Order reduction by minimizing integral square error and H∞ norm of error

In this paper, a new alternative method for order reduction of high ordersystems is presented based on optimization of multi objective fitness function byusing Harmony Search algorithm. At first, step response of full order system isobtained as a vector, then, a suitable fixed structure considered for model orderreduction which order of original system is bigger than fixed structure model.Parameters of model order reduction are determined by minimizing the multiobjective fitness function where the fitness function is conducted with integralsquare error and H∞ norm of error. The harmony search algorithm is applied forminimizing the multi objective fitness function. To assure the stability, the Routhcriterion is applied for specifying the stability conditions. This stability condition isconsidered as constraints in optimization problem. To present the accuracy y of theproposed method, three test systems are reduced. The obtained results show that theproposed approach performs very well.

Order reduction by minimizing integral square error and H∞ norm of error Keywords:

Harmony search , model reduction , Routh criterion , H∞ norm , Integral square error