Discrete-Time Complex-Vector Model Based Closed-Loop Current Controller for CSC-Fed PMAC Machine Systems With Low Carrier Ratios

Abstract

Pulsewidth modulated (PWM) current-source converters (CSCs) have been attractive for high-power adjustable-speed machine systems with low carrier ratios. However, the high-order nonlinear model of CSC-fed machine systems, the distinct digital delay from the low carrier ratios, and the cross-coupling caused by coordinate transformation bring great challenges to design of high-performance stator current controller for such kind of machine systems. Firstly, this article derives the discrete-time complex-vector model for the CSC-fed permanent-magnet ac (PMAC) machine system with low carrier ratios considering the distinct digital delay and cross-coupling effect mentioned above. On that basis, the stator current controller is proposed with the modified controller parameters and the compensation technique to improve both dynamic performance and stability of the CSC-fed PMAC machine systems with low carrier ratios. The theoretical analysis and controller design process have been presented in detail to provide a guide for the model derivation and controller design. The experiments on a laboratory prototype are conducted to verify the effectiveness of the developed modeling and controller.