Sensorless control of doubly-fed induction generators based on stator 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.

Stator Flux Based Model Reference Adaptive Observers for Rotor Position and Speed Estimation in Doubly-Fed Induction Machines

“…There are several advantages for sensorless rotor position estimation such as lower cost, lesser maintenance, and higher reliability [5]. Most sensorless methods are based on either Model Reference Adaptive Observers (MRAO) [5]- [9] or Phase Locked Loops (PLL) [10] or high frequency signal injection [11], [12]. A speed sensorless method for control of DFIG without flux estimation can be found in [13].…”