Patent ID: 10796037

Abstract:
A system and method is presented for efficiently enforcing control limits in the calculation of powerflow studies of electrical power systems, using the Holomorphic Embedding Load-flow Method. The method applies to any automatic control in which the controlling resource is limited by a maximum or minimum value, such as Mvar limits in generators, the tap ratio in load-changing transformers, or real power output in AGC-participating generators. One key element of this invention consists in devising an equality constraint, holomorphically embedded, able to encode the switching behavior between the different control modes when limit thresholds are reached. The other key element is a novel analytic continuation scheme, here referred to as “Padé-Weierstrass”, which achieves the continuation to s=1 by means of several intermediate steps of power series re-expansions on the path from s=0 to s=1 in embedding parameter space. This technique exploits the great numerical stability of Padé approximants, which in the particular case of the power-flow problem have guaranteed convergence properties granted by Stahl's theorem. The Padé-Weierstrass technique provides the level of precision and numerical stability that is needed to perform the analytic continuation up to s=1 under the new equality constraint. The result is a greatly improved computational efficiency in the calculation of large powerflow studies in which control limits need to be enforced.