A novel nonlinear method of analysis is deployed in detail with the aim to design suitable controllers with guaranteed stability for grid-connected photovoltaic (PV) systems driven by power converters. By this method, all the system nonlinearities are considered in order to allow a reliable analysis in a wide range of operation and to avoid instabilities that as shown in this article can be occurred by inappropriate design. To this end, first, a detailed accurate nonlinear dynamic model is presented for the PV system by including a cascade-mode control scheme. Then, considering the closed-loop system and incorporating the concept of input-to-state stability (ISS), a rigorous novel stability analysis is developed, which achieves to prove asymptotic stability of the desired equilibrium point. A multistep process is deployed, in which the control-loops operating in cascade-mode are involved. However, since the cascaded-mode control scheme and analysis is based on the time-scale separation principle, a systematic tuning method is conducted for the accurate gain selection of both inner-loop and outer-loop controllers, which is based on the construction of suitable Lyapunov functions. To further validate the overall analysis, experimental results are carried out.

中文翻译：

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非线性分析方法在电力电子变换器驱动并网光伏系统中的应用

详细介绍了一种新颖的非线性分析方法，旨在为功率转换器驱动的并网光伏（PV）系统设计具有保证稳定性的合适控制器。通过这种方法，考虑了所有系统非线性，以便在较宽的操作范围内进行可靠的分析，并避免了不适当的设计可能会导致本文所述的不稳定性。为此，首先，通过包括级联模式控制方案，为光伏系统提出了详细的精确非线性动力学模型。然后，考虑闭环系统并结合输入到状态稳定性（ISS）的概念，进行了严格的新颖稳定性分析，以证明所需平衡点的渐近稳定性。部署了多步骤流程，其中涉及以级联模式运行的控制环。但是，由于级联模式的控制方案和分析是基于时标分离原理的，因此基于内环和外环控制器的结构，进行了系统的调谐方法，以精确选择内环和外环控制器的增益。合适的Lyapunov功能。为了进一步验证整体分析，进行了实验结果。