Multirate PI Control System Performance for a Wind Energy Conversion Scheme

This paper deals with the performance of a multirate PI controller for a wind energy conversion scheme using a self-excited induction generator connected to the supply system through a DC link. The PI controller loope for the firing angles of the converter and inverter in this scheme use different sampling rates. The performance of a multirate controller with a set of PI gains is compared to that of the single (fast) rate PI controller using the same gains. Experimental results are shown for this case. Next, PI gains are designed by the minimization of an integral squared error (ISE) criterion using nonlinear optimization methods on the nonlinear dynamic model of the system for various integral ratios of the two sampling periods in the loops. It is seen from simulation of the resultant controllers on the nonlinear dynamic model that a multirate PI controller has better performance in terms of overshoot and settling time for this system at certain choice of rates than a similarly designed single fast rate PI controller.