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Publications

Publications by CPES

2018

Control Room Requirements for Voltage Control in Future Power Systems

Authors
Coelho, A; Soares, F; Merino, J; Riano, S; Lopes, JP;

Publication
ENERGIES

Abstract
In future power grids, a large integration of renewable energy sources is foreseen, which will impose serious technical challenges to system operators. To mitigate some of the problems that renewable energy sources may bring, new voltage and frequency control strategies must be developed. Given the expected evolution of technologies and information systems, these new strategies will benefit from increasing system observability and resources controllability, enabling a more efficient grid operation. The ELECTRA IRP project addressed the new challenges that future power systems will face and developed new grid management and control functionalities to overcome the identified problems. This work, implemented in the framework of ELECTRA, presents an innovative functionality for the control room of the cell operator and its application in assistance with the voltage control designed for the Web-of-Cells. The voltage control method developed uses a proactive mode to calculate the set-points to be sent to the flexible resources, each minute, for a following 15-min period. This way, the voltage control method developed is able to mitigate voltage problems that may occur, while, at the same time, contributes to reduce the energy losses. To enable a straightforward utilization of this functionality, a user interface was created for system operators so they can observe the network state and control resources in a forthright manner accordingly.

2018

The role of Low-Voltage-Ride-Through capability of Distributed Energy Resources for the mitigation of voltage sags in Low Voltage distribution grids

Authors
Rodrigues, J; Lopes, A; Miranda, L; Gouveia, C; Moreira, C; Pecas Lopes, JP;

Publication
2018 POWER SYSTEMS COMPUTATION CONFERENCE (PSCC)

Abstract
The large scale integration of Distributed Energy Resources (DER) at the Low Voltage (LV) distribution network offers new opportunities for the improvement of power quality and network reliability. Currently, the occurrence of large disturbances at the transmission network causing severe voltage sags at the distribution level could lead to the disconnection of a large share of DER units connected to the LV network, causing a more severe disturbance. In this paper, Low-Voltage-Ride Through (LVRT) requirements and current support strategies are proposed to mitigate the impact of severe voltage sag at the distribution level for DER units connected to LV network. The impact of adopting the proposed LVRT strategies will be analyzed through simulation and experimentally. A developed in house ESS prototype incorporating the developed LVRT strategies is also presented, and its capacity to comply with the proposed LVRT requirements is demonstrated using an experimental Power Hardware-in-the-Loop (PHIL) setup.

2018

EMI Filter Design for a Single-stage Bidirectional and Isolated AC-DC Matrix Converter

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

Publication
ELECTRONICS

Abstract
This paper describes the design of an electromagnetic interference (EMI) filter for the high-frequency link matrix converter (HFLMC). The proposed method aims to systematize the design process for pre-compliance with CISPR 11 Class B standard in the frequency range 150 kHz to 30 MHz. This approach can be extended to other current source converters which allows time-savings during the project of the filter. Conducted emissions are estimated through extended simulation and take into account the effect of the measurement apparatus. Differential-mode (DM) and common-mode (CM) filtering stages are projected separately and then integrated in a synergistic way in a single PCB to reduce volume and weight. A prototype of the filter was constructed and tested in the laboratory. Experimental results with the characterization of the insertion losses following the CISPR 17 standard are provided. The attenuation capability of the filter was demonstrated in the final part of the paper.

2018

Microgrid demonstration projects and pilot sites

Authors
Gouveia, C; Moreira, C; Rua, D; Lopes, JP;

Publication
Microgrids Design and Implementation

Abstract
Within the smart grid (SG) paradigm, the microgrid (MG) concept has been pointed out as a pathway for the implementation of future smart distribution networks since it extends and decentralizes the distribution network monitoring and control capability and provides key self-healing capabilities to low voltage (LV) networks. The increased interest on the MG concept has led to several demonstration activities that have been exploited worldwide. Therefore, this chapter provides an overview regarding some of the laboratorial infrastructures and pilot sites dedicated to development of MG and SG concepts. Additionally, it is presented and discussed the development of a specific SG laboratorial infrastructure following the MG concept.

2018

Impacts of Low-Carbon Fuel Standards in Transportation on the Electricity Market

Authors
Karnama, A; Pecas Lopes, JAP; da Rosa, MA;

Publication
ENERGIES

Abstract
Electric Vehicles (EVs) are increasing the interdependence of transportation policies and the electricity market dimension. In this paper, an Electricity Market Model with Electric Vehicles (EMMEV) was developed, exploiting an agent-based model that analyzes how carbon reduction policy in transportation may increase the number of Electric Vehicles and how that would influence electricity price. Agents are Energy Service Providers (ESCOs) which can distribute fuels and their objective is to maximize their profit. In this paper, the EMMEV is used to analyze the impacts of the Low-Carbon Fuel Standard (LCFS), a performance-based policy instrument, on electricity prices and EV sales volume. The agents in EMMEV are regulated parties in LCFS should meet a certain Carbon Intensity (CI) target for their distributed fuel. In case they cannot meet the target, they should buy credits to compensate for their shortfall and if they exceed it, they can sell their excess. The results, considering the assumptions and limitations of the model, show that the banking strategy of the agents contributing in the LCFS might have negative impact on penetration of EVs, unless there is a regular Credit Clearance to trade credits. It is also shown that the electricity price, as a result of implementing the LCFS and increasing number of EVs, has increased between 2% and 3% depending on banking strategy.

2018

Analysis of spinning reserves in systems with variable power sources

Authors
Fonte, PM; Monteiro, C; Barbosa, FM;

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

Abstract
In this paper is studied an approach based on risk assessment to solve the scheduling of a power production system with variable power sources. The spinning reserves resulting from the unit commitment are analyzed too. In this methodology there are no infeasible solutions, only more or less costly solutions associated to the operation risks, such as, load or renewable production curtailment. The uncertainty of forecasted production and load demand are defined by probability distribution functions. The methodology is tested in a real case study, an island with high penetration of renewable power production. Finally, forecasted and measured reserves are compared, once the reserves are strongly linked with the forecasting quality. The results of a real case study are presented and discussed. They show the difficulty to achieve complete robust solutions.

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