High voltage step-up ratio, Z-source based coupled inductor DC-DC converter topolgies

DC?DC converters with high step-up voltage gain are widely used in many applications such as uninterrupted power supplies, photovoltaic systems and fuel cell systems. Theoretically, conventional boost converters can obtain high step-up voltage gain at high duty cycles. In practice, the voltage gain of boost converters is limited due to losses on inductor, capacitor, power switch and rectifier diode at high duty cycles. In this dissertation, z-source based, coupled inductor, high step-up ratio dc-dc converter topologies are proposed. The proposed topologies achieve these high voltage gains while switching at low voltages with low duty cycles. While the leakage inductances do not cause any extra voltage stress on the switch and diodes, galvanic isolation is obtained between the input and output. Simulation and experimental results are given for a prototype converter that converts 25 V dc to 400 V dc at 300 W with over 90% efficiency.Key Words : z-source, dc-dc converter, renewable energy, AC modul