Stable Frequency Response for Multi-Terminal MMC-HVDC System with DC Voltage Fluctuations

This paper presents a control strategy for a Multi-Terminal MMC-HVDC system to enhance the frequency response of AC grids. Using power sharing of both upper and lower arms of MMC combined with a basic equation of control functions, the proposed upper and lower control functions are extracted. In these proposed control functions, total wasted power in both upper and lower arms along with the power generated by the arm inductances are considered. The proposed control functions are capable of providing accurate performance with fast frequency response for AC grids with the existence of both load variations and DC voltage fluctuations. MATLAB/SIMULINK software is employed to demonstrate the merit of proposed controller.