13,706 research outputs found
Power quality and electromagnetic compatibility: special report, session 2
The scope of Session 2 (S2) has been defined as follows by the Session Advisory Group and the Technical Committee: Power Quality (PQ), with the more general concept of electromagnetic compatibility (EMC) and with some related safety problems in electricity distribution systems.
Special focus is put on voltage continuity (supply reliability, problem of outages) and voltage quality (voltage level, flicker, unbalance, harmonics). This session will also look at electromagnetic compatibility (mains frequency to 150 kHz), electromagnetic interferences and electric and magnetic fields issues. Also addressed in this session are electrical safety and immunity concerns (lightning issues, step, touch and transferred voltages).
The aim of this special report is to present a synthesis of the present concerns in PQ&EMC, based on all selected papers of session 2 and related papers from other sessions, (152 papers in total). The report is divided in the following 4 blocks:
Block 1: Electric and Magnetic Fields, EMC, Earthing systems
Block 2: Harmonics
Block 3: Voltage Variation
Block 4: Power Quality Monitoring
Two Round Tables will be organised:
- Power quality and EMC in the Future Grid (CIGRE/CIRED WG C4.24, RT 13)
- Reliability Benchmarking - why we should do it? What should be done in future? (RT 15
European White Book on Real-Time Power Hardware in the Loop Testing : DERlab Report No. R- 005.0
The European White Book on Real-Time-Powerhardware-in-the-Loop testing is intended to serve as a reference document on the future of testing of electrical power equipment, with speciïŹ c focus on the emerging hardware-in-the-loop activities and application thereof within testing facilities and procedures. It will provide an outlook of how this powerful tool can be utilised to support the development, testing and validation of speciïŹ cally DER equipment. It aims to report on international experience gained thus far and provides case studies on developments and speciïŹ c technical issues, such as the hardware/software interface. This white book compliments the already existing series of DERlab European white books, covering topics such as grid-inverters and grid-connected storag
Effects of energy storage systems grid code requirements on interface protection performances in low voltage networks
The ever-growing penetration of local generation in distribution networks and the large diffusion of energy storage systems (ESSs) foreseen in the near future are bound to affect the effectiveness of interface protection systems (IPSs), with negative impact on the safety of medium voltage (MV) and low voltage (LV) systems. With the scope of preserving the main network stability, international and national grid connection codes have been updated recently. Consequently, distributed generators (DGs) and storage units are increasingly called to provide stabilizing functions according to local voltage and frequency. This can be achieved by suitably controlling the electronic power converters interfacing small-scale generators and storage units to the network. The paper focuses on the regulating functions required to storage units by grid codes currently in force in the European area. Indeed, even if such regulating actions would enable local units in participating to network stability under normal steady-state operating conditions,
it is shown through dynamic simulations that they may increase the risk of unintentional islanding occurrence. This means that dangerous operating conditions may arise in LV networks in case dispersed generators and storage systems are present, even if all the end-users are compliant with currently applied connection standards
Small-Signal Modelling and Analysis of Doubly-Fed Induction Generators in Wind Power Applications
The worldwide demand for more diverse and greener energy supply has had a significant
impact on the development of wind energy in the last decades. From 2 GW in 1990,
the global installed capacity has now reached about 100 GW and is estimated to grow to
1000 GW by 2025. As wind power penetration increases, it is important to investigate its
effect on the power system. Among the various technologies available for wind energy
conversion, the doubly-fed induction generator (DFIG) is one of the preferred solutions
because it offers the advantages of reduced mechanical stress and optimised power capture
thanks to variable speed operation. This work presents the small-signal modelling and
analysis of the DFIG for power system stability studies.
This thesis starts by reviewing the mathematical models of wind turbines with DFIG
convenient for power system studies. Different approaches proposed in the literature for
the modelling of the turbine, drive-train, generator, rotor converter and external power
system are discussed. It is shown that the flexibility of the drive train should be represented
by a two-mass model in the presence of a gearbox.
In the analysis part, the steady-state behaviour of the DFIG is examined. Comparison
is made with the conventional synchronous generators (SG) and squirrel-cage induction
generators to highlight the differences between the machines. The initialisation of the
DFIG dynamic variables and other operating quantities is then discussed. Various methods
are briefly reviewed and a step-by-step procedure is suggested to avoid the iterative
computations in initial condition mentioned in the literature.
The dynamical behaviour of the DFIG is studied with eigenvalue analysis. Modal
analysis is performed for both open-loop and closed-loop situations. The effect of parameters
and operating point variations on small signal stability is observed. For the
open-loop DFIG, conditions on machine parameters are obtained to ensure stability of
the system. For the closed-loop DFIG, it is shown that the generator electrical transients
may be neglected once the converter controls are properly tuned. A tuning procedure is
proposed and conditions on proportional gains are obtained for stable electrical dynamics. Finally, small-signal analysis of a multi-machine system with both SG and DFIG is
performed. It is shown that there is no common mode to the two types of generators.
The result confirms that the DFIG does not introduce negative damping to the system,
however it is also shown that the overall effect of the DFIG on the power system stability
depends on several structural factors and a general statement as to whether it improves or
detriorates the oscillatory stability of a system can not be made
Data Acquisition and Control System of Hydroelectric Power Plant Using Internet Techniques
VodnĂ energie se nynĂ stala nejlepĆĄĂm zdrojem elektrickĂ© energie na zemi. VyrĂĄbĂ se pomocĂ energie poskytovanĂ© pohybem nebo pĂĄdem vody. Historie dokazuje, ĆŸe nĂĄklady na tuto elektrickou energii zĆŻstĂĄvajĂ konstantnĂ v prĆŻbÄhu celĂ©ho roku. Vzhledem k mnoha vĂœhodĂĄm, vÄtĆĄina zemĂ nynĂ vyuĆŸĂvĂĄ vodnĂ energie jako hlavnĂ zdroj pro vĂœrobu elektrickĂ© energie.NejdĆŻleĆŸitÄjĆĄĂ vĂœhodou je, ĆŸe vodnĂ energie je zelenĂĄ energie, coĆŸ znamenĂĄ, ĆŸe ĆŸĂĄdnĂ© vzduĆĄnĂ© nebo vodnĂ zneÄiĆĄĆ„ujĂcĂ lĂĄtky nejsou vyrĂĄbÄny, takĂ© ĆŸĂĄdnĂ© sklenĂkovĂ© plyny jako oxid uhliÄitĂœ nejsou vyrĂĄbÄny, coĆŸ ÄinĂ tento zdroj energie ĆĄetrnĂœ k ĆŸivotnĂmu prostĆedĂ. A tak brĂĄnĂ nebezpeÄĂ globĂĄlnĂho oteplovĂĄnĂ. PouĆŸitĂ internetovĂ© techniky k ovladĂĄnĂ nÄkolika vodnĂch elektrĂĄren mĂĄ velmi vĂœznamnĂ© vĂœhody, jako snĂĆŸenĂ provoznĂch nĂĄkladĆŻ a flexibilitu uspokojenĂ zmÄny poptĂĄvky po energii na stranÄ spotĆeby. TakĂ© velmi efektivnÄ ÄelĂ velkĂœm naruĆĄenĂm elektrickĂ© sĂtÄ, jako je napĆĂklad pĆidĂĄnĂ nebo odebrĂĄnĂ velkĂ© zĂĄtÄĆŸe, a poruch. Na druhou stranu, systĂ©m zĂskĂĄvĂĄnĂ dat poskytuje velmi uĆŸiteÄnĂ© informace pro typickĂ© i vÄdeckĂ© analĂœzy, jako jsou ekonomickĂ© nĂĄklady, predikce poruchy systĂ©mĆŻ, predikce poptĂĄvky, plĂĄny ĂșdrĆŸby, systĂ©mĆŻ pro podporu rozhodovĂĄnĂ a mnoho dalĆĄĂch vĂœhod. Tato prĂĄce popisuje vĆĄeobecnĂœ model, kterĂœ mĆŻĆŸe bĂœt pouĆŸit k simulaci pro sbÄr dat a kontrolnĂ systĂ©my pro vodnĂ elektrĂĄrny v prostĆedĂ Matlab / Simulink a TrueTime Simulink knihovnu. UvaĆŸovanĂĄ elektrĂĄrna sestĂĄvĂĄ z vodnĂ turbĂny pĆipojenĂ© k synchronnĂmu generĂĄtoru s budicĂ soustavou, generĂĄtor je pĆipojen k veĆejnĂ© elektrickĂ© sĂti. SimulacĂ vodnĂ turbĂny a synchronnĂho generĂĄtoru lze provĂ©st pomocĂ rĆŻznĂœch simulaÄnĂch nĂĄstrojĆŻ. V tĂ©to prĂĄci je upĆednostĆovĂĄn SIMULINK / MATLAB pĆed jinĂœmi nĂĄstroji k modelovĂĄnĂ dynamik vodnĂ turbĂny a synchronnĂho stroje. Program s prostĆedĂm MATLAB SIMULINK vyuĆŸĂvĂĄ k ĆeĆĄenĂ schematickĂœ model vodnĂ elektrĂĄrny sestavenĂœ ze zĂĄkladnĂch funkÄnĂch blokĆŻ. Tento pĆĂstup je pedagogicky lepĆĄĂ neĆŸ komplikovanĂ© kĂłdy jinĂœch softwarovĂœch programĆŻ. Knihovna programu Simulink obsahuje funkÄnĂ bloky, kterĂ© mohou bĂœt spojovĂĄny, upravovĂĄny a modelovĂĄny. K vytvoĆenĂ a simulovĂĄnĂ internetovĂœch a Real Time systĂ©mĆŻ je moĆŸnĂ© pouĆŸĂt budâ knihovnu simulinku Real-Time nebo TRUETIME, v prĂĄci byla pouĆŸita knihovna TRUETIME.Hydropower has now become the best source of electricity on earth. It is produced due to the energy provided by moving or falling water. History proves that the cost of this electricity remains constant over the year. Because of the many advantages, most of the countries now have hydropower as the source of major electricity producer. The most important advantage of hydropower is that it is green energy, which mean that no air or water pollutants are produced, also no greenhouse gases like carbon dioxide are produced which makes this source of energy environment-friendly. It prevents us from the danger of global warming. Using internet techniques to control several hydroelectric plants has very important advantages, as reducing operating costs and the flexibility of meeting changes of energy demand occurred in consumption side. Also it is very effective to confront large disturbances of electrical grid, such as adding or removing large loads, and faults. In the other hand, data acquisition systems provides very useful information for both typical and scientific analysis, such as economical costs reducing, fault prediction systems, demand prediction, maintenance schedules, decision support systems and many other benefits. This thesis describes a generalized model which can be used to simulate a data acquisition and control system of hydroelectric power plant using MATLAB/SIMULINK and TrueTime simulink library. The plant considered consists of hydro turbine connected to synchronous generator with excitation system, and the generator is connected to public grid. Simulation of hydro turbine and synchronous generator can be done using various simulation tools, In this work, SIMULINK/MATLAB is favored over other tools in modeling the dynamics of a hydro turbine and synchronous machine. The SIMULINK program in MATLAB is used to obtain a schematic model of the hydro plant by means of basic function blocks. This approach is pedagogically better than using a compilation of program code as in other software programs .The library of SIMULINK software programs includes function blocks which can be linked and edited to model. Either Simulink Real-Time library or TrueTime library can be used to build and simulate internet and real time systems, in this thesis the TrueTime library was used.
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