A comparative analysis of the 5L-AH6 and 5L-SC topologies for grid-connected transformer-less multilevel inverters for PV systems

In this paper a comparative evaluation of the efficiency for two multilevel topologies used in grid-connected transformer-less applications is presented. The proposed analysis is focused in two of the most important characteristics in grid-connected converters, such as the leakage currents which appear between the stray capacitances and the ground path and the efficiency. The efficiency evaluation includes an analysis of power losses distribution in the semiconductors providing information to develop a good thermal design of the converter. For the evaluation is considered that the overall DC link is fixed to the desired voltage value and the capacitor voltages are balanced. Also, the topologies selected are connected to the grid by means of an ideal L filter to inject active power to the grid. In both cases, the proposed modulation strategy is based in the Sinusoidal Level Shifted Pulse Width Modulation (SLSPWM). Numerical results of the analysis of common mode voltage and the efficiency curves are presented.

[1]  Pablo Sanchis,et al.  Ground currents in single-phase transformerless photovoltaic systems , 2007 .

[2]  Gerardo Escobar,et al.  Transformerless single-phase multilevel inverter for grid tied photovoltaic systems , 2014, IECON 2014 - 40th Annual Conference of the IEEE Industrial Electronics Society.

[3]  Gerardo Escobar,et al.  A model-based controller of a three-level stacked-cell grid connected converter , 2015, IECON 2015 - 41st Annual Conference of the IEEE Industrial Electronics Society.

[4]  G. Vazquez,et al.  Comparative analysis of single-phase grid connected transformerless photovoltaic inverter topologies , 2013, 2013 IEEE International Autumn Meeting on Power Electronics and Computing (ROPEC).

[5]  Marco Liserre,et al.  Grid Converters for Photovoltaic and Wind Power Systems , 2011 .

[6]  Huan Yang,et al.  Topologies and control strategies of multi-functional grid-connected inverters for power quality enhancement: A comprehensive review , 2013 .

[7]  Shaojun Xie,et al.  Leakage Current Analytical Model and Application in Single-Phase Transformerless Photovoltaic Grid-Connected Inverter , 2010, IEEE Transactions on Electromagnetic Compatibility.

[8]  P. Sanchis,et al.  Transformerless Inverter for Single-Phase Photovoltaic Systems , 2007, IEEE Transactions on Power Electronics.

[9]  U. Borup,et al.  Transformerless Photovoltaic Inverters Connected to the Grid , 2007, APEC 07 - Twenty-Second Annual IEEE Applied Power Electronics Conference and Exposition.

[10]  Holmes,et al.  Pulse width modulation for power converters , 2003 .

[11]  Jih-Sheng Lai,et al.  High-Efficiency MOSFET Inverter with H6-Type Configuration for Photovoltaic Nonisolated AC-Module Applications , 2011, IEEE Transactions on Power Electronics.

[12]  G. Vazquez,et al.  Comparative evaluation of L and LCL filters in transformerless grid tied converters for active power injection , 2014, 2014 IEEE International Autumn Meeting on Power, Electronics and Computing (ROPEC).

[13]  Sigifredo Gonzalez,et al.  Performance Test Protocol for Evaluating Inverters Used in Grid-Connected Photovoltaic Systems. , 2015 .

[14]  Ehsan Afshari,et al.  Analysis and modification of the single phase transformerless FB-DCB inverter modulation for injecting reactive power , 2015, 2015 IEEE Conference on Energy Conversion (CENCON).