Fault identification scheme for UPFC compensated transmission line based on characteristic voltage active injection

Abstract

When a fault occurs at Unified Power Flow Controller (UPFC) compensated transmission line, the traditional auto reclosing scheme cannot identify the fault characteristics, and thus reclosing on a permanent fault would cause the second strike on the power system within a short period. To solve this problem, this paper proposes a fault identification scheme based on the active injection of the characteristic voltage by the control of UPFC. Firstly, after the circuit breakers on both sides of the faulty line have tripped, the converter on the series side of the UPFC is switched to the additional control mode. Then, the characteristic voltage is actively injected into the faulty line through the series transformer. Based on the active injection, the fault characteristics can be identified through the difference of characteristic voltages and currents under different faults. Therefore, this scheme could prevent the circuit breaker from reclosing on permanent faults and thus enhance the stability and safety of the system. Finally, the simulation results in PSCAD/EMTDC verify the robustness and effectiveness of the proposed scheme.