A Predictive Voltage Control Scheme For A Variable Speed Doubly Fed Induction Generator

Abstract

The study presents an effective predictive voltage control (PVC) scheme for a variable speed DFIG. The implementation of the PVC is articulated on a unique cost-function which concerns with the error minimization between the desired and actual rotor voltages. Thus, the cost function does not contain any estimated terms as implemented in the model predictive direct torque control (MP DTC) procedure. Moreover, there is no need to use a weighting scale (wf) in the proposed cost function which avoided the problems that can arise when using in accurate value of wf. The reference voltages are generated using two PI rotor current regulators which are designed and explained in details. The rotor voltages are applied to the rotor terminals using the finite set mechanism which enables the voltage vectors selection from a specified set of eight vectors, which facilitates the termination of the PWM modulator. To test the applicability of the proposed PVC for the DFIG, an accurate comparison is performed amongst the designed PVC and MP DTC algorithms. The test results approve that the DFIG dynamics are noticeably improved when applying the proposed PVC scheme and this is confirmed by the reduced ripples in the controlled variables and reduced switching actions of the rotor side inverter as well.