Methodology for analysis and design of discrete time current controllers for three-phase PWM converters

In this work, a methodology for the analysis and design of robust, high bandwidth current controllers for three phase converters is presented. The overall goal is to demonstrate how the proposed model based control structure and the design methodology lead to an optimized digital current controller that exhibits fast and smooth dynamics as well as an excellent disturbance rejection ability. First, accurate discrete time models are derived and used to review classical current control from the perspective of the synchronous and stationary reference frame. Then, implementation options for the synchronous frame proportional integral (SFPI) regulator and the proportional resonant (PR) regulator are discussed and systematically compared in the stationary frame leading to the formulation of a general controller framework based on space vector resonators. It embodies multiple complex resonators and can represent the SFPI regulator, the PR regulator and beyond that any higher order regulator structure. For this framework, a step by step design procedure based on the complex root locus is proposed that allows an insightful optimization of its feedback gains. Finally, the performance of the presented control design techniques is evaluated experimentally.