With the increasing deployment of offshore wind power plants (WPPs), the grid-forming (GFM) battery energy storage system (BESS) has recently emerged as an attractive solution to improve the dynamic performances of WPPs. However, the control interactions of the GFM-BESS and offshore WPP, under different grid strengths, tend to complicate the controller-parameter tuning. This paper presents a modeling method for analyzing control interactions of offshore WPP and GFM-BESS, which sheds clear insights into the critical controller parameters to the system dynamics. Differing from conventional methods, a frequency-domain model of GFM-BESS, obtained by taking the Laplace transform of the corresponding state-space model, is developed first. This allows the impedance model of offshore WPP, including a black-box model of long transmission cable, to be flexibly integrated. Based on the model, both closed-loop transfer-function and pole-based dynamic analyses are then performed. Electromagnetic transient simulations corroborate the effectiveness of the model and analysis.

Grid-forming (GFM) converters are a promising solution to enable large scale integration of renewable energy sources into the power system. However, due to the intrinsic voltage-source behaviour of GFM converters, current limitation during large grid disturbances is challenging. This paper presents a novel limitation strategy that preserves the GFM properties of the converter and at the same time effectively limits the converter current to the desired value. Through the limitation of the converter's internal voltage, stable operation even during faults and in case of large frequency disturbances in the grid is achieved. Experimental results show the effectiveness of the proposed current limitation strategy in case of various grid disturbances.

The past years have seen a rapid increase in the deployment of large-scale wind power plants (WPPs) in transmission grids. The dynamic interactions between wind turbines (WTs), power transmission cables, and other electrical infrastructure of WPPs pose challenges to the stability and quality of electricity supply, particularly under diverse grid conditions. The interactions tend to be worsened with longer transmission cables [1] . A harmonic instability issue that features a 451 Hz resonance is manifested in an offshore WPP located in the North Sea [2] . During a submarine cable outage, an offshore WPP situated in England encountered instability due to sub-synchronous resonance at around 8.5 Hz [3] .

In this survey paper, applications of medium voltage direct current (MVDC) to distribution substations are discussed and compared to conventional ac for power conversion from transmission voltage levels to distribution voltage levels. Technical changes in the substation due to the dc equipment, efficiency of the substation, and protective measures are major aspects to consider in the MVDC concept development.

This article proposes a selective harmonic voltage control approach for the static synchronous compensator (STATCOM) deployed in wind power plants (WPPs). The method enables STATCOM to mitigate voltage harmonics at the point of interconnection of WPP without using the high-voltage sensor. Further, a passivity-based design of the proposed control method is developed to eliminate the negative resistances around the concerned harmonic components, which allows robust harmonic voltage damping under the different passive grid impedances. The effectiveness of the approach is elaborated by theoretical analysis and validated by electromagnetic simulations.

The aim of this paper is to present a grid-forming (GFM) control strategy with a novel active-power loop (APL) structure facilitating limitation of active power while providing maximum available inertial support. This is achieved by decoupling the synchronization duties of the APL from the inertial support. The latter is provided by calculating the active-power reference through a dedicated inertia-emulation loop (IEL), which is connected in cascade with the APL. The effectiveness of the proposed method is demonstrated through laboratory experiments including frequency transients of varying size and unbalanced operating conditions.