JP2008131676A - Power plant load control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power plant load control system, capable of executing control with so good responsiveness that a turbine generator output faster reaches a target load. <P>SOLUTION: The load control system is provided with a change rate controller 2 for imposing a limit of change rate on a plant target load signal 1 and outputting a plant load command signal 3; a delay means 4 for applying delay to the plant load target signal 3 and outputting a turbine generator load command signal 5; a detecting means 21 for detecting that the plant load command signal 3 has reached the plant target load signal 1; a signal output means 23 for outputting a signal 24 following the plant target load signal 1 faster than the turbine generator load command signal 5 from the delay means 4; and a switching means 25 for switching the signal to the signal 24 to form a turbine generator load command signal 26 when the plant load command signal 3 reaches the plant target load signal 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a load control device for a power plant that generates power by driving a turbine generator with steam generated in a boiler.

 In this type of power plant, when the load command signal to the turbine generator is changed drastically, it is necessary to rapidly change the flow rate of steam generated from the boiler and introduced into the steam turbine. If it exceeds the change that can be followed on the boiler side, the disturbance to the boiler will be great, and control of each control loop on the boiler side including the steam temperature will become difficult, leading to instability of the plant.

 In particular, a coal-fired transformer boiler will be described as an example. In a power plant where the response speed of a boiler is slow, turbine power generation is performed using a circuit as shown in FIG. A method of giving a load command to the machine as a smooth signal is often adopted.

 That is, the plant target load signal 1 transmitted from the command unit 10 of the central power station is signaled to the load change rate determined for the plant (coal-fired transformer boiler and turbine generator) by the load change rate limiter (RL) 2. To obtain a plant load command signal 3 in which the rate of change of is limited. Although the load control of the boiler 11 is performed based on the plant load command signal 3, the plant load command signal 3 is not directly used as the load command for the turbine generator 12, but the first-order delay or higher-order delay means 4 is used. The generated signal is used as the turbine generator load command signal 5.

 FIG. 7 is a waveform diagram of various signals obtained by this control device, with the horizontal axis representing time and the vertical axis representing changes in the load command signal. In the figure, 1 ′ is the waveform of the plant target load signal 1, 3 ′ is the waveform of the plant load command signal 3, and 5 ′ is the waveform of the turbine generator load command signal 5. Further, t1 is a time when the change of the plant load command signal 3 is started by acquiring a new plant target load signal 1, t2 is a time when the plant load command signal 3 reaches the plant target load signal 1, and t3 is a turbine generator load. The time points when the command signal 5 reaches the plant target load signal 1 and the plant load command signal 3 are shown.

 As shown in this figure, the turbine generator load command signal waveform 5 'changes along a gentler curve than the plant load command signal waveform 3'. Since the output of the turbine generator 12 is controlled according to the turbine generator load command signal 5 having such a gentle waveform, the fluctuation of the steam flow extracted from the boiler 11 becomes gentle, and the boiler control is stabilized correspondingly.

Regarding the control device for the turbine generator, for example, the following patent documents can be cited.
JP-A-8-266095

 However, in the above-described load control device, the delay means 4 is operated to change the plant load command signal 3 (until the plant load command signal 3 starts changing and reaches the plant target load signal 1. That is, between t1 and t2, the turbine generator load command signal 5 has a waveform delayed from the plant load command signal 3 by a time corresponding to the time constant of the delay means 4.

 Further, after the plant load command signal 3 reaches the plant target load signal 1, that is, after t2, the transition is very slow, and it takes a long time for the turbine generator load command signal 5 to reach the plant target load signal 1. The response of the turbine generator output is slow. Since the purpose of the plant is to make the turbine generator output follow the plant target load quickly, such characteristics are very disadvantageous for the performance of the power plant.

 An object of the present invention is to provide a power plant load control device that solves such drawbacks of the prior art and achieves both a responsive control in which the turbine generator output quickly reaches the target load and a stability of the plant. There is.

In order to achieve the above object, the present invention is a power plant for obtaining a generator output by introducing steam generated in a boiler into a turbine generator,
A rate of change limiter that outputs a plant load command signal by adding a rate of change limit to the plant target load signal of the power plant, and
A delay means for outputting a turbine generator load command signal by causing a delay to act on the plant load command signal output from the change rate limiter, and the boiler load command signal not to act on the delay means. In the power plant load control device that outputs the output signal of the delay means to the turbine generator as a turbine generator load command signal.
Arrival detection means for detecting that the plant load command signal has reached the plant target load signal;
A target load post-arrival signal output means for outputting a target load post-arrival signal that follows the plant target load signal faster than the turbine generator load command signal obtained by applying a delay by the delay means;
Until the plant load command signal reaches the plant target load signal, the turbine generator load command signal output from the delay means is output to the turbine generator, and the arrival detection means generates the plant load command signal. When it is detected that the plant target load signal has been reached, the turbine generator load command signal is switched to the target load after-arrival signal, and the target load after-arrival signal is sent to the turbine generator. And a switching means.

 The present invention is configured as described above, and can provide a power plant load control device that achieves both responsive control in which the turbine generator output quickly reaches the target load and plant stability.

 Next, embodiments of the present invention will be described with reference to the drawings. 1 is a schematic system diagram of a power plant load control device according to an embodiment of the present invention, FIG. 2 is a waveform diagram of various signals obtained by the control device, and FIG. 3 is a specific system diagram of the power plant load control device. FIG. 4 is a waveform diagram of various signals obtained by this control apparatus.

 As shown in FIG. 1, a plant target load signal 1 transmitted from a command unit 10 of a central power station is a load determined by a change rate limiter (RL) 2 in a plant (a coal-fired transformer boiler and a turbine generator). A plant load command signal 3 in which the rate of change of the signal is limited to the rate of change is obtained. Although the load control of the coal fired transformer boiler 11 is performed based on the plant load command signal 3, the plant load command signal 3 is not directly used as a load command for the turbine generator 12, but is a first-order lag or higher-order lag means. 4 is used as the turbine generator load command signal 5. The configuration so far is the same as the prior art described with reference to FIG.

 In the present invention, the arrival detection circuit 21 detects that the plant load command signal 3 has reached the plant target load signal 1, and outputs the detection signal 22 to an analog switch (ASW) 25 serving as switching means. The load command to the turbine generator 12 after this detection time (see FIG. 2) does not use the turbine generator load command signal 5 obtained by the action of the delay means 4, but rather than the signal 5 Switching to the waveform signal 24 after reaching the target load outputted from the waveform forming circuit 23 that forms a waveform that quickly follows the plant load command signal 3 (selecting a by the ASW 25) is used as the turbine generator load command signal 26. . As a result, the time to reach the plant target load signal 1 (time t4, see FIG. 2) can be shortened.

 The load command to the turbine generator 12 before the plant load command signal 3 reaches the plant target load signal 1 uses the turbine generator load command signal 5 to which the delay means 4 is applied. The boiler 11 and the turbine generator 12 are coordinated at the start of the change and during the load change, and control with little disturbance to the boiler plant is ensured. That is, it is possible to realize control that achieves both load followability and plant stability.

 FIG. 3 is a system diagram more specifically showing the load control device according to the present embodiment. As shown in the figure, the output signal of the rate-of-change limiter 2 does not become the load command signal as it is, but the AFC command signal 51 and the frequency bias signal 53 are superimposed on the plant load command signal 3 by the signal addition processor 55. The post-addition load command signal 56 is used.

 The AFC (abbreviation of Automatic Frequency Control) command signal 51 is a signal given from the central power station for control to maintain and maintain the system frequency in the jurisdiction at a constant level (for example, 50 Hz or 60 Hz).

 The frequency bias signal 53 is a signal obtained by detecting the steam pressure at the turbine inlet, creating a pressure correction coefficient by a function generator based on the steam pressure at the turbine inlet, and multiplying the system frequency deviation by a multiplier. Thus, the signal is set so as to coincide with the power generation amount changed by the governor-free function.

 Generally, since the response to the AFC signal 51 and the frequency bias signal 53 is not allowed to be delayed, the signal component added here is not allowed to be delayed by the load command signal. Therefore, the signal component to which the delay means acts as the load command signal is the component of the output signal of the change rate limiter 2 (plant load command signal) before the signal component by the AFC signal 51 and the frequency bias signal 53 is superimposed. It is only necessary for 3).

 Therefore, a signal 58 obtained by subtracting the plant load command signal 3 not acting on the delay means by the subtractor 57 from the primary delay output signal 65 obtained by acting the primary delay means 64 on the plant load command signal 3 is used as the post-addition load command signal. 56 is added by the adder 63 so that only the component of the plant load command signal 3 before the AFC signal 51 and the frequency bias signal 53 are added is canceled in the output signal of the adder 63 as a result. Basic form.

 The output signal 58 of the subtractor 57 is obtained as a waveform 58 'shown in FIG. 4, that is, a signal waveform obtained by reversing the plus / minus of the signal obtained by incomplete differentiation of the plant load command signal 3. When the output signal 75 of the monitor relay 74 that detects that the plant load command signal 3 has reached the plant target load signal 1 is turned on, this signal is output from the signal generator 68 (setting value = 0). The signal 69 is switched by an analog switch (ASW) 59.

 The output signal 60 of the analog switch (ASW) 59 has a waveform 60 ′ shown in FIG. 4, and the change rate setting value signals 76 and 77 similar to those used in the change rate limiter 2 are used for the output signal 60. Then, the limiter output signal 62 in which the change rate is limited by the change rate limiter 61 has a waveform 62 ′ shown in FIG. The signal 76 is a change rate set value signal on the lower side, and a signal 77 is a change rate set value signal on the up side.

 When the limiter output signal 62 and the post-addition load command signal 56 are added by the adder 63, the waveform 26 'shown in FIG. 4 is obtained, and the load command signal that is the object of the present invention reaches the plant target load signal 1. At the same time, it is possible to obtain the turbine generator load command signal 26 in which the components of the AFC signal 51 and the frequency bias signal 53, which are not allowed to be delayed in operation, are added in the same waveform.

 The monitor relay output signal 75 for detecting that the plant load command signal 3 has reached the plant target load signal 1 is obtained by taking the derivative of the plant load command signal 3 with a differentiator 70 and calculating the absolute value of the output signal 71 as an absolute value. It is obtained by a value calculator (ABS) 72 and detected by the monitor relay 74 that the value of the output signal 73 is not more than a specified value.

 The reason why the output signal 67 of the function generator 66 is applied to the first-order lag or higher-order lag means 64 using the plant load command signal 3 as an input signal is that the response performance of the boiler changes depending on the plant load. In consideration of the command signal 3, the smoothness of the waveform of the turbine generator load command signal 26 can be adjusted.

 Therefore, the differentiator 70, the absolute value calculator (ABS) 72, and the monitor relay 74 constitute the arrival detection circuit 21 shown in FIG.

 The subtractor 57, the analog switch 59, the change rate limiter 61, the adder 63, and the signal generator 68 constitute the waveform forming circuit 23 shown in FIG.

  FIG. 5 is a diagram comparing the prior art and the turbine generator load command signal waveforms according to the present invention, with the horizontal axis representing time and the vertical axis representing the load command signal and the turbine generator load command signal.

  Assuming that the plant load command signal 3 is stable at 50% until the time t = 0 seconds, the conventional turbine generator load command signal 5 when the load is changed under the following conditions and the turbine according to the present invention: The response of the generator load command signal 26 is expressed by the following (1) and (2). The response waveform is shown in FIG.

従来技術によるタービン発電機負荷指令信号５の波形５’と本発明によるタービン発電機負荷指令信号２６の波形２６’を比較すると、ｔ＝４００秒までは同じであるが４００秒以降の応答が異なる。 Load change rate r = 3% / min. Load change width α = 20%
The first-order lag or higher-order lag means 4 with respect to the turbine generator load command is assumed to be a general first-order lag of T = 60 seconds in the past results.

Comparing the waveform 5 ′ of the turbine generator load command signal 5 according to the prior art and the waveform 26 ′ of the turbine generator load command signal 26 according to the present invention, the response is the same up to t = 400 seconds but the response after 400 seconds is different. .

  In other words, the turbine generator load command signal 5 according to the prior art slowly reaches the target value of 70% (shown by a solid line) as a characteristic of the first-order lag waveform, but the turbine generator load command signal 26 according to the present invention is used. If so, the target value 70% is reached as it is at a rate of 3% / min along the extended line of the waveform at t <400 seconds (indicated by a broken line).

  As a result, when the time for the turbine generator load command to reach the target value 70% is compared with the time t = 400 seconds from which the plant load command 3 reaches the target value 70%, the conventional technology delays 205 seconds. On the other hand, in the present invention, the delay is shortened to 60 seconds. However, since it takes an infinite time to reach 70% just due to the nature of the first-order lag waveform, it is assumed that it has reached 0.1% or 69.9%.

  From another point of view, if the load change rate during this period is expressed as load change width / required time to target load, the conventional turbine generator load command signal 5 of 1.98% / min and the plant load command signal 3 While the load change rate is greatly reduced from 3% / min, the turbine generator load command signal 26 according to the present invention can be improved to 2.61% / min.

  Although what has been described here relates to the turbine generator load command, the ultimate target generator output itself of the power plant is controlled in a manner that substantially follows this command value. The improvement of the characteristics is directly connected to the improvement of the response characteristics of the generator output as the power plant.

1 is a schematic system diagram of a power plant load control device according to an embodiment of the present invention. It is a wave form diagram of various signals obtained with this control device. It is a specific systematic diagram of this power plant load control device. It is a wave form diagram of various signals obtained with this control device. It is a figure which compares and shows the prior art and the turbine generator load command signal waveform by this invention. It is a schematic system diagram of a conventional power plant load control device. It is a wave form diagram of various signals obtained with this control device.

Explanation of symbols

  1: Plant target load signal, 1 ′: Plant target load signal waveform, 2: Change rate limiter, 3: Plant load command signal, 3 ′: Plant load command signal waveform, 4: Delay means, 5: Turbine generator load Command signal, 5 ′: Turbine generator load command signal waveform, 10: Command unit, 11: Boiler, 12: Turbine generator, 21: Arrival detection circuit, 22: Arrival detection signal, 23: Waveform formation circuit, 24: Target Waveform signal after reaching load, 25: analog switch, 26: turbine generator load command signal, 26 ': turbine generator load command signal waveform, 51: AFC command signal, 53: frequency bias signal, 55: signal addition processing unit, 56: Load command signal after addition, 56 ′: Load command signal waveform after addition, 57: Subtractor, 58: Subtractor output signal, 58 ′: Subtractor output signal waveform, 59: Analog switch 60: Analog switch output signal, 60 ′: Analog switch output signal waveform, 61: Change rate limiter, 62: Limiter output signal, 62 ′: Limiter output signal waveform, 63: Adder, 64: Delay means 65: Delay means output signal 66: Function generator 67: Function generator output signal 68: Signal generator 69: Signal generator output signal 70: Differentiator 71: Differentiator output signal 72 Absolute value calculator, 73: Absolute value calculator output signal, 74: Monitor relay, 75: Monitor relay output signal, 76: Decreasing side change rate set value signal, 77: Ascending side change rate set value signal.

Claims (1)

A power plant that obtains generator output by introducing steam generated in a boiler into a turbine generator,
A rate of change limiter that outputs a plant load command signal by adding a rate of change limit to the plant target load signal of the power plant, and
A delay means for outputting a turbine generator load command signal by causing a delay to act on the plant load command signal output from the change rate limiter, and the boiler load command signal not to act on the delay means. In the power plant load control device that outputs the output signal of the delay means to the turbine generator as a turbine generator load command signal.
Arrival detection means for detecting that the plant load command signal has reached the plant target load signal;
A target load post-arrival signal output means for outputting a target load post-arrival signal that follows the plant target load signal faster than the turbine generator load command signal obtained by applying a delay by the delay means;
Until the plant load command signal reaches the plant target load signal, the turbine generator load command signal output from the delay means is output to the turbine generator, and the arrival detection means generates the plant load command signal. When it is detected that the plant target load signal has been reached, the turbine generator load command signal is switched to the signal after reaching the target load, and the signal after reaching the target load is sent to the turbine generator. A power plant load control device comprising: a switching means.

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