COMPARATIVE STUDY THD AND AMPLITUDE OUTPUT VOLTAGE VIA INVERTED SINUSOIDAL PULSE WIDTH MODULATION TECHNIQUES FOR NINE LEVEL DIODE CLAMPED MULTILEVEL INVERTER

The multilevel inverters have become more popular during the recent years. The multilevel inverters are applied in many industrial applications such as static VAR compensators, AC power supplies, drive systems, active power filters, etc. The topologies of multilevel inverter have several advantages such as low distortion in output voltage with relative low switching frequency, low harmonic and good Electro-Magnetic Interference (EMI). Different pulse width modulation strategies have been used in multilevel inverter topologies. In this paper, various Inverted Sinusoidal Pulse Width Modulation (ISPWM) techniques that compared a sinusoidal reference wave with sinusoidal carrier signal are suggested for a nine-level Diode Clamped Multilevel Inverter (DCMLI) in order to minimize the Total Harmonic Distortion (THD) and increase the output voltage. In this study, three strategies will be addressed which are widely used to control of multilevel inverters: Constant Switching Frequency Inverted Sinusoidal Pulse Width Modulation (CSF-ISPWM), Phase Shifted Inverted Sinusoidal Pulse Width Modulation (PSISPWM) and Variable Switching Frequency Inverted Sinusoidal Pulse Width Modulation (VSF-ISPWM). The effectiveness of each method is verified through Matlab/Simulink software.