Abstract
A two-level optimization method is presented to find the optimal number and location of conventional protective devices to be upgraded to remote-controlled switches (RCSs) for an existing distribution network (DN). The effect of distributed generation (DG) on this problem is considered. In the first level, a nonlinear binary program is proposed to maximize the restored customers subject to technical and topological constraints. All feasible interchanges between protective devices and ties involved in the restoration, when a fault occurs at all possible locations are found considering switching dependencies. In the second level, a nonlinear cost function, combining the expected cost of interruptions (ECOST) and the switch cost, is minimized with respect to the location of RCSs. The expected cost function is computed based on the optimum restoration policies obtained from the first level. The optimum placement of RCSs using the proposed algorithm is tested on a 4-feeder 1069-node test system and compared to the solution obtained with a genetic algorithm (GA) on the same system.
Highlights
The reliability of an existing distribution network (DN) can be significantly improved by upgrading existing manual protection devices to remote-controlled switches (RCSs) that have communication capability and can achieve quicker system restoration following a permanent outage [1,2]
The partial restoration was not considered in problem formulation, and the optimal number of switches was not reflected in the objective function
The main contributions of the paper are: the feasible solutions of restoration policies are first determined, and the optimum one is selected from the feasible set by solving a mathematical program that is formed with the assistance of the fundamental cut-set matrix of DN; the dependencies of switching operations to restore the interrupted loads are considered by obtaining the sequence of switching actions; elite genes (EG) are defined efficiently based on independent switching actions to solve the final objective function; and both normally closed (NC) and normally open (NO) switches are reflected in the optimization problem; the optimum upgrading of NO switches can be determined as well
Summary
The reliability of an existing distribution network (DN) can be significantly improved by upgrading existing manual protection devices to remote-controlled switches (RCSs) that have communication capability and can achieve quicker system restoration following a permanent outage (e.g., longer than 5 min) [1,2]. The partial restoration was not considered in problem formulation, and the optimal number of switches was not reflected in the objective function. The main contributions of the paper are: the feasible solutions of restoration policies are first determined, and the optimum one is selected from the feasible set by solving a mathematical program that is formed with the assistance of the fundamental cut-set matrix of DN; the dependencies of switching operations to restore the interrupted loads are considered by obtaining the sequence of switching actions; elite genes (EG) are defined efficiently based on independent switching actions to solve the final objective function; and both normally closed (NC) and NO switches are reflected in the optimization problem; the optimum upgrading of NO switches can be determined as well.
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