Short-circuit Fault Conditions Research Articles

Fault Detection and Isolation in Simulated Batch Operation of Fine Motion Control Rod Drives

Control rods and elements manage the power distribution in nuclear reactors through the motion of banks of rods distributed throughout the core. These positional changes are achieved through the actuation of fine motion control rod drive (FMCRD) mechanisms. In the BWRX-300 design by GE-Hitachi, this mechanism is electrically driven by a servomotor that allows for high-precision control of power outputs. Under operational transients, such as load-following, accurate and precise operation of these servomotors is necessary over long periods of time, so they are key maintenance targets to maintain availability and operational flexibility. Swiftly and precisely identifying faults in the drive mechanisms will support predictive maintenance and reduced costs. This paper used three different types of simulated faults to test the fault detectability of principal component analysis (PCA) when considering the simulated operations of banks of control rods and their associated servomotors. These faults were stator short-circuit faults, ball screw jam faults, and ball screw wear faults. Torque and position were monitored in the simulation. The position signal was insufficient to detect mechanical faults. Torque signals for each servomotor in the bank of rods undergoing multiple position demand changes were projected to a reduced dimensional space via PCA. Q and T2 statistics were employed for anomaly detection. Using this approach, all faults were detected, and the anomalies were isolated to the faulty FMCRD mechanism.

A novel estimation methodology for multi-resonance equivalent inductance of transformer winding for inter-turn short-circuit fault detection

A novel, indirect measurement technique for estimating equivalent inductance associated with multi-resonance behavior of an isolated transformer winding is reported for both healthy and inter-turn short-circuit fault-condition. For healthy winding, the authors proposed measuring two unique admittance magnitude responses of the winding followed by utilizing their natural frequencies for estimating the said inductance. Here, the one response is for line-end excitation with neutral-end grounded and the other one is for two equal and opposite polarity excitations from two ends of the winding. For inter-turn shorting, driving-point admittance magnitude response with neutral-end open is also utilized. This inductance seems to be one important parameter for verifying the design constraint mainly for impulse behavior as well as for identifying inter-turn shorting of the winding. The proposed method was also verified by experimental measurements on two actual transformer windings; one of which incorporated an iron core within it. All pertinent analytical derivations and the associated results are also included in the paper.

Transient Synchronous Stability Analysis of Grid-Forming Photovoltaic Grid-Connected Inverters during Asymmetrical Grid Faults

Compared with the traditional grid-following photovoltaic grid-connected converter (GFL-PGC), the grid-forming photovoltaic grid-connected converter (GFM-PGC) can provide voltage and frequency support for power systems, which can effectively enhance the stability of power electronic power systems. Consequently, GFM-PGCs have attracted great attention in recent years. When an asymmetrical short-circuit fault occurs in the power grid, GFM-PGC systems may experience transient instability, which has been less studied so far. In this paper, a GFM-PGC system is investigated under asymmetrical short-circuit fault conditions. A novel Q-V droop control structure is proposed by improving the traditional droop control. The proposed control structure enables the system to accurately control the positive- and negative-sequence reactive current without switching the control strategy during the low-voltage ride-through (LVRT) period so that it can meet the requirements of the renewable energy grid code. In addition, a dual-loop control structure model of positive- and negative-sequence voltage and current is established for the GFM-PGC system under asymmetrical short-circuit fault conditions. Based on the symmetrical component method, the composite sequence network of the system is obtained under asymmetrical short-circuit fault conditions, and positive- and negative-sequence power-angle characteristic curves are analyzed. The influence law of system parameters on the transient synchronous stability of positive- and negative-sequence systems is quantitatively analyzed through the equal area criterion. Finally, the correctness of the theoretical analysis is verified by simulation and hardware-in-the-loop experiments.

Incipient short circuit fault impact on service continuity of an electric vehicle propelled by dual induction motors structure

The short circuit is among one of the most dangerous electrical faults in induction motor, which leads to serious implications on the motor operation and its performances. The present paper deals with the influence of the stator short circuit fault in its early stage in terms of performances and service continuity of an electric vehicle (EV) using dual induction motor’s structure piloted by Backstepping control. An equivalent induction motor model with turn-to-turn fault on one stator phase, without already assuming the temperature effect through an intrinsic model, is investigated and thereafter its impacts on electric vehicle performance using simulation tests are presented and discussed.

A Modular DC-DC Converter as a Hybrid Interlink Between Monopolar VSC and Bipolar LCC-Based HVDC Links and Fault Management

High voltage dc (HVdc) transmission has gradually gained its popularity in long distance transmission of power. The possibility of multi-terminal HVdc network has further projected HVDC as a potential mode of power trading across geographical boundaries. The emergence of modular multilevel converter (MMC)-based dc-dc converters has led to the interconnection of HVdc networks across voltage levels, converter technologies and line topologies. This paper puts forward a topological modification in an existing MMC-based dc-dc converter topology, acting as a hybrid interconnect between different converter technologies, for interface of an asymmetric monopolar voltage source converter (VSC) and a bipolar line commutated converter (LCC)-based HVdc links. The proposed operation of the topology is validated experimentally in a down-scaled laboratory prototype. The proposed topology is further investigated for short-circuit fault conditions in any of the poles of HVdc bus and appropriate fault mitigation strategies are adopted for short-cicuit fault in both LCC and VSC bus. The fault mitigation strategies are validated by simulation in Matlab/Simulink platform.

Short-Circuit Performance Analysis of a Distribution Transformer Using Coupled Field-Circuit Approach

The inability of power transformers to resist a short-circuit (SC) fault significantly impacts the safety of power systems. During SC faults, the leakage field undergoes significant distortion, resulting in large SC electromagnetic forces (EFs), which results in critical mechanical stresses. The finite element method (FEM) might be one of the best non-destructive numerical methods that enable designers to assess the transformer SC performance. Using the FEM, most SC performance analysis studies assume either the three-phase (LLL) or the single-phase-to-ground (LG) SC fault. Moreover, the existing studies use an excitation method that provides a high error rate due to the sensitivity of transient solvers. Furthermore, no considerable attention has been given to analyzing the influence of grounding the wye-connected windings on the SC performance. In this work, a non-linear-transient field-circuit coupled 3-D finite element model is created to analyze the SC performance of a delta-wye connected distribution transformer under various SC fault conditions. Results show that grounding the secondary windings significantly impacts the performance when a LG fault is applied. Except for the LG fault with wye configuration of the secondary windings, the windings SC current and EFs decay/rise over time with an exponential trend till reaching steady state.

Active Power Backflow Suppression Strategy of Cascaded PV Solid-State Transformer Under Interphase Short-Circuit Fault Condition

Currently, the grid-tied guidelines all require large and medium-sized photovoltaic (PV) power stations to stay connected to the grid during low-voltage ride through (LVRT). However, three-phase cascaded PV solid-state transformer (SST) has the inherent active power backflow problem during asymmetric voltage sags, causing that H-bridge dc-bus voltages are out of control and that the converter will be disconnected from the grid because of overvoltage fault. The existing control strategy is capable of avoiding active power backflow in theory by injecting appropriate zero-sequence voltage, but the overmodulation range is larger during interphase short-circuit fault, weakening active power backflow suppression effect. For this issue, this article proposes a combined control method of positive–negative-sequence maximum–minimum harmonic zero-sequence voltage injection strategy and adaptive zero-sequence voltage compensation strategy, which can shrink effectively active power backflow range of three-phase cascaded PV SST, increasing its adaptability to different output powers and different grid drop depths, and then improving LVRT capability of the PV power generation system. Finally, a low-voltage and low-power experimental prototype is made to verify the effectiveness and feasibility of the proposed control strategy.

Frequency Response Analysis for Three-Phase Star and Delta Induction Motors: Pattern Recognition and Fault Analysis Using Statistical Indicators

This paper presents a new investigation to detect various faults within the three-phase star and delta induction motors (IMs) using a frequency response analysis (FRA). In this regard, experimental measurements using FRA are performed on three IMs of ratings 1 HP, 3 HP and 5.5 HP in normal conditions, short-circuit fault (SC) and open-circuit fault (OC) conditions. The SC and OC faults are applied artificially between the turns (Turn-to-Turn), between the coils (Coil-to-Coil) and between the phases (Phase-to-Phase). The obtained measurements show that the star and delta IMs result in dissimilar FRA signatures for the normal and faulty windings. Various statistical indicators are used to quantify the deviations between the normal and faulty FRA signatures. The calculation is performed in three frequency ranges: low, middle and high ones, as the winding parameters including resistive, inductive and capacitive components dominate the frequency characteristics at different frequency ranges. Consequently, it is proposed that the boundaries for the used indicators facilitate fault identification and quantification.

Fault diagnosis in a five-level multilevel inverter using an artificial neural network approach

Introduction. Cascaded H-bridge multilevel inverters (CHB-MLI) are becoming increasingly used in applications such as distribution systems, electrical traction systems, high voltage direct conversion systems, and many others. Despite the fact that multilevel inverters contain a large number of control switches, detecting a malfunction takes a significant amount of time. In the fault switch configurations diode included for freewheeling operation during open-fault condition. During short circuit fault conditions are carried out by the fuse, which can reveal the freewheeling current direction. The fault category can be identified independently and also failure of power switches harmed by the functioning and reliability of CHB-MLI. This paper investigates the effects and performance of open and short switching faults of multilevel inverters. Output voltage characteristics of 5 level MLI are frequently determined from distinctive switch faults with modulation index value of 0.85 is used during simulation analysis. In the simulation experiment for the modulation index value of 0.85, one second open and short circuit faults are created for the place of faulty switch. Fault is identified automatically by means of artificial neural network (ANN) technique using sinusoidal pulse width modulation based on distorted total harmonic distortion (THD) and managed by its own. The novelty of the proposed work consists of a fast Fourier transform (FFT) and ANN to identify faulty switch. Purpose. The proposed architecture is to identify faulty switch during open and short failures, which has to be reduced THD and make the system in reliable operation. Methods. The proposed topology is to be design and evaluate using MATLAB/Simulink platform. Results. Using the FFT and ANN approaches, the normal and faulty conditions of the MLI are explored, and the faulty switch is detected based on voltage changing patterns in the output. Practical value. The proposed topology has been very supportive for implementing non-conventional energy sources based multilevel inverter, which is connected to large demand in grid.

High-Frequency Square-Wave Signal Injection Based Sensorless Fault Tolerant Control for Aerospace FTPMSM System in Fault Condition

To enhance position detection reliability, this article proposes a new high-frequency square-wave signal injection (HFSWSI) based sensorless control for aerospace fault tolerant permanent magnet synchronous motor (FTPMSM) drives, which can be configured as the nonsimilar redundancy for a physical sensor. The novel sensorless control scheme with HFSWSI in two nonfault windings is first proposed for the FTPMSM system under each phase current independent control frame, which is free of the coordinate transformation. The HFSWSI-based position detection is then proposed for rotor position estimation via HF response currents even in phase open-circuit fault (OCF) and short-circuit fault (SCF) conditions. To enhance the dynamic performance, a novel dual-output filter is proposed for the fundamental and HF response current component extractions with almost no phase lag. To guarantee the fault tolerant performance, the optimal torque control (OTC) is utilized to ensure that the FTPMSM system generates the ripple-free torque even in fault condition. The resulting sensorless FTPMSM system has outstanding low-speed sensorless control performance both in normal and fault conditions, which is also experimentally validated on a six-phase FTPMSM platform.

Simulation research on large capacity power supply technology suitable for distribution transformer short-circuit withstand capability test

The existing transformer short-circuit test equipment and technology have several limitations. The purpose of short-circuit test is to simulate the test of high-voltage equipment under the short-circuit fault condition of the power system, usually, a large capacity test such as transformer burst short-circuit test, circuit breaker dynamic heat stability test, to verify the reliability and stability of related equipment under extreme working conditions. At present, the large capacity test generally uses methods of power grid dedicated line power supply and short-circuit testing alternator group. However, these two methods have difficulties in construction approval, high investment costs, complex site requirements, a large impact on the power grid, and low control accuracy. Theoretical studies on equivalent simulation verification method of short-circuit withstand capability test of distribution transformer demonstrated the feasibility of using modern power electronics and advanced energy storage technology to replace conventional power grid dedicated line power supply, short-circuit testing alternator and other short-circuit impact test equipment. It could complete the transformer short-circuit impact test specified by (IEC60076-5) with lower cost and higher efficiency, verify the short-circuit impact resistance of the transformer, and improve the test capacity.

Modality analysis and algorithm design of stator short-circuit fault set for large compressed air energy storage generators

Using salt caverns and caves to build compressed air energy storage power stations is an important development direction in the field of large-scale energy storage. With the continuous maturity of technology, compressed air energy storage generators have gradually developed into large-scale units with a single-unit capacity of 300 MW. Due to the increase of single-unit capacity, the internal short-circuit fault of the stator will cause very serious losses. In addition, the compressed air energy storage generator has complex operating conditions and is more prone to various internal short-circuit faults. In order to effectively ensure its safe and reliable operation, it is particularly necessary to study the effective main protection configuration scheme. The optimal design of the main protection configuration scheme is based on the analysis of the possible internal short-circuit faults of the generator. At present, the stator windings of large-scale compressed air energy storage generators generally adopt double-layer wave winding or double-layer tap winding structures. For these two winding structures, this paper analyzes in detail the characteristics of all fault modalities that may occur inside the large-capacity compressed air energy storage generator and designs a general algorithm that can form their respective fault sets. Finally, the application of the algorithm in the analysis of the stator fault modality in a compressed air energy storage power station is introduced.

Resistive SFCL Integrated Ultrafast DC Hybrid Circuit Breaker for Subsea HVDC Transmission Systems

High voltage direct current (HVdc) power transmission systems do not encounter any natural zero crossing unlike the ac systems, and hence, the dc circuit breakers employed should be fast-acting and reliable to ensure safe operation. Circuit breakers (CBs) that have fast response time with lower energy loss dissipation are required for subsea HVdc transmission systems. This article investigates the performance of various CB topologies, including ultrafast coupled inductor hybrid CB (CIHCB) topology without and with the integration of resistive-type superconducting fault current limiter (R-SFCL) for a 100-kV, 100-MW HVdc transmission systems. It is found that the addition of R-SFCL with 1.7-ms response time decreases the peak current through the breaker and, hence, the power dissipated in the CB during short-circuit fault conditions. Thus, the rating of CB can be significantly decreased with the proposed topology. Furthermore, a comparison of power loss in CIHCB with the existing topologies, such as mechanical CB, resonant CB, and HVdc-hybrid CB, are also presented in this article.

Multi-Domain Modeling and Simulation of High-Temperature Superconducting Transmission Lines Under Short-Circuit Fault Conditions

Emission reduction in transportation requires advancements in aviation technologies enabling fully electrified propulsion, among which the use of superconducting technologies can provide untapped benefits given their low weight and minimal losses for high-power transmission. However, to enable their use in aircraft electrical power systems, additional considerations for electrical and thermal performance during faults is required in order to meet stringent aircraft safety requirements. In this work, a cryogenically cooled electric aircraft power system is studied under short-circuit conditions for different cooling media. This system consists of a fuel cell, high-temperature superconducting (HTS) transmission line, inverter, and motor, where each of their fault models have been explored. A trade-off study of the impedance of the fuel cell is conducted to identify the values at which the superconducting cable remains thermally stable after a short-circuit fault, as it is crucial that the cable does not experience a thermal runaway.

A Fault-Tolerant Power Converter With Multi-Switch Fault Diagnosis and Repair Capability for 4-Phase 8/6 SRM Drives

In this article, a modular fault-tolerant power converter for 8/6 four-phase switched reluctance motor (SRM) drives is presented. The proposed converter can work for both open-circuit (OC) and short-circuit (SC) fault conditions in the power semiconductor switches. A semiconductor switch module and a relay circuit are used for achieving the fault tolerance feature. The proposed converter is modular and provides independent fault-tolerant control for all phases. It also uses a minimum number of switches when compared with other fault-tolerant converter topologies. The proposed converter is tested for a fault in single as well as multiple phases using MATLAB/Simulink software and is validated experimentally on a 0.6 hp 8/6 SRM using an FPGA-based hardware setup developed in the laboratory. Detailed results are presented and compared with existing fault-tolerant converter topologies. A fault repair time of 2 ms has been achieved for both open and SC faults.

Electromagnetic Field Analysis and Optimization Method of High-Temperature Superconducting Transformer under the Influence of Abnormal Voltage

High-temperature superconducting transformers are an important research topic of superconducting technology in power applications, and electromagnetic field analysis and optimization are the basis for the design and application of high-temperature superconducting transformers. The electromagnetic field analysis of high-temperature superconducting transformers should consider the superconducting properties of the materials, that is, the properties of critical current and magnetic field. This paper aims to study the electromagnetic field analysis and optimization method of high-temperature superconducting transformer under the influence of abnormal voltage. Due to the energy loss of high-temperature superconducting transformers, in order to study the economy and reliability of high-temperature superconducting transformers, in this paper, the core loss, winding AC loss, and coil power consumption of high-temperature superconducting transformers are analyzed under normal operation and short-circuit fault conditions, respectively. The power and stress on the windings are analyzed. In order to take into account the current-carrying capacity, short-circuit loss, and short-circuit electromotive force of superconducting windings in normal operation, a concentrically placed double-cake coil structure is selected in this paper, and according to different optimization objectives, a global optimization method is used to evaluate the structure of the coil. The structural parameters of the high-temperature superconducting transformer are optimized, including the structural parameters of the magnetic conducting ring. It is found that that abnormal voltage will affect the electromagnetic field of high-temperature superconducting transformers, including winding circulating current, leakage magnetic field, and current distribution.

Output power smoothing of wind power plants using unified inter-phase power controller equipped with super-capacitor

Due to the growing concerns regarding environmental and economic issues in power systems, nowadays the application of renewable energy sources (RES), especially wind energy has been increased. However, the increasing penetration of wind power plants (WPPs) into the grid has raised numerous challenges including output power fluctuations as well as the significant role these sources play in low-voltage ride-through (LVRT) in case of short circuit fault conditions. Energy storage systems (ESSs) are commonly employed to enhance WPP output power smoothing. On the other side, flexible AC transmission systems (FACTS) can be utilized to enhance dynamic transients of the WPPs under short circuit contingencies. This paper presents the utilization of unified inter-phase power controller (UIPC) and the super-capacitor to fulfill the aforementioned challenges in connection of WPPs to the grid. To achieve this, a novel power control scheme is proposed to compensate for output power variations. The WPP model studied here is of doubly-fed induction generator (DFIG) type wind turbine. Simulations and comparisons are performed in the MATLAB/Simulink® environment to demonstrate the effectiveness of the proposed scheme in smoothening WPP output power as well as enhancing their LVRT capability.

Simulation of reactance of built-in reactor in power transformer with field-circuit coupling method

Using low-voltage winding series built-in reactor in power transformer was one of the effective methods to improve the impedance of transformer. It was useful and benefit for the impedance selection and design of power transformer by researching on the simulation calculation of leakage reactance under the normal operation and short-circuit fault condition of transformer with built-in reactor. In this paper, a finite element model was established based on the structural parameters of an actual power transformer with built-in reactor. The leakage magnetic field and leakage inductance parameters of the teansformer with built-in reactor under the normal operation and short-circuit condition were calculated respectively using “Magnetic-Circuit” coupling method, and the changes of leakage reactance were compared.The results show that, when the transformer was short-circuit, the short circuit current will passing through built-in reactor, which would cause the core framesaturated, and the leakage reactance of the built-in reactor would be reduced. The research results shown that the problem of leakage reactance reduction of built-in reactor should be considered in the design of short-circuit resistance of transformer, which was of great significance to guide the short-circuit design of power transformer.

Investigation analysis of open circuit and short circuit fault on cascaded H-bridged multilevel inverter using artificial neural network approach

Cascaded H-bridge multilevel inverters are becoming increasingly used in applications such as distribution systems, electrical traction systems, high voltage direct conversion systems, and many others. Despite the fact that multilevel inverters contain a large number of control switches, detecting a malfunction takes a significant amount of time. In the fault switch configurations diode included for freewheeling operation during open-fault condition. During short circuit fault conditions are carried out by the fuse, which can reveal the freewheeling current direction. The fault category can be identified independently and also failure of power switches harmed by the functioning and reliability of cascaded H-bridge multilevel inverters. This paper investigates the effects and performance of open and short switching faults of multilevel inverters. Output voltage characteristics of five level MLI are frequently determined from distinctive switch faults with modulation index value of 0.85 is used during simulation analysis. In the simulation study, with the modulation index value of 0.85, one second open and short circuit faults are generated for the location of the defective switch. Fault is identified automatically by means of artificial neural network technique using sinusoidal pulse width modulation based on distorted total harmonic distortion and managed by its own. The proposed topology is to be design and evaluate using MATLAB/Simulink platform.

천연가스 정압소에 설치한 터보팽창형 유도발전기의 계통 연계 시 과도특성 해석

A new type of power generation facility with TEG that utilizes waste pressure energy during the decompression process of liquid natural gas, and the problem of instantaneous voltage sag should be reviewed in advance for grid-connected operation mode. This study implemented an EMTP/RV simulation model and conducted a time-domain simulation for verifying transient characteristics of turbo expander driven a squirrel cage induction generator in a gas governor station. The simulation results for the case studies including parallel operation condition, reactive power compensation, and three-phase short-circuit fault condition were reviewed based on the grid code and finally contributed to propose the conceptual method for grid-connected operation of TEG.