Markov-Based Stochastic Stabilization Control for MMC-HVDC Systems With Inertia Supporting Under Random Disturbances

The communication-dependent inertia supporting of MMC-HVDC systems transmits the ac frequency information to the MMC station via phase measured units (PMUs), and provides frequency support for the connected ac grid. However, the random disturbances including the communication time delays and denial of service (DoS) attacks in the communication networks introduce new threats on the stable operation of the MMC-HVDC and the connected ac system. This article proposes a Markov-based stochastic stabilization control for MMC-HVDC systems with inertia supporting under random disturbances. Firstly, the Markov time-delay jump model of MMC-HVDC systems with inertia supporting is investigated under random disturbances, while the communication delay and DoS attacks are modeled as the stochastic Markov jumps with bounded time-varying delay and state discontinuities. Then the time delay term is regarded as a kind of equivalent disturbance acting on system input and compensated through the second-order communication disturbance observer (CDO). Besides, a Markov-based finite-time stabilization controller is designed for MMC-HVDC to mitigate the influence of random DoS attacks without need of information about the detailed DoS attack states. Simulations of several cases on PSCAD/EMTDC platform show that the inertia supporting control of MMC-HVDC can remain stable and unaffected in realizing fast frequency recovery for the ac grid under the random disturbances in the communication networks.