and the boiler 7. The steam control valve 4 adjusts driving steam to the steam turbine 2 directly connected to the generator 1. The main steam stop valve 5 injects steam all around the turbine in order to disperse local heating when the turbine is started. Before and after the main steam stop valve 5, a steam pressure detector 8 before the main steam stop valve and a steam pressure detector 9 after the main steam stop valve are provided.

  The turbine control device 3 includes a differential pressure ratio calculation circuit 100 and an operation amount output circuit 101. The differential pressure ratio calculation circuit 100 calculates a differential pressure ratio D between the deviation signal C and the pressure signal A, and a subtractor 11 for obtaining a deviation C from the main steam stop valve post-steam pressure signal A from the main steam stop valve post-steam pressure signal B. It is comprised by the divider 12 which performs. The operation amount output circuit 101 is a comparator 18-20 that compares the differential pressure ratio D with each set value of the high-speed switching setter 13, the medium-speed switching setter 14, and the low-speed switching setter 15, and outputs from the comparators. A switch 28-31 is provided for switching the high-speed operation amount 24, the medium-speed operation amount 25, the low-speed operation amount 26, and the fine-speed operation amount 27. Furthermore, a load control circuit 32 that controls the steam control valve 4 after the valve switching is completed, switching devices 33 and 35 that perform switching operation when the valve switching is completed, and a load control circuit 34 that controls the main steam stop valve until the valve switching is completed. Composed.

  Here, the manipulated variable correction circuit 102 provided according to the present invention is surrounded by a dotted line in the figure, and includes a specified pressure setter 50, a divider 51, and multipliers 52, 53, and 54.

  2 and 3 are operation characteristic diagrams of the valve switching control. The former is when the differential pressure ratio before and after the main steam stop valve is normal, and the latter is when the differential pressure ratio is small. When the subtractor 11 calculates the deviation between the steam pressure signal A before the main steam stop valve and the steam pressure signal B after the main steam stop valve, the divider 12 divides the steam pressure signal A before the main steam stop valve from the deviation signal C. Calculate the differential pressure ratio. The differential pressure ratio D is compared with the signals E, F, G from the high-speed switching setter 13, the medium-speed switching setter 14, and the low-speed switching setter 15 by the comparators 18, 19 and 20, and the difference at the time of starting the valve switching. When the pressure ratio D is large, all the comparators 18, 19, and 20 output 1 (high level). As a result, only the switching signal H becomes 1 by the logic circuit after output of the comparators 18, 19, 20, and the switching unit 28 selects and outputs the signal from the high speed operation amount 24. Since the switch 33 is before the valve switching is completed, the signal from the switch 28, that is, the signal from the high speed operation amount 24 is selected and output to the steam control valve 4, and the steam control valve 4 narrows down at high speed. When the steam control valve 4 is narrowed down, the steam pressure B after the main steam stop valve is increased as shown in part a of FIG.

  As the steam pressure B increases after the main steam stop valve, the differential pressure ratio D decreases. The differential pressure ratio D and signals E, F, G from the high speed switching setter 13, the medium speed switching setter 14, and the low speed switching setter 15 are compared by comparators 18, 19, and 20. When the differential pressure ratio D becomes smaller than the high-speed switching setting signal E, only the output of the comparator 18 becomes 0 (low level), and the other comparators 19 and 20 continue to output 1 (high level). Therefore, the switching signal H is 0 and the signal J is 1 by the logic circuit after the outputs of the comparators 18, 19, and 20. Thereby, the switch 29 selects and outputs a signal from the medium speed manipulated variable 25, and the switch 28 selects and outputs a signal from the switch 29. Since the switch 33 is before the valve switching is completed, the signal from the switch 28, that is, the signal from the medium speed manipulated variable 25 is selected and output to the steam control valve 4, and the steam control valve 4 narrows down the medium speed. When the steam control valve 4 is narrowed down, the steam pressure after the main steam stop valve rises with a gentler slope than at high speed, as shown in part b of FIG.

  As the steam pressure B after the main steam stop valve further increases, the differential pressure ratio D further decreases. The differential pressure ratio D is compared with the signals E, F, G from the high-speed switching setting device 13, the medium-speed switching setting device 14, and the low-speed switching setting device 15 by the comparators 18, 19, 20; When it becomes smaller, the outputs of the comparators 18 and 19 become 0, and the comparator 20 continues 1 output. Therefore, the switching signals H and J become 0 and the signal K becomes 1 by the logic circuit after the outputs of the comparators 18, 19 and 20. Thereby, the switch 30 selects and outputs a signal from the low speed operation amount 26, the switch 29 selects and outputs a signal from the switch 30, and the switch 28 selects a signal from the switch 29. Output. Since the switch 33 is before the valve switching is completed, a signal from the switch 28, that is, a signal from the low speed operation amount 26 is selected and output to the steam control valve 4, and the steam control valve 4 narrows down at a low speed. As the steam control valve 4 narrows down, the steam pressure after the main steam stop valve rises with a gentler slope than at the middle speed, as shown in part c of FIG.

  As the steam pressure further increases after the main steam stop valve, the differential pressure ratio D further decreases. The differential pressure ratio D is compared with the signals E, F, G from the high speed switching setter 13, the medium speed switching setter 14, and the low speed switching setter 15 by the comparators 18, 19, 20 and is smaller than the low speed switching setting signal G. As a result, the outputs of the comparators 18, 19, and 20 all become zero. Therefore, only the switching signal L becomes 1 by the logic circuit after the outputs of the comparators 18, 19, and 20. Thus, the switch 31 selects and outputs a signal from the slow operation amount 27, the switch 30 selects and outputs the signal from the switch 31, and the switch 29 selects the signal from the switch 30. The switch 28 selects and outputs the signal from the switch 29. Since the switch 33 is before the valve switching is completed, the signal from the switch 28, that is, the signal from the fine speed manipulated variable 27 is selected and output to the steam control valve 4, and the steam control valve 4 narrows the speed. As the steam control valve 4 narrows down, the steam pressure B after the main steam stop valve rises with a gentler slope than at low speed, as shown in part d of FIG.

  When the steam pressure B after the main steam stop valve finally reaches the valve switching completion pressure and the differential pressure ratio D reaches the valve switching completion differential pressure ratio, a preset valve switching completion condition 36 is established (ON), The switch 35 selects and outputs the fully open operation amount 37, and the main steam stop valve 5 is fully opened. Thereby, the load control by the main steam stop valve 5 performed during valve switching is completed. On the other hand, when the valve switching completion condition 36 is turned ON, the switch 33 selects and outputs a signal from the load control circuit 32, and thereafter, the load control by the steam control valve 4 is performed. The normal valve switching time is, for example, 4-5 minutes, and when it exceeds 6 minutes, a valve switching congestion signal is generated.

  The above is the normal valve switching control. When the steam pressure A before the main steam stop valve at the time when the valve switching control is performed is lower than normal, the operation is performed as shown in the operation characteristic diagram of FIG. That is, the steam pressure B after the main steam stop valve is increased by narrowing the steam control valve, but the steam pressure B before the main steam stop valve is lower than the normal time because the steam pressure A before the main steam stop valve is low. The pressure ratio will be reached. As a result, the steam control valve 4 is switched from the high-speed operation amount to the medium-speed operation amount in a state where the throttling is not sufficiently performed (operation of the part e in FIG. 3).

  Here, the relationship between the opening of the steam control valve 4 and the steam pressure B after the main steam stop valve is such that the closer the steam control valve 4 is to the fully open state, the smaller the amount of change in the steam pressure B after the main steam stop valve is. There is a characteristic that the amount of change in the steam pressure B after the main steam stop valve increases as it approaches the closing. Therefore, the change in the steam pressure B after the main steam stop valve is slowed by switching to the medium speed manipulated variable with a slow throttle speed before the steam control valve opening is sufficiently narrowed, and the time for narrowing the steam control valve 4 is reduced. Takes a long time (operation of part f in FIG. 3). Thereafter, the operation amount is switched between the low speed operation amount and the fine speed operation amount (operations g and h in FIG. 3). From the above, when the steam pressure A before the main steam stop valve is lower than normal, it takes longer to complete the valve switching than normal, and the turbine startup time is delayed. Thereby, when the valve switching time is delayed and a valve switching congestion signal is generated, an erroneous detection of an abnormality in the turbine control device occurs.

  Next, the operation of the operation amount correction circuit 102 according to the present invention will be described. The specified pressure setter 50 is set with a normal pressure before the main steam stop valve as a specified pressure value P. By dividing the specified pressure P from the steam pressure A before the main steam stop valve by the divider 51, a decrease from the steam pressure before the main steam stop valve at the normal time is calculated as a correction value. The correction value is multiplied by the high-speed switching setting signal E, the medium-speed switching setting signal F, and the low-speed switching setting signal G by the multipliers 52, 53, and 54. Correct the decrease in the steam pressure before the valve.

  As a result, even if the steam pressure before the main steam stop valve is lower than normal and the differential pressure ratio D is reduced, the switching setting signals E, F, and G are also reduced by the correction in the same manner as the differential pressure ratio D. As a result, the operations of the comparators 18, 19, and 20 can be performed at the same timing as that during the valve switching control at the normal steam pressure before the main steam stop valve. The amount of restriction of the steam control valve by the high-speed operation amount from the start of valve switching is switched to the medium-speed operation amount after sufficiently restricting similarly to the valve switching control performed at the steam pressure before the main steam stop valve at the normal time. For this reason, the valve switching control can be performed in the same time as the valve switching control performed at the normal steam pressure before the main steam stop valve, and the valve switching control without the delayed traffic jam signal can be performed.

  Next, a second embodiment of the present invention will be described. FIG. 4 is a configuration diagram of a turbine control device according to the second embodiment. The turbine control apparatus according to the present embodiment includes an operation amount correction circuit including a specified pressure setter 60, a divider 61, and a multiplier 62 in addition to the differential pressure ratio calculation circuit 100 and the operation amount output circuit 101 equivalent to those in FIG. 103 is provided.

  The operation of the manipulated variable correction circuit 103 sets the steam pressure before the main steam stop valve at the normal time in the specified pressure setting device 60 as the specified pressure value R. The divider 61 divides the steam pressure A before the main steam stop valve from the specified pressure R, and calculates a decrease from the steam pressure A before the main steam stop valve at the normal time as a correction value. By multiplying this correction value by the differential pressure ratio D by the multiplier 62, the differential pressure ratio D due to the decrease in the steam pressure A before the main steam stop valve is corrected.

  As a result, even if the steam pressure before the main steam stop valve is lower than normal and the differential pressure ratio D becomes smaller, the correction results in a value equivalent to the normal differential pressure ratio. Therefore, the operations of the comparators 18, 19, and 20 that compare the corrected differential pressure ratio T with the switching setting signals E, F, and G are the same as those during normal valve switching control at the steam pressure before the main steam stop valve. It's time.

  Thereby, the amount of narrowing of the steam control valve 4 by the high-speed operation amount from the start of valve switching is switched to the medium-speed operation amount after sufficient throttling, as in the case of normal steam pressure before the main steam stop valve. Therefore, the valve can be switched in the same time as the normal steam pressure before the main steam stop valve.

  Next, a third embodiment of the present invention will be described. FIG. 5 shows a configuration diagram of the turbine control apparatus according to the third embodiment. The difference between the third embodiment and the first embodiment (FIG. 1) is the operation amount correction circuit. The manipulated variable correction circuit 104 according to this embodiment includes a function calculator 70, a comparator 71, and a logical sum calculator 72.

  FIG. 6 shows a characteristic diagram of the function calculator. The function calculator 70 sets the input steam pressure A before the main steam stop valve as the horizontal axis, and the output U sets the differential pressure before and after the main steam stop valve as the vertical pressure corresponding to the state of the steam pressure before the main steam stop valve as the vertical axis. . The point M in the graph is the normal steam pressure before the main steam stop valve, and the target differential pressure at the completion of high-speed narrowing when the valve is switched at the normal steam pressure before the main steam stop valve is the V point. Also, if the steam pressure before the main steam stop valve is lower than normal, and if this point is N point, the high speed throttling completion target differential pressure corresponding to the steam pressure before the main steam stop valve is smaller than the V point. W points.

  As a result, in the operation amount correction circuit 104 of this embodiment, when the steam pressure A before the main main steam stop valve is normal, the function calculator 70 outputs the target differential pressure at the normal time, and the differential pressure C at the valve switching start time is large. Since it is a value, the comparator 71 outputs 1. As a result, the switch 28 outputs the high speed operation amount 24 via the logical sum calculator 72, and the steam control valve is subjected to high speed narrowing operation via the switch 33.

  When the value of the differential pressure C decreases due to the narrowing of the steam control valve 4, the comparator 71 becomes 0 when it becomes smaller than the target differential pressure signal U at the normal time. Further, the comparator 18 becomes 0 when the differential pressure ratio D becomes smaller than the high-speed switching setting signal E. At the later operation timing of the comparator 71 and the comparator 18, both inputs of the logical sum calculator 72 become 0 and the output also becomes 0. Then, after the steam control valve throttle operation amount is switched to the medium speed operation amount, the operation is equivalent to the operation of the conventional valve switching control.

  On the other hand, when the steam pressure before the main steam stop valve has decreased before the valve switching, the function calculator 70 outputs the target differential pressure when the steam pressure before the main steam stop valve decreases (point N in FIG. 6). . Since the differential pressure C at the start of valve switching is a large value, the comparator 71 outputs one output. As a result, the switch 28 outputs the high speed operation amount 24 via the logical sum calculator 72, and the steam control valve is subjected to high speed narrowing operation via the switch 33. When the steam control valve 4 is narrowed down, the comparator 18 that compares the differential pressure ratio D and the high-speed switching setting signal E becomes 0, but the function calculator 70 is set with the target differential pressure when the steam pressure before the main steam stop valve decreases. Therefore, the comparator 71 does not operate unless the differential pressure C before and after the main steam stop valve is small. Thereby, the comparator 71 becomes 0 when the steam control valve is sufficiently narrowed and becomes smaller than the target differential pressure signal U at the time of the steam pressure drop before the main steam stop valve, and the output of the logical sum calculator 72 is also 0. Become. Then, after the steam control valve throttle operation amount is switched to the medium speed operation amount, the operation is equivalent to the operation of the conventional valve switching control. As a result, the steam control valve 4 can be sufficiently throttled at a high speed operation amount, and valve switching control can be performed without delay even when the steam pressure before the main steam stop valve is lower than normal.

The block diagram of the turbine control apparatus by Example 1 of this invention. Explanatory drawing of valve switching control operation at the time of starting (at the time of the normal pressure before the main steam stop valve). Explanatory drawing of valve switching control operation at the time of starting (when the pressure before the main steam stop valve decreases). The block diagram of the turbine control apparatus of Example 2. FIG. FIG. 6 is a configuration diagram of a turbine control device according to a third embodiment. FIG. 10 is a characteristic diagram of the function calculator of the third embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Generator, 2 ... Steam turbine, 3 ... Turbine controller, 4 ... Steam control valve, 5 ... Main steam stop valve, 7 ... Boiler, 8 ... Steam pressure detector before main steam stop valve, 9 ... Main steam stop Steam pressure detector after valve, 11 ... subtractor, 12 ... divider, 13 ... high speed switching setter, 14 ... medium speed switching setter, 15 ... low speed switching setter, 18, 19, 20 ... comparator, 24 ... High speed manipulated variable setter 25: Medium speed manipulated variable setter 26: Low speed manipulated variable setter 27 27 Slow manipulated variable setter 28-31 Switcher 32 Load control circuit 33 Switcher 34 DESCRIPTION OF SYMBOLS ... Load control circuit, 35 ... Switch, 36 ... Valve switching completion condition, 37 ... Fully opened operation amount, 50 ... Prescription pressure setter, 51 ... Divider, 52-54 ... Multiplier, 60 ... Prescription pressure setter, 61 ... Divisor, 62 ... Multiplier, 70 ... Function calculator, 71 ... Comparator, 72 ... Logical ring calculator 100 ... differential pressure ratio calculating circuit, 101 ... manipulated variable output circuit, 102, 103, 104 ... operation quantity correction circuit.

Claims (4)

In a turbine control device that controls steam by a main steam stop valve at the time of starting the turbine, and controls steam by a steam control valve in the subsequent stage of the main steam stop valve during normal load operation,
A differential pressure ratio calculation circuit for calculating a differential pressure ratio between the steam pressure before the main steam stop valve and the steam pressure after the main steam stop valve in order to perform the valve switching control from the main steam stop valve to the steam control valve, and the differential pressure ratio The operation amount output circuit that outputs the operation amount to the steam control valve by switching the operation amount of the steam control valve step by step according to the size of the valve, and the operation amount output circuit that corrects the operation amount to be applied to the operation amount output circuit to correct the valve switching time. A turbine control device comprising an operation amount correction circuit for avoiding extension.   The operation amount correction circuit according to claim 1, wherein the operation amount correction circuit calculates a change amount of the steam pressure before the main steam stop valve with respect to a specified value of the steam pressure before the main steam stop valve as a ratio, and switches a narrowing operation amount of the steam control valve. A turbine control device characterized by multiplying the switching setting signal used for the comparison by the ratio.   The operation amount correction circuit according to claim 1, wherein the operation amount correction circuit calculates a change amount of the steam pressure before the main steam stop valve with respect to a specified value of the steam pressure before the main steam stop valve as a ratio, and switches a narrowing operation amount of the steam control valve. A turbine control device that multiplies the differential pressure ratio signal used for the comparison by the ratio. 2. The operation amount output circuit according to claim 1, wherein the operation amount output circuit is configured to output an operation amount to the steam control valve by switching a throttle operation amount of the steam control valve to high speed, medium speed, low speed, and fine speed according to the magnitude of the differential pressure ratio. The manipulated variable correction circuit generates a target differential pressure corresponding to the steam pressure value before the main steam stop valve, and calculates the differential pressure between the steam pressure before the main steam stop valve and the steam pressure after the main steam stop valve and the target differential pressure. A turbine control device that determines a switching timing using a signal that has been compared and a signal that has been compared with the differential pressure ratio and the high-speed switching set value.

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