Design of Control System Using Online Tuning of PI Controllers for Three-Phase Active Front End Neutral Point Clamped Three-Level Converter

Abstract

In conventional DC link AC-AC converter system, uncontrolled front end converter has inherent problem of power quality. To overcome the problem associated with uncontrolled front end converter, multilevel front end converter will be good choice for high power applications. In the paper, unity power factor control system (UPC) for active front end (AFE) neutral point clamped (NPC) 3-level converter is presented. PI controllers are used in UPC and for tuning of PI controllers it is essentially required to know the different time constants with their gains exactly for evaluating the optimized controller parameters for steady operation of the NPC rectifier. In this paper a simplified and accurate method of online tuning of PI controllers in UPC is derived and implemented for three phase AFE NPC 3-level converter. Complete design procedure for the design of control system for AFE NPC 3-level is also presented in this paper. Based on developed model, simulations are carried in MATLAB/SIMULIK environment. Experimentation results confirm the simulation results.