الفهرس 
ABSTRACT
Major Power Quality ProblemsOnly 14 pages are availabe for public view
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Abstract
Power Quality (PQ) problem has become very important nowadays, especially when the market focuses on electricity price and regulators are focused only on energy efficiency. Lack of PQ may cause damage and the total cost of using electrical energy can be thus doubled. So efficiency and cost of electricity are considered today almost at the same level. Nonlinear loads, which commonly present in industrial facilities, service facilities, office buildings, and even in our homes, are the source of several PQ issues such as harmonics, reactive power, low power factor (PF), flicker and resonance.
The conventional method to mitigate the harmonics and reactive power compensation is by using passive LC filters but this method has drawbacks like large size, resonance problem and fixed compensation behavior etc., so this solution becomes ineffective. Subsequently, the active power filter (APF) comes into the picture, which has been developed over the years to give promising solution to solve PQ problems by using suitable control algorithms. There are different APF topologies, such as series, shunt and hybrid type. Series APS is used to compensate the voltage harmonics and shunt type for current harmonics.
This thesis aims to design and apply shunt APF with an adaptive hysteresis band current controller for the harmonic suppression, reactive power compensation and PFcorrection to approximately unity PF for two large motor drive systems in an industrial sector in Assiut Cement Company:
• Three phase 203 kW synchronous motor drive ( Alternative Fuel Shredder)
• 630 kW DC motor (DCM) drive (Bypass Fan in production line # 2)
As these adjustable speed drives (ASDs) are nonlinear loads and injecting a huge amount of current harmonics into the power system. The suitable choice to eliminate current harmonics and reactive power is voltage source shunt APF. The instantaneous reactive power (IRP) p-q theory and the synchronous reference frame (SRF) id-iq control method are used for calculating the compensating current to drive the two proposed shunt APFs of the above two case study, respectively.
In this thesis, the site practical measurements needed for complete analysis of the two studied systems are performed using professional PQ analyzers and their associated software programs. The studied systems are modeled and simulated using MATLAB/SIMULINK software. The site practical results have been validated and compared with computer simulations MATLAB/SIMULINK models results. All results are completely consistent. The total harmonic distortion (THD) with respect to % of fundamental in supply current, source voltage has been analyzed.
For each case of the studied systems, the proposed shunt APF operation principle, theoretical analysis, algorithm and simulation results are presented. The digital simulation results prove the feasibility, effectiveness and high compensation performance of the proposed shunt APF systems in terms of fast response, high efficiency and pure sinusoidal waveforms of source voltage and current with unity PF.
The influence of power system parameters on the performance of the two proposed APFs for the 203kW AC drive and the 630kW DC drive have been screened in this study. It has been verified by simulation results that changing the source impedance of the studied systems, has no effect on the performance of the proposed hybrid shunt APFs. So the same APFs are still effective in harmonic elimination and PF correction, in the case of changing power system configuration such as the disconnection or addition of a transformer at the substation.
This thesis presents the configuration of the standalone APFs, when eliminating the shunt passive RC element from the proposed models for the AC drive and the DC drive, respectively. It has been verified from simulation results that, this passive RC element plays an important role in improving the filtering characteristics of the two proposed APFs.
For comparative purpose, this thesis describes and discusses in detail the design and simulation for a standalone shunt passive power filter (PPF) for the 630 kW DCM drive system to improve the PF and reduce the current/voltage distortion. When comparing the performance of the proposed PPF method and the proposed APF method for this 630 kW DCM drive, it can be verified that, APF is more efficient for harmonic suppression and PF improvement. APF also responds very fast under changes in the load conditions, compared to PPF, which designed to certain load conditions
The THD of the source current and voltage after compensation via the combined system (shunt APF and passive RC element) is well below 3%; the harmonic limit imposed by the IEEE519/1992 standard.