Nowadays, neutral point voltage (NPV) balancing control and leakage current (LC) reduction methods are considered to improve the reliability of transformerless three-level T-type (3LT ² ) inverter. Medium vector pulse width modulation (MVPWM) method can control the inverter operation to eliminate the LC; however, is powerless to balance the NPV. Alternatively, discontinuous PWM (DPWM) methods can be implemented to balance the NPV. In this article, a hybrid method for transformerless 3LT ² inverter is proposed to simultaneously minimize the LC and accomplish balancing control in case of NPV unbalancing. The proposed method applies MVPWM switching patterns to eliminate LC while the NPV is balanced. If the NPV becomes unbalanced, it applies specific switching patterns of the DPWM methods as alternative patterns to balance the NPV with minimal LC. Accordingly, the proposed method not only maintains the LC elimination advantage of the MVPWM method but also realizes the NPV balancing capability without any topology modification or adding electrical components. Noteworthy, even the NPV balancing is accomplished with minimal flow of the LC. The proposed method is carrier-based PWM, which shortens execution time and simplifies practical implementation. Experimental tests have been accomplished and results demonstrate the effectiveness of the proposed method on adding the NPV balancing capability with minimal LC to the MVPWM method.

中文翻译：

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一种消除光伏三电平T型逆变器漏电流和平衡中性点电压的混合方法

目前，中性点电压（NPV）平衡控制和漏电流（LC）降低方法被认为是提高无变压器三电平T型（3LT ² ）逆变器的可靠性 。中矢量脉宽调制（MVPWM）方式可控制逆变器运行，消除LC；然而，却无力平衡 NPV。或者，可以实施不连续 PWM (DPWM) 方法来平衡 NPV。在本文中，无变压器 3LT ²的混合方法 逆变器被提议同时最小化 LC 并在 NPV 不平衡的情况下完成平衡控制。所提出的方法应用 MVPWM 开关模式来消除 LC，同时 NPV 是平衡的。如果 NPV 变得不平衡，它会应用 DPWM 方法的特定开关模式作为替代模式，以用最小的 LC 平衡 NPV。因此，所提出的方法不仅保持了 MVPWM 方法的 LC 消除优势，而且无需任何拓扑修改或添加电气元件即可实现 NPV 平衡能力。值得注意的是，即使是 NPV 平衡也是通过最小的 LC 流量完成的。所提出的方法是基于载波的PWM，它缩短了执行时间并简化了实际实现。