Performance Evaluation of Grid-Connected Converters Using The Mixed Sensitivity Robust Current Control

This paper presents a robust current control strategy for the grid-connected voltage source converters (VSCs) using the mixed-sensitivity design approach. The objective is to maintain a well-damped performance under the wide variation range of the utility-grid impedance. The plant is modelled and controlled in the stationary reference frame. Firstly, the performance weighting function is designed to ensure a good tracking of the AC current at the line frequency. Secondly, the robust weighting function is designed by considering the worst-case multiplicative output unstructured uncertainty in the utility-grid impedance. A constant weighting function is used to penalize the controller effort. Finally, the H-infinity robust controller is synthesized to minimize the infinity norm of the cost function that combines the weighted sensitivity, the complementary sensitivity, and the function from the reference to the controller output. Time-domain simulations are presented and compared to the grid-connected VSCs with the proportional-and-integral (PI) and proportional-resonant (PR) current controllers.