Review on Oscillation Mechanism and Analysis Methods of High Proportion Renewable Energy Power System

A large number of power electronic converters are connected to the grid by a high proportion of renewable energy sources, which leads to endless power system oscillation problems, which is one of the important issues that have received widespread attention in the field of power systems. In order to further study the oscillation problem of high proportion of renewable energy power system, this paper introduces the classification of oscillation mechanism and stability analysis method of renewable energy power system. Firstly, with the help of LC oscillation circuit, the oscillation mechanism and characteristics of negative damping oscillation, forced oscillation (external resonance) and self-resonance (internal resonance) are summarized from an analytical perspective. The results reveal that both positive and negative damping may cause system instability. The oscillation waveforms are similar but the causes are not necessarily the same. In addition, the multi-machine grid-connected system has close oscillation modes, which causes system instability under the slight interaction of certain parameters; on this basis, this paper further introduces the analysis methods of various oscillations. Among them, the eigenvalue method and the impedance/torque method are suitable for analyzing negative damping oscillations. The open-loop mode resonance method mainly focuses on internal resonance. In addition, this paper also introduces the application of complex modal perturbation method and modal analysis method in power electronic grid-connected systems, which are usually used for the analysis of close-mode oscillations and resonances in the field of power systems. Finally, with the increasing impact of the renewable energy input volatility and randomness on the power system, the stability problem is increasingly complex and irregular. This paper puts forward the prospect of the future high-proportion renewable energy power system from the aspects of the discrimination, positioning, analysis theory and method of the oscillation mechanism type. © 2022, High Voltage Engineering Editorial Department of CEPRI. All right reserved.