SSOs caused by OLMOC in a power system with the PMSGs for wind power generation

Abstract

The authors study the modal condition, under which the sub‐synchronous oscillations (SSOs) may be caused by the grid integration of a permanent magnet synchronous generator (PMSG) in a power system. The study is conducted by using a closed‐loop interconnected model of the power system with the PMSG, which consists of a PMSG subsystem and a subsystem of the remainder of power system (ROPS). The modal condition is the nearness of an SSO mode of open‐loop PMSG subsystem to an SSO mode of open‐loop ROPS subsystem on the complex plane. It is named as the open‐loop modal coupling (OLMOC). The study shows that when the OLMOC takes place, strong sub‐synchronous interactions (SSIs) are induced by the PMSG and may very likely decrease the damping of SSOs in the power system. A formula to approximately evaluate the degree of damping decrease caused by the OLMOC is derived in this study. Hence, the mechanism of why the PMSG may jeopardize power system stability is revealed from the viewpoint of open‐loop modal condition. Study cases are displayed to confirm the analytical investigation. They indicate that the growing torsional SSOs and the SSIs between the PMSGs take place when the OLMOC occurs.

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Identifiers

DOI

10.1049/iet-rpg.2018.5160

Journal

IET Renewable Power Generation

Year

2018