Soft-Switched Ultrahigh Gain DC–DC Converter With Voltage Multiplier Cell for DC Microgrid

In this article, a soft-switched modular nonisolated converter is proposed for distributed generation systems. By integrating flyback energy delivering circuit to the interleaved boost converter, ultrahigh-voltage gain and high efficiency are achieved with reduced duty ratio. Cockcroft–Walton based multiplier cell extensively reduces voltage stress on the active switches. Voltage spikes across mosfets caused by leakage inductance and interconnection of primary-secondary windings are alleviated by adjoining the active switch based auxiliary circuit. Thus, low voltage rating switches (small Rds(on)) are employed. Furthermore, the clamp circuit realizes wide-load-range zero-voltage switching (ZVS) turn-on and, reduced falling current magnitudes ensures low turn-off losses for all the mosftets. Also, leakage-energy is recycled to the load. Indeed, leakage-energy effectively limits the rate of fall-current (dif/dt) through power diodes and alleviates the reverse-recovery problem by turning-off them with zero-current switching. Furthermore, during turn-on, ZVS is achieved for all the diodes. Thus, voltage spikes across the diodes are suppressed without needing any snubber. Minimized voltage stresses, lowered on-state and switching losses of the semiconductor devices, altogether, improves the efficiency. A 600-W prototype working at 100 kHz is developed in the laboratory to validate the design analysis. Measured efficiency at rated-load is 95.81% and maximum efficiency is 96.65%.