Publication

Abstract : The doubly fed induction generator (DFIG)‐based windfarm is located far away from load points. Hence, the elongated transmission lines are required to transmit the generated power. The high inductive nature of the lengthier transmission line will lessen the transmission power capacity and a very simple solution is to insert the series capacitors along the lines. But this can cause an adverse effect known as sub‐synchronous resonance (SSR) oscillations in the system causing electrical instability and shaft failure. The main motive of this paper is to examine the risk of SSR effect and its damping on series compensated 2 MW DFIG‐based Wind Energy Conversion Systems. The detailed time domain analysis of SSR is carried out using the state space model of the total scheme in MATLAB/SIMULINK and the effective SSR damping control scheme is proposed. Conventionally, an additional sub‐synchronous resonance damping controller is inserted exclusively for damping of SSR oscillations along with the DFIG's own proportional integral (PI)‐based rotor side converter (RSC)‐grid side converter (GSC) controllers. The RSC‐GSC controllers are essential for the control of active‐reactive power and grid synchronization. Insertion of an additional controller in the system leads to controller interactions. In order to avoid the use of an additional SSR damping controller, an efficient fuzzy logic controller (FLC)‐based single controller is developed for RSC. This controller is an effective dual‐purpose controller and is utilized for power control as well as for damping the torque oscillations due to SSR. This work focuses on the design of fuzzy‐based effective controller by modifying DFIG's own converter controllers for the damping SSR oscillations together with its own control responsibilities. Under fast dynamic operating conditions, the conventional PI controllers of the converters are found to be ineffective as they require retuning for the better damping. This proposed fuzzy‐based RSC controller replaces the existing conventional PI‐based RSC controllers. The results are discussed for various wind speeds, compensation levels, etc. The prototype model of series compensated 1.5HP DFIG grid integrated system is developed. The effect of the RSC controller into the series compensated grid connected DFIG is analysed along with the experimental results.