Economic-emission load dispatch in renewable integrated system under availability based tariff (ABT) environment

Grid discipline is very important for smooth and secure operation of any power system. ABT is one such commercial tool which improves the grid discipline by suitably re-dispatching the participating generating units depending upon the frequency of the grid at different intervals. This paper presents a load dispatch model based on ABT, where any unscheduled interchange (UI) from generating units, which helps in maintaining nominal frequency on the grid, invites higher incentives. Besides load variations, the integrated unpredictable renewable sources like the wind and the solar units cause significant UIs and consequently vary the system frequency. The optimum sized pumped storage (PS) unit used in the generation mix compensates these variations, and reduces the UIs and emission. The study has been carried out for restructured power system with significant renewable sources integrated in it. The system frequency is predicted considering the variations in the wind power and in the load demand, and scheduled interchange (SI) power is decided based on the predicted frequency. The grid power schedule decided on the basis of predicted frequency is very useful in minimizing the UI charges. The PS unit improves the frequency profile by suitably adjusting its operation as pump and as generator, which minimizes the cost paid as UI charges. The results of the model proposed have been demonstrated on modified IEEE-14 bus system data.