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Publications

Publications by CPES

2022

Greater than the sum: On regulating innovation in electricity distribution networks with externalities

Authors
Marques, V; Costa, PM; Bento, N;

Publication
UTILITIES POLICY

Abstract
To modernize distribution networks and enable the energy transition, we need to understand the most appro-priate regulatory approach. A set of new technologies with positive externalities challenge the traditional reg-ulatory models. We develop a decision model to assess firms' incentives to invest in new technologies under different regulatory schemes that consider externality effects. Results show that regulatory schemes under which companies retain the gains (or losses) of achieving (or not) efficiency targets more effectively promote inno-vation investments that reduce network costs. However, a case-by-case approach should be preferred for tech-nologies whose benefits go mostly beyond the network activities.

2022

Improvement of Steady State Performance of Voltage Control in Switched Reluctance Generator: Experimental Validation

Authors
Touati, Z; Pereira, M; Araujo, RE; Khedher, A;

Publication
MACHINES

Abstract
This paper presents a voltage control approach to a Switched Reluctance Generator (SRG) using a Proportional Integral (PI) controller. The principle of operation is described and the considerations in the design of controller are discussed. A current loop transfer function of an SRG with power converter has been systematically derived in order to obtain a small-signal model for the generator. The generated voltage is controlled by manipulation of the setpoint of the current control of the generator. The entire voltage loop controller and current control have been simulated and tested with a 250 W SRG prototype. The control law of the control system was implemented on a digital signal processor (TMS320F28379D). To verify the feasibility of the proposed voltage control, the performances are evaluated by numerical simulations and experimental tests with an 8/6 SRG for different rotational speeds and resistive loads. Experimental results demonstrate that the DC output voltage from SRG can be controlled well using a simple linear controller.

2022

Integration of Switched Reluctance Generator in a Wind Energy Conversion System: An Overview of the State of the Art and Challenges

Authors
Touati, Z; Pereira, M; Araujo, RE; Khedher, A;

Publication
ENERGIES

Abstract
This paper presents a technical overview for Switched Reluctance Generators (SRG) in Wind Energy Conversion System (WECS) applications. Several topics are discussed, such as the main structures and topologies for SRG converters in WECS, and the optimization control methods to improve the operational efficiency of SRGs in wind power generation systems. A comprehensive overview including the main characteristics of each SRG converter topology and control techniques were discussed. The analysis presented can also serve as a foundation for more advanced versions of SRG control techniques, providing a necessary basis to spur more and, above all, motivate the younger researchers to study magnetless electric machines, and pave the way for higher growth of wind generators based on SRGs.

2022

Learning-Based Control for Hybrid Battery Management Systems

Authors
Mirwald, J; de Castro, R; Brembeck, J; Ultsch, J; Araujo, RE;

Publication
Springer Optimization and Its Applications - Intelligent Control and Smart Energy Management

Abstract

2022

An Analytic Hierarchy Process for Selecting Battery Equalization Methods

Authors
Dias, BMD; da Silva, CT; Araujo, RE; de Castro, R; Pellini, EL; Pinto, C; Lagana, AAM;

Publication
ENERGIES

Abstract
Batteries have been the predominant energy storage system used in electric vehicles. Battery packs have a large number of cells that develop charge, thermal, and capacity imbalances over time, limiting the power, range, and lifetime. Electronic battery management and state of charge (SoC) equalization methods are necessary to mitigate such imbalances. Today, it is possible to find a wide range of battery equalization methods in the literature, but how to decide which of these methods should be applied in practice? This paper compares 24 SoC equalization circuits that are typically found in automotive applications. We employ an analytic hierarchy process (AHP) approach to rank these equalization circuits according to multiple decision criteria (energy efficiency, equalization speed, implementation and control simplicity, hardware size, and total price). We also prepared a survey to collect design preferences from multiple battery balancing experts from around the world in order to better understand the relative importance of different criteria. The obtained results confirm that automotive engineers continue to favor passive balancing methods because of their low price, small PCB size, and implementation simplicity-despite the energy efficiency benefits of active balancing.

2022

Comparative Study of Discrete PI and PR Controller Implemented in SRG for Wind Energy Application: Theory and Experimentation

Authors
Touati, Z; Pereira, M; Araujo, RE; Khedher, A;

Publication
ELECTRONICS

Abstract
The Switched Reluctance Generator (SRG) has been widely studied for Wind Energy Conversion Systems (WECS). However, a major drawback of the SRG system adopting the conventional control is the slow response of the DC link voltage controller. In this paper, a Proportional Resonant (PR) control strategy is proposed to control the output voltage of the SRG system to improve the fast response. The SRG model has a high non-linearity, which makes the design of controllers a difficult task. For this reason, the important practical engineering aspect of this work is the role played by the SRG model linearization in testing the sensitivity of the PR controller performance to specific parameter changes. The characteristics of steady-state behaviors of the SRG-based WECS under different control approaches are simulated and compared. The controller is implemented on a digital signal processor (TMS320F28379D). The experimental results are carried out using a 250 W 8/6 SRG prototype to assess the performance of the proposed control compared with the traditional Proportional Integral (PI) control strategy. The experimental results show that the PR control enhances the steady-state performance of the SR power generation system in WECS. Compared to PI control, the rise and settling times are reduced by 45% and 43%, respectively, without an overshoot.

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