Enhancement of the System Stability of DB-Controlled VSC Links Parallel Operated with a Weak Multi-Machine AC Power System

Abstract

To allow the large-scale integration of renewable energy sources into the grid, VSC-HVDC is commonly utilized. However, with greater integration, several power system stability issues arise. In this study, we examined the small-signal rotor angle stability of a model of the Australian power system with embedded VSC-based HVDC links. A simplified model of the Australian power network was used to connect the potential geothermal resources in the region of Innamincka using a 1100 km HVDC link. We observed that the introduction of the new source of geothermal power generation had an adverse impact on the damping performance of the system. Therefore, two forms of stabilization are examined here: (i) generator power system stabilizers (PSS) fitted to the synchronous machines, which are used to convert geothermal energy to electrical power; and (ii) power oscillation damping controllers (PODs) fitted to the VSC-HVDC link. In the case of the PODs, two types of stabilizing input signals are considered: (i) local signals such as power flow in adjacent AC lines, and (ii) wide-area signals such as bus voltage angles at key nodes in the various regions of the system. It was concluded that the small-signal rotor angle stability of the interconnected AC/DC system can be greatly enhanced by employing the designed damping controllers.