## 1 Introduction
### Research Status  
At this stage, domestic and foreign scholars have conducted numerous researches on the energy saving and emission reduction of the electric power industry in China. On the one hand, some researches laid particular emphasis on the power production technologies and power equipments [1; 2; 3; 4], qualitative assessment and quantitative analysis were carried out to evaluate the impact on energy saving and emission reduction by improving and applying those technologies and equipments. [PERSON] [1] analyzed the effects of energy saving and emission reduction for electric systems while using high-voltage frequency conversion technology, which proved that the appliance of this technology can help power plants to achieve a high-level energy saving. [PERSON] et al. [2] conducted the assessment of the effects of central heating supplied by large coal-fired power unit and then put forward relative measures to improve the energy efficiency. [PERSON] et al. [3] researched on the effects after the application of advanced equipments in the fields of power transmission and transformation. The use of switching equipment to achieve energy saving and emission reduction was put forward. [PERSON] and [PERSON] [4] proposed to realize the saving and emission reduction in the electric power industry through resource optimization configuration technology and implemented corresponding actions at the strategic level. On the other hand, most researches focused on the use of different comprehensive evaluation methods to assess the energy saving and emission reduction effects for the power plants [5; 6; 7; 8; 9; 10; 11; 12; 13; 14] and power grid companies [15; 16; 17; 18]. [PERSON] and [PERSON] [5] established an evaluation indicator system of energy saving and emission reduction technologies form the resource and energy consumption, pollutant discharge, economic benefits, and technical performance. Next, the interval-value comprehensive method was selected to assess the effects. [PERSON] [6] selected evaluation indicators according to the subsystems of energy saving and consumption reduction, pollutant discharge reduction, energy saving, and emission reduction relations of thermal power companies, then conducted the assessment. [PERSON] et al. [7]built an indicator system mainly reflected the actual production status of thermal power plants and evaluated the energy saving and emission reduction effects through grey correlation analysis method. [PERSON] and [PERSON] [8] chose the technical indicators of biomass power generation to finish the assessment. [PERSON] et al. [9] designed an evaluation indicator system for thermal power companies from two perspectives of energy saving and pollutant reduction. The effects were assessed based on entropy-weighted extentic method. [PERSON] et al. [10] adopted the way that combined factor analysis and DEA (data envelopment analysis) to analyze the energy saving and emission reduction effects of power generation enterprises. During the process of evaluating energy saving and emission reduction performance of power generation companies, [PERSON] [11] established the indicator system from six dimensions, including energy resource utilization, pollutant discharge, and efficiency improvement, etc. It also put forward the evaluation model based on network-level analysis method and improved gray clustering decision-making. The evaluation indicator system that is proposed by [PERSON] et al. [12] includes aspects, such as coal saving, electricity saving, water saving, and pollutant discharge, which could evaluate the status of emissions reduction of coal-fired power plant more comprehensively. [PERSON] et al. [13] utilized the indicators of consumption and emissions to have an integrated evaluation for power plants, which was carried out by means of entropy weight based on fuzzy matter element model. [PERSON] et al. [14] studied on the benefits of energy saving and emission reduction sides for domestic small hydropower ecological protection projects through econometric models.