Research On Energy Storage Characteristic And Flexibility Control Of Thermal Power Plant

The integration of large-scale renewable energy has been a serious realistic problem to our country’s electric power grid.The improvement of coal-fired thermal power unit operating flexibility is an effective and necessary way to the solution of renewable energy integration.The core of thermal unit operating flexibility lies in the rapidity and depth of unit load regulation performance.Conventional thermal units have the load regulation ability in a certain extent,however the rapidity and depth of load regulation process can hardly meet the requirement of power grid peak load and frequency regulation.The conception of thermal unit energy storage utilization offers the possibility of further improvement on unit rapid load regulation performance.In this thesis the analysis of energy storage characteristic and control of multiple energy storage are researched to solve the thermal unit operating flexibility issue.The following works have been carried out in this thesis:1.Research on flexibile operating ability of coordinated control system in unit.The main energy storage links in thermal unit are classified and the possibility of their utilization for participating in the improvement of unit operating flexibility is analyzed.The boiler system,regenerative system and heat supply system energy storage are assigned to be the effective energy storage links.The subcritical unit nonlinear model is built by using combined modeling method.A soft measure method on boiler energy based on flue gas oxygen content and a boiler storage coefficient mechanism calculation method are presented to analyze the characteristic of boiler system energy storage.On the basis of characteristic and disadvantage analysis of existing coordinated control methods,a multiple predictive control method based on dynamic matrix control is designed to optimize the unit coordinated control system,which improves the control effect of operation parameters in load regulation process,and lay the foundation of multiple energy storage participating in load regulation control.2.Research of thermal unit operating flexibility control based on regenerative system energy storage.On the basis of regenerative system characteristic analysis,condensate throttling is assigned to be the control method of regenerative system energy storage utilization.The condensate throttling system nonlinear model is built through regenerative thermodynamic analysis,and the power capability and storage capacity of condensate throttling system are calculated quantitatively.A condensate throttling participating in AGC load regulation method based on boiler energy compensation is presented and modified to implement on a 330MW unit.The unit control performance and grid adaptation is verified by the source-grid combined dispatch control simulation system.A condensate throttling participating in primary frequency control method based on frequency load command decomposition is presented to optimize the operating parameters’ performance in primary frequency regulation process.3.Research of thermal unit operating flexibility control based on heat supply system energy storage.On the basis of heat supply system characteristic analysis,heat extraction throttling is assigned to be the control method of heat supply system energy storage utilization.The heat extraction throttling system nonlinear model is built through considering heat extraction in turbine energy balance.The power capability of heat extraction throttling system are calculated using equivalent enthalpy drop method,and the storage capacity of heat extraction throttling system is analyzed in consideration of heat grid load.Heat extraction throttling is designed to participating in AGC load control and unit operating stability control to realize the utilization of heat supply system energy storage.The effect of heat extraction throttling on performance of unit dynamic response is verified by simulation.4.Research on thermal unit energy storage combined utilization control system.To achieve the goal of multiple energy storage participating in improving the thermal unit operating flexibility,a global optimizing strategy of thermal unit load quick response based on multiple energy storage combined utilization is presented.a multiple energy storage management system is built,with the AGC load command decomposing and rebuilding by signal stratified decomposing method,and energy storage command generating based on energy storage integrated index.The energy storage systems are controlled accurately based on the nonlinear model feedback,and the state of the systems are estimated online.The AGC performance index and operating parameters’ control performance are evaluated in the simulation verification of the optimizing system.Research conclusion shows that the thermal unit load quick response control strategy based on multiple energy storage combined dispatching can realize the accurate control of energy storage system and coordination of multiple energy storage in unit’s AGC load response process.Though the research the improvement of unit load regulation performance is achieved in the precondition of stable operating,which provides fundamental theory and pivotal technique support to coal-fired thermal power unit flexible rapidity operation control system design.