An Observer Based Intrusion Detection Framework for Smart Inverters at the Grid-Edge

This paper presents an observer based predictive control scheme for grid-interactive inverters with intrusion detection capability. The proposed framework is robust to potential cyber-physical attacks due to intentional electromagnetic interference (EMI) on the vulnerable Hall-effect current sensors of the inverter. The robust operation of smart inverters at the grid-edge is highly dependent on the reliable and accurate current measurement in their feedback control scheme. The proposed security framework highlights two layers; the first layer detects an intrusion by EMI attack on the current sensor on-board of the inverter, while the second layer supports the first layer by establishing a secure line of communication between the inverter and the supervisory controller by using a time-sensitive passcode key. The observer uses the voltage measurements, which are not susceptible to EMI attacks targeting current sensors. The smart inverter flags the compromised current sensors at the grid-edge in a proactive manner by evaluating the current sensor measurements and the observer output in a constraint penalty function – leveraging the model predictive control phenomena. The intrusion detection and controller performance has been verified by multiple case studies.