Wind-thermal generation coordination in multi-terminal HVDC-connected AC systems for improved frequency support

The large-scale penetration of renewable generation into power systems has required an integration of wind and conventional thermal generation. This has been supported by high-voltage direct-current lines for bulk power transmission as wind generation is normally located far away from the load centres. The participation of wind generators in primary frequency regulation and stability has become an important challenge due to the intermittent nature of wind. This is especially relevant due to the slow response from thermal generation and, therefore, the coordination between these two generation sources becomes of utmost concern. In this work, a dual droop control method for a voltage source converter based multiterminal DC grid (MTDC) is proposed, where bulk power is transmitted from an integrated wind-thermal generation park. The results in this paper show that the proposed method can be used to enhance the frequency stability and primary frequency response of the mixed AC/DC system. This is achieved by mitigating wind power fluctuations through the regulation of power flows into and from the MTDC grid.