The Journal of Engineering (Jan 2019)

Power system dynamic voltage stability affected by open-loop modal coupling between DFIG-based wind farms and IM loads

  • Guoyun Su,
  • Long Xu,
  • Wenjuan Du,
  • Chen Chen,
  • Yining Ji,
  • Haifeng Wang

DOI
https://doi.org/10.1049/joe.2018.8579

Abstract

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Power system voltage stability can be significantly affected by load dynamic characteristics. This study examines the impacts of dynamic interaction between doubly fed induction generator (DFIG)-based wind farms and induction motor (IM) loads on system dynamic voltage stability. It is revealed that the IM load model exhibits a recovery response which is accompanied by an IM oscillation mode (IMOM). The IMOM is first demonstrated to be closely related to system voltage stability. Moreover, a closed-loop interconnected model is established, which consists of the following two open-loop subsystems: DFIG; the rest of power system with IM loads. Generally, due to the fast response of the voltage-source converter control loop, the dynamic interaction between the two open-loop subsystems is weak. However, it is discovered that under a special condition named as open-loop modal coupling, the aforementioned dynamic interaction will become tremendous. As a consequence, the damping of IMOM may be degraded substantially which can cause system voltage instability. Therefore, the mechanism of dynamic voltage instability issues is investigated from the perspective of modal coupling. A modified Western Systems Coordinating Council (WSCC) 9-bus system integrated with a DFIG-based wind farm is adopted to demonstrate and validate the above conclusions.

Keywords