Energy from the sun is harnessed through a photovoltaic (PV) array in form of DC. This available DC voltage is converted into AC for industrial or domestic use as per the requirement. In some topologies the extracted DC voltage is stepped up to a higher level of DC using a boost or a buck-boost converter and then this stepped up DC voltage is converted into AC by the use of an inverter. However this process is pretty costly because of the larger number of components employed. An efficient alternative to this two-stage approach is the Single-Stage Inverter (SSI). SSI does the boosting of DC and inversion of the DC to AC using only a single circuit and hence the name Single-Stage Boost Inverter. SSBI give us the advantage of reduced and robust circuitry along with reliability and efficiency. This paper presents a review of the various (however not all) SSI topologies in PV systems.

Introduction

With the surge in demand for electrical energy globally [1], conventional (non-renewable) energy sources are being harnessed at a very rapid rate and pretty soon the mankind would run out these resources. The use of conventional energy sources also leads to the pollution of environment. Fig. 1a) shows a comparison between the electricity produced globally and between India, Fig. 1b). shows the coal and lignite production worldwide and in India, Fig. 1c). presents the CO2 emissions throughout the world and in India over the years from 1990 to 2015. However, with the advancements in technology, the human race has been able to harness the non-conventional (renewable) energy resources such as the wind, solar, geothermal or hydro. The non-conventional energy resources have several advantages over the conventional energy resources such as a) These resources are abundant in nature b) These are very easily available etc. By far the biggest advantage these non-conventional resources have over the conventional fossil fuels is that the former are a cleaner source of energy with no hazardous byproducts. When a comparison is done between the various renewable sources it is found that solar energy is the best option among the category. Hydro plants require a large investment in terms of capital, land and manpower. Wind power plants cannot be installed everywhere and availability of constant wind all the time can also not be guaranteed. Other options such as geothermal energy or tidal energy require sophisticated and costly technology to harness energy. Considering all the pros and cons of the several nonrenewable energy options available, solar energy tops the list. Solar energy is put to commercial or household use by first converting the sun light into DC by the help of PV array and then this DC can be converted into AC and fed to the grid or run an independent load such as street lights or water pumps for irrigation etc. Since the PV output depends on solar irradiation and the ambient temperature, to extract maximum power from the PV module maximum power point tracking (MPPT) is used as a control technique [2]. Based on the number of power processing stages PV inverters can be put under two different categories multi-stage inverters and single-stage inverters. A multi stage inverter employs more than one power processing stage [3] where in one or many stages achieve the task(s) of boosting the DC output from PV array and/or galvanic isolation with the final stage being the conversion of the boosted DC into high-quality AC. However most of the PV inverters employ a two-stage power conversion process [4–۶].