Design optimization of an MMC based HVDC current flow controller

The modular multilevel converter (MMC) provides a lot of features such as low harmonic voltage content, a high power quality or easy scalability. Due to its several advantages, it is a well-suited topology for high-voltage direct current (HVDC) applications. In a meshed DC grid, a current flow control is essential. In this paper, an MMC based HVDC current flow controller is described which allows an exchange of direct power between two or more lines and can be directly installed at a DC node without any additional AC grid. Furthermore, a dimensioning method is presented for ideal scalable semiconductors as well as a design optimization based on the simplex algorithm. With this approach, additional degrees of freedom are obtained and it is possible to realize a holistic dimensioning of a given circuit.