Design and Tuning of Robust Fractional Order Controller for Autonomous Microgrid VSC System

• Published in: IEEE transactions on industry applications 2018-01, Vol.54 (1), p.91-101
• Main Authors: Pullaguram, Deepak, Mishra, Sukumar, Senroy, Nilanjan, Mukherjee, Monish
• Format: Article
• Language: English
• Subjects: Autonomous voltage source converter (VSC); Current control; fractional order control; Frequency control; Microgrids; Radio frequency; robust control design; Robustness; Switches; Voltage control
• ISSN: 0093-9994; 1939-9367
• DOI: 10.1109/TIA.2017.2758755

A robust controller design for the voltage control of an autonomous three-phase voltage source converter (VSC) is proposed. As compared with the conventional proportional plus integral (PI) controllers, fractional order controllers make the VSC system robust due to their fractional characteristics. The fractional PI \lambda controller has an additional degree of freedom \lambda along with k_p and k_i gains of the conventional PI controller. Detailed modeling of a VSC is used in the controller design process so as it include inner current control and filter dynamics. The outer fractional voltage controller is designed such that the VSC system satisfies a required phase margin, with improved robustness in the system and capability to attenuate the noise. The overall system stability is analyzed using both bode plot and step response, and these responses are compared with a conventional PI controller. Further, the dynamic performance of the fractional controller is evaluated by simulating the nonlinear system. A hardware prototype is also developed to demonstrate the practical realization of the controller.