Improved method for the calculation of power systems low voltage solutions
In this paper an improved method for calculating low voltage solutions (LVS) of the load flow (LF) equations is proposed. It is based on a state space search approach and it has the following features: (a) it is fully derived with voltages in polar coordinates, making its insertion in existing production grade LF programs a very easy task; (b) a special procedure is proposed so that it is always possible to obtain a state space search direction and an initial state estimate for the LVS calculation; (c) nonconvergent and divergent cases are easily and efficiently detected and handled through the use of step size optimization techniques; (d) it correctly identifies the desired LVS in case several close solutions exist (as it is often the case for real life systems); and (e) the LVS can be found regardless of its distance to the stable (high voltage) solution. Also, a more robust way of finding the initial estimate for the LVS is proposed. Test results have shown that the method is robust and efficient. A comparison between state space search methods (SSSM) and path-following methods (PFM) is presented. Finally, a very simple maximum loading point (MLP) proximity index is shown and its characteristics are discussed.
low voltage solutions state space search method multiple load flow solutions voltage stability