Grid support functionalities based on modular multilevel converters with synchronous power control

Abstract

High voltage direct current (HVDC) transmission networks is one of the most interesting systems for the application of modular multilevel converters. Stability improvement of large interconnected systems is essential which has been largely studied in AC systems but still under development in DC networks. This paper presents a control strategy to provide support to the grid against disturbance in a HVDC system implemented with a modular multilevel converter (MMC). The main idea behind this work is to replace the classical power controller by a new control strategy, which emulates the characteristics of a synchronous generator. The control proposed is known as Synchronous Power Control (SPC) and it is able to emulate inertia, damping and droop characteristics required by the grid. To validate this work, simulation results are presented in a HVDC-MMC system connected to a weak grid.