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 providing a DC output;
an inverter coupled to the DC power converters and adapted to convert input power received on the DC output from the DC power converters to provide output power to an electrical load;
a monitoring mechanism configured to monitor at least one electrical parameter of the electrical load and detect when the at least one electrical parameter of the load is out of a predetermined specification;
a shutdown mechanism coupled to the monitoring mechanism and configured to cause the inverter to stop the output power when the at least one electrical parameter is out of the predetermined specification;
a switch disposed between the plurality of DC power converters and the inverter, wherein the switch is activated in response to the monitoring mechanism detecting the at least one electrical parameter of the load being out of the predetermined specification, and wherein the switch being activated causes a change in a current of the input power; and
at least one controller configured to shut down the plurality of DC power converters in response to the change in the current of the input power.
2. The distributed power system, according to claim 1 , wherein the plurality of DC power converters are coupled in at least one serial string.
3. The distributed power system, according to claim 1 , further comprising a protection mechanism configured to cease the input power on the DC output in response to detecting the change in the current of the input power.
4. A distributed power system comprising:
a plurality of DC power converters providing a DC output, wherein the plurality of DC power converters are coupled in at least one serial string;
an inverter coupled to the at least one serial string and adapted to convert input power received on the DC output from the DC power converters to provide output power to an electrical load;
a monitoring mechanism configured to monitor at least one electrical parameter of the electrical load and detect when the at least one electrical parameter of the load is out of a predetermined specification;
a shutdown mechanism coupled to the monitoring mechanism and configured to cause the inverter to stop the output power when the at least one electrical parameter is out of the predetermined specification;
a switch disposed between the at least one serial string and the inverter, the switch being adapted to cause a change in a current flowing through the at least one serial string, and the switch being arranged in one of a serial configuration and a parallel configuration, wherein:
the serial configuration includes the switch connected serially with the at least one serial string, the switch configured to open in response to the monitoring mechanism detecting the at least one electrical parameter of the load being out of the predetermined specification, and
the parallel configuration includes the switch connected in parallel with the at least one serial string, the switch configured to close in response to the monitoring mechanism detecting the at least one electrical parameter of the load being out of the predetermined specification; and
at least one controller configured to sense the change in the current flowing through the at least one serial string and, in response to the change in current, shut down the plurality of DC power converters.
5. A system comprising:
a plurality of DC power converters providing a DC output;
an inverter having an inverter input coupled to the DC output and an inverter output, wherein the inverter is configured to convert input power received on the inverter input from the plurality of DC power converters on the DC output and provide output power on the inverter output; and
a switch disposed between the plurality of DC power converters and the inverter, wherein the inverter is configured to provide a signal to the switch indicating whether a parameter at the inverter output is in or out of a predetermined specification, wherein the switch is configured to activate in response to the signal indicating that the parameter is out of the predetermined specification, and wherein the switch, when activated, causes a change in current flowing through the DC output; and
at least one controller configured to sense the change in the current flowing through the DC output, and in response to the change in current, shut down the plurality of DC power converters.
6. The system of claim 5 , wherein the plurality of DC power converters are coupled in at least one serial string.
7. The system of claim 5 , wherein the parameter being out of the predetermined specification indicates an islanding condition in a load coupled to the inverter output.
8. A method comprising:
monitoring operation of an inverter having an input coupled to a plurality of direct current (DC) power converters coupled in at least one serial string, the inverter having an output coupled to a load, and the inverter converting input power received from the plurality of DC power converters and providing output power to the load;
monitoring at least one electrical parameter of the load;
stopping production of the output power when the at least one electrical parameter is out of a predetermined specification;
activating a switch disposed between the plurality of DC power converters and the inverter when production of the output power is stopped;
sensing a change in current flowing through the serial string in response to the activating of the switch; and
shutting down the plurality of DC power converters in response to sensing the change in current flowing through the serial string.
9. An apparatus comprising:
a serially connected string of a plurality of direct current (DC) converters having a DC output, each DC converter configured to sense current through the serially connected string;
an inverter coupled to the DC output of the serially connected string and adapted to convert input power received on the DC output to provide output power to a load;
a switch disposed between the DC output of the serially connected string and the inverter and arranged in one of a serial configuration and a parallel configuration; and
control circuitry configured to open and close the switch;
wherein, in the serial configuration, the switch is connected serially with the serially connected string, the control circuitry is configured to open the switch in response to an electrical parameter of the load being out of a predetermined specification, and each DC converter is configured to stop providing the input power in response to the sensed current through the serially connected string being less than a previously specified minimal threshold current; and
wherein in the parallel configuration, the switch is connected in parallel with the serially connected string, the control circuitry is configured to close the switch in response to the electrical parameter of the load being out of the predetermined specification, and each DC converter is configured to stop providing the input power in response to the sensed current through the serially connected string being greater than a previously specified maximal threshold current.
10. The apparatus of claim 9 , wherein the control circuitry is configured to cause the inverter to stop production of the output power in response to the electrical parameter being out of the predetermined specification.
11. An apparatus comprising:
a plurality of direct current (DC) power converters providing a DC output;
an inverter coupled to the plurality of DC power converters and adapted to convert input power received on the DC output from the plurality of DC power converters to provide output power to a load;
a switch disposed between the plurality of DC power converters and the inverter and adapted to, when activated, cause a change in a current flowing through the input of the inverter; and,
at least one control circuit configured to activate the switch in response to an electrical parameter of the load being out of a predetermined specification, and in response to the change in current, shut down the plurality of DC power converters.
12. The apparatus of claim 11 , wherein the inverter is configured to stop production of the output power in response to the electrical parameter being out of the predetermined specification.
13. The apparatus of claim 11 , wherein the electrical parameter being out of the predetermined specification indicates an islanding condition in the load.
14. A method comprising:
monitoring operation of an inverter having an input coupled to a plurality of direct current (DC) power converters and having an output coupled to a load, the inverter converting input power received from the plurality of DC power converters and providing output power to the load;
activating a switch disposed between the plurality of DC power converters and the inverter in response to an electrical parameter of the load being out of a predetermined specification;
sensing a change in the current flowing through the input of the inverter; and
shutting down the plurality of DC power converters in response to the change in current.
15. The method of claim 14 , further comprising:
stopping production of the output power in response to the electrical parameter being out of the predetermined specification.
16. The method of claim 14 , wherein the electrical parameter being out of the predetermined specification indicates an islanding condition in the load.