Economic Scheduling of a Power System: a Cost Optimization Model

Economic scheduling of a power system: A cost optimization model

Supply of electricity must equal demand, at all the times. These aspects made the operation and planning of electricity system a complex matter especially in the context of minimizing cost of power without compromising on reliability.

Models are necessary to optimize the daily operation of power systems known as unit commitment. Optimization models are required to determine which generating units would be generating electricity to operate at lowest cost. In the context of liberalized market, these models are required to determine strategic decision concerning generation; bidding strategy etc for individual organisation to maximize revenues.

Scope of work:

The scope of work is limited to the 900MWe cogeneration power plant of Essar Oil Refinery. The purpose of the unit is to supply steam and power to the refinery as well to the national grid. Topics to be addressed in the projects:

1. Cost optimization with constraints within the framework of sustainable; reliable and efficient landscape.

2. Transmission system effects

3. Scheduling with limited energy supplies

4. Unit commitment problems and its constraints

Problem Identification:

The cogeneration power plant has three Oil/Gas-fired boilers, two heat recovery steam generators (HRSG) and two coal-fired boilers. These boilers are delivering steam at various pressure levels and meets the demand of steam in the refinery as well steam turbines for power generation. These units require refinery fuel oil, natural gas, naphtha, coal and LCO for power generation. Coal and natural gas are procured from markets whereas fuel oil, naphtha and LCO are refinery product.

Due to variation in fuel prices; its availability and complexities in the operation of cogeneration plant, it is very difficult to optimize the power and steam cost without any mathematical models.

In unit committed problems minimum operating points; minimum up and down times and start up cost etc plays an important role in defining the allocation of load to various units. Without a mathematical model for the same, it is very difficult to plan for maintenance, stoppage or start-up of any unit with variation in demand without affecting the reliability and spinning reserve.

Methodology/Approach:

The methodology will be to develop an optimization model. These models are characterized by a single objective function with various technical constraints as discussed above. This demands for a high level of technical detail and will be incorporated in the model.

Unit commitment problem can be solved by Priority list; Dynamic programming;