Power Quality analysis in Renewable Energy Systems Supplying Distribution Grids (original) (raw)
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Power Quality Assessment in Small Scale Renewable Energy Sources Supplying Distribution Systems
Energies, 2013
The impact of wind turbines and photovoltaic systems on network operation and power quality (harmonics, and voltage fluctuations) is very important. The capability of the power system to absorb this perturbation is dependent on the fault level at the point of common coupling. The paper deals with power quality case studies conducted on existing renewable resources-based systems. Voltage fluctuations determined by a 0.65 MVA wind turbine are analyzed. The impact of photovoltaic systems on steady state voltage variations and current harmonics is investigated. The correlation between the generated power and the main power quality indices is highlighted.
Power Quality Analysis of Electrical Distribution Systems with Renewable Energy Sources
2018
Renewable energy sources are promising solutions to cater the energy demand. In this context, research works have been reported by focusing on various aspects of renewable energy sources, for their successful integration into the Electrical Distribution Systems (EDS). Among various renewable energy sources, wind and solar photovoltaic (SPV) units have assumed more prominence. However, in such systems, Power Quality (PQ) problems are encountered during the operation of a EDS. Such problems in a wind unit are mainly due to the rapid output power variations (flicker) from wind turbines. The reasons for flicker are variations of wind speed, wind gust, wind turbulence, tower shadow and wind shear. Further, PQ problems are also probable in EDS with SPV, mainly with a fluctuating cloud affecting irradiation and hence the generation of power. In this context, studies on EDS with Distributed Generation are presented from Power Quality perspective. Suitable Power Quality Indices (PQIs) based ...
Power Quality Analysis Of A System Based On Renewable Energy Supplying A Local Distribution Network
Acta Flectrotehnica, 2008
This paper deals with the quality analysis of an electrical local network supplied with energy provided by renewable resources. The presence on a large scale of renewable energy resources brought some issues concerning generally the electromagnetic compatibility and particularly the quality of energy regarding the harmonic pollution. Modelling and analysis of the electric energy quality in the proposed system is conducted by programs developed in Matlab/Simulink environment.
pvtechnology.ucy.ac.cy
The growing integration of renewable energy sources and more specifically of photovoltaic (PV) technologies has intensified the conviction to identify the effects arising when connecting such energy sources to the grid. A growing research interest exists and focuses on the effects of the harmonics that are produced from PV grid connected systems. Consequently, the quality of produced electrical power must fall within certain limits for voltage and current disturbances in order to avoid undesirable effects in power distribution networks. Power quality research related activities are therefore necessary in order to avoid possible complaints and undesirable economic consequences in the future. In this work, the power quality response of distribution grids with PV systems under different solar irradiation conditions and with various concentrations of such systems is investigated and the results are presented.
Impacts of Renewable Sources on Power Quality in Distribution Systems
Renewable Energy and Power Quality Journal, 2004
This paper analyzes the influence of renewable sources (RS) on voltage quality in MV networks and summarizes problems considered of general interest relating to the power quality of dispersed generation. We are interested in voltage fluctuations, flicker, harmonic distortion, interharmonic distortion, and the effect of dispersed generation on ripple control signals. The influence of DG on voltage stabilization, line losses, and short circuit impedance are also investigated. A basic analysis of the possibility and effectiveness of using a parallel Active Filter (AF) to compensate for the constant-speed wind turbine (WT) flicker, reactive power, and terminal voltage variation is presented too.
Power Quality in Grid-Connected Wind Turbines
Wind Turbines, 2011
Electric power is a very unusual product. It must be constantly available for the customers but its massive storage is not possible. Therefore, electric power needs to be generated as it is used. Furthermore, it is usually generated far from the customers. All these factors make it difficult to control and assure the quality of electric power. There is no procedure that allows the removal of the poor electric power. Consequently, it is necessary to define preventive and monitoring procedures that guarantee a minimum level of power quality and hence the correct behavior of the equipment connected to the power distribution system. Perfect power quality means that the voltage is continuous and sinusoidal with a constant amplitude and frequency. Low-frequency conducted disturbances are the main defects that could compromise power quality. These are classified in the following groups: harmonics and interharmonics, voltage dips and short supply interruptions, voltage unbalance, power frequency variations and voltage fluctuations or flicker. In the last years the use of wind farms and other distributed power generation systems has drastically increased. The question that needs to be raised is how those new generation systems will affect to the whole grid. A portion of the answer must be obtained from the impact that they have on the power quality. In principle, wind energy can be considered a risky source in terms of power quality. Moreover, when wind turbines are part of the grid the power, quality seems to be a complex issue which highly depends on the interaction between the grid and the wind turbines. The main impact on the grid by the wind turbines, concerning power quality, is related to voltage changes and fluctuations, harmonic content, power peaks and flicker. The presence of these disturbances is determined by meteorological conditions and by the technical features of the wind turbine: continuously variable output power due to wind shear, tower shadow or turbulences; performance of electrical components such as generators and transformers; aerodynamic and mechanical behavior of the rotor.. . The power quality of the wind turbines must be certified on the basis of measurements performed according to international standards and guidelines. On one hand, the IEC 61400-21 standard is the reference normative for the certification of the power quality of wind turbines (IEC-61400-21 Ed. 2.0, 2008). The first edition was published in 2001 and it specifies the main relevant features of power quality that should be measured in a wind turbine. This standard establishes the procedures for the measurement and assessment of power quality characteristics of grid-connected wind turbines. According to it, measurements should be performed for harmonic content, flicker, voltage drops as well as active and reactive power, during normal and switching operations. To obtain those characteristics, the measurements should be made on the basis of long time-series of current and voltage, always depending on 24 www.intechopen.com 2.1 Current harmonics, interharmonics and higher frequency components Voltage and current harmonics are usually present on the utility network. Non-linear and electronic loads, rectifiers and inverters, are some sources which produce harmonic content. The effects of the harmonics include overheating, faulty operation of protections, equipment failures or interferences with communication systems. The standard specifically defines different procedures to assess the harmonics, interharmonics and higher frequency components for a wind turbine working under continuous conditions and operating with reactive power as close as possible to zero. This means that, if applicable, 548
Assessment of power quality in the utility grid integrated with wind energy generation
IET Power Electronics, 2020
The ever increasing wind energy penetration into the utility grid causes challenges in the power quality (PQ) of the electrical supply. Therefore, this work proposed PQ assessment in the utility grid which is interfaced with the wind energy generation using Stockwell's transform (ST) under various operating events. The experimental setup for assessing the PQ included an emulated wind generator synchronised with the utility grid at the point of common coupling. The current and voltage measurements are carried out using PQ analyser associated with WTViewer application software. The recorded signals of the voltage waveforms are assessed using ST to detect the various PQ issues related to the grid integration and wind generator's outage. To investigate the effects of various types of loads on the PQ, the same events are carried out. Various PQ disturbances are successfully detected using the proposed algorithm. Performance of the proposed algorithm is also tested on the grid integrated solar photovoltaic (PV) system to investigate and compare the PQ disturbances associated with the grid integrated solar PV system.
IET Renewable Power Generation, 2015
Renewable energy sources are expected to have a considerable share in the global energy mix over the next years and consequently further research is required to enhance the planning strategies, modify prudently the existing standards and set quality levels on delivered power in order to accommodate the penetration of these technologies. Depending on the distribution grid dynamics and the load demand, the amplitude of voltage may vary significantly, and therefore proper simulation models are required for performing dedicated studies. In this study, a simplified and accurate model representing the distribution grid dynamics is introduced for power quality studies in the presence of distributed photovoltaic (PV) generators. The proposed simplified distribution grid model (SDGM) is validated using measurements and it is then used along with a verified PV system model to estimate the voltage variation and PV capacity of the distribution grid under investigation. Moreover, a sensitivity analysis is performed by varying the parameters of the SDGM to assess how the PV capacity is altered. As a last step, common voltage regulation schemes are analysed through the use of the proposed model, validating operational modes that can accommodate high distributed PV capacities.
The introduction of an increasing density of renewable energy sources (RES) in the distribution network is an issue of major concern as this can give rise to power quality problems if appropriate proactive actions are not taken. It is expected that in the not so distant future, utilities will have to deal with higher densities of PV systems in distribution networks, especially in regions with high solar irradiance and further investigation is necessary to understand the behaviour of the distribution network in the presence of such power sources. The environmental factors and in particular the fluctuation in solar irradiance can lead to variations in power and supply quality and hence the electricity network has to adapt in such a way to absorb any kind of harmful disturbances. It is clear that the future electricity grids will have to undergo significant changes to accommodate the increased penetration of RES and the behaviour of these sources in the network has to be well understood. As a result and in order to gain the ability to predict the harmonic pollution due to PV generation, a simple harmonic model for the grid has been adopted and analyzed. Then a typical distribution system topology has been modelled and the findings of the measurements on PV systems have been applied to the distribution system model. On that basis the solar irradiance dependent level of harmonic distortion due to PV generation has been assessed. The extracted results have been compared with already existing standards in an attempt to evaluate the validity of the use of power quality (PQ) standards in modern distribution systems.