Power Limitation at High Wind Speed for a Variable Speed Fixed Pitch Wind  Turbine using Close-Loop Scalar Control

Authors

This paper represents the speed regulation for a

fixed pitch stall-regulated variable speed wind energy

conversion system. The speed regulation in the high (above

rated) wind speeds 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 maintain

the generated power by reducing the power coefficient from the

peak of Cp curve. It can be achieved by reducing the tip speed

ratio from the optimum value when wind speed vary from rated

wind speed to cut-out wind speed. Therefore, closed-loop

scalar speed control with the concept of constant ratio of

voltage/frequency was being applied. In addition, simple

algorithms of drive train and squirrel cage induction generator

were being 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 maintain constant

power by restraining the rotational speed corresponding to the

wind speed variation at the rated wind speed.