Operation of self-excited induction generator through Matrix Converter

This paper aims at obtaining fixed output voltage of frequency 50 Hz to the load by a self excited induction generator (SEIG) employed in wind energy conversion system (WECS). The output voltage of a SEIG is a function of wind turbine´s speed, which varies with wind velocity. Due to the variation in shaft speed of the wind turbine, the output voltage and frequency of doubly fed induction generator (DFIG) will vary. In this paper, a new WECS is proposed in which the conventional PWM AC/ DC/ AC converter is replaced by a matrix converter (MC) topology and the DFIG machine is replaced by a low cost squirrel cage induction generator. MC eliminates bulky DC link capacitor, provides bi-directional power flow capability, independent control on the output voltage magnitude, frequency and phase angle as well as the input power factor. Space vector pulse width modulation (SVPWM) technique is used for controlling MC in such a way that output load voltage and frequency is kept constant for all wind velocities. The SVPWM technique provides higher voltage transfer ratio without lower order harmonics. SVPWM is digitally implemented using DSP processor (TMS320 F2407A). Switching times are pre-calculated offline. Semi soft commutation procedure for safe switching control of MC switches is also presented.