1. Dr. Unnikrishnan P.C. Professor, EEE
EE305 Power Electronics
Dr. Unnikrishnan P.C.
Professor, EEE

2. Voltage control in inverters-Types
Internal Control of the Inverter (PWM for voltage and harmonic control
External control of the AC output voltage
External control of the DC input voltage

3. Internal Control of Inverter -Pulse Width Modulation
Types of PWM Inverters
Single Pulse Width Modulation
Multiple Pulse Width Modulation
Sinusoidal Pulse Width Modulation

4. Single Pulse Width Modulation

5. Single Pulse Width Modulation
RMS value of the output voltage waveform is
Output expressed as a Fourier series
nth harmonic voltage is

6. Multiple Pulse Width Modulation

7. Multiple Pulse Width Modulation
Frequency of carrier signal is much higher than the reference signal
Whenever the reference signal is greater than the carrier signal, a high pulse is produced by a comparator which is used as gating signal to turn ON the controlled devices.
The frequency of the reference signal decides the frequency of the inverter output voltage.
Uniform multiple pulses can be generated in the output voltage, also known as uniform pulse width modulation.

8. Multiple Pulse Width Modulation
N - The number of output pulses in each half cycle

9. Multiple Pulse Width Modulation with first cycle of carrier wave