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 formation 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.