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10 months ago in Power Electronics By Aamir

How do you guarantee clean output from a multilevel converter when dc voltages are unequal?

Standard carrier-phase-shifted PWM assumes equal DC-link voltages. What if they're not equal—say, from aging batteries or mismatched PV panels? How do I still get good harmonic performance?

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By Natasha Answered 8 months ago

You can't use vanilla CPS-PWM anymore—you need smarter modulation. Options: 1) Optimal PWM (Selective Harmonic Elimination or Space Vector PWM) that accounts for actual voltage levels in real time. 2) Modified CPS-PWM with adjusted carrier amplitudes or positions to balance the effective switching. 3) Closed-loop harmonic compensation inject corrective voltages in the control loop to actively cancel dominant low-order harmonics. The goal is the same: synthesize a clean sine wave from uneven building blocks. It's doable, but the math gets heavier.

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