Management of a wind farm and integration in the operational power system, Contribution of multilevel power electronic converters for the control of doubly fed induction machine based wind generators
This research work deals with two topics conditioning the large scale development of wind turbines into electrical grids. The first is devoted to the development of new algorithms for the control of Doubly Fed Induction Machine (DFIM) based wind energy conversion systems. Two direct current control strategies have been proposed and are based on the hysteresis square areas (HZCA) and hysteresis circular areas (HZCI). Both strategies apply an appropriate voltage vector to control the active and reactive powers delivered to the grid, and also, to balance the voltages of the inner DC bus converter. Simulation and experimental results show that the HZCI strategy is better than HZCA in terms of output voltage waveforms and harmonic contain.The second topic is dedicated to the active and reactive powers supervision in a wind farm in order to supply prescribed power references from the grid operator. This supervision is ensured by a centralized algorithm that distributes power references between wind turbines in a proportional way. These references are calculated according to the maximum production capacity of wind turbines. An analysis of the power flow in the DFIM based wind energy system has been made to identify the (P, Q) characteristic and to calculate limits in terms of reactive power compensation. The local power management of each wind system has been developed allowing the powers distribution between the stator of the DFIM and the grid side converter by considering several operating modes of the wind generator