High-boost dc-ac inverters are used in solar photovoltaic
(PV), fuel cell, wind energy, and uninterruptible power
supply systems. High step-up and step-down capabilities and
shoot-through immunity are some of the desired properties of an
inverter for a reliable, versatile, and low-distortion ac inversion.
The recently developed Z-source inverter (ZSI) possesses these
qualities. However, the realization of ZSI comes at a cost of higher
passive component count as it needs two sets of passive filters. A
switched boost inverter (SBI) has similar properties as ZSI, and
it has one L-C pair less compared to ZSI, but its gain is less than
ZSI. This paper proposes the current-fed switched inverter (CFSI)
which combines the high-gain property of ZSI and low passive
component count of SBI. The proposed inverter uses only one L-C
filter and three switches apart from the inverter structure. The
inverter topology is based on current-fed dc/dc topology. Steadystate
analysis of the inverter is presented to establish the relation
between the dc input and the ac output. A pulse width modulation
(PWM) control strategy is devised for the proposed inverter. An
experimental prototype is built to validate the proposed inverter
circuit in both buck and boostmodes of operation. A 353-V dc-link
and a 127 V (rms) ac are obtained from a 35.3-V dc input to
demonstrate the boost mode of operation. A 200-V dc-link and a
10.5-V (rms) ac are obtained from a 37.8-V dc input to verify the
buck mode of operation of CFSI.
Index Terms—Current-fed dc/dc topology, electromagnetic
interference (EMI) immunity, switched boost inverter (SBI),
Z-source inverter (ZSI).
I. INTRODUCTION
VOLTAGE SOURCE INVERTERS (VSIs) find wide application
in uninterruptible power supplies, solar photovoltaic
(PV) and fuel-cell applications, wind power systems,
hybrid electric vehicles, industrial motor drives, etc. [1], [2].
The limitation of traditional VSI is that its peak ac output
voltage is always less than the input dc-link voltage [3]. Also,
shoot-through in any of the inverter legs is not permitted as
it results in flowing of high short-circuit current. Therefore,
a dead-band is introduced between the switching signals of
complementary switches of the inverter legs, which, in turn,
causes ac output distortion. High-boost inversion is essential
in small rooftop solar PV/fuel-cell applications when it is
connected to 110–240-V ac systems. For such applications,
either a step-up transformer at the inverter output or a two-stage
boost-inverter structure is used. Inverter systems with step-up
transformers having a high turns ratio are generally bulky and
noisy. Therefore, the alternate option is to go for a transformer-