Research On Engineering Control Method Of Non-balanced Thermal Object

With the large-scale integration of renewable energy sources such as wind power and photovoltaic,the strong randomness and fluctuation of its power generation load have seriously affected the security and stability of the power grid.In China,thermal power units are still the main force.In order to provide more consumption space for new energy grid connection,the flexibility of thermal power units operation needs to be improved.The core lies in expanding the power generation load regulation range of thermal power units and increasing the power generation load regulation rate of thermal power units.In the process frequent and large fluctuations in the load of the units cause the control effect of the drum water level,deaerator water level,heating network heater water level,and high and low refilling water levels to deteriorate.Through analysis,it is found that the phenomenon of "false water level" is the main cause of the poor water level control effect.Research based on drum water level: through mechanism analysis,a simplified non-linear model of the object is established.Quantitative analysis of the "false water level" by calculating the amount of change in the vaporization or liquefaction volume ratio of the working fluid when the pressure changes under constant enthalpy.The results show that the amplitude of the water level of the steam drum is greater under ultra-low load.At the same time,the control characteristics of non-balanced thermal objects are analyzed.Due to the integration,static errors will be generated under partial disturbances.After eliminating the static errors,the system will become a second-order indifference system under constant value disturbances.Feedback control can not achieve the ideal control effect.Regarding the drum water level,the cascade three impulse control scheme cannot eliminate the "false water level".Based on the quantitative analysis of pressure changes and false water levels,the improvement of the control scheme for the drum water level is optimized.The pressure differential feedforward control is added with the cascade three impulse.By simulation comparison between cascade three impulse control scheme and pressure differential feedforward control scheme.The results show that the pressure differential feedforward control scheme can effectively overcome the “false water level” of the drum water level,and has good control effect in the adaptability.The pressure differential feedforward control is applied to the units.This control scheme can effectively overcome the "false water level" of the drum water level,deaerator water level,heating network heater water level,and high and low water supply levels,and achieve good control results.