NMIR was implemented to take advantage of the new HVDC controls that enabled reserve response from one island to cover AC events in the other island. These changes reduced the amount of reserves required to maintain system security, releasing more generation from the reserve market to the energy market, creating market benefits.
Since the implementation of NMIR, significant volumes of post NMIR power system information is now available. This has enabled the refinement of reserve sharing constraints modelled in the Scheduling Dispatch and Pricing tool when the HVDC energy transfer is below 285 MW. When the transfer is below 285 MW refinements will benefit industry participants by:
1. Increasing predictability of inter-island price separation and dispatch.
2. Reducing oscillatory behaviour on the HVDC.
3. Reducing the amount of reserves required to maintain system security.
Removing the current reverse FIR sharing constraint and hence the sticky point, however, requires introducing new constraints for FIR to model different physical limitations of the HVDC. These are not required in the current design as they are already implicitly covered. The new constraints may result in sticky point behaviour at 190 MW but will be significantly less than the sticky points currently observed.
A full report covering the NMIR Refinement is linked below.
NMIR Refinements Document [ pdf 2.42 MB ]
An industry workshop was held on the 12th February in Transpower's Wellington office, the following it the information that was presented.
NMIR Refinement Industry Forum Slide Pack [ pptx 2.18 MB ]
NMIR Refinement Feedback and Questions [ pdf 476.34 KB ]