Coordinated Control of a Dual Grid Forming Unit Connecting an Offshore Wind Farm and an E-STATCOM for Damping and Inertia Provision

Future weak power grids pose significant challenges for the operation of grids interconnecting power converters. Recently developed dual grid-forming strategies for modular multilevel converters allow simultaneous ac grid voltage for-mation and dc voltage control. However, these strategies have limitations in providing damping and inertial power. Motivated by the grid-forming services requirements by transmission system operators, this work proposed the cooperative operation of a static synchronous compensator with energy storage in parallel with an HVDC connected offshore wind farm to provide the required inertia and damping power, forming a virtual power plant. The obtained system exhibits an enhanced performance and stability, obtaining frequency Nadir and Rate of Change of Frequency improvements of 65.8% and 76.2%, respectively. In addition, wind farm power intermittency is reduced, filtering out wind power variations over 0.25 Hz.