PI CONTROLLER BASED OF MULTI-LEVEL UPQC USING DQ0 TRANSFORMATION TO IMPROVE POWER QUALITY IN DISTRBUTION SYSTEM

Katabathina Venkateswarlu, M.S. Sujatha

Abstract: The aim of this paper is to improve power quality in the source side of distribution system using unified power quality conditioner (UPQC) by realization of cascaded multilevel inverter (MLI). The UPQC is an integration of series and shunt active power filters via common dc link which can mitigates various power quality issues like voltage sag, swell, harmonics, interruptions etc. The cascaded MLI offers low THD in the output waveform and flexible circuit layout. The sinusoidal pulse width modulation (SPWM) switching scheme is employed for better operation of MLI. The control mechanism of UPQC is derived from dq0 transformation which is simple in its design and gives better control characteristics. The PI controller can efficiently reduce the steady state error and this can be used in UPQC controller for better response. The regulation of source voltage in the distribution system using multilevel UPQC under nonlinear load condition is analyzed in MATLAB/SIMULINK environment.

Keywords: UPQC, series APF, shunt APF, cascaded multilevel inverter, dq0 transformation, SPWM switching scheme PI controller, nonlinear load.

DOI: https://doi.org/10.15623/ijret.2014.0306043