Enhancement on the Fault Ride through Capability of Power Distribution Systems Linked by Distributed Generation due to the Impedance of Superconducting Fault Current Limiters

Abstract

Recently, studies on connecting distributed generation (DG) to power distribution systems through DC links have been actively conducted. When a fault in feeder of this power distribution system occurs, a voltage dip can happen in the grid. In order to prevent voltage dips, there are several solutions such as the application of a superconducting fault current limiter (SFCL). If a SFCL with a larger impedance is applied, the voltage dip of the grid is effectively prevented. However, this action can bring about the malfunction or the delayed operation of the over-current relay (OCR) due to the decreased fault current, which causes another problem of protection coordination between the protective relays. On the other hand, if the impedance of the SFCL is too low, excessive reactive power is supplied by the fault ride-through (FRT) regulation and the active power is reduced. This causes an active power imbalance on the DC link and increases the DC link’s voltage. As previous solutions to prevent the rise of DC links’ voltage, the deloading method and the application of a chopper resistor have been suggested. In this paper, a technique called active power tracking control (APTC), was proposed to suppress the rise of DC links’ voltage. Case studies considering the impedance of SFCL in the constructed power distribution system were carried out, and the rise of DC links’ voltage could be effectively suppressed without any significant delay in the operation of the OCR. This study is expected to solve both the voltage dip of the grid and the rise of DC links’ voltage when distributed generation is connected to a grid.

Impacts of a LVRT Control Strategy of Offshore Wind Farms on the HTS Power Cable

“…and are the dq-axis components of the stator voltage that are proportional to the modulation signals ( and ), as in (22) and (23). , The dynamics voltage equations of the PMSG expressed in the dq-reference frame is given by…”

“…where R s is the stator resistance; ω r is the rotor angular frequency; λ PM is the magnet flux of PMSG; i sd and i sq are the dq-axis components of the stator current; L d and L q are the dq-axis components of the stator inductances; V sd and V sq are the dq-axis components of the stator voltage that are proportional to the modulation signals (m sd and m sq ), as in (22) and (23).…”

“…Energy storage systems (ESSs) connected with the DC-link capacitor were used to absorb the excess energy during fault condition [18][19][20], preventing overvoltage of the DC-link and improving the LVRT capability of the wind turbine generator (WTG). Fault current limiters (FCLs), which limit the transient current by changing these impedances, have been proposed to improve the LVRT capability [21][22][23]. In addition, coordinated control strategies of converters in WTG for LVRT improvement have been proposed [24,25].…”

Study on Malfunction of OCR Due to Penetration of DER into Power Distribution System with SFCL

“…To solve this problem, a correction method using the voltage component of SFCL and a method using SFCL impedance correction have been proposed. However, the correction for the fault current contributed by the DER is not perfect [12][13]. In this paper, fault simulation was performed to analyze the type of fault current contributed by DER and its effect on OCR operation.…”

Development of an Intelligent System for Distance Relay Protection with Adaptive Algorithms for Determining the Operation Setpoints

“…According to the North American Electric Reliability Council, in 74% of cases, the cause of severe accidents in power systems was incorrect actions of relay protection during the development of an accident. Therefore, the reliability of the entire power system largely depends on the reliability of relay protection [1][2][3][4][5]. The drastic consequences of emergencies force us to look for ways to increase the stability of the device operation at OHPTL.…”