An inverter is a circuit which converts dc power into ac power at desired output voltage and frequency. The ac output voltage can be fixed at a fixed or variable frequency. This conversion can be achieved by controlled turn ON & turn OFF or by forced commutated thyristors depending on applications. The output voltage waveform of a practical inverter is non sinusoidal but for high power applications low distorted sinusoidal waveforms are required. The filtering of harmonics is not feasible when the output voltage frequency varies over a wide range. There is need for alternatives. Three level Neutral Point Clamped inverter is a step towards it.
Figure1.Diode clamped three level inverter
EXPECTED SIMULATION RESULTS:
Figure2. Upper triangular pulse width modulation
Figure3. lower triangular pulse width modulation
Figure4. three level voltage waveform
Figure5.Matlab model of three level inverter feeding induction motor
Figure 6. stator waveform of three level inverter
In normal inverters odd harmonics are present which causes distortion of the output waveform. By using the “THREE LEVEL DIODECLAMPED INVERTER” we can eliminate some number of harmonics hence increasing the efficiency of the inverter.
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