Sensorless Control of Doubly Fed Induction Generators Based on Rotor High-Frequency Signal Injection

Abstract

High frequency signal injection based methods have been widely investigated for sensorless position/speed control of induction machines (IMs), permanent magnet synchronous machines (PMSMs) and more recently for doubly fed induction generators (DFIGs). When used with IMs and PMSMs, the high frequency signal is injected in the stator windings, an asymmetric (salient) rotor being required for this case. Contrary to this, both stator and rotor terminals are accessible and sensored in DFIGs, being therefore possible to inject the high frequency signal either in the stator or the rotor terminals. As consequence of this, the method can be used even if the machine is non-salient. In the implementation of the method with DFIGs, the high frequency voltage signal is typically injected in the rotor, the high frequency components (voltages of currents) induced in the stator being used for rotor position estimation. A drawback of this alternative is that the method is sensitive to the grid impedance in the stator side, which will be affected by the grid configuration, and is normally unknown. This paper proposes the sensorless control a DFIG injecting the high frequency voltage in the stator side, and using a high frequency current cancellation strategy in the rotor side. The main advantage of the proposed strategy is that the estimated position is independent of the grid characteristics. 1Index Terms -DFIG, high frequency signal injection, sensorless control.

Sensorless control of doubly-fed induction generators based on rotor high frequency signal injection

“…Compared to previously published high frequency signal injection based methods [6,18], the proposed method shows a reduced sensitivity to machine and grid parameters variation.…”

“…where is the stator resistance, is the rotor resistance referred to the stator (5), is the stator leakage inductance, is the rotor leakage inductance referred to the stator (6), is the magnetizing inductance, is the stator current complex vector, is the rotor current complex vector referred to the stator (7), is the stator voltage complex vector and is the rotor voltage complex vector referred to the stator (8), is the rotor resistance, is the rotor voltage complex vector, is the rotor current complex vector, is the stator number of turns, is the rotor number of turns. The transformation from three-phase quantities to qd quantities is given by (9).…”

“…Among the various types of grid connected wind turbines, the DFIGs are the more extended in on-shore applications, accounting for around of 50% of the installed wind turbines all over the world [4]. DFIGs have some appealing properties compared with other types of grid connected wind turbines: four quadrant active and reactive power capabilities; a fractional power converter compared to the machine rating (≈30%), a certain ride through capability and operation above and below synchronous speed [1,[5][6][7].…”

Sensorless control of doubly-fed induction generators based on stator high frequency signal injection

“…(8) (9) where is the stator resistance, is the rotor resistance referred to the stator (5), is the stator leakage inductance, is the rotor leakage inductance referred to the stator (6), is the magnetizing inductance, is the stator current complex vector, is the rotor current complex vector referred to the stator (7), is the stator voltage complex vector and is the rotor voltage complex vector referred to the stator (8), is the rotor resistance, is the rotor voltage complex vector, is the rotor current complex vector, is the stator number of turns, is the rotor number of turns. The transformation from three-phase quantities to qd quantities is given by (9).…”

“…Among the various types of grid connected wind turbines, the DFIGs are the more extended in on-shore applications, accounting for around of 50% of the installed wind turbines all over the world [4]. DFIGs have some appealing properties compared with other types of grid connected wind turbines: four quadrant active and reactive power capabilities; a fractional power converter compared to the machine rating (≈30%), a certain ride trough capability and operation above and below synchronous speed [1,[5][6][7].…”