Reliability improvement of Modular Multilevel Converter in HVDC systems

In this paper the reliability of a Modular Multilevel Converter for HVDC applications is incremented, by decreasing the electrical stress of the main passive component suitable to fault, that is, the capacitor cell. This effect is obtained with the injection of a suitable cell second harmonic circulating current. It's important to note how the cell current increment does not increase the semiconductor losses, but in some circumstances can even decrease such losses.