Reactive power generation by DFIG based wind farms with AC grid connection

Reactive power generation by wind farms, which must operate similar to other conventional power plants, is a major concern during both steady state and fault conditions. This paper addresses the reactive power generation of offshore wind parks using doubly-fed induction generators (DFIGs) connected to the main grid with long cables along with reactive power compensating devices. During steady-state operation, reactive power can be generated with minimum power loss of wind energy system while meeting the grid code requirement. This is an optimization problem which, in this paper, is solved using a new adaptive particle swarm optimization (APSO) embedded in the Newton-Raphson load flow program. During grid disturbance, the wind power generators have to provide voltage support by increasing reactive current supply. The paper also discusses control measures which enable DFIG based wind turbines to provide effective voltage support and is demonstrated on a real offshore wind farm, which is currently in planning stage, in Germany.