Investigating the influence of semiconductor device voltage drops on harmonic and reactive current compensation with cascaded multilevel inverters

Cascaded multilevel inverter is a superior option for static var compensators and active power filters, especially in high voltage and/or high power applications due to its modular structure and distributed voltage stress and switching losses among switching devices. The influence of semiconductor device on-state voltage drops on the harmonic current and reactive power compensation in a cascaded multilevel inverter is studied in this paper. It has been found that device voltage drops may cause severe distortions to the output voltage of the cascaded multilevel inverter. It greatly deteriorates the compensation performance. In this paper, analysis, simulation and experiments were conducted to study the influence of the device voltage drops on a cascaded multilevel inverter based harmonic current and reactive power compensator. Based on the analysis of the steady-state waveforms in frequency domain, a technique to reduce the influence of device voltage drops is proposed and verified by simulation results.