Adding README

README.md

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+vSPD
+====
+
+vectorised Scheduling, Pricing and Dispatch - an audited, mathematical replica of SPD, the
+pricing and dispatch engine used in the New Zealand electricity market.
+
+[Input GDX files are published daily on EMI](https://www.emi.ea.govt.nz/Wholesale/Datasets/FinalPricing/GDX/) or 
+can be obtained directly from the underlying Azure storage account (see [instructions](https://www.emi.ea.govt.nz/Forum/thread/new-access-arrangements-to-emi-datasets-retirement-of-anonymous-ftp/) 
+on the EMI forum).
+
+The Electricity Authority created vSPD using the GAMS software in 2008. Dr Ramu Naidoo was
+the original author and, until November 2013, the custodian of vSPD. Tuong Nguyen and Phil Bishop
+from the Data and Information Management team now maintain the vSPD model.
+
+vSPD was most recently audited in August 2019 - see the audited vSPD codes and the auditor's certification on the [EMI vSPD page](https://www.emi.ea.govt.nz/Wholesale/Tools/vSPD).
+
+Throughout 2022, vSPD was extensively modified to accomodate the 1 November 2022 go-live of real-time pricing. Backward 
+compatability with GDX files was broken with this change. Version 3.1.0, available on the [EMI vSPD page,](https://www.emi.ea.govt.nz/Wholesale/Tools/vSPD) is
+the last version of vSPD to work with GDX files pertaining to all days up to and including 31 October 2022. GDX files pertaining to trading day 1 November 2022 
+or later will require vSPD v4.0.0 (or later).
+
+Contact: [email protected]