Reference-Governor-Based Power-Electronic Converter Control for Weak-Grid DFIG Offshore Wind Farms

Abstract

Power-electronic converter control is a key issue in the weak-grid integration of doubly fed induction generator (DFIG)-based offshore wind farms. In conventional fixed-reference DFIG control, the rotor-side power command is usually treated as a tracking target, although its suitability may change with the present point of common coupling (PCC) voltage and phase-angle condition. This paper proposes a weak-grid dynamic sensitivity-based model reference governor (WG-DSMRG) for DFIG offshore wind-farm converter control. The governor is inserted upstream of the RSC power-reference path, while the conventional RSC/GSC current controllers, phase-locked loop (PLL), coordinate transformations, and modulation structure are retained. The short-horizon relation between wind-farm power variation and PCC voltage-angle response is estimated from measured electrical signals. The RSC power command is then corrected through weak-grid scheduling and converter-capability projection. A 60-MW offshore DFIG wind farm connected to a weak AC grid is tested under an upstream voltage sag and a PCC single-line-to-ground fault. In the tested cases, the PCC reactive-power peak decreases from about 3.5 Mvar to 2.5 Mvar, and the DC-link voltage peak is reduced under both disturbances. The evaluated PCC voltage and current THD values are also lower with the proposed controller. These results show that reference-layer correction can improve weak-grid integration and power quality without replacing the established DFIG converter-control platform.