For AC to AC variable frequency speed drive system of synchronous motors applied in hot strip continuous mills

the harmonic impact on power supply net side is analyzed in detail by advanced simulation approach.Variety of situations have been studied by changing parameters of different parts in the synchronous frequency speed drive system

such as internal inductance of original/secondary sides of the transformers

external line commutating reactors and several kinds of synchronous motors with different resistance and inductance.An approach of power supply is proposed that adopting multi-group AC-AC inverters with incremental-shifting phase module to supply power.A comparative analysis of harmonic interference between the AC-AC inverter and AC-DC-AC inverter is given.Simulation results show that the approach combination regulating transformer inductance with the incremental-shifting phase modular power supply can effectively reduce harmonic interference and make the total harmonic distribution tend to be balanced in three phases.