Extended holomorphic embedded load-flow method and voltage stability assessment of power systems

Existing iterative load flow methods provide spurious solution/diverge near maximum loading point. The solution is also affected by the choice of initial condition. A non-iterative method known as holomorphic embedded load-flow method (HELM) overcomes these limitations. Existing holomorphic embedding (HE) formulation do not incorporate shunt conductance of voltage regulating transformer and reactive power injection at certain buses of the transmission system. This paper extends existing HE formulation incorporating all the parameters and develops a new HE formulation for non-uniform loading of the system. Another contribution of the paper is the formulation of a novel voltage stability index that measures load distance as well as voltage distance to accurately assess the voltage stability state of the system. The proposed research work is investigated using benchmark IEEE 14, 30 and 118-bus test systems.