SPEED CONTROL AT LOW WIND SPEEDS FOR A VARIABLE SPEED FIXED PITCH WIND TURBINE

摘要

This paper represents the speed regulation tor a iixed pitch stall-regulated variable speed wind energy conversion system. The speed regulation in the low wind speeds (below rated) region is the main topic of this paper where in this region, the rotor/generator speed activity is controlled by using the concept of adjustable or variable speed drive (ASD/VSD). Speeds need to be controlled in order to obtain maximum power by keeping the power coefficient at the peak curve by maintaining the tip speed ratio at the optimum value. To achieve this, the closed-loop scalar speed control with the concept of constant ratio of voltage/frequency is applied. Yet, simple algorithms of drive train and squirrel cage induction generator are used. A proportional integral (PI) controller was used to control the generator slip speed. Results demonstrate that such a closed-loop scalar control with proportional integral (PI) controller is good enough to accurately track maximum power at the optimum rotational speed corresponding to the wind speeds variation below the rated wind speed.