A High Step-Up Isolated DC-DC Converter Based on Cascaded Greinacher Voltage Multiplier

Abstract

High step-up converters are required and used in photovoltaic applications, due to low voltage of photovoltaic modules. In this paper, an isolated dc-dc high step-up SEPIC with a Greinacher voltage quadrupler cell is proposed. It has the advantage of continuous input current, high efficiency, high voltage gain, isolation and demands a single switch, being suitable for low power grid-tie photovoltaic systems. The derivation of converter, the operating principles and steady-state analysis are presented, including the detailed analysis of resonant stage, where the value of primary side capacitor is taken into account. Besides that, effects of transformer winding capacitances on converter operation are investigated. Experimental results on a 37.4/400 V, 50 kHz and 200 W prototype are presented to validate the proposed topology and concept, where the maximum efficiency obtained is 97.75%.

Keywords

• Isolated SEPIC
• Magnetizing current
• Voltage step-up cells