On the improvement of energy efficiency in existing fixed speed WECS

Due to simplicity and cost advantage, a significant opportunity of an existing and proposed wind farm are presented on fixed speed wind energy conversion systems employing induction machines. These direct connected machines offer converter-less operation but must be tightly controlled to synchronize voltage and frequency for grid connection. In motor technology, excitation control and speed control are well established to achieve better efficiency. This paper aims at explaining fixed speed wind generator efficiency improvement by controlling the generator terminal voltage using tandem control of excitation capacitors and OLTC transformer to match the required rotor speed of the WTG for maximum aerodynamic conversion efficiency. Results show that improvement in energy output is possible. This could translate to millions of additional MWh into the grid for medium to large turbines over their lifetime. © 2011 IEEE