Digital current control in a rotating reference frame - Part I: System modeling and the discrete time-domain current controller with improved decoupling capabilities

Digital current control of three-phase voltage-source power electronic converters is analyzed. Special attention is paid to the exact discrete time-domain modeling of inductive-resistive current dynamics in the rotating reference frame whereas three different regular sampling strategies are incorporated to the analysis. The exact system model motivates the development of a new current control structure in the rotating reference frame that is based on discrete time-domain analysis. Ideally, the new discrete time-domain current controller leads to a full compensation of all cross-coupling effects that appear in the controlled system. The experimental results (performed on a 22 kW test-bench) reveal that even under test conditions an excellent decoupling capability of the presented controllers is achieved.