Fractional Order Control of Three Level Dual Active Bridge Converter for EV Applications

This paper outlines a solar photo-voltaic based EV charger which has a bidirectional flow of active and reactive powers. A modified 3 level Dual Active Bridge (3-L DAB) converter is employed for bidirectional power flow with inherent soft switching. In comparison to a normal DAB, a 3L-DAB lessens voltage stress, enables working with lower voltage rated devices with better performance characteristics, and lowers conduction and switching loss of power devices. The paper illustrates the different modulation strategies of DAB. It also explains fractional order proportional resonant controller (FOPR) incorporated with triple phase shift modulation of three level DAB. The fractional exponents in the integro-derivative parts of the proposed FOPR controller results in a controller with an additional degree of freedom. The phase delay can be improved across a broad frequency range when compared to the conventional proportional-resonant controllers because of the additional degree of freedom. The simulation of the proposed converter is carried out in MATLAB/ Simulink. The three level voltage obtained in simulation is illustrated. The presence of zero level completely eliminates the reactive power component. Also the performance of the same is verified under varying solar irradiance conditions. It is shown that irrespective of the changes in solar insolation, the FOPR controller can effectively take care of the sudden changes in the input. Also the performance of FOPR is compared with PI, PID and PR controllers w.r.t efficiency and settling time.