Fault nature identification and location scheme for distribution network based on active injection from IIDG

•This paper proposed a signal injection method. The modified LCL filter is used to shorten the injection signal rise time. The injection signal is generated by switching on IGBTs in an IIDG for a short period of time.•This paper has derived the traveling wave (TW) characteristics under signal injection. After signal injection, if there is a permanent fault on the feeder, the aerial mode 1 or aerial mode 2 will not remain at 0. And the first mutation point is caused by the reflected TW at the fault point.•The paper proposed a fault nature identification and fault location scheme. The approximate entropy (ApEn) is utilized as the identification criterion, and the fault distance is further calculated according to the mutation point extracted by wavelet transform.•The proposed scheme uses almost no additional equipment and can detect all faults except for three-phase faults. Compared to other single-ended fault location schemes, the proposed scheme has smaller error. Simulations with different fault resistances and fault distances verify the high sensitivity of the scheme. In view of the difficulty in passively identifying the nature of faults in distribution networks and the high equipment cost of existing active detection schemes, a permanent fault identification and location scheme using an inverter-interfaced distributed generator (IIDG) connected to feeders for signal injection is proposed. After the faulty feeder is isolated, the power electronics in the IIDG are switched on for a short time and a voltage signal is injected into the feeder through the modified LCL filter and grid-connected transformer. The analysis shows that the aerial mode voltage of the feeder will not remain 0 under permanent faults. A highly sensitive criterion with fixed thresholds is constructed using approximate entropy (ApEn) to identify fault nature. Then the fault distance is further calculated based on the detected mutation point of the aerial mode voltage under permanent faults. The correctness of the theory and the effectiveness of the scheme are verified in PSCAD/EMTDC simulations. © 2017 Elsevier Inc. All rights reserved.