Study of the control structure of a small wind turbine with permanent magnet synchronous generator

Abstract

This paper presents the analysis of the two control structures used in wind generation systems with permanent magnet synchronous generators, variable speed and fixed pitch, to determine which structure is most appropriate for implementation. These control structures are speed control and torque control. The analysis considers all the elements of wind power generation system, with greater emphasis on the model of the turbine where mechanical torque is considered as a system variable and not as in other studies where it is considered as internal disturbance in the system. The analysis is developed so that the control structure is independent of AC/DC converter that is used in the system. From the analysis is obtained that the speed control can be stable using classical control techniques because it is a nonminimum phase system and the torque control is unstable because it has poles and zeros in the right half plane, very low frequency and very close to each other, so it is very difficult to control using classical control theory. In the evaluation of the speed control structure, the AC/DC converter is Three-phase rectifier Boost in Discontinuous Conduction Mode with an input filter and a Peak Current Control and to avoid the need of mechanical sensors, a Linear Kalman Filter has been chosen to estimate the generator speed.