Harmonic suppression of multi-pulse AC-DC converter with recycling system of harmonic energy at DC side

In order to improve the harmonic suppression ability of multi-pulse ac-dc converter, this paper presents a method of harmonic suppression at dc side based on principle of recycling harmonic energy. The applicable current of secondary winding for AIR is derived when the input line currents are sine waves through analyzing the current relation between ac and dc side. According to the directions of voltage and current of secondary winding, it is obtained that the harmonic of input line current can also be suppressed when a resistor is connected to the secondary winding, and the resistor must meet a match relation with the load current. In order to recycling the energy consumed by the resistor, a multi-pulse ac-dc converter with recycling circuit of harmonic energy is presented to abstract the harmonic energy to feed the load. Experimental results show the kVA rating of recycling circuit is only 2% of load power, and the system has better ability of harmonic suppression than the previous multi-pulse ac-dc converter.