## 1 Introduction  
In order to realize green development, flexible scheduling and the low-carbon transition of electric power, more renewable power started to be exploited and utilized in China following the new-round power market reform in 2015. Meanwhile, through the promotion of the electric power development plan in the 13 th five-year period, the installed capacity and consumption ratio of renewable energy will increase rapidly. By the end of 2016, the total power generation in China reached 614.25 GWh, an increase of 5.6% compared with the level in 2015 [1]. In the power supply structure, renewable energies, such as hydropower, wind power and solar power, accounted for 24.3% of total power generation. Among numerous power-generation types, distributed generation using renewable and clean energy has developed rapidly in recent years. Due to its advantages of being environmentally-friendly and easily consumed, there has been a focus on the distributed photovoltaic (PV) generation project which has been generalized widely. With data from National Energy Administration, China's distributed PV-generation capacity had a newly installed 34.54 GW in 2016, which shows its huge development potential [2]. However, China's distributed PV-generation industry is still in its infancy, so it is important to identify its real core ability in this complex generation environment in order to realize its sustainable development. From the competitiveness perspective in previous studies, the core ability of a generation project usually contains aspects of technology, cost and environmental effects [3; 4; 5]. However, their assessment have not been comprehensive and cannot meet the multi-objective development requirements of distributed energy at present. With this widely accepted viewpoint, the influences of distributed power-generation projects on the power grid and other generation types have been taken into account in recent studies [6]. In terms of basic concepts, attention to the core ability of distributed power generation has changed from reliability to flexibility [7; 8; 9]. More comprehensive benefits from distributed power generation have been focused on. Thus, the core ability of distributed generation projects needs to be refined and extended to multiple dimensions. In this paper, the core ability of distributed PV-generation project was defined as a comprehensive ability aiming at the goals of its economic operation, grid coordination, energy substitution, energy saving, emission reduction and demand satisfaction in a complex electric system. These abilities will be examined to help in the assessment of a distributed PV project's actual development level and provide optimal references for its sustainable development. It is imperative to construct the evaluation index system for the core abilities of distributed PV-generation projects systematically and find an effective evaluation method to examine practical projects scientifically, and this is the paper's most important contribution. Therefore, this study focuses on the evaluation of core abilities of distributed PV-generation projects. Based on the literature, feasibility reports and expert interviews, the evaluation indexes for core abilities of distributed PV-generation projects will be explored deeply. Then, by using combination weighting and techniques for order preference by similarity to an ideal solution (TOPSIS) evaluation methods, an evaluation model will be constructed scientifically and systematically. Finally, three experimental projects will test the effectiveness of the core abilities evaluation index and method. This exercise can provide management references for both the industry and enterprises. The model adopted in this paper can also provide an effective tool for assessing a distributed PV-generation project or other renewable generation projects.