Design and Analysis of Triplen Controlled Resonant Converter for Renewable Sources to Interface DC Micro Grid

This paper presents a triplen controller for a dc-dc resonant converter, which provides excellent load voltage regulation with respect to wide variations in input voltage from renewable sources in a dc micro grid. The control provides enhanced converter efficiency and soft switching of all the switches from rated load to very light load. In the proposed control, duty cycle modulation, switching frequency modulation, and phase shift modulation between active bridges are simultaneously varied in order to maintain constant dc voltage. The two control variables viz., switching frequency and duty ratio are simultaneously adjusted keeping phase shift fixed, in order to regulate voltage with respect to load variations and increase in the input voltage. Whereas, the third control variable, i.e., phase shift regulates output voltage when input from renewable sources is reduced, by keeping frequency and duty ratio fixed. The three control variables provide the greater degree of freedom. The experimental and simulation results of the programmable triplen control are presented for a resonant converter operating from the rated load of 3 kW to 5% of rated load 0.15 kW. The proposed control also tested for the input voltage range of 180-260 V (i.e., 220 V, ± 18% tolerance) in order to validate the functionality of the proposed control.