Enhancement of Dynamic Performance of a Single Phase Cascaded H-Bridge Multilevel Inverter Using Closed Loop Controllers

Abstract

This paper explores the steady state and dynamic performance of a cascaded H-Bridge multilevel inverter (CHB-MLI) with the help of closed loop controllers. Dual loop cascaded controller is suitable for MLI system for addressing various issues. It consists of two loops i.e. outer loop and inner loop. The outer loop controller is Proportional-Integral (PI) controller which is used as a voltage controller and inner loop controller is Proportional (P) controller which is used as a current controller. The steady state voltage i.e. constant output voltage can be obtained with the help of voltage controller while the time taken to reach the steady state i.e. transient/dynamic period can be reduced with the help of current controller. The same controller is used for both linear load and nonlinear load. In this paper, the closed loop CHB-MLI model is designed in MATLAB/SIMULINK platform with proper selection of controller parameters i.e. proportional gain (K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> ) and integral gain (K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> ). By controlling these two parameters in both of the loops, the steady state and dynamic performance of a CHB-MLI is obtained for linear load. For the non-linear load steady state performance is investigated using the same controller by taking the same values of the controller parameters as used for linear load.