Cascade Hydropower Stations Joint Optimal Dispatch And Decision-making Method

As a complex nonlinear large scale system, the cascade hydropower stations joint optimal dispatch system has the inherent characteristics of high dimension, multi-objective, strong coupling relationship, uncertainty, and complex constraints, and thus is always concerned by researchers. Nowadays, with the continued exploitation of river basin hydropower, the number of hydropower stations is growing up, and the hydraulic and electric relationship between hydropower stations is further enhanced. Hence, the conflict between the complexity of the problem and the limitations of solving methods is more prominent. Traditional optimal dispatch and decision-making methods are confined to isolated hydropower stations, single objective, and rigid decision-making, which has been unable to meet the demands of operation and management of cascade hydropower stations. Therefore, it is needed to develop new optimization theories and decision-making methods, and enhance the ability to solve practical problems. In this paper, aimed at the characteristics of the cascade hydropower system, we deeply study the theories and methods of the cascade joint optimal dispatch and decision-making by adopting the complex systems engineering theory, swarm intelligence algorithm and multi-objective decision-making theory, and obtain a series of conclusions with theoretical and practical value, some of which have been successfully applied to the Three Gorges project. The main research and innovative results are as follows:(1) Focus on the complex characteristics of hydrothermal power system which contains the cascade hydropower stations, a novel algorithm-Shuffled Particle Swarm Optimization (SPSO) is presented. The SPSO can overcome the shortages of the Particle Swarm Optimization (PSO), such as slow convergence and easily getting rid of local extremum, and it has higher solution accuracy than PSO and Shuffled Frog Leaping Algorithm (SFLA). Furthermore, we apply the algorithm to the complex hydrothermal power system short-term optimization problems, and propose a double fitness constraints treatment approach. The results demonstrate that the SPSO has high calculation accuracy and good convergence in solving the problem. The double fitness constraints treatment approach can effectively handle the complex system constraints and make the calculation results rapidly converge to the feasible space. Thus it can be provided as an effective alternative for solving the complex power system optimization problems. (2) According to the characteristics of multi-objective problems, a Multi-objective Shuffled Particle Swarm Optimization (MOSPSO) is presented by further expand the proposed SPSO algorithm. The core contents of the MOSPSO include a new archiving strategy based on self-adaptive niche method, and the population sorting approach and memetic evolution process based on the Pareto domination relationship. The numerical experiments indicate that MOSPSO can yield better-spread solutions and converges closer to the true Pareto frontier compared to some representative multi-objective evolutionary algorithms.(3) In view of the multi-objective joint dispatch requirements with the Three Gorges cascade project completion, we establish the multi-objective power generation dispatch and multi-objective flood control models based on MOSPSO for Three Gorges cascade. Additional, the suitable algorithm coding method and constraints handling approach are proposed based on the constraints corridor and punish functions, which can improve the capacity of constraints treatment and the models convergence efficiency. After multi-objective optimal calculation with the different typical influx, the non-inferior solution sets are obtained, and can be provided as reliable data for the final multi-attribution decision. The non-inferior solution sets also reveal the change rules of objects.(4) It's the final target of multi-objective dispatch and decision-making to determine the optimal scheme scientifically and reasonably. On the basis of the advantages of entropy method and Vague set theory, a novel Vague set decision-making method based on modified entropy method is proposed. This method overcomes the shortage of basic entropy weight calculation formula, and uses the Vague value referred to the ideal scheme to accurately describe the optimal degree of the alternative solutions. Furthermore, by applying the proposed method to solve the Three Gorges cascade multi-objective power generation and flood control decision-making problem, we obtain the optimal power generation and flood control schemes with different trend of benefits and risk and clarify the hydraulic and electric relationship of the cascade hydropower stations, which are useful to the rapid and scientific decision for the Three Gorges cascade dispatch.