Multi-terminal LVDC system for optimal acquisition of power in wind-farm using induction generators

Optimal wind-power acquisition requires automatic tracking of the optimum wind-turbine speed for the prevailing wind velocity. As the wind velocity keeps changing with time so the wind-turbine must keep adjusting its speed. In a wind-farm, the wind velocities depend on the locations of the wind-turbines, each of which has its optimal turbine speed at any given time. With an eye to costs, the wind-farm of this paper is conceived as operating with cheap induction generators driven by variable-speed wind-turbines, without the expense of speed governors. This paper shows that the voltage-source converters of LVDC (low voltage direct current) transmission systems (which are now commercially available) can be tailored as speed-sensorless drives of the wind-turbine induction generators, while meeting the objective of optimal wind-power acquisition. The LVDC system aggregates the power of many wind-turbine induction-generator units into a DC grid. Then a DC voltage regulator inverts the collected power into a 3-phase AC electric utility grid.