Research On Optimal Operation Of Large-middle Scale And Small Hydropower With The Constraints Of Transmission Capacity

According to economic demand and state development tactic, hydropower in the southwestern China where are abundant in water resource, especially small hydropower has been explored rapidly. It counts a rather proportion of generation capacity for electricity in grids, responsible for the conduct of West-East Power Transmission together with traditional large scale hydropower. However, the relatively slow establishment of transmission facilities compared with increasing power plants as well as the disturbance of low-voltage access from small hydropower results in transmission congestion and spillage. Meanwhile the weak regulation ability of small hydropower accelerates the spillage during wet season. To solve above problems, it is necessary to optimize the hydropower system scheduling. But traditional optimization methods cannot apply in numerous and extensive small hydro plants with limited data, which suffer spillage caused by restriction of transmission capacity on complex transmission section. Furthermore, it is critical to offer guideline for grids planning by criteria of recognizing transmission capacity limitation on transmission section. Based on the analysis of massive small hydro plants, this paper focused on optimization of coordination scheduling between small hydropower and large scale hydropower as well as the relationship between absorption of hydropower and transmission capacity. The results are concluded as follows:(1) To coordinate with large scale hydropower while massive small hydro plants are connecting the power grids, this paper presented an optimization model of limited transmission between small hydropower and large-middle scale hydropower in separate areas, considering the maximum absorption of hydroelectricity as the optimal objective under the constraints of transmission capacity. It proposaled an algorithm to calculate spillage ensures maximum absorption, which avoid setting spillage output as decision variable. The experiments at Dehong area in Yunnan illustrates the given model could effectively facilitate the absorption of hydroelectricity while satisfying the limitation of transmission capacity.(2) To ensure the fair generation planning while generation capacity is bigger than transmission capacity based on non-market environment, this paper presented an optimization model for coordination scheduling between small hydro plants and large-middle hydro plants considering with index for measuring fairness, which prioritize absorption as main objective while fairness as subordinate objective. From both the overall and local view, this paper introduced heuristic method to allocate spillage in the local optimization model, which avoids spillage output as decision variable.(3) To evaluate the revenue after expending flexible transmission capacity for massive small hydro plants, this paper established a linear regression model for average load of small hydro plants and inflow of near large-middle hydro plants during the same time, which effectively extends the data of generation capacity by small hydro plants. Based on the long series spillage calculation, it presented a method to realize the relationship between increasing annually average absorption and transmission capacity on transmission section. The projects in Dehong show that such model and method could offer references for evaluation of revenue by extending transmission capacity.Finally, it summarized the research conducted for this paper, and outlook for further study.