Power Factor Control for High Power Current Source Drive with Active Front End

This paper proposes a power factor control strategy for a current source drive with active front end, where the selective harmonic elimination (SHE) modulation is employed for the rectifier and a combination of space vector modulation (SVM) and SHE is used for the inverter to guarantee best waveforms at a low switching frequencies. The proposed power factor compensation strategy comprises two methods: a modulation index regulation method and a flux adjustment method, which when implemented together will complement each other's functionalities and improve the overall compensation performance. The modulation index regulation method functions to directly control the dc link current and voltage and it can effectively correct a leading power factor as long as the SVM is used for the inverter. On the other hand, the flux adjustment method is proposed to improve the line power factor when the power factor is lagging or when the SHE modulation is used for the inverter at high speeds. Relationships of the motor flux and drive's input reactive power have been thoroughly investigated to ensure the proper function of the flux adjustment scheme. Experimental results are obtained from both a 4.16 kV 600hp drive system and a 4.16 kV 1100hp drive system.