Stability Analysis of a Hybrid Multi-Infeed HVdc System Connected Between Two Offshore Wind Farms and Two Power Grids

This paper presents the stability simulation results of two equivalent aggregated offshore wind farms (OWFs) based on doubly-fed induction generator fed to two power grids through a hybrid multi-infeed high voltage dc (HVdc) system. The hybrid multi-infeed HVdc system consists of a line-commutated converter (LCC)-based HVdc link and a voltage-source converter-based HVdc link. A static synchronous compensator (STATCOM) is connected at the rectifier station of the LCC-based HVdc link. A unified approach using a pole-assignment approach based on a modal control theory is employed to design the damping controllers for the two HVdc links, respectively. Steady-state results under different wind speeds of the two OWFs are carried out. Comparative dynamic responses of the studied system with and without the designed damping controllers for the two HVdc links under wind-speed changes are also achieved. Comparative transient simulations of the studied system with and without the STATCOM subject to a three-phase fault are also performed.