Sharif Digital Repository

Increase in the number of non-linear loads has increased harmonic pollution in industries, resulting in lower power factor and more losses. Harmonics may also lead to adverse conditions in cases they match a resonance frequency existing in the system. To alleviate the problems of harmonics, tuned harmonic filters are used. However, design and installation of passive elements in power systems or industries requires special attentions due to the possible resonances that may occur. In this paper, a Tire-Rubber company is analyzed for a filter installation. Harmonic analysis is performed, and site measurements are examined. Cautions to be taken for design consideration are then discussed  

This paper presents an investigation of power quality problems arising from electric arc furnace (EAF) operation, and the required compensating system capabilities. It also proposes a compensation system using a shunt active filter and a series inductor. A shunt active filter compensates for the reactive power and the current harmonics of the highly varying load. Reference signals for the compensation logic are obtained from the instantaneous current vector components on a rotating reference frame. Due to noninteger harmonics on voltages at the point of common coupling, conventional methods for the inverter dc bus voltage regulation fail to perform properly. Hence, a new method is introduced... 

This paper discusses the application of unified power quality conditioner (UPQC) for improving power quality of a system supplying an electric arc furnace (EAF). The UPQC comprises a combined series and shunt active filters sharing a common DC link. It is used to mitigate voltage disturbances and compensate for reactive power, harmonics and interharmonics. A novel control strategy of the UPQC is presented. Since voltages at the point of common coupling (PCC) contain low frequency interharmonics, conventional methods can not be used for extracting voltage reference signals. In the proposed method, voltage references are extracted using active power processing to generate sinusoidal waveforms.... 

This paper presents a shunt active filter control using the instantaneous power theory on a rotating reference frame for power quality improvement in 3-phase 4-wire system. By current space vector mapping on rotating reference frame, three linearly independent components are derived. The defined powers can be controlled by current vector components. The in-phase current vector component to voltage vector is used for compensating oscillatory load active power and controlling dc voltage. Two other components are used to compensate for reactive power and to eliminate neutral current. Advantage of this control strategy is that synchronizing circuit is not required. Simulation results verify... 

This paper addresses a new mixed model for characterizing LPC excitation on a 3-band basis through analyzing harmonic structure of the residual signal. In addition, a sub-frame based analysis is developed for detecting both aperiodic pulses and noisy signals, which plays a major role in reduction of perceptual errors introduced by some certain consonants. Preliminary results show that near natural speech is achieved at 1050 bps, allocated to the excitation parameters, suggesting superiority of the proposed coding scheme to the MELP-2400 coding standard, in the sense of perceptual quality of reconstructed speech  

The leakage current originated from the fluctuations of the common-mode voltage (CMV) is an issue in a transformerless grid-connected photovoltaic (PV) system. In this paper, a modified space vector modulation based on the Fourier transform analysis is proposed to reduce the leakage current in a three-phase quasi-Z-source inverter (qZSI). The CMV harmonic content in a qZSI contains low and high-frequency harmonics which cause safety and EMI problems respectively. By implementing the proposed modulation in a three-phase qZSI, the low-frequency harmonics of the CMV are mainly reduced. The distribution of the high-frequency harmonics is also modified in a way they can be simply filtered.... 

The leakage current originated from the fluctuations of the common-mode voltage (CMV) is an issue in a transformerless grid-connected photovoltaic system. In this paper, a modified space vector modulation based on the Fourier transform analysis is proposed to reduce the leakage current in a three-phase quasi-Z-source inverter (qZSI). The CMV harmonic content in a qZSI contains low-and high-frequency harmonics that cause safety and electromagnetic interference problems, respectively. By implementing the proposed modulation in a three-phase qZSI, the low-frequency harmonics of the CMV are mainly reduced. The distribution of the high-frequency harmonics is also modified in a way they can be... 

This paper offers a new EF-class converter for dynamic wireless power transfer application. The proposed high-frequency converter employs a floating-frequency switching algorithm to control the converter in a continuous frequency range, eliminate the requirement to any additional operational data from the secondary (receiver) side, accelerate the load impedance match while moving, maximize the transferred power rate, reduce charging interval and compensate power transfer tolerances. Moreover, an optimized super elliptical shape coil is designed to cope with lateral misalignment, enhance coil coupling, and increase efficiency. In the proposed converter, (i) soft switching is implemented to... 

A detection technique for extraction of total harmonics, individual harmonics, and reactive current components is introduced and its performance is evaluated. The detection algorithm is then adopted as part of the control system of a single-phase active power filter (APF) to provide the required signals for harmonic filtering and reactive power compensation. Performance of the overall system is evaluated based on digital time-domain simulation studies. The APF control system including the signal processing algorithms are implemented in Matlab/Simulink Fixed-Point Blockset to accommodate bit-length limitation which is a crucial factor in digital implementation. The power system including the...