Abstract
This paper proposes a power control method to improve a stability of a small-scale power grid with renewable energy sources. In an isolated small- scale power grid such as an island, diesel power plant is main power source which has an environmental burden and expensive running cost due to high priced fossil fuel. Thus, expanding installation of the renewable energy sources such as a wind power is strongly desirable. Such fluctuating energy sources, however, harm power quality of the small-scale power grid, and in addition, conventional power plant in the small-scale power grid cannot, in general, stabilize the grid system with such fluctuating power sources. In this study, Variable Speed Doubly-Fed Induction Generator (VS-DFIG) is proposed to be in-stalled at a diesel power plant instead of a conventional Fixed Speed Synchronous Generator (FS-SG), because quick control of a power balance in the small-scale power grid can be achieved by using the inertial energy of VS-DFIG. In addition, utilization of a Battery Energy Storage System (BESS) is also considered to assist cooperatively the VS-DFIG control. As a result of the simulation analysis by using the proposed method, it is verified that frequency fluctuations due to renewable energy source can be effectively reduced by quick power control of the VS-DFIG compared to the conventional FS-SG, and further control ability can be obtained by utilizing BESS. Moreover, the transient stability of a small-scale power grid during a grid fault can also be enhanced.
Highlights
Utilization of renewable energy is spreading worldwide, especially energy conversion from solar and wind energy to electric power is most prevalent form for using renewable energy
This paper proposes a new strategy to enhance the controllability of the main generator in a small-scale power grid by adopting the Variable Speed Doubly-Fed Induction Generator (VS-DFIG), and it will be possible to introduce further renewable energy sources to small-scale power grid with the proposed VS-DFIG based diesel power plant
The variable speed diesel generator is proposed to control the grid frequency fluctuations of a small-scale power grid and its performance is evaluated through simulation analyses
Summary
Utilization of renewable energy is spreading worldwide, especially energy conversion from solar and wind energy to electric power is most prevalent form for using renewable energy. There is little report in which detailed analyses of the small power system including the diesel power plant and wind power station with natural fluctuating wind condition as a renewable energy source are performed with considering their cooperative control system. A new design and operation method of small-scale power grid is proposed in order to improve stability of the system frequency against fluctuating power from the wind power station, in which a variable speed diesel generator with employing Variable Speed Doubly-Fed Induction Generator (VS-DFIG) is adopted and controlled cooperatively with a Battery Energy Storage System (BESS). The simulation analysis in this paper is performed by PSCAD/EMTDC
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