Condition Monitoring And Optimization Of Control System For Heating Units Under Deep Peak Load Regulation

With the promotion of national energy policy,renewable energy is developing rapidly in China.With a large number of renewable energy connected to the grid,the grid system is facing increasingly prominent peak load regulation pressure.The power supply structure of our country leads to the peak load regulation pressure of the grid system can only be borne by the thermal power unit.The proportion of heating units in North China is relatively high.In the heating season,the operation mode of "power by heat" will further increase the peak load regulation pressure of the system,so it has become a trend to carry out flexible transformation of the heating unit to improve the space of wind power consumption of the system.This paper focuses on the zero output technology of low pressure cylinder of heating unit,the peak regulation depth of zero output transformation,the monitoring of important parameters and the control strategy of the cooling steam control system are analyzed and studied.At present,the main methods of flexibility transformation of heating units are electric boiler with thermal energy storage,heat storage tanks,zero output of low pressure cylinder and other transformation methods.Zero output transformation of low pressure cylinder has the advantages of low cost,flexible operation and high potential.Based on the method of off design calculation and heat balance calculation and Ebsilon simulation software,the load output of a certain LPS subcritical unit and a KBS supercritical unit is calculated and analyzed under the condition of zero output.Determine the peak regulation depth of zero output technology of low pressure cylinder.The zero output technology of low pressure cylinder can greatly reduce the load output of the unit,improve the capacity of the unit to participate in the deep peak load regulation,conform to the existing peak load regulation policy,and make the unit obtain the peak load regulation price compensation.The zero output technology of low pressure cylinder makes the operation condition of the unit deviate from the design condition greatly.The monitoring of various state parameters is of great significance for the safe operation of the unit.In the process of unit switching to zero output condition and in zero output condition,the original connecting pipe of low and medium pressure cylinder may have steam flowing into the low pressure cylinder.The measurement of steam flow at the flow measurement point may deviate from the actual steam flow into the low pressure cylinder.Therefore,the soft measurement method is studied to monitor the steam flow into the low pressure cylinder.Based on the mechanism analysis,the soft sensing model of low-pressure cylinder’s inlet steam flow is constructed.The static method has high accuracy for the calculation of inlet steam flow under steady-state condition,and the dynamic method has fast dynamic response speed.The soft sensing signal with both static accuracy and dynamic characteristics can be obtained by using frequency complementary method,to realize the online monitoring of low pressure cylinder’s inlet steam flow after zero output transiformation.The control of the exhaust temperature of the low pressure cylinder affects the safe operation of the unit,so the characteristics of the exhaust temperature object should be analyzed first.The influencing factors,dynamic and static characteristics of exhaust steam temperature under zero output condition are analyzed,and the control strategy of cooling steam control system is designed.Exhaust temperature of low pressure cylinder is controlled by cooling steam flow and desuperheating water flow.Because the coupling degree of inlet steam flow and desuperheating water flow to exhaust steam temperature is small,two independent circuits are designed to establish the control system of exhaust steam temperature.Through the simulation analysis of the designed control system by Simulink software,the effectiveness of the control strategy is verified.