Control Strategy With High Flexibility Of Heating Unit

The large-scale integration of new energy sources such as wind power has resulted in insufficient peak regulation margin,which has impacted the operation of the power grid.In the northern region where wind energy resources are widely distributed in China,heating units are the main component of thermal power units,and the power grid almost entirely counts on heating units to provide the capacity of peak and frequency regulation.The serious coupling characteristics between generating load and heating load of heating units causes frequent fluctuations of generating load when the plants are adjusting heating load,which limits the load regulation range and rate of the plants,and it is not conducive to put the units into automatic generation control(AGC)operation.In order to improve the control quality of heating units,the coordinated control systems of units need to be optimized.Because of the large energy storage in hearing net,small fluctuations of heating load will often not affect heating users.Therefore,the main is to consider the decoupling of the generating load side.Around this issue,this article mainly carried out the following work:The structure and model of the thermal system of heating units was analyzed.Analyzing the structure of the thermal system of the heating unit,it is found that the thermal system structure determines the coupling characteristics between the control systems of generating load and heating load.Use the model of fuel flow-turbine governor valve opening-low pressure valve(LV)opening-extraction valve(EV)opening versus throttle pressure-generating load-medium pressure cylinder exhaust pressure-heating extarction flow for simulation analysis,which is built on the MATLAB/Simulink platform.The coupling characteristic was analyzed and the high flexibility control system was designed.The nonlinear dynamic model of the heating units is linearized with small deviations to obtain a linearized model in the form of transfer function.The model is built on the MATLAB/Simulink platform to compare the simulation experiment with the original model,and the simulation experiment proves that the linearized model has good reproducibility.The linear model is used to analyze the coupling characteristics of units,and it is found that the fluctuation of generating load caused by the adjustment of heating load is caused by the path from the LV valve opening and the EV valve opening to the generating load.Based on the coupling characteristics analysis results,using the feed-forward compensation method to design the decoupling link,two forms of decoupler are obtained.One of them is constructed by dynamic signal of throttle pressure and medium pressure cylinder exhaust pressure,and the other is constructed by static operating point parameters.Based on the operation point of 100% rated heating load,the two forms of decoupler are obtained.the high flexibility control system was verified by simulation.Perform simulation analysis on the pure condensing condition,manual heating condition and automatic heating condition of the traditional coordinated control system of heating units on the MATLAB/Simulink platform.Carry out the simulation analysis of the highly flexible control system after the decouplers is added.The results of simulation experiments show that the highly flexible control system can reduce the fluctuation amplitude of generating load caused by the LV valve opening step disturbance to 7.1% of the original amplitude,and reduce the fluctuation amplitude of generating load caused by the EV valve opening step disturbance to 11.3% of the original amplitude.Moreover,it is found that the decouplers constructed by dynamic signal of throttle pressure and medium pressure cylinder exhaust pressure has fewer fluctuations and smaller fluctuation amplitude,which has better dynamic characteristics.