Transformerless Single-Phase Multilevel-Based Photovoltaic Inverter
Transformerless Single-Phase Multilevel-Based Photovoltaic Inverter
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DOI：
10.1109/tie.2008.924015
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发表时间：
2008-06
影响因子：
7.7
通讯作者：
R. González;E. Gubía;J. L. Taberna;L. Marroyo
中科院分区：
文献类型：
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作者：
R. González;E. Gubía;J. L. Taberna;L. Marroyo
光伏并网发电系统中省去了输出变压器，不仅降低了转换级的成本、体积和重量，而且提高了系统的整体效率。然而，如果移除变压器，光伏发电机和电网之间的电流隔离就会丢失。在发生接地故障时，这可能会造成安全隐患。此外，漏电流(共模电流)通过光伏阵列和接地之间的杂散电容循环也将成为可能。此外，当不使用变压器时，逆变器会向电网注入直流电流，导致沿配电网的变压器饱和。虽然无变压器系统的安全要求可以通过外部元件来满足，但泄漏电流和向电网中注入直流必须从拓扑上或通过逆变器的控制系统来保证。本文提出了一种新的无变压器系统高效拓扑结构，该拓扑结构不产生共模电流，并在拓扑上保证不向电网注入直流。所提出的拓扑结构已经在5kW的样机上得到了验证，取得了令人满意的结果。
The elimination of the output transformer from grid- connected photovoltaic (PV) systems not only reduces the cost, size, and weight of the conversion stage but also increases the system overall efficiency. However, if the transformer is removed, the galvanic isolation between the PV generator and the grid is lost. This may cause safety hazards in the event of ground faults. In addition, the circulation of leakage currents (common-mode currents) through the stray capacitance between the PV array and the ground would be enabled. Furthermore, when no transformer is used, the inverter could inject direct current (dc) to the grid, causing the saturation of the transformers along the distribution network. While safety requirements in transformerless systems can be met by means of external elements, leakage currents and the injection of dc into the grid must be guaranteed topologically or by the inverter's control system. This paper proposes a new high-efficiency topology for transformerless systems, which does not generate common-mode currents and topologically guarantees that no dc is injected into the grid. The proposed topology has been verified in a 5-kW prototype with satisfactory results.