Small-signal wide-range-frequency oscillation analysis of renewable energy grid-connected system under electromagnetic transient scale.

Renewable energy converters represented by wind power and photovoltaics often cause wide-range-frequency oscillation problems after being connected to the grid. There are currently relatively few studies on multi-converter system state analysis methods. An electromagnetic transient small-signal state space analysis method suitable for grid-following and grid-forming converters access systems is proposed. Equations are constructed based on the dq coordinates of each converter or power supply, combined with the reference phase between multiple coordinate systems. The angle difference is used to construct the coordinate conversion equation, which realizes the writing of the state space matrix of the whole system. Combined with time domain simulation, the correctness and practicability of the proposed method were verified by taking a single-machine infinite system, a dual-machine system, and the IEEE-39 system as examples.