22 research outputs found
Greening Multi-Tenant Data Center Demand Response
Data centers have emerged as promising resources for demand response,
particularly for emergency demand response (EDR), which saves the power grid
from incurring blackouts during emergency situations. However, currently, data
centers typically participate in EDR by turning on backup (diesel) generators,
which is both expensive and environmentally unfriendly. In this paper, we focus
on "greening" demand response in multi-tenant data centers, i.e., colocation
data centers, by designing a pricing mechanism through which the data center
operator can efficiently extract load reductions from tenants during emergency
periods to fulfill energy reduction requirement for EDR. In particular, we
propose a pricing mechanism for both mandatory and voluntary EDR programs,
ColoEDR, that is based on parameterized supply function bidding and provides
provably near-optimal efficiency guarantees, both when tenants are price-taking
and when they are price-anticipating. In addition to analytic results, we
extend the literature on supply function mechanism design, and evaluate ColoEDR
using trace-based simulation studies. These validate the efficiency analysis
and conclude that the pricing mechanism is both beneficial to the environment
and to the data center operator (by decreasing the need for backup diesel
generation), while also aiding tenants (by providing payments for load
reductions).Comment: 34 pages, 6 figure
Distributional Analysis for Model Predictive Deferrable Load Control
Deferrable load control is essential for handling the uncertainties
associated with the increasing penetration of renewable generation. Model
predictive control has emerged as an effective approach for deferrable load
control, and has received considerable attention. In particular, previous work
has analyzed the average-case performance of model predictive deferrable load
control. However, to this point, distributional analysis of model predictive
deferrable load control has been elusive. In this paper, we prove strong
concentration results on the distribution of the load variance obtained by
model predictive deferrable load control. These concentration results highlight
that the typical performance of model predictive deferrable load control is
tightly concentrated around the average-case performance.Comment: 12 pages, technical report for CDC 201
Opportunities for Price Manipulation by Aggregators in Electricity Markets
Aggregators are playing an increasingly crucial role in the integration of
renewable generation in power systems. However, the intermittent nature of
renewable generation makes market interactions of aggregators difficult to
monitor and regulate, raising concerns about potential market manipulation by
aggregators. In this paper, we study this issue by quantifying the profit an
aggregator can obtain through strategic curtailment of generation in an
electricity market. We show that, while the problem of maximizing the benefit
from curtailment is hard in general, efficient algorithms exist when the
topology of the network is radial (acyclic). Further, we highlight that
significant increases in profit are possible via strategic curtailment in
practical settings
Optimal Charging of Electric Vehicles in Smart Grid: Characterization and Valley-Filling Algorithms
Electric vehicles (EVs) offer an attractive long-term solution to reduce the
dependence on fossil fuel and greenhouse gas emission. However, a fleet of EVs
with different EV battery charging rate constraints, that is distributed across
a smart power grid network requires a coordinated charging schedule to minimize
the power generation and EV charging costs. In this paper, we study a joint
optimal power flow (OPF) and EV charging problem that augments the OPF problem
with charging EVs over time. While the OPF problem is generally nonconvex and
nonsmooth, it is shown recently that the OPF problem can be solved optimally
for most practical power networks using its convex dual problem. Building on
this zero duality gap result, we study a nested optimization approach to
decompose the joint OPF and EV charging problem. We characterize the optimal
offline EV charging schedule to be a valley-filling profile, which allows us to
develop an optimal offline algorithm with computational complexity that is
significantly lower than centralized interior point solvers. Furthermore, we
propose a decentralized online algorithm that dynamically tracks the
valley-filling profile. Our algorithms are evaluated on the IEEE 14 bus system,
and the simulations show that the online algorithm performs almost near
optimality ( relative difference from the offline optimal solution) under
different settings.Comment: This paper is temporarily withdrawn in preparation for journal
submissio
Online Algorithms: From Prediction to Decision
Making use of predictions is a crucial, but under-explored, area of sequential decision problems with limited information. While in practice most online algorithms rely on predictions to make real time decisions, in theory their performance is only analyzed in simplified models of prediction noise, either adversarial or i.i.d. The goal of this thesis is to bridge this divide between theory and practice: to study online algorithm under more practical predictions models, gain better understanding about the value of prediction, and design online algorithms that make the best use of predictions.
This thesis makes three main contributions. First, we propose a stochastic prediction error model that generalizes prior models in the learning and stochastic control communities, incorporates correlation among prediction errors, and captures the fact that predictions improve as time passes. Using this general prediction model, we prove that Averaging Fixed Horizon Control (AFHC) can simultaneously achieve sublinear regret and constant competitive ratio in expectation using only a constant- sized prediction window, overcoming the hardnesss results in adversarial prediction models. Second, to understand the optimal use of noisy prediction, we introduce a new class of policies, Committed Horizon Control (CHC), that generalizes both popular policies Receding Horizon Control (RHC) and Averaging Fixed Horizon Control (AFHC). Our results provide explicit results characterizing the optimal use of prediction in CHC policy as a function of properties of the prediction noise, e.g., variance and correlation structure. Third, we apply the general prediction model and algorithm design framework to the deferrable load control problem in power systems. Our proposed model predictive algorithm provides significant reduction in variance of total load in the power system. Throughout this thesis, we provide both average-case analysis and concentration results for our proposed online algorithms, highlighting that the typical performance is tightly concentrated around the average-case performance.</p
Distributed Optimization via Local Computation Algorithms
We propose a new approach for distributed optimization based on an emerging area of theoretical computer science -- local computation algorithms. The approach is fundamentally different from existing methodologies and provides a number of benefits, such as robustness to link failure and adaptivity in dynamic settings. Specifically, we develop an algorithm, LOCO, that given a convex optimization problem P with n variables and a "sparse" linear constraint matrix with m constraints, provably finds a solution as good as that of the best online algorithm for P using only O(log(n+m)) messages with high probability. The approach is not iterative and communication is restricted to a localized neighborhood. In addition to analytic results, we show numerically that the performance improvements over classical approaches for distributed optimization are significant, e.g., it uses orders of magnitude less communication than ADMM
Distributed Optimization via Local Computation Algorithms
We propose a new approach for distributed optimization based on an emerging area of theoretical computer science -- local computation algorithms. The approach is fundamentally different from existing methodologies and provides a number of benefits, such as robustness to link failure and adaptivity in dynamic settings. Specifically, we develop an algorithm, LOCO, that given a convex optimization problem P with n variables and a "sparse" linear constraint matrix with m constraints, provably finds a solution as good as that of the best online algorithm for P using only O(log(n+m)) messages with high probability. The approach is not iterative and communication is restricted to a localized neighborhood. In addition to analytic results, we show numerically that the performance improvements over classical approaches for distributed optimization are significant, e.g., it uses orders of magnitude less communication than ADMM
Opportunities for Price Manipulation by Aggregators in Electricity Markets
Aggregators are playing an increasingly crucial role for integrating renewable generation into power systems. However, the intermittent nature of renewable generation makes market interactions of aggregators difficult to monitor and regulate, raising concerns about potential market manipulations. In this paper, we address this issue by quantifying the profit an aggregator can obtain through strategic curtailment of generation in an electricity market. We show that, while the problem of maximizing the benefit from curtailment is hard in general, efficient algorithms exist when the topology of the network is radial (acyclic). Further, we highlight that significant increases in profit can be obtained through strategic curtailment in practical settings
Opportunities for Price Manipulation by Aggregators in Electricity Markets
Aggregators of distributed generation are playing an increasingly crucial role in the integration of renewable energy in power systems. However, the intermittent nature of renewable generation makes market interactions of aggregators difficult to monitor and regulate, raising concerns about potential market manipulation by aggregators. In this paper, we study this issue by quantifying the profit an aggregator can obtain through strategic curtailment of generation in an electricity market. We show that, while the problem of maximizing the benefit from curtailment is hard in general, efficient algorithms exist when the topology of the network is radial (acyclic). Further, we highlight that significant increases in profit are possible via strategic curtailment in practical settings
Opportunities for Price Manipulation by Aggregators in Electricity Markets
Aggregators are playing an increasingly crucial role for integrating renewable generation into power systems. However, the intermittent nature of renewable generation makes market interactions of aggregators difficult to monitor and regulate, raising concerns about potential market manipulations. In this paper, we address this issue by quantifying the profit an aggregator can obtain through strategic curtailment of generation in an electricity market. We show that, while the problem of maximizing the benefit from curtailment is hard in general, efficient algorithms exist when the topology of the network is radial (acyclic). Further, we highlight that significant increases in profit can be obtained through strategic curtailment in practical settings