An Approach for Under Voltage Load Shedding Using Particle Swarm Optimization

Under voltage load shedding (UVLS) is one of the most powerful countermeasure and somehow an economical solution to sustain voltage stability especially for double or severe contingencies in power systems. In this paper the concept of dynamic security-constrained OPF is employed to develop a model for optimal UVLS. Considering dynamic voltage security, the presented model attempts to provide sufficient voltage stability margin for post contingency condition. This is done by means of interruption some portion of loads at minimum cost. The voltage stability margin, which is measured as a MW distance to the collapse point, is incorporated into the power flow equations. Although some powerful mathematical based nonlinear optimization techniques are available to find the optimal solution of the problem, here the intention is to show the feasibility and efficiency of the PSO algorithm when it is applied to such problems. To end this, PSO's results are compared with the results obtained by another evolutionary approach like GA. In this stage, the IEEE 39-bus system is adopted for UVLS problem and the solutions found by these two approaches are compared in various aspects