A Modified Control Topology to Improve Stability Margins in Micro-grids with Droop Controlled Inverter Based Distributed Generation

  • Nadim H. Kan'an

Student thesis: Master's Thesis

Abstract

Electrical power systems are major contributors to the greenhouse gas emissions. Recent efforts to tackle the effects of global warming have made renewable energy-based distributed generation (DG) an important player in electrical power production. This led to the introduction of new concepts in the field of electrical power that would help harness the advantages offered by these renewable energy-based DGs, such as the micro-grid. Such new topologies, however, present their own challenges. Droop control techniques of Inverter Based Distributed Generation (IBDG) are generally the most common approach for controlling micro-grids especially in the islanded mode of operation. However, these techniques suffer from slow transient response in addition to inefficient power sharing under weak system conditions. An improved transient response as well as better load sharing can be achieved using higher droop gains. However, large droop gains drive the system into the unstable region. In this work, a new control topology is proposed to facilitate the use of higher droop gains. The advantages of the proposed control topology are proven through small-signal stability analysis. The controller gains are optimally determined using Particle Swarm Optimization (PSO). The control gain selection problem is formulated as a constrained optimization problem where the main objective is to maximize the droop gain while maintaining micro-grid stability and adequate dynamic performance. The proposed control topology with its optimal parameters is verified through tests on a micro-grid with three IBDG units in the MATLAB/SIMULINK environment. The results show that the proposed P-PID-PD controller facilitates the use of much higher droop gain values at higher stability margins compared to the commonly used PI-PI-P control topology.
Date of AwardDec 2011
Original languageAmerican English
SupervisorHatem Zein El din (Supervisor)

Keywords

  • Topology
  • Renewable Energy
  • Electrical Power

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