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.

Improved Super Twisting Based High Order Direct Power Sliding Mode Control of a Connected DFIG Variable Speed Wind Turbine

“…According to the above, the output reference of the rotor voltage is expressed as [14,35]: The expression of the super twisting output laws does not depend on the value of ( S, Ṡ ), but only of their signs. Fig.…”

“…The high order sliding mode approach presents another typical effective solution to eliminate the chattering problem, by keeping the same first-order sliding mode behaviors, especially the convergence properties and the control accuracy [13]. The super-twisting algorithm is an exception in a class of second-order sliding mode control, it can reduce chattering problems due to the discontinuity of the control signal [14].…”

Assessment of a PLL‐ASMO position/speed estimator for sensor‐less control of rotor‐tied DFIG (RDFIG)

“…Thus, the saliency‐based estimation methods are mostly suitable for standstill and start‐up operating conditions. The model‐based estimation techniques are used to estimate the rotor speed/position based on the machine model at the fundamental frequency and they are mostly used for medium‐speed and high‐speed applications [10–32]. The model‐based estimation techniques are generally grouped into two categories: the open loop calculations and closed loop observers.…”

“…Another SMO‐based estimator, the super twisting sliding mode observer (STSMO), is proposed for the sensor‐less control of the RDFIG in ref. [31], whereby it was shown that the use of the super twisting algorithm (STA) improves the performance of the proposed position/speed estimator.…”

“…In refs. [25,[30][31][32], in the implementation of the SMObased estimators, the estimated rotor speed is calculated using the arc-tangent function. The noise and the harmonics created by the switching of the sliding mode functions might alter the estimation performance.…”