Intermittent control method for eliminating static deviation of main steam pressure of fossil fuel fired power unit

Abstract

The invention discloses an intermittent control method for eliminating static deviation of main steam pressure of a fossil fuel fired power unit, which includes the steps: monitoring the static deviation of the main steam pressure of the fossil fuel fired power unit in real time; and when the static deviation of the main steam pressure exceeds a specified value, making use of the step output characteristic of a derivative control module to adjust fuel quantity of a boiler based on an original boiler fuel quantity instruction by means of the intermittent rapid superposition of fuel quantity instruction offset corresponding to the static deviation of the main steam pressure, thereby eliminating the static deviation of the main steam pressure of the unit. By the method, the static deviation of the main steam pressure of the fossil power unit can be monitored in real time, and when the static deviation of the main steam pressure exceeds the specified value, the fuel quantity of the boiler can be adjusted timely by means of the intermittent rapid superposition of fuel quantity instruction offset corresponding to the static deviation of the main steam pressure, so that the static deviation of the main steam pressure of the unit can be eliminated quickly, and the precision of controlling the main steam pressure of the unit is improved effectively.

Description

technical field [0001] The invention relates to an intermittent control method for quickly eliminating the static deviation of the main steam pressure of a thermal power unit, in particular to a method for using the step output characteristic of the differential control module, based on the original boiler fuel quantity command, through intermittent rapid superposition and The fuel quantity command offset corresponding to the steam pressure static deviation, and the advanced control method of adjusting the boiler fuel quantity in time to quickly eliminate the static deviation of the main steam pressure of the unit belong to the field of thermal power engineering and automatic control. Background technique [0002] The load control system of the boiler is one of the most important control systems for regulating the load and stabilizing the operation of the unit in the thermal power plant. It mainly includes the boiler main control circuit and the fuel control circuit. In the ...

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Problems solved by technology

Since the influence of boiler coal supply on the main steam pressure is a controlled process with large inertia and large lag (the pure lag is about 120 seconds, and the inertia time is about 1000 seconds), so in order to ensure the stability of the boiler load control system, the PID The integral action in the regulator can only be obtained very small (for a large inertia process, a large integral action will cause the instability of the control system), and the integral time is often more than 400 seconds

On the other hand, the static deviation of main steam pressure (P 0 -P T ) is often only about (0.1-0.3) Mpa, the input deviation of the PID regulator is very small, and the small integral action often makes the ability of the boiler load control system to eliminate the static difference of steam pressure very poor. In part of the time, there is always a static deviation of steam pressure that is difficult to eliminate, especially for direct-blowing subcritical units such as 300MW units that are in large numbers in China, where there is always a static difference in steam pressure.

At present, there have been no reports on methods and control schemes that use other effective methods to eliminate the static difference of steam pressure to improve the control accuracy.

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