Adaptive FRT Improvement of DC-Link Voltage-based VSGs in Weak Power Grids

The integration of renewable energy sources (RESs) in modern power systems (MPSs) has been increased. Traditionally, Grid-Following Inverters (GFLIs) have been widely employed for integrating in MPSs. However, in recent years, Grid-Forming Inverters (GFMIs) have emerged as a promising architecture for integrating of RESs. GFMIs mainly establishes their voltage and frequency references independently. This enables GFMIs to have an active contribution on the system inertia, damping, and voltage support. This work develops a fault ride through (FRT) mechanism for Virtual Synchronous Generator (VSG) GFMIs, according to the current limiter dynamics and presents a novel power deceleration scheme. During current saturation scheme, the proposed scheme modifies the active power swing loop structured on d-axes current. The effectiveness of the proposed adaptive FRT has been shown under both strong and weak grid conditions. Under symmetrical and asymmetrical faults with different durations, the performance of the proposed scheme has been checked. The results validate the merits of proposed scheme and its compatibility with GFMI objectives. It has been shown that the proposed architecture enhances the FRT capability of DC-link VSGs; in addition, it supports stable operation in weak MPSs and provides a robust solution for grids with high share of RESs.