SYSTEMS AND METHODS FOR AN ENHANCED WATCHDOG IN SOLAR MODULE INSTALLATIONS
Systems and methods for automatically or remotely rendering a solar array safe during an emergency or maintenance. A watchdog unit is disclosed for monitoring a signal from a central controller. If the signal is lost, interrupted, or becomes irregular, or if a shutdown signal is received, then the watchdog unit can shut down one or more solar modules. Shutting down a solar module can mean disconnecting it from a power bus of the solar array or lowering the solar module voltage to a safe level.
1 . A method implemented in a photovoltaic system, comprising:
connecting an inverter between a power bus of the photovoltaic system and a power grid, wherein the photovoltaic system includes a plurality of photovoltaic modules, each respective photovoltaic module of the photovoltaic modules having a watchdog unit coupled between the respective photovoltaic module and the power bus, the watchdog unit comprising:
a local controller; and
at least one switch coupled between photovoltaic cells of the respective photovoltaic module and the power bus;
monitoring, by the watchdog unit, a communication from a central controller;
determining, by the watchdog unit, whether the communication from the central controller has been interrupted for a time period longer than a predetermined number of allowed skips;
connecting, by the at least one switch, power from the photovoltaic cells of the respective photovoltaic module to the power bus in absence of a determination by the local controller that the communication from the central controller has been interrupted for a time period longer than the predetermined number of allowed skips; and
disconnecting, by the at least one switch, power from the photovoltaic cells of the respective photovoltaic module from the power bus in response to a determination by the local controller that the communication from the central controller has been interrupted for a time period longer than the predetermined number of allowed skips.
2 . The method of claim 1 , wherein the photovoltaic system further comprises the central controller.
3 . The method of claim 2 , further comprising:
performing the communication from the central controller via a wired connection.
4 . The method of claim 2 , further comprising:
performing the communication from the central controller is via a wireless connection.
5 . The method of claim 1 , further comprising:
controlling, by the local controller a duty cycle of the at least one switch to control an output voltage of the respective photovoltaic module.
6 . The method of claim 3 , further comprising:
powering, by the respective photovoltaic module, the local controller.
7 . The method of claim 1 , further comprising:
receiving, in the local controller, a shutdown signal from the central controller in addition to detecting that the communication from the central controller has been interrupted for a time period longer than a predetermined number of allowed skips.
8 . The method of claim 7 , further comprising:
disconnecting, by the at least one switch, power from the photovoltaic cells of the respective photovoltaic module from the power bus in response to the local controller receiving the shutdown signal.