JPH0442920B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal power plant control system, and particularly to a thermal power plant control system suitable for use in rapid and large-scale load addition operations.

FIG. 1 is a block diagram of a conventional thermal power plant control system.

The thermal power plant 3 is controlled by the boiler automatic control device APC 2 based on the load command L _D from the central power dispatch center 1 . Each operation amount u _i (i=1, 2,
...output r). This operation amount includes spray operation, turbine control valve operation, water supply pump operation,
There are fuel control valve operations, air damper operations, etc. Each controlled variable x _j (j=1, ₂ ,...
...l) The respective manipulated variables u _i are auxiliary controlled by the feedback control (steam temperature, steam pressure, etc.).

In a thermal power plant as shown in Figure 2, load commands include turbine steam flow rate, feed water flow rate, fuel flow rate, air flow rate, spray flow rate, gas recirculation flow rate, etc.
It is controlled according to L _D , and each adder output becomes the manipulated variable u _i . In addition, each control amount x _j is the frequency f, the amount of power generation
MW, main steam pressure P _MS , main steam temperature T _MS , gas oxygen amount O ₂ , and reheat steam temperature T _RH , and these are added to the load command L _D to become the manipulated variable.

By the way, each manipulated variable u _i has a response delay with respect to a change in the target value. In other words, there is a delay in the operation of the drive unit (for example, in coal-fired power generation, there is a delay in the crushing of coal, a delay in transporting pulverized coal, a delay in heat transfer, etc.), and therefore, it is difficult to respond to rapid and large changes in load command. Poor load followability and control amount
There is a problem that the fluctuation of x _j increases.

An object of the present invention is to provide a predictive control system for a thermal power plant that can perform accurate load following control by compensating for response delays in manipulated variables and has small fluctuations in controlled variables.

In order to achieve the above object, the present invention preliminarily calculates each manipulated variable related to response delay of a thermal power plant based on a load command from a central power dispatch center, outputs it to a thermal power plant, and provides a feed. In a thermal power plant predictive control system that is equipped with an arithmetic control means that performs forward control and also takes in a part of the control amount of the thermal power plant as a feedback amount and performs supplementary feedback control of each of the manipulated variables, A load prediction means for predicting a load command after a time corresponding to the response delay based on the load command and outputting the predicted load command to the calculation control means as a current load command is connected to the central power dispatch center and the calculation control means. This paper proposes a predictive control system for thermal power plants installed between

Since the dead time of each manipulated variable is generally different, the load prediction means predicts the load command for each manipulated variable after a time corresponding to the response delay of each manipulated variable, and uses each predicted load command as the current load command. If the load prediction means outputs to the arithmetic control means, more accurate predictive control becomes possible.

In the present invention, a predicted load means command that takes into account the dead time of each manipulated variable is input to the calculation control means as the current load command, and each manipulated variable is calculated to control the thermal power plant, so there is a delay in the response of each manipulated variable. can be compensated for, improving the load followability of thermal power plants and reducing fluctuations in controlled variables.

FIG. 3 is a block diagram showing an embodiment of the present invention.

Based on the time-series signal from the central power dispatch center 1 to the load command L _D , the load prediction system 4 predicts and calculates the load command L^ _D in the near future, and calculates this predicted load command L^ _D
Based on this, the APC 2 preliminarily manipulates each manipulated variable u _i of the thermal power plant 3, and additionally manipulates each manipulated variable u _i by feedback control of each controlled variable x _j .

The functions of the load prediction system 4 will be described in detail below.

An autoregressive moving average model is used to predict load commands. That is, the sampling period (ΔT)
The load command value L _D for the past M time points captured every time
(k), L _D (k-1), ..., L _D (k-M+1) and prediction error E _L (k), E _L (k-1), ..., E _L (k-M+1)
The load command L^ _D (k-1) after one sampling is predicted by the following equation using a linear combination of .

L^ _D (k+1)=a ₁ L _D (k)+a ₂ L _D (k-1)+...+
a _M L _D (k-M+1) +b ₁ E _L (k)+b ₂ E _L (k-1)+...b _M E _L (k-M
+1) ...(1) Here, E _L (k-i) = L _D (k-i) - L^ _D (k-
i) (i=0,1,2,...,M-1) L^ _D (k-i): 1 at time (k-i-1)
Predicted value of load command after sampling Also, predicted value of load command after 2 samplings
L _D (k+2) is calculated using equation (2).

L^ _D (k+2)=a ₁ L^ _D (k+1)+a ₂ L _D (k)+……+a _M
L _D (k-M+2) +b ₂ E _L (k)+b ₃ E _L (k-1)+...+b _M E _L (k-
M+2) ...(2) Similarly, the predicted value L^ _D (k+N) of the load command after N sampling is calculated using equation (3).

L^ _D (K+N)=a ₁ L^ _D (K+N-1)+a ₂ L^ _D (K+N
−
2) +... +a _N-1 L^ _D (k-1) +a _N L _D (k)+a _N+1 (k+1)+... +a _M L _D (k-M+N) +b _N E _L (k) +b _N+1 E _L (k-1)+... +b _M EL (k-M+N) = _N-1 〓 ⁱ⁼¹ a _i L^ _D (k+N-i)+ _M 〓 ^i=N a(one) L _D (k+N
-i) + _M 〓 ^i=N b ₁ E _L (k+N-i) ...(3) In this way, the predicted value of the load command after N samplings L^ _D (k+1), L^ _D (k+2) ,...,L^ _D (
k
+N) is required. Note that the coefficients a _i , b _i (i=1,
2,...,M) are determined by the least squares method using past load commands. Next, a method for determining the predicted time will be described.

The response of load L to changes in load command L _D is:
It can be approximated by the following formula.

L(S)=1/1+T・Se ^-L

Claims (1)

[Scope of Claims] 1. Based on a load command from a central power dispatch center, each manipulated variable related to response delay of a thermal power plant is calculated in advance and outputted to the thermal power plant for feed forward control. In the thermal power plant predictive control system, the thermal power plant predictive control system includes an arithmetic control means that takes in a part of the control amount of the thermal power plant as a feedback amount and performs auxiliary feedback control on each of the manipulated variables. The central power dispatch center and the arithmetic control means include a load prediction means that predicts a load command after a time corresponding to the response delay based on the response delay and outputs the predicted load command to the arithmetic and control means as a current load command. A thermal power plant predictive control system characterized by being installed between. 2. In claim 1, the load prediction means predicts the load command for each manipulated variable after a time corresponding to the response delay of each manipulated variable, and sets each predicted load command to the current load. A thermal power plant predictive control system, characterized in that it is a load prediction means that outputs a command to the arithmetic and control means.