# Prediction of Intraday Electricity Supply Curves
###### Abstract  
The electricity market in Spain, as in many European countries, is organized into daily, intraday, and reserve markets. This project aims to predict the supply curves in the Spanish intraday market that have six sessions with different horizons of application, using information from the market itself. To achieve this, we approximate these curves using a non-uniform grid of points and evaluate the quality of these approximations with a weighted distance, both based on empirical market data. We employ neural network models, including multilayer perceptrons (MLPs), convolutional neural networks (CNNs), long short-term memory (LSTM), bidirectional LSTM (BiLSTM), and a Transformer network alongside a naive model for benchmarking. The MLP and CNN models demonstrated significant improvements in predicting these supply curves for the six market sessions. BiLSTM; CNN; electricity market; forecast; intraday market; LSTM; MLP; offer curve; Transformer +
Footnote †: journal: Applied sciences  
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(see [3,4]) (In Figure 1: Audax Energia, Comision Nacional de los Mercados y de la Competencia, Endesa, EDP HC Energia, Iberdrola, Gas Natural Fenosa, Nexus, Red Electrica de Espana and Viesgo are official names of companies and regulatory institutions). The Spanish electricity market is actually a set of interconnected markets designed to meet the changing needs of electricity supply and demand. In addition to electricity transactions planned for weeks, months, or years ahead, many trades are conducted with only hours or even minutes of notice before the actual generation of the energy. Given that electrical energy is difficult to store, production at each moment must match the demand. Supply and demand have a volatile nature due to weather conditions, socioeconomic factors, and other variables, highlighting the need to constantly review negotiations in line with current forecasts. Additionally, the energy transmission network must be physically capable of executing what has been agreed upon. Following the 2007 integration of the Spanish electricity market with the Portuguese one in the so-called MIBEL (Iberian Electricity Market), the resulting market was coupled with Europe progressively from 2013, establishing a single price in the connected regions when the system allows it. In the daily market [6], which is organized by OMIE (Iberian Energy Market Operator), energy transactions between generators and consumers are conducted for each of the 24 h of the following day (which is referred to as the 'dispatch day' and is denoted by \(D\)). Once the bids from producers for each hour of the next day are submitted, they are arranged in ascending order, forming the market supply curve for each hour. The bids from buyers are ordered in descending order of price, forming the market demand curve. Finally, the market price for the following day is set by the intersection point of the supply and demand curves. It follows a pay-as-clear system, meaning that all participants, both buyers and sellers, pay the market price established for that period. Following the daily market, participants have the opportunity to buy and sell electricity again in the intraday market, held a few hours before real-time operations, or in the continuous intraday market, which operates under a European crossborder framework [7]. Intraday markets, also organized by OMIE, provide a crucial mechanism for market players to fine-tune their schedules from the daily market to better align with real-time energy demands. Lastly, there are reserve markets through which the system operator, Red Electrica de Espana, ensures the physical feasibility of the previously negotiated generation and distribution of energy, making adjustments to the agreements. In this paper, we focus our attention on the intraday markets, with our goal being to forecast the supply curves of these markets, specifically using information from the market itself and its predecessor.