Assessment of voltage stability in microgrid

On-line security assessment techniques use real-time measurements from different locations in a power system and continuously update the security of the system. The introduction of Phasor Measurement Units (PMU) and their use as a powerful measurement tool in power systems has made possible for fast accurate algorithms. The simulated PMU data is used to determine the voltage indices being considered in this work to predict the stability of the Microgrid. The on-line assessment is supposed to capture the continuous changes of operation states of power system i.e. to assess if the dynamic state of power system is acceptable or not. The islanding detection time is an important factor for the smooth transition to islanding mode. For this purpose voltage security indices can be used to promptly send signals to the Microgrid Control Centre for islanding. In this work initially a transient stability analysis is performed on a Microgrid test bed using DIgSILENT and the simulation results are analyzed. The indices taken for the study Voltage Collapse Proximity Index (VCPI), Voltage Security Index (VSI) and Power Transfer Stability Index (PTSI) are compared. The credibility of these indices is validated on a typical utility system from Calicut, Kerala. From the simulation performance of the indices are analysed for three particular cases.