Sensorless adaptive observer of wind synchronous generator

Controlling electrical drives without mechanical sensors at the machine shaft has several benefits e.g. low cost and high reliability. To avoid these sensors, state observers must be resorted to get the required information using only measured voltages and currents at the machine terminals. In this paper we are considering the problem of estimating mechanical state variables in permanent magnet synchronous generators driven by wind turbines through AC/DC rectifiers and DC/AC inverters. Only the electrical variables are supposed to be accessible to measurements. Then a sensorless interconnected adaptive observer of the high-gain type is designed to get online estimates of the rotor position and speed as well as the load torque. Parameter adaptation is resorted because the load torque is not supposed to be known. The proposed state observer is formally proved to be globally convergent if its gains are conveniently chosen. This theoretical result is confirmed by simulations which, besides, show that the observer convergence is quite robust with respect to wind speed (or load torque) uncertainties.