Frequency keeping control and roundpower information

Frequency Keeping Control (FKC) ties the North and South Island frequencies together by modulating the HVDC transfer.

FKC enables the implementation of national reserves and frequency keeping markets which provides benefit to the electricity market through reduced frequency keeping and reserve costs. Roundpower enables the seamless direction change from north to south HVDC transfer and vice-versa. This also enables reverse reserve sharing in the opposite power direction.

NCC business process for managing FKC when roundpower is disabled

Notification of a change to Roundpower

A CAN will be issued advising whenever Roundpower will be disabled and the expected duration.
There will be no CAN updating the status of FKC during a Roundpower outage.

Disabling Roundpower

Roundpower must be disabled for HVDC live line work or an HVDC pole outage.
Disabling Roundpower means no reverse reserve sharing is available through zero and in the opposite power direction.

FKC enabled (each of FSC, SRS and island-based FK is disabled)

FKC status will normally be enabled, unless there is an offer change from the Grid Owner.
FKC is the normal mode of HVDC operation. Enabling FKC allows the following items to be modelled:
- modelled modulation risk = 30 MW
- NI MFK band = 15 MW; SI MFK band = 15 MW
- MFK operating single frequency source
- SIR reserve sharing enabled.

FKC disabled (each of FSC, SRS and island-based FK is enabled)

Disabling FKC results in the following changes:
- modelled modulation risk = 0 MW
- NI MFK band = 25 MW; SI MFK band = 25 MW
- MFK operating with island based frequency sources
- SIR reserve sharing disabled.

Business process scenario:

Making a decision to change MFK from single frequency source to island-based frequency sources when Roundpower is disabled and HVDC transfers are low.
MFK operating with island-based frequency sources when the HVDC transfer is less than 70MW.
NI MFK band = 25MW; SI MFK band =25MW if both poles are blocked.

FKC status will be modelled as enabled in the NRSS time frame at the start of a 1hr period (2 trading periods) where the scheduled HVDC transfer is continuously greater than 100 MW.

FKC status will be continually monitored to these criteria any time Roundpower is disabled.