The reduction in the Common Mode Voltage (CMV) and thermal losses in semiconductors play a crucial role in designing of a new transformer-less inverter topologies for solar powered applications. The galvanic isolation and the leakage current problem due to non-availability of transformer can be addressed either by providing additional switches on the dc side or on the ac side, but this results in more number of semiconductor devices being added into the conduction paths which are switched according to the desired output requirements which further results in high conduction and switching losses indirectly effecting the efficiency of the transformer-less inverters. Hence it is important to study the existing topologies in view of the total losses, CMV and leakage current parameters together. In this review paper H5, H6 and HERIC transformer-less inverter configurations in terms of CMV, Leakage current, Conduction and Switching losses as total losses have been analyzed using PSIM2022.2 simulation software package with the availability of the thermal module. The study of total losses with CMV and leakage current will help in noting the drawbacks of the topologies discussed in this paper.
A. Transformer-less PV Inverter
Single phase transformer-less inverters are becoming more and more common for solar power applications due to their Lower cost, compact size and improved efficiency, As shown in the Fig.1 the transformer used in the PV system is removed in order to lower the price, size, losses, and weight and to improve its efficiency. As a result of this idea, numerous transformer-free PV inverter topologies have been created. The PV inverter is more cost-effective and efficient because the transformer has been removed.
The transformer's removal from the system, however, causes the galvanic isolation between the grid and the PV source to be lost. Because of this, the leakage current starts circulating in the PV system. The resonant path of parasitic elements is triggered by the Common Mode Voltage (CMV) developed in the circuit. This causes flow of high leakage currents.
These days transformer-less PV connected grid inverters are often used at a single phase beside the three phase level. Computation of losses, efficiency with constant or reduced CMV is required to overcome the cost and to achieve this good efficient inverter with minimum leakage current topology is required.
H5, H6 and HERIC transformer-less PV-inverter configurations in terms of average leg voltage, Leakage current, total losses have been evaluated using PSIM2022.2 simulation software package with the help of its thermal module.
 Zameer Ahmad and S. N. Singh, \"Comparative analysis of single phase transformerless inverter topologies for grid connected PV system,\" Solar Energy, vol. 149, pp. 245-271, 2017.
 G. Vazquez, TamasKrekes, Alejandro Rolan, Daniel Aguilar, Alvaro Luna and Gustavo Azevedo, \"Losses and CMV Evaluation in Transformerless Grid-connected PV Topologies,\" ISIE 2009 (IEEE International Symposium on Industrial Electronics),2009.
 Zameer Ahmad and S. N. Singh, \"Improved modulation strategy for single phase grid connected transformerless PV inverter topologies with reactive power generation capability\",Solar Energy, 2018.