Stand-alone microgrids

A hybrid power system (HPS) which consists of diesel Genset, PV-arrays and wind turbines with energy storing and power electronic devices is discussed in this paper. An inventory of different connection topologies is made for some of the sources that generate AC power and others that generate DC power. By comparative study on the system efficiency, the Mixed-coupled HPS is found to be the best layout and this layout is used for further investigation. By considering AC-load demand, solar irradiation and wind speed profiles of a typical site, the sizing approaches of the system elements are developed for the HPS. For the selected layout, eleven innovative Power Management Strategies (PMSs) are defined; and for each PMS, Mathematical models are derived based on the power balance between the supply and the demand sides, charging/discharging control of the battery and switching controls for the Genset. The different HPSs are modeled using MATLAB/Simulink blocks and simulation results are analyzed. The different PMSs result to different sizing of system elements, power sharing, fuel consumption & environmental impacts, and cycles of batteries in the lifetime of the system. Finally, the hybrid system of each PMS is investigated for its cost competitiveness and environmental impacts by taking the economical aspects and fuel consumption into consideration. It is found that RESs and/or HPSs are cost competitive over the system life, in spite of the huge initial capital costs, for the variable costs of the Genset overshadows its low initial capital investment.