Research On Optimization Control For Heating Units Under The Condition Of Large-Scale Integration Of Wind Power

Because of the large-scale integration of the wind power units, the uncertainty of wind power generation load can cause lots of fluctuations in the grid. The ability of peak regulation and frequency regulation of the units in the regional power grid determines the capacity of the wind power integrated into the grid. The thermal power units are the inevitable choice for compensating wind power load in the current Chinese grid. The ability of peak regulation and frequency regulation of the dominant subcritical units and supercritical units with positive pressure direct blowing pulverizing system can not satisfied the requirement of the grid. By comparing the characteristics of different types of thermal power units, it was discovered that the circulating fluidized bed units have high ability of peak regulation and low ability of frequency regulation; moreover, the heating units have high ability of frequency regulation and low ability of peak regulation. The circulating fluidized bed units coordinating with the heating units can resolve this problem.The chemical energy of coal was transformed to electrical energy in the thermal power units. The transforming process is very slow. For improving the load response rate of the units, the energy storage of the units must be fully used. The heating units supply the heat load for a certain area, and the pipeline of the heating network has the huge capacity of energy storage. By using the energy storage of the pipeline, the heating units can response the load disturbance of the grid in the small time scale. Directed by above train of thought, the researches were carried out as follows:1. Based on the analysis on the double inputs and double outputs model of power generation load-throttle pressure versus boiler fuel flow-turbine governor valve opening for pure condensation unit, by improving the energy balance link in turbine, and by adding the output of extraction steam pressure and the input of extraction control butterfly valve opening, the simplified nonlinear dynamic model of typical heating units was constructed with the differential equation. For a typical300MW heating unit with certain model parameters, the accuracy of the model was confirmed by the disturbance experiments. The nonlinear model was linearized over specified operation point, and the transfer function matrix was gained to describe the relation between inputs and outputs.2. The control systems of existing heating units under different operation conditions were simulated. The inner reason why the extraction steam flow can be maintained stable by controlling the extraction steam pressure in heating units was explained. The problems such as operation point nonlinearity, heating demand disturbance, uncertainty of heat storage coefficient and instability of coal calorific value were analyzed. Comparing the influence degree on control quality, designing suitable extraction steam flow compensation, designing heat released signal guidance differential control structure and coal calorific value compensation scheme, the result can provide the critical technical support for automatic generation control (AGC) of the heating units integrated in grid and primary frequency regulation.3. A union scheduling scheme for wind power and thermal power under the condition of large-scale integration of wind power was presented. The nonlinear filter was designed to decomposing the load instruction of AGC. And the load instruction appropriated for heating units was constructed. By comparing the advantages and disadvantages of different control schemes, the traditional coordinated control scheme with feedforward and compensation was adopted. The scheme can adapt to the changes of object characteristics under different heating demands and can also ensure the stability of the throttle pressure and heating demands. So the heating network energy storage can be used effectively and the load response rate of the units can be improved greatly. And the undisturbed switching between the heating operation condition and non-heating operation condition was realized.The engineering application characteristics were analyzed by exploiting the simulation experiment platform. According to the typical grid environment, the feasibility of the scheme was verified in a real unit. The research results can provide theoretical and fundamental technology support for the large-scale application on high-speed and varying load operation in heating units.