Speed sensorless control of a PMSG for small wind turbine systems

Wind turbine systems (WTS) based on permanent magnet synchronous generators (PMSG) have been gaining more and more importance over the last years. In fact, these generators are self-excited, allowing operation at high power factor and high efficiency. Additionally, the elimination of the gearbox allows a reduction in costs and maintenance. To further reduce the system complexity and the maintenance process, sensors normally used to sense the speed of these generators could be eliminated. This aspect is particularly important for wind turbine installation in harsh environment characterized by extreme weather conditions. To this purpose this paper investigates how a phase locked loop (PLL) can be profitably used to estimate the rotor speed. A systematic analysis is presented as well as simulation and experimental results proving the feasibility of such solution.