Hierarchical Reserve Power Dispatching of Multi-Terminal DC System-Integrated Wind Power Systems for Frequency Control

In the modern power system with increasing risks of frequency instability and possible blackout, frequency support from renewable energy systems is important. For the wind power system (WPS) that is usually integrated into the grid by a multi-terminal DC system (MTDC), the power reserve is usually required for more considerable frequency support capacity. However, the power reserve will frequently change following random offshore wind speed in traditional dispatching causing low system stability. Moreover, applying the same droop parameters may cause more severe wear and low efficiency in different operation conditions of each WPS. This paper therefore proposes a hierarchical reserve power dispatching of multi-terminal DC system-integrated wind power systems for frequency control. Firstly, an allocation method of steady-state reserve power based on historical wind speed and clustering algorithm is proposed to determine reserve power commands instruction of each turbine. Subsequently, a utilization method of transient reserve power is proposed to task each turbine with additional power in frequency support according to operation conditions. Finally, an equivalent multi-terminal system is established in PSCAD/EMTDC to verify and analyze the above methods. The results show that the proposed methods improve frequency stability and system economic performance and system operation stability.