JP4459730B2 - Turbine speed control device and pulse modulation control circuit - Google Patents

Description

  The present invention relates to a speed control device for a turbine (BFP T: Boiler feed Pump Turbine) used for control of a feed water pump or the like for supplying water to a boiler of a thermal power plant, and particularly relates to improvement in controllability for increasing the turbine speed.

The turbine speed can be controlled by controlling the valve opening degree of the steam control valve that adjusts the amount of steam supplied to the turbine. A conventional turbine speed control apparatus will be described below.
First, a speed target value is set in the target speed setter. The actual speed setter outputs the output value of the target speed setter based on the output signal of the comparator that detects the magnitude of the output of the target speed setter and the actual speed setter and the OR condition of “startup” given from the outside. It operates so that it becomes the same output value. The output change speed of the actual speed setter at that time is given by the speed increase rate setter that determines the speed increase rate of the turbine. On the other hand, the actual rotational speed of the turbine is given to a speed detection circuit from a speed detector attached to the turbine shaft, and an output signal of the speed detection circuit is sent as a speed signal. The difference between the actual speed signal and the output signal of the actual speed setter is proportionally amplified or proportionally-integratedly amplified by an amplifier, and the valve opening degree of the steam control valve is controlled. Steam at a high temperature and high pressure is given to the inlet of the valve from the boiler, a turbine is connected to the outlet of the valve, and a generator or the like serving as a turbine load is connected to the turbine shaft. That is, the turbine speed is controlled by controlling the valve opening degree of the steam control valve (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 52-144504

  The conventional turbine speed control device adopts the above configuration, but in the case of turbine speed control by the valve opening control of the steam control valve such as BFPT, the governor motor that adjusts the valve opening of the steam control valve outputs The valve control hydraulic pressure signal and the opening / closing characteristics of the steam control valve are not proportional, especially when the turbine speed is increased during startup until the valve opening reaches the valve opening at which the adjustment of the steam amount is effective for the acceleration control. It takes time to get up. For this reason, the control signal is preceded by the time the turbine speed starts to increase, and an excessive speed increase signal is output to the steam control valve, and the turbine speed increases rapidly and exceeds the target speed to overshoot. However, there are problems such as convergence to the target speed and the time required for the adjustment.

The present invention has been made to solve the above-described problems, and it is an object of the present invention to obtain a turbine speed control device that improves the controllability of the turbine speed and can quickly converge to the target speed. Objective.
In addition, a pulse modulation control circuit suitable for such a turbine speed control device, that is, a pulse modulation control circuit capable of generating a pulse signal that quickly converges a variable to be controlled to a target value is provided. Is the second purpose.

  The turbine speed control device according to the present invention controls the valve opening degree of the regulating valve for the fluid supplied to the turbine so that the detected turbine speed follows the command signal. Using the deviation between the turbine speed detection signal and the command signal as an input signal, a pulse modulation circuit that outputs a pulse having a preset pulse width at a pulse interval that varies in inverse proportion to the input signal, and the set pulse width A prior auxiliary signal generating circuit for generating a signal having a larger pulse width, and a switching circuit for switching and selecting the output of the prior auxiliary signal generating circuit and the pulse modulation circuit to output a control signal for controlling the valve opening degree And a logic circuit for determining a switching condition in the switching circuit. Prior to selecting the output from the pulse modulation circuit as the control signal, the output from the preceding auxiliary signal circuit is selected as the control signal for a predetermined period determined by the logic circuit.

  The pulse modulation control circuit according to the present invention further includes a pulse modulation circuit that outputs a pulse having a preset pulse width at a pulse interval that varies in inverse proportion to the input signal, using the deviation between the command signal and the detection signal as an input signal. . Also, a preceding auxiliary signal generating circuit for generating a signal having a pulse width larger than the set pulse width, and a switching for selecting and outputting the output of the preceding auxiliary signal generating circuit and the pulse modulating circuit. A circuit and a logic circuit for determining a switching condition in the switching circuit. Prior to selecting the output from the pulse modulation circuit as the control signal, the output from the preceding auxiliary signal circuit is selected as the control signal for a predetermined period determined by the logic circuit.

  According to the turbine speed control device of the present invention, by using a signal having a large pulse width from the preceding auxiliary signal generation circuit prior to the output of the pulse modulation circuit, the valve opening characteristic and the rise of the turbine speed are accelerated, and the pulse An excessive pulse signal from the modulation circuit can be suppressed to quickly converge to the target speed, and the controllability of the turbine speed can be improved.

  In addition, according to the pulse modulation control circuit of the present invention, by using a signal having a large pulse width from the preceding auxiliary signal generation circuit prior to the output of the pulse modulation circuit, the rise of the variable to be controlled is accelerated and the pulse modulation is performed. An excessive pulse signal from the circuit can be suppressed and the controlled variable can be quickly converged to the target value, and the controlled variable can be controlled well.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below.
FIG. 1 is a diagram showing the structure of a turbine speed control apparatus according to Embodiment 1 of the present invention for a BFPT control apparatus.
As shown in FIG. 1, the BFPT control device controls the speed of a turbine 12 that controls a water supply pump 14 for supplying water from a water supply tank 13 to a boiler 15. The turbine 12 is arranged coaxially with the water supply pump 14. And the rotational speed of the turbine 12 is controlled by adjusting the amount of steam as a supply fluid supplied from the accumulator 11 to the turbine 12. The adjustment of the steam amount is performed by controlling the valve opening degree of the adjustment valve 10 as an adjustment valve with a valve control signal by a valve control hydraulic signal output from the valve adjustment motor 9.

A main circuit configuration for generating a valve control signal for controlling the speed of the turbine 12 will be described below.
As shown in the figure, a target speed setter 1, a speed increase rate setter 2, a speed command generation circuit 3, a speed detector 4 attached to the turbine shaft, a speed detection circuit 5, and a comparison circuit 6 are provided. Further, a pulse function module circuit 7 (Pulse function Module: hereinafter referred to as a PFM circuit 7) as a pulse modulation circuit, a preceding auxiliary signal generation circuit 71, a switching circuit 72, a switching condition logic circuit 61 and an amplifier 8 are provided, and valve adjustment is performed. The motor 9 receives the output signal from the amplifier 8 and outputs a valve control signal.

  The output from the target speed setter 1 and the output from the acceleration rate setter 2 are input to the speed command generation circuit 3, and the speed command generation circuit 3 outputs a rotational speed command for the turbine 12 as a speed command signal. This rotational speed command is an inclination signal when the speed is increased up to the target rotational speed, and then substantially reaches the target rotational speed. On the other hand, the actual rotational speed of the turbine 12 is given to the speed detection circuit 5 from the speed detector 4 attached to the turbine shaft, and the speed detection circuit 5 outputs a speed detection signal. The comparison circuit 6 inputs the rotational speed command from the speed command generation circuit 3 and the speed detection signal from the speed detection circuit 5 and outputs the deviation 6a.

  The PFM circuit 7 receives the deviation 6a from the comparison circuit 6 and outputs a pulse signal (PFM signal) having a preset pulse width and a pulse interval that varies inversely according to the deviation 6a. The pulse width in the pulse signal controls the driving time, and the pulse interval controls the non-driving time. The preceding auxiliary signal generating circuit 71 generates a preceding auxiliary signal having a pulse width larger than that of the PFM signal of the PFM circuit 7. The switching condition logic circuit 61 inputs the output from the target speed setter 1 as a start recognition signal for recognizing the start of the turbine 12, and outputs the deviation 6 a from the comparison circuit 6 and the speed detection signal from the speed detection circuit 5. As an input, a satisfaction condition signal is output while the deviation 6a is equal to or greater than a preset threshold value and the speed detection signal is equal to or less than a preset dark value from the time when the activation recognition signal is input. . The switching circuit 72 receives the PFM signal from the PFM circuit 7, the preceding auxiliary signal from the preceding auxiliary signal generating circuit 71, and the output from the switching condition logic circuit 61 as input, and the satisfaction condition signal is input from the switching condition logic circuit 61. During this time, the preceding auxiliary signal is selected and outputted, and when the input of the satisfaction condition signal is completed, the PFM signal is switched and outputted. A valve opening control signal 72 a output from the switching circuit 72 is amplified by the amplifier 8 and used as a control signal to the valve adjusting motor 9.

FIG. 2A shows the characteristics of the valve opening of the adjusting valve 10 and the actual rotational speed of the turbine 12 in such turbine speed control. As a comparative example, FIG. 2 (b) shows characteristics when control is performed using only the PFM signal as the valve opening control signal 72a without using the preceding auxiliary signal.
In this embodiment, a predetermined period determined by the switching condition logic circuit 61, that is, the turbine 12 is started and the speed is increased to some extent from the start of the acceleration, and the rotational speed command (the rotational speed command in the figure) is obtained. Until it approaches, the preceding auxiliary signal is used as the valve opening degree control signal 72a. The advance auxiliary signal may have a pulse width larger than that of the PFM signal, and may generate, for example, one to several continuous pulses that are continuous for a predetermined time. Number)).
Thereafter, the PFM signal is switched and selected by the switching circuit 72 and used as the valve opening degree control signal 72a. That is, after the deviation between the turbine speed and the rotational speed command becomes relatively small, a PFM signal output at a pulse interval that varies inversely according to the deviation is used as the valve opening degree control signal 72a. For this reason, it is possible to suppress an excessive output of the PFM signal serving as the valve opening degree control signal 72a, and it is possible to suppress overshoot exceeding the target speed (target rotational speed) and quickly converge to the target speed.

  On the other hand, in the comparative example in which only the PFM signal is used for the valve opening degree control signal 72a without using the preceding auxiliary signal, as shown in FIG. The PFM signal is output excessively due to the large deviation from the speed command. Since the pulse width of the PFM signal does not exceed the predetermined value, it is insufficient for improving the characteristics that the valve opening degree and the turbine speed rise slowly, and the target rotation speed is exceeded by the excessively output PFM signal. Overshoot becomes large and it takes time to converge to the target speed.

  As described above, in this embodiment, a signal having a large pulse width from the preceding auxiliary signal generation circuit 71 is used for the valve opening control signal 72a prior to the PFM signal, so that the valve opening characteristics and the rise of the turbine speed are increased. As a result, the overshoot can be suppressed and the target speed can be quickly converged, and the controllability of the turbine speed can be improved.

Note that the PFM circuit 7, the preceding auxiliary signal generation circuit 71, the switching circuit 72, and the switching condition logic circuit 61 used in the above embodiment may be configured integrally as a PFM control circuit 70 as shown in FIG. .
Further, in order to improve the controllability of the existing turbine speed control device using only the PFM signal as the valve opening control signal 72a, a preceding auxiliary signal generation circuit 71, a switching circuit 72 and a switching condition logic circuit 61 are added, and a new An integral PFM control circuit 70 may be used in the turbine speed control device.

  In addition, the PFM control circuit configured by the PFM circuit 7, the preceding auxiliary signal generation circuit 71, the switching circuit 72, and the switching condition logic circuit 61 is used in the BFPT control device in the above embodiment. The speed control of the device or a variable other than the speed may be controlled. By using a signal having a large pulse width from the preceding auxiliary signal generation circuit prior to the PFM signal, the rise of the variable to be controlled is accelerated. Overshoot can be suppressed and the target speed can be quickly converged.

It is a figure which shows the structure of the turbine speed control apparatus by Embodiment 1 of this invention. It is explanatory drawing of the control characteristic of the turbine speed control apparatus by Embodiment 1 of this invention. It is a figure which shows the structure of the turbine speed control apparatus by another example of Embodiment 1 of this invention.

Explanation of symbols

3 Speed command generation circuit, 4 Speed detector, 5 Speed detection circuit, 6 Comparison circuit,
6a deviation, 7 PFM circuit as pulse modulation circuit, 9 valve adjustment motor,
10 adjustment valve as adjustment valve, 12 turbine, 61 switching condition logic circuit,
71 Preliminary auxiliary signal generation circuit, 72 switching circuit, 71a Valve opening control signal.

Claims (4)

In a turbine speed control device that controls the valve opening degree of a regulating valve of a fluid supplied to the turbine so that the detected turbine speed follows the command signal, a deviation between the turbine speed detection signal and the command signal is calculated. A pulse modulation circuit that outputs a pulse having a preset pulse width as an input signal at a pulse interval that changes in inverse proportion to the input signal, and a preceding auxiliary signal generation that generates a signal having a pulse width larger than the preset pulse width. Circuit, a switching circuit for switching the output of the preceding auxiliary signal generation circuit and the pulse modulation circuit and outputting a control signal for controlling the valve opening, and a logic circuit for determining a switching condition in the switching circuit Prior to selecting the output from the pulse modulation circuit as the control signal, the preceding auxiliary signal for a predetermined period determined by the logic circuit Turbine speed control the output from the road and selects on the control signal. 2. The turbine speed control apparatus according to claim 1, wherein the predetermined period determined by the logic circuit is a predetermined period from the start of acceleration of the turbine by the start of the apparatus. 3. The turbine speed control according to claim 2, wherein the predetermined period is a period in which a detection signal of the turbine speed is equal to or less than a predetermined value, and a deviation between the detection signal and the command signal is equal to or greater than a predetermined value. apparatus. In a pulse modulation control circuit comprising a pulse modulation circuit that outputs a pulse having a preset pulse width at a pulse interval that varies inversely proportional to the input signal, using the deviation between the command signal and the detection signal as an input signal. A preceding auxiliary signal generating circuit for generating a signal having a pulse width larger than the pulse width, a switching circuit for switching and selecting outputs of the preceding auxiliary signal generating circuit and the pulse modulation circuit, and the switching circuit; And a logic circuit for determining a switching condition in step (b), and an output from the preceding auxiliary signal circuit for a predetermined period determined by the logic circuit prior to selecting an output from the pulse modulation circuit as the control signal. Is selected as the control signal.

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