Optimal Control Strategies For VSC In MTDC Network

Technological advancement in the field of power electronics,in the past decade,led to global advancement in the field of power system.Moreover,constantly depleting conventional energy resources and the environmental hazards associated with them resulted in a trend of green and renewable energy generation.High Voltage Direct Current(HVDC)transmission system offers several advantages over traditional HVAC transmission system in terms of cost,efficiency,reliability and renewable energy integration.Multi Terminal Direct Current(MTDC)distribution network serves as the platform for connecting the transmission system to the load center providing flexibility of renewable energy integration into the main grid.Converter serves as the backbone in HVDC transmission system.Previously installed system contains Line Commutated Converters(LCC),which was the only reliable and mature option at that time.But the current systems prefer Voltage Source Converter(VSC),which provides higher rating and control.Modular Multilevel Converter(MMC)is the most advanced form of the power converter,which is the product of high advancement in power electronics and switching techniques.VSC and MMC forms the basis of modern power system infrastructure.VSC-MTDC and MMC-MTDC systems enables high power applications,large scale integration,smart and reliable operation.The performance of a VSC or MMC based system depends on the controller setting of the converter.Usually hit and trial method or operator’s experience is utilized for tuning the converter.In multi terminal direct current(MTDC)network,converter control becomes more crucial due to the involvement of multiple grids simultaneously.Such situation demands an optimal and intelligent control strategy for the converter to ensure smooth,high quality and efficient operation.This research focuses on the study and understanding of VSC extending to their optimal control strategies based on fuzzy logic and Artificial intelligence(deep learning)techniques,leading to an improved response in terms of operational efficiency,smooth performance and coordination,fast settling time,better slew rate,minimum undershoot and minimum overshoot response、Fuzzy logic and Deep learning techniques are implemented on a three terminal VSC based MTDC systems designed and simulated in MATLAB/SIMULINK.These techniques help to optimize the parameters of the controller which in turn produce optimized response.The research also focuses on the implementation of a unified voltage droop control strategy for a VSC-MTDC network.A three terminal MTDC system is designed and simulated in PSCAD for the Voltage droop control strategy.