A novel control algorithm of a three-phase PWM inverter with output LC filter

Abstract

In this paper we introduce a novel control method of a three-phase PWM inverter with output LC filter. The transfer function of LC filter is the same as that of second order LPF(low pass filter) except that it has zero damping ratio. A simple method to implement second order LPF with damping ratio is adding resistor in series with reactor. But the series resistor cannot be used in real high power system because it consumes lots of energy being proportion to square of conducted current. So, proposed control strategy utilizes the measured capacitor voltages and voltage references of inverter to damp LC filter resonance instead of a series resistor. The overall transfer function is the same as second order LPF and damping ratio is also controllable via control variables. Experimental waveforms are presented to verify LC filter control algorithm.