Microgrid inverter controller and inverter fault current control method

Patent metadata

Field	Value
Publication number	US-12068699-B2
Application number	US-202318501494-A
Country	US
Kind code	B2
Filing date	Nov 3, 2023
Priority date	Nov 3, 2022
Publication date	Aug 20, 2024
Grant date	Aug 20, 2024

Abstract

A method includes outputting an alternating current (AC) waveform from an inverter module to a plurality of loads, outputting a fault waveform from the inverter module to a first load of the plurality of loads in response to a fault condition associated with the first load, and outputting the AC waveform from the inverter module to at least some of the plurality of loads if the fault condition is cleared before a recovery period expires or disconnecting the inverter module from the plurality of loads if the fault condition is not cleared before the recovery period expires.

First claim

What is claimed is:

1. A method, comprising:
outputting an alternating current (AC) waveform from an inverter module to a plurality of loads;
outputting a fault waveform from the inverter module to a first load of the plurality of loads in response to a fault condition associated with the first load; and
performing one of:
outputting the AC waveform from the inverter module to at least some of the plurality of loads if the fault condition is cleared before a recovery period expires, and
disconnecting the inverter module from the plurality of loads if the fault condition is not cleared before the recovery period expires.

2. The method of claim 1 , wherein outputting the fault waveform comprises:
outputting a first trip current at a first current level for a first time period;
outputting a second trip current at a second current level that is less than the first current level, for a second time period that is greater than the first time period; and
repeating the steps of outputting the first and the second trip current until the recovery period expires or the fault condition is cleared.

3. The method of claim 2 , wherein:
the first time period ranges from one half of a current cycle to one current cycle; and
the first current level is 20% to 30% greater than the second current level.

4. The method of claim 2 , further comprising:
determining if the recovery period expired by counting a number of times the first current level is reached; and
resetting the recovery period if the first current level is not reached during consecutive cycles of the fault waveform.

5. The method of claim 1 , wherein the recovery period ranges from 1 second to 5 seconds.

6. The method of claim 1 , wherein the fault condition comprises a short circuit associated with the first load.

7. The method of claim 6 , wherein:
the step of outputting the fault waveform comprises outputting a trip current to a first overcurrent protection device (OCPD) associated with the first load; and
the fault condition is cleared before the recovery period expires when the trip current trips the first OCPD to electrically disconnect the first load from the inverter module.

8. The method of claim 7 , wherein the step of outputting the AC waveform from the inverter module to at least some of the plurality of loads comprises outputting the AC waveform from the inverter module to a second load of the plurality of loads after the first load is electrically disconnected from the inverter module.

9. The method of claim 7 , wherein the first OCPD comprises a circuit breaker and a relay that are electrically connected between the inverter module and the first load.

10. The method of claim 7 , wherein the first OCPD comprises a fuse that is electrically connected between the inverter module and the first load.

11. The method of claim 1 , wherein the fault condition comprises a current inrush.

12. The method of claim 11 , wherein the step of outputting the AC waveform from the inverter module to at least some of the plurality of loads comprises outputting the AC waveform from the inverter module to the first load and to a second load of the plurality of loads after a magnitude of the current inrush drops below a magnitude of the fault waveform.

13. The method of claim 1 , wherein the inverter module receives a direct current (DC) from a fuel cell system and outputs the AC waveform to the plurality of loads.

14. The method of claim 1 , further comprising:
activating an energy reduction maintenance setting (ERMS) mode in response to receiving an ERMS signal; and
disconnecting the inverter module from the plurality of loads when the fault condition is detected while the ERMS mode is activated,
wherein the disconnecting the inverter module from the plurality of loads comprises disconnecting the inverter module within one half of a current cycle of detecting the fault condition, and
wherein the ERMS signal is generated in response to opening a door or access panel of the inverter module.

15. The method of claim 1 , further comprising:
monitoring a magnitude of the AC waveform output from the inverter module to the plurality of the loads; and
detecting the fault condition based on the monitoring the magnitude of the AC waveform.

16. A system, comprising:
an inverter module;
a plurality of overcurrent protection devices (OCPD) electrically connected to the inverter module and configured to be connected to a respective load of a plurality of loads, wherein a first OCPD of the plurality of OCPDs is configured to be electrically connected to a first load of the plurality of loads; and
a controller configured to control the inverter module to:
output an alternating current (AC) waveform from the inverter module to the plurality of loads;
output a fault waveform from the inverter module to the first OCPD in response to a fault condition associated with the first load; and
output the AC waveform from the inverter module to at least some of the plurality of loads if the fault condition is cleared before a recovery period expires or disconnect the inverter module from the plurality of loads if the fault condition is not cleared before the recovery period expires.

17. The system of claim 16 , wherein:
an input of the inverter module is configured to be electrically connected to a fuel cell system;
the plurality of overcurrent protection devices (OCPD) comprise circuit breakers or fuses;
the controller is configured to control the inverter module to output the fault waveform which comprises a trip current to the first OCPD; and
the controller is configured to control the inverter module to clear the fault condition before the recovery period expires when the trip current trips the first OCPD to electrically disconnect the first load from the inverter module.

18. The system of claim 16 , wherein:
the inverter module comprises a switch configured to be actuated by opening an access panel or door of the inverter module; and
the controller is configured to activate an energy reduction maintenance setting (ERMS) mode in response to a signal from the switch indicating the opening of the access panel or door of the inverter module; and
the controller is configured to disconnect the inverter module from the plurality of loads within one half of a current cycle of detecting the fault condition while the ERMS mode is activated.

19. A method performed by a controller, comprising:
detecting whether a fault has occurred in an electrical circuit connected to an inverter;
generating a first signal to set a current limit level of the inverter to a first predefined level for a first predefined period, the current limit level indicating a maximum amount of current supplied by the inverter under fault conditions;
generating a second signal to set the current limit level of the inverter to a second predefined level for a second predefined period, the second predefined level being less than the first predefined level; and
transmitting the first signal and the second signal to the inverter.

20. The method as claimed in claim 19 , further comprising:
determining a count of consecutive instances when a current level of the inverter reaches the first predefined level; and
transmitting a trip signal to inverter if the count of the consecutive instances for the current level of the inverter exceeds a predetermined value, the trip signal facilitating tripping of the inverter from the electrical circuit.

Assignees

• Bloom Energy Corp

Inventors

• Pmsvvsv Prasad
• Biligiri Kaushal
• Baker Beau
• Ebad Mehdi
• Bommireddy Vignan Reddy
• Hurt Andrew

Classifications

• H02M7/537

  using semiconductor devices only, e.g. single switched pulse inverters · CPC title

• H02M1/088

  for the simultaneous control of series or parallel connected semiconductor devices · CPC title

• H02H1/0015

  Using arc detectors · CPC title

• H02M7/44

  by static converters · CPC title

• H02M1/325

  with means for allowing continuous operation despite a fault, i.e. fault tolerant converters · CPC title