A new direct slip-position estimator MRAS self-sensing control method for application on the DFIG connected to a DC network trough a diode rectifier on the stator circuits

This paper presents a new self-sensing method for the direct estimation of the slip position angle in the DFIG connected to a dc network. This connection is made by the stator through a diode bridge and by the rotor through a single voltage source inverter. Considerable savings are obtained when this system is used in networks where several systems should work together, because only a dc-link is needed. Additionally to the slip position estimation, required to implement field orientation, it is also necessary to control the stator frequency because the system is connected to a dc link, and consequently the mains do not impose the stator frequency as in the traditional DFIG. The slip angle estimation method is based on the MRAS methodology and compares the stator current amplitude with the q-axis rotor current component computed using the estimation angle. Small estimation errors are obtained using this method.