A general programmed three-level PWM modulation algorithm was proposed in this paper based on the volt-second (V-S) balance principle. A general switch sequence was designed in a single period of carrier, where three different levels were considered in each phase switching sequence. According to the special solution plan of the V-S balance equations, different control objects of NPC three-level inverter are achievable through selecting different calculation criteria. Meanwhile, the modulation algorithm is greatly simplified, and has more clear physical meaning. On the purpose of achieving the neutral voltage balance and low frequency oscillations suppression, this paper puts forward the nine-segment special solution planning programmed PWM algorithm and the neutral voltage closed-loop control strategy based on the special solution plan to solve the problem of the calculating complexities in the virtual voltage vector modulation strategy simultaneously. The methods of special solution plan and pulse distribution are described in detail. The experiment was conducted on the NPC three-level prototype platform using inductance-resistance load and PMSM load. The results have proved the accuracy and effectiveness of the proposed algorithm.%基于伏-秒(V-S)平衡原理,提出一种通用程控三电平PWM方法,在单个载波周期内,设计一种通用的开关序列,其中每相开关序列均考虑三种不同电平,揭示三电平PWM算法可根据不同的控制目标对伏秒平衡方程特解进行规划来实现,物理意义更明晰.为了实现中点电位平衡与低频脉动抑制,解决虚拟电压矢量调制策略计算复杂的问题,以特解规划为基础,提出九段式低频脉动抑制PWM特解规划算法和中点电位闭环控制策略,给出了脉冲分配方法,无需扇区判定及矢量合成分析.建立中点钳位(NPC)三电平样机实验平台,采用阻感负载和永磁同步电机(PMSM)负载实验验证了所提方法的正确性和有效性.
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