Distribution system problems, such as planning, loss minimization, and energy restoration, usually involve network reconfiguration procedures. The determination of an optimal network configuration is, in general, a combinatorial optimization problem. Several Evolutionary Algorithms (EAs) have been proposed to deal with this complex problem. Encouraging results have been achieved by using such approaches. However, the running time may be very high or even prohibitive in applications of EAs to large-scale networks. This limitation may be critical for problems requiring online solutions.The performance obtained by EAs for network reconfiguration is drastically affected by the adopted computational tree representation. Inadequate representations may drastically reduce the algorithm performance. Thus, the employed representation for chromosome encoding and the corresponding operators are very important for the performance achieved. An efficient data structure for tree representation may significantly increase the performance of evolutionary-based approaches for network reconfiguration problems.The present paper proposes a tree encoding and two genetic operators to improve the EA performance for network reconfiguration problems. The corresponding EA approach was applied to reconfigure large-scale systems. The performance achieved suggests that the proposed methodology can provide an efficient alternative for reconfiguration problems.
This paper presents the fundamentals and the algorithm of a new methodology for the design of robust power system damping controllers. The methodology provides controllers capable of fulfilling various practical requirements of this problem, which could not be simultaneously satisfied by the majority of the proposed robust control approaches until now. The design procedure is based on a special formulation of the dynamic output feedback control problem, in which the design problem can be expressed directly in the form of linear matrix inequalities. The formulation also allows the incorporation of decentralization constraints on the controller matrices, one of the practical requirements for power system damping controllers. Other practical requirement is satisfied with the use of the polytopic model (to ensure the robustness of the closed-loop system with respect to the variation of operating conditions). Moreover, the inclusion of a regional pole placement criterion allows the specification of a minimum damping factor for all modes of the controlled system. The results show the controller is able to provide adequate damping for the system oscillation modes.
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