A comparative study of 5-level and 7-level multilevel inverter connected to the grid

Abstract

Power electronic converters were developed for integrating the photovoltaic (PV) arrays and utility grid. Inverters are needed to convert the direct current electricity produced by the PV array into alternating current electricity required for loads. Nowadays, multilevel inverter gained so much popularity in PV systems. Multilevel inverter promises a lot of advantages over conventional inverter especially for high power applications. Some of the advantages are that the output waveform were improved since multilevel inverter produced nearly sinusoidal output voltage waveforms, hence the total harmonic distortion also low. The switching losses also become less. And, the filter needed to smooth the output voltage is small; hence, the system is compact, lighter and much cheaper.

Harmonic Minimization in a Modified Cascaded Multilevel Inverter for Islanded Microgrid using two Switching Techniques

“…With the multilevel inverters the harmonic distortions can be reduced with the increase in the higher levels of output. With separate dc sources the cascaded multilevel inverters are used [13], in our research a modified topolopgy of 7 level 6 switches cascaded multilevel invereter [7] is used. Switching power devices causes harmonics in the sensitive equipments which are connected to the non-linear loads for the applications of higher kilowatts, hence an LCLfilter is connected at the output of modified multilevel inverter to reduce the total harmonic distortion (THD) in the islanded microgrid as shown in the block diagram of Figure 1 below [1].…”

An Investigation of THD in 5-level NPC Multilevel Inverter Based on Multicarrier PWM Techniques

“…Comparison results, the power electro-nic switch is closed when the reference signal is greater than the carrier signal, and the switch is opened when the reference signal is less than the carrier signal. The modulation technique [10] used in this paper is sinusoidal pulse width modulation technique. The method is to produce the gate signal by comparing a triangular carrier signal with two reference signals as shown in Fig7.…”