Wyniki 1-3 spośród 3 dla zapytania: authorDesc:"Sabrije OSMANAJ"

An experimental study of Wind Data of a Wind Farm in Kosovo DOI:10.15199/48.2018.07.05

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We have been harnessing the wind's energy [1, 2] for hundreds of years. From old Holland to farms in the United States, windmills have been used for pumping water or grinding grain. Today, the windmill's modern equivalent - a wind turbine - can use the wind's energy to generate electricity. Wind turbines [3, 4, 5], like windmills, are mounted on a tower to capture the most energy. At 30 meters or more aboveground, they can take advantage of the faster and less turbulent wind. Turbines catch the wind's energy with their propeller-like blades. Usually, two or three blades are mounted on a shaft to form a rotor. A blade acts much like an airplane wing. When the wind blows, a pocket of low-pressure air forms on the downwind side of the blade. The low-pressure air pocket then pulls the blade toward it, causing the rotor to turn. This is called lift. The force of the lift is actually much stronger than the wind's force against the front side of the blade, which is called drag. The combination of lift and drag causes the rotor to spin like a propeller, and the turning shaft spins a generator to make electricity. Wind turbines can be used as stand-alone applications, or they can be connected to a utility power grid [6, 7, 8] or even combined with a photovoltaic (solar cell) system. For utility-scale sources of wind energy, a large number of wind turbines are usually built close together to form a wind plant. Several electricity providers today use wind plants to supply power to their customers. Stand-alone wind turbines are typically used for water pumping or communications. However, homeowners, farmers, and ranchers in windy areas can also use wind turbines as a way to cut their electric bills. Small wind systems also have potential as distributed energy resources. Distributed energy resources refer to a variety of small, modular power-generating technologies that can be combined to improve the operation of the electricity deli[...]

An experimental study for the islanding detection by the harmonic distortion method and protection system of the inverter DOI:10.15199/48.2019.04.44

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The problem of islanding of photovoltaic systems interconnected with utility grid has been the main challenge in implementing distributed generation of electricity. Islanding is a condition in which a portion of the utility system, which contains both load and operating generation. The distributed generation of electricity is an option that is being considered seriously around the world, especially in countries where the centralized power generation system is very old and causes large environmental pollution. Distributed generation, as defined by Karlsson is “…an electrical power generation source connected directly to the distribution grid or on the customer side of the meter". One of the main problems encountered in distributed generation is the possible formation of isolation conditions (areas called the island) that can continue to work normally even if the electrical grid is disconnected. For applications without detection and correction, it is better to combine more methods for detection of islanding detection based on other work processes [1, 2]. This unity power factor condition combined with passive parameters of parallel RLC load and frequency is considered the worst case for islanding detection when the active power of load matches to the output power of distributed generation [3, 4]. Is describes an anti-islanding control technique for use in utilityinterconnected photovoltaic systems. The technique can be used to prevent islanding in any distributed generation resource that uses a static inverter as the interface device [5]. The ability to protect from the creation of islanding circumstances is an important request for distributed generation. It is necessary to detect when the system works under insulation conditions and disconnect from the network as soon as possible [6]. Detecting the islanding is important for all DG systems. In the last decade, many algorithms have been developed for such detect[...]

An experimental study of passive methods for islanding detection and protection system of the inverter operation DOI:10.15199/48.2018.02.28

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The distributed generation of electricity is an option that is being considered seriously around the world, especially in countries where the centralized power generation system is very old and causes large environmental pollution. Distributed generation, as defined by Karlsson [1] is “…an electrical power generation source connected directly to the distribution grid or on the customer side of the meter". One of the main problems encountered in distributed generation is the possible formation of isolation conditions (areas called the island) that can continue to work normally even if the electrical grid is disconnected [2]. For applications without detection and correction, it is better to combine more methods for detection of islanding detection based on other work processes [3]. The distribution generation is considered to be in unity power factor operation [4]. This unity power factor condition combined with passive parameters of parallel RLC load and frequency, as given in (1)-(4), is considered the worst case for islanding detection when the active power of load matches to output power of distribution generation. 1. The power generated by DG should match the RLC load power, DP = 0 and DQ = 0. 2. A resonant frequency of the RLC load is the same as grid line frequency (f = 50Hz). 3. The quality factor Qf of RLC load is set to be 2.5. The quality factor is defined as that the reactive power stored in L or C is at times the active power consumed in R. Load definition can be represented as (1) 1 2 f  LC  (2) V 2 R P  (3) 2 2 f L V  fQ P  (4) 2 2 f Q P C  fV  where: R - effective load resistance [W], L - effective load inductance [H], C - effective load capacitance [F], P - active power [W], Qf - quality factor, f - grid frequency [Hz]. The values of frequency and magnitude of the voltage at the point of common coupling (PCC) after grid d[...]

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