A multilevel energy buffer and voltage modulator for grid-interfaced micro-inverters
Author(s)Chen, Minjie; Perreault, David J.; Afridi, Khurram
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Micro-inverters operating into the single-phase grid from solar photovoltaic (PV) panels or other low-voltage sources must buffer the twice-line-frequency variations between the energy sourced by the PV panel and that required for the grid. Moreover, in addition to operating over wide average power ranges, they inherently operate over a wide range of voltage conversion ratios as the line voltage traverses a cycle. These factors make the design of micro-inverters challenging. This paper presents a multilevel energy buffer and voltage modulator (MEB) that significantly reduces the range of voltage conversion ratios that the dc-ac converter portion of the micro-inverter must operate over by stepping its effective input voltage in pace with the line voltage. The MEB also functions as an active energy buffer to reduce the twice-line-frequency voltage ripple at the output of the solar panel. The small additional loss of the MEB can be compensated by the improved efficiency of the dc-ac converter stage, leading to a higher overall system efficiency. A prototype micro-inverter incorporating a MEB, designed for 27 V to 38 V dc input voltage, 230 V rms ac output voltage, and rated for line cycle average power of 70 W, has been built and tested in grid-connected mode. It is shown that the MEB can successfully enhance the performance of a single-phase grid-interfaced micro-inverter by increasing its efficiency and reducing the total size of the twice-line-frequency energy buffering capacitance.
DepartmentMassachusetts Institute of Technology. Department of Electrical Engineering and Computer Science; Massachusetts Institute of Technology. School of Engineering
Proceedings of the 2013 IEEE Energy Conversion Congress and Exposition
Institute of Electrical and Electronics Engineers (IEEE)
Chen, Minjie, Khurram K. Afridi, and David J. Perreault. “A Multilevel Energy Buffer and Voltage Modulator for Grid-Interfaced Micro-Inverters.” 2013 IEEE Energy Conversion Congress and Exposition (September 2013).
Author's final manuscript