Improved microgrid resiliency through
distributionally robust optimization under a
policy-mode framework
Nawaf Nazir
Energy and Environment Directorate
Pacific Northwest National Laboratory
Richland, USA
nawaf.nazir@pnnl.gov
Thiagarajan Ramachandaran
Energy and Environment Directorate
Pacific Northwest National Laboratory
Richland, USA
thiagarajan.ramachandaran@pnnl.gov
Soumya Kundu
Energy and Environment Directorate
Pacific Northwest National Laboratory
Richland, USA
soumya.kundu@pnnl.gov
Veronica Adetola
Energy and Environment Directorate
Pacific Northwest National Laboratory
Richland, USA
veronica.adetola@pnnl.gov
Abstract—Critical energy infrastructure are constantly under
stress due to the ever increasing disruptions caused by wildfires,
hurricanes, other weather related extreme events and cyber-
attacks. Hence it becomes important to make critical infrastruc-
ture resilient to threats from such cyber-physical events. Such
events are however hard to predict and numerous in nature
and type, making it infeasible to become resilient to all possible
cyber-physical event as such an approach would make the system
operation overly conservative. Furthermore, distributions of such
events are hard to predict and historical data available on such
events is sparse. To deal with these issues, we present a policy-
mode framework that enumerates and predicts the probability
of various cyber-physical events on top of a distributionally
robust optimization (DRO) that is robust to the sparsity of the
available historical data. The proposed algorithm is illustrated on
an islanded microgrid example: a modified IEEE 123-node feeder
with distributed energy resources (DERs) and energy storage.
Index Terms—Distributionally robust optimization (DRO),
cyber-physical events, critical infrastructure, extreme events,
data-driven methods
I. INTRODUCTION
Critical energy infrastructure has undergone significant
changes in the past decades with the increased penetration
of distributed energy resources (DERs) and other inverter-
interfaced generation. While this has helped to achieve green-
house gas emission reduction goals [1], it has also made
the energy grid more vulnerable to breakdowns due to the
uncertainty and variability in renewable energy generation [2],
[3]. Furthermore, the risk of weather related outages such as
wildfires, hurricanes and other natural disasters have increased
in the past years [4] and so have the risk of possible cyber-
attacks [5]. This work provides a framework for improved re-
siliency of critical infrastructure systems, with an emphasis on
microgrid resiliency. Microgrids are a group of flexible energy
The authors are with the Electricity Infrastructure and Buildings Division
at PNNL, Richland, WA 99354, USA.
resources operating together locally as a single controllable
entity [6]. In our framework, we assess the risk associated
with various cyber-physical events and based on the risk
assessment operate the system under a particular policy-mode.
This allows us to be resilient against the risks without being
overly conservative. Then in order to deal with the sparsity
of data available on such cyber-physical events, we develop a
distributionally robust optimization (DRO) formulation that is
robust to a range of disturbance distributions.
Literature review/related work: Chance constraints con-
stitute a means to provide certain guarantees on constraint
satisfaction under uncertainty [7] and have found applications
in several domains including in power system optimization
under uncertainty. However, a major drawback of chance con-
straint formulations is that they only consider the probability of
constraint violation and not the impact. In many critical infras-
tructure systems, minimizing the impact of uncertainties is far
more significant. Conditional value at risk (CVaR) approaches
do account for the risk in constraint violation [8], however,
many of these methods require assumptions on the probability
distribution of the uncertainty and convex reformulations exist
only for a very small set of such distributions (e.g., Gaussian),
which may not hold in practice.
Distributionally robust chance constraint problems have
been well studied in the literature [9]. Even though, these
methods consider the risk in constraint violations, they can
often be overly conservative and furthermore still require
assumptions on the underlying distribution (e.g., moments)
to be accurate. In case the uncertainty distribution is not
known beforehand, sample based approaches have been used
in literature [10]. However, in case of rare events sampling
based approaches cannot be applied directly, since they would
require an impractical number of samples to yield reasonable
solutions [11], something which may not be available in
arXiv:2210.12586v2 [math.OC] 11 Mar 2024