There is enormous flexibility potential in the power consumption of the majority of electric loads. This flexibility can be harnessed to obtain services for managing the grid: with carefully designed decision rules in place, power consumption for the population of loads can be ramped up and down, just like charging and discharging a battery, without any significant impact to consumers' needs. The concept is called Demand Dispatch, and the grid resource obtained from this design virtual energy storage (VES). In order to deploy VES, a balancing authority is faced with two challenges: 1. how to design local decision rules for each load given the target aggregate power consumption (distributed control problem), and 2. how to coordinate a portfolio of resources to maintain grid balance, given a forecast of net-load (resource allocation problem).Rather than separating resource allocation and distributed control, in this paper the two problems are solved simultaneously using a single convex program. The joint optimization model is cast as a finite-horizon optimal control problem in a mean-field setting, based on the new KLQ optimal control approach proposed recently by the authors.The simplicity of the proposed control architecture is remarkable: With a large portfolio of heterogeneous flexible resources, including loads such as residential water heaters, commercial water heaters, irrigation, and utility-scale batteries, the control architecture leads to a single scalar control signal broadcast to every resource in the domain of the balancing authority. Keywords: Smart grids, demand dispatch, distributed control, controlled Markov chains.
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Virtual Energy Storage from Flexible Loads: Distributed Control with QoS Constraints.
Loads are expected to help the power grid of the future in balancing the highs and lows caused by intermittent renewables such as solar and wind. With appropriate intelligence, loads will be able manipulate demand around a nominal baseline so that the increase and decrease of demand appears like charging and discharging of a battery, thereby creating a virtual energy storage (VES) device. An important question for the control systems community is: how to control these flexible loads so that the apparently conflicting goal of maintaining consumers’ quality of service (QoS) and providing reliable grid support are achieved? We advocate a frequency domain thinking of handling both of these issues, along the lines of a recent paper. In this article, we discuss some of the challenges and opportunities in designing appropriate control algorithms and coordination architectures in obtaining reliable VES from flexible loads.
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- Award ID(s):
- 1646229
- NSF-PAR ID:
- 10211986
- Editor(s):
- Stoustrup J., Annaswamy A.
- Date Published:
- Journal Name:
- Smart Grid Control. Power Electronics and Power Systems
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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null (Ed.)A new stochastic control methodology is introduced for distributed control, motivated by the goal of creating virtual energy storage from flexible electric loads, i.e. Demand Dispatch. In recent work, the authors have introduced Kullback- Leibler-Quadratic (KLQ) optimal control as a stochastic control methodology for Markovian models. This paper develops KLQ theory and demonstrates its applicability to demand dispatch. In one formulation of the design, the grid balancing authority simply broadcasts the desired tracking signal, and the hetero-geneous population of loads ramps power consumption up and down to accurately track the signal. Analysis of the Lagrangian dual of the KLQ optimization problem leads to a menu of solution options, and expressions of the gradient and Hessian suitable for Monte-Carlo-based optimization. Numerical results illustrate these theoretical results.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1007/978-3-319-98310-3_6
