A power dispatch approach to enhance dynamic stability for incorporating a large scale PV farm into an isolated grid

Abstract

Almost the majority of power dispatch strategies are based on the economic, energy-efficient or environmental consideration. It has never been studied the effect of power dispatch on dynamic stability of turbine shafts torsional responses. A 9-bus isolated grid is thus studied in the paper by focusing on such an effect by using the DIgSILENT PowerFactory. It is found the dynamic stability will be affected when a large scale photovoltaic (PV) farm is incorporated into an isolated system. When the system is operating under the low load situations, the traditional generators need to operate with a small rating factor to counterbalance the PV power. That might lead to the torsional modes of the traditional generators become unstable. The power dispatch thus becomes very important for maintaining the stability. Here, some of the commonly used power dispatch approaches have been studied to evaluate their effect on dynamic stability of turbine shafts torsional responses. A moderate dispatch approach then is proposed specifically for improving the torsional responses stability under the system low load situations.