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Saturated core fault current limiters are effective means to limit short-circuit currents in high voltage power systems. To solve its problems of a low rate of utilization and large loss, this study proposes a multifunctional saturated-core fault current limiter (MFFCL) with a hybrid excitation system. The MFFCL can limit the short-circuit current and control power flow to reduce losses. The composition and topological structure of the MFFCL are provided, an equivalent electromagnetic circuit model of the MFFCL is then established, and its working mechanisms of limiting current and regulating power flow are analyzed. Following this, a finite-element simulation model of the MFFCL is built to investigate its electromagnetic characteristics and verify its performance in terms of limiting current. The power flow regulation function of the MFFCL was verified through the field-circuit coupling method. Finally, a laboratory-scale prototype of the MFFCL and a test platform was designed to test it. The results of the experiments verified the correctness and feasibility of the proposed structure. It can adequately control power flow in its normal state, and can limit the short-circuit current to 60% of the original in case of a fault. [ABSTRACT FROM AUTHOR]

Orthogonal controllable reactors (OCRs) have the advantages of low distortion and linear inductance regulation. However, traditional OCRs suffer from two vital problems, namely, their small inductance regulation range and large space occupation. To solve these issues, a new compact OCR is proposed in this study. First, the magnetic circuit of the reactor is established through theoretical analysis. Second, the simulation model is established and the inductance regulation characteristics of the reactor are obtained. Third, the key parameters are optimized for better performance based on Pareto optimality and a genetic algorithm. Finally, based on the optimized parameters, a new prototype of the OCR is developed and experimental work is carried out to verify the analysis. The results show that, compared with the traditional model, with the same material consumption, the space occupation of the new topology is reduced by 53.7% and the inductance regulation range is increased by 69%. Experimental results also show that increasing the area of the orthogonal region can significantly increase the inductance regulation range of the reactor. Based on the OCR, the filter with a variable resonance frequency can be formed, which is of significant application value in situations where the harmonic frequency is constantly changing. [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]

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 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]

Eddy-current loss of NdFeB permanent magnets (PMs) is widely analyzed in PM motors. This paper proposes a coupled 2-D transient finite-element analysis (FEA) of the saturated core fault current limiter (SCFCL) and 3-D analytical model of PMs to evaluate eddy-current loss in SCFCL. The comparison between the result from coupled method and that from 3-D FEA verifies the applicability of the coupled method in analyzing eddy current loss of PMs in SCFCL. The 3-D analytical model of PM is applied to analyze the effect of segmentation on the reduction of PM’s eddy-current loss. And the results show that segmentation along width has a better performance, which is also verified by 3-D FEA. [ABSTRACT FROM AUTHOR]

In this paper, a novel compact high-voltage (HV) test system based on a magnetically controlled resonant transformer (MCRT) is proposed. This system is used to perform a power-frequency HV on-site voltage withstanding test. First, the basic principle of the MCRT is introduced. Next, a Fourier analysis based on the equivalent magnetic and electrical circuits of the MCRT is described. This analysis provides a design reference for the basic MCRT parameters. In addition, a finite-element model was constructed to verify the MCRT design. Finally, an MCRT prototype was designed to verify the effectiveness of the test system. Compared with the traditional HV test systems, the proposed test system in this paper has the advantages of compact structure, stable secondary voltage, and wide reactance adjustment range. [ABSTRACT FROM AUTHOR]

To reduce the requirement of dc-coil-generated magnetomotive force, this paper analyzes the method of using permanent magnets (PMs) to saturate the core. In this paper, a novel bridge-type hybrid saturated-core fault current limiter (BHFCL) is proposed to investigate the influence of PM. For the BHFCL, a bridge structure is designed to guarantee the fault clipping performance, with a fault limiting reactor. In addition, the compact structure of magnetic device and the shared coil of alternating current and dc could reduce cost and losses. To compare the influence of PMs on the performance of BHFCL and to validate the effectiveness of the proposed BHFCL, various FEA simulation models in a simple system are carried out by ANSOFT. The simulation results demonstrate that the BHFCL could achieve considerable energy consumption reduction with little effect on the normal condition voltage drop as well as the fault clipping ability. The BHFCL is efficient in fault clipping, and the performance is shown to depend mainly on the value of the reactor included in the bridge. [ABSTRACT FROM AUTHOR]