Grid Tie Three Phase Voltage PWM converters can be conceived as current sources that inject currents into the grid at the point of common coupling (PCC). In order to achieve a good performance, the voltage source inverter (VSI) should be commanded by a current controller to track as accurate as possible a current reference. Pulse with modulation (PWM) and space vector modulation (SVM) are two techniques used in VSIs to generate the time average output voltage demanded by the current controller. By using the average model of the VSI, controlled either by PWM or by SVM, we can use feedback linear control for the analysis and design of the current controller. The main goal of this technical paper is to illustrate an analytical formula to calculate the gains of the proportional-integral current controller. The gains are calculated based on the values of the coupling inductivity, the DC Bus voltage and the switching frequency and given for two PWM modulation methods.
Authors: Rodrigo Zenon Guzman Iturra (University of Applied Sciences Südwestalen), Peter Thiemann (University of Applied Sciences Südwestfalen),
Hide Authors & Abstract

The present document illustrates two formulas that determine the maximum amount of harmonic active power PH that can be recovered by power quality conditioners such as an harmonic active power filter in a three-wire three-phase system that contains linear and nonlinear loads. The upper bound (O) of the harmonic active power O(PH) is the total harmonic apparent power SeH. The upper bound is given in function of the Total Harmonic Distortion (THD) of the current (THDI) and the voltage (THDU) measured at the point of common coupling (PCC) and total apparent power Se of the loads.
Authors: Rodrigo Zenon Guzman Iturra (University of Applied Sciences Südwestalen), Peter Thiemann (University of Applied Sciences Südwestfalen),
Hide Authors & Abstract

This paper presents a comparative analysis of different modulation techniques that can be applied to a dual active bridge (DAB) converter, validating its performance with the realization of computational simulations. A DAB converter is an isolated dc-dc topology with great applicability in the most diverse branches of power electronics, as is the case of energy storage systems, solid state transformers, power electronic traction transformers, and dc/hybrid microgrids. In this sense, several strategies have been studied to mitigate circulating currents, expand the zero voltage switching operating range, and reduce reactive power. One of the possible solutions to increase the efficiency of this converter is to adopt specific modulation techniques, however, it is necessary to assess which one has a better cost-benefit ratio. Thus, this paper presents a comparative analysis between: (i) Duty cycle modulation; (ii) Single phase shift (SPS); (iii) Dual phase shift (DPS); (iv) Extended phase shift (EPS); (v) Triple phase shift (TPS). Specifically, this study aims to investigate the performance of a DAB when controlled by the aforementioned strategies and operating with a nominal power of 3.6 kW. By analyzing the simulation results, it was shown that only SPS, DPS, and TPS techniques are considered suitable for this particular case. Duty cycle modulation presents time limitations during the power transfer, whilst EPS is more suitable for dynamic medium/high power applications.
Authors: Sérgio Coelho (University of Minho), Tiago J. C. Sousa (University of Minho), Vitor Monteiro (University of Minho), Luís Machado (University of Minho), Joao L. Afonso (University of Minho), Carlos Couto (Universty of Minho),
Hide Authors & Abstract

In this paper, a smart greenhouse project has been presented as an example of a sustainability-focused learning experience for undergraduates. The concept of sustainability has generated a tremendous amount of interests in the recent years in all fields of education including and beyond natural and applied sciences, engineering, and technologies. While project-based instruction and learning experience has already gained enough momentum in all of the aforementioned fields of education, the inclusion of sustainability perspectives from the science and engineering fields of studies is yet to make its room in the current course curricula as well as in the mindset of new generations of engineering undergraduates. This smart greenhouse project is an example of how sustainability can be brought into a classroom setting of engineering and technology programs as a project-based learning experience. The objective of this smart greenhouse project is to create an automated system capable of growing vegetation with little human input by utilizing electricity, computer programming, and a microcontroller operation. While this project was implemented by a group of two students with electrical engineering technology (EET) major as parts of their course requirements at the University of Wisconsin-Green Bay, a similar sustainability-focused learning approach can be applied successfully in other courses at different levels of engineering and technology programs at other academic institutions.
Authors: Mohammad Mahfuz (University of Wisconsin-Green Bay), Rick Todd Kaske Jr (University of Wisconsin-Green Bay, USA), Brady Connaher (University of Wisconsin-Green Bay, USA),
Hide Authors & Abstract

Renewable energy technologies in OECD countries have been highly promoted for the purpose of producing cleaner energy and better life conditions for people in urban areas. However, devel-oping countries require an extended analysis to assess the feasibility for their implementation, identifying financial risks and settling emissions reduction. In Colombia, in the last few years, there have been enhanced public policy strategies to enlarge energy supply alternatives and ac-complishing the COP 21 limits of 20% GHG reduction before 2030. In this work, it was devel-oped a methodology based on Multicriteria Decision Making Methods (MCDM) to assess com-paratively new renewable energy technologies with renewable energy technologies currently used in the country based on technical, financial, and environmental criteria. The methodology allows to identify the best and the worst alternative from the output ranking, considering the numerical value of criteria placed on the decision matrix and the dominance index output. The methodology was used in order to assess comparatively ocean energy technologies in Colombia. It was identi-fied that tidal range is the best alternative and ocean current the worst among the projects evaluated.
Authors: David Serrato Tobón (Universidad Tecnológica de Pereira), Juan Castillo (Universidad Tecnológica de Pereira), Laura Salazar (Universidad Tecnológica de Pereira), Alejandro Hernández (Universidad Tecnológica de Pereira), Harold Salazar (Universidad Tecnológica de Pereira), Juan Tibaquirá (Universidad Tecnológica de Pereira), Álvaro Restrepo (Universidad Tecnológica de Pereira), Juan López (Universidad Tecnológica de Pereira), Tatiana Loaiza (Universidad Tecnológica de Pereira),
Hide Authors & Abstract

Phase-Locked Loop (PLL) circuits have contributed to modernise electrical grids in different segments, such as distributed generation, identification and characterisation of phenomena related to power quality, localisation of faults, among others, and this justify the undergoing researches aiming at increasing their performance under certain conditions. Taking the example of the single-phase PLLs, researchers have worked out ways to cope with the characteristic doubly-frequency oscillation, which can undermines the performance of the frequency and phase tracking and compromise the extraction of the fundamental component from the input signal. In this sense, the present article aims at analysing a single-phase PLL circuit providing a methodology to adjust the PLL's gains and minimise low frequency oscillation. As for the analysed PLL, simulations in both time and frequency domain were carried out for modified versions of the well known EPLL, SOGI-PLL and APF-PLL comprising notch filters and second order integrator.
Authors: Dayane Lessa (Rio de Janeiro State University), Michel Tcheou (Rio de Janeiro State University), Cleiton Freitas (Rio de Janeiro State University), Luís Fernando Monteiro (Rio de Janeiro State University),
Hide Authors & Abstract

LiDAR (Light Detection And Ranging) is a technology used to measure distances to objects. Internally, a LiDAR is constituted by several components, including a power supply, which is responsible to provide the distinct voltage levels necessary for all the components. In this context, this paper presents an efficiency comparison of three different DC-DC converter architectures for a LiDAR, each one composed of three DC-DC converters: in parallel; in cascade; and hybrid (mix of parallel and cascade). The topology of the adopted integrated DC-DC converters is the synchronous buck switched-mode power supply (SMPS), which is a modified version of the basic buck SMPS topology. Three distinct SMPSs were considered: LM5146-Q1, LM5116, and TPS548A20RVER. These SMPSs were selected according to the requirements of voltage levels, namely, 12 V, 5 V, and 3.3 V. Along the paper, the principle of operation of the SMPSs is presented, as well as the evaluation results obtained for different operating powers, allowing to establish a comprehensive efficiency comparison.
Authors: Ruben Figueiredo (ALGORITMI Research Centre, University of Minho), Vitor Monteiro (University of Minho), Luiz Alberto Lisboa Cardoso (University of Minho), Jose Afonso (University of Minho), José Gabriel Oliveira Pinto (University of Minho), José Salgado (Universidade do Minho), Miguel Nogueira (Bosch Car Multimedia Portugal, S.A. Rua do Barrio de Cima, nº1, 4705-820 Braga, Portugal;), Aderito Abreu (Bosch Car Multimedia Portugal, S.A. Rua do Barrio de Cima, nº1, 4705-820 Braga, Portugal;), Joao L. Afonso (University of Minho),
Hide Authors & Abstract

This paper presents a single- phase current-source converter (CSC) combined with a hybrid converter on the dc-link, allowing to interface an electric vehicle (EV) and a renewable energy source (RES). Therefore, the interface with the power grid is only performed through the CSC, which also permits the operation as shunt active power filter (SAPF), allowing to compensate power quality prob-lems related with current. The whole system is composed by two main power stages, namely, the CSC that is responsible for compensating the current harmonics and low power factor, as well as operating as a grid tied inverter or as an active rectifier, and the hybrid converter that is responsible for interfacing the dc-link of the CSC with the converters for the EV and the RES interfaces. As demonstrated along the paper, the CSC, combined with the hybrid converter on the dc- link, allows the operation as SAPF, as well as the operation in bidirectional mode, specifically for the EV operation, and also for injecting power from the RES. In the paper, the power electronics structure is described and the principle of operation is introduced, supported by the description of the control algorithms. The validation results show the proper operation of the CSC, combined with the hybrid converter on the dc-link, for the main conditions of operation, namely exchanging power with the power grid in bidirectional mode and operating as a SAPF.
Authors: Cátia Oliveira (University of Minho), Joao L. Afonso (University of Minho), Ana Rodrigues (University of Minho), Delfim Pedrosa (University of Minho), Vitor Monteiro (University of Minho),
Hide Authors & Abstract

Residential demand response has been playing an important role in the low carbon energy system transition. Although this is not a new concept, the popularity of Demand Response (DR) programs is growing, driven by the in-creasing opportunities that emerged with smart grid appliances as well as by their potential to support the integration of variable renewables generation. The end-user plays a key role in the successful deployment and dis-semination of these DR programs. This study aims to assess social awareness and acceptance of DR programs, based on a survey for data collection and complemented with the regression models. The results suggest that the eco-nomic determinants, contribution to environmental protection as well as the extent of urbanization are important motivating drivers, to be explored in the future to encourage the residential consumers’ participation in DR programs.
Authors: Paula Ferreira (Universidade do Minho), Rocha Ana (Universidade do Minho), Araújo Madalena (Universidade do Minho),
Hide Authors & Abstract

The penetration of battery electric vehicles is increasing. Due to their ability to store electrical power and to shift charging events, they offer a wide range of opportunities with regard to renewable grid integration and lowering the overall CO2 emissions. This is particularly evident for isolated microgrids, such as the Portuguese island of Porto Santo. In this paper, we conduct a data analysis of real-world charging data of 20 electric vehicles operated on the island of Porto Santo. We provide insights into the charging behavior of different users and analyze the opportunity of smart charging for better renewable grid integration using linear optimization models. The data analysis shows that drivers prefer home rather than publicly available charging stations, flexible charging events occur mostly overnight and the charging flexibility of the fleet decreases over the project duration. With regard to make charging more flexible, we can see that smart charging can help to raise the share of electricity generated by renewable energy sources for charging the electric vehicles to up to 33%.
Authors: Leo Strobel (Friedrich-Alexander-University Erlangen-Nürnberg), Jonas Schlund (Friedrich-Alexander-University Erlangen-Nürnberg), Veronika Brandmeier (The Mobility House), Michael Schreiber (The Mobility House), Marco Pruckner (Friedrich-Alexander-University Erlangen-Nürnberg),
Hide Authors & Abstract

The paper presents a real-time error correction method that accurately estimates the primary quantity of an inductive instrument transformer – that is, a voltage or current transformer – based on a Dynamic-State-Estimation (DSE) op-timization approach. The DSE error-correction method uses a high-fidelity model of the voltage transformer (VT) instrumentation channel (IC) and the Unconstrained-Weighted-Least-Squares (UWLS) optimization approach to accurately estimate the VT pri-mary voltage; thus, correcting for errors generated in the instrumentation chan-nel. Specifically, the method involves obtaining discretized measurements of the VT burden voltage signal through a continuous monitoring process. The VT pri-mary voltage is then continuously estimated by the method based on fitting the continuously obtained measurement samples to the high-fidelity VT model. The continuously estimated primary voltage can then be made readily available for metering, protection, and control functions. The method can be implemented us-ing microprocessor technology, for example, in Merging Unit (MU) applications for digital power substation architectures. The paper will focus on evaluating the performance of the DSE error-correction method, applied to inductive voltage transformer (VT) instrumentation channel (IC) applications, in the estimation of primary voltage signals distorted by harmonics. The evaluation process will leverage multiple Fourier analyses techniques.
Authors: Chukwuemeka Obikwelu (Georgia Institute of Technology), Sakis Meliopolous (Georgia Institute of Technology),
Hide Authors & Abstract

Nowadays electrical energy presents itself as the most promising solution to sat-isfy the energy needs of smart cities. For electrical energy to be managed effi-ciently and sustainably, the use of power electronic converters is essential. The evolution of semiconductors, in terms of blocking voltages, conduced current and switching frequencies, led to the emergence of new topologies for more robust and compact power electronics converters with high-frequency galvanic isolation. However, for high and medium voltage applications, such as electric railways, wind turbines, solar photovoltaic, or energy distribution systems, the semicon-ductor blocking voltages are still below the values in demand. In order to solve this problem, modular multilevel converters (MMC) has been implemented, re-quiring more sophisticated control algorithms and complex pulse width modula-tion (PWM) techniques, such as space vector modulation. In this paper, different topologies to be integrated in an MMC are presented, as well as PWM techniques for MMC, making a comparative analysis based on computer simulations of different PWM techniques. An MMC consisting of 4 full-bridge DC-AC power converters connected in series was considered as the study basis for the analysis of the PWM techniques.
Authors: Luis Barros (University of Minho), Mohamed Tanta (UMINHO), Antonio Martins (University of Porto - Faculty of Engineering), Joao L. Afonso (University of Minho), José Gabriel Oliveira Pinto (University of Minho),
Hide Authors & Abstract