Extension of power transmission capacity in MMC-based HVDC systems through dynamic temperature-dependent current limits

This paper proposes the extension of the current control loops used in Modular Multilevel Converters to include semiconductors junction temperature as an operational constraint. A new controller is added to the inner current loop to modulate the current limits as a function of the temperature, providing an extension of the power transmission capacity without violating the thermal limits of the semiconductors. A numerical method to investigate the operation of converters with temperature-dependent current limits is proposed and the stability of the controller is analyzed and validated through simulations under steady and transient operations.