An oscillation source tracing method for renewable energy flexible DC transmission systems based on interaction energy weight factor and energy flow path deduction

• Quantitatively characterized interaction energy impact-degree by Modularity Q function. • Oscillation energy conduction link at the sending/receiving end is accurately described. • Revealed main oscillation-inducing paths through multi-region searching method. • Clarified that AC lines of PMSG/PV are with the most significant oscillation effect. • Oscillation sources are traced accurately and much faster by MPN-Tracker algorithm. This paper proposed an oscillation source tracing method based on the interaction energy weight factor and graph theory deduction, concerning the oscillation source tracing in flexible DC transmission systems connected with new energy stations. The proposed method can depict the interaction pathways of dynamic energy, effectively identify the key oscillation-dominant links and the propagation paths within the system, and enable more precise analysis of oscillation excitation mechanisms and their propagation processes. Firstly, according to the diverging rate and accumulating gradient of the interaction energy between different energy subsystems, the interaction energy weight factor characterizing the influence of oscillation is constructed. On this basis, a subsystem partitioning method based on the modularity Q function of the weight factor is proposed, and the edge betweenness centrality sorting processing is carried out for each partition. According to the modularity Q function, the key energy subsystems of oscillation are located. The key energy subsystems are divided into the key energy subsystems that induce the oscillation and the key energy subsystems that are affected by the oscillation. By using the improved MPN-Tracker path searching method, the transmission routes of the oscillation interaction energy between different key energy subsystems are depicted. Finally, the proposed method is verified on the RT-Lab semi-physical experimental platform. From the results, the proposed oscillation source tracing method can effectively locate the oscillation sources in the test system. When a transient fault occurs on the AC transmission line of the receiving-end master station, the key energy subsystem that induces the oscillation is the phase-locked loop (PLL) of the receiving-end master station. The key energy subsystems affected by the oscillation include the PLL of the receiving-end slave station and the d-axis subsystems of the sending-end AC transmission lines.