中文摘要：

中点箝位型（NPC）三电平逆变器在实际使用过程中，其中点电压不平衡问题一直存在。首先分析了直流侧电容电压不平衡原因实际是由于“0”状态充放电不平衡造成，针对传统载波调制受负载功率因数限制的不足，提出一种双调制波载波脉宽调制（DMWPWM）策略，该策略通过注入电压补偿量以调整“0”状态的占空比．来达到能在负载任意功率因数范围内实现直流侧电容电压平衡的目的。为减小开关损耗。电压补偿量只叠加在双调制波均不为零的情况下。最后通过仿真和实验验证，证明了该策略分析方法的正确性和有效性。

英文摘要：

The neutral voltage unbalanced is an problem for the application of three-level neutral point clamped （NPC） inverter.Firstly ,the reason of voltage unbalanced are analyzed and practical reason is in the ＂O＂ conditions due to un- balanced state of capacitor charging and discharging,for the traditional carrier modulation restricted by load power factor, the double modulation wave carrier-based pulse width modulation （DMWPWM） strategy is proposed to solve the problem, the voltage offsets is injected to adjust the state of the ＂O＂ duty ratio to achieve the arbitrary load power factor within the scope of the realization of the aim of DC side capacitor voltage balance.In order to reduce the switching loss,voltage offsets only stack in the case of double modulation wave is not in zero areas.Finally ,the cor- rectness of theoretical analysis is verified by simulation and experimental results.