A novel PV sub-module-level power-balancing topology for maximum power point tracking under partial shading and mismatch conditions

部分遮挡和串联模块(或子模块)的非匹配条件可在整个光伏系统中导致功率曲线非凸且出现多个局部极值和峰值功率下降的现象。通过功率传输,可将各子模块的工作电压拉平;这样的功率收集操作可生成凸功率曲线,提升光伏系统的峰值功率。本文所述拓扑结构受益于开关电容(Switched capacitor,SC)转换器的概念,是一种子模块级功率平衡概念的具体应用。与现有研究成果相比,其创新点包含无遮挡时停止开关操作、串联线路级可拓展性以及减少功率电子元件使用量。功率电子元件使用量的减少是通过两个子模块共享一个SC转换器的方式实现的,这也能带来降低功率器件能量损耗、降低成本和电路体积的优势。本文给出了所述拓扑结构的插入损耗的理论式,并通过PSpice仿真和原型电路的实验评估,证明了损耗理论解的正确性。这也表明,通过使用所述拓扑结构,有可能提取出部分遮挡的光伏线路的几乎所有可用能量,并将其传输至负载端。

Partial shading and mismatch conditions among the series-connected modules/sub-modules suffer from a nonconvex power curve with multiple local maxima and decreased peak power for the whole string. Energy transfer between the sub-modules brings them to the same operating voltage, and this collective operation produces a convex power curve, which results in increased peak power for the string. The proposed topology benefits from the switched-capacitor （SC） converter concept and is an application for sub-module-level power balancing with some novelties, including stopping the switching in absence of shading, string-level extension, and a reduced number of power electronics components as compared to those in the literature. Reduction in the number of power electronics components is realized by the fact that two sub-modules share one SC converter. This leads to reduced power electronics losses as well as less cost and volume of the converter circuit. Insertion loss analysis of the topology is presented. The proposed topology is simulated in the PSpice environment, and a prototype is built for experimental verification. Both simulation and experimental results confirm the loss analysis. This proves that with the proposed topology it is possible to extract almost all the power available on the partially shaded string and transfer it to the load side.