Modelització i control d'un sistema de generació elèctrica de turbina de vent

Premi al millor Projecte de Fi de Carrera presentat durant el curs 2006-2007 en l'àmbit d'Energies Alternatives que atorga CÀTEDRA ENDESA REDAquest projecte tracta el desenvolupament d'un model dinàmic de simulació d'un sistema de generació de turbina de vent de velocitat variable amb aspes orientables i generador d'inducció doblement alimentat a través d'un convertidor voltage-source back-to-back per tal de simular els transitoris produïts per canvis en el vent i pertorbacions de la xarxa que no són correctament reproduïts pels models simplificats estàtics que se solen emprar en la simulació de parcs eòlics. S'analitza la modelització tenint en compte la dinàmica mecànica i elèctrica i es tracta el disseny del control tant a nivell d'estratègia d'extracció de la màxima potència del vent com a nivell de control del convertidor, posant especial èmfasi en aquesta part amb un estudi detallat del control vectorial de màquines d'inducció doblement alimentades. Finalment, es presenta el resultat de la simulació d'un assaig de sot trifàsic reproduint les condicions d'un assaig real realitzat sobre un aerogenerador del qual es coneixen els paràmetres i es disposa de dades enregistrades durant l'assaig.Award-winnin

Control of doubly fed induction generators under balanced and unbalanced voltage conditions

The present chapter presents a control technique to deal with the control of doubly fed induction generators under different voltage disturbances. Certain current reference values are chosen in the positive and negative sequences so that the torque and theDCvoltage are kept stable during balanced and unbalanced conditions. Both rotor-side and grid-side converters are considered, detailing the control scheme of each converter while considering the effect of the crow-bar protection. The control strategy is validated by means of simulations.Postprint (published version

Design of a linear time-varying model predictive control energy regulator for grid-tied VSCs

This article presents an energy regulator based on a Model Predictive Control (MPC) algorithm for a Voltage Source Converter (VSC). The MPC is formulated to optimise the converter performance according to the weights defined in an objective function that trades off additional features, such as current harmonic distortion, reactive power tracking and DC bus voltage oscillation. Differently from most approaches found in the research literature, the MPC proposed here considers the coupling dynamics between the AC and DC sides of the VSC. This study is focused on the example case of a single-phase VSC, which presents a nonlinear relationship between its AC and DC sides and a sustained double-line frequency power disturbance in its DC bus. To reduce the burden of the MPC, the controller is formulated to benefit from the slow energy dynamics of the system. Thus, the cascaded structure typically used in the control of VSCs is kept and the MPC is set as an energy regulator at a reduced sampling frequency while the current control relies on a fast inner controller. The computational burden of the algorithm is further reduced by using a linear time-varying approximation. The controller is presented in detail and experimental validation showing the performance of the algorithm is provided.Peer ReviewedPostprint (published version

E-bike load demand estimation for transport using cartographic data

In remote areas of Sub-Saharan Africa, as well as in Rwanda, communities face the problem of finding an affordable and suitable way of transport for their daily life. Currently, the short-range transportation of people and goods rely on manual traction (e.g., bicycles, handmade wooden bicycle, etc.) and on small combustion engines. However, this region has a large renewable energy source (solar) which can help to mitigate this problem. Electric bicycles may be used to tackle the problem, although their use is still not largely widespread despite its potential. In addition, the local society does not have an easy way to accurately estimate the amount of energy consumed for a certain itinerary to be sure of how the electric vehicles perform. Thus, characteristic analysis of consumed energy is very important to analyze the performance of electric vehicle storage systems, model charging infrastructure, size vehicles, planning for itineraries, etc. This paper presents a methodology to estimate the power consumed by electric bikes for specific itineraries. In order to accomplish so, the WebPlotDigitizer tool and Google Maps were used to produce driving profile patterns. The results are compared against experimental data, showing the accuracy of the methodology presented. The simulated results show that the consumed power value differs by only 1.68% from the experimental recorded value; the difference can be explained by traffic congestion, the density of traffic, and the intersection that occurred during the experiment. The presented method of driving energy requirement estimation using WebPlotDigitizer is attractive, affordable, and easy to use.This study supported by; University of Rwanda (UR_CST) African Center for Excellence Energy for Sustainable Development, Mechanical and Energy Engineering Department.Peer ReviewedPostprint (published version

MVDC network balancing for increased penetration of low carbon technologies

This paper outlines the case for using Medium Voltage Direct Current (MVDC) (5-50 kV) elements in distribution systems as a means to accelerate the deployment of low carbon technologies. The approach uses existing cable and overhead assets, originally designed into the ac system for security purposes. By selective conversion to dc, an inter GSP (grid supply point) balancing network can be created with modifications only required at substations. This approach allows for increased network transfer capability without increasing fault level as would be the case with conventional interconnection. Using data from a real-world Scottish suburban distribution network, the benefits and barriers to such an approach are examined. Power flows for the existing network are benchmarked under various present day and future loading scenarios. Controllable MVDC links are introduced to the network and power flow studies used to assess the value of such an approach to network reinforcement. Cost estimates for such a scheme are projected using data from industrial trials

Sizing requirements of the photovoltaic charging station for small electrical vehicles

Electric vehicles (EVs) are being introduced in Rwanda and becoming attractive for different reasons. For instance, these types of vehicles can help decrease air pollution and noise emissions. In addition, it presents an alternative to combustion engines, given the increased price of fuel resources in Rwanda and around the world. This paper presents a tool tailored to optimize the design of an electrical charging station serving small-sized electric vehicles, utilizing the algorithm to assist in sizing stand-alone mopped charging stations. The developed tool is based on the toolbox EventSim from MathWorks, which permits the combination of the simulation of discrete events (such as the arrival of customers at the station) with continuous states (such as the simulation of the charging process). The required PV power was estimated by utilizing solar resources, for the location, from renewables. Ninja. The number of customers arriving at the existing oil station is normalized to estimate the energy requirements of the mopped fleet. A Poisson distribution was proposed to model the battery discharge upon arrival, and different related parameters were evaluated through a sensitivity analysis to identify their effects on the performance of photovoltaic charging station. For the testing values, the station parameters were changed by ±25% to determine the impact of key design parameters on station performance, as well as other satisfaction measures such as average waiting time and average queue length. With a 25% increase in photovoltaic panels, the blackout period decreases by 2.12%, while a 25% decrease in photovoltaic panels causes an increase of 2.18% in the blackout period. Utilizing the energy management system (EMS), the waiting time was reduced by 8%.Peer ReviewedPostprint (published version

Decentralized control of a nine-phase permanent magnet generator for offshore wind turbines

2nd Place, Best paper award de la revista "IEEE transactions on energy conversion" atorgat per la IEEE Power and Energy SocietyThis paper presents a decentralized current control approach for a nine-phase wind turbine generator. This type of generator has three different three-phase stators sharing the same machine yoke and connected to the grid by means of three different voltage source back-to-back power converters. Due to the machine configuration, magnetic couplings are present between the three stators, complicating the design and implementation of the machine current controllers. Rather than a centralized control approach, this paper proposes a methodology to design a decentralized machine control to regulate the active and reactive power flowing through each stator independently. A complete dynamic analysis is performed in order to design the controller to reduce the coupling effects within the machine, while ensuring a proper dynamic performance. The control strategy is validated through simulation and experimental results.Award-winningPostprint (author's final draft

A new fast-acting backup protection strategy for embedded MVDC links in future distribution networks

This paper presents a new fast-acting backup protection strategy for future hybrid ac-dc distribution networks. By examining the impedance measured by a distance protection relay measuring from the “ac-side” of the network, a unique characteristic is established for faults occurring on the “dc-side” of an embedded medium-voltage dc (MVDC) link, interconnecting two 33 kV distribution network sections. Based on the identified impedance characteristic, appropriate settings are developed and deployed on a verified software model of a commercially available distance protection relay. To remain stable for ac-side faults, it is found that the tripping logic of the device must be altered to provide correct time grading between standard, ac, protection zones and the fast-acting dc region, which can identify faults on the dc system within 40 ms. An additional confirmatory check is also employed to reduce the likelihood of mal-operation. Trials on a test system derived from an actual distribution network, which employs distance protection, are shown to provide stable operation for both ac-side and dc-side pole-pole and pole-pole-ground fault

Real-time optimization-based reference calculation integrated control for MMCs considering converter limitations

© 2021 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksThe paper addresses a real-time optimization-based reference calculation integrated with a control structure for Modular Multilevel Converters (MMC) operating under normal and constrained situations (where it has reached current and/or voltage limitations, e.g. during system faults). The algorithm prioritizes to satisfy the Transmission System Operators (TSO) AC grid current demanded set-points. The constrained optimization problem is formulated based on the steady-state model of the MMC, whereby the prioritization is achieved through distinct weights defined in the Objective Function’s (OF) terms. The resultant optimization problem, however, is highly nonlinear requiring high computation burden to be solved in real-time. To overcome this issue, this paper applies a Linear Time-Varying (LTV) approximation, where the nonlinear dynamics of the system are represented as constant parameters, while a Linear Time-Invariant (LTI) system is used to formulate the optimization constraints. The converter's current references are determined in real-time by solving a constrained linearized optimization problem at each control time step, considering the TSO's demands, the current MMC operating point and its physical limitations. Finally, the linearized-optimization problem is integrated with the MMC controllers and evaluated under different network conditions, where the results indicated that method can be potentially employed to obtain the MMCs current references.Peer ReviewedPostprint (author's final draft

Electromechanical modelling and control of a micro-wind generation system for isolated low power DC micro grids

This paper describes the modelling and control of a micro-wind generation system, based on an axial flux permanent magnet synchronous generator (PMSG), for isolated low power DC micro grids. The system consists of a micro-wind turbine including a furling tail, a PMSG, a three phase diode rectifier and a buck converter connected to a battery bank and a load. Furthermore, it incorporates a control system to extract the maximum power output from the wind turbine using the minimum possible number of sensors. The system is simulated in Matlab/Simulink to analyze the dynamical response and it is compared with the current IT-PE-100.Postprint (published version