Trans-Provincial Absorption And Peak Shaving Scheduling For Large-Scale Hydropower Systems In Southwest China

Power grid with high proportion of hydropower has formed in southwest China. When large and small hydropower plants (LHPPs and SHPPs) in that area are bundled for transmission, severe water spills for hydropower frequently occur and power grid security is threated during the flood season because of limited transmission capacity. How to coordinated operation among LHPPs and SHPPs in the area for achieving greater total electricity absorption and reducing spilled water electricity, that is a key issue of large-scale hydropower system scheduling in Southwest China. There are the hydropower enrichment areas in China that reverse distribute to the electricity demand. The large-scale hydropower distance transmission is inevitable. Two kinds of transmission mode:One is cascaded hydropower plants transmission mode in the same grid scheduling platform, such as hydropower plants in China Southern Power Grid. Second is hydropower transmission model of UHVDC, such as East China Power Grid. For the former one, mainly studied long-term coordinated optimal operation method for an integrated system of LHPPs and SHPPs, operation method of integrated LHPPs and SHPPs systems under small hydropower output uncertainty; For the latter problem, mainly studied large-scale hydropower in southwest China transmission impact on power grid peak shaving. The studies are based on actual engineering background and proposed for the practical engineering problems. The main innovation contents are as follows:(1) Long-term coordinated optimal scheduling for large and small hydropower absorption under multistage transmission constraints. The maximizing the total electricity absorption was selected as the objective. A coordination solution framework with LHPPs and SHPPs was built for remission transmission congestion, and a search algorithm was used to solve the model via make the high-dimensional problem transform into low dimensional. A case study of the Mojiang in Yunnan Power Grid was conducted. The result shows that the proposed method can handle complex transmission constraints, and use the different regulation ability of LHPPs and SHPPs to achieve greater total electricity absorption and effectively reduce spilled water electricity.(2) Operation method of integrated LHPPs and SHPPs systems under small hydropower output uncertainty. The small hydropower plant (SHPP) generation is uncertain, which has a great influence on the hydropower system scheduling. A scenario analysis method was used to deal to the uncertainty of small hydropower, and constructs power scenario sets for description power characteristics of SHPP. And fuzzy clustering and clustering comprehensive quality algorithm were proposed for reduction scenarios while establishment the conditional probability distribution of forecast and actual power under the current prediction accuracy. The minimum of expected maximum remaining load was selected as the peak shaving objective. The similarity was analyzed between the current forecast power and prediction scenarios in order to discriminate prediction scene category and obtain possible actual scenarios in the future. Then, a successive search algorithm was proposed to solve the model. The proposed method is useful for improving expect peak shaving effect and reliability of hydropower schemes.(3) Long-term typical day peak load regulation energy maximization model for trans-provincial hydropower plants systems. The minimization of the maximum remaining load of typical day was selected as objective, that was dealt with by a coherency function and fuzzy choose method. A long-term operation and typical day power scheduling are integrated into one model that was solved by a progressive optimality based algorithm, load reconstruction method, successive cutting load method and load distribution method. The proposed method not only can satisfy the requirement of the grid energy balance, but also can satisfy the requirement of the grid power balance. It makes the scheduling plan is more practical, and improves accuracy scheduling level for power grid operation.(4) Coordination method of regional and provincial grids for peak shaving operation among UHVDC hydropower and provincial hybrid energy sources. The power transmission plan of UHVDC is straight line or other unreasonable way, which can increase the power grid load pressure. How to coordinate regional and provincial grids for peak shaving operation among UHVDC hydropower and provincial hybrid energy sources is a new problem. The power grid load was selected as associated factors, and proposed a heuristic search algorithm, a successive search algorithm, and improved load shedding algorithm for UHVDC, pumped-storage, conventional hydropower, thermal and nuclear operation. Then, the solution to the moreover, the quadratic programming method was used to allocate electric power among provincial grids after obtaining the generation schedule of each plant for optimizing the demand of peak shaving. The proposed method can effective coordination of multiple provincial power grid peak load demand, and better play a role of UHVDC for power grid peak shaving.