Symmetrical Angle Switched Single-Phase and Three-Phase Rectifiers: Application to Micro Hydro Power Plants

Micro-size hydro power plants are commonly used at remote areas to supply islanded AC micro-grids. A typical way to control grid frequency is to manipulate active power dissipated in ballast loads by AC/AC converters. However, conventional asymmetrically switched thyristor controlled converters consume reactive power degrading the power factor at the generator output and transmission efficiency. In this paper the operation of a symmetric angle switched, bridged three-phase rectifier and three single-phase rectifiers connected in series with ballast load, are studied to improve the power factor of the system. The objective is to evaluate the characteristics of these two configurations to improve the power factor by reactive power compensation in the frequency control of an islanded micro hydropower system.