Methods to Enhance Cybersecurity of Multiple Inverters in Large Grid connected PV / Battery Energy Storage Systems

In this paper, methods for enhancing the cyber-security of multi-inverter systems in large-scale grid following photovoltaic (PV) and battery energy storage systems (ESS) are investigated. The study uses data from a 2.5 MW solar PV system and a 1.1 MW battery ESS, both interfaced with the grid through CenterPoint Energy Inc. at the Volkman location. The paper examines several attack scenarios, focusing particularly on False Data Injection (FDI) attacks targeting sensors within Cyber-Physical Systems (CPS). These inverters are especially vulnerable to cyber-attacks that compromise the integrity of the Programmable Logic Controller (PLC) and the transmitted sensor data. Attackers exploit vulnerabilities, including side-channel attacks on PLCs and sensor data spoofing, which threaten system security. To mitigate these risks, a dual-layer defense strategy is proposed, incorporating side-channel monitoring of the PLC and the embedding of a unique "watermark" (a low-magnitude, randomly fluctuating voltage signal) into the inverter’s DC link voltage. This watermark serves as a diagnostic tool to detect unauthorized changes in sensor data, enhancing the system’s ability to identify and respond to potential intrusions. Preliminary results from a hardware-in-the-loop (HIL) emulation, utilizing real-world data from the CenterPoint Energy solar farm, demonstrate the effectiveness of combining side-channel monitoring with watermarking in detecting previously undetectable attacks in multi-inverter systems.