Comparison of Different types of Inverter outputs

This chapter shows comparison between different types of inverter outputs. Different waveforms and THD spectrums are compared with pure sinusoidal waveform. Five different waveforms and THD that compared here with sinusoidal wave are:

1. Square wave inverter

2. Pulsated square wave inverter

3. PWM inverter

4. Cascade inverter with staircase topology

5. Cascade inverter with PWM topology

The wave forms and Fourier analysis of above mentioned are shown in fig.6.1.

Table 6.1 shows the comparison of above mentioned waveforms

From table 6.1 it can be conclude that PWM inverter output has minimum THD level of 10.583946% and after that cascade inverter has 14.13905% THD level. As mentioned in 3.1 that in high power and high voltage applications three level inverters have some limitations in operating at high frequency due to the switching losses and constrains of device ratings. So that for high power application or to reduce switching losses we should go for cascaded multilevel inverter for quality output. In cascaded multilevel inverter by applying proper switching angles and by adding harmonic filter to the circuit we can reduce furthermore THD. Calculation for switching angle to minimize THD level is shown is next chapter.