Modeling and Analysis of a Six-phase Self Excited Induction Generator Feeding Induction Motors

Conventionally, the multi-phase self-excited induction generators (SEIGs) have been analysed either with resistive or static resistive-inductive loads. This endeavor proposes a simple six-phase SEIG (6 $\phi$ -SEIG) topology feeding induction motors (IMs). Shunt and series capacitances provide excitation current and load voltage compensation for 6 $\phi$ -SEIG. A stationary reference frame dual dq model including non-linear saturation and cross coupling effects is integrated with IM loads for simulating 6 $\phi$ -SEIG-IM set. Sub-synchronous resonance (SSR) is associated with series compensated SEIGs. A series capacitance 2.5 times the excitation capacitance causes SSR in studied 6 $\phi$ -SEIG as starting of IMs is attempted from its terminals. SSR induces low frequency oscillations and spikes load voltage and current amplitudes. A method to overcome SSR is proposed by evaluating a critical value of series capacitance ( $C_{se,cr}$ ). Equipped with $C_{se,cr}$ and excitation capacitance the 6 $\phi$ -SEIG successfully sustains starting, no-load build-up and rated load operation of IMs. A comparison with its equivalent 3 $\phi$ counterpart reveals that 6 $\phi$ -SEIG manages reactive power more efficiently as its optimum capacitance requirement reduces by 1.9 to 3.75 times, it incurs 0.4% to 2.8% lesser %THDs in output parameters and exhibits greater operational flexibility. Experimental results are obtained on an open end winding induction machine operated as SEIG.