Modeling a self-excited induction generator

Abstract

Induction machines have been widely used in power generation and other industrial applications for decades due to their numerous advantages like robust design and lower cost as compared to synchronous machines. When a standalone induction generator like in isolated wind farm and micro hydro is driven by a mechanical prime mover, the residual magnetism in the rotor of the machine induces an electro-magnetic field (EMF) in the stator windings at a frequency proportional to the rotor speed. This EMF is applied to the capacitors (cap-bank) connected to the stator terminals and causes reactive current to flow in the stator windings. The capbank provides necessary reactive power to run the generator as well as reactive power to the inductive loads connected to the generator. Multiple generators can be connected in parallel to increase reliability and to provide required power for increasing loads. This paper presents a PSIM simulation model of a self-excited induction generator (SEIG) using the well-known [alpha beta gamma] three axis model for induction machines (IM). Transient response of standalone generator, two SEIG generators connected in parallel, and SEIG connected to grid is also part of this study. This paper is expected to be a learning module for electrical engineering students to understand dynamics of the induction machines.