System and method for protection during inverter shutdown in distributed power installations
A protection method in a distributed power system including of DC power sources and multiple power modules which include inputs coupled to the DC power sources. The power modules include outputs coupled in series with one or more other power modules to form a serial string. An inverter is coupled to the serial string. The inverter converts power input from the string and produces output power. When the inverter stops production of the output power, each of the power modules is shut down and thereby the power input to the inverter is ceased.
1 . A distributed power system comprising:
a plurality of DC power converters configured to provide DC output power;
an inverter coupled, via input DC conductors, to the plurality of DC power converters and configured to convert the DC output power of the plurality of DC power converters into an AC output power to an electrical load, wherein the inverter comprises an input capacitor coupled across the input DC conductors;
a monitoring controller configured to monitor at least one electrical parameter of the electrical load and detect that the at least one electrical parameter of the electrical load is out of a predetermined specification; and
a switch circuit disposed in parallel to the input capacitor, wherein the switch circuit is activated based on the monitoring controller detecting the at least one electrical parameter of the electrical load being out of the predetermined specification.
2 . The distributed power system of claim 1 , wherein the switch circuit comprises a switch that is open during normal operation of the inverter and that is closed based on the switch circuit being activated.
3 . The distributed power system of claim 1 , wherein the switch circuit is configured, when activated, to cause a change in an input current of the inverter, and the system further comprises at least one controller configured to shut down the plurality of DC power converters based on the change in the input current.
4 . The distributed power system of claim 1 , wherein the at least one electrical parameter of the electrical load comprises a voltage of an electrical grid connected to an output terminal of the inverter.
5 . A method comprising:
monitoring, by a monitoring controller coupled to an inverter, at least one electrical parameter of an electrical load connected to an output terminal of the inverter;
detecting, by the monitoring controller, the at least one electrical parameter of the electrical load being out of a predetermined specification; and
activating, based on the detecting, a switch circuit coupled to an input of the inverter,
wherein the switch circuit is connected in parallel to an input capacitor of the inverter.
6 . The method of claim 5 , wherein the switch circuit comprises a switch connected in parallel to two input terminals of the inverter, and the activating the switch circuit comprises closing the switch.
7 . The method of claim 6 , wherein the activating the switch circuit causes a change in input current of the inverter, and the method further comprising detecting, by at least one controller, the change in input current of the inverter and causing, by the at least one controller, a shutdown of at least one DC power converter coupled to the two input terminals of the inverter.
8 . The method of claim 7 , wherein the causing the shutdown of the at least one DC power converter comprises operating the at least one DC power converter to cease outputting power.
9 . The method of claim 5 , further comprising:
monitoring a power output by the inverter, wherein the
activating the switch circuit is based on detecting a stop of power output by the inverter,
wherein the activating the switch circuit causes a change in input current of the inverter, and the method further comprising detecting, by at least one controller, the change in input current of the inverter and causing, by the at least one controller, a shutdown of at least one DC power converter coupled to the input of the inverter.
10 . The method of claim 9 , wherein the causing the shutdown of the at least one DC power converter comprises operating the at least one DC power converter to reduce input voltage of the inverter.
11 . An apparatus comprising:
an inverter coupled, via input DC conductors, to a plurality of DC power converters and configured to convert DC output power of the plurality of DC power converters into an AC output power to an electrical load; and
a switch circuit connected in parallel to an input capacitor of the inverter,
wherein the switch circuit is configured to be activated based on at least one electrical parameter of the electrical load being out of a predetermined specification.
12 . The apparatus of claim 11 , wherein the switch circuit comprises a switch connected in parallel to two input terminals of the inverter, and the activation of the switch circuit comprises closing the switch.
13 . The apparatus of claim 11 , wherein the switch circuit is configured to cause, when activated, a change in input current of the inverter.
14 . The apparatus of claim 13 , further comprising a controller configured to:
detect the change in input current of the inverter, and
cause, based on the change in input current of the inverter, a shutdown of at least one of the plurality of DC power converters coupled to the inverter.
15 . The apparatus of claim 11 , wherein:
the activation of the switch circuit is based on detecting a stop of power output by the inverter, and
the switch circuit is configured to cause, when activated, a change in input current of the inverter.