ANALYSIS AND CONTROL OF INDUCTION GENERATOR

Abstract

In this report the main concentration is made on the feasibility of the Induction Generators, so that the wind energy can harness in a very efficient manner. Induction generators are increasingly being used in nonconventional energy systems such as wind, micro/mini hydro, etc. The advantages of using an induction generator instead of a synchronous generator are well known. Some of them are reduced unit cost and size, ruggedness, brushless (in squirrel cage construction), absence of separate dc source, ease of maintenance, self-protection against severe overloads and short circuits, etc. In isolated systems, squirrel cage induction generators with capacitor excitation, known as self-excited induction generators (SEIGs), are very popular. For the process of self excitation, fixed capacitor banks or thyristor switched capacitors (TSC's) are commonly used in practice. A model of Fixed Capacitor-Thyristor Controlled Reactor (FC-TCR) is used for the purpose of self excitation and for variable reactive power and this FC-TCR is controlled by a closed loop fuzzy logic controller by controlling the delay firing angle(a) of the FC-TCR as the load (both R and RL loads (cosc)=0.8)) varies from no-load to rated load. To increase the controllable range of speed the WRIG (Wound Rotor Induction Generator) are flexible, which get excitation from the grid side, the rotor of WRIG is connected to the grid via the convertor setup. Due to the advances in power electronics it is advantaged to use the doubly fed induction generator (DFIG) system with variable speed connected to the electrical grid through an AC-AC converter, improving the efficiency of the power conversion. The converter topologies are modeled in the simulink environment and integrated the rotor power to the grid by controlling the converters (both grid side and rotor side converter in case of AC/DC/AC converter topology). The Pulse width Modulation (PWM) techniques and Space Vector Pulse Width Modulation (SVPWM) techniques are used for controlling the converters. The Back to Back AC/DC/AC (IGBT) converter setup is modeled and the same is controlled by using PWM and SVPWM techniques. The Matrix Converter is developed in SIMULINK environment and the same is controlled by using closed loop SVPWM technique. The main aim of developing these converter topologies and control circuits is to analyze the DFIG in both sub and super synchronous modes of operation and to ensure the power flow is bidirectional in case of these converter topologies.