Improving Performance of Total Harmonic Distortion Based Fault Detection Scheme for Inverter Interfaced Islanded Microgrids

Global warming and environmental concerns have led to increasing penetration of converter interfaced renewable energy resources. One of the main challenges of inverter interfaced islanded microgrids is the fault detection. This paper investigates the performance of total harmonic distortion (THD) based fault detection scheme when various inverter topologies, main current limiting strategies, and different reference frame are employed. Then, based on this analysis, the performance of THD based fault detection scheme is improved using the instantaneous saturation limit and independent control capability in the natural reference frame. The proposed scheme does not mal-operate in the presence of non-linear loads and can distinguish fault condition from load change. Also, using the auxiliary control system, the proposed fault detection scheme is capable of detecting single line to ground fault in three wire system when synchronous/stationary reference frame is employed. Various time-domain simulations verify the effectiveness of the proposed scheme in the case of symmetrical and unsymmetrical faults.