A novel model of MMC-VSC for simulating multi-scale transients in MTDC transmission systems

Abstract

A novel model for the simulation of diverse transients covering multiple time-scales for modular multilevel converter (MMC)-based voltage source converter (VSC) is presented. It makes use of the method of shifted frequency analysis (SFA) in which the carrier with a frequency of 50 or 60 Hz is removed at VSC ac-side system. Using the SFA, an average-value model (AVM)-based MMC-VSC multi-scale transient model is developed, resulting in a flexible simulation of electromechanical and electromagnetic transients (EMT) by adjusting the time-step sizes. This can also be achieved in the multi-terminal DC (MTDC) transmission systems. The effectiveness of the proposed model is validated by comparisons with EMT model to simulate diverse transients such as phase-to-ground faults and wind power fluctuations in a realistic three-terminal DC grid.