The Research Of Hydropower System Optimization Scheduling Methods To Respond Peak Shaving Demand

Most of China’s power grids are facing a huge pressure of peak shaving load. Particularly in East and Northeast China where the coal-fired power takes up the predominant position in power energy structure, the peak shaving operation problem is more serious. Hydropower’s low cost, near-zero pollution emissions and ability to quickly respond to peak loads make it become one of the most valuable power source of peak shaving load. So to carry out peak shaving operation method research of hydropower system has important theoretical guiding significance and engineering practical value for ensuring the security, stability and economy operation of China’s power grids. This research elaborates the key science and technology problems of peak shaving operation of hydropower system from three different point of view, including the basin side, power grid side and ultra high voltage direct current (UHVDC) interconnected power grid side. Based on the optimal control theory of Operations Research and the practical engineering background in Northeast China Power Grid (NCPG) and East China Power Grid (ECPG), this article research on long-term maximum peak shaving benefit for cascade hydropower plants with inter-basin water diversion system, model method of long-term peak shaving operation rules for cascade hydropower plants with hybrid pumped storage power plant, short-term heuristic method for peak shaving operation of pumped storage power plant among multiple interconnected provincial power grids and short-term peak shaving operation method of large-scale inter-district UHVDC hydropower with multiple conventional power source of receiving end power grid. The author has made some achievements for the theoretical guiding significance and engineering practical value and these achievements is summarized as follows:(1) Considering that complicated hydraulic connection and peak shaving demand are hard to be deal with for long-term optimal operation of cascade hydropower plants of inter-basin water diversion, a long-term optimal operation model based on the objective of maximum peak shaving benefit and hybrid search algorithm are presented for cascade hydropower plants of inter-basin water diversion. A peak price curve based on the typical daily load curve is simulated to construct a peak shaving operation model by power price. The Progressive Optimality Algorithm, Dynamic Programming Successive and Discrete Differential Dynamic Programming are coupled to solve the model. The practical results of Songjiang River cascade hydropower plants in Northeast China Power Grid show that the proposed model can play a powerful role in regulation and compensation ability among reservoirs and significantly improve peak shaving ability of original cascade hydropower plants during dry season. The present model is more applicable to shave peak demand in power grid which the thermal power takes up the predominant position.(2) To solve the long-term operation rules on cascade hydropower plants with hybrid pumped storage power plant (PSPP), combining peak shaving price curve and filling off-peak price curve, a long-term optimal operation rules model is proposed based on maximum peak shaving benefit as object and fire power as constraint. A water to energy converting model of hybrid PSPP is incorporated into the Stochastic Independence Dynamic Programming and Stochastic Correlation Dynamic Programming to solve the model according to strong historical runoff correlativity or weak, respectively. The practical results of the Second Songhua river cascade hydropower plants in Northeast China Power Grid show that the proposed model can consider the period correlativity and stochastic of runoff, and can reflect dual demand of power grid to the fire power and peak shaving benefit. The proposed model can give full play to the role of shaving peak and filling off-peak load by hybrid PSPP in electrical power system.(3) Considering that it is very difficult to respond to peak and off-peak load demands for multiple provincial power grids with PSPPs, a short-term peak shaving operation method is proposed to meet peak shaving requirements of multiple provincial power grids. The objective is to minimze the variance of remaining load series of each power grid. This paper develops a three-step hybrid algorithm for the day-ahead quarter-hourly schedules of PSPPs. A normalization method is first proposed to reconstruct a total load curve to deal with the load differences of multiple provincial power grid. Secondly, a heuristic search method is presented to determine the generating and pumping powers of PSPPs. Thirdly, a combination optimization method is used to allocation the determined generating and pumping powers among multiple provincial power grids. The practical results of the PSPPs typical daily operation in East China Power Grid show that the proposed model can efficiently search generating power and pumping power schedules of PSPPs and can reasonable distribute the schedules among multiple power grids to response peak and off-peak load demand.(4) Considering the complicated electricity transmission problem of large-scale ultra high voltage direct current hydropower (UHVDCH) in China, a short-term peak shaving operation method for the UHVDCH and multiple conventional power source of receiving end power grid is presented based on a practical problem. The original problem was decomposed into multiple sub-problems according to different power source type by the decomposition-coordination method of large scale systems. Especially for the UHVDCH, two kinds of control model, including control power and control energy, are proposed to solve the sub-problem of UHVDCH. For the control power model, a power distribution procedure of UHVDCH is only carried out. For the control energy model, a power transmission optimization procedure and power distribution procedure are carried out. Finally, the remaining load curve of each power grid as associated factor, all sub-problem solving methods are carried out recursively to determine the optimal results based on an assumed coordinated principle. The practical results of multi-level energy integrated optimization scheduling system of East China Power Grid show that the proposed model can give full play to peak shaving potential of UHVDCH and significantly improve peak shaving rate of East China Power Grid. The research result can provide the feasible theory method for China’s UHVDCH transmission problem in the present and future.Finally, some problems should be studied in the later work and learning process.