Power System Operation, Planning, and Economics

This sub-program focuses on optimal decision-making in the power system on time scales ranging from minutes to years. Decisions made on these time scales aim to economically ensure reliability and resilience of the power system and are often driven by electricity markets. Sandia’s work in this area proposes and develops novel decision-making tools to address emerging challenges that include the increasing occurrence of natural disasters, the reduction of carbon emissions, and the introduction of new technologies that don’t fit into traditional power system operational procedures such as wind, solar, and storage.

Power System Planning for Resilience and Reliability

Flood Protection Sandbags with flooded homes in the background (Montage)

Sandia’s efforts in power system planning have focused on investments to improve resiliency and reliability subject to uncertain future threats.  The Threat and Impact Modeling sub-program assists in characterizing uncertain future threat that range from physical attacks to natural disasters such as hurricanes, earthquakes, cold waves, or flooding. Many different investment decisions are considered including the weatherization of generators, transmission line reinforcement, and temporary flood barricades to protect substations (as illustrated in the picture above).

In the context of power system planning, Sandia has developed stochastic multi-stage investment optimization problems along with algorithms that are capable of efficiently solving these problems.  These problem formulations include any combination of one or more of the following three stages:

  • Investment stage: Decisions for long-term investment that require years to implement and intend to function for decades.  These investments should ensure resilience and reliability of the power system. Examples include rebuilding old transmission infrastructure or building a protective enclosure around a generator to protect it from weather events.
  • Pre-emptive action stage: Decisions made in preparation of an upcoming and forecasted event such as a hurricane or winter storm.  These pre-emptive action decisions may include the spatial routing of Mobile Energy Storage Systems (MESSs) or temporary flood barriers that can be constructed quickly.
  • Restoration stage: Decisions made during the power system restoration process in response to an event. Restoration decisions include generation dispatch, transmission switching, and repair crew routing/scheduling. 

Power System Operation and Electricity Markets

Intra-day commitment and dispatch operations executed by Independent System Operators (ISOs) intend to economically ensure reliability of the power system.  Unit-Commitment (UC) and Economic Dispatch (ED) optimization problems are used to clear the day-ahead and real-time electricity markets.  On the other hand, Look-Ahead Commitment (LAC) optimization problems are used as advisory tools to guide emergency operations and do not clear a market.  Sandia has proposed and developed multiple innovations to these operations including the following:

  • Stochastic Look-Ahead Commitment (SLAC) advisory tool that considers multiple net load forecast scenarios rather than the deterministic LAC considered today.  Sandia has developed a progressive hedging algorithm that allows for parallel computation over the scenarios, allowing for efficient computation.
  • Economic and reliability metrics used to evaluate the performance of newly proposed features introduced to power system operations. The developed metrics include simulation-based reliability metrics that model the interaction between the UC, ED, and LAC and economic metrics such as system-wide costs and out-of-market uplift payments to market participants.
  • New reserve types introduced into the UC and ED problems along with corresponding reserve products in ancillary services markets.  For example, some ISOs have recently introduced new frequency response reserve products provided by fast acting inverter-based resources that intend to help accommodate low system inertia levels.
  • Operating Reserve Demand Curve (ORDC) innovations that more accurately account for net-load uncertainty.  The proposed ORDCs represent expected costs of reserve shortfall, remove the common assumption that reserve error is Gaussian, and are used to set reserve and energy prices.  The proposed ORDCs would improve power system reliability by more accurately procuring reserve quantities.
  • Efficient algorithms to solve the UC problem that allow for parallel computation over the UC time intervals, allowing for finer time increments to be represented in the UC problems.

Manuel Garcia