Planning considerations of HVDC link in power network

This paper presents planning considerations of HVDC link in a power network. Normally HVDC back to back links had been planned based on the criterions of asynchronous AC system interconnections earlier. In order to evacuate bulk power as more power generating stations have been added and also to provide fast power control, it becomes system requirements to put another point to point HVDC link in close proximity of existing back to back link. This paper presents an analysis for understanding the existing network interface which may have interactions in situations of inadequate system strength both at back to back and point to point HVDC links. It has been examined that any change being offered by new point to point HVDC link very closely connected with existing back to back may create an operational problem, if proper controller is not incorporated. The power transfer may also get affected which may lead to power swing in nearby AC network which is unacceptable from operational view point. A sample system comprising of back to back (monopolar) and point to point (bipolar) has been modelled in PSCAD/EMTDC environment and detailed study has been performed. This study may provide a guideline for system planners with many upcoming HVDC links in close proximity.