Self-scheduling for electrical energy balance and output power control of energy-intensive enterprises

Many energy-intensive enterprises own power plants themselves. Achieving balance of electrical energy consumption and supply through self-scheduling is very important to security and reliability of the power grid and often gets incentives from the power utility. Due the ramping limit of generating units and infeasible step-up change, a generation level schedule based on discrete-time model may not be realizable although ramp-rate constraints are satisfied in scheduling. This paper formulates a new model for balance analysis with integral constraints. Based on the detailed analysis of the admissible region of initial or terminal generation level and its relationship to scheduled energy delivery and ramp-rate constraints, the new model for balance analysis with integral constraints is converted into a mixed integral programming model. Based on the minimum principle in optimal control theory, a control method of unit power output is developed considering unit economics and security. Numerical testing is performed with the actual data of a large iron and steel enterprise and the results show that the model and the control method are effective.