Reliability Assessment of Wind-Diesel Hybrid System

Wind-Diesel Hybrid Power Systems are of interest to remote areas for power needs. They are preferred in remote area power systems as they have a reduced fuel consumption which leads to lower cost and lesser green house emissions. Besides, the hybrid combination needs lesser fuel storage requirements than a system consisting of a only conventional diesel generator sets. However the intermittent characteristics of wind energy seriously affect the reliability of wind diesel hybrid systems. Hence it is a matter of research interest to determine the adequacy levels for such schemes. In this paper an attempt has been made to evaluate Energy Index of Reliability (EIR) which is express as a function of Expected Energy Not Supplied (EENS) using Wind-Diesel hybrid System consisting of one or more wind and diesel genset units. This will help in arriving at the most suitable schemes having expectable level of adequacy. designed wind speed prediction model in the Monte Carlo simulation can lead to very reliable results coming from large amount calculation time on sequential simulation. In (6) the authors demonstrate a model of constrained wind generation output below a certain ratio of system load considering conventional generation and load at the same time. In the time frame approach (7), discrete wind speeds are applied to wind turbine power output function with the probabilities of discrete speeds based on the Weibull distribution to model wind turbine generator (WTG). A short term system reliability index can then be obtained by associating this model with load duration curves within each discrete frame. In this paper, an attempt is made to evaluate a reliability index called the Energy Index of Reliability (EIR). This index is obtained in terms of another reliability index Expected Energy Not Supplied (EENS) and the load demand for the area, being supplied by the hybrid system. The scheme proposed for the study consists of variable mix of wind turbines and diesel generators. The basic scheme is shown in Figure 1. The number of wind and diesel units can be varied.