Abstract: The power quality (PQ) in distribution systems is principally affected by the pollution introduced by the customers. It is necessary to protect the sensitive loads from disturbances such as sags, swells, source voltage imbalances, etc. The actual solution for this case is to employ a dynamic voltage restorer (DVR) device. Dynamic Voltage Restorer (DVR) is a series connected compensators. A DVR has to supply energy to the load during the voltage sag and swell. The use of multilevel inverters in DVR improves the harmonic performance of the System. The synchronous reference frame based control is used for the DVR control. In this paper the design and simulations of three level inverter based DVR is discussed. A three level inverter based DVR and a two level inverter DVR is simulated in MATLAB software and the results are analysed. From the result it is observed that load voltage is maintained at reference value by injecting a series voltage and the load voltage THD is improved by employing the three level inverter.

Keywords: PQ-Power Quality, DVR-Dynamic Voltage Restorer, THD-Total Harmonic Distortion, PWM-pulse width modulated.