Modelling and analysis of MMC-HVDC transmission systems

Abstract

Abstract—This work is devoted to a comparative-technical study of multilevel transmission systems based on VSC-HVDC technology. Two networks with different operating conditions (i.e., frequency and voltage) have been considered. Based on the continuity of last year's work on HVDC systems, a link between two asynchronous 400 kV- 60 Hz and 230 kV- 50 Hz networks is considered for a power of 300 MW (the same model studied). Under MATLAB/Simulink environment, simulations of multilevel cascaded VSC technologies are performed. The obtained results, including current and voltage on the DC side, are presented and successfully validated with those calculated using the theoretical model. This project also includes a technical analysis of multilevel VSCs, followed by a comparative study between different cascaded multilevel converters (3, 5, 7 and 9 levels). The comparison considers the performance as well as the stability of each converter when integrated into an HVDC transmission system. In general, the higher-level cascaded converters were found to have superior efficiency, reliability and harmonic generation compared to other converters with lower operating levels. In addition, the VSC-HVDC CHB offers many futuristic features for HVDC transmission technology and its applications worldwide.