PSS Tuning of a Radially Connected Hydro Power Plant of Eastern India Using SMIB Model and Phase Compensation Technique

Power systems are very often exposed to large disturbances such as loss of load, loss of transmission lines, and loss of large generating units. Now the main challenge in operating large power system is that running all the generators synchronously even after these disturbances. Generally following a large disturbance different generators respond differently to the disturbance and low frequency oscillation among the generators comes into the picture. Hydro power plants are generally located to very remote hilly area and connected to the electrical grid via long radial transmission lines. Small signal stability issue is sometimes get triggered following some disturbance or during system wide inter-area oscillation. In this paper a radially connected hydro generating station “A” of Sikkim having 3X170 MW installed capacity is studied. Generating station is connected to the grid at a pooling station via two 400 kV twin moose lines. Machine is currently equipped with static excitation and one simple Power system stabilizer model at the site. However excitation system has the provision of activating complex stabilizer model also. Analyzing various past disturbances and low frequency events in the Indian power grid it is found that the performance of the above mentioned generators in damping the local and inter-area oscillation is poor and ranges between 0 to 7 % damping for all the modes. This paper aims at improving the damping of oscillation to 15-25%.