An Improved Cascaded H-Bridge Based High Power Factor Converter with Enhanced Power Quality

Abstract

An individual linear control scheme has been designed to improve the performance of 3-phase, 3.3 kV, 1MW, 5-level Cascaded H-Bridge (CHB) based High Power Factor Converter (HPFC). This individual control scheme exhibits the cell balancing system addressing the problem of DC voltage regulation in each H-bridge cell when loaded asymmetrically and current harmonics in the input source is reduced. This methodology ensures that voltages across DC bus capacitor retains to a preset value, even if the loads demand different powers. Additionally, this methodology achieves stability during the DC load perturbations at all modes of operation. In anticipation to adopt conventional Multi Level Sinusoidal Pulse Width Modulation (MLSPWM) scheme, an individual unipolar Sinusoidal PWM (SPWM) is acquired to apply on each H-Bridge cell for individual control to achieve the target. This effort addresses and curtails the capacitor unbalancing problem due to power mismatch between the loads attached to the cells and other performance indices of HPFC. The evaluation and impact of the proposed strategy is augmented by various simulations and the results are verified with dSPACE 1104 based real time experimental studies