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Publications

Publications by CPES

2018

Improving the Brazilian electricity market: how to replace the centralized dispatch by decentralized market-based bidding

Authors
Calabria, FA; Saraiva, JT; Rocha, AP;

Publication
JOURNAL OF ENERGY MARKETS

Abstract
The Brazilian electricity market is characterized by having around 65% of its installed capacity coming from hydropower plants, with multiple agents coexisting in the same hydro cascades. Currently, it also contains certain peculiarities that distinguish it from other markets, such as the Energy Reallocation Mechanism (MRE), a centerpiece of the Brazilian market's design. This paper proposes replacing the MRE with a bid-based short-term market called the virtual reservoir model. To simulate the behavior of the hydros in this new market, an agent-based model is implemented using the reinforcement Q-learning algorithm, simulated annealing and linear programming. In the simulations, we use real data - encompassing more than 98% of the total hydro installed capacity and three years of market data - from the Brazilian power system. The results indicate that the management of (virtual) reservoirs can be the responsibility of each hydro: these can save water according to their own risk perceptions, while maintaining current efficiency and security levels. The results also suggest that the final monthly short-term market prices can substantially decrease in comparison with the current prices.

2018

Optimal allocation of maneuver devices in distribution networks for reliability improvement

Authors
Junior, AC; De Oliveira, LW; Dias, BH; De Oliveira, EJ; Gomes, PV; Coelho, MDP; Saraiva, JT;

Publication
20th Power Systems Computation Conference, PSCC 2018

Abstract
A flexible control of the distribution system is an efficient strategy to enhance the grid reliability and quality of service, in this sense, the maneuver devices play an important role to reach flexibility under network faults. In this direction, the present work proposes a new approach to solve the allocation problem of optimal maneuver devices in electric distribution systems (EDS) that considers both permanent and temporary faults. The considered maneuver devices are normally closed switches coupled to the beginning or to the end of distribution branches. The objective is to improve the system reliability with minimal investment cost. The metaheuristic and bio-inspired technique known as artificial immune system (AIS) is applied to handle the discrete feature of the switch allocation problem. The index considered to evaluate the reliability is the system expected outage cost to customers due to supply outages (ECOST). The paper includes a case study with four different simulations using the well-know RBTS Bus 4 test system The obtained results were compared to the literature ones and proved that the proposed approach can lead to promising solutions that establish a suitable trade-off between the reliability and the utility costs. © 2018 Power Systems Computation Conference.

2018

Behavior of the Iberian Electricity Market Prices in 2016 Considering Increasing Values of Feed-in Generation

Authors
Teixeira, JP; Saraiva, JT;

Publication
2018 15TH INTERNATIONAL CONFERENCE ON THE EUROPEAN ENERGY MARKET (EEM)

Abstract
This paper results from the research conducted by the first author during the preparation of his MSc Thesis. This research aimed at investigating the impact on the market prices of the Iberian Electricity Market, MIBEL, due to increases of the feed-in generation, as such an increase is expected to occur in the next few years, namely for PV systems. This research was conducted using real market data publicly available in the web site of the Iberian Market Operator for 2016. To estimate this impact, for each trading hour of 2016 we considered new segments at price 0,0 (sic)/MWh to translate the priority given to this type of generation. These segments representing the new feed-in generation were then used together with the selling bids submitted by market agents to build the new aggregated selling curve. The new market price was finally obtained as the intersection of the new selling curve with the original buying curve, that was assumed unchanged. The global result indicates that if the feed-in generation increases by 25% regarding the values of 2016, then the average annual market price decreases by 6,57 % regarding the original value of 39,42 (sic)/MWh.

2018

Generation Expansion Planning in Brazilian Competitive Multi-Market Framework

Authors
Coelho, MDP; Saraiva, JT; Pereira, AJC;

Publication
2018 15TH INTERNATIONAL CONFERENCE ON THE EUROPEAN ENERGY MARKET (EEM)

Abstract
Most generation expansion planning (GEP) methodologies developed under the monopolistic power industry framework were based on optimization models considering static and detailed descriptions of the power system's equipment and operating conditions. Many of these techniques are still in use in the current market framework, although planning in a liberalized environment is affected by a set of uncertainties and dynamics that traditional models are not designed to capture. In this setting, this research describes a GEP approach that uses System Dynamics (SD) to construct a simulation tool to provide planners, regulators, policy and decision makers with strategic and broader insights regarding policies to apply to power systems. The developed tool models the four Brazilian electricity submarkets, providing electricity prices and expansion scenarios in each region, given that policies recently applied at a country level are leading to different outcomes in each of these submarkets.

2018

Evaluation of the Impact of Shifting Demand from Peak to Adjacent Hours in the Social Welfare Function of the Iberian Electricity Market, MIBEL

Authors
Pinto, PT; Saraiva, JT;

Publication
2018 15TH INTERNATIONAL CONFERENCE ON THE EUROPEAN ENERGY MARKET (EEM)

Abstract
This paper reports the main results obtained by the first author in the preparation of his MSc Thesis. The motivation for this work resulted from the intention announced by the Portuguese Regulatory Agency for the Energy Services to introduce dynamic tariffs as a way to induce a change of the behavior of some consumers in terms of moving some demand from peak periods to the adjacent hours. This is reported to lead to loss reductions, postponement of grid investments and generation cost reductions. In the case of Portugal, given the participation in the common market with Spain, generation costs are not publicly available so that it was investigated how the Social Welfare Function, SWF, that is maximized by the market operator would change given these demand transfers. The simulations were done using real market data for 2016 and the results suggest that the advantages are unclear since the SWF would be almost unchanged or slightly reduced.

2018

Modulation Strategy for a Single-Stage Bidirectional and Isolated AC-DC Matrix Converter for Energy Storage Systems

Authors
Varajao, D; Araujo, RE; Miranda, LM; Lopes, JAP;

Publication
IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS

Abstract
This paper presents a new modulation and control strategies for the high-frequency link matrix converter (HFLMC). The proposed method aims to achieve controllable power factor in the grid interface as well as voltage and current regulation for a battery energy storage device. The matrix converter (MC) is a key element of the system, since it performs a direct ac to ac conversion between the grid and the power transformer, dispensing the traditional dc-link capacitors. Therefore, the circuit volume and weight are reduced and a longer service life is expected when compared with the existing technical solutions. A prototype was built to validate the mathematical analysis and the simulation results. Experimental tests developed in this paper show the capability of controling the grid currents in the synchronous reference frame in order to provide grid services. Simultaneously, the battery current is well regulated with small ripple, which makes this converter ideal for battery charging of electric vehicles and energy storage applications.

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