Distributed Generation Capacity Planning for Distribution Networks to Minimize Energy Loss: An Unbalanced Multi-Phase Optimal Power Flow Based Approach

Distributed Generation Capacity Planning for Distribution Networks to Minimize Energy Loss: An Unbalanced Multi-Phase Optimal Power Flow Based Approach

Adnan Anwar (University of New South Wales, Australia), Md. Apel Mahmud (Deakin University, Australia), Md. Jahangir Hossain (Griffith University, Australia) and Himanshu Roy Pota (University of New South Wales, Australia)
DOI: 10.4018/978-1-4666-9911-3.ch005
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This chapter presents an unbalanced multi-phase optimal power flow (UMOPF) based planning approach to determine the optimum capacities of multiple distributed generation units in a distribution network. An adaptive weight particle swarm optimization algorithm is used to find the global optimum solution. To increase the efficiency of the proposed scheme, a co-simulation platform is developed. Since the proposed method is mainly based on the cost optimization, variations in loads and uncertainties within DG units are also taken into account to perform the analysis. An IEEE 123 node distribution system is used as a test distribution network which is unbalanced and multi-phase in nature, for the validation of the proposed scheme. The superiority of the proposed method is investigated through the comparisons of the results obtained that of a Genetic Algorithm based OPF method. This analysis also shows that the DG capacity planning considering annual load and generation uncertainties outperform the traditional well practised peak-load planning.
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1. Introduction

Traditionally, distribution networks are passive networks where the flow of both real and reactive power is always from the higher to lower voltage levels. The integration of small and medium sized generation into distribution networks is increasing as these types of generating units offer a number of technical, environmental and economic benefits for utilities along with consumers due to their locations close to customers (Gil, & Joos, 2008). Beside these benefits, the integration of distributed generation (DG) significantly changes the behaviour of the distribution network operations, e.g., passive distribution networks with unidirectional power flow convert into active distribution networks with bidirectional power flow. From the technical point of view, these changes create both negative and positive impacts on both distribution networks service providers (DNSPs) and customers.

The integration of DG creates a variety of well-documented negative impacts on distribution networks. The impact of integrating a single or small amount of DG may not be a significant issue but the penetration of a large fraction of DG may become problematic and affects the power flow of low and medium voltage distribution networks (Lopes et al., 2007). A wide range of conventional approaches are available for mitigating the adverse effects of integrating DG into distribution networks which generally involve the network up-gradation with considerable costs. Traditionally, DG connections are assessed based mainly on 'first come-first serve' basis as well as 'fit and forget' approach that require a DG unit to operate at fixed power factors with a limited capacity to minimize adverse impacts which conspire to limit the available capacity within distribution networks to connect DG (Vovos et al., 2007). Thus, it is essential to shift network planning and operating policies away from the conventional policy of connecting DG to electric power systems to a new and more appropriate one which is able to accommodate more DG within distribution networks.

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