Analysis and Damp of Oscillations Caused by SSR Mode in DFIG Based Wind Farm by Controlling of Stator Voltage in Conditions of Maintaining MPPT

The subsynchronous resonance (SSR) phenomenon is a condition that the wind farm exchanges energy with the electrical network at one or more of the subsynchronous frequencies. If it is not prevented, this phenomenon causes damages to the system. The SSR phenomenon occurs in two following conditions: Induction generator effect and Torsional interaction effect. The SSR occurs in the DFIG based wind farms due to the induction generator effect. In this research, by controlling the stator voltage, the SSR is mitigated or prevented with considering the maintenance of MPPT condition. So that, with direct control of the stator voltage, line current of the system is controlled indirectly and prevented from the induction generator effect. For this purpose, an additional controller called SSR damping controller is used. This controller is applied to GSC converter of the DFIG. Because the SSR depends on the speed and frequency of the generator rotor, the rotor speed is selected as the input signal of this controller. In order to simulate, the MATLAB/SIMULINK software has been used. To verify the proposed method, a DFIG based wind farm connected to an infinite bus by a series capacitor compensated transmission line, is considered.