Design Of NPC Multilevel Inverter Closed Loop Control System

With the development of the electronic technology,researches on the control strategy of multi-level converter are looming so large in the field high-power electrical applications.This paper mainly focuses on the SVPWM arithmetic and close-loop control strategy of NPC three-level grid inverter.The paper introduces the topological structure and control strategy of high-power multi-level inverter,develops a mathematical model of NPC three-level grid inverter,analyzes the modulation technology of three-level SVPWM.and carries out researches on the realization of SVPWM arithmetic.Based on the SVPWM arithmetic,a controlling system of the voltage loop and current inner ring double closed loop of NPC three-level grid inverter was designed.To ensure the properties of controlling system,the voltage loop and the current loop in the dissertation adopted PI control,and the principles of the selection of main circuit filter inductance and capacitance were studied.On the basis of the mathematical model and control strategy,the dynamic-steady state properties of the system when the load of NPC current presents a sudden augment and the value of three–phase power grid voltage jumps accidentally on a set power were studied in MATLAB/SIMULINK.The result of the simulation indicates that,under a control strategy of the design,the ideal voltage and current waveform was obtained with a low probability of deformation of interconnection,which suggests the relatively idealized waveform of current and voltage,thus lending support to the feasibility and validity of the controlling systematic arithmetic of the closed loop by the design.