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 system comprising:
a watchdog unit coupled between a solar module and a power bus, the power bus configured to connect a plurality of solar modules to an inverter, the watchdog unit having:
a local controller configured to monitor a power line communication from a central controller and determine whether the power line communication has been interrupted for a period longer than a predetermined time or number of allowed skips,
wherein the power line communication is a signal whose modulation represents coded information;
at least one component configured to disconnect the solar module from the power bus in response to a determination by the local controller that the power line communication from the central controller has been interrupted for a period longer than the predetermined time or number of allowed skips; and
a diode coupled in series with the power bus;
wherein the watchdog unit is configured to connect the solar module to the power bus when the power line communication is not interrupted; and
a bypass circuit configured to enable current in the power bus to bypass the solar module when the at least one component disconnects the solar module from the power bus;
wherein the bypass circuit is configured to short the power bus through the watchdog unit such that current in the power bus can bypass the solar module;
wherein the bypass circuit is configured to enable current in the power bus to bypass the diode.
2. The system of claim 1 , further comprising a junction box housing the watchdog unit, the junction box to provide connectivity between the solar module and the power bus.
3. The system of claim 2 , wherein the local controller is configured to control an output voltage from the junction box.
4. The system of claim 3 , wherein the local controller is configured to operate using power from the solar module.
5. The system of claim 1 , wherein the watchdog unit is configured to determine irregularity in periodicity of the power line communication to determine whether the power line communication is interrupted.
6. The system of claim 1 , wherein the power line communication is interrupted when a threshold of irregularity is surpassed.
7. The system of claim 1 , wherein the power line communication is interrupted when the central controller fails to send a communication.
8. The system of claim 1 , wherein the power line communication is continuous or pulsed.
9. The system of claim 1 , further configured to disconnect the solar module from the power bus when the watchdog unit receives a shutdown signal.
10. The system of claim 1 , wherein skips include irregularity in the periodicity of pulses, or less than a threshold number of pulses are received, or pulses dropped below a certain threshold amplitude.
11. A system comprising:
a watchdog device coupled between a solar module and a power bus, the power bus configured to connect a plurality of solar modules to an inverter, the watchdog device configured to:
verify power line communication with a central controller,
wherein the power line communication is a signal whose modulation represents coded information; and
shutdown the solar module from the power bus if the power line communication with the central controller cannot be verified for a period longer than a predetermined time or number of allowed skips;
wherein the watchdog device comprises a diode coupled in series with the power bus; and
a bypass circuit configured to enable current in the power bus to bypass the solar module when the watchdog device shuts down the solar module from the power bus;
wherein the bypass circuit is configured to short the power bus through the watchdog device such that current in the power bus can bypass the solar module;
wherein the bypass circuit is configured to enable current in the power bus to bypass the diode.
12. The system of claim 11 , wherein to shut down the solar module includes disconnecting the solar module from the power bus.
13. The system of claim 11 , wherein to shut down the solar module includes reducing an output voltage of the solar module.
14. The system of claim 11 , wherein the power line communication can be continuous or pulsed.
15. The system of claim 11 , further configured to shut down the solar module if a shutdown signal is received.
16. The system of claim 11 , further configured to wait for a restart signal.
17. The system of claim 11 , further configured to draw energy from a backup energy source when a primary energy source is not available.
18. The system of claim 11 , wherein skips entails irregularity in the periodicity of pulses, or less than a threshold number of pulses are received, or pulses dropped below a certain threshold amplitude.
19. A system comprising:
a watchdog unit coupled between a solar module and a power bus, the power bus configured to connect a plurality of solar modules to an inverter, the watchdog unit having:
a local controller configured to monitor a power line communication from a central controller and determine whether the power line communication has been interrupted for a period longer than a predetermined time or number of allowed skips,
wherein the power line communication is a signal whose modulation represents coded information;
at least one component configured to lower a voltage of the solar module in response to a determination by the local controller that the power line communication from the central controller has been interrupted for a period longer than the predetermined time or number of allowed skips; and
a diode coupled in series with the power bus;
wherein the watchdog unit is configured to increase back the voltage of the solar module when the power line communication is not interrupted; and
a bypass circuit configured to enable current in the power bus to bypass the solar module when the at least one component disconnects the solar module from the power bus;
wherein the bypass circuit is configured to short the power bus through the watchdog unit such that current in the power bus can bypass the solar module;
wherein the bypass circuit is configured to enable current in the power bus to bypass the diode.
20. The system of claim 19 , wherein the power line communication can be periodic or non-periodic.
21. The system of claim 19 , wherein skips entails irregularity in the periodicity of pulses, or less than a threshold number of pulses are received, or pulses dropped below a certain threshold amplitude.