received by the International Bureau on 02 October 2020 (02.10.2020)

1 . A system for controlling power walk-in for an uninterruptible power supply (UPS) being switched to receive AC power from an AC generator, the system comprising: a control system; and

a power walk-in (PWI) subsystem controlled in part by the control system, and including:

the PWI subsystem configured to control at least one of an input current or an input power of an AC signal being provided by an AC generator during a power walk-in operation to maintain a minimum frequency of the AC signal from the AC generator during the power walk-in operation.

2. The system of claim 1 , wherein the PWI subsystem further comprises a user settable minimum generator frequency control for enabling a user to set the minimum frequency for the AC signal from the AC generator, which the frequency of the AC signal is not to drop below while the power walk-in operation is being carried out.

3. The system of claim 1 , wherein the power walk-in subsystem is further configured to determine when the AC generator has assumed an entire UPS load, and subsequently to continuously monitor the load for an increase in the load to a new load level, and when an increase is detected that produces a drop in a frequency of the AC signal from the generator to a level below the minimum frequency, then initiating an additional operation to cause the UPS to supplement the AC signal being provided by the AC generator.

4. The system of claim 1 , wherein the PWI subsystem is configured to determine if the power walk-in time occurs within a predetermined maximum power walk-in time period.

5. The system of claim 1 , wherein the PWI subsystem further comprises a user settable maximum power walk-in time control for enabling a user to manually set the predetermined maximum power walk-in time period.

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6. The system of claim 5, wherein the PWI subsystem is configured to detect when the power walk-in time will not occur within the maximum power walk-in time period while maintaining the frequency of the AC signal being output from the AC generator at the minimum AC frequency.

7. The system of claim 5, wherein the PWI subsystem is further configured to modify the minimum generator frequency when the PWI subsystem has detected that the power walk-in time will not occur within the maximum power walk-in time period.

8. An uninterruptible power supply (UPS) able to control a power walk-in operation when the UPS is being switched to receive AC power from an AC generator, the UPS comprising:

a control system; and

a power walk-in (PWI) subsystem controlled in part by the control system and configured to control at least one of an input current or an input power of an AC signal being provided by an AC generator during a power walk-in operation to either:

at least attempt to maintain a minimum frequency of the AC signal from the AC generator during the power-walk-in operation; or

ensure that the power walk-in time occurs within a predetermined maximum power walk-in time period; and

the PWI subsystem further including a user settable minimum generator frequency control for enabling a user to set a minimum value for the frequency of the AC signal from the AC generator, which the PWI subsystem maintains while the power walk-in operation is being carried out.

9. The UPS of claim 8, wherein the PWI subsystem further comprises a user settable maximum power walk-in time control for enabling a user to set a maximum time period within which the power walk-in time must occur.

10. The UPS of claim 8, wherein the power walk-in subsystem is further configured to determine when the AC generator has assumed the entire UPS load, and subsequently to continuously monitor the load for an increase in the load to a new load level, and when an increase is detected that results in a change that causes the frequency

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1 1 . The UPS of claim 8, wherein the PWI subsystem is configured to detect when it will not be possible for the power walk-in time to occur within the maximum power walk- in time period while maintaining the frequency of the AC signal being output from the AC generator at the minimum AC frequency.

12. The UPS of claim 1 1 , wherein the PWI subsystem is further configured to modify the minimum generator frequency when the PWI subsystem has detected that the power walk-in time will not occur within the maximum power walk-in time period.

13. A method for controlling power walk-in for an uninterruptible power supply (UPS) being switched to receive AC power from a AC generator, the method comprising: setting a minimum frequency which a frequency of the AC signal from the AC generator is not to drop below; and

controlling at least one of an input current or an input power of the AC signal being provided by the AC generator during a power walk-in operation to maintain a minimum frequency of the AC signal from the AC generator during the power walk-in operation.

14. The method of claim 13, further comprising determining if the power walk-in time can occur within a predetermined maximum power walk-in time period.

15. The method of claim 14, further comprising detecting when it will not be possible for the power walk-in time to occur within the maximum power walk-in time period while maintaining the frequency of the AC signal being output from the AC generator at the minimum AC frequency.

16. The method of claim 15, further comprising allowing the minimum generator frequency to be adjusted when it is detected that the power walk-in time will not occur within the maximum power walk-in time period, to ensure that the power walk-in time can occur within the maximum power walk-in time period.

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17. The method of claim 13, further comprising determining when the AC generator has assumed the load of the UPS, and subsequently continuously monitoring the load for an increase in the load to a new load level, and when an increase in the load is detected which causes the frequency of the AC signal being output from the AC generator to drop below the minimum AC frequency, then using the UPS to supplement the output of the AC generator.

18. The method of claim 14, wherein the predetermined maximum power walk-in time period comprises a user settable maximum power walk-in time period.

19. The method of claim 13, wherein the minimum frequency comprises a user settable minimum frequency.

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