Load Flow Analysis of Distribution System Including Wind Turbine Generating System Models

The power world is sauntering towards ecofriendly distributed generation (DG), their integration into the distribution network postures challenges to existing load flow techniques. This paper is concerned with developing models of various types of wind turbine generating systems (WTGSs) used as distributed generation (DG) sources and demonstrating their application for steady state analysis. As wind energy is used as a DG power source, its impact on the distribution system needs to be analyzed. This requires a load flow algorithm capable of simulating both radial and weakly mesh systems along with Wind Turbine Generating Systems (WTGSs). The compensation based distribution load flow algorithm is extended including WTGS modeling in the present work. The application of the proposed models for the load flow analysis of radial systems having WTGS has been demonstrated. Based on these studies we evaluate the impact of wind based DG on the voltage profile and losses of radial distribution networks. Simulation studies have been conceded out on radial distribution systems having WTGS as DG sources to illustrate the application of the proposed models. Keywords— Distributed Generation, Distribution load flow, Wind Turbine Generating Systems, Forward and Backward sweep, Voltage Profile, Losses. I.INTRODUCTION The supply of electric power to homes, offices, schools, factories, stores, and nearly every other place in the modern world is now taken for granted. Electric power has become a fundamental part of the infrastructure of contemporary society, with most of today’s daily activity based on the assumption that the desired electric power is readily available. The power systems which provide this electricity are some of the largest and most complex systems in the world. They consist of three primary components: the generation system, the transmission system, and the distribution system. Each component is essential to the process of delivering power from the site where it is produced to the customer who uses it. Wind energy continues to be one of the fastest growing energy technologies and it looks set to become a major generator of electricity throughout the world. The role of wind energy in electrical power generation is increasing day by day and new advances in power electronic Equipment’s are underpinning this strategy. Wind energy is converted into mechanical power by wind turbines. This mechanical power is fed to the generator directly or through gear system. This cumulative arrangement of turbine and Generator is called a wind turbine generating unit (WTGU). A large number of wind turbine generating systems (WTGSs) are already in operation and many new systems are being planned. The integration of WTGS with the power systems is taking place at both the transmission and the distribution voltage levels. This growth in wind generation has spurred investigations, to understand the behavior of the wind turbine generating Systems (WTGSs) as well as their impact on the power grid. As distributed generation penetrates into the distribution network its impact on the voltage profile and total power losses needs to be analyzed by appropriate load flow methods. Due to high R/X ratio of distribution lines, the performance of load flow methods used for the transmission network are inadequate for distribution systems. These methods do not make use of the structural advantage (radial / weakly mesh) of distribution system. This led to the development of separate load flow methods for distribution system. These methods are broadly classified into three categories: direct methods, backward / forward sweep methods and Newton-Raphson based methods [1]. The backward/forward sweep methods have an edge over the others as they are simple, flexible and the computational time requirement is low [1]. The basic backward/forward sweep method described in [2] is applicable for radial networks only. The practical distribution systems are weakly meshed. The compensation based distribution load flow algorithm proposed in [3] address this issue. It is improved to adapt the PV bus modeling in [4]. The method was further extended to the distribution networks containing DG’s, where these are modeled as constant PQ or PV nodes [5]. Ii. Wtgs Modeling The mechanical power converted from wind energy by a wind turbine is described as