Comparative Stability Analysis of Synchronous Reference Frame Current Controllers Operated at High Fundamental Frequency

Synchronous reference frame (SRF) proportional-integral (PI) current controller (CC) is the most well-established solution for current regulation in ac machine drives and grid-connected voltage source converters. The design of high dynamic performance current control loop has several challenges in high-speed and high-power applications due to the effects of controller gain's selection, nonlinearities, parameters variations, disturbances, digital implementation, and time delays. These become more significant due to high operating frequencies, which severely degrade dynamics and stability of the current control system. Various structures of SRF PI CCs have been reported in the literature. However, the aforementioned effects on the dynamics at high-frequency operation have not been thoroughly addressed. Therefore, a comparative analysis of different SRF PI CCs' structures is proposed in this article, which addresses the design principles and gains' selection while also taking into account the heavy computational burden and pulsewidth modulation (PWM) delays. In addition, this article thoroughly analyzes and evaluates the dynamics and stability of the system operating at high fundamental frequencies. The advantages and limitations of each SRF PI CC scheme are studied and reported. The performance of the SRF PI CCs is comprehensively tested to demonstrate the analytical outcome of this study.