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The current-limiting performance of the smoothing reactor is weak. The traditional saturated core-type fault current limiter (TFCL) is better, but will cause the dc circuit breaker (DCCB) to endure high overvoltage, energy absorption and also increase the current fall time. When DCCB recloses on the permanent fault, the whole dc system will face a harmful second shock that cannot be solved effectively by TFCL. To solve the above problems, a secondary active limiting fault current limiter (SAFCL) topology is proposed. It can reduce the DCCB overvoltage and energy absorption greatly. Meanwhile, it can store fault energy and uses it to active limit the current when the DCCB recloses on the permanent fault. The secondary active current limiting effect is better than the first and the DCCB breaking electric stress is lower than the first. First of all, the topology and principle of the SAFCL are introduced. The main electromagnet parameters are then analyzed. The performance of different FCLs are simulated comparatively to verify the superiority of the SAFCL. Final, the experiment is carried out, the comparison with simulations verifies the feasibility of the SAFCL. [ABSTRACT FROM AUTHOR]

The traditional saturated core type fault current limiters (TFCLs) cause large energy absorption and high overvoltage in direct current circuit breakers (DCCBs). Energy absorbing FCLs (AFCLs) cause coils to bear the fault current for a long period and the fault energy absorption is slow. In order to solve the problems of TFCLs and AFCLs, a novel fast energy storage dc FCL (EFCL) topology is proposed in this article. The EFCL not only reduces the overvoltage and energy absorption of DCCBs but also quickly stores energy. First, the working principle and topology of the EFCL are proposed. The design requirements of the main electrical and core size parameters are then analyzed. Then, the key electrical parameters are optimized by electromagnetic circuit simulations. The economy is analyzed. Finally, the whole process simulation and FCL comparison simulation are carried out. The feasibility of the EFCL is verified by the comparison of simulation with experiment. [ABSTRACT FROM AUTHOR]

With the development of power systems, the power flow problem of transmission line is becoming more and more prominent. This paper presents a power flow regulation method based on phase shifting transformer (PST). Firstly, the working principle and performance of PST are analyzed. Then, the simulation model of BPA multi node system is established. PST access reduces the line imbalance to less than 8%. On this basis, considering the influence of saturation effect and leakage reactance, a PST suitable for 220 kV power grid is designed. Three different working conditions are simulated by PSCAD software. Under normal working conditions and N-1 conditions, PST can increase the transmission limit of the ring network section by more than 20%. When a short-circuit fault occurs, PST can also suppress the fault current. For 220 kV practical projects, unified power flow controller (UPFC) has faster response speed and stronger performance, but PST is more economical and reliable, and the equipment cost is 49.86% lower than that of UPFC. The power flow regulation method based on PST has good steady-state effect. It can improve the utilization efficiency of power grid assets and optimize the power flow distribution in a short time and at low cost. [ABSTRACT FROM AUTHOR]

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]

A fault current limiter is an effective mean of limiting fault currents. The simultaneous use of three single-phase current limiters requires significant amounts of ferromagnetic material and space. This article proposes a three-phase saturated-core fault current limiter (T-SCFCL) that employs a common yoke and a permanent magnet to mitigate the restrictions of material and space. T-SCFCL delivers good performance for single-phase, two-phase, and three-phase faults. In this configuration, flux flowing through the permanent magnets is generated by a three-phase unbalanced current, thereby reducing the loss in eddy current and improving stability while significantly reducing the volume of the core. An algorithm is provided for use in the design of the FCL structure. A simulation was conducted based on the finite element method and a prototype manufactured and tested to verify effectiveness. The results prove that the proposed method is efficient. [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]

A novel multi-function saturated-core fault current limiter (MFCL) with two operating modes is proposed in this paper. MFCL can achieve fault current limitation and power flow management by switching operating mode: current-limiting mode and power-flow-controlling mode, which realizes technology convergence. The MFCL consists of an iron core with rotatable magnetic valve, ac coils, dc coils, and a fault-limiting reactor. The operating principle of the MFCL and the design of the rotatable magnetic valve are analyzed in this paper. The finite-element analysis (FEA) model based on Maxwell is used to analyze the MFCL. Simulation results depict that the MFCL can limit fault current effectively and provide variable impedance for power flow controlling. [ABSTRACT FROM AUTHOR]

A novel direct current system fault current limiter (DCSFCL) based on the principle of nonlinear magnetization was proposed to limit fast rising fault current of the dc system. Different materials were also tested to find the iron core material. However, the existing material is not able to obtain both two necessary indexes, namely, a large saturation point and fast demagnetization speed. Hence, the performance is not satisfactory using a single material. In order to obtain the best performance for the DCSFCL, mixed materials were applied to combine the advantages of different soft magnetic materials. Furthermore, magnetic valves were also added to the original DCSFCL topology, which is an effective method to optimize the clipping performance and reduce the usage of materials. The 2-D models were built and finite-element analyses were carried out to verify these assumptions. Compared with a traditional smoothing reactor, the proposed new model not only limits the fault current by 55.4%, but also reduces the usage of both magnetic material and permanent magnets by over 20%. [ABSTRACT FROM AUTHOR]

The saturated-core fault current limiter (SFCL) is an effective device for limiting fault current. This paper proposes and analyzes a novel bridge-type SFCL (BSFCL) that uses a permanent magnet (PM) to reduce dc bias while improving the stability of the PM. The bridge structure in the BSFCL consists of four coils and a fault-limiting reactor which is used to limit fault current. The ac and the dc share coils to help reduce energy loss. The iron core uses air-gap branches to offer paths for ac flux, which reduces eddy current in the PMs and enhances their stability. The operating principle and characteristics of the BSFCL were analyzed using the electromagnetic coupling method. To investigate the effects of parameters on the performance of the BSFCL, various finite-element analysis simulations were performed by Maxwell. Experimental results of a 220 V prototype verify the effectiveness of the BSFCL. [ABSTRACT FROM AUTHOR]

The permanent-magnet-biasing saturated core fault current limiter (PMFCL) is one of the most promising devices to limit the fault current. To improve the biasing ability of permanent-magnets (PMs) and reduce the cost of PMFCL, this paper proposes a novel compact permanent-magnet-biased fault current limiter (CPMFCL). The three-limb structure can reduce the size and cost; the optimal small-section structure can improve the biasing ability of PMs and reduce the usage amount of PMs. First, the principle, equivalent magnetic circuit, and small-section optimized structure are introduced. To validate the principle and performance of CPMFCL, various finite element analysis simulation and optimization study are performed in Maxwell-3D. A 220 V/10 A CPMFCL prototype is designed and tested. The simulation and experimental results demonstrate that, compared with traditional PMFCLs, the CPMFCL has the advantages of smaller size, better biasing capacity of PMs, lower possibility of demagnetization, and excellent fault clipping performance. [ABSTRACT FROM AUTHOR]

The application of fault current limiter is an effective method to limit fault current. The saturated-core fault current limiter (SFCL) is one of the promising devices. However, its commercialization is limited by the high demands for the ferromagnetic material and the dc source generating magneto motive force. This paper proposes a novel three-phase compact SFCL (CSFCL) in which a common core and a permanent magnet are used to solve the mentioned challenges. The common core can significantly reduce the amount of required ferromagnetic material. The basic operating principle of CSFCL is introduced based on the analysis of the CSFCL’s magnetic circuit and equivalent electrical circuit. Finite-element analysis (FEA) simulations were performed by ANSOFT to validate the effectiveness of the CSFCL’s fault clipping performance. [ABSTRACT FROM AUTHOR]

The saturated core fault current limiter (SFCL) is one of the most effective methods for limiting fault current. A permanent magnet (PM)-biased SFCL (PFCL) can reduce dc bias current and additional energy consumption. However, the thermal stability of NdFeB PMs in PFCL poses a major challenge. This paper proposes a novel hybrid-type SFCL (HSFCL) topology that can reduce this risk. In the HSFCL, a hybrid PM/dc coil is designed to saturate the core, and a fault-limiting reactor is used to guarantee fault-clipping performance. The new structure provides air-gap branches for the time-varying magnetic field produced by alternating current, which reduces the eddy current in the PMs and enhances their stability. Electromagnetic coupling is used to analyze the operating principles and characteristics of HSFCL. Finite-element analysis simulations were performed using Maxwell and compared with verification experiments, proving that HSFCL is efficient in fault clipping and PM reliability enhancement. [ABSTRACT FROM AUTHOR]

A saturated core fault current limiter (SCFCL) is a promising device for limiting the fault currents effectively, and improving the safety and reliability of power systems. Due to the core structure and the coupling effect between the ac and dc windings, traditional SCFCLs suffer the drawbacks of insufficient clipping performance and large size. Moreover, theoretical analysis of fault clipping performance has received little attention. Therefore, this paper proposes a novel bridge-type SCFCL (BSFCL). Compared with the traditional type, the BSFCL effectively reduces size and cost by using a bridge-type structure. In addition, the proposed additional limiting inductor improves the fault clipping performance of SCFCL. This paper first presents the principle and characteristics of BSFCL. Then, a theoretical analysis of clipping performance and parameter design method of BSFCL are presented in detail. Finally, the principle and performance of BSFCL are validated through electromagnetic simulation and experiments. The simulation and experimental results demonstrate the effectiveness of the theoretical analysis and the structure. The influence of different BSFCL parameters on fault clipping performance is also discussed. [ABSTRACT FROM PUBLISHER]

The fault current limiter (FCL) is one of the most useful measures for limiting fault currents in power systems. This paper introduces a new structure for a parallel-type permanent magnet (PM)-biased saturation-based FCL (PPFCL). The PPFCL consists of two magnetic devices connected in parallel and in magnetic counter opposite to each other. The operating principle and the core inductances in different states were analyzed using an electromagnetic equivalent circuit. In addition, a 220 V/10 A experimental prototype was designed and tested in a simple system and compared with Maxwell-3-D simulation and analytical methods. Finally, a 10 kV case-study model was created and compared with a series-type FCL, which verified the effectiveness of the limiter in high-voltage, large-capacity application. Experimental and simulation results have demonstrated that the PPFCL exhibits fast response and low impedance during normal operations, as well as high bias capability and low possibility of demagnetization of the PM during fault conditions. [ABSTRACT FROM AUTHOR]