Search

In order to limit the extremely fast rising trend of fault current in a high voltage direct current system, a permanent magnet (PM) biased dc saturated core fault current limiter (DCSFCL) was proposed previously. However, the demagnetization problem of the PM and compromised fault limiting inductance value caused by the inserted PMs are two major issues that need to be solved. In this article, a hybrid-material based fault current limiter (HMFCL) is proposed. First, by means of reconstructing the iron core topology and substituting different soft magnetic materials with their hybrid benefits, the proposed novel HMFCL can present instant change in fault limiting inductance value without threating the safety of the PMs. Then, the Jiles–Atherton hysteresis modeling technique is applied on the HMFCL and its electromagnetic feature is analyzed. The parameters of HMFCL are optimized using genetic algorithm as well. Finally, the effectiveness of the proposed HMFCL is proved by various device and system level simulations as well as a prototype experiment. Results reveal that the proposed HMFCL can limit the fault current by over 80% compared with traditional smoothing reactor. [ABSTRACT FROM AUTHOR]

The inductance of a permanent magnet-biased saturated fault current limiter (PMFCL) increases automatically with the fault current. It can quickly restrain the rising speed of direct current (dc) fault current. However, when the dc circuit breaker (DCCB) opens, the PMFCL will delay the current drop speed and generate overvoltage, which will increase the voltage stress on the DCCB. In this article, a new type of fast-response FCL (NFCL) is proposed. It has the advantage of improving the fault current drop speed. Besides, it can reduce DCCB overvoltage, thus protecting the expensive insulated gate bipolar transistors in the DCCB. In addition, it greatly reduces the energy absorption in the DCCB, thus reducing its manufacturing cost. The NFCL operates automatically without a control device, which means that it responds faster. Moreover, the diode is on the low-voltage side, meaning that insulation manufacturing cost can be reduced. First, the working principle of NFCL cooperation with the DCCB is introduced. Then, the main electromagnetic parameter design requirements of the NFCL are analyzed. Their feasibility is verified by electromagnetic circuit simulation, and a prototype is built and tested. Finally, the experimental and simulation results show that NFCL can improve current drop speed effectively. [ABSTRACT FROM AUTHOR]

A DC system saturated core fault current limiter (DCSFCL) was proposed to limit the fast rising trend of fault current in HVDC system. However, traditional method to calculate and design the DCSFCL tend to neglect leakage flux around the permanent magnet (PM), leading to large calculation error and inappropriate design procedure. The novel contribution of this paper is that it proposed a modularization method to analyze the permeance of both PM and adjacent air. Hence, the leakage flux effect is considered properly and a more accurate permeance matrix can be derived in a pure mathematical way. In this case, DCSFCL can be calculated much faster than the FEA simulation program with a promising accuracy regarding fault limiting performance. More importantly, design flow of the DCSFCL and related PM biased devices was given as well. Calculation result shows that inductance value calculated by the proposed method has less than 1% error compared with fine meshed FEA simulation result and about 20% increase in accuracy compared with traditional method that neglects PM leakage flux effect. Prototype of the DCSFCL was also built and experimental tests were carried out to verify the correctness of the proposed method. [ABSTRACT FROM AUTHOR]

When the fault current in high voltage direct current (HVDC) systems rises to a higher level, the DC circuit breakers will have either insufficient capacity or will require larger sizes with increased costs. Fault current limiters (FCLs) can reduce the turn-off stress and the stringent requirements on breakers, thereby also lowering their cost. The use of saturated core FCLs, which have fast response times and low power loss, is a promising approach for this issue. However, the parameter design principles for this kind of FCL has so far not been discussed in the literature. The design is often based on reactors that does not consider the transient performance. In this study, an optimized design method for permanent magnets saturated core FCLs in HVDC transmission systems, is proposed. The constraint conditions, parameter optimization and modification steps are discussed, and an optimized FCL design is obtained with the lowest cost and expected current-limiting function. Both simulations and experiments are conducted, and the results demonstrate the validation of the proposed method. Finally, a cost evaluation among main types of inductive FCLs is carried out and suggestions for scaling up saturated core FCLs to HVDC applications are given. [ABSTRACT FROM AUTHOR]

Large fault direct current with fast rising speed has always been a significant threat to high voltage direct current systems. Fault current limiters (FCLs) are one of the most promising solutions. However, the biased permanent magnets (PM)s in traditional FCLs have large magnetic reluctance that causes FCLs to have small inductance changing ratios when a fault occurs. In this study, a novel three-limb topology of a saturated iron core-type fault current limiter (TSFCL) is proposed and a central PM bias limb is inserted to force flux flow through this limb. Therefore, the inductance changing ratio is greatly enhanced and the steep rising trend of fault current will be restrained effectively. The operating principles and characteristics of the TSFCL are analyzed to verify the deductions. Moreover, different lengths and cross-sectional areas of the inserted PM are tested and optimization study is carried out. The results show that the clipping inductance has a 55% increase compared with a traditional two-limb model. Moreover, compared with the existing smoothing reactor and traditional two-limb model, proposed topology can decrease the fault current by 45% and 16% within 5 ms, respectively. Finally, a typical HVDC system was built and the effectiveness of proposed TSFCL was verified. [ABSTRACT FROM AUTHOR]