  Traditionally, Volt/VAR optimization (VVO) is performed in distribution
networks through legacy devices such as on-load tap changers (OLTCs), voltage
regulators (VRs), and capacitor banks. With the amendment in IEEE 1547
standard, distributed energy resources (DERs) can now provide reactive power
support to the grid. For this, renewable energy-based DERs, such as PV, are
interfaced with the distribution networks through smart inverters (SIs). Due to
the intermittent nature of such resources, VVO transforms into a dynamic
problem that requires extensive communication between the VVO controller and
devices performing the VVO scheme. This communication, however, can be
potentially tampered with by an adversary rendering the VVO ineffective. In
this regard, it is important to assess the impact of cyberattacks on the VVO
scheme. This paper develops a real-time co-simulation setup to assess the
effect of cyberattacks on VVO. The setup consists of a real-time power system
simulator, a communication network emulator, and a master controller in a
system-in-the-loop (SITL) setup. The DNP3 communication protocol is adopted for
the underlying communication infrastructure. The results show that corrupted
communication messages can lead to violation of voltage limits, increased
number of setpoint updates of VRs, and economic loss.
