Optimum number of cascade cells for multilevel inverter considering redundancy strategies based on cost and reliability optimization

Abstract This paper proposes an economical reliability‐oriented solution to determine the optimal number of cascade cells and redundancies for STATCOM using a Non‐Dominated Sorting Genetic (NSGA‐II) algorithm based on different redundancy configuration schemes. A multi‐objective optimization framework is presented, to minimize the total cost and maximize its reliability index by considering power quality issues. In the presented model, a new cost modelling is introduced considering the cost of inductor loss. The multilevel cascade topology with staircase modulation strategy is also taken into account. The effectiveness of the proposed optimization framework is validated by the NSGA‐II algorithm compared to the results of goal attainment and goal programming as decomposition single‐objective optimization methods. The results verify that the proposed multi‐objective optimization framework could be useful in the optimal selection of high‐voltage STATCOM levels in the presence of redundancies while ensuring the required level of reliability at the minimum cost. Also, the presented NSGA‐II optimization algorithm is applicable to maintain both objective functions at an acceptable value.