Coordinate Control Of Boiler,Turbine And Grid For The Primary Frequency Regulation

The fluctuation of renewable energy leads to frequent adjustment of the supercritical unit, and affects the life and economy of the once-through boiler as well. A coordinated control method of boiler, turbine and grid is designed for the primary frequency regulation of supercritical unit, which contributes to both the life of the thermal unit and the frequency regulation of power system. This paper also verifies the applicability of this method in the power system.Firstly, models of once-through boiler, turbine and grid is proposed to analyze primary frequency regulation. Based on the differential equations of energy as well as mass and momentum, a mathematical model consisting of furnance and super heater is established in order to reflect the dynamic characteristic of once-through boiler. Based on the dynamic characteristics of turbine and its regulation system, a mathematical model of steam turbine is proposed to analyze primary frequency regulation. A frequency regulation model of power system including different type of turbine is also established in order to test the effect of this coordinate control method.Secondly, coordinated control strategy is designed according to the different states of boiler and grid. In order to harmonize the energy of boiler and grid, quantitative analysis of boiler energy and grid energy are carried out. Coordinated control strategy is then designed according to different frequency and main steam pressure. Simulation under different states of power system showed coordinated control method contributes to both main steam pressure and frequency of the grid.Finally, effect of the coordinated control method is analyzed in respect of the life of the boiler, the CPS value and the power flow. Life loss of boiler is closely related to the number of stress cycles, the coordinated control method brings about life increaments of furnace and superheater by about 3% and 7% respectively. Based on frequency regulation model of power system, the CPS value is calculated, the results show that the coordinated control method of boiler, turbine and grid improves the CPS value significantly. Simulation of power flow show that coordinated control of boiler as well as turbine and grid will not cause a serious impact on the power flow.