Comparative analysis of fractional order PI and integer order PI based controller for hybrid standalone wind energy conversion system

This article presents a comprehensive analysis of fractional order proportional integral (FOPI) and integer order proportional integral (IOPI) controllers for voltage and frequency control of a variable speed hybrid standalone wind energy conversion system. Variations in wind velocity and load introduce the changes in terminal voltage and frequency. This can be controlled by an appropriate controller with satisfactory response. In this work, FOPI controller is proposed for controlling the terminal voltage and frequency. Dual second order generalized integral phase locked loop (DSOGI-PLL) is utilized to track the system frequency. Fractional-order controller is implemented for voltage source converter, which makes it robust due to their fractional characteristics. FOPI (PI lambda) provides an additional degree of freedom (lambda), along with proportional gain (K-p) and integral gain (K-i). The robustness of the controller is validated through simulations in MATLAB/simulink and its performance is compared with IOPI under various operating conditions. The results show that, FOPI based controller is able to maintain the terminal voltage and frequency constant with improved transient response in comparison to IOPI. Finally, performance assessment of the controllers is carried out using performance metrics.