Voltage balancing for active power filter using dual-frequency multicarrier modulation with balanced H-bridge control

Abstract

In this paper, a switching control method integrated with voltage balancing feature is presented to manage operation of single-phase 5-level cascaded H-bridge (CHB) inverter as parallel-connected active power filter (PAPF), and at the same time maintain its voltage balance. CHB inverters are always preferred for PAPF due to their dominating features of modularity, flexibility and least components count. However, inherent voltage unbalance issues of CHB inverter which is due particularly to unequal switching operation across its individual H-bridge module have always been the most troublesome when handling CHB inverter. For consistent voltage balance across each H-bridge module, proportional-integral (PI) controller for voltage balancing control and multicarrier sinusoidal pulse-width modulation (MCSPWM) for switching control have commonly been integrated together. However, these conventional approaches do not directly address the issue of unequal switching. Hence, in this work, effort is performed to allow each individual H-bridge module to operate with balance switching pattern, by evenly distributing the PWM switching signal to them. Design concept of the proposed method is modeled in MATLAB-Simulink platform. To critically assess its effectiveness, comparative analysis involving two types of highly nonlinear rectifier loads and distorted grid is performed. The presented simulation findings confirmed effectiveness of the proposed method in maintaining voltage balance of the 5-level CHB inverter when mitigating harmonics under adverse grid.

Keywords

• Active harmonic filter
• Current harmonics mitigation
• Level-shifted PWM
• Multilevel inverter
• Uniform switching pattern