Improving voltage stability in power systems with HVDC converters

When analysing HVDC systems connected to weak AC systems it is important to have a model that is simple and still captures the important features of the system. Such a model is presented and a number of conclusions are drawn from simple arguments based on physical observations of this system. These findings are verified by a more rigorous mathematical treatment of the problem. This analysis includes both steady state and dynamic conditions. It is also demonstrated how an appropriate control of the convertors can be used to stabilize a voltage instability in the system