Mitigating voltage SAGS or SWELLS using Z Source AC to AC converter based dynamics voltage restorer

Abstract

newlinequotPower quality has become a major concern of the modern industries in the present newlineera. Voltage sags/swells are considered as the most significant power quality problems newlinebecause of increasing complexity in the power system. To overcome these problems, newlineCustom Power Devices (CPD) is connected closer to the load end. One of those devices is newlineDynamic Voltage Restorer (DVR) which is a series connected most efficient and effective newlinemodern CPD used in power distribution network. The main function of the DVR is to newlinemonitor the load voltage constantly and if any sag or swell occurs, it can quickly mitigate newlineby injecting the balance (or excess) voltage to the load voltage. The primary advantage of newlinethe DVR is keeping the users always on-line with high quality constant voltage to newlinemaintain the continuity of production. newline newlineIn this thesis the three different topologies of DVR, Voltage Source Inverter (VSI) newlinebased DVR, Z Source Inverter (ZSI) based DVR and Z source AC-AC converters based newlineDVR have been analyzed and simulated to mitigate the voltage sag/swell. Comparisons newlineare made between these topologies that can be realized with a minimum amount of energy newlinestorage, with the energy taken from the grid. newline newline newlineIn VSI based DVR topology, a sinusoidal PWM pulse generation technique is used to generate a gate pulse. This control scheme provides superior performance compared to conventional control methods because it directly measurers the R.M.S. voltage at the load point without involving any transformation process. Even under system disturbances, this control scheme maintains a constant voltage at the load point. The control scheme is rather simple, flexible in cost and has an excellent voltage regulation capability. In ZSI based DVR topology, ZSI is introduced to enhance the voltage compensation capability of DVR and to ensure the constant dc link voltage. newlineSimple boost control technique is used to generate the gate pulse. newline newlineIn Z source AC-AC converter based DVR, the AC-AC converter has been employed to perform a direct AC-AC conver