Investigations on using DFIG for Reactive Power Ancillary Services

Abstract

The progress of any country is decided by its per capita consumption of energy. Conventional synchronous generators carry out the bulk electrical energy generation; however, use fossil fuels which are highly pollutant and also depleting in nature. The governments around the world emphases on bulk energy generation through the renewable sources like biomass, wind energy and solar energy etc. Among the renewables, extraction of energy from wind power has been maximum till date. It is well known that during the low wind conditions as well as excessive wind conditions, the wind generator rotors are stalled via hydraulic brakes. In this condition, the generated active power insignificant although the generators are still connected to the grid. A reactive power control /voltage support is one of the function that can be provided by modern wind farms equipped with variable speed wind turbine with power electronic converters. Referring to literature, there is a possibility of providing reactive power support to the grid from wind farms as a part of the ancillary services. To do so the grid side converter can be controlled to work alike STATCOM in order to balance the reactive power in the system so that the power quality issues are mitigated and the voltage is maintained at the load end. For this purpose, the energy available at the converters of the stalled DFIG's DC link capacitors may be utilized effectively for this case. The thesis contains various mathematical models of type 3 wind turbine (available in literature), determines suitable model for the required operation by setting the mechanical torque to be zero. Grid side converter of the type 3 wind turbine would be operated such that it will be able to provide reactive power to the grid for the reactive power support. The dissertation report contains the further details.