基于SVPWM补偿优化的三电平NPC并网逆变器容错控制

为保证并网系统中三电平中点箝位（neutral point clamped，NPC）型并网逆变器单相桥臂短路或断路故障后持续运行，提出一种基于空间矢量脉宽调制（space vector pulse width modulation，SVPWM）的优化补偿型低共模电压容错控制策略。首先，通过分析故障后八开关三相逆变器（eight switch three phase inverters，ESTPI）拓扑开关状态对应的共模电压大小，确定参考电压矢量合成规则；然后通过一个基波周期内中点电流情况分析中点电位波动机理，进而对空间矢量合成进行调节补偿，并设计低通滤波器和滞环控制器进一步对补偿进行优化调整，保证并网电流质量的同时有效抑制了直流母线中点电位偏移。仿真结果表明，该容错控制策略能够实现三电平NPC并网逆变器单相桥臂故障后并网系统的稳定可靠运行，每个基波周期有三分之一时间的共模电压得到改善，优化补偿后的并网电流质量显著提高，且在并网电流突变时具备良好的控制特性。

Fault tolerant control of three-level NPC grid-connected inverter based on SVPWM compensation optimization

To ensure the operation of three-level NPC grid-connected inverter in a grid-connected system after single-phase bridge arm short circuit or open circuit failure, this paper proposes a fault-tolerant control strategy based on space vector pulse width modulation (SVPWM), which reduces the common-mode voltage and compensates for the three-phase output. First, the reference voltage vector synthesis rule is determined by analyzing the common mode voltage corresponding to the switch state of the eight switch three phase inverters (ESTPI), which is the topology of the NPC 3-level inverter with one phase failure. Then, the mechanism of neutral point potential fluc-tuation is analyzed by the neutral point current change in a fundamental wave period, then the space vector syn-thesis is compensated. The low-pass filter and hysteresis controller are designed to optimize vector synthesis compensation, so as to ensure the quality of grid-connected current and effectively control the neutral point po-tential offset of the DC bus. The simulation results show that the proposed fault-tolerant control strategy can re-alize the stable and reliable operation of the grid-connected system after single-phase bridge arm failure, the common-mode voltage can be reduced for one third of the period time, the quality of grid-connected current is improved significantly. The proposed controller also shows fine performances when the grid-connected current changes.