Calculation of the extreme loading condition of a power system for the assessment of voltage stability

Abstract

The Extreme Loading Condition (XLC) of a power system is defined by assuming a load increase (a m d i n g to a predefined pattern for both active and reactive powers) until a maximum is reached for anyone of the lods. The XUJ is significant for the assessment of voltage stability. Its calculation, as presented in the paper, is based on increasing the load admittances while first keeping the generator voltage phasors constant and then adjusting these phasors for satisfying operational requirements with respect to the generation powers. The secant method is used for the efficient and reliable determination of the maximal value of the loading parameter p, while for the voltage adjustment a fast convergent Newton module is employed. The XLC can be calculated for both normal operation and for contingencies. The new approach is fast and simple and can be used on larger systems. Its features have been illustrated on the 39 bus New England test system. The calculation identifies the weakest bus where remedial action may be needed for voltage support.

Mathematical methods for computing the extremal power values in the nodes of ac electric power systems

“…Numerical computation of the node power limits for the case when load conductances in several nodes vary along a given scalar-parametrized trajectory is reported by Semlyen, Gao, and Janischewskyj [54], who solve the problem (reduced to unconstrained optimization form) by the secant method.…”

“…A specific feature of this case is that the system of node power balances is linear in node voltages [9,54], which makes it possible to reduce the problem with constraints (17) to unconstrained optimization problems and obtain analytical solutions for some problems of this class. Thus, Bogdanov and Davidson [9] obtained an analytical solution for the active power limits in an arbitrary AC grid node assuming that the loads in all nodes (with the exception of the balancing node) are specified by constant conductances whose values are fixed in all nodes, except the given node.…”

Maximum loadability of power systems using hybrid particle swarm optimization

“…Also these indices remain relatively stable up to the system stability limit where they suddenly and rapidly change. This type of behavior renders these indices inadequate to detect stability problems, since they give a false sense of security by remaining practically unchanged until the system is too close to the stability point [5]. Another technique is the repetitive power flow solution by increasing the load on the system in some direction in steps and solving the load flow at each step until the load flow solution diverges [1,6].…”

Relationships Exploration for Real-time Static Voltage Stability Prediction of Power Systems

“…Various techniques are reported to identify and estimate the maximu m load ability in the research of static voltage stability [2]- [3]. One of the conventional techniques is solving the power flow repetitively, starting at a base load leading up to the collapse limit [4], [5], in which the load and the generator output are increased in steps. However, this paper doesn't adopt these specific methods, but simulates the increase of load and generator output using Python language in the software PSS/ E. In this way, not only a batch of power flow at different operating points can be solved at one time, but also different increase directions of load and generator output can be freely selected.…”