Analysis & Control of Integrated Distribution Networks Based On Distributed Generation Systems

Abstract

Distributed1generation (DG) systems1based on renewable1energy resources1play an important1role in electric1power systems. The1estimated share of1these resources in electrical1networks will1increase significantly1in the1near future by providing1different benefits like cost1reduction, reliability1of main1grid, and emission1reduction. In this1thesis wind energy DG1system that uses1Doubly Fed Induction1Generators (DFIGs) is1considered. The DFIG is1a special type1of induction1machine which1is comprised of1two back-to-back1converters. One1converter connects the DFIG1stator to the grid, and1the second converter is1connected to the1rotor of the machine1through a1DC-link capacitor. In1this work, DFIG1model has been created1in the DQO1reference frame. The1wind turbine (WT) system1is modelled by considering1typical wind turbine1aerodynamic characteristics1under variable wind1and pitch angle1conditions. The variable1speed WT system equipped1with DFIG is normally1controlled by a set of1controllers. Tuning these1controllers is a tedious1work and it is difficult to1tune the gains of controllers1optimally due to the1nonlinearity and the high1complexity of the1system. Design1an optimal control strategy1is the most important1part to integrate wind1energy system as a1renewable DG resource1into the electricity1grid. Today this has1become an important1challenge for the utilization1and control of1electric power1systems, because of1the fluctuating and1intermittent behaviour1of wind power1generation.