Lyapunov theory-based control strategy for multi-terminal MMC-HVDC systems

This paper presents a coordinated control strategy based on direct Lyapunov theory to handle the consistency of AC grids in multi-terminal (MT) modular multilevel converter (MMC)-HVDC systems during varying both loads and DC link voltage. As first contribution, set dynamic equations is proposed separating dynamics MMCs upper lower arms state variables. The consists only their related upper/lower variables leading more effective components for steady terms technique. To develop parts controller, global asymptotical stability MT MMC-HVDC system assessed by method. another advantage separated equations, able exploit very simple decoupled functions. Moreover, order specify variation trend coefficients, further analysis contributes demonstrating effects coefficients variable errors its dynamic. main contribution this paper, two independent capability curves power injection arms, are obtained which will be through changing input output voltages as well MMC parameters. Finally, simulation results MATLAB software utilized verify validity strategy.