Abstract: Abstract: A comprehensive decision-making method is proposed for GW-scale photovoltaic (PV) system integrated to power grid in this paper. A decision-making evaluation index system is established, in which main influence factors considered are security and stability, intermittence of PV, economy as well as extendibility. The improved fuzzy analytic hierarchy process (FAHP) and TOPSIS are applied to decide the weights for indexes and to select the best scheme respectively. The case study of 1 GW coastal mud flat PV system integrated into Shandong power grid indicates that the applying of improved FAHP omits the consistency test, which can take full advantage of the original datas and reflect merits as well as demerits of different schemes visually and rapidly combined with TOPSIS. 1. Introduction In recent years, PV curtailment in the western regions has become serious owing to the insufficient consumptive ability and transmission capability, resulting that the development of large-scale PV generation gradually transfers to the eastern regions such as coastal mud flat or coal mine collapse area PV system. In order to reduce the effect of GW-scale PV system integrated into power grid, the integration scheme should be analyzed. Therefore, this paper proposes a method of integration scheme decision-making for GW-scale PV system in the eastern regions. It mainly consists of two steps: preliminary screening and scheme selection. The screening method is put forward which can reduce the unnecessary work of scheme selection. According to the established decision-making evaluation system, the improved FAHP combined with TOPSIS is adopted to select the optimal scheme. 2. Comprehensive decision-making of GW-scale PV system integrated to power grid Some indexes of steady-state operation are picked out for preliminary screening so as to eliminate some schemes that can not meet the standards of the steady-state power flow distribution of the power grid and alternatives can be determined. Then, considering the influence factors of GW-scale PV system integrated to power grid, the decision-making evaluation system is established, as shown in Fig.1. It mainly contains four criterions: Security and Stability A, Intermittence of PV B, Economy C, and Extendibility D. Each criterion also includes the corresponding sub factors. The improved FAHP is applied to determine the weights, which can avoid the problem of disaccord of judgment matrices in the traditional AHP method and improve the accuracy of the weights. The TOPSIS is adopted to arrange screened schemes. 3. Case study The index calculation results of 1 GW coastal mud flat PV system integrated into Shandong power grid are shown in Table 1 (Scheme 1 has been eliminated by preliminary screening). It can be seen the indexes can be quantified easily. The omission of consistency test when using improved FAHP makes the establishment of weights more efficient and accurate. The results of scheme selection combined with TOPSIS are given in (1), which consider all the factors in the evaluation system and truly reflect the gap between schemes. 4. Conclusion This paper focuses on the decision-making process of GW-scale PV system integrated to power grid in the eastern regions. Some schemes which can not fulfill the requirements of steady-state operation of the power grid will be given up in advance. The evaluation system is established based on the understanding of the key influence factors and the optimal scheme can be determined by using improved FAHP combined with TOPSIS. Simulation results show that indexes are easy to be calculated, which is convenient for engineering application. The combination of the improved FAHP and TOPSIS makes the decision-making process efficient and reasonable. The proposed method in this paper has certain significance for improving the scientific, comprehensive and quantitative decision-making of GW-scale PV system integrated to power grid.