Small signal analysis of a grid-forming modular multilevel converter with a novel virtual synchronous generator control.

• Development of a current source interfaced virtual synchronous generator (VSG) controller which emulates an actual synchronous generator (SG). • Investigation of the stability of the VSG controller when connected to ac systems with different strengths using small signal analysis as well as Electromagnetic Transients simulation (EMT) simulation. • Analysis of the transient performance and damping properties with inclusion/exclusion of 'virtual' damper windings. This paper introduces a grid forming (GFM) control method – detailed synchronous machine emulation virtual synchronous generator (VSG). The proposed method makes a voltage source converter exactly emulate a synchronous generator (SG), using a current source interface. The precise emulation of an SG gives tighter control over overcurrent and improved transient damping. Electromagnetic Transients (EMT) simulation is used to demonstrate the operation, and small signal model is used to assess the stability performance. Small signal analysis shows that the resulting VSG operates stably, and oscillatory modes can be damped by appropriate optimization of the virtual damping windings resistances. [ABSTRACT FROM AUTHOR]