Selective grounding of grid parallel inverter systems

Patent metadata

Field	Value
Publication number	US-11271406-B2
Application number	US-201916250153-A
Country	US
Kind code	B2
Filing date	Jan 17, 2019
Priority date	Jan 24, 2018
Publication date	Mar 8, 2022
Grant date	Mar 8, 2022

Abstract

A method of operating a power generator having a first electrical output electrically connected to a utility grid and a second electrical output electrically connected to a load includes detecting if the first electrical output of the power generator is electrically disconnected from the utility grid, and electrically connecting at least a neutral line of the first electrical output to ground in response to detecting that the first output is electrically disconnected from the utility grid.

First claim

What is claimed is:

1. A power generation system, comprising: a power generator having a first electrical output configured to be electrically connected to a utility grid transformer and a second electrical output configured to be electrically connected to a load; at least one first switch located at least on a neutral line of the power generator and configured to disconnect the neutral line from the utility grid transformer; a ground line electrically connecting the power generator to a local ground; and at least one ground line switch located on the ground line and configured to connect the neutral line to the local ground via the ground line in response to the at least one first switch disconnecting the neutral line from the utility grid transformer.

2. The system of claim 1 , wherein: the power generator comprises a fuel cell power generator comprising a plurality of fuel cell modules, a plurality of input output modules containing a respective DC/AC inverter, and an electrical distribution module; a first electrical output of the of each of the plurality of the fuel cell modules is electrically connected to a respective one of the plurality of input output modules; the plurality of input output modules are electrically connected to the electrical distribution module; and the electrical distribution module is configured to be electrically connected to the utility grid transformer via a circuit breaker.

3. The system of claim 2 , wherein: neutral lines of the plurality of fuel cell modules are electrically connected to each other in the electrical distribution module to form the neutral line of the power generator; the first electrical output of the power generator is configured to be automatically electrically disconnected by the circuit breaker from the utility grid transformer when the grid experiences a power spike or an outage; at least one first switch comprises a switch located in the electrical distribution module or a plurality of switches located in the respective input output modules; and the at least one first switch is configured to be switched to electrically disconnect at least the neutral line from the circuit breaker and to electrically connect at least the neutral line to the ground via the ground line in response to detecting that at least one of the electrical distribution module or the plurality of input output modules are electrically disconnected from the utility grid transformer by the circuit breaker.

4. The system of claim 3 , wherein the ground line switch is configured to close from a normally open position to electrically connect at least the neutral line to the ground via the ground line in response to detecting that the at least one first switch is switched to electrically disconnect at least the neutral line from the circuit breaker.

5. The system of claim 4 , wherein: the at least one first switch comprises a relay containing a primary contactor, an auxiliary contactor and a detector; and detecting that the at least one first switch is switched to electrically disconnect at least the neutral line from the circuit breaker comprises detecting a current or voltage through the auxiliary contactor using the detector.

6. The system of claim 4 , wherein: the at least one first switch comprises a relay; and the system is configured to detect that the at least one first switch is switched to electrically disconnect at least the neutral line from the circuit breaker by sending an electrical test signal between the electrical distribution module and the plurality of input output modules and detecting that the at least one first switch is switched when the electrical test signal is disrupted.

7. The system of claim 4 , wherein: the at least one first switch comprises a relay; and the system is configured to detect that the at least one first switch is switched to electrically disconnect at least the neutral line from the circuit breaker by measuring a change in resistance between the ground line and a point in the neutral line located between the circuit breaker and the at least one switch.

8. The system of claim 4 , wherein the first electrical output of the power generator is connected by the at least one switch to the ground through at least one of a resistor or an inductor.

9. The system of claim 4 , wherein a second electrical output of the fuel cell module is configured to be electrically connected to the load via an uninterruptible power module containing a second DC/AC inverter or via an auxiliary output module containing a DC/DC converter and a DC output.

10. The system of claim 1 , wherein the first electrical output of the power generator comprises a four line power bus which is configured to provide a three phase alternating electric current on three of the lines and the fourth line comprises the neutral line.

11. The system of claim 1 , wherein: the power generator comprises a fuel cell power generator comprising a first fuel cell module, at least one input output module containing a DC/AC inverter, an electrical distribution module, and a plurality of uninterruptable power modules; each of the plurality of uninterruptable power modules are operably connected to the first fuel cell module; the load comprises a first load and a second load; and the first load and the second load are operably connected to a respective one of the plurality of uninterruptable power modules.

Assignees

• Bloom Energy Corp

Inventors

• Pmsvvsv Prasad
• Cottuli Carl
• Baker Beau

Classifications

• H02J2101/30

  Fuel cells · CPC title

• H02J2101/28

  Wind energy · CPC title

• H02J2101/24

  Photovoltaics · CPC title

• H02J2101/22

  Solar energy · CPC title

• Y02B90/10

  Applications of fuel cells in buildings · CPC title