Power System Stability and LVRT Capability Enhancement of Grid Connected Hybrid System with UPFC and Energy Storage System

The present day power system network is having more and more renewable energy resources (RES) included into it, day by day. PV-Wind hybrid power generation systems are promising energy sources, because they are able to generate electric power in remote areas and complement the demand of conventional electrical power systems. But the intermittent nature of these sources adversely affects the power system stability. During the initial stage of introducing PV, Wind systems to the electrical energy market, they were allowed to be disconnecting from the grid during fault events in the grid side to avoid any possible damages. Currently, the developed grid codes require them to ride-through intermittent fault conditions to remain connected and support the grid under such events. This will assure sustainable power delivery to the grid during faults and abnormal operating situations. A cost effective approach to improve the Fault Ride Through (FRT) capability of the existing PV-Wind hybrid systems is by connecting fexible ac transmission system (FACTS) device to the Point of Common Coupling (PCC). Among all the FACTS devices, UPFC performs this operation well. By controlling the UPFC as a virtual inductor can lead to increase the voltage at the PCC during the fault clearing while all other devices can only recover voltage after fault clearing at the PCC. The back-up energy supply system incorporated with UPFC is providing a complete control of real and reactive power at the same time and hence is competent to improve the performance of an electrical power system. Thus the backup energy supply unit integrated is superconducting magnetic energy storage (SMES), because, SMES based UPFC is much better in terms of transient stability and lvrt capability improvement, maintaining constant DC bus voltage.