JPH0735722B2 - Turbine controller - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a turbine control device, and more particularly to a turbine control device provided with a turbine bypass system capable of controlling a steam amount corresponding to a steam condition when a turbine is started.

[Technical background of the invention and its problems]

Generally, when a turbine bypass system is used in a thermal power plant, reduction in start-up time is evaluated, and recently, a large capacity to supply bleed air to an industrial plant that requires a large amount of process steam, such as a desalination plant. Turbine bypass systems are also increasingly used in extraction turbines. In this case, the adoption of the turbine bypass system is not for shortening the start-up time of the steam turbine but for supplying steam to the main purpose process such as the fresh water plant, and the steam turbine is rather an auxiliary device of the fresh water plant. Since it can be said that
The steam turbine including the turbine bypass system is under severer usage conditions than general thermal power plants. FIG. 3 is a system diagram showing a schematic configuration of an extraction turbine plant including the turbine bypass system described above. Steam generated in the boiler 1 having the reheater 1a is a main steam stop valve 2 and a steam control valve 3 The steam that has been introduced into the high-pressure turbine 4 via the high-pressure turbine 4 and has worked in the high-pressure turbine 4 returns to the boiler 1 via the check valve 5 and is reheated.
And through the combined reheat valve 6 with the intercept valve 6b to the medium pressure turbine 7. The steam thus introduced into the intermediate-pressure turbine 7 performs work here, flows into the low-pressure turbine 21 through the extraction control valve 20, performs the work, and then is condensed in the condenser 23 to be condensed. It passes through the pump 24, the low-pressure heater 27, the water supply pump 10, and the high-pressure heater 11 in order, and returns to the boiler 1 again. A generator 22 is connected to a shaft common to the high pressure turbine 4, the intermediate pressure turbine 7, and the low pressure turbine 21.

On the other hand, part of the steam that worked in the medium-pressure turbine 7
A part of the extracted steam is extracted to the deaerator 9 while the remaining steam is extracted by the check valve 8.
It is introduced into the collective header 17 via 16 and supplied to the fresh water plants 19a and 19b through the supply valves 18a and 18b. The upstream side of the main steam stop valve 2 and the downstream side of the check valve 5 are connected by a high pressure bypass pipe 12 having a high pressure bypass valve 13 for bypassing the high pressure turbine 4, and upstream of the combination reheat valve 6. The side and the downstream side of the check valve 16 and the condenser 23 are connected by a medium pressure bypass pipe 14 having a medium pressure bypass valve 15 and a low pressure bypass pipe 26 having a low pressure bypass valve 25, respectively. The low pressure bypass pipe 26 includes the combination reheat valve 6, the intermediate pressure turbine 7, the extraction control valve 20, and the low pressure turbine.
It forms a bypass for the 21 steam system.

The steam extracted from the other extraction turbine 100 is introduced into the collecting header 170 and is supplied to the desalination plants 190a and 190b through the supply valves 180a and 180b. Since the collective header 17 and the collective header 170 are connected via the sluice valve 171, the desalination plant can be operated independently by operating the sluice valve 171 arbitrarily, or the extraction turbine from either one can be operated. However, even if it is stopped due to a decrease in power demand, periodic inspections, accidents, etc., steam is supplied from the collective header by opening the sluice valve 171. Therefore, one steam turbine can operate two desalination plants simultaneously. it can. If the boiler 1 has already started up, it is possible to supply steam to the collecting header 17 through the intermediate pressure bypass pipe 14 having the intermediate pressure bypass valve 15 even before the turbine is started up. Only the boiler 1 and the turbine bypass system (system of the bypass pipes 12 and 14) can operate only the desalination plants 19a and 19b.

By the way, generally, in a steam turbine having a turbine bypass system, at the time of starting the steam turbine, the main steam is made to flow into the high-pressure turbine and the reheated steam is made to flow into the intermediate-pressure turbine at the same time, and the rotational speed of the steam turbine is gradually increased. Change to load operation. In this case, normally, the steam supply amount to the high-pressure turbine and the medium-pressure turbine is considered so that the cooling steam flows more on the high-pressure turbine side in order to prevent the temperature from rising due to windage loss in the high-pressure turbine compartment. In addition, the steam pressures of the steam generators are always controlled under constant conditions by the high pressure and low pressure bypass systems.

By the way, in the case where the main purpose of the plant is desalination as described above, the turbine bypass system is used to start only the desalination plant before starting the turbine, or two desalination plants are installed. When driving at the same time,
Each time, the pressure and temperature of the main steam and the high temperature reheated steam are determined irrespective of the start of the steam turbine. Also, since these pressures and temperatures change according to the required load of the desalination plant at that time, the starting steam condition of the steam turbine is not constant, and the turbine must be started in an uncertain state. There was a drawback that the amount of steam to the high-pressure turbine was insufficient and the final stage of the high-pressure turbine was overheated and damaged.

[Object of the Invention]

In order to eliminate such drawbacks, the present invention selects the optimum steam turbine starting conditions under such conditions even if the conditions of main steam and high temperature reheated steam change corresponding to the process side, and it is safe. It is an object of the present invention to provide a steam turbine control device capable of starting a steam turbine.

[Outline of Invention]

The present invention uses a main steam from a boiler to operate a high-pressure turbine through a main steam valve, and a steam from the high-pressure turbine is reheated by a reheater to obtain steam through an intercept valve. The reheat steam system that operates the medium-pressure turbine, the low-pressure steam system that operates the low-pressure turbine through the extraction control valve with the steam from the medium-pressure turbine, the high-pressure bypass valve that bypasses the main steam valve and the high-pressure turbine, and the intercept. A medium pressure bypass valve that bypasses the valve and the medium pressure turbine and supplies reheated steam from the reheater to the desalination plant; an intercept valve; a medium pressure turbine;
In a turbine control device for controlling a turbine plant equipped with an extraction control valve and a low-pressure bypass valve for bypassing a low-pressure turbine, when the turbine is started, the pressure of the main steam and Control that controls the opening of only the intercept valve so that the flow rate of reheat steam flowing into the medium-pressure turbine becomes a predetermined ratio based on the amount of main steam flowing into the high-pressure turbine according to the pressure of the hot steam. It is characterized in that means is provided, and an accident due to overheating of the high-pressure turbine at the time of startup can be prevented in advance without performing a complicated startup operation at startup of the steam turbine. .

Example of Invention

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. The same parts as those in FIG. 3 in the above figure are designated by the same reference numerals, and detailed description thereof will be omitted.

The rotation speed of the high-pressure turbine 4 is detected by the speed detector 200 having the speed detection gear 200a and the magnetic pickup 200b, and is given to the adder 202 via the frequency / voltage converter 201. The difference between the rotation speed signal of the high-pressure turbine 4 and the setting signal from the speed load setter 203, that is, the speed deviation signal is formed by the adder 202, and the speed adjustment circuit 204 of the intercept valve and the speed adjustment of the main steam control valve are formed. The constant circuit 205 and the main steam stop valve speed adjusting circuit 206 are provided. The output signal of the speed adjusting circuit 206 is given to the adder 210. A bias signal from the full-circulation injection / partial injection bias circuit 209 is also input to the adder 210, and the sum signal and the signal from the load limiter 212 are input to the low value priority circuit 213. The output signal of the low value priority circuit 213 and the signal from the constant circuit 207 are added by the adder 216, and the sum signal is added by the adder 242a and the amplifier 2
42b, power amplifier 242c, electro-hydraulic converter 242d, differential transformer 242e, and demodulator 242f. The output signal of the speed adjustment circuit 205 and the bias signal from the full-circle injection / partial injection bias circuit 209 are added by the adder 208, and the output signal is the load limiter 2
The signal from 12 is input to the low value priority circuit 211, and the low value output is given to the adder 215. A signal from the constant circuit 225 is also input to the adder 215, and its output signal is a valve position control circuit 243 having the same configuration as the valve position control circuit 242 described above.
Given to. The output signal of the function generator 238, which receives the signal from the logic circuit 237, is input to the adder 240 together with the signal provided from the fully open bias circuit 226 via the switch 241 which is closed when the low pressure bypass valve 25 is fully closed. Adder 2
The output signal of 40 and the signal from the speed adjustment circuit 204 are input to the low value priority circuit 239, and the output signal of this low value priority circuit 239 is given to the valve position control circuit 244. The pressure signal of the reheated steam supplied to the desalination plant is given to the adder 218 via the pressure detector 217. A setting signal from the extraction pressure setting device 219 is also input to the adder 218, and the deviation signal is given to the low value priority circuit 221 via the extraction pressure limiting circuit 220. The signal from the extraction limiter 222 is also input to the low value priority circuit 221, and the deviation between the output signal and the signal of the constant circuit 224 is calculated by the adder 223. Changeover switch for constant circuit 224
The output signal of the low value priority circuit 211 or 213 is selectively input via 214. The deviation signal output from the adder 223 is given to the valve position control circuit 245. Changeover switch 214
Is switched by the operation switching of the full-circulation injection / partial injection by the full-circulation injection / partial injection bias circuit 209. Valve position control circuits 242, 243, 244, 245 are oil cylinders 246, 247, 24, respectively.
The openings of the main steam stop valve 2, the steam control valve 3, the intercept valve 6b, and the extraction control valve 20 are controlled via 8,249. As shown in FIG. 2, the logic circuit 237 controls the amount of steam flowing into the high pressure turbine 4 and the amount of steam flowing into the intermediate pressure turbine 7 according to the main steam pressure from the boiler 1 and the reheat steam pressure from the reheater 1a. It is provided to determine the ratio,
A specific example will be described later. Valve position control circuit 243,
The configurations of the valve position control circuit 244 and the valve position control circuit 245 are
It is the same as the valve position control circuit 242 and includes an adder, an amplifier, a power amplifier, an electro-hydraulic converter, a differential transformer and a demodulator.

By the way, there are the following three types of turbine start-up patterns.

(A) Cold start Even if the plant has a turbine bypass system and an industrial plant that uses bleed air, for example, a desalination plant, the steam turbine is first used as a simple reheat turbine without operating and operating these plants. The activation pattern to activate.

(B) Hot start (1) A startup pattern in which the own desalination plant using the turbine bypass system is already in the operating state, and then the steam turbine of the own is started.

(C) Hot start (2) Using the turbine bypass system, with only one boiler of its own plant, while operating both its own desalination plant and other desalination plants, then start its own steam turbine The activation pattern to do.

Here, the hot start (1) and (2) not only operate the desalination plant first as a process of starting the plant, but also use the turbine bypass system even when restarting after the trip operation of the steam turbine. Needless to say, it is applied when the desalination plant side is continuously operated.

The operation of the apparatus shown in FIG. 1 will be described below for each activation pattern.

(A) Cold start In the case of cold start, the turbine bypass system is not used, that is, the turbines are started with all bypass valves fully closed, and the steam supply amount to the high pressure turbine 4 and the intermediate pressure turbine 7 is reduced. You don't have to consider the ratio,
The flow rate ratio at this time is 1: 1. In this case, in order to control the rotation speed (load) of the steam turbine, a frequency signal proportional to the turbine rotation speed is first obtained by the speed detector 200 connected to the high pressure turbine 4. This signal is converted by the frequency / voltage converter 201 into an analog signal proportional to the frequency. This analog signal is an actual rotation speed signal and is added by the adder 202 to the speed load setter 203.
The speed deviation signal is formed by being compared with the setting signal from the speed deviation signal, and this speed deviation signal is branched into three. One of them is supplied to the speed adjustment circuit 205 for the steam control valve 3, where a speed control signal matching the speed adjustment rate is formed. The other one is a speed adjusting circuit for the main steam stop valve 2.
206, where a speed control signal matching the speed regulation rate is formed. These speed control signals are added by the adder 208 and the adder 210 with the bias signal from the full-circle injection / partial-injection bias circuit 209 for switching the full-circle injection operation and the partial injection operation by the absolute ratio. , And becomes an input to the low value priority circuit 211 and the low value priority circuit 213. In the low value priority circuits 211 and 213, the load limiter 212
The control signal of the steam control valve 3 or the main steam stop valve 2 is compared with the control signal from the extraction pressure control system by the adders 215 and 216 after the signal having a low value is output after comparison with the limit signal from Become valve position control circuit 243
Alternatively, it is input to the valve position control circuit 242.

On the other hand, the outputs of the low-value priority circuit 211 and the low-value priority circuit 213 are added via the constant circuit 224 via the switch 214 that operates by the operation switching of the full-circulation injection / partial injection bias circuit 209. It is also supplied to the vessel 223. The constant circuit 224 is provided to equalize the flow rate changes of the valve opening signal of the steam control valve 3 or the main steam stop valve 2 and the opening signal of the extraction control valve 20 from the speed control system. .

Since the valve position control circuits 242, 243, 244, 245 all have the same configuration as shown in FIG. 1, the one for the main steam stop valve 2 will be described as a representative. For the main steam stop valve 2 from the adder 216, The control signal of the
The actual opening signal of the main steam stop valve 2 derived from the output of the hydraulic pressure converter 242d is compared and calculated, and is taken out as an opening error signal. This opening degree error signal is adjusted by the amplifier 242b with the optimum loop gain of the main steam stop valve position control, then power-amplified by the power amplifier 242c and transmitted to the electro-hydraulic converter 242d. One of the mechanical output signals of the electric / hydraulic converter 242d becomes an input signal of the oil cylinder 246 for the main steam stop valve 2, and the oil pressure is amplified by the oil cylinder 246 to open the main steam stop valve 2. Control the degree. On the other hand, the mechanical output signal of the electro-hydraulic converter 242d is converted into a position signal by the differential transformer 242e directly connected to the electro-hydraulic converter 242d, and the demodulator 24
After being demodulated to an electric signal in 2f, it is given to the adder 242a as an actual opening signal of the main steam stop valve 2.

Closed loop valve position control circuit 242 configured as above
Will control the valve opening of the main steam stop valve 2 so that the opening command value input to the adder 242a becomes equal to the actual opening. Further, the outputs of the adder 215 and the adder 216 are input to the valve position control circuit 242 and the valve position control circuit 243, but by operating the full-circulation injection / partial injection bias circuit 209, the rotational speed ( The (load) control is shifted to the steam control valve 3 side, and the main steam stop valve 2 and the steam control valve 3 are not in the control state at the same time. The remaining one of the three branched speed deviation signals is transmitted to the speed adjusting circuit 204 for the intercept valve 6b and becomes the input signal of the low value priority circuit 239. This low value priority circuit 239 is the sum of the signal from the control circuit used at the time of hot start described later and the intercept valve fully open bias signal provided via the switch 241 which is closed when the low pressure bypass valve 25 is fully closed. Signal is input, a comparison operation of low value priority is performed on these two input signals, and as a result, it becomes a control signal for opening the intercept valve 6b prior to the steam control valve 3 and becomes a control signal for the intercept valve 6b. Valve position control circuit 244
Is output to.

Explaining the extraction pressure control system, the extraction pressure from the turbine device to the desalination plant is detected by the pressure detector 217 as an analog signal proportional to the extraction pressure.
This detection signal is sent to the extraction pressure setting device 219 by the adder 218.
Is calculated and compared with the setting signal from. The extraction pressure deviation signal output from the adder 218 is transmitted to the extraction pressure control circuit 220 and becomes an extraction pressure control signal corresponding to the extraction pressure adjustment rate. This bleed pressure control signal is transmitted to the low value priority circuit 221, where the limit signal from the bleed air limiter 222 and the comparison calculation for low value priority are performed. This low value priority circuit 222
Is input to the adder 215 and the adder 216 of the control system of the steam control valve 3 and the main steam stop valve 2 via the constant circuit 225 and the constant circuit 207, and is output as a valve opening command value from the extraction pressure control system. A comparison operation is performed to equalize the flow rate changes. The output from the low value priority circuit 221 is added by the adder 223 from the speed control system as described above, that is, the bleed air control valve opening command value from the constant circuit 224 to form a bleed air control valve opening signal. The valve position control circuit 24 of the bleed air control valve 20
Output to 5.

Even if the turbine bypass system is provided and the desalination plant is provided as described above, if the steam turbine is started as a simple reheat turbine without operating and operating these before starting the steam turbine, the low pressure bypass Valve 25
Since the intercept valve 6b is opened prior to the steam control valve 3 corresponding to the speed adjustment rate on the condition that is fully closed, the steam inflow amounts of the high pressure turbine 4 and the intermediate pressure turbine 7 become equal.

(B) Hot start (1), (2) Next, the case of hot start will be described. In this case, the turbine bypass system is used to supply steam to the desalination plant side before the steam turbine is started. Since it is the turbine bypass operation, the steam flow rate ratio between the high-pressure turbine 4 and the intermediate-pressure turbine 7 must be taken into consideration as described above. However, the high-temperature reheat steam pressure controlled by the low-pressure turbine bypass valve 25 and the main steam pressure controlled by the high-pressure bypass valve 13 change according to the required steam amount on the side of the desalination plant. Will need to be reviewed for each steam turbine and each time it is started.

Here, considering the outline of the pressures of the main steam and the high-temperature reheat steam, the high-temperature reheat steam pressure controlled by the low-pressure bypass valve 25 is controlled by the amount of steam supplied to the desalination plant by the intermediate-pressure bypass valve 15. In the operation of one desalination plant and the operation of two units including the other, since the increase in the amount of steam is dealt with by using the medium pressure bypass valve already installed, the front side of the medium pressure bypass valve 15 The pressure, that is, the high temperature reheat steam pressure may be increased. Therefore, as a result, the pressure control set value of the low-pressure bypass valve 25 is operated when only one self-producing plant (in the following description, is symbolized as P _R1 = 7 ^K ) and other two are operated. There are two types of time (which will be symbolized as P _R2 = 14 ^{K in the} following description). On the other hand, the main steam pressure changes from the operating state of the boiler when starting the turbine to the rated condition (in the following description,
P _M1 = 140 ^K ) and boosting operation (P
Symbolize as _M2 ≤ 140 ^K. Below the rated conditions).
A control mode at the time of hot start (1) and hot start (2) by combining these four kinds of steam pressures will be described. It should be noted that the hot start (1) and the hot start (2) are different only in the quantity of the desalination plant to be operated, and all are included in the following description, so no special distinction is made. Further, in the case of hot start, there is no particular change except for the control of the intercept valve 6b, so only the change will be described. The control signal of the intercept valve 6b is output from the speed adjusting circuit 204 of the intercept valve 6b and the logic circuit 2 via the switch 214 that operates by switching the operation between full-circle injection and partial injection.
The signal from the main steam stop valve 2 or steam control valve 3 side that has passed through 37, the function generator 238 and the adder 240 is the low value priority circuit 23.
Entered in 9. Here, the output signal of the adder 240 is the control signal itself from the function generator 238 side because the switch 241 is not turned on because the low-pressure bypass valve 25 is in the operating state. In addition, the speed adjustment circuit 204 input to the low value priority circuit 239
From the control signal from the adder 240,
The latter is configured to always have a low value. That is, the logic circuit 237 selects the flow rate ratio calculated to be sufficient for cooling the high pressure turbine 4 as shown in FIG. 2 according to the pressure conditions of the main steam and the high temperature reheated steam described above, and makes the selection. A control signal as a numerical value relating to the main steam corresponding to the determined flow rate ratio is output to the function generator 238.
The output signal of the function generator 238 is a function of the flow rate characteristics of the main steam stop valve 2 or the steam control valve 3 and the intercept valve 6b, and is converted into a control signal of the intercept valve 6b by receiving the input signal from the logic circuit 237. However, according to FIG. 2, since the flow rate ratio is 3: 1, 2: 1, conversion is performed with the high-pressure turbine 4 side as the reference, so the actual output on the medium-pressure turbine 7 side is 1 /
A low value of 3 or 1/2 is input to the adder 240.
Therefore, in the low value priority circuit 239, the adder 240 side always has a low value.

According to such a control method by the logic circuit 237 and the function generator 238, the hot start (1) and the hot start (2) have different flow rate ratios, but the main steam stop valve 2 or the steam control valve 3 is always used. Since the control signal for the intercept valve 6b is formed based on the control signal for the intercept valve 6b, the main steam stop valve 2 or the steam control valve 3 and the intercept valve 6b are linked to perform the opening / closing operation. In the turbine bypass operation, that is, until the low pressure bypass valve 25 is fully closed and the switch 241 is turned on, and the full open bias signal from the full open bias circuit 226 of the intercept valve is applied, the aforementioned interlocking relationship is maintained.

〔The invention's effect〕

Since the present invention is configured as described above, even when the flow rate ratio between the high pressure turbine and the intermediate pressure turbine changes during operation during turbine startup due to some cause, the steam valve that controls the flow rate change in response to the change in the flow rate ratio. Becomes an intercept valve, so that there are fewer disturbance elements in the steam turbine and better startup control can be achieved. Moreover, it is possible to prevent a serious accident due to overheating of the high-pressure turbine at the time of startup.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a turbine control device of the present invention, FIG. 2 is a logic diagram of a logic circuit for determining a flow rate ratio between a high pressure turbine and an intermediate pressure turbine, and FIG. It is a schematic system diagram of a steam turbine that does. 2 ... Main steam stop valve, 3 ... Steam control valve, 4 ... High-pressure turbine, 6 ... Combination reheat valve, 6a ... Reheat steam stop valve,
6b …… intercept valve, 19a, 19b, 190a, 190b …… desalination plant, 203 …… speed / load setter, 205 …… steam control valve speed adjustment circuit, 209 …… full injection / partial injection bias circuit, 226 …… Fully open bias circuit, 240 …… Adder, 242,24
3,244,245 …… Valve position control circuit, 242a …… Adder, 242b
...... Amplifier, 242c …… Power amplifier, 242d …… Electro-hydraulic converter, 242e …… Differential transformer, 242f …… Demodulator, 237
...... Logic circuit, 238 …… Function generator.

Claims (1)

[Claims] Claim: What is claimed is: 1. A main steam system for operating a high-pressure turbine via a main steam valve from a main steam from a boiler, and a reheated steam obtained from a high-pressure turbine via a reheater via an intercept valve. A reheat steam system for operating a medium-pressure turbine, a low-pressure steam system for operating a low-pressure turbine with steam from the medium-pressure turbine via an extraction control valve, a high-pressure bypass valve for bypassing the main steam valve and the high-pressure turbine, A medium-pressure bypass valve that bypasses the intercept valve and the medium-pressure turbine and supplies reheated steam from the reheater to the industrial plant, and a low-pressure bypass that bypasses the intercept valve, the medium-pressure turbine, the bleeder regulator and the low-pressure turbine. In a turbine control device that controls a turbine plant equipped with a valve, the low-pressure bypass valve is fully closed when the turbine is started. If not, the interception is performed so that the flow rate of reheated steam flowing into the intermediate pressure turbine becomes a predetermined ratio based on the amount of main steam flowing into the high pressure turbine according to the pressure of main steam and the pressure of reheated steam. A turbine control device comprising control means for controlling the opening of only a valve as a control target.