Transient stability impacts of a ‘vertical-to-horizontal’ transformation of power systems

A large-scale implementation of distributed generation leads to a gradual transition from the current ´vertically-operated power system´, which is supported mainly by several large centralized generators, into a future ´horizontally-operated power system´, having also a large number of small to medium-size distributed (renewable) generators. This paper presents a scenario of this ´vertical-to-horizontal´ transformation of power systems and analyzes the impacts on the power system transient stability. The New England test system is used for these purposes. The transformation is realized by increasing the implementation of distributed generation (DG) within the test system in discrete steps, while the load is kept constant. The remaining power is distributed among the centralized generators, directly proportional to their fuel efficiency. The most inefficient units are shut down when the power output falls below their minimum generated power requirement. The impact of DG on the transmission system transient stability is investigated by considering increasing DG (penetration) levels and looking at maximum rotor speed deviations and oscillation durations in the transients resulting from permanent three-phase faults in the transmission system.