HYBRID ISLANDING RECOGNITION SCHEME FOR PV DRIVEN DISTRIBUTED GENERATORS USING RATE OF FREQUENCY DEVIATION AND SUB-HARMONIC INJECTION IN Q AXIS CURRENT

Distributed Generation (DG) has become widely acceptable and inevitable part in electrical power sector. Firstly, because of their emission free operation and secondly due to their ability to reduce the transmission loss considerably, especially when power is to be transmitted to remote areas. Grid Connected DG (GCDG) operation cannot be avoided as the power transfer in both ways is necessary and highly useful. Though the GCDG operation is advantageous, certain challenges and difficulties are to be faced. Involuntary islanding is one of the challenges which is to be addressed in GCDG operation. The unplanned disconnection of utility grid from a GCDG causes the DG, to get isolated. It is mandatory to recognize involuntary islanding as quickly as possible due to severe drawbacks and health hazards to working personnel. In the literature, there are several Islanding Recognition Schemes (IRS) available. In this paper a hybrid IRS, using Rate of Frequency Deviation (ROFD) measurement and Sub Harmonic Injection (SHI) in q axis current is presented. MATLAB/SIMULINK software is used to simulate this IRS in a 50kW Photo Voltaic (PV) based GCDG. Necessary waveforms to validate this IRS are presented