Abstract：Conventional three-level carrier-based pulse width modulation (PWM) strategy, which has only one modulation wave per phase, cannot eliminate low-frequency neutral point (NP) voltage ripple of three-level neutral point clamped(NPC) inverter completely under some modulation index and power factor using zero sequence component injection method. In this paper, modulation wave optimal solutions of double modulation wave carrier-based PWM(DMWPWM) strategy based on voltage equivalent principle and NP potential balance principle is proposed and researched. There are 64 groups of optimal solutions of DMWPWM strategy in all, and the outstanding advantage of these solutions are as follows: ① The optimal solutions can eliminate the low-frequency NP potential ripple completely in one switching cycle regardless of modulation index and power factor. ② The optimal solutions proposed in this paper can be straightforwardly implemented in a simple microprocessor. ③ The DC voltage utilization ratio using the optimal solutions is 1.154 times of conventional three-level carrier-based PWM strategy. ④ The devices switching losses of the optimal solutions are the minimum among all of the DMWPWM strategies which meet condition ①. ⑤ The output phase voltage THD characteristics of the optimal solutions are the minimum among all of the DMWPWM strategies which meet condition ①. Simulation and experiment results verify the analysis in this paper.
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2014, Vol. 29 
