For shielding voltage sensitive loads from diverse power quality problems (Voltage harmonic distortion and voltage sag/swell) a wide variety of custom power devices are used. Dynamic voltage restorer (DVR) is one of the important custom power device presently used for mitigation of above mentioned power quality problems. In this paper, reduced-rule fuzzy logic controller based on synchronous reference frame theory for controlling of self-supported dynamic voltage restorer (DVR) is proposed. As a result of the proposed controller, the mathematical model of plant is not at all needed and the control signals required by the DVR are thoroughly provided during various types of power quality problems at the source side. The performance of this technique is better than the other existing techniques and it is very simple to implement, less complex, very flexible and robust in nature. For the same system parameters, the fuzzy logic based controller uses the less amount of reactive power to mitigate the various disturbances at source side compared to PI based controller, which results into reduced rating of IGBTs and consequently leading to lowering of the overall cost. DVR is simulated for mitigation of various power quality problems (voltage harmonic distortion, balanced voltage sag/swell, unbalanced voltage sag/swell, balanced voltage sag/swell with harmonic distortion and unbalanced voltage sag/swell with harmonic distortion) and the simulation results verified by experimental results are presented displaying the workability of proposed controller.
This paper presents an analysis of current source inverter (CSI)-based unified power quality conditioner (UPQC) to improve the electric power quality at distribution levels. In recent years unified power quality conditioner (UPQC) is being used as a universal active power conditioning device to mitigate both voltage as well as current harmonics in a polluted power system network. Fabrication of UPQC is done implying both current source and voltage source inverter. Current source UPQC has unique advantages over generalised voltage source-based UPQC. Reference and switching signals are derived using a simple PI controller and robust hysteresis band PWM technique respectively. The resultant compensation system eliminates voltage as well as current harmonics with good dynamic response. Extensive simulation results using MATLAB/Simulink and SimPowerSystems software for R-L load connected through an uncontrolled bridge rectifier is presented for performance evaluation.
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