Cyber attack in PV sysTem for voltagE regulation in diStribution neTwork (CybTEST)

The sizeable practical power system networks are prone to cyber-physical attacks. The cyberphysical system is integration of physical and communication layer for advance control and self –monitoring techniques, optimisation of assets use, advanced fault detection and mitigation, facilitation of distributed generation and electric vehicle. The archetypical diagram of cyber-physical system is shown in Figure 1. However, exposure of physical system to communication system is main source of cyber-physical attacks. The studies to various kinds of cyberphysical attacks are limited to the type of system and type of cyber-physical attack construction. The detection and mitigation techniques are only designed for conventional energy resources and malware intrusion into the system. 

The detection and mitigation of cyber-physical attack can be achieved on the condition that the nature of the attack is exhaustively studied. The switching sliding mode attack construction provides a way to stealthy attack. The foundation of sliding mode attack is variable structure theory that consists of set of continuous subsystems with proper switching logic/algorithm and, as a result, control actions remain discontinuous functions of system state disturbances and reference inputs. The core idea of designing VSS control algorithm consists of enforcing this type of motion in some form of manifolds in system state spaces.  

Therefore, in the present study, switching sliding mode attack construction involves enforcing the state variables of power network towards instability in a particular form of manifolds (sliding surface) by changing the status of circuit breaker [1].  

The study and analysis of switching sliding attack construction was made possible by imitating the behaviour of intruder. The intruder could remotely connected and intrude in the system over TCP/IP communication protocols. These protocols establish a connection similar to pipeline theory. The intruder design sliding surface and switching algorithm was introduced in the system by means of TCP/IP socket. 

The switching stage involves two attributes in the algorithm i.e. “start” and “stop” time of switching based on intruder designed sliding surface. The start- and stop-time of switching sliding mode attack is graphically analysed via phase-portrait plot as shown in Figure 2. The said plot is a graphical representation of rotor angle and rotor speed of the generator. The start-time and stop-time is selected such that the intruder applies the attack in a swiftly and stealthy manner. 

The algorithm based on switching sliding surface for attack construction is tested on IEEE 9-bus system. The successful implementation of attack algorithm shows its commendable yet disastrous nature on leading to generator instability.  

The study forms a basis for understanding the generator behaviour, at the time of cyber-attack and thus the approach can helpful to devise its detection and mitigation techniques. The study related to impact of cyber-attack in the control loop of PV systems integrated in distributed network could not be carried out during the visit. This is due to the fact, that we wished to first implement the attack construction algorithm on transmission network, i.e. standard test network, for which model was already available in the RSCAD software.