Control of quasi z source inverter based dvr and its application in a microgrid

Abstract

Dynamic Voltage Restorer DVRis a custom power device to mitigate the effects of voltage sags/swells in sensitive loads It is a series compensation device which injects an appropriate compensating voltage into the distribution line and is connected closer to the sensitive load The objective of this work is to investigate methods to improve the performance of newlinethe DVR by focusing on the DVR control system, converter topologies and energy storage DVRs employ Voltage Source Inverters VSI as power converters which require a large DC energy storage to mitigate deep voltage sags In a quest to reduce the size of energy storage of the DVR the use of a new set of converters called Quasi Z Source Inverters QZSI which are very effective in renewable systems is explored Nonlinear control methods such as newlinesliding mode controllers are highly effective in systems with power electronic converters Hence the performance of QZSI based DVR with sliding mode control is investigated against the performance of conventional DVRs with PI Proportional plus Integral controllers and VSIs The combined advantagesof sliding mode controllers and QZSI bring effective sag/swell mitigation even with energy storage of low rating Performance studies of the proposed DVR under various parameter variations such as different types of loads load newlinecurrents, sag depths and storage battery voltages are conducted A prototype of the proposed DVR is built with FPGA Field Programmable Gate Array based digital controller. The simulation results of the proposed single phase DVR are validated with the hardware prototype results A DVR with the proposed design is developed for three phase systems and simulation studies also carried out. newline newline