On practical digital current regulator design for PM synchronous motor drives

Most high performance PWM voltage source motor drives utilize inner current-loop regulators in order to achieve high dynamic performance. In this paper, the relation between desired system performance and current-loop bandwidth are analyzed and a practical range of current-loop bandwidth for a given system is established based on PWM frequency, compensator structure, and system lag. In addition, various strategies to improve current regulation are evaluated for both phase current regulators and synchronous regulators, which includes structure of compensators, current acquisition method, and filter design. Furthermore, parameter variations due to magnetic saturation and voltage saturation are investigated and their effects on current-loop performance are studied. Insights acquired from the above analysis can be used as a preliminary design guide in choosing sampling and PWM frequencies, and selecting processors and other circuit components in order to meet performance objectives