CHENG Dong-liang, WANG Xiao-peng, ZHU Tian-liang, MA Wen-gang
（School of Electronic and Information Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China）
Abstract： The topology of diode neutral-point-clamped (NPC) three-level inverter is prone to neutral-point potential offset. When the sum of three-phase current is zero, the virtual space vector pulse width modulation (VSVPWM) scheme does not cause the neutral-point voltage offset, but it lacks the ability to balance the deviation. For this reason, a neutral-point potential control strategy combining virtual space vector modulation and loop width control is proposed. The neutral-point potential is balanced by introducing the distribution factor for the regions with redundant vectors. For other regions, the potential is controlled by selecting a suitable switching sequence. Meanwhile, the effect on the virtual vector modulation is reduced within the loop width by setting an appropriate loop width, thereby improving the balance effect. The simulation results show that the proposed method has a strong ability to control the offset and has excellent potential balance performance under the conditions of balanced load, unbalanced load and asymmetric capacitance parameters.
Key words： three-level inverter; virtual space vector pulse width modulation (VSVPWM); neutral-point potential balance; switching sequence
CLD number： TM464 Document code： A
Article ID： 1674-8042（2018）04-0397-08 doi： 10.3969/j.issn.1674-8042.2018.04.014
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基于虚拟空间矢量脉宽调制的三电平逆变器中点电位平衡控制策略
程东亮， 王小鹏， 朱天亮， 麻文刚
（兰州交通大学 电子与信息工程学院， 甘肃 兰州 730070）
摘 要： 二极管中点钳位型三电平逆变器的拓扑结构容易出现中点电位偏移问题。 当三相电流之和为零时， 采取虚拟空间矢量调制(Virtual space vector pulse width modulation, VSVPWM)的方法不会造成中点电压偏移， 但其缺乏对偏移进行平衡的能力， 为此， 提出了一种虚拟空间矢量调制与环宽控制相结合的中点电位控制策略。 该方法通过引入调节因子对存在冗余矢量的小扇区进行中点电位平衡； 对于缺乏冗余小矢量的小扇区， 则选择合适的开关序列进行电位的控制； 同时， 设置合适的环宽， 在环宽内减小对虚拟矢量调制的影响， 进而提高平衡效果。 仿真结果表明该方法具有很强的控制电位偏移的能力， 在对称负载、 非对称负载以及非对称电容参数的条件下都有很好的表现。
关键词： 三电平逆变器； 虚拟空间矢量脉宽调制； 中点电位平衡； 开关序列
引用格式： CHENG Dong-liang, WANG Xiao-peng, ZHU Tian-liang, et al. A neutral-point potential balance control strategy for three-level inverter based on VSVPWM. Journal of Measurement Science and Instrumentation, 2018, 9(4)： 397-404. ［doi： 10.3969／j.issn.1674-8042.2018.04.014］
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