Differential Geometric Foundations for Power Flow Computations.

This paper aims to systematically and comprehensively initiate a foundation for using concepts from computational differential geometry as instruments for power flow computing and research. At this point we focus our discussion on the static case, with power flow equations given by quadratic functions defined on voltage space with values in power space; both spaces have real Euclidean coordinates. Central issue is a differential geometric analysis of the power flow solution space boundary (SSB) both in voltage and in power space. We present different methods for computing tangent vectors, tangent planes and normals of the SSB and the normals' derivatives. Using the latter we compute normal and principal curvatures. All this is needed for tracing the orthogonal projection of curves in voltage and power space onto the SSB for points on the SSB cosest to given points on the curves, thus obtaining estimates for the distance to the SSB. Furthermore, we present a new high precision continuation method for power flow solutions. We also compute geodesics on the SSB or an implicitly defined submanfold thereof and, used to define geodesic coordinates together with their Jacobians on the manifolds. These computations might be the most innovative and most significant contribution of this paper, because this concept provides a comprehensive coordinate system for sub many folds defined by implicit equations. Therefore while moving on geodesics described by the geodesic coordinates of the sub manifold at hand we get, via systematic navigation guided by geodesic coordinates, access to all feasible operation points of the system. We propose some applications and show some properties of the Jacobian of the power flow map.