1,082 research outputs found
On the Economic Value and Price-Responsiveness of Ramp-Constrained Storage
The primary concerns of this paper are twofold: to understand the economic
value of storage in the presence of ramp constraints and exogenous electricity
prices, and to understand the implications of the associated optimal storage
management policy on qualitative and quantitative characteristics of storage
response to real-time prices. We present an analytic characterization of the
optimal policy, along with the associated finite-horizon time-averaged value of
storage. We also derive an analytical upperbound on the infinite-horizon
time-averaged value of storage. This bound is valid for any achievable
realization of prices when the support of the distribution is fixed, and
highlights the dependence of the value of storage on ramp constraints and
storage capacity. While the value of storage is a non-decreasing function of
price volatility, due to the finite ramp rate, the value of storage saturates
quickly as the capacity increases, regardless of volatility. To study the
implications of the optimal policy, we first present computational experiments
that suggest that optimal utilization of storage can, in expectation, induce a
considerable amount of price elasticity near the average price, but little or
no elasticity far from it. We then present a computational framework for
understanding the behavior of storage as a function of price and the amount of
stored energy, and for characterization of the buy/sell phase transition region
in the price-state plane. Finally, we study the impact of market-based
operation of storage on the required reserves, and show that the reserves may
need to be expanded to accommodate market-based storage
Resilience of Locally Routed Network Flows: More Capacity is Not Always Better
In this paper, we are concerned with the resilience of locally routed network
flows with finite link capacities. In this setting, an external inflow is
injected to the so-called origin nodes. The total inflow arriving at each node
is routed locally such that none of the outgoing links are overloaded unless
the node receives an inflow greater than its total outgoing capacity. A link
irreversibly fails if it is overloaded or if there is no operational link in
its immediate downstream to carry its flow. For such systems, resilience is
defined as the minimum amount of reduction in the link capacities that would
result in the failure of all the outgoing links of an origin node. We show that
such networks do not necessarily become more resilient as additional capacity
is built in the network. Moreover, when the external inflow does not exceed the
network capacity, selective reductions of capacity at certain links can
actually help averting the cascading failures, without requiring any change in
the local routing policies. This is an attractive feature as it is often easier
in practice to reduce the available capacity of some critical links than to add
physical capacity or to alter routing policies, e.g., when such policies are
determined by social behavior, as in the case of road traffic networks. The
results can thus be used for real-time monitoring of distance-to-failure in
such networks and devising a feasible course of actions to avert systemic
failures.Comment: Accepted to the IEEE Conference on Decision and Control (CDC), 201
- …