Optimization Of DCS Control Rules In Coal-fired Power Station

At present,electric power of our country mainly rely on the coal-fired generating set.This trend will not change for a long time.In power system,unit power plants with great power and big parameters have been widely used.It is required that the unit is able to set react to the load demand quickly,perform safely,stably and economically at the same time.The unit can be considered as a two-input-two-output system,which are interdependent and coupled greatly.The inputs are the combustion of boiler and the valve opening of turbine,and the outputs are main steam pressure of the boiler and the power from the generator.There is a contradiction between rapidly and stability of the unit.Therefore,it's essential for us to optimize parameters to solve this contradiction.This paper introduces the fundamental automatic control systems in #5 Unit of Yangliuqing Power Plant,including coordinated control,combustion control,boiler-feedwater control,main-steam temperature control,bypass control,and RUNBACK system.Fundamental control rules and key issues in practical production are discussed and optimized,and the result is analyzed.The safety,the stability and the economical efficiency of the whole unit are improved as a result.Firstly,rules of coordinated control system are studied in this paper.To solve key issues,such as poor control accuracy in load,fluctuation of main steam pressure,optimize the coordination control rules,and analyzes the results.Secondly,the control rules of combustion are studied and optimized to solve problems,such as big inertia,deviate from the design types of coal,etc.Thirdly,the feed water control rules are studied and optimized to solve problems,for example,it's easy to over temperature for the big inertia of feed water system,feed water is unable to start automatically,and there are blind areas in steam pump and electric pump,etc.The rules of the main steam temperature control are optimized to solve the problem that the steam temperature is too low or too high sometimes.Experiment results show that the the steam temperature is controlled well.Finally,the bypass control system and RUNBACK system are studied to ensure the safety of the unit.Bypass control system can be used to solve problems,such as mismatches between the boiler and the turbine of large intermediate reheat unit.RUNBACK system keeps the air fuel ratio and water fuel ratio at a stable level after important auxiliaries tripping,and disturbance of the unit can be quickly eliminated,the safety and stability of the unit is be able to ensure as a result.