Optimal Control Structure for Variable Speed wind Power System
Dată
2002Autor
Cutululis, Nicolaos Antonio
Munteanu, Iulian
Ceangă, Emil
Culea, Mihai
Abstract
This paper presents an optimal control structure for variable speed, fixed pitch
wind turbine. The control objective results from the optimization criterion that includes
two contradictory demands: maximization of the energy captured from the wind and
minimization of the damage caused by mechanical fatigue. We admit, as a modeling
assumption, that wind speed has two components: a slowly varying component, named
seasonal and a rapidly varying component, named turbulence. Hence, two control
structures, which should function simultaneously, are identified in the optimal control
problem.
The first optimization structure aims to maximize the wind turbine energetic efficiency
by maintaining operational point on optimal regime characteristics (ORC). According to
the slowly varying seasonal component of wind speed, a control loop adjusts system
operating point in order to maintain it on ORC. In the second optimization structure, the
system is considered to be operating on “static” optimal point assured by the above
mentioned control loop, with the turbulence component being the input variable. The
second control loop aims dynamic optimization that implies the minimization of the tip
speed ratio variations around its optimal value, while minimizing the torque variations,
thus the mechanical stress. Mathematically, this objective is defined as an integral
criterion, belonging to linear quadratic optimization.