Part 2: Ensuring Adequate Generation Supply
Many utilities struggle to deal with achieving adequate generation supply as the system approaches Real-Time operation. In my previous blog post, I covered generation supply adequacy for these four distinct time horizons:
In today’s blog post, I will focus on generation scheduling, or generation adequacy, in the Near Real-Time and Real-Time time horizons.
Presently in North America, there are two utility models:
- Restructured (e.g., California and Ontario)
- Partial Restructuring, or sufficient restructuring, with a Vertical Integration Utility model to offer non-discriminatory transmission service (e.g., British Columbia and Quebec)
Regardless of the utility model, the generation scheduling objectives and processes are similar as they focus on ensuring there is sufficient generation to reliably operate the system in different time frames.
Near Real-Time Generation Scheduling
Near Real-Time time scheduling deals with implementing the necessary changes in selecting the most economic generation portfolio (unit commitment) within a day or a few hours, and the optimum set point for the units (economic dispatch) to supply that load for actual operation.
Near Real-Time generation scheduling provides more time for posturing the system to ensure sufficient supply and system reliability. Near Real-Time scheduling has a time frame of many hours to days. During this period, operators take into account the start time and the ramping rates of the generators that need to be supplying load in Real-Time. Operators should also develop Near Real-Time schedules for regulation reserve, slow reserve, and fast reserve requirements to ensure that the units providing these reserves are ready for their operation in Real-Time.
In a Restructured Utility model, there are normally Day Ahead markets for energy and ancillary services. In the Day Ahead market, 24-hour price and generation schedules are calculated for posting beginning at midnight, 18 to 24 hours ahead of time for system posturing. In a Partially Restructured model, hourly generation schedules are provided to operators for the next day by the utility’s generation group, as well as all the Independent Power Producers, for system posturing.
Real-Time Generation Scheduling
Real-Time generation scheduling provides opportunities for operators to revise the Near Real-Time schedules and posture the system to ensure sufficient supply and system reliability. Real-Time scheduling ensures optimal schedules, considering the projected real time operation load, transaction schedules, transmission constraints, as well as reserve sufficiency.
In the Restructured Utility model, there are normally Real-Time markets for energy and ancillary services with intervals as short as five to ten minutes, and a shorter look-ahead horizon between one to three hours. In a Partially Restructured model, operators use the most economic generation schedules to minimize the utility costs while satisfying the reserve requirements and transmission constraints.
Technology for Generation Scheduling
Regardless of the utility model, the generation scheduling process needs a sophisticated generation scheduling and optimization solution dealing with forecasting, optimization, and scheduling of conventional resources, as well as a Distribution Energy Resources (Distributed Energy Resource Management System [DERMS]). These solutions can be adapted to work with different electricity and ancillary services markets, as well as the conventional generation portfolio optimization and scheduling in a conventional utility model.
In the third and final blog post for this series, I will discuss microgrid generation scheduling and how it can be supported with microgrid optimization software.
About the author:
Dr. Ebrahim Vaahedi is Senior Director of Microgrid & GridControl Software Development at OATI. Dr. Vaahedi has more than 30 years of experience in different segments of the energy industry, specializing in the development and execution of technology strategies for utility industry. Dr. Vaahedi joined OATI following his prior position with a major Canadian utility as Chief Technology Officer, where he was accountable for developing and executing a consolidated technology plan, including the delivery of a $140 million Control Center project. Dr. Vaahedi is the author of a recent book on modern power system operation, titled “Practical Power System Operation.” Dr. Vaahedi earned his B.S. in Electrical Engineering from the Sharif University of Technology in Tehran and went on to earn his M.S. in Power Systems and Electrical Machines and Ph.D. in Optimal Control of Power from the Imperial College of Science and Technology in London.