Analytical Approach for Novel Temporary Frequency Support Control of VSC HVDC

The grid support function by DC devices such as static synchronous compensator (STATCOM) or high-voltage direct current (HVDC) systems is becoming more important owing to renewable energy integration. This study proposed an energy-effective temporary frequency support strategy using a voltage source converter (VSC) HVDC. The frequency response of the HVDC was analyzed to maintain a flat frequency and a system frequency response model with the HVDC model was employed for this purpose. Subsequently, a simplified HVDC frequency support strategy aimed at achieving quasi-flat frequencies, which can be easily implemented within an HVDC controller, was proposed. The analysis indicated that a ramp response constitutes a sufficient condition for maintaining flat frequency nadir. Consequently, two distinct frequency support strategies were formulated. These strategies were validated through numerical simulations and were implemented within an HVDC outer controller. The effectiveness of the proposed support control strategy was demonstrated through PSCAD simulations based on various case studies. In addition, an inertial-deviation scenario was examined to validate the practical application of the proposed control strategy.