Inverters are those which convert fixed dc voltage to variable ac output voltage and frequency.
Harmonics are generated in the power electronic circuit due to the frequent turn-on and turn-off of the semiconductor devices. Due to this disturbances in the circuit, it causes fluctuations in the supply voltage, torque pulsations, low power factor, , increase of losses, less efficiency, etc.
3. PWM Technique:
In this technique, a fixed dc voltage is applied to the inverter as a input and a controlled ac output voltage is obtained by adjusting the ON and OFF period of the inverter devices.
In this scheme, there is only one pulse per half cycle and the width of the pulse is varied to control the inverter output voltage.
In this scheme, there are several pulses in each half cycle and the width of the pulse is varied to control the inverter output voltage. This method permits reduction in harmonic content up to low output voltage.
OP-amp acts as a comparator, which compares the carrier triangular signal and a dc reference signal.
7. Pulse Generator:
It generates trigger pulses/firing pulses; in order to turn-on the switching/power semiconductor devices.
8. Voltage source inverter:
In VSI the input dc voltage remains constant at low input impedance irrespective of ac voltage delivered to load.
9. Utility Factor:
It is the ratio of power delivered by the three-phase inverter when the load is 3-ϕ balanced to the total power rating of all switching devices of the bridges.
10. Current source inverter:
In CSI the input dc current from the dc source is maintained at an effectively constant level at high input impedance irrespective of load.