| This thesis develops small-signal and large-signal models to investigate the dynamic performance of a hybrid wind-diesel energy system interfaced to a utility grid. The study system comprises a 3.5-MVA diesel-generator unit operating in parallel with a 750-kVA variable-speed, squirrel-cage induction generator, wind unit. The wind unit is interfaced to the power network through a back-to-back voltage-sourced converter system.; The controllers of the machine-side converter regulate the mechanical torque and the shaft speed of the induction generator to obtain maximum power production under fluctuating wind-speed conditions. The controllers of the grid-side converter maintain the dc-link voltage and the ac-side converter terminal voltage within the specified limits and ensure delivery of the captured wind power to the network.; The diesel-generator unit is equipped with excitation and governor systems to compensate for (i) output power changes of the wind unit due to the intermittent nature of the wind, and (ii) changes in the load demand.; Based on small-signal (eigen) analyses in the MATLABRTM software environment, the controller parameters of the wind and the diesel units are selected to guarantee (i) minimization of transients due to switch over between two consecutive modes of operation, (ii) voltage/angle stability during islanded (autonomous) mode of operation, and (iii) local load requirements in terms of voltage and real/reactive power.; The results obtained from time-domain simulations, in the PSCAD RTM/EMTDCRTM software environment, demonstrate that proper adjustment of the controllers of the wind and diesel units promote "ride-through" capability in the event of (i) pre-planned transitions between different modes of operation, (ii) pre-planned islanding and re-connection of the units to the power network, and (iii) short circuits, accidental islanding and subsequent re-connection attempts to the network.; The developed eigen analysis tool is structured to accommodate any network configuration, any number of wind-diesel units, and any variable-speed wind-unit technology. |
