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The answer to global problems challenging energy sector was to use more efficiently local alternative (non-conventional fossil fuel or renewable) energy resources. In power systems, the use of renewable energy (RE) based distributed generation (DG) has increased considerably all over the world; the presence of DG units at distribution voltage level determines the transition from traditional passive...
The trend of generating power at distribution voltage level, known as distributed generation, is thought to be the future of energy generation, as it is environmental friendly and brings many advantages especially for electricity consumers. The paper presents the study of a real Romanian weak distribution network; the microgrid, comprising a transformer and the associated feeders, supplies single-...
The paper tackles an issue that concerns both the suppliers and consumers of electric energy: power losses in distribution power networks. On the other hand, the harmonic pollution in power networks has become a permanent issue, and in many situations along with the unbalance determines a steady state that is unbalanced and non-sinusoidal. In the design and exploitation stage the power engineers calculate...
Modeling of electrical networks elements (electric lines and transformers) during steady state operation is based on the following suppositions: a) supply voltage system is balanced; b) currents are sinusoidal and form a balanced system of phasors; c) network parameters are constant; d) running state is permanent and stationary. These hypotheses can be correctly applied for single-phase and positive...
Interharmonics represent those electrical signals whose frequencies are not integer multiples of the supply fundamental frequency. They correspond to electrical components that are not synchronized with the systems fundamental frequency; due to this fact, they have a more destructive impact than harmonics on the elements of the power system. International organizations like IEC and IEEE International...
This paper deals with the use of a set of indicators defined within a symmetrical component-based framework to study the characteristics of the Steinmetz compensation circuit in the presence of waveform distortion. The Steinmetz circuit is applied to obtain balanced currents in a three-phase system supplying a single-phase load. The circuit is analyzed without and with harmonic distortion of the supply...
The paper presents a new technique to mitigate the voltage unbalance in LV distribution grids using distributed generation (DG). Usually, public LV networks supply many single phase consumers; in this case, the unbalanced line currents produce the unbalance of standard symmetrical supply voltage system. This voltage system negatively influences other three-phase loads operating in the same system,...
Daylighting has become a more important feature of recent constructions due to the sustainable design movement, and suitable lighting controls provide building operators with the means to manage the way lighting energy is used in buildings more efficiently. Unfortunately, classic control systems, based on continuous dimming present some difficulties to adjust their performances to the rapid changes...
Analyse of harmonic distortion in power systems consists in the determination of steady state quantities for each harmonic component at a time. The existing theoretical relationships are difficult to be implemented in complex systems containing many elements, in various combinations. In the case of radial power systems operated in sinusoidal conditions, the load flow calculation can be performed using...
The integration of photovoltaic generation systems into power networks can cause both benefits and drawbacks. However, utilities have to control and operate their systems properly, in order to assure the availability and quality power supply to the users. Therefore, utilities should consider technical constraints and existing regulation in order to assess the impact of photovoltaic systems and limit...
Besides industrial or domestic customers, some single-phase distributed generators can impose an unbalanced operation of electrical networks. In the case of balanced power systems operated in radial schemes, the load flow calculation can be performed using a particular method known as the backward/forward sweep. For unbalanced radial electrical networks, we can consider the backward/forward sweep...
Power quality has become an important issue for electric power engineering. Nowadays, the distribution electric networks have unbalanced operating regimes, mainly produced by the great number of single-phase loads. Unbalanced line currents produce unbalanced voltage drops on the three phases of the supply system. Consequently, the voltage system within the supply network will become unbalanced. Voltage...
The growth of distributed generation (DG) which is consumer driven and not centrally planned presents a number of challenges and opportunities specific mainly to low voltage (LV) distributed networks. The growth of DG in order to meet the UK government's environmental targets for 2010 will taken into consideration for example the following LV distribution network constraints: steady-state voltage...
The issue of non-conventional energy sources now is correlated with energy efficiency and clean energy. An application researched by the authors is vibration stress relieving, which consist in vibration of stress reliving piece with electromagnetic or electro-dynamic vibrator to determine frequencies of resonance. Technology is energy efficient and involves a single-phase inverter with variable frequencies,...
For harmonic polluted electrical networks, the load flow calculation consists in the determination of steady state quantities for each harmonic component at a time. On the other hand, the load flow calculation for unbalanced/asymmetrical electric networks consists in the determination of steady state quantities for each phase at a time. The theoretical relationships proposed in literature are complex...
The sustainable development concept has revived the interest for daylighting as any day lit area has very promising energy-saving opportunities; according to some specialists, the potential energy savings can exceed 40%. However, daylight is a dynamic source of lighting, i.e. the illuminance from the sky is not constant, and the variations in daylight can be quite large depending on season, location...
The reconstruction or revitalization of electrical substations provides the possibility to introduce very powerful new switchgears, and as a result, to simplify the substation circuit diagram. Taking into account these tendencies, the authors propose a systematical method for establishing the optimal structure of electrical substations for increasing the operational level of reliability at the lowest...
In the present study, an overview of the capacitor bank energizing transients is presented and the means of harmonic mitigation technique are investigated. Capacitor bank connection is essential due to reactive compensation reasons. Transients produced upon of capacitor bank energizing, reach in harmonics, may be harmful for the capacitor and become an increasing concern for both electric utilities...
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