Discrete State-Space Current Control of PWM Converters: Robust Tracking Control with Additional Dynamics

Proportional-resonant current controllers are the stationary frame counterparts of current proportional-integral controllers that operate in the rotating reference frame. Recently, proportional-resonant current controllers have been extensively investigated to reduce the complexity produced by the coordinates transformation and to achieve zero steady error in the case of multi-frequency reference signals. This paper introduces an alternative discrete approach to the state-of-the-art continuous proportional-resonant current controller. In particular, the direct discrete design of a state-space current controller with additional dynamics with multi-frequency robust tracking capabilities is presented in this contribution. Moreover, this paper discusses the state-space formulation, the design, and the stability analysis of such a state-space controller and compares its performance with the state-of-the-art continuous proportional-resonant current controller with delay compensation. It was found that the maximum frequency that the proposed controller can target falls within the limit of switching frequency divided by five in contrast to the limit of switching frequency divided by seven of the continuous proportional-resonant controller. Furthermore, the effectiveness of the proposed state-space controller is demonstrated through hardware-in-loop (HiL) tests and experimental measurements carried out in a one kVA active power filter based on voltage detection.