Modeling and Control of Electric Loads for Ancillary Services and Decarbonization

Abstract

Towards decarbonizing power systems and achieving sustainability goals, traditional power plants, such as coal fired power plants, are being phased out and replaced with renewable generation alternatives. Historically, synchronous generators of traditional power plants provided much of the essential load balancing services required to match scheduled generation and demand, ensuring power system reliability. Hence, with the sunsetting of traditional generation, new sources of load balancing flexibility are needed. Furthermore, the inherent intermittent and variable nature of renewable generation typically requires an increase in the load balancing services needed. Aggregations of electric loads, such as thermostatically controlled loads (TCLs), hold substantial potential to offer this flexibility, given their thermal inertia and ubiquity.

TCLs are an ubiquitous resource with inherent temporal flexibility that allows them cycle on/off and consume power in cycles. This flexibility can be leveraged for power system objectives. The abundance and spatial distribution of TCLs make them a prime and valuable candidate to provide flexibility to the power grid.

This dissertation develops models and control algorithms for leveraging the flexibility of TCL resources and practically demonstrates the ancillary service and decarbonization potential of these loads. Building on established hierarchical load control methods, a novel device-driven approach for coordinating aggregations of TCLs is created. The developed control design was tested and validated via simulations and hardware-in-the-loop (HIL) experiments. Also, communication architectures enabling cyber-physical demonstrations of load control for frequency regulation were developed.

In this dissertation, the state-of-the-art device-driven packetized energy management (PEM) aggregate load control strategy, which coordinates only thermostatic loads without compressors, is improved upon to create a new device-driven method that enables coordination and control of all classes of thermostatic loads. The new control approach when compared to the state-of-the-art PEM, significantly improves control flexibility and signal tracking performance with the load aggregation. It is demonstrated with simulation and HIL experiments that the newly developed device-driven control is able to satisfactorily (according to industry standards) provide up to 1 MW capacity of frequency regulation balancing service using about a thousand residential air conditioners. An aggregate model of the new device-driven strategy that can be used for predictive control and analyzing system dynamics is also developed.

There exists significant efforts to decarbonize by replacing fossil-fuel dependent systems like space heating with electric heat pumps, appliances such as dryers and water heaters, with electric versions. The transition to electrified homes is crucial for climate goals but requires precise evaluation methods to understand energy, economic, and environmental impacts. A systematic review of energy modeling approaches, used in electrification and decarbonization impact assessments, is also presented in this dissertation.

Overall, this dissertation attempts to establish credibility for aggregate control of electric loads in providing power system balancing services and harnessing the decarbonization potential of load electrification. This dissertation identifies and overcomes challenges involving electric load aggregations, showing they can indeed provide the additional flexibility required in modern power systems.