Method for communication between transceivers of module level devices within a photovaltaic module level monitoring system

A photovoltaic module level monitoring system comprising:

• a photovoltaic array including at least one photovoltaic string PV comprising photovoltaic modules each having a module level device, MLD adapted to monitor and/or to control the associated photovoltaic module,
• wherein each module level device comprises a transceiver adapted to communicate with a transceiver of a base station of an inverter connected to said photovoltaic array, wherein the transceivers are coupled by associated duplexer circuits to a DC power network comprising power cables connecting the photovoltaic modules of the at least one photovoltaic string of said photovoltaic array with the base station of the inverter,
• wherein a signal amplitude of a communication signal transmitted by a transceiver via its associated duplexer circuit is adjusted automatically depending on a monitored impedance of the respective photovoltaic array,
• wherein the impedance of the photovoltaic array is determined depending on a measured communication signal or a test signal received by the transceiver of the base station of the inverter via its associated duplexer circuit and depending on a reference signal,
• wherein the reference signal comprises a calibrated communication signal with a predetermined amplitude transmitted by the transceiver of the base station of the inverter via its associated duplexer circuit,
• wherein the impedance value of the photovoltaic array is calculated depending on a turn ratio and a coupling coefficient of a transformer of the duplexer circuit coupling the transceiver of the base station of the inverter (6) to the DC power network connecting the photovoltaic modules in the respective photovoltaic string of the photovoltaic array and depending on a resistance of a voltage divider resistor connected to a primary side of said transformer, in response to the measured received communication or test signal and the reference signal, and
• wherein the signal amplitude of the communication signal, transmitted by a transmitter of the transceiver of the base station during operation of the photovoltaic array is adjusted automatically depending on the calculated impedance value of the photovoltaic array such that the amplitude of the communication signal is below a predetermined threshold value.