Design And Implementation Of Advanced Control Strategy For Gas Power Plant Boiler

Gas power plant boiler is the important thermal equipment in self-generation power plant of steel enterprise.It not only consumes extra blast furnace gas,but also converts gas into electric energy in order to utilize for enterprise.At present,Distributed Control System(DCS)is usually applied to gas power plant boiler control system in owned power plant.Because of the complexity of the boiler system,the conventional PID control effect is poor in DCS.In order to improve control quality of the relevant loops,the gas power plant boiler is treated as research object in this dissertation.A set of advanced control system is designed and implemented,and it successfully applied to the field.The research and development work of this dissertation is mainly composed of three parts:1.Considering the characteristics of large inertia,lager time-delay and slow time-varying in main steam temperature,we use the recursive least squares method to indentify model of superheater.Then,a cascade control strategy based on indentified model of main steam temperature-desuperheater has been designed.Stair-like Generalized Predictive Control(SGPC)strategy is implemented to controller of major,and PID is used as controller of minor loop.2.Due to the lack of branch flow detection equipment,it is difficult to determine ratio of between air flow and gas flow(air-fuel ratio).For this problem,the air-fuel ratio is replaced by ratio of opening degree between air and gas regulator.Firstly,the neural network is applied to establish the relationship model between furnace temperature and air-fuel ratio.Secondly,particle swarm optimization algorithm is used to find the ratio of opening degree regulator of air-gas in upper and lower.Under adaptive fuzzy control process of oxygen content of flue gas,the result is regarded as air-fuel ratio reference value in order to provide datum point for change of air valve,achieving air-fuel ratio optimization.3.In order to overcome the influence of gas pressure change on furnace negative pressure and oxygen content of flue gas,PID controller has been designed to adjust furnace negative pressure.In addition,gas pressure and blower opening have been introduced as feed-forward.Fuzzy controller has been designed and implemented to adjust oxygen content of flue gas,and dynamically adjust quantization and scale factor strategies to adapt to changing working conditions.Moreover,the control of air pressure has been designed to assist the control loop of oxygen content of flue gas.4.With the help of existing hardware foundation on field,advanced control system platform for gas power plant boiler is designed and implemented,and graph user interface is designed,and communication connection test of OPC is completed,and the parameters of controller are tuned.The development of advanced control system has been put into engineering application,and the overall automation level of the boiler has been improved.Result of application shows that the quality of circuits control is significantly improved and the energy efficiency of the system is enhanced.