一种改进的三电平变流器不连续调制策略

An Improved Discontinuous Modulation Strategy for Three Level Converter

针对传统的非连续脉宽调制(DPWM)策略共模电压较高的缺点,提出了一种改进的调制策略,该策略可以同时达到减小开关损耗、降低共模电压和消除中点电压直流偏移的目的,该调制策略被称为改进的降低共模电压的DPWM(RCMV-DPWM)策略。首先分析了中点箝位型三电平变流器(NPC TLC)的空间矢量图,通过弃用某些基本矢量实现减小共模电压;为了消除中点电压直流偏移和降低开关损耗,在综合运用最近相邻三矢量和非最近相邻三矢量的矢量合成原则下,详细分析了各种箝位模式存在的可能性,选择恰当的箝位模式实现对中点电压的控制。同时分析了RCMV-DPWM对中点电压的控制能力,并与其他PWM策略进行了比较。最后,通过实验验证了RCMV-DPWM的可行性和优越性。

An improved discontinuous pulse width modulation(DPWM) strategy for neutral point clamped three level converter(NPC TLC) is proposed to reduce switching loss,reduce common mode voltage and remove direct current offset on neutral point voltage simultaneously,which is named as improved reduced common mode voltage DPWM(RCMVDPWM).Firstly,the space vector diagram of the NPC TLC is analyzed,and the common mode voltage is reduced by discarding some basic space vectors.Then,in order to remove direct current offset on neutral point voltage and reduce switching loss,the possibility of all clamping modes is revealed based on the nearest three vectors and non-nearest three vectors synthesis principles.Neutral point voltage is controlled by selecting proper clamping mode.Moreover,performances of RCMV-DPWM are analyzed and compared with other PWM strategies in term of control ability of neutral point voltage.Finally,the feasibility and superiority of RCMV-DPWM are verified by experiments.