Date of Award

May 2013

Degree Type


Degree Name

Master of Science



First Advisor

David C. Yu

Committee Members

Hossein Hosseini, Chui Law, David C. Yu


P-Q Region, Voltage Stability Assessment, Wind Power


Voltage stability assessment (VSA) is a significant part in planning and operating of the power system. As one of the classic static VSA method, the P-V curve is widely used in identifying the weak buses in one power system. Normally, there is a required range of bus voltage variation that restricts load with fixed power factor within a maximum value. The loading margin can be defined as the distance between the operating point and the maximum load. The proposed P-Q region, which defines safe region for voltage stability, is more effective and intuitional when applying to VSA compared to the P-V curve. However, it is necessary to verify the feasibility of the novel method before implementing this method in system incorporating wind power penetration. Simulations using MATPOWER and contrastive calculating results prove the accuracy of P-Q region. Also, the calculation method of the probability of output power of the wind farm is proposed. In this approach, the P-Q regions at different levels of wind power penetration are presented and discussed. Moreover, the P-Q region is proposed as a tool to determine the best location to place a wind farm as well as assess the safe operating zone of the reactive power with respect of the variable real power output. Finally, the expected loading margin validates the effectiveness of the proposed P-Q region method and its applications when incorporating wind power.