Inverters are the most vulnerable parts of the photovoltaic (PV) power plants. Therefore, choosing an appropriate inverter topology to maximize the reliability and availability of the PV power plants is very important, especially in the large scale power plants. This paper proposes a novel index named Total Financial Losses (TFL) to compare different inverter topologies from reliability and energy losses points of view. Initial cost, repair cost, financial losses due to the downtime and element losses, and environmental conditions are considered in evaluating the TFL index. Using this universal index, the optimal inverter topology and its switching frequency are determined when the TFL is minimized. Considering the fact that the reliability of power electronic devices is strongly dependent on their power losses and ambient conditions, the exact failure rates of vulnerable elements such as capacitors, switches, diodes, and cooling system are calculated. The system availability and frequencies of encountering the failure states are determined using the Markov method. Finally, the optimal photovoltaic inverter of the 150 kW power range is selected out of commonly used two-level and three-level topologies.

中文翻译：

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基于可靠性和成本分析的光伏多串逆变器拓扑优化选择

逆变器是光伏（PV）发电厂中最易损坏的部分。因此，选择合适的逆变器拓扑结构以最大化光伏电站的可靠性和可用性非常重要，尤其是在大型电站中。本文提出了一种新颖的索引，称为总财务损失（TFL），从可靠性和能量损失的角度比较了不同的逆变器拓扑。在评估TFL指数时，应考虑初始成本，维修成本，由于停机和零件损失引起的财务损失以及环境条件。使用该通用指标，可以在最小化TFL时确定最佳的逆变器拓扑及其开关频率。考虑到功率电子设备的可靠性在很大程度上取决于其功率损耗和周围环境，计算易损元件（如电容器，开关，二极管和冷却系统）的确切故障率。使用马尔可夫方法确定系统的可用性和遇到故障状态的频率。最后，从常用的两级和三级拓扑中选择150 kW功率范围的最佳光伏逆变器。