Smith-Type Digital Control for a Cross-Coupling Free AC Electrical Power Distribution System of the More Electric Aircraft

The development of distributed generation systems and fully-controlled semiconductor devices has brought power electronic converters into the focus of scientific research. Synchronous reference frame-based controllers are commonly employed for the control of ac/dc converters owing to their simplicity and clear physical significance. However, in aircraft ac electrical power distribution system, the variable sampling-to-fundamental frequency ratio and higher rate of electronic devices compared to utility grid leads to more significant cross-coupling between <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{d}$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{q}$</tex-math></inline-formula> axis, which will lead to additional oscillation modes and even jeopardize the system stability. In this work, a discrete Smith predictor (SM)-based decoupling scheme is proposed with a hybrid reference frame (HRF) structure, which effectively decouples the 2 output channels without sophisticated system modeling or parameter designing process. A 2-level three-phase converter is used to elaborate its performance, experimental results show that the proposed scheme enhances the overall stability of the system with sufficient robustness against parameter variation.