Steady State Analysis of Self-Excited Induction Generator for Balanced and Unbalanced Conditions

Abstract

Use of self-excited induction generator is becoming popular for the harnessing the renewable energy resources such as small hydro and wind. The poor voltage regulation under varying load is the major drawbacks of the induction generator. The steady state analysis is paramount as far as the running conditions of machine are concerned. To study the steady state aspects, methods are required by which the generator performance is predicted by using the induction motor data so that the effect of the parameters can be assessed. Different methods are available to identify the steady state operating point under saturation for a given set of speed, load and excitation capacitor. The steady-state analysis of self-excited induction generators (SEIG) under balanced conditions using an iterative method is presented. MATLAB programming is used to predict the steady state behaviour of self-excited induction generator. By considering the conductance connected across the air gap node in the equivalent circuit, an iteration procedure is developed for the determination of the per unit frequency. The main advantage of the method as compared with other methods of analysis is that it involves only simple algebraic calculations with good accuracy and rapid convergence. The steady state analysis of three-phase self-excited induction generator for unbalanced conditions is also presented. Symmetrical components theory is used to obtain relevant performance equations through sequence quantities. While the analysis of the system is inherently complicated due to unbalance and magnetic saturation. Valid simplifications incorporated in the equivalent circuit for both forward and backward fields results in manageable equations suitable for computer simulation. Newton-Rhapson method is employed to solve these equations in order to determine the generated frequency and magnetizing reactance. Computer program in MATLAB environment is developed to determine the performance under any unbalanced external network at the given speed of the prime mover.