Improving system loadability with the consideration of multiple bifurcations

The introduction of large numbers of power electronic converters along with increasing load demand will create voltage stability issues in future power systems. Most present analysis methodologies neglect the non-linearities within these systems. Bifurcation analysis is an increasingly popular method which not only incorporates system non-linearities, but also efficiently provides information about the system trajectory towards multiple instability mechanisms. This paper develops a new concept of combined system loadability with the consideration of saddle-node bifurcations (SNB), limit-induced bifurcations (LIB), and Hopf bifurcations (HB) simultaneously. These concepts have shown great promise in analyzing complex, multi-origin stability phenomena which are starting to appear in power systems and other areas, and are difficult to study using other methods. An optimization approach is applied to identify the system maximum loadability with these different types of bifurcation points which have not previously been considered at the same time. This creates a new system loadability boundary concept consisting of multiple types of bifurcation which is more representative of the actual power system limit boundary. By maximizing the shortest distance to the composite loadability boundary, the system loading margin is increased. Three illustrative systems are used to verify the proposed methodologies.