EE 4109 Lecture 05 Sinusoidal Pulse Width Modulation

EE 4109 Lecture 05 Sinusoidal Pulse Width Modulation (SPWM) Reference Book: Power Electronics: Circuits, Devices, and Applications by Muhammad H. Rashid 2/22/2021 Department of EEE, KUET 1

This lecture is for Learning Outcome 3 (LO 3): At the end of the course students will be able to identify and design DC-AC converters (inverters) and their gate driver circuits 2/22/2021 Department of EEE, KUET 2

Sinusoidal Pulse-Width Modulation • In multiple-pulse modulation, all pulses are the same width • Vary the pulse width according to the amplitude of a sine wave evaluated at the center of the same pulse 2/22/2021 Department of EEE, KUET 3

Generate the gating signal 2 Reference Signals, vr, -vr 2/22/2021 Department of EEE, KUET 4

Comparing the carrier and reference signals • Generate g 1 signal by comparison with vr • Generate g 4 signal by comparison with -vr 2/22/2021 Department of EEE, KUET 5

Potential problem if Q 1 and Q 4 try to turn ON at the same time! 2/22/2021 Department of EEE, KUET 6

If we prevent the problem Output voltage is low when g 1 and g 4 are both high 2/22/2021 Department of EEE, KUET 7

This composite signal is difficult to generate 2/22/2021 Department of EEE, KUET 8

Generate the same gate pulses with one sine wave 2/22/2021 Department of EEE, KUET 9

Alternate scheme 2/22/2021 Department of EEE, KUET 10

rms output voltage • Depends on the modulation index, M Where δm is the width of the mth pulse 2/22/2021 Department of EEE, KUET 11

Harmonic Profile 2/22/2021 Department of EEE, KUET 12

Compare with multiple-pulse case for p=5 Distortion Factor is considerably less 2/22/2021 Department of EEE, KUET 13

Modified SPWM 2/22/2021 Department of EEE, KUET 14

Modified SPWM 2/22/2021 Department of EEE, KUET 15

Self Study Detail of Modified SPWM and phase displacement control End of Lecture 4 2/22/2021 Department of EEE, KUET 16