Influence Analysis of Sub-Synchronous Oscillation on Commutation Failure for LCC-HVDC Systems

With the rapid development of renewable energy, sub-synchronous oscillations have become a new stability issue caused by the interaction between the control of renewable energy and the power grid in renewable energy integrated receiving-side HVDC system. The appearance of sub-synchronous oscillations, due to the large-scale integration of renewable energy into the receiving-end HVDC system, can affect the voltage quality of the receiving-end, resulting commutation failure, thereby affecting the safe and stable operation of the LCC-HVDC system. Currently, the research on the mechanism of impact of sub-synchronous oscillations on commutation failure is still in its infancy. In this paper, through analyzing the commutation process, the research shows that sub-synchronous oscillations can cause commutation failure by affecting the amplitude and phase of the commutation voltage, resulting in an insufficient area of the commutation voltage-time area. A sub-synchronous oscillation impact factor (SOIF) is proposed, which can quantify the impact of each frequency component of sub-synchronous oscillation. The impact of each sub-synchronous oscillation frequency on commutation failure is analyzed based on the SOIF. Finally, the effectiveness of the proposed SOIF is verified based on the CIGRE HVDC standard model.