Dynamic analysis of a variable speed wind turbine equipped with a voltage source AC/DC/AC converter interface and a reactive current control loop

In this paper the analysis of the dynamic behavior of a variable speed wind turbine (VSWT) is presented. Comparison between variable speed and constant speed (CS) mode of operation is also performed. The examined wind turbine is equipped with a dual PWM voltage source converter cascade and connected to an electrical network represented by the Thevenin equivalent. Conventional scalar control is applied to the electrical generator, employing the constant V/f principle. Furthermore, the grid side inverter is assumed capable of regulating its output reactive power in order to maintain the voltage within permissible variations. The objective is to point out some of the advantages of the variable speed (VS) operation, such as the improved output power quality, the decrease of the mechanical stresses and the capability of controlling the voltage of the local grid.