version, to correct CPD Price in the case of over-constrained dispatch (OCD)

On Wednesday 20th March 2024 we released ez2view version to correct instances of incorrect CPD Price during Over-Constrained Dispatch periods.

This was communicated directly with a number of clients on this day (e.g. GR Case 00006635) … and belatedly via this back-dated Release Note here.


What’s the CPD Price?

As noted in this Glossary Page at WattClarity, the Connection Point Dispatch Price is our name for the constraint adjusted nodal price for a given DUID … but at the Regional Reference Node (i.e. not taking into account the individual marginal loss factor for that DUID, to ensure comparability across all DUIDs in a region, or in a constraint equation).

(a)  What’s it for?

For a Generation DUID, it’s the price that they need to bid at, or under, in order to gain a non-zero dispatch target from NEMDE (the inverse for a Load).

(b)  Inside ez2view

It’s used within several widgets inside of ez2view, including:

    • The ‘Unit Dashboard’ widget for a given DUID; and
    • The ‘Constraint Dashboard’ widget for a given Constraint Equation.

(c)  Elsewhere

It’s also reported in places such as the GSD2023.


What’s the situation?

We’d particularly noted instances of OCD during the day on Tue 13th Feb 2024 with the ‘Significant Power System Event’ in Victoria (i.e. dispatch intervals 13:20 to 14:30 inclusive).

After noticing some instances where the CPD Price we were displaying in ez2view at the time did not appear correct, we invested some time to understand the situation more fully.

(a)  On 20th February 2024, Allan O’Neil wrote ‘Victorian renewable generation on 13 February 2024: One picture and a thousand (sorry, many more) words which contained a section about OCD (Section 7).

(b)  On 22nd June 2016 the AEMO published this ‘Over-Constrained Dispatch Rerun Process’ that helps to explain what happens in cases such as these.

In simple terms what it means is that, during OCD periods:

(a)  In real time, the ‘correct’ CPD Price may (or in many cases not) be able to calculated from the information that’s published in the EMMS;

(b)  Certainly after the fact (e.g. Time-Travelling back to ‘yesterday’) it’s even more likely that the CPD Price can’t be calculated for any DUID during these OCD dispatch intervals  with the information in the EMMS.


What’s the resolution?

So the short story is that showing the ‘correct’ CPD Price will be quite complicated … as a result of which we are following a multi-step process to resolving this issue:

Step # When What?

Step 1

Wed 20th March 2024

Release of ez2view v9.9.1.98

In this version we enhanced the code to ensure that, during periods of OCD where the data in the EMMS (either in real time or in time-travel) is insufficient to calculate the CPD Price, these data fields will now be shown as blank

Step 2

In the future

Future Version A

We intend to enhance existing widgets that contain the CPD Price such that, on occasions when the CPD Price is shown as blank because of the above, via tool tip or other structure we’ll provide the user with more explanation of why the data is blank

Step 3

(Possibly further) in the future

Future Version B

Via our investigations we have confirmed that (outside of the EMMS) it is possible to calculate the CPD Price on many occasions.

We will, as a future upgrade to the software, build the functionality to deliver this data.

Step 4

(Possibly further) in the future

Future Version C

Whilst we are doing the above, we have identify other widgets within ez2view that would benefit from having access to the CPD Price, and would look to enhance these widgets.