A robust multi-loop linear controller for transformer-based single-phase PWM inverter

This paper proposes the modeling of the single-phase full-bridge inverter as a linear high order system integrating both the input voltage and load variations as disturbances. The model considers the output voltage to duty cycle transfer function (TF) as the plant of the control system when the converter operates using constant frequency Pulse Width Modulation (PWM). A simple nested loop controller is proposed including two Proportional-Integral compensators which ensure a minimum deviation of the desired Root Mean Square (RMS) value and a reduced Total Harmonic Distortion (THD) in the output voltage despite of the harmonic or reactive content of the power load. Both the model and the correct operation of the control system were validated by means of simulation results using resistive, resistive-inductive and nonlinear loads for different power levels demonstrating its advantageous characteristics.