Powersystem dynamic voltage stability affected by open‐loop modal coupling between DFIG‐based wind farms and IM loads

• Published in: Journal of engineering (Stevenage, England) England), 2019-03, Vol.2019 (16), p.2514-2519
• Main Authors: Su, Guoyun, Xu, Long, Du, Wenjuan, Chen, Chen, Ji, Yining, Wang, Haifeng
• Format: Article
• Language: English
• Subjects: aforementioned dynamic interaction; asynchronous generators; closed loop systems; closed‐loop interconnected model; damping; DFIG‐based wind farm; doubly fed induction generator‐based wind farms; dynamic voltage instability issues; IM load model; IM loads; IM oscillation mode; IMOM; induction motor loads; induction motors; load dynamic characteristics; modified WSCC 9‐bus system; open‐loop modal coupling; open‐loop subsystems; oscillations; power system dynamic voltage stability; power system stability; power system voltage stability; recovery response; system voltage instability; voltage‐source converter control loop; wind power plants
• ISSN: 2051-3305; 2051-3305
• DOI: 10.1049/joe.2018.8579

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.