Cyber-Attacks in Modular Multilevel Converters

Abstract

Distributed control of modular multilevel converter (MMC) submodules (SMs) offers several potential benefits such as flexibility, scalability and modularity. In this approach, lowlevel control tasks, such as capacitor voltage balancing, can be distributed amongst controllers placed in the SMs. This decreases the computational burden for the central control system that performs high-level control tasks; also, a single point of failure is avoided. Distributed control architecture requires a cyberphysical network (CFN) through which local controllers share all the information necessary to perform their respective control loops. To date, none of the reported works in this field have paid attention to potential imperfections in the CFN. Indeed, previous works are based on the assumption that the network always provides correct information to the local controllers. However, erroneous measurements in the CFN may degrade the distributed control scheme operation, leading to suboptimal or even unstable operation. These events can occur in the presence of cyberattacks, for example, which can be created through illegitimate data intrusion into the distributed control architectures. This paper is the first to investigate the impacts of cyber-attacks on distributed control schemes used in MMCs. The effects of a specific cyber-attack, named false data injection attack (FDIA), on a consensus-based distributed control strategy are studied in this work. Additionally, a method for detecting FDIAs is proposed, along with a countermeasure strategy, to ensure the safe operation of the MMC whilst the attack is cleared. The proposals reported in this paper are validated using simulation and experimental results.

Impact and Mitigation of High-Frequency Side-Channel Noise Intrusion on the Low-Frequency Performance of an Inverter

“…Now, during nominal operation if measurement of the inverter state(s) is contaminated due to SNI, then, the inverter control is compromised. To mitigate the effects of the contaminated feedback state(s), a noise-rejection-estimation-based technique is employed [11], [14]. Kalman filter [15], as captured in the generalized structure (8), is used to estimate all the contaminated state(s) of the inverter −1 , P is a positive definite matrix that minimizes the steady-state covariance between x k and xk+1|k , y k = C • x k , where C is an identity matrix, whose dimension depends on the number of measured inverter states that are contaminated, and R represents the covariance of the measurement noise.…”

“…This work, given this backdrop, studies experimentally the effect of a specific type of intrusion, which contaminates the output-voltage signal of an inverter and investigates its impact on the performance degradation of the inverter leading to a simple solution that mitigates the problem. Unlike conventional sensor-attack scenarios [11], [12], in this work, we consider the side-channel noise intrusion (SNI) at the gateway to the digital signal processor (DSP) controller. We investigate, in Section II, using phase-plane and frequency-domain analyses, the impact of the proximity of the SNI noise frequency to the sampling frequency of the inverter.…”

Cyber-Resilient Converter Control System for Doubly Fed Induction Generator-Based Wind Turbine Generators

“…A consensus-based distributed control system for modular multilevel converter (MMC) submodules (SMs) was proposed in ref. [11] to prevent bad data attacks. Additionally, a Kalman Filter-based FDIA detection method was introduced.…”

Reinforcement Learning-Based Method to Exploit Vulnerabilities of False Data Injection Attack Detectors in Modular Multilevel Converters

“…Both centralised and distributed control architectures are implemented in a cyber-physical system (CPS), composed of sensors, communication links, etc., where interactions between the physical elements and computational processes occur [10]. The CPS is vulnerable to malicious cyber-attacks, which could potentially degrade the converter operation, lead to suboptimal or even unstable operation, and induce protection system tripping in severe cases.…”