A Grid-forming Control Strategy to Improve the Inertia Supporting Capability of the VSC-HVDC

Oriented the VSC-HVDC transmission system integrated with high-penetration renewable energy, the paper presents a grid-forming control strategy which utilizes DC capacitor’s dynamics to synchronize grid. On the basis of DC-side voltage tracking grid frequency, the supplementary inertia supporting and frequency adjustment control method is presented. In order to increase the grid-supporting capability, a method of regulating the inertia control and frequency regulation coefficients dynamically is proposed according to the measured DC voltage. The research result shows supplementary inertia supporting and frequency adjustment methods are able to enhance grid-supporting capability of VSC-HVDC through the wind turbines’ stored kinetic energy. Comparing the inertia supporting and frequency regulation strategy with fixed coefficients, this presented method is able to further strengthen the grid’s frequency stability under conditions of wind speed fluctuations. Finally, simulations based on PSCAD/EMTDC are built to prove the validity of grid-forming and inertia supporting strategy.