Influence of the firing angle control in the harmonic generation of thyristor pulse controlled AC/DC/AC systems

This paper presents some selected results of experimentally based research to observe the firing angle control influence on the harmonic level generated by two 6-pulse-controlled three phase converters, connected in an AC/DC/AC configuration. The sending-end of this scheme is constituted by a rectifier, while the reception-end is made up by a three phase converter acting in its inverter mode of operation. Thus, such harmonic phenomena as the one presented in a weak AC line feeding electrochemical and electrometallurgical industries is readily simulated. Also the harmonic effects of network asymmetries in the reception-end of HVDC transmission links, can be easily implemented in this physical model. The paper includes selected graphs showing the dependence of both individual harmonic voltages and currents on the firing angles of rectifier and inverter operations. The firing angle control impact is observed for both filtered and nonfiltered harmonic phenomena