PI Passivity-based Control and Performance Analysis of MMC Multi-Terminal HVDC Systems

In this paper, a decentralized PI passivity-based controller is applied to modular multilevel converters to ensure global stability of a multiterminal high-voltage direct current system. For the derivation of the controller, an appropriate model with constant steady-state solutions is obtained via a multifrequency orthogonal coordinates transformation. The control design is then completed using passivity arguments, and performance guarantees are established by a small-signal analysis. The obtained results are validated by means of detailed time-domain simulations both on a single-terminal and a four-terminal benchmarks.