Photovoltaic Array Systems, Methods, and Devices with Improved Diagnostics and Monitoring

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 by automatically disconnecting portions of the array during normal service (when load is not maximum, and observing the resulting change in electrical characteristics. More intensive diagnostic procedures can be launched if needed. One embodiment provides for performing monitoring or diagnostic operations on the array in daylight or at night. Another embodiment allows monitoring or diagnostic operations to be performed on a portion of the array while other parts of the array continue to collect energy. Yet another embodiment provides a safety mode for an array for maintenance or during emergencies.

1 .- 7 . (canceled) 
     
     
         8 . A method of monitoring a photovoltaic array with a plurality of strings of photovoltaic cells comprising the following steps:
 automatically electrically disconnecting one or more strings of photovoltaic cells from a photovoltaic array;   performing a diagnostic test on the strings remaining connected;   initiating an alert condition if results of the diagnostic test are outside of an expected range; and   automatically electrically reconnecting the one or more strings.   
     
     
         9 . The method of  claim 8 , wherein said diagnostic test uses a bidirectional AC-DC converter to apply a DC potential to said at least one string of photovoltaic cells. 
     
     
         10 . The method of  claim 8 , wherein said diagnostic test performs a differential comparison of the output of said modified array with respect to the electrical characteristics of the entire array. 
     
     
         11 . The method of  claim 8 , wherein said diagnostic test performs an IV curve trace on ones of said cells. 
     
     
         12 . The method of  claim 8 , wherein said steps are repeated, from time to time during normal operation, for each said string. 
     
     
         13 . The method of  claim 8 , wherein said automatically disconnecting step is performed at regular intervals. 
     
     
         14 . The method of  claim 8 , wherein said automatically disconnecting step is performed only when electrical load is below a ceiling value. 
     
     
         15 . A method of monitoring a photovoltaic array with a plurality of strings of photovoltaic cells comprising the following steps:
 automatically electrically disconnecting at least one string from said combined set of strings to produce a modified set of strings;   measuring electrical output characteristics of said modified set of strings;   comparing said electrical output characteristics to a baseline value, to thereby ascertain the result of said disconnecting operation; and   transmitting an alert if said comparing step shows that the electrical output characteristics found by said comparing step are outside of an expected range; and   automatically electrically reconnecting said at least one string.   
     
     
         16 . The method of  claim 15 , wherein said measuring step uses a bidirectional AC-DC converter to apply a DC potential to said at least one string of photovoltaic cells. 
     
     
         17 . The method of  claim 15 , wherein said steps are repeated during normal operation for each said string. 
     
     
         18 . The method of  claim 15 , wherein said automatically disconnecting step is performed at regular intervals. 
     
     
         19 . The method of  claim 15 , wherein said automatically disconnecting step is performed only when electrical load is below a ceiling value. 
     
     
         20 .- 32 . (canceled) 
     
     
         33 . A photovoltaic power generation system comprising:
 Two or more strings of photovoltaic cells;   A first circuit path with conductors switchably connected to each string of photovoltaic cells;   A second circuit path with conductors switchably connected to each string of photovoltaic cells;   Wherein first and second circuit paths are configured so that, in a first switchable configuration, corresponding to a normal operating mode, a positive end of each string of photovoltaic cells is connected to the first circuit path and in a second switchable configuration, corresponding to a safety mode, a positive end of one string and a negative end of a second strong are connected to said first circuit path and the opposite end of each string is connected to said second circuit path.   
     
     
         34 . A solar energy system which implements the methods of any of the preceding claims.