PV junction unit, PV junction box and method for monitoring current in PV string

摘要

A PV junction unit for joining a plurality of PV strings into a single string, comprising: a plurality of anode branch circuits; an anode busbar adapted to connect with an anode output end of each PV string via one corresponding anode branch circuit; a plurality of cathode branch circuits; a cathode busbar adapted to connect with a cathode output end of each PV string via one corresponding cathode branch circuit; resistors each of which is connected in series in one corresponding anode branch circuit connecting the anode output end of one corresponding PV string with the anode busbar, wherein each resistor has a theoretical resistance; voltage measuring devices each of which is connected in parallel with one corresponding resistor; and a processor connected with each of the voltage measuring devices, the processor configured to determine a current value in one PV string at least based on the theoretical resistance of the resistor in one anode branch circuit connected with the one PV string and based on a voltage value from the voltage measuring device in said one anode branch circuit connected with the one PV string.