EMK:Modelling Major Hydro Systems

As at April 2007

Disclaimer

Reasonable care has been taken to ensure that the information in this paper is up to date at the time of issue. Potential users of EMarket should, however, ensure that they evaluate EMarket and this paper through an appropriate evaluation process in consultation with Energy Link. The authors are also reliant on certain information external to EMarket and Energy Link, for which no liability or responsibility can be accepted.

Introduction

This technical bulletin is intended to provide users and interested parties with a detailed explanation of how EMarket’s four major hydro systems are modelled.

This paper includes a brief overview of other features in EMarket and a note on enhancements planned in the short to medium term.

Main Hydro Localisation

Each major hydro system may be represented by one more resources, and the appropriate resource used in each particular simulation run. In this way, each grid may have its own version of each of the main hydros. Each of these may be created as the thermal stations are but each of the main hydros has a separate category on the main screen. For example, you might want to run a simulation with a station added to a major hydro – in this case you would create a new resource of the hydro concerned, add the station, attach the resource to the grid you are using and do the run. This gives you a high degree of flexibility in how you model hydro systems.

The diagrams of the four major hydro systems in this technical bulletin show the default configurations but the user is able to change these, add or delete stations, in order to investigate upgrade or alternative scenarios, e.g. the addition of the now abandoned Project Aqua to the Waitaki hydro system.

In each of the separate hydro entities must run and spill prices and minimum flow are accessible. This facility allows the running of multiple configurations of the main hydros (see New Zealand Major Hydro Systems) without having to change the model's global variables.

Other Documents

This bulletin is one of a series of technical bulletins relating to Energy Link’s EMarket model. Taken together, the bulletins replace the old EMarket User Guide. The full series of bulletins covers an overview of the EMarket model, the details of the four major New Zealand hydro systems modelled in EMarket, water values and hydro offers, power flows, dispatch and nodal pricing, short term river chain optimisation and company optimisation.

Summary

IMPORTANT: The material in this section on offer formulation for the major hydro systems provides background information and relates primarily to the "old code" from v1.3.6.

The following is an overview of the operation and modelling of the main hydro systems. The level of detail has been deliberately chosen to give the user an appreciation of the offering and acceptance dispatch algorithms. It is not intended to detail in extenso the precise workings of each major hydro system's algorithm, nor is it intended to be a full account of the operation of the hydro systems in practice. Rather, it is intended to give the user an insight into the behaviour of the major hydro systems, both as modelled and in practice. Note that if a major hydro system uses Short term River Chain Optimisation then its smaller storages are modelled and its offers are calculated by the optimiser rather than as described here.

In each of the following sections an overview of the system is given, with a diagram showing the principle parts. The key for these is shown on the Waitaki diagram. This is followed by an explanation of the algorithms used to model the offers and post dispatch evaluation. Unless otherwise stated, the information used to put together the major hydro models is taken from resource consent applications, brochures and other sources of information in the public domain.

Note that, in all cases, flow delays are ignored, thus avoiding the need to include inter-period hydro modelling in EMarket.