Closure to Discussion on “A Genetic Algorithm-Based Low Voltage Ride-Through Control Strategy for Grid Connected Doubly Fed Induction Wind Generators”

Abstract

Regarding the second comment, it should be pointed out that the only reason the response of the conventional control system is cited in Fig. 11 is to show that with the proposed modification of the conventional control system, the DFIG manages to ameliorate its overall response and ride-through the fault without any auxiliary hardware. There is no point to compare the effectiveness of the two systems, as in real cases, the conventional control system cannot ride through the fault by itself, but it also requires a crowbar in order to protect the DFIG. As mentioned in the introduction, during the crowbar activation, the DFIG is converted to a conventional squirrel-cage induction generator absorbing a large amount of reactive power from the grid. On the contrary, using the proposed method, the rotor side converter is not disabled during the fault, so it is possible to supply reactive power to the grid in order to support the voltage recovery, as imposed by several grid codes. In the case studied, the grid voltage, being supported by the proposed control system, recovers quickly, so there is no need for large amounts of reactive power from the DFIG after the fault. However, it is obvious that while the ac voltage remains below its reference value, the DFIG delivers the required amount of reactive power to the grid, in order to support the grid voltage. Once again, we emphasize that Fig. 11 shows a no-realistic response of a DFIG, because in a real case, the control system would protect the wind turbine through the crowbar just after the occurrence of the fault.