Identification and verification of hierarchy of dfig converter controls for power system damping

This article employs two decomposition techniques and the residue principles to determine the order of the converter controls of a doubly fed induction generator (DFIG) in terms of providing system damping. The dynamic model of the various components of the DFIG system - the wind turbine, induction generator, converter system, the load and transmission network are derived and 4 converter controls identified. The hierarchy analysis demonstrates that out of 4 converter controls the magnitude of the rotor applied voltage is the most effective one. The finding was verified by simulating the system through both lead-lag as well as proportional integral (PI) controller designs, the controller parameters being found through the residue principle. Simulation studies on the doubly fed generator system show that both the controller designs provide good damping to the system, the PI control being slightly superior. The controlled rotor voltage was observed to be able to avert voltage collapse in the system arising in the event of severe disturbance conditions.