Unbalanced voltage sag correction with dynamic voltage restorer using particle swarm optimization

Voltage sag is a crucial power quality problem. Due to the asymmetry present in occurrence of sags, dealing with unbalanced voltage sag is more complicated. Along with the reduction in voltage magnitude, if phase-jump is accompanied in unbalanced voltage sag, it further complicates the compensation. Power electronic converter loads get seriously deteriorated due to the unbalance present either in magnitude or in phase-angle relationship present between all three phases. Apart from restoring magnitude of the load voltage to the required level, care has to be taken so that balance is maintained in the three phase network. But, taking into consideration the maximum voltage injection constraint of the dynamic voltage restorer (DVR), voltage injection has to be done in an efficient manner so as to find out the best scheme of DVR voltage injection. Particle swarm optimization (PSO) technique is used to find out the optimum configuration for various unbalanced voltage sags with phase-jumps. Numerical examples are included to illustrate the efficacy of the proposed algorithm.