A Nonlinear Backstepping Control Scheme for Rapid Earth Fault Current Limiters in Resonant Grounded Power Distribution Systems: Applications for Mitigating Powerline Bushfires

This work presents a nonlinear backstepping control scheme for rapid earth fault current limiters (REFCLs) in resonant grounded power distribution systems to mitigate the severity of powerline bushfires. The main feature of the proposed control scheme is that it quickly eliminates both active and reactive components of the fault current to make it zero for reducing the chance of igniting bushfires. The nonlinear backstepping control scheme is employed on the dynamical model of a REFCL equipped with a T-type inverter. The desired tracking of the fault current is ensured with the proposed scheme by appropriately injecting the current to the neutral point. The performance of the controller is evaluated in terms of the fault current and faulty phase-to-ground voltage under different fault conditions while following the standard criteria for the practical operation. The fault current compensation capability of the proposed scheme is evaluated for both low and high impedance faults. Simulation results in software and processor-in-loop platforms clearly demonstrate the fault current is limited to a value much lower than its desired value of 0.5~A in less than 1~s which means that the chance of igniting bushfires will be reduced with the proposed controller.