A New Strategy For Short-Term Scheduling Optimization Of Cascaded Hydro Plants Based On Chance-Constrained Programming

Remarkable economic and social benefit is achieved by the optimal scheduling of cascaded hydroelectric power plants. With the problem of energy shortage and the achievements in recent liberalization of the electricity market, it is necessary to make full use of hydropower, and improve its quality and benefit for adjusting energy structure and carry sustainable development strategy into execution. This paper presents a hybrid particle swarm optimization (HPSO) algorithm, short-term scheduling optimization of cascaded hydro plants, and short-term scheduling optimization of thermal power systems with risk management. The achievement of this paper is capable of providing significant reference value for utilizing cascaded hydroelectric power plants effectively and promoting comprehensive benefit of power system.To maximize the possible total objective profit throughout a time period, a novel strategy for short-term scheduling optimization of cascade hydro plants is presented based on chance-constrained programming in which the constraints are met with a specified probability. The detailed representation of cascade hydro plants, which includes water volume, water inflow, water discharge, forebay elevation, tailrace elevation and effective water head, is studied in the proposed strategy. The uncertainties, such as water inflows, electricity prices and unit status are taken into account as well. The two conflicting targets of profit and risk are coordinated preferably according to the practical system, and the optimization of power output for cascade hydro plants is established by the method developed.A novel model of risk management for short-term scheduling optimization of hydrothermal power system based on chance-constrained programming is presented in this paper. Coordinated relationship between day-ahead trading and real-time trading, operational constraints of hydrothermal power system, and uncertainty in hydrothermal power system are considered in an integrated fashion. This proposal model increases generation benefits of hydro electric power plants, reduces operation costs of thermal power plants, advances comprehensive benefits of power systems, and provides a novel research thought for hydro thermal power systems short-term optimal scheduling problem.To overcome the short coming of easily local optimum of PSO, a hybrid particle swarm optimization (HPSO), in which the catastrophe theory and chaos optimization was embedded into PSO, is also presented in this paper. Since the ideas of PSO and catastrophe theory are inspired by natural concepts, it provides an idea that the stagnation of evolutionary strategies of PSO may be described by catastrophe theory. The logistic map of chaos is used to disjoin the particles, which are close to each other around a local minimum according to the ergodicity, stochastic property and regularity of chaos. The definition of global convergence of stochastic algorithm is defined in the paper, and the algorithm presented is proved to converge to the global optimization solution with probability one using Lebesgue measure. The improvement of community diversity and searching space of PSO is achieved, and the proposal strategy is a simple effective approach to solve nonlinear programming problem with complex constraint conditions. The model presented is solved using a combination of HPSO and Monte Carlo simulation because of the advantages of HPSO such as simple concept, easy implementation and robustness. The results have showed that the combination of HPSO and Monte Carlo simulation for short-term scheduling optimization of cascade hydro plants is versatile and efficient.