A Direct Method to Improve the Load Margin of Power Systems

The complexity of power system operations increasingly demands dynamic safety assessment tools and effective control measures to ensure system stability. Load Margin is an important index to assess system safety, but it usually considers only voltage stability requirements. Load Margin can also be affected by the presence of low-frequency oscillation modes with low damping ratios that are commonly studied in small-signal rotor angular stability. Therefore, it is important to inform the system load margin that considers the voltage stability and small-signal stability thresholds. This paper proposes the use of the direct method to improve the Load Margin of power systems through a control measure. This direct method considers mutual requirements of voltage stability and small-signal stability. A Brazilian reduced power system was used to conduct the case studies and the results achieved are discussed in detail. The proposed method proved to be simple and fast in identifying the load margin and determining the control measure to improve the load margin.