Direct calculation of voltage‐stability limit of electric power systems

AbstractOn‐line monitoring of voltage‐stability conditions is a new requirement for the energy management systems of the electric power industry. Preferred by the utility engineers and dispatchers is an index which represents explicitly the margins to a voltage‐stability limit (collapse point) expressed in a physical unit ordinarily used. For example, such indices are the system load and voltage‐voltage‐stability‐margins (SVVSM) between the present operating point and a voltage collapse point. However, long computer time is required to calculate accurately the voltage collapse point by the conventional method because many multiple load‐flow solutions are required.This paper presents a new algorithm to calculate directly, exactly, and rapidly the voltage‐stability limit. The algorithm uses the load‐flow equations and the explicit expressions of the voltage collapse root conditions are expressed as dR/dV = 0, where R is active or reactive power node injection, and modifying the conventional N‐R load‐flow program, and is not affected numerically by singular Jacobians. The proposed algorithm is verified through calculating the voltage stability limit of a 176‐node power system.