Harmonic analysis and performance improvement of slip energy recovery induction motor drives

Slip energy recovery induction motor drives are used in high power applicat ions, in which by controlling the slip power a variable speed drive system is provided. However, poor power factor is a disadvantage of the system. Pr esence of sub-harmonics of the line frequency on the stator side is one of the special features of these drives. Phase-controlled inverter can absorb the reactive power from the supply and inject the low-order current harmoni cs with relatively high amplitudes to the supply. This paper simulates the harmonic content of waveforms in various points of drive at different speed s, based on the hybrid model (dqabc), Then the sinusoidal pulse-width-modul ation (SPWM) control technique is used in order to improve the power factor of the drive and to weaken the injected low-order harmonics to the supply. Based on the frequency spectrum, total harmonic distortion, distortion fac tor and power factor, two phase control and SPWM techniques are compared an d the advantage of the SPWM technique over the phase control technique is s hown.