AC–DC Converter – I | Totem Pole PFC | DC–AC Converter | SPWM | Electric Vehicles | Lecture 13

AC–DC and DC–AC converters form the backbone of modern electric vehicle charging systems, enabling efficient power conversion between the utility grid, the DC link, and the battery. In this lecture, we begin by completing the analysis of the Totem Pole Power Factor Correction (PFC) converter, discussing its operation during positive and negative half cycles, deriving the variable duty ratio, and explaining the switching strategy for active devices. The lecture also demonstrates how replacing all passive devices with active switches improves converter performance and forms the basis of advanced AC–DC converter topologies.

The lecture then introduces the architecture of a practical EV charger, highlighting the integration of a two-level AC–DC converter with an isolated DC–DC converter. It proceeds to explain the fundamentals of DC–AC converters (Voltage Source Inverters), beginning with square-wave operation, followed by quasi-square-wave and multi-pulse operation. The advantages and limitations of each technique are discussed with emphasis on output voltage regulation and Total Harmonic Distortion (THD).

Finally, the lecture presents Sinusoidal Pulse Width Modulation (SPWM), one of the most widely used inverter modulation techniques. Both bipolar and unipolar modulation methods are explained using sinusoidal reference and triangular carrier waveforms, illustrating the switching logic and output voltage generation in practical inverter systems used for electric vehicle and power electronic applications.

Topics Covered

Totem Pole PFC Converter Operation
Positive and Negative Half-Cycle Analysis
Duty Ratio Calculation for Totem Pole PFC
Active Switch Implementation
EV Charger Architecture
Two-Level AC–DC Converter
DC–AC (Voltage Source Inverter) Fundamentals
Square Wave Operation
Quasi Square Wave Operation
Multi-Pulse Operation
Sinusoidal Pulse Width Modulation (SPWM)
Bipolar PWM Technique
Unipolar PWM Technique

Who Should Watch?

B.Tech. and M.Tech. students
Power Electronics learners
Electric Vehicle enthusiasts
GATE and ESE aspirants
Researchers working on EV charging systems
Engineers designing AC–DC converters, inverters, and motor drive systems

Recommended References

D. W. Hart, Power Electronics, McGraw-Hill, 2011.
P. S. Bimbhra, Power Electronics, 5th Edition, Khanna Publishers, 2012.

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