Power-Factor Compensation for PWM CSR–CSI-Fed High-Power Drive System Using Flux Adjustment

This paper presents a novel power-factor (PF) control strategy for a high-power pulsewidth-modulated current-source rectifier-current-source inverter-fed motor drive system. The PF regulation is realized by adjusting the motor flux in the drive´s field-oriented control scheme. The relationship between the motor flux and the drive´s input reactive power is first investigated. Based on this analysis, a flux-adjustment PF regulation scheme is proposed. The proposed PF regulation method, together with a properly designed input line capacitor, can ensure a unity PF throughout the whole speed range (including flux-weakening range). Furthermore, unlike all the other PF compensation techniques, the proposed flux-adjustment approach does not require online modulation index control of the rectifier and the inverter, and therefore, offline selective harmonic elimination modulation can be implemented on both the rectifier and the inverter to minimize the line-side and motor-side waveform distortions. Medium-voltage simulation results and experimental results from a low-voltage 30-hp induction motor drive are provided to verify the effectiveness of the PF correction strategy.