Abstract:The first contribution of this paper is to present three alternative analytical expressions to identify the location, size and power factor of a single DG unit with a goal of minimizing power losses. These expressions are easily adapted to accommodate different types of renewable DG units for minimizing energy losses by considering the time-varying demand and different operating conditions of DG units. Second objective is to minimize the cost of plantation of renewable energy source at the buses with high losses. This cost also must be minimized in coordination with losses minimization. A meta heuristic algorithm, firefly optimization is used for this purpose. Results are compared with the other metaheuristic algorithm, widely used in literature, particle swarm optimization (PSO).Comparative results in form of losses and voltage profile improvement shows effectiveness of our algorithm. Keywords: Distributed Generation, Firefly Optimization, PSO I. INTRODUCTIONDistributed Generation plays a vital role in the electric power system due to increased availability of small capacity generation technologies [1]. DG installations require special studies and attention to help maintaining system reliability and performance. Optimal allocation of DG effectively reduces the operational cost and increases the reliability and quality of power supply and also cuts down the power and energy losses. DG has significant impact on the voltage profile of the system. Voltage profile is defined as the change in the voltage of the system as the load changes. With the increased loading and exploitation of the existing power structure, the probability of occurrence of voltage collapse are significantly greater than before and the identification of the nodes which are prone to the voltage fluctuations have attracted more attention for the transmission as well as the distribution systems. For operating a power system in a safe and secure manner, all unsecure operating states can be identified and DG placement can be done, in order to enhance the voltage stability margin [2]. Many researchers have introduced different DG placement algorithms using analytic or heuristic approaches. Only a few works have been concentrated on optimizing the effect DG in voltage stability improvement. A method of finding a continuum of power flow solutions starting at some base load and leading to the steady state voltage stability limit of the system was presented in [3]. A method for DG placement in radial distribution networks which uses CPF to identify the most sensitive bus to voltage collapse has been applied in [4]. Voltage stability analysis of large power systems using a modal analysis technique was proposed in [5], which gives the idea about the proximity to voltage collapse. In [6] optimal DG allocation has been identified which is based on the modal analysis and compared the effectiveness of the method to the CPF method. The determination of maximum loading is one of the most important problems in voltage-stability analysis that cannot be ca...