Research On Frequency Regulation Of Regional Power System Including Air Cooling Units

With the rapid development of power industry, the number of steam turbines oflarge capacity increases, which consumes not only a lot of primary energy but also alot of water resources as well. Water scarcity is the major problem that the world isfacing currently and our country has been listed as one of13water-poor countriesby the United Nations. As air cooling units use cooling air as the cooling medium,the water volume saved by power plants using air cooling technology reaches over65%. Therefore, air cooling units have broad prospects for development andapplication in the northwest regions which are rich in coal and lack water. Under thepolicy guidance, the construction of air cooling units in China has entered a rapiddevelopment period and there have been an increasing number of air-cooling unitsput into operation. However, the heat exchange process of an air cooling unit takesplace in a surface heat exchanger and the backpressure of air cooling condenser willbe greatly affected by environmental factors. Air cooling unit’s generating abilitywill be greatly restricted at high backpressure, thus affecting the power generatedand the frequency of the grid. In the past, this problem wasn’t taken seriously forthere wasn’t much air cooling units connected to the grid. As more and more aircooling units are connected to the grid, to ensure the safe and stable operation ofregional power grid, the study of frequency regulation problem of regional powergrid including air cooling units is needed.Firstly, the meteorological information of the location of air cooling units canbe obtained by processing the weather forecast data using GRIDDATA interpolation.Then the model of regional power grid including air cooling units is constructed bythe mechanism modeling method and identification method on the basis of previousresearch. The model is divided into nonlinear model which is used for simulation inthe time domain and linear model which is used for analysis in the frequencydomain. The simulation in the time domain is the simulation of frequency regulationprocess under the conditions of changing environment temperature and face velocityof cooling air. The analysis in the frequency domain is the analysis of the effects ofenvironment temperature, face velocity of cooling air and power proportion of aircooling unit on the frequency characteristics of regional power systems byobserving the bode diagram of primary frequency regulation and secondaryfrequency regulation. To further quantitatively study the environmental factors’effects on the performances of frequency regulation of regional power grid, theprimary and secondary frequency regulation ability are defined and the analyticalformulas are obtained. By changing the environmental temperature, face velocity of cooling air and power proportion of air cooling units in the power grid, the effects ofthese factors on frequency regulation ability of regional power grid is studied. Theprimary frequency regulation process of regional power grid under specialconditions is simulated in the time domain using Matlab/Simulink software, fromwhich the maximum capacity of air cooling unit connecting to the grid and theminimum value of frequency regulation ability can be evaluated.Finally, the methods to improve the performances of regional power systemincluding air cooling units are proposed, such as dispatching according to numericalweather forecast and change the opening of steam stop valve, the validity of whichare erified by the simulation in the time domain.The research is financed by The National Key Basic Research Program ofChina (973Program)(NO.2012CB215201), The Natural Science Foundation ofChina (NO.51107014) and The National High Technology Research andDevelopment Program (863Program)(NO.2011AA05A105).