Optimal Planning of the Distribution Network with Distributed Generation

Abstract

The deregulation of electricity market created a competitive market environment. For Distribution companies (DISCOs), how to maximize its profit is the primary purpose of this planning and operations. Therefore, to achieve the best economic and technical benefits, a DISCOs should determine where and how much DG units allow to install in the system. Distributed generation is a key component in the power market. There is a brief introduction of DG in this thesis including: the definition of DG, size and several often used DG types. The benefit and risk of DG which may bring to the power system also have been appropriately evaluated in this study. The review of literature of optimal size and location of DG in distribution system have shown that a number of economic and technical impacts have been considered in DG planning. The selection of the best places and the preferable size of DG units for installation in the distribution system is a complex combinatorial optimization problem. The various solution techniques along with various objective function and constraints for the optimal solution of the problem of size and location problem of DG are discussed and compared in this work. With the increasing of load demand, distributed generation becomes an attractive alternative method to supply the power in the distribution system. DG can not only help to defer the T&D investment but also bring benefits to environment protection. The technical benefit which can bring to the distribution system also cannot be ignored. Such as power loss reduction, voltage profile and power quality improvement. The impact of DG units on voltage stability has become significant. A review of the indices refers to voltage stability has been shown in this work and an index named voltage collapse proximity index (VCPI) was introduced and used in this work. This study proposed a planning framework for effective planning of DG units in the distribution system due to minimize total cost and enhance the voltage stability of the system. To achieve the purpose of minimizing the total cost and maximize the technical benefit of DG units to voltage stability, a multi-objective methodology to decide optimal locations and size of DG units. The total cost in the proposed planning model includes investment cost, operation and maintenance cost except the revenue from the utility grid. VCPI which is given in this study have been used in this model to identify the voltage stability of this system. The uncertainties associated with the load value, and generated power of renewable energy DG units also take a part in this study. A Monte Carlo simulation method has been introduced in this work to calculate the uncertainty because of probabilistic nature of renewable DG unit (WTs, PVs). The Pareto optimal set is found by using non-dominated sorting genetic algorithm method and the final result is chosen by using the max-min method. An IEEE 33-bus distribution system with DG installation has been used to achieve the goals of minimum total cost and improvement of voltage stability.