A comparative analysis of modulation techniques in multilevel inverter for pv applications

It is observed that the power quality requirements that must be provided in power systems change day by day depending on the conditions of the day. The prominent factors that negatively affect power quality are voltage and/or current harmonic distortions. In general, voltage and/or current harmonics are generated by non-linear and switched systems. Grid-connected power electronics converters used in distributed generation units, reactive power and voltage compensators are one of the systems that generate various harmonics. Inverters, which are among the power electronics converters, can be classified as two level and multilevel. Two-level inverters are generally used in grid and small-scale industry applications, and multilevel inverters are used in structures with medium and high power conversion demands. Compared to two-level inverters, multilevel inverters have many advantages such as low electromagnetic compatibility (EMC), high voltage capability, low switching losses and high power quality waveforms. The main purpose of a multilevel inverter is less harmonic distortion and a high quality output voltage waveform. It can be named in three categories that can be done to increase the efficiency of a power electronic converter system, to reduce the harmonic distortions caused and to meet the requirements of the standards: Topological improvement, considering new modulation technique and employing suitable control strategies. In the literature, three basic modulation techniques are used for multilevel inverters. These are: Multilevel sinusoidal pulse width modulation (SPWM), space vector pulse width modulation (SVPWM) and multilevel selective harmonic elimination pulse width modulation (SHE-PWM). The aim of this research study is to perform performance analysis of multilevel inverter for photovoltaic applications with various modulation techniques. In this study, to evaluate performance parameters such as inverter output current and voltage waveforms, inverter efficiency (Normal efficiency, European efficiency and California efficiency), active inverter input and output powers and total harmonic distortion (THD) value, sinusoidal pulse width modulation (SPWM), third harmonic injected pulse width modulation (THI-PWM), space vector pulse width modulation (SVPWM) and hybrid pulse width modulation (HPWM) techniques are applied for single phase 5-level H-bridge diode clamped (DC) inverter.