Adversarial Attacks to Distributed Voltage Control in Power Distribution Networks with DERs

It has been recently proposed that the reactive power injection of distributed energy resources (DERs) can be used to regulate the voltage across the power distribution network, and simple distributed control laws have been recently developed in the literature for performing such distributed Volt/VAR control. However, enabling the reactive-power injection capability of DERs also opens the door for potential adversarial attacks. Specifically, the adversary can compromise a subset of the DERs and use their reactive power to disrupt the voltage profile across the distribution network. In this paper, we study the potential damage (in terms of the voltage disruption) of such adversarial attacks and how to mitigate the damage by controlling the allowable range of reactive power injection at each bus. Somewhat surprisingly and contrary to the intuition that the reactive power injection at legitimate buses should help mitigating the voltage disruption inflicted by the adversary, we demonstrate that an intelligent attacker can actually exploit the response of the legitimate buses to amplify the damage by two times. Such a higher level of damage can be attained even when the adversary has no information about the network topology. We then formulate an optimization problem to limit the potential damage of such adversarial attacks. Our formulation sets the range of the reactive power injection on each bus so that the damage by the adversary is minimized, subject to the constraint that the voltage mismatch (without attack) can still be maintained within a given threshold under an uncertainty set of external inputs. Numerical results demonstrate the validity of our analysis and the effectiveness of our approach to mitigate the damage caused by such attacks.