AbstractsEngineering

This master thesis studies the flexibility of Swedish power system. Because of the increase of fuel price and the environmental issues, renewable energy plays an increasingly important role. Sweden parliament has a planning frame of 30 TWh wind power energy per year in 2020. Wind power generation is largely dependent of wind speed. Since wind speed varies all the time and is hard to be predicted, the introduction of wind power will cause variation of power generation which needs to be balanced. Therefore, it is very important to study the regulation capacity of the power system in order to balance wind power. In Sweden, it is hydropower and thermal power that plays the role as balancing power. In earlier studies at Department of Electric Power Systems KTH, a model has been built to examine the flexibility of Swedish hydropower system. The aim of this thesis is to further develop this original model. In the improved model, the flexibility of thermal power in Sweden is included. Moreover, the improved model further considers the future value of stored water and the impact of delayed running water released from the upstream power plants at the end of simulated week. The whole model is a large short-time planning problem and the objective of this model is to maximize the profits. In this thesis, the profit is expressed as the future value of hydropower minus the generation cost of thermal unit. Besides, the profit also includes the income and the cost for the trading energy. The improved model is built as an optimization problem in GAMS. The time step is one hour and the time span of each simulation is one week. The load consumption and wind power production in each area are given as time series. The constraints considered in this model include the generation limitations, operational constraints of thermal power plants, hydrological coupling of hydropower plants, load balance in each bidding area and transmission capacity. Several case studies are performed in this thesis. Two models, both original model and improved model, will be tested. To find out how large the regulation capacity the Swedish power system has, four different expansion levels of wind power: 0 MW, 4000 MW, 8000 MW and 12000 MW are introduced. The information regarding hydropower is obtained from statistic data in 2009 and the wind power data for each week is coming from scaling the data in earlier studies. The operational constraints of thermal power plants are based on the statistics data from 2008 to 2012. The main finding from these case studies is that spillage will not increase when more wind power is introduced to the system but only increase when the export capacity is reached and the surplus power cannot be exported to other countries. Therefore, it can be concluded that the Swedish power system has good possibilities to balance large amounts of wind…