Determination of Power System Voltage Stability Using Modal Analysis

Voltage instability within the power system has severe consequences including a wide-spread low voltage profile and system blackout. The development and use of accurate methods to predict incipient voltage instability is crucial in preventing such voltage collapse situations. A comparison of the common steady-state methods for voltage stability analysis was undertaken, along with a brief examination into the dynamic approach. Special attention is given to the modal analysis technique presented in [2], which provides both a relative proximity of the system to instability, as well identifies the key contributing factors to instability. A PC-based MATLAB prototype application was developed to assist power system operators in the assessment and analysis of the voltage stability of a power network, at any given operating point, using the modal analysis technique, in addition to useful features such as power flow analysis and traditional V-P/V-Q analysis. Using multiple practical test cases on the IEEE 30 bus system the modal analysis technique was shown to provide an accurate estimate of the system proximity to the voltage stability limit, and to consistently and correctly predict the critical buses and the weakest branches in the transmission system. These results clearly demonstrate the suitability of modal analysis technique as applied to voltage stability analysis, and the need for closer analysis, possible refinement to the method and incorporation into more commercial analysis packages.