Stacked Controlled-Cell Power Conversion Architecture for Grid-Connected Photovoltaic Systems

Problem: -Low extracted energy of current MPP operation of a series- or parallel- connected set of PV cells -Energy loss due to cell-current mismatches Technology: The invention provides a new architecture to assemble PV cells to yield the optimal energy output. An integrated circuit switched-mode MPP controller is connected to each cell, forming a ΓÇ£controlled cellΓÇØ. The controlled cells can then be stacked in series to achieve a high output voltage, which enables the use of a high-power, highly efficient centralized inverter in grid-tied applications. The MPP controllers can preferably be fabricated in a low-voltage CMOS process, with power switches and control logic all integrated on a monolithic die. In the new architecture, individual cells can each be operated at any current level below the current in the series controlled-cells string connections. By adjusting the duty ratio, the local MPP tracker can autonomously achieve MPP operation so long as the cell current at its MPP is equal to or less than that in the string. In this manner, the system level controller, implemented by the grid-interface inverter, can adjust the string current such that there is just sufficient string current available for the cell with the highest MPP current. Christopher Noble crn@mit.edu