RESEARCH ARTICLE Single‐phase common mode transformer‐less soft‐switching grid‐connected inverter with eliminated leakage current Mehdi Tofigh Azary 1 | Mehran Sabahi 1 | Ebrahim Babaei 1,2 1 Faculty of Electrical and Computer Engineering, University of Tabriz, Tabriz, Iran 2 Engineering Faculty, Near East University, Mersin, Turkey Correspondence Mehran Sabahi, Faculty of Electrical and Computer Engineering, University of Tabriz, Tabriz, Iran. Email: sabahi@tabrizu.ac.ir Summary In this paper, a single‐phase single‐stage soft‐switching transformer‐less grid‐ tied common mode inverter is proposed, which is useful for injection of power from the photovoltaic (PV) panels to the grid. One of the output ports of the PV panel in the proposed topology can be connected directly to the neutral point of the grid to eliminate the leakage current. The proposed topology has buck‐ boost ability, besides soft switching capability to have a proper efficiency. Fur- thermore, the proposed converter can operate in unity power factor, therefore the proposed converter has most of the features needed for a PV inverter. A full analysis of the converter is done. Also, a suitable switching algorithm for cor- rect operation of the converter is presented. Moreover, the design technique for the passive elements of the topology is demonstrated. The voltage gain of the converter is calculated. The leakage current of the proposed inverter due to the low‐ and high‐frequency voltage ripple of the PV panel has been discussed. Simulation results in PSCAD EMTDC plus experimental results from a laboratory prototype are added to substantiate the theoretical results. Eventually, a comprehensive comparison study is presented to compare the proposed topology with the most similar converters. KEYWORDS common mode inverter, leakage current, PV, soft‐switching, transformer‐less grid‐connected inverter 1 | INTRODUCTION Photovoltaic transformer‐less inverters are preferred in grid‐tied applications because of their lower size, weight, and cost compared with inverters with galvanic isolation. However, obtaining higher efficiency and eliminating the leakage current are two main challenges in designing new transformer‐less grid‐tied inverters. 1,2 Besides conventional transformer‐less grid‐tied inverters such as H5, 3 OH5, 4 H6, 5 and HERIC, 6 some new topologies have been presented recently for better elimination of the leakage current and enhancement of the efficiency. Presented topologies in Guo 7,8 are current source H5 and H7 inverters, respectively, which apply space vector modulation for further elimina- tion of the leakage current; however, the leakage current is not completely zero in these converters. In addition, draw- backs of the conventional transformer‐less grid‐tied inverters like hard switching, lack of buck‐boost ability, and low efficiency still exist in CH5 and CH7. In transformer‐less grid‐connected inverter presented in Barater et al, 9 the negative terminal of the PV panel is connected to the neutral point of the grid, which extremely increases the reliability and suppresses the leakage current. On the opposite, this converter does not have buck‐boost and soft switching capability, which lowers the efficiency Received: 8 January 2018 Revised: 12 December 2018 Accepted: 25 January 2019 DOI: 10.1002/cta.2612 Int J Circ Theor Appl. 2019;1–24. © 2019 John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/cta 1