我国早期建成的众多中小型水电站多已出现技术水平落后，设备老化，能效逐年衰减等诸多问题。这不仅未能充分利用宝贵的水资源，而且存在诸多安全隐患。目前中小水电增效扩容的关键技术研究多聚焦于发电机组与水能资源配置的优化，鲜有对原建筑形式进行优化。本文结合衡阳白渔滩电站增效扩容的实践，从理论上分析了进水口拦污栅水头损失的特征，提出了一种机组优化结合进水口结构优化达到电站增效扩容效益最大化的改造新思路，并介绍了进水口优化的施工方案，丰富了中小电站增效扩容方法，对后续类似电站的增效扩容提供了可靠经验。

Many small and medium-sized hydropower stations built in early years of China have encountered problems such as backward technology, aging equipment and declining efficiency. This not only fails to make full use of valuable hydropower resources, but also leave many security threats. The present study on key technologies for efficiency?improvements?and?capacity?additions?focuses on the optimization of the configuration of generator sets and hydropower resources. Research on achieving fuller utilization by means of optimizing the original hydraulic structure is rarely seen. Based on the efficiency?improvements?and?capacity?additions practice of Baiyutan Hydropower Station (Hengyang), this paper theoretically analyzes the characteristics of the water head loss of the inlet trash rack, and proposes a new method to maximize the station efficiency combining the optimization of the generator set and the inlet structure. This paper also introduces the construction scheme of the inlet structure optimization which hopefully will enrich the methods of efficiency?improvements?and?capacity?additions at?existing?small and medium-sized hydropower stations, and provided reliable experience for the subsequent cases.