Novel Double Modulation Wave Three-level Carrier-based Pulse Width Modulation Method

Conventional three-level carrier-based pulse width modulation(PWM),which has only one modulation wave per phase,can not eliminate low-frequency neutral point(NP) potential ripple of three-level neutral point clamped(NPC) inverter completely under some modulation index and power factor.A new double modulation wave carrier-based PWM(DMWPWM) was proposed in this paper.Based on voltage equivalent principle and NP potential balance principle,one modulation wave is decomposed into two modulation waves to implement modulation in the new PWM.One outstanding advantage of the new PWM is that low-frequency NP potential ripple can be eliminated completely regardless of modulation index and power factor.Fundamental principle of the proposed PWM was introduced in this paper,and verified by simulation and experimental results.