Integral terminal sliding mode control to provide fault ride-through capability to a grid connected wind turbine driven DFIG

With the increased number of wind turbines being directly connected to the power grid comes new challenges regarding grid integration. Fault ride through capability during voltage sags are among the most challenging issues. Conventional ride through techniques result in a compromised control of the turbine shaft and grid current during deep voltage sags. In this paper, an integral terminal sliding mode controller is designed to control the Rotor Side Converter during deep voltage sags. In addition, to further improve the performance of the DFIG during voltage sags, an inverter and three single phase transformers are placed in series with the generator which is controlled using a Fuzzy logic controller. Computer experiments were carried out to validate the proposed control approach. Results clearly show that the proposed controller is very effective in maintaining the currents and voltages of the DFIG bus within acceptable ranges during deep voltage sags, hence preventing damages to the rotor side converter and ensuring the WT remains connected to the grid during such faults.