Stalling region instability compensation for constant power soft stalling control

Small scale VAWTs are valuable due to their ability of capturing wind from different directions without using a yaw; this simplifies the design and gives the turbine the tolerance to turbulence in urban areas. One difficulty with VAWTs is their control at excessive wind velocities to prevent the turbine from over speeding and electrical components from overloading. This paper presents analysis and controller design for a constant power soft stalling strategy at high wind velocities for a vertical axis wind turbine (VAWT) driving a permanent magnet generator. The constant power soft stalling control method suggests controlling the system so that the turbine operates in the stall region with the power kept constant. This paper discusses the system analysis, and the controller design. The proposed controller tends to stabilize the nonlinear system at the stalling region, and to eliminate excessive power fluctuations.