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%.