Analysis of Three Phase Self Excited Induction Generator Using MATLAB/SIMULINK Prerna Gaur, Avinash Kishore N.S.I.T., India SELF excited induction generator (SEIGs) are slowly replacing conventional synchronous alternator in isolated power generation because of the former ruggedness lower unit cost, relative ease of operation and maintenance easily availability in lower rating even under low speed operation. Since a majority of loads even in isolated system are dynamic in nature, wider applicability of the SEIGs would depend on its capacity to handle such loads satisfactorily. Another bottleneck in the applicability of the SEIG is its inherent poor voltage regulation, and the conquest requirement of a well designed voltage regulator. The cost complexity and operational problems associated with the regulator often vitiate the advantage gained in using an induction machine for isolated application. In an externally driven three phase induction motor, if a three phase capacitor bank is connected across it’s stator terminals, an e.m.f. is induced in the machine windings due to self excitation provided by the capacitor. The magnetizing requirement of the machine is supplied by the capacitors. For self excitation to occur, the following two conditions must be satisﬁed: 1. The rotor should have suﬃcient residual magnetism. 2. The three phase capacitor bank should be suﬃcient value. If the rotor has suﬃcient residual magnetism, a small e.m.f. is developed in the stator winding. The e.m.f. if suﬃcient in magnitude would circulate leading current in the capacitors. The ﬂux produced due to these currents would assist the residual magnetism. This would increase the machine’s ﬂux .This process is thus cumulative and the induced voltage keeps on rising until saturation is reached. As saturation occurs, the ﬂux becomes constant and ﬁnal steady state value of the voltage is obtained. This voltage continues to exist till value of capacitance and speed dare maintained favorably. Also, the value of the three capacitance bank should be of suﬃcient magnitude in order to initiate self excitation and generate e.m.f of suitable value. To start with steady state analysis of the SEIG with the static load is critically analyzed. The analytical technique used for the static load is found not directly applicable to dynamic load. Consequently, a program is developed to predict the steady state performance of the SEIG. Eﬀect of capacitance on the performance of the SEIG is studied to enable selection of suitable capacitor for a given operating condition. To start steady state analysis a equivalent circuit is presented which represent the steady state model of SEIG. Using that circuit a equations is developed to obtain the steady state behavior of the SEIG. In the steady state analysis the magnetizing property of the machine is assumed to be linear. Following the circuit the parameters are obtained. Following the steady state investigation response of the SEIGs for the diﬀerent transient conditions is studied to know it’s suitability to sudden switching of loads. The d-q axes model which is widely used for the analysis of an induction motor is developed for the SEIGs system. The condition which are considered for the studied include onset of self excitation, load per- turbation, loss of excitation and short circuit. Starting of the induction motor by the SEIGs is studied and methods for reliable starting of the motor are suggested. Based on the inferences drawn from the steady state and transient performance of the system, guidelines are suggested for the design and operation of a dedicated SEIG system for applications such as irrigation pump sets.
Pages to are hidden for
"Analysis of Three Phase Self Excited Induction Generator Using"Please download to view full document