Photovoltaic Array Systems, Methods, and Devices with Bidirectional Converter

Abstract

Devices, systems and methods for operating, monitoring and diagnosing photovoltaic arrays used for solar energy collection. The system preferably includes capabilities for monitoring or diagnosing an array, under some circumstances, by using a bidirectional power converter not only to convert the DC output of the array to output power under some conditions, but also, for diagnostic operations, applying a back-converted DC voltage to the array.

1 .- 19 . (canceled) 
     
     
         20 . A method for operating a photovoltaic array, comprising:
 in daylight conditions, providing DC current from photovoltaic cells to a bidirectional power converter, and operating said bidirectional power converter to provide an AC power output onto an AC connection;   in dark conditions, operating said bidirectional converter in reverse, to apply a reduced DC potential, which is less than half of the maximum voltage provided by said cells under daylight conditions, to said string of photovoltaic cells;   measuring a DC current through the string of photovoltaic cells; and   initiating an alert if the measured DC current indicates that a photovoltaic cell in the string has been disconnected.   
     
     
         21 . A solar energy system which implements the methods of any of the preceding claims. 
     
     
         22 . A photovoltaic power generation system comprising:
 a plurality of photovoltaic cells; and   a bidirectional power converter which is operatively connected to groups of said photovoltaic cells;   wherein, in a first mode of operation, said bidirectional power converter draws current from at least some ones of said groups of photovoltaic cells, and provides an AC power output onto an AC connection;   and wherein, in a second mode of operation, said bidirectional power converter draws power from one or more sources other than said photovoltaic cells, and accordingly applies a DC potential to at least some ones of said photovoltaic cells.   
     
     
         23 . The system of  claim 22 , wherein, in said second mode, said bidirectional converter is powered from said AC connection. 
     
     
         24 . The system of  claim 22 , wherein said second mode is initiated automatically, from time to time, during normal operation. 
     
     
         25 . The system of  claim 22 , wherein said second mode is initiated automatically, from time to time, during dark conditions. 
     
     
         26 . A photovoltaic power generation system comprising:
 a plurality of photovoltaic cells; and   a bidirectional power converter which is operatively connected to groups of said photovoltaic cells;   wherein, in a first mode of operation, said bidirectional power converter draws current from at least some ones of said groups of photovoltaic cells, and provides an AC power output onto an AC connection;   and wherein, in a second mode of operation, said bidirectional power converter draws power from one or more sources other than said photovoltaic cells, and accordingly applies a variable DC potential to at least some ones of said photovoltaic cells;   and wherein one or more diagnostic tests are performed during said second mode.   
     
     
         27 . The system of  claim 26 , wherein, in said second mode, said bidirectional converter is powered from said AC connection. 
     
     
         28 . The system of  claim 26 , wherein said second mode is initiated automatically, from time to time, during normal operation. 
     
     
         29 . The system of  claim 26 , wherein said second mode is initiated automatically, from time to time, during dark conditions.