Capacitor-less Photovoltaic (PV) Cell-Level Power Balancing Using Diffusion Charge Redistribution

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Professor Steven Leeb
Department of Electrical Engineering and Computer Science, MIT
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Al-Thaddeus Avestruz
Department of Electrical Engineering and Computer Science, MIT
Arthur Chang
Department of Electrical Engineering and Computer Science, MIT
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Christopher Noble
MIT Technology Licensing Officer - Clean and Renewable Energy
Patent Protection

Photovoltaic power balancing and differential power processing

US Patent Pending 2015-0144176
Differential diffusion charge redistribution for photovoltaic cell-level power balancing
IEEE Xplore, October 14, 2015: p. 567-582


Photovoltaic power modules are created by linking several photovoltaic cells to make up for the relatively low cell voltage of each individual cell. This approach attempts to harness higher power from the stronger photovoltaic cell, bypassing lower performing photovoltaic cells to extract more power from the string. 

Problem Addressed

Existing photovoltaic power modules are configured as a string of solar cells where the overall string current is limited by the available current of the lowest-performing solar cell in the string. External operating conditions such as dirt/dust accumulation and partial shading can severely impact the available power from the string. This technology makes an array of solar cells behave as a single super-cell with its own energy storage to eliminate effects on peak power tracking efficiency. 


This technology is a cell-level power balancing scheme that builds on the concept of differential power processing. The method uses diffusion charge rebalancing to improve the efficiency of energy capture in the presence of partial shading, while retaining high power and minimizing the number of external passive components. The technique not only increases energy extraction, but also improves maximum power point tracking (MPPT) efficiency under partial shading conditions. This invention does not require external passive components for intermediate energy storage, but instead uses the intrinsic diffusion capacitance of the solar cells as the main energy storage element. 


  • Removes the complexity of MPPT converters
  • Eliminates the binning process during cell manufacturing
  • Minimal possible cost for power processing
  • Removes cell-by-cell testing basis