Improved system performance by integration of adjustable speed hydro (ASH) machines

The main purpose of this paper is to show how the adjustable speed hydro (ASH) machine behaves with respect to transient and dynamic conditions in power systems. The ASH machine gives a contribution to increased efficiency in the penstock/turbine system as well as an improved flexibility with respect to the electrical system. By means of its quick response to network events, the ASH machine is able to obtain an increased stability margin and thereby a more safe operation of the power system. With proper location and parametrisation of power system stabilisers (PSS), the ASH machine can make considerable support to damping of large scale power oscillations in transmission networks. On the other hand, this represents new opportunities for the power producer as well as for the system operator in utilising the transmission network even better. The paper has shown that transmission lines appearing as bottlenecks with respect to power demand may increase their transfer capacity as ASH machines are introduced in the network. In turn, this may lead to a postponement of high investment costs for new overhead lines. Furthermore, the paper has given a quantification of how much the power export out of an example region can be increased due to introduction of ASH machines.