Load Comparison Between Two Controlling Strategies for Wind Energy Conversion System Power-Boosting

Abstract

This paper explains in detail the development, validation and simulation of a standard PI controller that can boost the WECS (Wind energy conversion system) power through two strategies. In the first strategy, the power is boosted by increasing the generator angular velocity through the direct increase of the angular velocity of the wind turbine rotor by slightly pitching the blades. In the second strategy, the power is boosted by increasing the load torque of the generator, through the direct increase of the load torque of the wind turbine rotor. For achieving this goal, the following tasks have been accomplished: a wind energy conversion system nonlinear mathematical model has been developed, a gain scheduled proportional-integral (PI) controller as the baseline controller, and two gain scheduled proportional-integral (PI) power-boosting controllers for the two power-boosting strategies. For the power-boosting controllers, it is also presented a logic that switches between baseline and power booster controllers when certain wind speeds conditions are met. The response, stability, performance and the increase in the shaft torsion, tower and blades bending moments of the gain scheduled PI power-boosting controllers have been compared with the baseline controller. By comparing the output power response of the controllers, it can be seen that the power booster controllers boost the power when the defined conditions are met. Finally, for boosting the power of a WECS in certain conditions the most efficient way is by increasing the generator load torque, because this strategy increases the least the loading of the main components of a WECS. This power boosting strategy implementation it might require the change (or reinforcement) of the drive train shaft, if it cannot take the extra loading created by power boosting controller.