PROJECT TITLE :

Characteristic Investigation and Control of a Modular Multilevel Converter-Based HVDC System Under

ABSTRACT:

An HVDC transmission system with a multilayer modular converter (MMC) is analysed and controlled under three single-line to ground fault conditions, with specific attention paid to the research of the fault characteristics of these three conditions. The generalised instantaneous power of a phase unit is theoretically computed using the equivalent circuit model of the MMC under unbalanced conditions, taking into account positive-, negative-, and zero-sequence components in both arm voltages and currents. A unique double-line frequency dc-voltage ripple suppression control is suggested based on this approach. Additionally, the HVDC system's fault tolerance might be increased without additional cost by using this controller in conjunction with the negative- and zero sequence current control. The performance of the HVDC system with and without single-phase switching is reviewed and compared in depth in order to enhance its fault-tolerant capability. To support the theoretical analysis and recommended control techniques, MATLAB/Simulink simulation results from a three-phase MMC-HVDC system have been included in this paper.