There is no doubt that Distributed Generation (DG) has proved to be an effective solution for satisfying the growing demand within a fleeting period and improving system performance, voltage profile, and power quality, especially on the end user’s side. Thus, in modern distribution systems, DG is preferable to be installed in the vicinity of the end user to enhance the system performance, reduce power losses, and improve grid voltage. In this paper, hybrid static and dynamic load types (100% static, 50% static and 50% dynamic, and 100% dynamic loads) at different overloading conditions, for the standard IEEE 33-bus system, are considered, and power system performance is recorded. Moreover, to improve the power system performance, Distributed Generations (DGs) are optimally sized and allocated in the IEEE 33-bus system using the Harmony Search Algorithm (HSA), and two analytical approaches, respectively, and compared to other reported optimization methods. The results show that, at 100% loading, the minimum bus voltage for the proposed method reached 0.97 pu, compared to 0.94 pu for the Particle Swarm Optimization (PSO) algorithm and 0.9574 pu for the Improved Analytical (IA) method. From the results obtained in this paper, it can be concluded that the proposed technique improved the performance of the studied power system, compared to other reported techniques, by enhancing the voltage profile and minimizing the power losses.