The control strategy for grid-side converter of DFIG under asymmetrical voltage swell

Abstract

This paper aims to study the control strategy of grid side converter (GSC) of DFIG under asymmetrical voltage swell. Asymmetrical high voltage swell may cause significant fluctuations across the DC voltage and energy reflux of the GSC, even results in the runaway of the GSC. Firstly, the mathematical model of GSC is established. Afterwards, negative sequence current is derived on the suppression of the double fluctuations in DC voltage. On the above basis, the controllability of GSC is analyzed. When the grid voltage asymmetry swells to a certain extent, in order to make the GSC return to controllable range, the modulation index closed loop control strategy is used to compensate inductive reactive power. The effectiveness of proposed control strategy for GSC during grid voltage asymmetrical swell is validated by the simulated results.