A novel fault ride through strategy for grid-connected virtual synchronous Generators: Power angle stability enhancement and current limiting

Abstract

As more and more renewable energy generations (REGs) are connected to the power grid through grid-following converters, the lack of inertia has become a challenge to grid-frequency stability. Virtual Synchronous Generator (VSG) is a prospected solution for this issue. However, VSGs still have several unresolved issues in practical application. Especially, in a three-phase symmetrical fault scenario, the inrush current may damage the converter and the VSG would lose synchronization with the grid. To address these issues, this paper presents a novel fault ride through (FRT) strategy. First, the transient behaviours of VSGs, including transient current characteristics and power angle characteristics are analysed, which reveals that the increase of the power angle would aggravate the inrush current. Thus, an angular frequency dynamic compensation (AFDC) strategy is proposed to eliminate the instability of power angle. Then, this paper presents a current-limiting strategy combining virtual impedance (VI) and reference voltage adjustment to limit the fault current to a safe level. Finally, the time-domain simulations and experimental tests are performed to verify the effectiveness of the proposed FRT strategy.