Generacion Distribuida

Distributed Generation Location and Capacity Effect on Voltage Stability of Distribution Networks
Nasser G. A. Hemdan, and Michael Kurrat, Member, IEEE
Institute of High Voltage Technology and Electric Power Systems Braunschweig University of Technology Braunschweig, Germany n.hemdan@tu-bs.de, m.kurrat@tu-bs.de
Abstract—Analysis of the effect of distributed generation (DG) capacity andlocation on voltage stability enhancement of distribution networks is presented in this paper. The analysis is performed using a steady state voltage stability index which can be evaluated at each node of the distribution system. Different optimal capacities and locations are used to check this effect. The location of DG has the main effect on the system voltage stability. Voltage stability should betaken into account as one of the objectives of DG optimal allocation techniques. The analysis is conducted on a 69 node distribution system. Keywords-Distributed Generation;Voltage Stability;Distribution Networks

Distribution systems are traditionally passive and designed to operate with such unidirectional energy flow, not as the transmission system is designed for two-way power flow. In planningand operating, it is assumed that electric power always flows from the secondary winding of the transformers in the substations to the end of feeders. With newly introduced distributed generation, the distribution system becomes an active system with both energy generation and consumption at the formerly exclusive load nodes. Bidirectional power flows should now incorporated in the hierarchicalnetwork design and its operation criteria [9]. Voltage stability concerns stable load operation, and acceptable voltage levels all over the system buses. Its instability has been classified into steady state and transient voltage instability, according to the time spectrum of the occurrence of the phenomena. A power system is said to have entered a state of voltage instability when a disturbancecauses a progressive and uncontrollable decline in voltage [10,11]. Voltage stability analysis often requires examination of lots of system states and many contingency scenarios. For this reason the approach based on steady state analysis is more feasible, and it can also provide global insight of the voltage reactive power problems [11]. The voltage stability phenomenon has been well recognized indistribution systems. Radial distribution systems having a high resistance to reactance ratio causes a high power loss so that the radial distribution system is one of the power systems, which may suffer from voltage instability [10,12]. The effect of DG capacity and location on voltage stability enhancement of radial distribution system is investigated in this paper. The analysis process isperformed using a steady state voltage stability index presented by M. Charkravorty and et.al in [13]. This index can be evaluated at each node of radial distribution system. The optimal capacities and locations of DG for a 69 node distribution system evaluated by G. P. Harrison and et.al in [14] are used to perform the analysis. II. VOLTAGE STABILITY INDEX

I. INTRODUCTION The penetration ofdistributed generation (DG) resources (wind turbines, photovoltaic, fuel-cells, biomass, micro turbines, small hydroelectric plants, etc., ranging from sub-kW to multi-MW sizes) in distribution grids is increasing worldwide. The drive for cleaner energy sources, the economic opportunities presented for investors in the deregulated electric industry environment, and the potential benefits for utilities(peak shaving, congestion alleviation, reduction of losses, better asset utilization, etc.) are contributing to this trend [1,2] Although there always exist important regulatory and business issues concerning the integration of DG in the grids, technical considerations are often viewed as a critical factor affecting the development of new installations [1,3]. Due to the locally available resources...