The combined economic-environmental dispatch issue is multidimensional, non-linear, non-convex and highly constrained problem. It involves multiple and often conflicting optimization criteria for which no unique optimal solution can be determined with respect to all criteria. In this paper a multi- objective optimization based solution to the combined economic-environmental power dispatch is proposed. The derivation of the optimal solution is based on the weighted sum method for which improvements are made in direction of penalty function integration. For that purpose a modified dynamic normalization is suggested. A penalization method based on membership functions is introduced in order to calculate the constraint violations. The objective of the proposed method is gaining an optimal solution for the dynamic combined economic-environmental dispatch problem associated to real power systems. Therefore, the algorithm is applied on different test power systems. The obtained results are analyzed and compared with various optimization techniques presented in the literature. The results demonstrate the efficiency of the proposed method in finding solutions toward global optimum.