3.3_Jain: Comparison of Grid forming control strategies in the scope of BSR by OWPPs

High volume integration of renewable energy like large offshore wind power plants (OWPP) has pushed the modern power system closer to its critical dynamic stability limits due to its inherent variability & availability uncertainty, decoupling due to power electronics interface and system-expansion constraints. Thus, an improper handling of certain partial failures can easily lead to severe chain reactions, which ultimately increases the risk of wide area blackouts due to stronger linking of national power systems.

In contrast to conventional blackstart units (BSU), large OWPPs can provide fast and fully controlled, high power, environment-friendly blackstart capability. Moreover, grid-forming wind turbines (WT) need not only wait for network restoration to complete like traditional grid-following WTs, but can also participate & support the network energization & load restoration process in the earlier stages, thus reducing the overall impact of a blackout. Additionally, blackstart-able WTs can produce power to sustain themselves and avoid risk to their health, especially when offline for long durations. This minimizes the use of diesel generator and provides cost benefit.

Since, grid-forming is a necessary capability for WTs to support the blackstart restoration process, this paper aims at presenting a conceptual classification of the various existing grid forming control strategies. The different control techniques that will be studied are virtual synchronous machine based (VISMA, VSM), power synchronization control (PSC, Synchronverter), Distributed PLL-based, direct power control (DPC, enhanced DPC) and Synchronous machine matching.

Furthermore, the different control techniques will be implemented in an aggregated wind farm model for comparison in the scope of blackstart restoration and islanding operation using OWPPs. The main aim of this study will be to ensure controlled network energization and stable load recovery of the offshore collector grid for durations sufficiently long enough that OWPPs be considered as BSUs by TSO for early participation in power system restoration.