Robust High-Performance Inverter Control Using Discrete Direct-Design Pole Placement

Abstract

A robust high-performance discrete controller, with a simple implementation and characterizable performance that lend it to high-power industrial applications, is proposed. Discrete direct-design pole placement allows the use of common design parameters such as damping ratio and bandwidth (BW) to define the controller's response. High performance is demonstrated with example systems achieving BWs twice as high as those of traditional cascaded current- and voltage-loop controllers. The controller is shown to be robust against component variations and many different load types, including low-impedance grid connections. Comparisons between the proposed controller and a discretized full-state-feedback continuous-time-derived controller are made and show significant improvements in both BW and stability margins. Practical tests on a parallel 2-MVA test system demonstrate a close correlation with the analysis, with an error of less than 1%.