Analysis design and implementation of passive filter Configurations for five level inverters

Abstract

Distributed generation using sustainable energy sources like solar and wind energy has received greater attention to meet increasing energy demand and environmental constraints Voltage source inverters are a key component in most of the grid connected and standalone distributed generation systems. Multilevel inverters are being investigated as an option owing to their advantages over conventional two level voltage source inverters for grid connected and standalone systems. A passive filter is usually connected between the inverter and the grid or the load in these systems to reduce harmonics on the inverter output voltage/current waveforms. Existing passive filters suffer from drawbacks such as reduced attenuation at the switching frequency, larger resonant peaking, higher power dissipation across the damping elements and larger filter size. Hence, this research work aims to address these challenges and gaps by developing and implementing novel passive filter configurations for a five level inverter. In this research work, initially, the harmonic profile of a five level cascaded HBridge (CHB) inverter controlled using multicarrier phase disposition pulse width modulation (PDPWM) technique is investigated, without any passive filter. Based on the investigation, LC and LCL type passive filters are designed by incorporating subtle modifications as required for a five level inverter. Procedural steps to choose the filter component values that include the reactive elements and damping resistance are provided. In addition, a modified methodology to arrive at the value of damping resistance for harmonic reduction with minimum losses is proposed for the LC and LCL type passive filters. The modified method considers quality factor, resonant peaking, harmonic attenuation rate and power loss in the damping branch to select the resistance value. Frequency response characteristics and experimental results validate the procedure that newlineis adopted to design these filters for the five level inverter newline newline