兼顾共模电压抑制与中性点电压平衡的T型三电平逆变器DPWM策略

DPWM Strategy for T-type Three-level Inverter Considering Common-mode Voltage Reduction and Neutral-point Voltage Balance

为提升T型三电平逆变器的可靠性与效率,提出1种可抑制共模电压的非连续脉宽调制RCVDPWM(reduced-common-mode-voltage pulse width modulation)策略,同时能够降低开关损耗。根据T型三电平拓扑开关序列对共模电压作用机理,总结出5种实现共模电压抑制的非连续脉宽调制DPWM(discontinuous pulse width modulation)钳位方式。分析表明,在任意调制度和相角下,至少存在1种实现共模电压抑制的钳位方式。对于部分相角区间存在的多种钳位方式,优先选取电流绝对值最大相的开关管进行钳位,以降低开关损耗。同时,所提RCVDPWM策略可保证中性点电压直流分量为0,具有中性点自平衡能力。实验结果验证了RCVDPWM策略的可行性与有效性。

To improve the reliability and efficiency of a T-type three-level inverter,a discontinuous pulse width modulation(DPWM)strategy is proposed to reduce the common-mode voltage while reducing the switching loss,which is also named as the RCVDPWM strategy.According to the mechanism of switching sequence in the T-type three-level topology which acts on the common-mode voltage,five DPWM clamping methods for common-mode voltage reduction are summarized.It can be found that there is at least one clamping method for common-mode voltage reduction at any modulation ratio or phase angle.For those phase angle regions where multiple clamping methods exist,the switch tube of the phase with the largest absolute value of current is preferentially selected for clamping to reduce the switching loss.Meanwhile,the proposed strategy can ensure that the DC component of neutral-point voltage is zero,and thus the neutral point shows a self-balancing capability.Experimental results verify the feasibility and effectiveness of the proposed RCVDPWM strategy.