Input-parallel/output-parallel inverter assembly control device and method

• US 9,362,815 B2
• Filed: 10/24/2011
• Issued: 06/07/2016
• Est. Priority Date: 10/25/2010
• Status: Active Grant

• Current Assignee: Bloom Energy Corporation
• Original Assignee: Bloom Energy Corporation
• Inventors: Anand, Aisur Gopalakrishnan Vishal, Gurunathan, Ranganathan, Ballantine, Ame, Narayanasamy, Saravanakumar, Rao, Kodali Venkata Narasimha
• Primary Examiner(s): Ruddock, Ula C
• Assistant Examiner(s): CHUO, TONY SHENG HSIANG
• Application Number:
  US13/279,921
• Publication Number:
  US 20120098336A1
• Time in Patent Office: 1,688 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: H02J 1/102 being switching converters H02J1/108, H02J1/12 take precedence
• CPC Class Codes: H02J 2300/30 The power source being a fuel cell
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 3/46 Controlling of the sharing of output between the generators, converters, or transformers
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/10 Arrangements incorporating converting means for enabling loads to be operated at will from different kinds of power supplies, e.g. from ac or dc
• CPC Class Codes: H02M 3/1584 with a plurality of power processing stages connected in parallel
• CPC Class Codes: H02M 7/493 the static converters being arranged for operation in parallel
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A method includes controlling multiple networked input-parallel/output-parallel inverters of a fuel cell system as a single inverter assembly by a master controller. A fuel cell system includes a plurality of fuel cell segments, a plurality of DC/DC converters and at least one DC/AC inverter, where an output of each of the plurality of the fuel cell segments is connected to a pair of DC/DC converters, and each of the pair DC/DC converters is connected to an opposite polarity bus being provided to the inverter.

Claims

1. A method, comprising controlling multiple networked input-parallel/output-parallel inverters of a fuel cell system as a single inverter assembly by a master controller, wherein all of the inverters in the assembly receive the same split bus direct current (DC) input from a plurality of fuel cell stack segments as parallel inputs, and output a common three phase alternating current (AC) parallel output to a load, wherein the master controller:

senses a condition of the split bus DC input and controls a power set point and an on/off state of each individual inverter in the assembly to avoid a power collapse of the split bus DC input, and

controls the power set point of each individual inverter in the assembly such that the power set point of a first inverter in the assembly is different from the power set point of a second inverter in the assembly.

2. The method of claim 1, wherein the master controller independently controls the power set point and the on/off state of each individual inverter in the assembly.

3. The method of claim 1, wherein the master controller independently controls the power set point of the first and the second inverter.

4. The method of claim 1, wherein the first inverter in the assembly is on while a second inverter in the assembly is off.

5. The method of claim 4, wherein the master controller independently controls the on/off state of the first and the second inverter.

6. The method of claim 1, wherein the fuel cell system output is connected to a building load, and a building management system uses the master controller to turn off a fraction of the inverters in the assembly to the building load.

7. The method of claim 1, wherein the master controller controls a power set point of each individual inverter in the assembly such that the power set point of each individual inverter is set to provide a power output for a load in response to at least one of the individual inverters not contributing to the power output.

8. The method of claim 1, wherein the master controller receives input signals indicating a state of health for each individual inverter in the assembly.

9. The method of claim 8, wherein the master controller detects a failure of an individual inverter in the assembly and controls the power set point of each remaining individual inverter in the assembly.

10. The method of claim 1, wherein the master controller evaluates a power output of the inverters in the assembly and the controller controls an on/off state of each individual inverter in the assembly to improve efficiency by signaling at least one of the inverters of the assembly to switch to an off state in response to a load being less than the maximum load of the inverters in the assembly.

11. The method of claim 1, wherein the master controller provides to the inverters in the assembly a power set point command, an on/off state command, and a power factor command.

12. A method, comprising controlling multiple networked input-parallel/output-parallel inverters of a fuel cell system as a single inverter assembly by a master controller, wherein the master controller:

controls a power set point of each individual inverter in the assembly such that the power set point of a first inverter in the assembly is different from the power set point of a second inverter in the assembly,

controls an on/off state of each individual inverter in the assembly,

receives input signals indicating a state of health for each individual inverter in the assembly,

detects a failure of an individual inverter in the assembly and controls the power set point of each remaining individual inverter in the assembly, and

increases the power set point of each remaining individual inverter in the assembly in response to determining that a load set point divided by a number of remaining individual inverters is less than a capability of each remaining individual inverter in the assembly or decreases the power set point of each remaining individual inverter in the assembly in response to determining that a load set point divided by a number of remaining individual inverters is equal to a capability of each remaining individual inverter in the assembly.

13. The method of claim 12, wherein the master controller increases the power set point of each remaining individual inverter in the assembly in response to determining that a load set point divided by a number of remaining individual inverters is less than a capability of each remaining individual inverter in the assembly and decreases the power set point of each remaining individual inverter in the assembly in response to determining that a load set point divided by a number of remaining individual inverters is equal to a capability of each remaining individual inverter in the assembly.

14. The method of claim 12, wherein the master controller signals at least one of the inverters of the assembly to switch to an on state in response to detecting a failure of a different individual inverter in the assembly.

15. The method of claim 12, wherein the master controller restores the power set points of each of the individual inverters in the assembly in response to receiving an input signal indicating a healthy and ready state of an individual inverter at a location of a previously detected failed individual inverter in the assembly.

16. The method of claim 12, wherein the master controller increases the power set point of each remaining individual inverter in the assembly in response to determining that the load set point divided by the number of remaining individual inverters is less than the capability of each remaining individual inverter in the assembly.

17. The method of claim 12, wherein the master controller decreases the power set point of each remaining individual inverter in the assembly in response to determining that the load set point divided by the number of remaining individual inverters is equal to the capability of each remaining individual inverter in the assembly.

18. A method, comprising controlling multiple networked input-parallel/output-parallel inverters of a fuel cell system as a single inverter assembly by a master controller, wherein the master controller:

controls a power set point of each individual inverter in the assembly such that the power set point of a first inverter in the assembly is different from the power set point of a second inverter in the assembly, and

provides a power output setting command for the inverters in the assembly as the smaller of a power command from a fuel cell system controller that regulates the fuel cell system and a power which can be maintained without collapse of a split bus direct current (DC) input to the inverters in the assembly, and

controls the power set point of each of the individual inverter in the assembly to provide the power output.

19. A method, comprising controlling multiple networked input-parallel/output-parallel inverters of a fuel cell system as a single inverter assembly by a master controller, wherein the master controller:

controls a power set point of each individual inverter in the assembly such that the power set point of a first inverter in the assembly is different from the power set point of a second inverter in the assembly,

monitors a power output of the inverters in the assembly,

compares the power output to a generated sine wave reference,

calculates a current command value to minimize an error between an output voltage of the power output and a reference voltage of the generated sine wave reference, and

provides a current command with the current command value to the inverters in the assembly.