Harmonic current reduction of three-phase rectifier based on modified line injection technique

This paper presents a modified line injection technique to reduce the input line current harmonics generated by three-phase AC/DC rectifiers. In conventional harmonic current injection method the optimum harmonic current reduction is obtained when (root mean square) (rms) value of the injection third harmonic current equals the DC load current. Therefore the power diode peak current is increased by 72 % compared to without injection case. In this paper a modified harmonic current injection is applied using a three-bidirectional switches connected to the input lines of the rectifier. The switch that is connected to line with zero current will be turned on to inject the harmonic current to it . In this method optimum harmonic reduction is obtained when the injection third harmonic current equal , one third of the DC load current. Therefore the power diode peak current is increased by 23.5% only and total harmonic distortion (THD) of the input current is less than 5% is obtained.