JPH01216005A - Turbine control device - Google Patents

Abstract

PURPOSE:To prevent sudden closing of an intercept valve during normal operation by providing a restricting means on changing rate of an intercept valve opening signal and a releasing means from restriction on the changing rate of the intercept valve opening signal to a means to control opening of the intercept valve. CONSTITUTION:A malfunction preventing circuit 50 is interposed in a controlled system which provides a final load signal that is output from a load distributing part 38 of a turbine controlling device to an intercept valve. The malfunction preventing circuit 50 is equipped with a restricting circuit 504 on changing rate, which restricts such a large signal that a dash pot of an intercept valve mechanism acts when the large signal is input during normal operation. And the malfunction preventing circuit 50 is also equipped with a releasing circuit from restriction on changing rate, which is composed of a one-shot circuit 503 which is connected to the restricting circuit 504, an OR circuit 502, a turbine acceleration detecting circuit 501, a subtracter 505, an absolute value circuit 506 and comparator 507. Thereby sudden closing of the intercept valve during normal operation is prevented, while sudden closing at the time of load shutdown is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a turbine control device, and particularly to a turbine control device that takes into account prevention of malfunction of an intercept valve.

[Conventional technology]

Mechanical-hydraulic governors (MIIG) and electro-hydraulic governors (EHG) are known as means for controlling the speed of a steam turbine when driving a generator, pump, etc. In addition, in order to prevent the turbine speed from becoming excessive in the case of load shedding, etc., an intercept valve is installed in the steam pipe and a means for controlling it is installed.In the intercept valve installed alongside the 0MHG, A dashpot mechanism is provided that abruptly closes the valve when the closing speed instructed to the valve (corresponding to the rate of increase in turbine rotational speed) is greater than a certain value (dashpot operating point).

FIG. 4 shows an example of a schematic diagram of a steam turbine generator equipped with an intercept valve. Steam generated in the boiler 1 is transferred to the main steam stop valve 2. It passes through the control valve 3 and is supplied to the steam turbine IO. Turbine 10 typically includes a high pressure turbine 11. Medium pressure turbine 12° and low pressure turbine 13
After the steam does work in the high-pressure turbine 11, it is reheated and heated in the reheater 16, and then passed through the reheat steam stop valve 17.
．． The water passes through an interrupt valve 18 equipped with a dashpot, which is a quick-closing mechanism, and then works in an intermediate pressure turbine 12 and a low pressure turbine 13, and becomes water in a condenser 19. The work of the steam is converted into rotational motion by the turbine 10, which turns the generator 20, and the electric power generated by the single engine A-machine 20 is supplied to the power supply system through the power transmission line.

FIG. 7 shows the operating characteristics of the intercept valve when the turbine is controlled by a mechanical-hydraulic governor.

During control during normal operation, the speed relay is activated based on the magnitude of the deviation of the detected turbine speed from the set value of the turbine speed, but when the detected turbine speed increases compared to the set value, the speed relay operates. The stroke decreases and the speed relay stroke increases as the sensed turbine speed decreases. As the speed relay stroke increases, the intercept valve 18 first
is fully opened, and then the control valve 3 is opened.

When the rotational speed change rate of the turbine is small, the opening of the response valve changes along the solid lines B and C in Fig. 6, but when the turbine speed increases, as in the case of load shedding, the dashpot operating point When the value becomes larger than , the intercept valve is rapidly closed along the dashed line A before the regulating valve is fully closed due to the dashpot characteristic, and the generation of overspeed of the turbine is prevented. The speed increase rate (speed change rate) of the turbine, which is the dashpot operating point, is 1MHG.

It is set in consideration of the sensitivity and responsiveness of the hydraulic system and mechanical parts to changes in rotational speed.

Next, the operation of an electronic turbine control system in which the mechanical-hydraulic governor is replaced with an electro-hydraulic governor and the speed detection section and calculation section are electronic will be explained with reference to FIG. The turbine controller fi22 controls the rotation speed, load, etc. of the turbine 10. The rotational speed of the turbine 10 is detected by a speed detector 15 via a gear 14 mounted on the rotating shaft of the turbine 10, and the load of the turbine 10 is detected by a power converter 21 coupled to the output side of a generator 20. Detected. The detected rotation speed and load signals are sent to the control device! 22 input section 2
3 and processed by the calculation unit 25. In the calculation unit 25, an intercept valve 18 equipped with a dashpot and a control valve 3 are used to control the rotation speed, load, etc. of the turbine lO.
etc., calculates the opening degrees of a plurality of valves, and outputs a valve drive signal that drives the response valve so that the opening degree is achieved. The valve drive signal is sent to the intercept valve drive unit 9 by the output section 24.
．． The signal is sent to a control valve drive unit such as the control valve drive unit 7, and drives the valve. The movement of the valve is detected by an intercept valve opening detector 8. It is detected by a response valve opening detector such as the adjustment valve opening detector 6, and is fed back to the input section 23 of the controller M22 to determine the valve opening.

FIG. 5 shows a part of the configuration of the control device 22. As shown in FIG. The turbine rotational speed detected by the speed detector 15 is input to the comparator 32 as an actual speed signal N, and is compared with a set speed signal N0 set by the speed setter 31 and input to the comparator 32. The comparison unit 32 calculates the deviation amount ΔN(
ΔN=N, -N).

It is output to the adjustment rate calculation section 33.

ΔN is multiplied by a gain corresponding to a preset speed adjustment rate in the adjustment rate calculation unit 33 and is transmitted to the addition unit 35. The adder 35 adds the signal P0 set by the load setter 34 to create a load signal Pa. Speed adjustment rate 8
is the value that indicates the percentage deviation of the speed (when the generator is connected to the power grid and operates synchronously, it corresponds to the frequency of the grid) from the set value (rated value) before the full load is changed. For example, an adjustment rate of 5% means that if there is a speed deviation of 5%, the load will change by 100%. That is,
Assuming that the system frequency (speed) increases by 5% during 100% load operation, the negative load is reduced to 0% to keep the frequency stable.

The load signal PG is compared with the load limit value PL set by the load controller 36 in a low value priority circuit 37, and the lower signal becomes the final load signal P. The load signal P is transmitted to the load distribution section 38
．． 42 etc. according to the share of the answering valve, and becomes a valve opening degree signal to determine the opening degree (flow rate) of the answering valve and control the valve opening degree of the answering valve. In FIG. 6, only the portions subsequent to this point are shown for the intercept valve 18, and the others are omitted.
They have the same configuration. Output of load distribution section 38 (valve opening signal)
is compared with the valve opening feedback signal U output from the intercept valve opening detector 8 in the comparator 39, and the deviation signal is converted into a valve drive signal Sv by the adjustment control unit 40 and intercepted by the valve drive unit 9. Adjust the opening degree of the valve 18. The opening degree of the intercept valve 18 is detected by the opening degree detector 8, and is fed back as a valve opening degree feedback signal U through the position converting section 41, and is given to the above-mentioned comparison section 39.

Note that when the load signal Pa is prioritized in the low value priority circuit 37, it is called speed-governing operation, and when the load limit value PL is prioritized, it is called load limit operation.

The final load signal P in the electronic turbine control device corresponds to the speed relay stroke in the MHG shown in FIG. The signal corresponds to the turbine rotation speed, and if the rate of change in the valve closing direction is greater than the dashpot operating point, the intercept valve equipped with a dashpot will cause the regulator valve 3 to change due to its dashpot characteristics. Before fully opening, it quickly closes along the dashed line A in FIG. As described above, the valve drive signal Sv is calculated based on the actual speed signal N indicating the turbine rotation speed, and the rate of change of the valve drive signal Sv in the valve closing direction corresponds to the rate of increase in the turbine rotation speed. Therefore, when the turbine speed increases above the dashpot operating point, the intercept valve closes abruptly to prevent turbine overspeed.

[Problem that the invention seeks to solve]

When the speed control means of a turbine equipped with an intercept valve with a dashpot is changed from a mechanical-hydraulic governor to an electro-hydraulic governor, the speed detection section and calculation section are electronic, and the MHG In this case, the response of the control signal corresponding to the speed relay becomes faster and the sensitivity becomes sharper, and in the MHG, the speed increase rate corresponding to the dashpot operating point is detected at an actual speed increase rate lower than the turbine actual speed increase rate. A valve drive signal Sv having a rate of change corresponding to the dashpot operating point is outputted,
There is a possibility that an unnecessary sudden closing operation of the intercept valve may be performed.

An object of the present invention is to provide an electronic turbine control device in which an intercept valve does not close suddenly below a predetermined turbine rotation rate of increase.

[Means to solve the problem]

The above problem is solved by a turbine control device for a steam turbine equipped with an intercept valve and its quick-closing mechanism. This is achieved by a turbine control device provided with a restriction release means.

[Effect]

The intercept valve opening signal rate of change limiting means limits the rate of change of the intercept valve opening signal due to changes in turbine rotational speed during normal operation to below a certain value that will not cause sudden closing of the intercept valve. If the change in turbine rotational speed exceeds a predetermined rate of change, such as when a load is cut off, the intercept valve opening signal change rate limit release means is activated and the limit is canceled, causing the valve to suddenly change. A valve drive signal that changes suddenly based on the opening signal is applied to the intercept valve, the quick closing mechanism is activated, and the intercept valve is suddenly closed.

〔Example〕

One embodiment of the present invention will be described with reference to FIGS. 1, 2A, 2B, and 3A-3F. In this embodiment, the final load signal is connected in series to the output side of a load distribution section that distributes the final load signal to the intercept valve. An intercept valve malfunction prevention circuit 50 is connected thereto. FIG. 1 shows details of the intercept valve malfunction prevention circuit 50.

This circuit is provided with a change rate limiting circuit 504 as an intercept valve opening signal change rate limiting means, does not limit the normal valve opening signal, and is designed to handle large If a signal is input, limit the signal.

Furthermore, when a load cutoff or the like occurs and the valve opening signal suddenly changes, the suddenly changed signal is output as is, and the dashpot mechanism of the intercept valve is operated to quickly close the intercept valve.

This circuit includes a change system limiting circuit 504 which is an intercept valve opening signal change rate limiting means connected in series to the output of the load distribution section, and a change rate limiting circuit 504 which constitutes an intercept valve opening signal change rate limit release means. One-shot circuit 503 and one-shot circuit 50 connected to limiting circuit 504
3, an acceleration detection circuit 5 connected to the OR circuit 502 and configured to detect and output turbine acceleration;
01, a subtracter 505 connected to the input side and output side of the rate-of-change limiting circuit 504, and an absolute value circuit 506 connected to the subtracter 505. and a comparator 507 connected to the absolute value circuit 506.

The output of the comparator 507 is input to the OR circuit 502.

In this embodiment, the above intercept valve malfunction prevention circuit 50
Other than that, it's the 51st! Since this is the same as the conventional example shown in I, the explanation of other parts will be omitted.

The change rate limiting circuit 504 outputs the input signal as it is when the change in the input valve opening degree signal is small as shown by the broken line l in FIG. 2A (FIG. 2B IA). When there is a change that causes the dashpot to operate as shown by the two-dot chain line 3.

The output is limited to a rate of change at which the dashpot does not operate (1-dot chain line 2A in FIG. 2B).

During normal operation, the above operation can prevent sudden closing of the intercept valve, but if you always set a rate of change limit, when it is necessary to close the intercept valve suddenly due to load shedding, etc.
Cannot close suddenly.

Next, the operation at load cutoff will be explained with reference to FIGS. 3A to 3F. When load shedding occurs, the turbine speed N increases rapidly, and the control signal obtained by multiplying the deviation amount ΔN from the set speed signal No by a gain corresponding to the speed regulation rate suddenly decreases. The valve opening degree signal outputted by calculating this control signal also suddenly changes in the valve closing direction.

At the same time, the acceleration detection circuit 501 detects that the acceleration 5 is higher than the set value.
is detected and a detection signal 6 is output to the one-shot circuit 503 via the OR circuit 502. The one-shot circuit 503 that has received the detection signal 6 outputs the limit release signal 7 to the change rate limit circuit 504 for a certain period of time, and
4 outputs the valve opening signal 8A that suddenly changes in the valve closing direction as it is while receiving the restriction release signal. As a result, the dashpot of the intercept valve, which receives the rapidly decreased valve drive signal, that is, the valve drive signal in the closing direction whose rate of change is greater than the value of the dashpot operating point, operates, causing the intercept valve to close rapidly and overload the turbine. Speed is prevented.

Furthermore, the valve opening degree signal input to the rate of change limiting circuit 504 and the output signal of the rate of change limiting circuit 504 are combined into a subtracter 505.
The difference between the output signal and the input valve opening signal is calculated and input to the comparator 507 through the absolute value circuit 506. Comparator 507 compares it with a preset value, and if the input difference value is large, OR circuit 502
A detection signal is output to the one-shot circuit 503 via the one-shot circuit 503. The operation after the detection signal is output to the one-shot circuit 503 is similar to the case where the detection signal is output from the acceleration detector described above.

In the above-mentioned embodiment, an intercept valve opening signal change rate limit release means based on acceleration detection and an intercept valve opening signal change rate limit release means based on the deviation between the valve opening signal and the output of the change rate limiting circuit are provided. Although an example has been shown, it is not necessarily necessary to provide both.

According to the above embodiment, the intercept valve opening degree signal that is calculated and outputted in accordance with the change in the rotational speed under normal turbine operating conditions is determined by the change rate limiting circuit at the operating point value of the dashpot of the intercept valve. Since the intercept valve is limited to (However, this value varies depending on the inertia of the rotating part of the turbine.), it is determined that load shedding has occurred, and the limiting operation of the rate of change limiting circuit is released. The input intercept valve opening signal, which has a large rate of change, is output as is, and the dashpot of the intercept valve is operated to quickly close the intercept valve, which prevents turbine overspeed and maintains operational safety. be done. As described above, according to this embodiment, an intercept valve equipped with a dashpot mechanism and an EHG can be combined and used safely.

〔Effect of the invention〕

According to the present invention, in a turbine control device for a steam turbine equipped with an intercept valve having a quick-closing mechanism, the means for controlling the opening of the intercept valve includes intercept valve opening signal change rate limiting means; Since it is equipped with a signal change rate limit release means, it is possible to prevent the intercept valve from closing suddenly during normal operation, and also to close it suddenly when the load is cut off.E-HG can be combined with an intercept valve with a quick-closing mechanism. This has the effect of increasing the safety of the control device.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an embodiment of the present invention, FIGS. 2A, 2B, and 3A to 3F are conceptual diagrams showing the operation of the embodiment of the present invention, and FIG. 4 is a diagram showing an intercept valve. 5 is a system diagram of a steam turbine equipped with a quick closing mechanism, FIG. 5 is a system diagram of a turbine control device according to the prior art, and FIG. 6 is a graph showing the operation of an intercept valve. 504...Intercept valve opening signal change rate limiting means (change rate limiting circuit), 501.502.503.5
05.506, 507...Intercept valve opening signal change rate limit release means (change rate limit release circuit)

Claims (1)

[Claims] 1. In a turbine control device for a steam turbine equipped with an intercept valve and its quick closing mechanism, the means for controlling the opening of the intercept valve includes intercept valve opening signal change rate limiting means and intercept valve opening signal change rate. 1. A turbine control device comprising rate limit release means.