Computers and Electrical Engineering 68 (2018) 192–203 Contents lists available at ScienceDirect Computers and Electrical Engineering journal homepage: www.elsevier.com/locate/compeleceng Highly reliable inverter topology with a novel soft computing technique to eliminate leakage current in grid-connected transformerless photovoltaic systems  S. Kirthiga * , N.M. Jothi Swaroopan Department of Electrical and Electronics Engineering, R.M.K. Engineering College, Kavaraipettai, Tamilnadu 601026, India a r t i c l e i n f o Article history: Received 7 September 2017 Revised 13 March 2018 Accepted 14 March 2018 Keywords: Photovoltaic system Grid-connected Inverter Leakage current Topology a b s t r a c t Grid-connected transformerless photovoltaic inverters are widely accepted in the renew- able energy market, owing to their high power density, low cost, and high efficiency. How- ever, the leakage current is the main issue in these inverters, which is to be investigated carefully. In this study, leakage current analysis of both transformer and transformerless bridge inverter topologies are widely investigated. Based on that, a new topology and mod- ulation technique is proposed to eliminate the leakage current in the system. The mecha- nism of a creating high-impedance path between the photovoltaic module and the system, by properly isolating them in the freewheeling state and maintaining a constant common mode voltage in all the switching states, is elaborately discussed in this paper. The ex- perimental results are finally presented to validate the proposed topology with respect to other conventional topologies. © 2018 Elsevier Ltd. All rights reserved. 1. Introduction Photovoltaic (PV) systems have become very popular in the renewable energy market. This popularity is mainly due to their wide usage in all the energy markets such as the residential, commercial, and industrial sectors. Although many solar thermal methods have been developed to tap the energy from the sun, the PV system is considered as a most effective, because of its high efficiency, small size, low cost, and light weight. PV systems are mostly designed either as standalone or grid-connected modules. The latter is widely used in the market, because it feeds energy into the grid. Generally, a PV array, inverter, and grid filters are used in a grid-connected PV system. PV modules are the basic struc- tural units of a PV array. They exhibit capacitance with respect to ground, called parasitic capacitance [1–3]. This parasitic capacitance increases if there is a large conducting surface and powerful electric field in the PV arrays. Broadly, transformer and transformerless topologies are used in the inverter sections. In transformer inverter topology, the use of a low-frequency transformer (LFT) provides better galvanic isolation between the PV modules and the grid. However, they reduce the overall efficiency by 2% and also increase the bulk size. The problem of bulk size is resolved by using a high-frequency transformer (HFT). It only reduces the size of the system, but the overall efficiency of the system is further reduced because it needs additional power frequency conversion stages [4,5].  Reviews processed and recommended for publication to the Editor-in-Chief by Guest Editor Dr. A. P. Pandian. * Corresponding author. E-mail address: rndkirthiga@gmail.com (S. Kirthiga). https://doi.org/10.1016/j.compeleceng.2018.03.022 0045-7906/© 2018 Elsevier Ltd. All rights reserved.