二极管钳位式三电平逆变器的拓扑结构导致了中点电位的不平衡,其实质在于有电流流过直流侧的电容中点. 准双极性调制策略能充分利用冗余电压小矢量抑制中点电压波动,但对深度调制时中矢量引起的电位波动却无能为力. 为此提出一种抑制中点电位波动的有效控制方法. 该方法基于首发矢量为正小矢量的准双极性调制策略,并引入一个控制因子k,根据直流侧中点电位重新分配下一个采样周期内的正、负小矢量作用时间,以此来实时控制流入电容中点的电荷量,减小中点电位的波动. 为便于硬件实现,减少窄脉冲的发生,又对k进行了分级控制设计. Simulink仿真结果验证了该方法的有效性.%Topology structure of diode-clamped three-level inverter leads to its neutral voltage balance problems, the essence of the neutral-point potential variation lie in the current which through the Capacitance midpoint of the DC side. Although semi-bipolar PWM pattern can take full advantage of redundancy small voltage vector, and be beneficial to restrain the neutral-point voltage potential variation, it is helplessness to the potential variation caused by medium-vector, especially at high modulation depth. Based on a semi-bipolar PWM pattern strategy where positive small vectors were adopted as first active vector, and a control factor k was introduced, so according to the neutral-point voltage potential variation of the DC side, we could redistribute the action time of the positive or negative small vector in next sampling period. It was able to control the charge of capacitance in real-time, and reduced the neutral-point voltage variation. For the convenience of hardware realization and decrease narrow pulse generation, the control factor k was classified. Finally, the effectiveness of proposed approach was confirmed via Simulink simulation results.
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