Abstract
This paper proposes a novel high step-up nonisolated single switch dc-dc converter suitable for regulating dc bus in various microsources especially for photovoltaic (PV) sources. Quadratic boost and switched-capacitor technique are used as primary and secondary circuits, respectively. A coupled inductor is applied to make a connection between them, so a high dc voltage gain is achieved. High efficiency is yield where voltage stress on active switch is alleviated by clamped capacitor; consequently, smaller R DS(ON) for power switch is required. On the other hand, input current of the proposed converter is continued, hence stress on the input source is reduced. The operating principles and steady-state analyses are discussed in detail for both continuous and discontinuous conduction modes. Also, the boundary condition is computed. To verify the performance of the proposed converter and theoretical calculations, a 250-W prototype converter is implemented with an input voltage of 24 V and an output voltage of 400 V designed especially for PV sources in continuous conduction mode operation. Finally, simulation results are confirmed by experimental results; maximum efficiency is occurred at 150 W and full-load efficiency is 92.96%.
I. INTRODUCTION
NOWADAYS, using renewable sources of energy is more and more expanded all over the world. Some of these sources include solar cell, fuel cell, and wind turbine [1]-[4]. In using the power of mentioned renewable sources by AC load or network, the voltage level value should be increased enough to be inverted to desired AC value [5]. PV-panel modules can be used in series connection to obtain higher dc voltage [6], [7], but shading problem and decreasing reliability are prohibitive in this method [8]-[12]. Therefore, DC-DC boost converter is better way instead of numerical series PVpanel modules. Conventional DC-DC boost converter is one of the common ways for increasing voltage gain. However, high extra duty cycle is required and this results in reduction of efficiency. In addition, voltage stress on the switch is equivalent to output voltage [13]-[16].
V. CONCLUSION
A novel topology of non-isolated high step up dc-dc converter has been introduced into renewable sources of energy by using quadratic boost as primary and switchedcapacitor as secondary part of circuit. Input current of converter is continuous, so current stress on source is reduced. To produce higher voltage gain in this topology, only one switch is used which reduced complexity of converter control. Furthermore, the energy of leakage inductance has recycled throughout of clamped capacitor; the voltage stress on the main switch is clamped because of the existence of clamed capacitor, so low on-state resistance RDS(on) can be chosen. To verify the proposed converter, a prototype 250W is implemented with 24V input and 400V output voltage, output waveforms have illustrated in CCM operation, and efficiency is approximately 93% in full-load. Theoretical calculations are confirmed by experimental results to some extent.
