A Review on Controller Scalability for VSC-MTDC Grids: Challenges and Applications

ABSTRACT This paper addresses the controller design potentials, challenges, and scope of improvements, which are used to control various VSC-MTDC grids effectively even in presence of renewable energy resources. Advantages of VSC-MTDC systems are high-speed power reversal capability, asynchronous interconnection, no need of reactive power compensation, more economical and flexible, etc. Hence, the different developed control schemes are discussed and summarized in terms of scalability of VSC-MTDC grid topologies. Based on different VSC-MTDC topologies, several controllers such as conventional PI controllers, optimal controllers, robust controllers, and intelligent controllers design potentials with their limitations has been discussed in this study. In order to minimize greenhouse effect, the renewable energy plants, i.e wind farms, solar plants, tidal energy plants, etc. are also integrated to VSC-MTDC grids. Due to uncertainties in renewable energy plants, it is necessary to use robust and intelligent control strategy for the optimal power sharing among terminals and also to maintain the stability of the system. Hence, scope of improvements, design potentials, challenges, integration of renewable energy resources, and limitations based on VSC-MTDC model topologies has been discussed.