Impact of the MMC level number to reduce THD rate and improve the power quality transmitted to the electrical grid

The High Voltage Direct Current (HVDC) power systems has an important role in transmitting high power among long distances with respect to the transportation of the AC high voltage (HVAC). The HVDC grid has a set of advantages such as robustness against disturbances and low power losses compared to the AC system and the connection between two AC power grids. Modular Multi-Level Converter (MMC) is more suitable kind of topology compared to other topologies used in HVDC applications. The increasing number of submodules (SM) presents a challenge for researchers in terms of ordering complexity. In this paper, two pulse width modulation techniques are compared in the quality of currents and voltages to the filter level, which presents one of the major problems of the MMC converter. The simulation was performed using MATLAB/Simulink software and the presented simulation results prove the performance of the proposed control systems. The output voltage waveforms and the total harmonic distortion (THD) rate of the proposed system are improved without the need for a filter.