Reconfigurable high step‐up DC to DC converter for microgrid applications

Abstract

AbstractHere, a high gain DC–DC converter which is based on switched capacitor (SC) and switched LCL (SLCL) cells is presented. The diode employed in the classical passive switched inductor (SI) cell is replaced by a capacitor in the proposed SLCL cell to achieve higher voltage gain. Two switches—one each in the positive and negative DC rails of the supply are employed to charge and discharge the inductors of SLCL cells. A generic structure comprising of N and M number of SLCL cells in the positive and negative DC rails respectively along with K number of SC cells is presented. To validate the proposed gain extension concept, a two‐switch based converter comprising of 2 SLCL and 1 SC cells is synthesized and its operation is described in detail. The voltage gain expression of the proposed SLCL‐SC converter is derived. Experimental results are obtained from a 25 to 380 V prototype converter which operates at a full‐load efficiency of 94.22% at 200 W. Since the switches employed in the proposed converter are operated at a moderate and safe duty ratio of D = 0.51, the voltage stress on the switches is about 25% of the output voltage while the diodes are subjected to even lesser voltage stress levels of only one‐fifth of the output voltage. The main salient features of the proposed topology are its (i) modular structure, (ii) ability to provide higher voltage gain values at lower duty ratios (iii) reduced voltage stress on the semiconductor devices and (iv) reduced conduction losses due to the replacement of diodes with capacitors in SLCL cells.