MULTILEVELINVERTERBASEDACTIVEPOWERFILTER

Abstract

Use of power electronics converters in industrial and domestic applications due to these converters harmonic currents are introduced in the supply system and cause of power quality. Two level inverter based active power filter is simulated with transformer and without transformer. The transformer rating is more than the system rating then also total harmonic distortion not less than the 5%. So this method is not suitable for high voltage system, this problem rectified by multilevel inverter based active power filter. Multilevel inverter based active power filter is used to reduce the harmonic currents. For current reference generation instantaneous reactive power theory or P-Q theory is used. In this method abc coordinates are transformed into α-β coordinates. Fundamental active power component is eliminated using low pass filter. The DC link capacitor voltage error from PI controller is added with resulting power. Then reference currents are generates in α β coordinates then transform into abc coordinates. These reference current signals are compared with actual current then error processing through the PI controller and generates a modulating signal. Multi carrier PWM method is used for the generation of control signals. The modulating signals are compared with carrier wave and generates the gate pulses for multilevel inverter. Five level cascaded inverter is used in this active power filter application. Inverter generates the required harmonic current and supplies to the load and makes source current sinusoidal.