Simplified rail power conditioner based on a half-bridge indirect AC/DC/AC modular multilevel converter and a V/V power transformer

This paper presents a comprehensive study about a Simplified Rail Power Conditioner (SRPC) based on a half bridge indirect AC/DC/AC Modular Multilevel Converter (MMC) and a V/V traction power transformer. The proposed system with a half bridge MMC can decrease the costs, reduce the control complexity, and require less hardware devices in comparison with the rail power conditioner based on a full bridge indirect AC/DC/AC MMC. Moreover, the SRPC with a half bridge MMC is able to compensate current harmonics, reactive power, and the Negative Sequence Components (NSCs) of currents, which are caused by the unbalance loads between power grid phases. This paper explains the system architecture and its control algorithms based on a pulse width modulation and a proportional integral controller, which is used to control the compensation currents. The simulation results of the SRPC show the submodule voltage balancing control and the DC bus voltage control in order to verify its effectiveness. The compensation strategy based on the NSCs detection is described and evaluated through simulation results.Mohamed Tanta was supported by FCT (Fundacao para a Ciencia e Tecnologia) PhD grant with a reference PD/BD/127815/2016. This work has been supported by COMPETE: POCI-01-0145-FEDER-007043 and FCT within the Project Scope: UID/CEC/00319/2013.info:eu-repo/semantics/publishedVersio

IoT-enabled Building Automation Systems: Challenges, Opportunities, and Case Studies in Energy Efficiency and user comfort

The integration of Internet of Things (IoT) technology into building automation systems (BAS) has ushered in a new era of smart buildings, revolutionizing the way we design, manage, and inhabit built environments. This abstract provides a comprehensive exploration of IoT-enabled BAS, focusing on the challenges, opportunities, and case studies that shape their role in driving energy efficiency and enhancing user comfort. IoT-enabled BAS face numerous challenges that must be addressed to realize their full potential. These challenges include interoperability issues stemming from the diversity of IoT devices and protocols, concerns regarding data security and privacy, the scalability of IoT deployments to encompass large buildings or portfolios, the inherent complexity of IoT ecosystems, and the upfront costs associated with deployment and maintenance. Despite challenges, IoT-enabled BAS present significant opportunities for improving building performance and occupant well-being. By leveraging real-time data analytics, predictive algorithms, and automated controls, these systems can optimize energy use, personalize occupant comfort preferences, enable remote monitoring and management, facilitate predictive maintenance strategies, and contribute to sustainability goals through efficient resource utilization

Modeling, control and design of AC microgrids in islanded mode

Tesi per compendi de publicacions, amb diferents seccions retallades pels dret de l'editorPremi Extraordinari de Doctorat, promoció 2018-2019. Àmbit de les TICThe present doctoral thesis is focused on the analysis and design of control strategies for the secondary control layer of islanded AC microgrids without the use of communications. The work is submitted as a compendium of publications, composed by journals and international conference papers. The first contribution is a control strategy for the secondary control layer based on a switchable configuration, that does not require the use of communications. For stability analysis purposes, a closed-loop system modeling is presented, which is also used to determine design considerations for the control parameters. The second contribution is a complementary control strategy that improves the frequency regulation of the previous proposed control, using a dynamic droop gain in the primary layer. For this purpose, a time protocol that drives the variable parameters is proposed which guarantees an effectively reduction of the maximum frequency error without relying on complex techniques, maintaining the simplicity of the basis strategy and the non-use of communications. The third contribution is a multi-layer hierarchical control scheme that is composed by a droop-based primary layer, a time-driven secondary layer and an optimized power dispatch tertiary layer. The proposed control guarantees an excellent performance in terms of frequency restoration and power sharing. The fourth contribution is an improved secondary control layer strategy without communications, which presents superior operating performance compared with the previous proposals. The scheme is based on a event-driven operation of a parameter-varying filter which ensures perfect active power sharing and controllable accuracy for frequency restoration. A complete modeling that considers the topology of the MG and the electrical interaction between the DGs is derived for the stability analysis and to determine design guidelines for the key control parameters. For the purpose of analyzing and verifying the operational performance of the control schemes, an experimental MG was implemented, where selected tests were carried out. The obtained results are discussed and its relation with the doctoral thesis objectives analyzed. The thesis ends presenting conclusions and future research lines.La presente tesis doctoral se enfoca en el análisis y diseño de estrategias de control para la capa de control secundaria en microrredes aisladas de corriente alterna, sin el uso de comunicaciones. El trabajo se presenta en la modalidad de compendio, por lo que está compuesto por publicaciones previamente aceptadas en revistas y congresos científicos internacionales. La primera contribución es un estrategia de control para la capa secundaria basada en una configuración conmutable, que no requiere el uso de comunicaciones. Con el propósito de analizar la estabilidad, se presenta el modelado del sistema de lazo cerrado, que también es usado para determinar reglas de diseño de los parámetros de control. La segunda contribución es una estrategia de control complementaria que mejora la regulación de frecuencia de la propuesta anterior, usando una ganancia dinámica en la capa de control primaria. Se propone la variación de los parámetros siguiendo un protocolo de tiempo, garantizando la reducción del error máximo de frecuencia sin depender de técnicas complejas, manteniendo la simplicidad de la estrategia base y sin requerir comunicaciones. La tercera contribución es un esquema de control jerárquico compuesto por una capa primaria basada en el método de la pendiente, una capa secundaria controlada por un protocolo de tiempo y una capa terciaria que optimiza el despacho de potencias. El control propuesto garantiza un excelente desempeño en términos de la regulación de la frecuencia y la compartición de potencias. La cuarta contribución es una estrategia de control para la capa secundaria que no usa comunicaciones, la cual presenta un comportamiento operativo superior comparado con las propuestas anteriores. El esquema está basado en una operación controlada por eventos, de un filtro con parámetros variables que garantiza una perfecta compartición de potencias y una precisa restauración de frecuencia. Además, para el análisis de la estabilidad y la determinación de pautas de diseño de los parámetros se presenta un modelo que considera la topología de la microrred y las interacciones eléctricas de los generadores. Con el objetivo de analizar y verificar el desempeño operativo de los esquemas de control, se implementó una microrred experimental donde se llevaron a cabo las pruebas requeridas. Se discutieron los resultados obtenidos y se analizó su relación con los objetivos de la tesis doctoral. El documento termina presentado las conclusiones así como futuras líneas de investigaciónAward-winningPostprint (published version

PV Parameter Identification using Reduced I-V Data

In this paper, possibility and accuracy of using reduced I-V data in PV parameter identification are discussed. Based on the linear identification method proposed in [1], six I-V points are used instead of the whole I-V curve to identify the PV parameters. The maximum power point (MPP) is then estimated using the identified I-V and P-V characteristics. Validation is done by using different sets of six points on the I-V curve. Experiment results show that the accurate curve fitting (with low RMSE and MPE) and good estimation of MPP can be achieved

A multi-port power conversion system for the more electric aircraft

In more electric aircraft (MEA) weight reduction and energy efficiency constitute the key figures. Additionally, the safety and continuity of operation of its electrical power distribution system (EPDS) is of critical importance. These sets of desired features are in disagreement with each other, because higher redundancy, needed to guarantee the safety of operation, implies additional weight. In fact, EPDS is usually divided into isolated sections, which need to be sized for the worst-case scenario. Several concepts of EPDS have been investigated, aiming at enabling the power exchange among separate sections, which allows better optimization for power and weight of the whole system. In this paper, an approach based on the widespread use of multi-port power converters for both DC/DC and DC/AC stages is proposed. System integration of these two is proposed as a multiport power conversion system (MPCS), which allows a ring power distribution while galvanic isolation is still maintained, even in fault conditions. Thus, redundancy of MEA is established by no significant weight increase. A machine design analysis shows how the segmented machine could offer superior performance to the traditional one with same weight. Simulation and experimental verifications show the system feasibility in both normal and fault operations

Phasor Estimation for Grid Power Monitoring: Least Square vs. Linear Kalman Filter

International audienc

Control strategies and applications of three-phase direct matrix converters

University of Technology Sydney. Faculty of Engineering and Information Technology.AC-to-AC converters have been widely used in various areas in the real world. In industrial applications, the AC-to-AC power conversion is usually accomplished by indirect converters. In these traditional converters, AC power is firstly converted into DC power by a rectifier, and then the DC power is converted into AC power by an inverter. The rectifier and inverter are usually connected via an intermediate bulky DC-link capacitor. The use of the DC-link capacitor in these converters makes the equipment volume bulky, reduces the lifetime, increases the design complexity and decreases the system efficiency. Therefore, it is of great benefit to remove the bulky DC-link capacitor or propose new converter topologies. A matrix converter (MC) does not require large energy storage elements and it has emerged as a potential solution to AC-to-AC conversion. A three-phase direct MC comprises nine bidirectional semiconductor switches arranged in a 3×3 matrix form to realize the direct AC-to-AC conversion. Thanks to benefits such as bidirectional power flow, compact volume, controllable input power factor and sinusoidal waveform, MCs have attracted research interests and plenty of projects on MC have been reported. MC is also regarded as an all-silicon converter. However, there are some drawbacks associated with MCs and they have very limited industrial applications. These drawbacks include low voltage transfer ratio (VTR), sensitivity to the grid variations and complex modulation. Some MC application areas need more exploration. The work in this thesis is carried out to contribute to possible solutions to some of the above issues by investigating some control strategies and applications of MCs. The main contributions included in this work are summarized as follows: (1) A simple decoupling controller is designed for the MC-based unified power flow controller (UPFC) (MC-UPFC) to regulate the power flow in a transmission system. The controllable regions of the MC-UPFC are also analyzed. A design procedure for the closed-loop controller in the MC-UPFC is presented. (2) A modified PI controller is proposed for the improvement of the steady-state performance by including a current feedforward path. More control flexibility is provided because of the feedforward controller. A PR controller is designed for the MC and this has good performance. (3) A hysteresis current controller is proposed for the MC to drive AC motors. Both fixed-band and sinusoidal-band hysteresis controllers are investigated, and their performance is compared. The hysteresis controller is a very simple and practical controller for the MC. For the MC-based motor drive, a direct torque control (DTC) technique is also investigated. (4) Model predictive control (MPC) is investigated to control the MC. This scheme is used in an MC-based microgrid. In the islanded mode, predictive voltage control is employed to regulate the MC output voltages to supply various loads. An improved VTR is observed. When the microgrid is connected to the utility grid, power flow is the main objective. The performance of the controller is tested under various conditions including input disturbance and different loads. (5) An MC prototype is built to support the research. The prototype hardware includes main circuit, drives, supplies, analog to digital conversion (ADC) conditioning circuits, and sensor board. The algorithm is implemented in Matlab Simulink with C2000 hardware support packages for TI DSP processors. Various experimental tests are carried out to support the proposed strategies

A review of PHIL testing for smart grids—selection guide, classification and online database analysis

The Smart Grid is one of the most important solutions to boost electricity sharing from renewable energy sources. Its implementation adds new functionalities to power systems, which increases the electric grid complexity. To ensure grid stability and security, systems need flexible methods in order to be tested in a safe and economical way. A promising test technique is Power Hardware In-the-Loop (PHIL), which combines the flexibility of Hardware-In-the-Loop (HIL) technique with power exchange. However, the acquisition of PHIL components usually represents a great expense for laboratories and, therefore, the setting up of the experiment involves making hard decisions. This paper provides a complete guideline and useful new tools for laboratories in order to set PHIL facilities up efficiently. First, a PHIL system selection guide is presented, which describes the selection process steps and the main system characteristics needed to perform a PHIL test. Furthermore, a classification proposal containing the desirable information to be obtained from a PHIL test paper for reproducibility purposes is given. Finally, this classification was used to develop a PHIL test online database, which was analysed, and the main gathered information with some use cases and conclusions are shown