The Scheduling Methods For Steelmaking-continuous Casting Under Time-of-use Tariffs

The steelmaking-continuous casting is the core process in the production of steel industry.Its scheduling can improve manufacturing efficiency and reduce the production costs.The process consumed a variety of energy media.With the in-depth implementation of green manufacturing policy,the proportion of electric energy consumption with the characteristics of economic,practical and clean gradually increases.The power supplies of steel plants are also getting tighter.Demand response(DR)can effectively maintain the balance of power supply and demand,and the stable operation of power grid.Time-of-use(TOU)tariffs and electrical load tracking are different DR programs based on price and incentive,respectively.Double-position refining furnace is widely used due to its obvious advantages.For the complex problem of steelmaking-continuous casting scheduling under TOU tariffs,considering that there are few studies on electric load tracking and double-station refining furnace,this paper mainly studies these two aspects.A mixed-integer nonlinear programming(MINLP)model based on continuous time representation for electrical load tracking steelmaking-continuous casting scheduling problem under TOU tariffs is established to reduce the penalty caused by the deviation load and electricity costs.To solve problems that variable increases,the complicated target calculation,a binary variable and an offset time are introduced,which can deduce the objective function of power penalty and power consumption within a single load interval in general and improve the universality of the model.To overcome shortcomings of strength Pareto evolutionary algorithm 2(SPEA2),the global search ability of model is poor,easy to fall into local optimum.AHSPEA2 is proposed,which based on the arithmetic crossover operator and the hybrid adaptive mutation operators.The experimental results show that AHSPEA2 can find highquality scheduling solutions in a short time,and Pareto solution set is of good stability and convergence.The optimal solution is effective in reducing electricity costs and deviation load penalties.A scheduling optimization model of steelmaking-continuous casting with multiposition refining furnace under TOU tariffs,the objective is the weighted sum minimization of completion time,machine idle time and total electiricty costs,the constraint with double-position characteristics.When solving such NP-hard problems,Lagrangian relaxation algorithm can obtain high-quality solutions in a short time.Therefore,Lagrangian relaxation algorithm based on subgradient method is adopted to solve the model.The job processing sequence constraint is relaxed,and the inner point algorithm is used to solve the relaxation problem.The solution is not feasible because it violates the relaxation constraint,and can only be used as the lower boundary of original problem.A feasible optimal scheduling scheme is obtained as the upper bound through heuristic algorithm.The Lagrangian multiplier is iteratively optimized by using a subgradient algorithm to optimize upper and lower bounds constantly.It shortens the dual gap between upper and lower bounds and finally gets an approximate optimal solution of original problem.It finds that the steelmaking-continuous casting optimization scheduling with double-position refining furnace can reduce more completion time of charges,idle time of machines and total electricity costs than nondouble-station one.The research work in this paper can promote the research of steelmakingcontinuous casting production scheduling,and provide a new model and method such as AHSPEA2 and Lagrange relaxation to solve scheduling problem.It is of guiding significance for other energy-intensive industries.