Expansion of high-voltage dc (HVdc) systems to multi-terminal HVdc (MT-HVdc) systems/grids considerably increases the short circuit levels. In order to protect the emerging MT-HVdc systems/grids against fault currents, proper dc fault current limiters (FCLs) must be developed. This paper proposes an innovative high inductance solid-state dc-reactor based fault current limiter (HISS-DCRFCL) to be used in HVdc applications. In fact, during the HISS-DCRFCL normal operation, its inductance value is extremely low, and its value becomes considerably high during the fault period, which decreases the fault current amplitude. The proposed HISS-DCRFCL performance is analyzed by MATLAB/Simulink and the simulation results are verified and confirmed by laboratory experimental results using a scaled-down laboratory prototype setup.

This paper proposes a novel bridge-type solid-state fault current limiter (BSSFCL) based on one series reactor which operates in ac and dc modes. The proposed BSSFCL includes a rectifier bridge with a reactor. This reactor is used as a dc reactor in normal operation mode and as an ac reactor in fault conditions. The advantages of the proposed BSSFCL over the existing dc reactor-type FCLs are its negligible impedance in normal operation mode and its high impedance during a fault interval using simple and novel switching. In other words, during the normal operation mode, the proposed BSSFCL operates in dc mode and in the fault interval, its topology is changed to the ac mode. This switching decreases the switching transient recovery voltage and introduces considerable impedance during the fault period. MATLAB/Simulink software is used for simulations and a prototype is designed and tested for results verification, and to show the performance of the proposed BSSFCL.

High voltage direct current (HVDC) systems are efficient solutions for the integration of large-scale renewable energy sources with the main power grids. The rapid development of the HVDC grid has resulted in a growing interest in DC circuit breakers (DCCBs). A fast and reliable circuit breaker is a necessary requirement in the development of large scale HVDC grids. This paper provides a comprehensive review and survey of the HVDC CBs and discusses potential research directions. Operational principles and the main features of various DCCBs are described and their merits and shortcomings are also highlighted.

In this paper, a novel solid-state fault current-limiting circuit breaker (SSFCLCB) based on a series resonance LC tank is proposed. Since the series configuration of the resonance structure (a capacitor and a reactor) of the SSFCLCB is invisible during normal operation mode, it shows negligible impedance in the line. In fault conditions, the SSFCLCB topology changes to a rectifier bridge and feeds the resonance structure with rectified ac voltage. With the rectified voltage, the series capacitor is charged and, as a result, the faulty line is opened and the fault current is seized. Hence, the suggested SSFCLCB cannot only limit the fault current but can also open the faulty line and acts as a circuit breaker. For confirmation of these aspects, simulations are performed using MATLAB software. Also, a prototype structure is designed and built for results confirmation. This experimental setup is established to prove that SSFCLCB has excellent performance in its startup, normal operation, and current-limiting/breaking conditions. The results show that the SSFCLCB has the ability to improve distribution network reliability and it can decrease the network fault current level successfully.

This paper studies a novel transformer-based solid state fault current limiter (TBSSFCL) for radial distribution network applications. The proposed TBSSFCL is capable of controlling the magnitude of fault current. In order to control the fault current, primary winding of an isolating transformer is connected in series with the line and the secondary side is connected to a reactor, paralleled with a bypass switch which is made of anti-parallel insulated gate bipolar transistors. By controlling the magnitude of ac reactor current, the fault current is reduced and voltage of the point of common coupling is kept at an acceptable level. Also, by this TBSSFCL, switching overvoltage is reduced significantly. The proposed TBSSFCL can improve the power quality factors and also, due to its simple structure, the cost is relatively low. Laboratory results are also presented to verify the simulation and theoretical studies. It is shown that this TBSSFCL can limit the fault current with negligible delay, smooth the fault current waveform, and improve the power quality.