In order to strengthen the onshore transmission network in many parts of the world, VSC HVDC will increasingly be utilized. The effect of the operating point of a VSC HVDC link and the control strategies employed can substantially affect the electromechanical oscillatory behavior of the AC network as well as the DC side dynamics. In order that the full, flexible capability of VSC HVDC can be exploited, further study of the effects of these controllers and their interactions with AC system responses is necessary. This paper addresses this gap. Both modal analysis and transient stability analysis are used to highlight tradeoffs between candidate VSC-HVDC power controllers and to study the electromechanical performance of the integrated AC/DC model. Tests are carried out on both a generic two-area model and a large-scale realistic network with detailed AC generator and HVDC models.

The location and variability of wind generation along with the difficulty of gaining permits for the construction of new overhead lines are placing increasing pressure on transmission system operators to increase utilisation of existing transmission capacity in as flexible a way as possible. Phase sifting transformers (PSTs) can contribute to this. However, to gain maximum benefit, the settings of a number of PSTs should be coordinated in a `smart' way. This paper presents an overview of PSTs, their technical characteristics and their current use on GB Transmission Network. Issues and challenges for their effective and coordinated operation are raised and discussed with examples from a test network

This paper analyses the dynamic behaviour of a power system with both FACTS and VSC HVDC, in particular, possible potential interactions between a STATCOM and a VSC in a point-to-point HVDC link. The investigation considers different STATCOM locations and VSC control strategies. A generic linearized mathematic model is firstly developed, where a combined method involving relative gain array (RGA) and modal analysis is applied to identify the interactions within the plant model and the outer controllers. The interactions identified are further analysed by creating a set of scenarios integrating both the STATCOM and VSC HVDC into a dynamic equivalent realistic AC system. Results show a collaborative operation between the STATCOM and the closely located VSC with reasonably tuned controllers.