Single-phase Common-ground Transformerless Photovoltaic Grid-connected Inverter

There is currently significant growth in the number of grid-connected photovoltaic(PV)systems.The presence of the electrical isolation between the PV module and the grid is a very crucial aspect in determining the performance requirement as well as the utility operator’s specifications of the PV inverter design.The grid-connected PV inverter design can be classified into transformer-less and transformer-based topologies regarding galvanic isolation.Grid-connected inverters with line-frequency transformer at the inverter output were widely used in the past to isolate AC and DC part of the inverters.It has the advantage of eliminating Leakage current(LC)and Direct Current Component Injection(DCCI)into the AC grid and electrical isolation,but the major disadvantage of increasing the size and volume of inverters.This project is focused on Single-phase photovoltaic transformer-less grid-connected Inverter with no leakage current as well as less number of switches.By eliminating a line frequency transformer at the inverter output,the size and volume of inverter significantly reduce but it introduces one major potential concern of LC due to parasitic capacitance between PV arrays and switching actions which can affect the performance of utility grid and in particular,distribution transformers and electromechanical power meters.Transformer-less inverter with common-ground between the PV array and grid is proposed in this work which eliminates the leakage current.Unlike other topologies with leakage current problem between PV and output grid,there is no leakage current as the PV negative terminal and grid neutral point has the same common ground.The number of switches is reduced which also reduces the cost as well as switching losses of the inverter.Peak current control modulation strategy is used to control the grid-in current.In order to supply the current to the grid in the negative half cycle,a virtual DC bus concept is used.Simulation work has been done in MATLAB/SIMULINK.