Modeling and Control Improvement of a DFIG Based Wind Farm with VSC-HVDC Link

This paper presents modeling and stability enhancement of a Doubly Fed Induction Generator (DFIG) based Offshore Wind Farm (OWF) connected to the main grid by a Voltage Source Converter based High Voltage Direct Current (VSC-HVDC) link. Firstly, the whole system with common control strategies is modeled in synchronous reference frame. The wind farm is represented by a single equivalent DFIG model. Then, modal analysis is carried out to identify various oscillation modes in the system. It's found that certain modes near synchronous frequency have great influence on the system stability, while the performance of ordinary control shames found in the literatures is not perfect in some cases. Therefore, a power system stabilizer (PSS) attached to the DFIG is proposed to enhance the system stability. The results from both eigenvalue analysis and time domain simulation studies show the effectiveness of the proposed control improvement.