Simulation study of wind energy conversion systems

Abstract

The growing emphasis on renewable energy sources to replace nuclear and fossil fuel based resources has resulted in an increase in the use of wind energy systems. The diesel prices predicted to go on rising, adding wind power systems at its current cost instead of adding diesel still means cheaper power for consumers in the long run, at least until systems are operating with very large volume of wind. Wind energy, although clean and pollution free is distinguished from conventional energy sources by the variability of the sources of fuel. The intermittent nature of the wind causes the output power systems to vary significantly. The increasing penetration of the wind energy conversion systems into the power systems grid increases the effects of the wind power variations on the grid, causing voltage and frequency fluctuations. Thus, it becomes important to study the dynamic behaviors of various types of wind energy conversion systems to understand their effects on the power systems. The study describes the principle underlying the economic assessment of wind power systems. The present thesis compares three widely used control schemes for wind energy systems, pitches control, rotor resistance control and vector control of doubly fed induction generator and investigates studies their effectiveness in controlling the fluctuations in the output power occurring due to wind speed variations. The pitch control iv system is easy to implement, but the response is slow and the output power variation is large when the rotor resistance controller is used, it has been found that there are large power losses in the system at low wind speeds. The doubly fed induction generator has been found to be the best power control method with low losses and unity power factor operations. In doubly fed induction generator, control of rotor currents allows for adjustable speed operations and also reactive power control.