Harmonics Content and Voltage Signal Based Hybrid Backup Scheme for Protection of Microgrid under Different Contingencies

The concept of adaptive protection has been applied to solve the problems of conventional protection approaches for microgrid. However, even in the case of adaptive protection system implementation, many factors can cause malfunction of protection and there is always a possibility of failure of the communication system. A hybrid adaptive protection strategy is proposed in this work to enhance selectivity and reliability of protection system of microgrid. The adaptive overcurrent strategy as primary scheme is backed up by a Total Harmonic Distortion (THD) detection method that takes over protection of the network in the case of failure in the primary method. In order to enhance the reliability of the proposed system during possible communication losses, additional non-communication back up algorithm based on voltage measurement is developed, too. The advantage of the proposed hybrid system is that the system can operate correctly for all types of internal and communication failures, plus prevents unwanted tripping caused by DG integration and dynamic behavior of microgrid.