BALANCING CURRENT WITHIN A PARALLEL MODULAR CONVERTER SYSTEM

• US 20180026557A1
• Filed: 07/25/2016
• Published: 01/25/2018
• Est. Priority Date: 07/25/2016
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: PASCHEDAG, Darren Lee, GAO, Lijun, LIU, Shengyi
• Granted Patent: US 10,454,393 B2
• Time in Patent Office: Days
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 1/0025 Arrangements for modifying reference values, feedback values or error values in the control loop of a converter
• CPC Class Codes: H02M 1/088 for the simultaneous control of series or parallel connected semiconductor devices
• CPC Class Codes: H02M 1/44 Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
• CPC Class Codes: H02M 7/493 the static converters being arranged for operation in parallel
• CPC Class Codes: H02M 7/537 using semiconductor devices only, e.g. single switched pulse inverters
• CPC Class Codes: H02P 27/08 with pulse width modulation
• CPC Class Codes: H02P 5/505 using equalising lines, e.g. rotor and stator lines of first and second motors

Abstract

A current balancing system, and associated method and computer-readable medium are disclosed herein. The current balancing system comprises a plurality of power inverters, each power inverter included within a respective current loop and configured to generate a corresponding current amount. The current balancing system further comprises a plurality of inverter controllers, each inverter controller associated with a respective one of the plurality of power inverters and configured to receive a reference frame-transformed amount of the corresponding current amount. Each inverter controller is capable of independently controlling the corresponding current amount provided to a load.

Claims

1. A current balancing system (100, 400) comprising:

a plurality of power inverters (125₁, 125₂, . . . , 125_n), each power inverter (125_k) included within a respective current loop (422(k)) and configured to generate a corresponding current amount (I_abc(k)); and

a plurality of inverter controllers (325(1), 325(2), . . . , 325(n)), each inverter controller (325(k)) associated with a respective one of the plurality of power inverters and configured to receive a reference frame-transformed amount (I_d (k), I_q (k)) of the corresponding current amount, whereby each inverter controller is capable of independently controlling the corresponding current amount provided to a load (140).

2. The system of claim 1, wherein at least a first power inverter of the plurality of power inverters has different electrical characteristics than at least a second power inverter of the plurality of power inverters, wherein a same commanded current amount (I_{q_command}) provided to the first power inverter and to the second power inverter results in an uneven current processing among the plurality of power inverters.

3. The system of claim 1, wherein independently controlling the corresponding current amount provided to a load operates to mitigate one or more of:

a current imbalance within the plurality of power inverters;

power losses of the plurality of power inverters;

a circulation current between at least two of the plurality of power inverters; and

electrical noise generated by the plurality of power inverters.

4. The system of claim 1, wherein at least two of the plurality of power inverters provide power to a common load (505).

5. The system of claim 4, wherein the common load comprises a motor (M₁, M₂, . . . M_j).

6. The system of claim 1, wherein the plurality of inverter controllers are included in a system controller (105), wherein the system controller further comprises a global controller stage (305) configured to:

determine (605) a total system current amount (I_{q_system}) for achieving a commanded motor rotational speed (235); and

generate (610) current commands (I_{q_command}) to distribute the total system current amount evenly (I_{q_system} n) among the plurality of power inverters.

7. The system of claim 6, wherein the global controller stage further comprises a circulation current module (215) configured to:

compare (620), responsive to generating the current commands, the current amounts corresponding to each of the plurality of power inverters; and

determine (625), based on the comparison, a circulation current (I_circulation(1), I_circulation(2), . . . , I_circulation(n)) existing between at least two of the plurality of power inverters,

wherein the plurality of inverter controllers are further configured to adjust the corresponding current amount provided to the load based on the determined circulation current.

8. A method (600) of controlling current production of a plurality of power inverters (125₁, 125₂, . . . , 125_n) controlled by a plurality of inverter controllers (325(1), 325(2), . . . , 325(n)), the method comprising:

determining (615) a plurality of current amounts (I_abc(1), I_abc(2), . . . , I_abc(n)), each of the plurality of current amounts produced by a respective one of the plurality of power inverters;

transforming (630) a reference frame of each of the plurality of current amounts to produce a plurality of transformed current amounts (I_dq(1), I_dq(2), . . . , I_dq(n)); and

generating (635), based on the plurality of transformed current amounts received by the plurality of inverter controllers, gate commands (330(1), 330(2), . . . , 330(n)) for the plurality of power inverters,

wherein application of the generated gate commands operates to adjust at least one of the plurality of current amounts to thereby mitigate a current imbalance between at least two of the plurality of power inverters.

9. The method of claim 8, wherein the application of the generated gate commands further operates to mitigate one or more of:

power losses of the plurality of power inverters;

a circulation current between at least two of the plurality of power inverters; and

electrical noise generated by the plurality of power inverters.

10. The method of claim 8, wherein at least a first power inverter of the plurality of power inverters has different electrical characteristics than at least a second power inverter of the plurality of power inverters, wherein a same commanded current amount (I_{q_command}) provided to the first power inverter and to the second power inverter results in an uneven current processing among the plurality of power inverters.

11. The method of claim 8, further comprising:

determining (605) a total system current amount (I_{q_system}) for achieving a commanded motor rotational speed (235); and

generating (610) initial current commands (I_{q_command}) to distribute the total system current amount evenly (I_{q_system}/n) among the plurality of power inverters using a plurality of initial gate commands,

wherein determining the plurality of current amounts is performed responsive to application of the initial gate commands.

12. The method of claim 11, further comprising:

comparing (620), responsive to application of the initial gate commands, the corresponding current amount produced by each of the plurality of power inverters; and

determining (625) that the current imbalance exists based on the comparison.

13. The method of claim 8, further comprising:

providing (640), using the generated gate commands received by the plurality of power inverters, power from the plurality of power inverters to a common load (505).

14. The method of claim 13, wherein the common load comprises a motor (M₁, M₂, . . . , M_j).

15. A non-transitory computer-readable medium comprising computer program code that, when executed by operation of one or more computer processors, performs an operation (600) of controlling current production of a plurality of power inverters (125₁, 125₂, . . . , 125_n) controlled by a plurality of inverter controllers (325(1), 325(2), . . . , 325(n)), the operation comprising:

determining (615) a plurality of current amounts (I_abc(1), I_abc(2), . . . , I_abc(n)), each of the plurality of current amounts produced by a respective one of the plurality of power inverters;

transforming (630) a reference frame of each of the plurality of current amounts to produce a plurality of transformed current amounts (I_dq(1), I_dq(2), . . . , I_dq(n)); and

generating (635), based on the plurality of transformed current amounts received by the plurality of inverter controllers, gate commands (330(1), 330(2), . . . , 330(n)) for the plurality of power inverters,

wherein application of the generated gate commands operates adjust at least one of the plurality of current amounts to thereby mitigate a current imbalance between at least two of the plurality of inverters.

16. The computer-readable medium of claim 15, wherein the application of the generated gate commands further operate to mitigate one or more of:

power losses of the plurality of power inverters;

a circulation current between at least two of the plurality of power inverters; and

electrical noise generated by the plurality of power inverters.

17. The computer-readable medium of claim 15, the operation further comprising:

determining (605) a total system current amount (I_{q_system}) for achieving a commanded motor rotational speed (235); and

generating (610) initial current commands (I_{q_command}) to distribute the total system current amount evenly (I_{q_system}/n) among the plurality of power inverters using a plurality of initial gate commands,

wherein determining the plurality of current amounts is performed responsive to application of the initial gate commands.

18. The computer-readable medium of claim 17, the operation further comprising:

comparing (620), responsive to application of the initial gate commands, the corresponding current output produced by each of the plurality of power inverters; and

determining (625) that the current imbalance exists based on the comparison.

19. The computer-readable medium of claim 15, the operation further comprising:

providing (640), using the generated gate commands received by the plurality of power inverters, power from the plurality of power inverters to a common load (505).

20. The computer-readable medium of claim 19, wherein the common load comprises a motor (M₁, M₂, . . . , M_j).