Zero-Dynamics Attack on Wind Turbines and Countermeasures Using Generalized Hold and Generalized Sampler

Most wind turbines are monitored and controlled by supervisory control and data acquisition systems that involve remote communication through networks. Despite the flexibility and efficiency that network-based monitoring and control systems bring, these systems are often threatened by cyberattacks. Among the various kinds of cyberattacks, some exploit the system dynamics so that the attack cannot be detected by monitoring system output, the zero-dynamics attack is one of them. This paper confirms that the zero-dynamics attack is fatal to wind turbines and the attack can cause system breakdown. In order to protect the system, we present two defense strategies using a generalized hold and a generalized sampler. These methods have the advantage that the zeros can be placed so that the zero dynamics of the system become stable; as a consequence, the zero-dynamics attack is neutralized. The effects of the countermeasures are validated through numerical simulations and the comparative discussion between two methods is provided.