开关点预置的四桥臂三相逆变器的中线电感

对无中线电感的基于开关点预置四桥臂三相逆变器进行仿真研究，发现N桥臂在不平衡负载时流过很大的电流，且输出电压波形总谐波含量大，因此，提出在主电路中引入中线电感。在带不平衡负载的不平衡指标的约束下，通过理论推导得到最大中线电感的选取表达式。通过仿真分析，得到不同中线电感时逆变器的输出特性，以确定中线电感的最佳值。仿真和实验结果表明：中线电感的加入，减小了输出电压的零序谐波、总谐波含量及第四桥臂的开关电流，提高了变换器的效率，且在不平衡负载时有较好的输出电压对称性。

Midline Inductor of Four-leg Three-phase Inverter Based on Switching-node Preset

The simulation of four-leg three-phase inverter without midline inductor and based on switching-node preset is researched in this paper. Current of N bridge is large and total harmonic distortion of the output voltage is big when load is unbalance . To resolve these problems , one midline inductor is added in this inverter. Expression to calculate the maximal value of midline inductor under target of unbalance load is given by theory analyse. And output characteristics of inverter versus different inductors are gotten by simulation, so the best value of midline inductor can be selected. Due to the midline inductor, the efficiency of the inverter is improved, the zero-sequence harmonic and total harmonic distortion of the output voltage is reduced, output voltage is symmetrical too under unbalance load. Simulation and experiment verify these analysis.