Control system for uninterruptible power supplies

• US 9,160,202 B2
• Filed: 01/31/2012
• Issued: 10/13/2015
• Est. Priority Date: 01/31/2012
• Status: Active Grant

• Current Assignee: ABB Schweiz AG (ABB Limited)
• Original Assignee: General Electric Company
• Inventors: Colombi, Silvio, Giuntini, Lorenzo, Delmu, Andrea Lauro
• Primary Examiner(s): Barnie, Rexford
• Assistant Examiner(s): PARRIES, DRU M
• Application Number:
  US13/363,178
• Publication Number:
  US 20130193760A1
• Time in Patent Office: 1,351 Days
• Field of Search: 307/64
• US Class Current: 1/1
• CPC Class Codes: H02J 3/0073 for providing alternative feeding paths between load and source when the main path fails, e.g. transformers, busbars
• CPC Class Codes: H02J 9/061 for DC powered loads
• CPC Class Codes: H02J 9/062 for AC powered loads

Abstract

Systems and methods for controlling uninterruptible power supplies (UPSs) are provided. In one example, a system may include an inverter feed path to supply a first amount of power to a load and a bypass feed path to supply a second amount of power to the load. A controller may generate command the inverter feed path and the bypass feed path to vary the first amount of power and the second amount of power based at least in part on an occurrence of a power supply disturbance and a type or severity, or both, of the power supply disturbance.

Claims

1. An uninterruptible power supply system comprising:

a first inverter feed path comprising a rectifier in series with an inverter to supply a first amount of power to a load based at least in part on a first plurality of commands;

a first bypass feed path in parallel with the inverter feed path to supply a second amount of power to the load based at least in part on a second plurality of commands; and

a controller configured to identify an occurrence and type of a power supply disturbance and to generate the first and second pluralities of commands to vary the first amount of power and the second amount of power based at least in part on an occurrence of an identified power supply disturbance and an identified type of the identified power supply disturbance, wherein the identified power supply disturbance comprises an output current, wherein the controller is configured to;

when the output current of the uninterruptible power supply system exceeds a limit, allow the first bypass feed path to supply power to the load;

increment a first counter while the output current of the uninterruptible power supply system exceeds the limit;

decrement the first counter while the output current does not exceed the limit; and

when the first counter has been decremented to a particular value or less, allow the first bypass feed path or the first inverter feed path, or both, to supply power to the load.

2. The system of claim 1, wherein the first inverter feed path comprises an output transformer in series with the rectifier and inverter, wherein the controller is configured to control the first bypass feed path or the first inverter feed path, or both, such that when the first inverter feed path substantially does not supply power to the load, the output transformer is magnetized by power back-fed from the first bypass feed path into the first inverter feed path.

3. The system of claim 1, wherein the controller is configured to detect the occurrence of one or more power supply disturbances of a set of identifiable types of power supply disturbances, wherein the set of identifiable types of power supply disturbances comprises an instantaneous voltage error, an RMS voltage error, an output short circuit, a failure of a static switch module of the first bypass feed path, a missing input phase, and a neutral current.

4. The system of claim 1, wherein the controller is configured to generate the first and second pluralities of commands such that, following the occurrence of the power supply disturbance, the first amount of power increases and the second amount of power decreases at corresponding rates that depend on a severity of the power supply disturbance.

5. The system of claim 1, wherein the controller is configured to generate the first and second pluralities of commands such that, following the occurrence of the power supply disturbance, the first amount of power increases and the second amount of power decreases at corresponding rates that depend on the type of the power supply disturbance.

6. The system of claim 1, wherein the controller is configured to generate the first and second pluralities of commands such that, following the occurrence of the power supply disturbance, the second amount of power is reduced to substantially zero and the first amount of power is temporarily increased to an amount sufficient to cause a static switch module of the bypass feed path to be forced off with back-fed power through the bypass feed path.

7. The system of claim 1, wherein the controller is configured to generate the first and second pluralities of commands such that, following the occurrence of the power supply disturbance, the first amount of power increases to softly remagnetize an output transformer of the first inverter feed path.

8. The system of claim 1, wherein the controller is configured to generate the first and second pluralities of commands, following the occurrence of the power supply disturbance, at least in part by decreasing control gains associated with the control of the first inverter feed path component to nominal values over a period time to reduce transient stiffness in the inverter feed path.

9. An uninterruptible power supply system comprising:

a first inverter feed path comprising a rectifier in series with an inverter to supply a first amount of power to a load based at least in part on a first plurality of commands;

a first bypass feed path in parallel with the inverter feed path to supply a second amount of power to the load based at least in part on a second plurality of commands, wherein the first bypass feed path comprises an inductor in series with a static switch module and wherein the controller is configured to identify the occurrence of the power supply disturbance based at least in part on current sensor and voltage sensor measurements on the first bypass feed path that are obtained before the inductor; and

a controller configured to generate the first and second pluralities of commands to vary the first amount of power and the second amount of power based at least in part on an occurrence of a power supply disturbance and a type or severity, or both, of the power supply disturbance.

10. An article of manufacture comprising:

one or more tangible, non-transitory machine-readable media at least collectively comprising machine-executable instructions, the instructions comprising;

instructions to run a disturbance analyzer component of an uninterruptible power supply control system to identify at least two types of power supply disturbances and to determine when at least one of the at least two identified types of identified power supply disturbances occurs in the uninterruptible power supply, wherein the instructions to run the disturbance analyzer comprise instructions to run an instantaneous voltage error detection component, wherein the instructions to run an instantaneous voltage error detection component comprise instructions to;

compare a measured instantaneous output voltage of the uninterruptible power supply with an expected instantaneous output voltage;

when the measured voltage differs from the expected voltage by more than a first threshold but less than a second threshold, increment a counter by a first added value;

when the measured voltage differs from the expected voltage by more than the second threshold, increment the counter by a second added value, wherein the second added value is greater than the first added value;

when the measured voltage differs from the expected voltage by less than the first threshold, decrement the counter by a subtracted value; and

when the counter holds a value that exceeds a counter threshold, determine that an instantaneous voltage error has occurred;

instructions to cause one or more bypass feed paths or one or more inverter feed paths to primarily supply power through the uninterruptible power supply depending on whether the at least one of the at least two identified types of identified power supply disturbances has occurred in the uninterruptible power supply; and

instructions to run a transient control component of the uninterruptible power supply control system to control a transient modality by which a transition from supplying power from the one or more bypass feed paths to the one or more inverter feed paths or from the one or more bypass feed paths to the one or more inverter feed paths occurs when such a transition occurs.

11. The article of manufacture of claim 10, wherein the instructions to run the disturbance analyzer comprise instructions to run an instantaneous voltage error detection component configured to determine whether an instantaneous voltage error has occurred and, when the instantaneous voltage error has occurred, a severity of the instantaneous voltage error.

12. The article of manufacture of claim 10, wherein the instructions to run the instantaneous voltage error detection component comprise instructions, when the counter holds the value that exceeds a counter threshold, to determine a severity of the instantaneous voltage error based at least in part on the value held by the counter, wherein the instructions to run the transient control component comprise instructions to vary the transient modality based at least in part on the severity of the instantaneous voltage error.

13. The article of manufacture of claim 10, wherein the instructions to run the disturbance analyzer comprise instructions to run:

a root mean squared voltage error detector component that compares a root mean squared value of an output voltage of the uninterruptible power supply to upper and lower root mean squared limits;

a static switch module failure detector that compares a direct current value of current through the one or more bypass feed paths with a bypass direct current limit;

a missing input phase detector that compares a root mean squared value of the current through the one or more bypass feed paths with upper and lower bypass root mean squared current limits;

or

a neutral current detector that compares a sum of all phases of the current through the one or more bypass feed paths with an upper limit;

or

any combination thereof.

14. The article of manufacture of claim 10, wherein the instructions to run the disturbance analyzer component comprise instructions to run a short circuit detection component, wherein the instructions to run the short circuit detection component comprise instructions to:

when an output current of the uninterruptible power supply exceeds a limit, allow only the bypass feed paths to supply power to the load;

increment a first counter while the output current of the uninterruptible power supply exceeds the limit;

decrement the first counter while the output current does not exceed the limit;

once the first counter crosses a first threshold;

increment a second counter while the output current does not exceed the limit; and

decrement the second counter while the output current exceeds the limit; and

when the second counter crosses a second threshold, allow the bypass feed paths or the inverter feed paths, or both, to supply power to the load after re-magnetizing output transformers of the inverter feed paths.

15. The article of manufacture of claim 10, wherein the instructions to run the transient control component comprise instructions to steadily reduce power supplied by the bypass feed path while steadily increasing power supplied by the inverter feed path.

16. A method comprising:

supplying power to a load through a bypass feed path of an uninterruptible power supply;

identifying a first type of power supply disturbance and a second type of power supply disturbance possibly occurring in the uninterruptible power supply;

ascertaining that the first identified type of power supply disturbance or that the second identified type of power supply disturbance is occurring in the uninterruptible power supply;

transitioning to supplying power to the load through an inverter feed path of the uninterruptible power supply rather than the bypass feed path according to a first transient modality when the first identified type of power supply disturbance is occurring and according to a second transient modality when the second identified type of power supply disturbance is occurring;

when an output current of the uninterruptible power supply exceeds a limit, allowing only the bypass feed path to supply power to the load;

incrementing a first counter while the output current of the uninterruptible power supply exceeds the limit;

decrementing the first counter while the output current does not exceed the limit; and

when the first counter has been decremented to a particular value or less, allowing the bypass feed path or the inverter feed path, or both, to supply power to the load.

17. The method of claim 16, wherein the first power supply disturbance and the second power supply disturbance respectively comprise a different one of the following power supply disturbances:

an instantaneous voltage error, a root mean square output voltage error, an output short circuit, a failure of a static switch module of the bypass feed path, a missing input phase of the bypass feed path, or a neutral current.

18. The method of claim 16, wherein the first transient modality and the second transient modality respectively comprise a different one of the following transient modalities:

a forced commutation of a static switch module of the bypass feed path, a soft magnetization of an output transformer of the inverter feed path, a transition with reduced transient stiffness, or a transition with delayed load sharing.