Biblio

We focus on the question of distributed control of electricity distribution networks in the face of security attacks to Distributed Energy Resources (DERs). Our attack model includes strategic manipulation of DER set-points by an external hacker to induce a sudden compromise of a subset of DERs connected to the network. We approach the distributed control design problem in two stages. In the first stage, we model the attacker-defender interaction as a Stackelberg game. The attacker (leader) disconnects a subset of DERs by sending them wrong set-point signals. The distribution utility (follower) response includes Volt-VAR control of non-compromised DERs and load control. The objective of the attacker (resp. defender) is to maximize (resp. minimize) the weighted sum of the total cost due to loss of frequency regulation and the cost due to loss of voltage regulation. In the second stage, we propose a distributed control (defender response) strategy for each local controller such that, if sudden supply-demand mismatch is detected (for example, due to DER compromises), the local controllers automatically respond based on their respective observations of local fluctuations in voltage and frequency. This strategy aims to achieve diversification of DER functions in the sense that each uncompromised DER node either contributes to voltage regulation (by contributing reactive power) or to frequency regulation (by contributing active power). We illustrate the effectiveness of this control strategy on a benchmark network.

We formulate a sequential (Stackelberg) game for assessing the vulnerability of radial electricity distribution networks to disruptions in Distributed Energy Resources (DERs). In this model, the attacker disrupts a subset of DER nodes by remotely manipulating the set-points of their inverters. The defender (network operator) responds by controlling the noncompromised DERs and by imposing partial load reduction via direct load control. The attacker’s (resp. defender’s) objective is to maximize (resp. minimize) the weighted sum of cost due to the loss of voltage regulation and the cost of load control. For the sequential play game where the attacker (resp. defender) is the leader (resp. follower) and under linear power flow equations, we show that the problem reduces to standard bilevel network interdiction problem. Under our assumptions on the attack model, we obtain a structural insight that the attacker’s optimal strategy is to compromise the downstream DER nodes as opposed to the upstream ones. We present a small case study to demonstrate the applicability of our model for vulnerability assessment of distribution networks.

This article focuses on the security assessment of electricity distribution networks (DNs) with vulnerable distributed energy resource (DER) nodes. The adversary model is simultaneous compromise of DER nodes by strategic manipulation of generation set-points. The loss to the defender (DN operator) includes loss of voltage regulation and cost of induced load control under supply-demand mismatch caused by the attack. A 3-stage Defender-Attacker-Defender (DAD) game is formulated: in Stage 1, the defender chooses a security strategy to secure a subset of DER nodes; in Stage 2, the attacker compromises a set of vulnerable DERs and injects false generation set-points; in Stage 3, the defender responds by controlling loads and uncompromised DERs. Solving this trilevel optimization problem is hard due to nonlinear power flows and mixed-integer decision variables. To address this challenge, the problem is approximated by tractable formulations based on linear power flows. The set of critical DER nodes and the set-point manipulations characterizing the optimal attack strategy are characterized. An iterative greedy approach to compute attacker-defender strategies for the original nonlinear problem is proposed. These results provide guidelines for optimal security investment and defender response in pre- and post-attack conditions, respectively.