Actively Damped PI-based Control Design of Grid-Connected Three-Level VSC with LCL Filter

Nowadays Grid-Connected Voltage Source Converters (GCVSC) are used in a wide range of applications, such as renewable energy systems, power conditioning or high power factor rectifiers. Recommended practices and requirements demand low harmonic distortion of the injected grid currents especially in weak grids and rural areas, which can be achieved by many means. This paper deals with the design of a PI-based grid current vector control system for a three-level GCVSC with an actively damped LCL output filter, particularly focusing on practical issues to max out control performance as well as taking requirements concerning current harmonics into account. Appropriate simplifications of the control plant transfer function are applied to enable quick tuning parameter determination while keeping approximation errors low by taking the impact of active damping into account. Overall system performance is assessed in terms of control rise time and injected grid current harmonic distortion. Simulation and experimental results validate the presented control system