Sharing Inertia Between VSC-HVDC Interconnected Weak AC Systems with a Self-Governing Control Scheme

VSC-HVDC is extensively used to connect asynchronous AC systems. While the synchronization of a VSC brings about requirement for short circuit capacity (SCC) of the embedded system, and the implementation of VSC impairs inertial of the system by taking the place of conventional generators. In this paper, a self-governing control scheme (SGC) is proposed for VSC-HVDC that interconnects weak AC systems. The SGC can operate VSCs in low SCC, and enables mutual inertial sharing between the interconnected AC systems during transient. These advantages of the SGC is achieved by operating a VSC in a way that mimics an electric motor for the AC grid, and in the meantime mimics a prime mover for the other VSC of HVDC. Moreover, like a synchronous machine, the VSC autonomously synchronizes with AC grid without any dedicated synchronization unit. No AC measurement nor VSCs' mutual communication is utilized in the SGC. The SGC's effectiveness in inertial sharing between weak AC grids is verified through RTDS simulations.