This paper proposes a new modulation strategy that balances the neutral-point voltage for three-level neutral-clamped inverter systems. The proposed modulation replaces the P-type or N-type small switching states with other switching states that do not affect the neutral-point voltage. The zero and medium switching states are employed to help the neutral-point voltage balancing. This method little bit increases the switching events and output total harmonic distortion. However, this method has a strong balancing ability at all regions. Further, it is very simple to implement in both space vector modulation and carrier-based PWM methods. Simulation and experimental results verify the validity and feasibility of the proposed new modulation strategy.
I E E E Transactions on Energy Conversion, 2014, Vol 29, Issue 1, p. 91-100
Carrier-based PWM (CB-PWM); Multilevel; Neutral-point clamped (NPC) inverter; Neutral-point voltage balancing; Space vector modulation; T-type inverter