A Novel Strategy for Sensorless Control Modification of a Six-phase Induction Generator in Faulted Mode

Abstract : Due to the limited operations of three-phase machines in open-phase fault conditions, the multiphase induction generators are now introduced in high-performance power generation systems. In the case of six-phase induction generators, the operation with opened phases is associated with torque and consequently power oscillations even in steady state conditions. Previous works have reported different methods to reduce these oscillations but they only deal with sensored control issues. Therefore, this paper deals with on-line modification of a sensorless control system applied to a squirrel cage six-phase induction generator (SC6PIG) when one to three phases of the machine are lost. Designing ten different off-line Luenberger speed observers as well as ten control systems corresponding to the different possible fault types and switching between them as a function of a detection system is proposed in this paper. Furthermore, on-line imposing of the nonzero initial conditions induces a smooth switching between the observers as well as the controllers with minimum associated transient at switching instants. The proposed strategy is tested on a wind turbine simulator driven by a permanent magnet dc motor. The experimental results in healthy and faulty modes assess the validity of the proposed strategy.