Discrete time modeling, implementation and design of current controllers

Abstract

This work addresses discrete time modeling, implementation and design options for the current control of three phase grid tied PWM converters. Based on an accurate discrete time model of the PWM converter, closed loop current control is reviewed 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 leading to the formulation of a general controller framework based on space vector resonators: the Resonant Space Vector (RSV) regulator. It can embody multiple SFPI regulators on different frequencies and allows a consistent design of state feedback controllers as well as an efficient implementation. For this control framework an insightful design procedure based on the root locus method for complex system models is introduced. Finally, the performance of the presented control design and implementation concepts is demonstrated experimentally.