A method for analyzing the problem of frequent wideband oscillations in grid-connected renewable energy generation systems based on small-world (SW) networks and fast-slow dynamics is proposed, where the mechanism of bursting oscillations in complex power systems has been examined. A direct-driven permanent magnet synchronous generator (DPMSG) and a complex network consisting of multiple DPMSGs connected to the grid were chosen as examples in order to discuss the process of bursting oscillations in a single system with both alternating large-amplitude and micro-amplitude oscillations due to the multi-timescale coupling effect introduced by the disturbance. The process of bursting oscillations in generation nodes spreading among the system nodes, which leads to successive chaotic oscillations of each node of the whole system, was also investigated. The results showed that the bursting oscillations created by the nodes in power generation in grid-connected renewable energy generation systems can lead to oscillation instability of the entire system. Our simulation verified the feasibility and effectiveness of the method proposed in this paper.

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With the increasing proportion of wind power in the power system, a significant threat is posed to the safe and stable operation of regional power grids and the consumption of the new energy by the harmonic interaction effects among wind farms. Aimed at the problem of mechanism for the harmonic interaction between wind farms and the degree of influence, an aggregation equivalence method of wind farms in harmonic power loss is proposed, where the complexity of wind farm equivalence calculation is reduced. Based on this, a harmonic impedance model of multiple wind farms grid-connected system is established, and the mechanism of harmonic interaction influence among the wind farms is revealed. The definition and calculation method of harmonic current interaction factor is presented, where the relationship between the harmonic current interaction and the potential factors, i.e., the coupling impedance, the dynamic reactive power compensation devices, and the number of wind turbines connected to the grid among multiple wind farms, is quantitatively analyzed. Finally, a typical wind farm of new energy base in Northwest China is used as a toy example to verify the effectiveness of the harmonic current interaction factor in the characterization of the interaction strength within multiple wind farms.

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