Smart junction box for photovoltaic systems
OwnerMei Zhang, Jianhong Kanginventors
Life of this patent
Estimating the term…
Abstract
A “smart” junction box for photovoltaic systems provides electrical measurements of strings of photovoltaic cells to detect premature photovoltaic cell degradation, bypass diode failure, and arcing, and report the same to a central location and/or to provide for automatic disconnection of a given string of photovoltaic cells. The smart junction box also provides general reporting of electrical characteristics to the central system and allows disconnection by command from the central system.
Claims14
A smart junction box for series connected photovoltaic units providing bypass diodes, the smart junction box comprising:
- a housing providing terminals receiving electrical connections to series connected photovoltaic units at multiple electrical junctions between the series connected photo voltaic units as joined by the bypass diodes;
- a remote communication circuit for communicating with a central station;
- I/O circuitry communicating with the terminals to digitize electrical measurements of the electrical junctions;
- and
- a processor receiving the digitized electrical measurements and executing a stored program to monitor the digitized electrical measurements across at least one photovoltaic unit to detect electrical arcing in at least one of the photovoltaic units to provide a signal through the remote communication circuit to the central station
- wherein the detection of electrical arcing monitors a voltage across at least one photovoltaic unit to:
- (a) identify a dominant frequency over time;
- (b) subtract the dominant frequency over time from the monitored voltage to produce a corrected voltage;
- and
- (c) analyze a trend of a spectral amplitude of the corrected voltage as a function of frequency to indicate arcing when the trend meets a predetermined criterion.
An arc detection system for photovoltaic units providing bypass diodes, the arc detection system comprising:
- terminals for receiving electrical connections to photovoltaic units;
- a remote communication circuit for communicating with a central station;
- I/O circuitry communicating with the terminals to digitize electrical measurements of electrical junctions;
- and
- a processor receiving the digitized electrical measurements and executing a stored program to monitor the digitized electrical measurements across at least one photovoltaic unit to detect electrical arcing in the photovoltaic units;
- wherein the detection of arcing monitors a voltage and/or current across at least one photovoltaic unit to:
- (a) identify a dominant frequency over time;
- (b) subtract the dominant frequency over time from a measured voltage and/or current to produce a corrected voltage;
- and
- (c) analyze a trend of a spectral amplitude of the corrected voltage and/or current as a function of frequency to indicate arcing when the trend meets a predetermined criterion.
Dependencies are inferred from the claim text.