A Novel Super-twisting Algorithm-based Direct Power Control Strategy for Doubly Fed Induction Generator

For both balanced and unbalanced grid voltage conditions, this paper proposes a direct power control (DPC) scheme for doubly fed induction generator (DFIG) based on second-order sliding mode super-twisting algorithm. Firstly, DFIG model under two-phase stator stationary reference frame is presented and power analysis for unbalanced grid condition is carried out in detail. Second-order sliding mode DPC strategy is then designed to improve dynamic performance and restrain current harmonic. System stability is analyzed based on Lyapunov method and control parameters ranges for finite time stability are accordingly deduced. For unbalanced grid voltage condition, while reserving the excellent control characteristics of second-order sliding mode DPC strategy, a flexible reference power compensation method is employed and the compensation values can be fast switched according to different operation objectives. Synchronous rotation coordinate transformation and current loop control are needless during the realization process of the proposed control strategy which simplifies the system structure. Simulation results for a 2.0MW DFIG verify the effectiveness of the proposed super-twisting algorithm based DPC scheme for both balanced and unbalanced grid voltage conditions.