Dual Active Bridge NPC

In an NPC DAB converter, how is the duty cycle defined when there are four switches in one leg producing three output levels (+Vdc/2, 0, −Vdc/2) — is it defined per switch, per switch pair, or as a modulation index mapped to the desired output level?

Thank you very much un advance

Answer 1

[Simran]

Hi @Ahmed,

I understand you're trying to determine how the duty cycle is defined in an NPC (Neutral Point Clamped) DAB converter configuration where four switches in one leg produce three output levels (+Vdc/2, 0, −Vdc/2).

Assuming you're working with power electronics modeling in Simulink using Simscape Electrical (Specialized Power Systems) on MATLAB R2025b using the latest Windows version:

I would suggest exploring these areas:

1. Review NPC converter modulation fundamentals:

• The duty cycle definition in multi-level converters depends on the modulation strategy being used
• Common approaches include defining it per switch pair, or as a modulation index
• This is typically determined by your control strategy (e.g., phase-shift modulation for DAB)

Please refer to the below documentation for more information:

• Three-Level Converter (Three-Phase) - Twelve-pulse three-phase three-level neutral-point clamped controlled converter - MATLAB - for understanding multi-level converter topology
• Dual Active Bridge Control - MATLAB & Simulink - Control strategies for DAB converters
• PWM - Generate ideal pulse width modulated signal corresponding to input duty cycle - Simulink - how to define modulation signals

Hope this helps!