Vjetroagregati se obično postavljaju na udaljene, nepristupačne lokacije te je potrebno spriječiti nastanak kvarova da bi se povećala njihova ekonomska konkurentnost. Kvarovi elektromehaničkih ...dijelova generatora vjetroagregata česti su i vrlo skupi. U ovom radu predstavljen je koncept upravljanja vjetroagregatima s promjenjivom brzinom vrtnje i zakretom lopatica za slučaj identificiranog i okarakteriziranog oštećenja kaveza asinkronog generatora. Predložena je nadogradnja na postojeći algoritam upravljanja momentom zasnovana na njegovoj modulaciji s obzirom na položaj magnetskog toka generatora. Da bi se izbjeglo ili usporilo širenje napuknuća kaveza generatora, predložena je primjena regulacijskog kruga za zakret lopatica i u režimu rada vjetroagregata ispod nazivne brzine vrtnje. Predstavljena strategija upravljanja razvijena je uvažavajući mogućnost modularnog nadovezivanja na postojeće metode upravljanja već postavljenih vjetroagregata s ciljem produženja njihova životnog vijeka i povećanja proizvodnje energije. Razmatrani su i uvaženi aspekti vezani uz praktičnu izvedbu, kao što je estimacija varijabli korištenih u upravljačkom algoritmu i pripadajuće pogreške estimata, kao i nesimetrije uzrokovane nastankom kvara. U radu su dani simulacijski rezultati za slučaj vjetroagregata iz megavatne klase s dijagnosticiranim napuknućem kaveza rotora.
Before applying current-signature-analysis-based monitoring methods, it is necessary to thoroughly analyze the existence of the various harmonics on healthy machines. As such an analysis is only done ...in very few papers, the objective of this paper is to make a clear and rigorous characterization and classification of the harmonics present in a healthy cage rotor induction motor spectrum as a starting point for diagnosis. Magnetomotive force space harmonics, slot permeance harmonics, and saturation of main magnetic flux path through the virtual air-gap permeance variation are taken into analytical consideration. General rules are introduced giving a connection between the number of stator slots, rotor bars, and pole pairs and the existence of rotor slot harmonics as well as saturation-related harmonics in the current spectrum. For certain combinations of stator and rotor slots, saturation-related harmonics are shown to be most prominent in motors with a pole pair number of two or more. A comparison of predicted and measured current harmonics is given for several motors with different numbers of pole pairs, stator slots, and rotor bars.
This work is focused on optimization problems within the predictive control framework for determining and engaging
the flexibility of a microgrid in grid-microgrid energy exchange. The microgrid has ...a controllable battery storage
and other components represented with a residual power flow. All major economic constituents of the grid-connected
microgrid operation are considered: day-ahead, intra-day, peak power and battery degradation costs, as well as
rewards and penalties for providing flexibility. The problems are posed as linear worst-case minimization programs
in which all flexibility activation scenarios are taken into account. An analysis is conducted for various combinations
of flexibility reservation and activation prices that can be bid to a grid entity. The technical and economic feasibility
of the flexibility provision is confirmed by the use of an online model predictive controller that optimally meets the
requirements of grid flexibility according to the declared reserve in the environment of online occurring disturbances
and events.
A railway energy management system based on hierarchical coordination of electric traction substation energy flows
and on-route trains energy consumption is presented in the paper. The railway system ...is divided into energy-efficient
individual trains energy consumption management as a lower level, and the energy-cost-efficient electric traction
substation energy flows management as a higher level. The levels are coordinated through parametric hierarchical
model predictive control with the main goal of additionally decreasing the operational costs of the overall system.
Through interactions with the power grid at the higher level, the system can provide ancillary services and respond
to various grid requests. At the same time, lower level trains driving profiles are adjusted to attain the minimum
cost of system operation with timetables and on-route constraints respected. The developed algorithm is verified
against a detailed real case study scenario with the presented results showing significant cost and energy consumption
reductions
In an era where cities are growing at an unprecedented pace and facing an array of challenges, from increasing population densities to aging infrastructure, it has become imperative to leverage ...advanced technology to ensure efficient and sustainable urban development. The work in this paper is focused on enabling and improving the monitoring of city infrastructure based on variables trends, setting alarm limit values and developing various predictive maintenance diagnostic algorithms. Based on the collected data, an information interface is developed for communication with the operator of the lighting system, which includes visualizations of various indicators such as the density of road and pedestrian traffic, weather conditions in different locations, lighting level, electricity consumption and identification of the work of individual lighting poles.
Lighting is among the largest electricity consumers in cities. It is also one of the most outdated infrastructures. Dimmable LED lamps introduced remote control capability and a potential to adjust ...the lighting based on real on-site demand. The paper presents an embedded controller with the corresponding software layer to transform a LED lamp into actively dimmable, smart sensor and network node of the city lighting system. The software layer utilizes model predictive control that exploits light propagation model and disturbance forecasting, to provide optimal horizontal and vertical lighting quality, adjusting to micro-location conditions in real-time. Explicit implementation with look-up tables enable simple implementation and fast execution.
This paper is focused on improvement of energy- and cost-efficiency of an electric railway traction system with respect to electricity supply conditions, routes conditions, timetable requirements and ...overall system constraints. This is attained by coordination of electric traction substation energy flows management and on-route trains energy consumption to facilitate the integration of railways into smart electricity grids. Optimization of energy flows in the electric traction substation with respect to the grid-supplied electricity price profile is coordinated with multiple trains on-route power consumption. The coordination optimizes traction profiles directly to improve the electricity cost while all physical and on-route constraints are kept. For validation purposes, extensive simulation scenarios are conducted confirming significant energy saving and cost reduction potential of the presented coordination in different railway system operation set-ups including volatile price tariffs, different energy storage systems, different number of trains in the substation supply area and grid conditions.
In high voltage induction machines the stator slots usually are wide opened to facilitate the assembling of the stator winding coils. Thus the magnetically effective air gap and higher order ...harmonics are rising, the power factor is decreasing. To compensate this negative effect magnetic stator slot wedges are frequently applied. During operation these slot wedges can get loose and eventually fall out totally. Currently a detection of fallen out slot wedges is only possible by time consuming partially disassembling the machine and optical inspection. Simple and reliable testing methods can thus increase the reliability and reduce costs due to unnecessary disassembling of the machine. For such testing methods high frequency or transient electrical properties of an electrical machine suit very well as the base. When high frequency or transient voltage signals are applied to the terminals of the machine the resulting current response contains information about the machine's magnetic state. Therein superposed are the magnetic material properties, several inherent asymmetries such as spatial saturation or slotting, as well as fault induced asymmetries. This paper introduces a new signal processing chain to detect and isolate the fault induced asymmetries caused by fallen out stator slot wedges. The chain consists of data capturing by collecting current response values due to voltage pulses and following Fast Fourier transformations. Measurements for several slot wedge fault cases are presented. The measured and calculated results show the high sensitivity and reliability of the proposed method.
Prikazan je povijesni tijek razvoja i sadašnji trenutak Laboratorija za sustave obnovljivih izvora energije (LARES) na FERu. Laboratorij je nastao adresiranjem tehničkih izazova povezanih s ...upravljanjem pojedinačnih sustava obnovljivih izvora energije, sustava pohrane ili potrošača, s ciljevima njihove ekonomičnosti i dugovječnosti, a danas se mahom bavi upravljanjem njihovih složeno povezanih kombinacija, na razini zgrada i infrastrukture. Glavna metodološka odrednica LARESa su matematička optimizacija i prediktivno upravljanje.
In this paper we successfully experimentally verify the recently introduced protective predictive controller patch for multi-mass drives subject to physical and safety constraints on their variables. ...The protective patch is obtained through set-theoretic computations that account for the drive model and constraints, as well as the state estimation uncertainties. It is used in combination with the classical LQR controller. The easy implementation of the patch online allows the correction of the LQR control signal in order to suppress the violation of drive constraints and thus avoid possibly dangerous and/or drive-harmful situations during the transients.
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