Improvement of Electrical Grid – Quality Parameters by LC-Filters, at Supplying of Power Electronics Converters
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Date
2018-03-22
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An-Najah National University
Abstract
Recently, Power electronic devices are applied in many fields, mainly in the industry and domestic appliances. The major problem that faces the power system by these devices is the generation of current harmonics. These harmonic currents act as a source of pollution to the power system as they have the major following impacts:
• Reduction of power quality parameter represented in power factor and system efficiency.
• Increment of total harmonic distortion.
This work investigates the mitigation of harmonic currents by different LC-filter configurations to improve the quality parameters of supplying electrical grid. Also it discusses the design and simulation of these LC passive filters within SCR rectifier.
The performance parameters of the controlled rectifiers, with various LC-filter configurations, for RL–load and firing angles, investigated in this work are: input current THD, input power factor, efficiency and output voltage.
This investigation was implemented by FFT analysis tool through MATLAB/SIMULINK.
The simulation of a single phase full wave controlled rectifier with RL-load and a firing angle of α=30° has resulted in: THD=18.04%, PF=0.804 and rectification efficiency of η =73.53%.
Inserting a series resonance LC-filter at the input of this rectifier, the simulation resulted in THD=2.52%, PF=0.745 and η=63.05% the corresponding reactive power to be installed in the LC-filter amounts to Q=39.053 kVAr.
Investigating the insertion of a high pass T-LC filter, the simulation results in THD=4.27%, PF=0.842, η =77.87% and Q=14.96 kVAr. The results for the T-LC filter indicate a considerable improvement of the grid quality parameters (especially for THD) in comparison with the corresponding parameters of the rectifier without LC-filter.
In addition, five LC-filter with different topologies were inserted at the input of the rectifier and investigated in the thesis. The simulation results of all seven filters show a significant reduction in the harmonic currents represented in THD for the different filters in the range of THD = 2.522%-5.15 %.
Moreover, the rectification efficiency could be improved by a simple second order high pass LC-filter to achieve η =79.66% at an installed reactive power of Q=10.086 kVAr.
The thesis compass investigating the mentioned main grid quality parameters beside other parameters for different firing angles of the above mentioned full wave controlled rectifier.