Suppression of Short-Circuit Fault Current Level in a Multi-Terminal Wind Farm VSC-HVDC System using Resistive-Type DC Superconducting Fault Current Limiters

摘要

High voltage direct current (HVDC) systems are one of the major solutions to transmit electric power in minimum loss and optimum cost. HVDC systems have many types of which voltage source converter based HVDC systems (VSC-HVDC) are one of the many types of HVDC systems. These systems are extremely useful in order to integrate renewable energy resources into a common grid. Although HVDCs have several advantages, they are vulnerable to DC short circuit faults. AC circuit breakers are able to cut off the faulted branch at t=t0 when the magnitude of voltage is zeros, on the other hand, DC voltage has no zero points to be cut off by a circuit breaker. Despite several prototypes of DC circuit breakers (DCCB) had been deployed, there is any version of these circuit breakers which is commercialized and as it has been explained above, it is because of their inability to mitigate fault currents. To overcome the aforementioned problem, utilization of fault current limiters (FCL) is vital to limit the fault current level. These devices apply massive impedance to the faulted region to suppress the fault current passing through the network. Superconducting fault current limiters (SFCL) are the new type of FCLs, which put superconductors in use to limit the fault current passing through grids. In this regard, SFCLs are purposed as one of the solutions of HVDC systems protection and their ability in mitigation of fault currents are tested in an HVDC system. This system is a multi-terminal HVDC system with 2 kA of rated current. For the purpose of finding the best performance of DC SFCL, the NSGA II algorithm is applied in simulations, which are accomplished in SIMULINK/MATLAB.