Voltage sag compensation in renewable plant using hydro-pump storage

This paper presents a remote renewable plant with hydro-pump station as energy storage that will also compensate main utility voltage sag. The hydro-pump station receives mechanical power from the water flow between the upper and lower reservoirs. This network-connected plant has a local 9 MW wind farm which uses doubly-fed induction generators (DFIG) as well as a critical load. The hydro pump station is simulated with a generator modelled as a synchronous machine and a hydro- pump modelled as an asynchronous machine. Detailed simulation are performed to investigate the advantages of implementing the hydro-pump storage including its capability in maintaining the voltage and power supply to the critical local load in the event of voltage sag from the main network utility as well as preventing wind farm from tripping during under-voltage fault. This will reduce the cost and maintenance.