Optimization methods

 

 

Date

30/05/2007

Author

F. Moussouni, T. V. Tran, S. Brisset, P. Brochet

Affiliation

L2EP – EC Lille – France

Email

fouzia.moussouni@ec-lille.fr, tran.tuan-vu@ec-lille.fr, stephane.brisset@ec-lille.fr

Method

Non-dominated Sorting Genetic Algorithm

References

[1] K. Deb, S. Agrawal, A. Pratap, and T. Meyarivan, “A fast elitist nondominated sorting genetic algorithm for multi-objective optimization : NSGA-II,” IEE Trans. on Evolutionary Computation, vol. 6, no. 2, Apr. 2002.

[2] M. Mohan, K. Deb, and S. Mishra, A fast multi-objective evolutionary algorithm for finding well-spread Pareto-optimal solutions.

[3] H. G. Beyer, and K. Deb, "On self-adaptive features in real-parameter evolutionary algorithm", IEEE Trans. Evol. Comp., Vol. 5, No. 3, pp. 250-270, Jun. 2001.

Description of the method

NSGA-II is one of the most efficient multi-objective evolutionary algorithms using elitist approach [1], [2]. Its particular fitness assignment scheme consists in sorting the population in different fronts using the non-domination order relation. Then, to form the next generation, the algorithm combines the current population and its offspring generated with the standard bimodal crossover and polynomial operators. Finally, the best individuals in terms of non-dominance and diversity are chosen. This new version of NSGA has a low time complexity of O(N logN), where N is the population size.

In this study, standard bimodal crossover (SBX) [3] and polynomial mutation operators are used. For the algorithm parameters, the following values are used: population size N=100, maximum number of generations T=100, mutation probability 0.1, crossover probability 0.9, and the distribution indexes for crossover and mutation operators are  and , respectively.

As optimization of the safety isolating transformer is a non-linear constrained problem the external penalty approach is used. The objective function and non-linear constraints are combined to formulate the following sub-problem:

          (2)

Where f1(X) = Mtot (X), f2(X) = 1-ren(X), are the both original objective functions to be optimized, gi(X) are the m=6 inequality constraints. The parameter µ is a penalty factor updated at each generation k as follow:

                                                  (3)

a is a positive parameter set to 10. µ0 is the upper limit of µ(k), given by the users and must be positive and very large.

Publication of the method

 

 

 

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