Evaluation of an STSMO‐based estimator for power control of rotor‐tied DFIG systems

Abstract

In this study, a sensorless vector control strategy of a rotor-tied doubly fed induction generator (RDFIG) system based on the association of the phase-locked loop (PLL) estimator and the super-twisting sliding mode observer (STSMO) is proposed and analysed. The proposed sensorless control strategy utilises the stator current and the back-electromotive force (EMF) as state variables. The advantage of the proposed sensorless control strategy is that the estimation process is conducted before the machine is connected to the grid. The slip angle/speed is extracted from the estimated back-EMF space vector by using a PLL. The parameters of the STSMO are selected such that the Lyapunov stability criteria are fulfilled and that fast response is achieved. The robustness of the proposed position/speed sensorless control strategy is validated through steady state and dynamic experimental measurements on a 5.5 kW custom-designed grid-connected mode RDFIG test bench based on a National Instruments PXIe-8115 controller.