Cyber-physical resilience of power electronics-enabled power systems

Abstract

The demand for carbon neutrality results in increasing integration of power electronics devices (e.g., wind, photovoltaic, electric vehicle, storage) into the power system, which lays the foundation for most economic and social activities. This leads to a paradigm shift from a traditional synchronous generator-based power system to a power electronics-enabled power system. The integrated power electronics devices enable the power system with higher performance via underlying metering and communication infrastructures, which introduce additional access points that could be potential cyber threats. As a result, the power electronics-enabled power system is intrinsically a cyber-physical system and has been demonstrated to be vulnerable to cyber-attacks. In other words, the interconnected power electronics devices, if compromised by cyber-attacks, could significantly deteriorate the power system performance, leading to possible load shedding, generator tripping, and even blackout. Motivated by these considerations, this thesis investigates the cyber-physical resilience of the power electronics-enabled power system in a cyber defender-attacker-defendee framework. First, from the perspective of a cyber defender, this thesis addresses the cybersecurity evaluation and enhancement for a multi-infeed high-voltage direct-current system, which is interfaced by line-commutated-converters. A two-timescale model is established to evaluate the cyber-attack-induced sequential impacts. Then, an event-triggered cyber-defense strategy is proposed to enhance cybersecurity by mitigating multiple non-simultaneous cyber-attacks. As an extension, this thesis also investigates the cost-benefit trade-off of a hybrid alternating-current/direct-current grid, which is interfaced by voltage-sourced-converters. To mitigate the cyber-attack-induced frequency deviations in alternating-current grids and voltage deviations in direct-current grids, this thesis proposes a cost-benefit-based cyber-defense strategy, which achieves the trade-off between maximizing the cyber-defense benefits and minimizing the cyber-defense costs. Second, from the perspective of a cyber attacker, this thesis investigates and proposes a small-signal angle stability-oriented false data injection cyber-attack focusing on two attacking purposes, i.e., the stability margin and operation cost, with different attacking priorities. A structure-preserving model-based cyber-attack is proposed with an implicit stability constraint in a novel bi-level model. The interarea mode and the local mode of the small-signal angle stability-oriented false data injection cyber-attack are addressed by a closed-form solution and a moving target cyber-attack-based solution, respectively. Finally, from the perspective of a cyber defendee, which is referred to as the power electronics-enabled power system that needs protection, this thesis investigates the existence and maximization of the security region of an inverter-interfaced power system under two general inverter control modes. From a geometric viewpoint in control and state variable space, this thesis formulates closed-form sufficient conditions of the existence and maximization of the security region. Dual properties of the security region between two control modes and between two state areas are addressed.