Abstract
Abstract
High Voltage Direct Current (HVDC) schemes are
becoming a more attractive solution as they have been used
extensively in interconnected weak power AC systems.
But, the problem of voltage stability for weak AC systems
interconnected by a DC link is critical especially during islanding
conditions. The approach to improve more on the stability of
such system would be to device a means of injecting locally
controlled dc power on the dc-link transmission corridor forming
a radial multi-terminal HVDC. However, continuous injection of
DC power on the dc line of the VSC HVDC link though will
increase the power transfer capability of the system but should
have a limit otherwise it will lead to instability of the system. In
this paper, a detailed VSC HVDC model and a simple analytical
technique using the principle of uniform loading to determine
penetration limit is presented. The techniques is applied to our
case study and validated with a simulation result.
Critical contingencies such as sudden island conditions, threephase
to ground fault are simulated with and without DC power
penetration. Results show the stability support on the AC side
networks by DC power injection on the dc-link.