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EPQU Journal Volume 14 Issue 2
EPQU Journal - Volume 14 Issue 2
By HDK / Published on Wed, 2009-05-27 08:20
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By HDK / Published on Wed, 2009-05-27 08:10
The development of photovoltaic (PV) panels has made solar-powered pumps a reality. The pump drivers are usually direct-current (DC) motors, which are fed by power electronic converters with maximum power point tracking (MPPT) to extract the whole energy that the PV panels can generate, depending on environmental conditions including irradiation and temperature. The implementation of the MPPT algorithm essentially involves sensing both an input current and an input voltage. Understandably, such realisation is expensive.
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By HDK / Published on Wed, 2009-05-27 08:03
Ferroresonance is a phenomenon usually initiated by transients in power networks resulting from, for example, switching operations or ground faults. Non linear behavior of the core of an inductive voltage transformer results in magnetic saturation. Long-lasting ferroresonant states are dangerous to equipment due to prolonged overvoltage and large overcurrents in HV windings. In the present article, numerical simulations of the ferroresonance phenomenon in a HV inductive VT are presented.
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By HDK / Published on Wed, 2009-05-27 07:57
A hybrid parallel active filter / off-line uninterruptible power supply (UPS) system is proposed here. The hybrid system contains a single inverter, which acts as a parallel active filter during the normal mode of operation (when the AC supply is available) and also supplies the load with energy from the UPS back-up battery during the back-up mode of operation (when the AC supply is not available, or is beyond the preset tolerance). In both modes of operation, the inverter is controlled in such a way that the line current is a pure sinusoid.
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By HDK / Published on Wed, 2009-05-27 07:55
Power Quality, in terms of power factor and harmonics, is greatly hampered by a three-phase rectifier used as a front-end ac-to-dc converter in many systems including a UPS. This paper presents the high power factor operation of the converter with reduced total harmonic distortion up to 4%.
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Recently, electricity consumers have shown increasing concern for power quality. Indeed, power quality standards have become higher than before for certain customers due to sensitivity of automation devices. In addition, power quality is affected by the deregulation of power markets in Turkey.
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By HDK / Published on Wed, 2009-05-27 07:49
This paper presents a method of estimating the conducted electromagnetic interference EMI emissions in soft switching inverters.
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By HDK / Published on Wed, 2009-05-27 07:45
In this paper, the method of selecting dv/dt for EMI current ringing attenuation is presented. The mechanism for attenuation is first identified using the theoretical approach. It is shown that the attenuation occurs for rise time of the voltage equal to the inverse of the frequency of current ringing. The concept has been experimentally verified in DC chopper and frequency converter arrangements.
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By HDK / Published on Wed, 2009-05-27 07:42
This paper presents an algorithm for the detection of a complex envelope of power grid signals. The algorithm is based on a Hilbert transform. It was prepared for an analysis of low-frequency disturbances, but can also be used as a compex envelope source for other applications. An implementation of the algorithm in a digital signal processor was made to prove an ability of a real-time operation. Analyses with various numerical representations and input signal quantisation were done. Execution times on a DSP were measured.
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By HDK / Published on Wed, 2009-05-27 07:38
Phase disturbances in electric power signals are neglected and only amplitude (envelope) distortions are discussed in literature. Amplitude disturbances are interpreted as Amplitude Modulation (AM) of the main 50 Hz frequency. Detailed analyses of all disturbances and their sources are presented in this paper. It is shown that AM and narrow band PM (phase modulation) take place in power networks simultaneously, and those two modulations interact with each other. Voltage variation is proposed for disturbance measurement.
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By HDK / Published on Wed, 2009-05-27 07:34
This brief communication addresses the case of a dc nonlinear load supplied with a perfectly constant instantaneous power. A careful analysis shows that this condition does not provide optimum transfer of electric energy.
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