Saturable Reactor Research Articles

A Case Study of Transient and Dynamic Performance of Saturated Core Reactor Static Var Compensator

This paper presents results related to transient, dynamic and steady state response of a Saturated Core Reactor Static VAr Compensator (SCR-SVC) at regulating a real radial 230 kV transmission line supplying a low density and highly distributed load in a developing area of Brazil. The studies are carried out using a time domain computational simulator in which a comprehensive model for a given twin-triple saturated reactor compensator model was implemented to cope with the receiving end load requirements for voltage regulation. Investigations are then performed to highlight the overall system and reactive compensator behavior at the occurrence of the reactor switch on conditions, final load relief and harmonic distortions.

A Comparative Performance Analysis between Saturated Core Voltage Regulators Using Silicon Steel and Amorphous Alloys

The focus of the paper presented herein is directedtowards the investigative study of the operational performance of saturated reactors intended for voltage regulation, which consist of magnetic silicon steel cores and amorphous alloys. In order to reach the defined goal, two similar devices in terms of voltage operation and reactive power compensation are employed, both embodied with a twin-tripler or 12 pulse configuration. Both devices are modelled and implemented onto the ATP simulator to carry out comparative studies. Through the use of a classicdistribution feeder, performance studies concerning sudden voltage variations are considered, which are focused on above all: evaluation of active losses, non-saturated and saturated reactive power, waveforms for inductive current and voltage with their harmonic spectra. The results obtained from the studies allows for a prompt correlation between the characteristics associated with the functionality of the device, highlighting the advantages offered by the use of one or other magnetic material.

Case-Study of an HTS Saturable Core Reactor for Power Flow Control in a Transmission Grid

Case-Study of an HTS Saturable Core Reactor for Power Flow Control in a Transmission Grid

Calculation of core hysteresis loss resistance for Buntenbach’s analogy hysteresis model

The value for core hysteresis loss (CHL) resistance in Buntenbach’s analogy hysteresis model does not consider the impact of frequency variations. In order to address this issue, this paper proposes a calculation expression for CHL resistance that takes into account the influence of frequency variation through a variable coefficient. The paper analyzes changes in CHL resistance values at different frequencies using hysteresis loss characteristics and circuit theory. To validate the proposed calculation method for CHL resistance, Buntenbach’s analogy hysteresis model is applied to model the Epstein frame and magnetically saturated controllable reactor. The comparative results reveal that the proposed calculation expression for CHL resistance is effective.

A Diagnostic Method for the Saturable Reactor Core Looseness Degree of Thyristor Converter Valves

During the long-term operation of thyristor converter valves, the saturable reactor vibration (mainly caused by magnetostriction) will lead to core looseness faults. In order to accurately evaluate the fault degradation degree, this paper proposes a vibration signal recognition model for iron core looseness based on synchrosqueezed wavelet transforms and a convolutional neural network. Firstly, vibration experiments are conducted on saturable reactors to obtain signals under different core looseness degrees. Then, the spectrogram features of vibration signals are extracted using synchrosqueezed wavelet transform. Finally, based on the high-dimensional learning ability of convolutional neural networks, the fault characteristics of the spectrogram are mined to accurately identify the core looseness degree. The research results indicate that the model in the paper has higher recognition accuracy than some other methods, which provides convenience for the monitoring and maintenance of saturable reactors.

Current-voltage characteristics of single-stage semiconductor magnetic pulse generators with a distinctive structure of the conversion link in the input circuit

Introduction. The main feature of the semiconductor magnetic pulse generators (SMPGs) is a slow accumulation of energy in the primary capacitor and its rapid introduction into the load by using a series of sequentially connected magnetic compression stages. Initially, these devices were mainly used for pumping gas lasers, but over the last decade SMPGs have been increasingly used in electric discharge technologies for water purification and air ionization to remove toxic impurities. At the same time, along with the practice of using these devices, development has also been achieved in the principles of their design and methods of mathematical modeling. Problem. The main drawback of the existing theory of SMPG’s stationary oscillations mode is an adoption of the saturable reactor (SR) model in approximation of the static magnetization curve of its core, as well as unidirectional nature of the energy transfer from the generator to the load. In most publication the exchange processes between the power source and SR are still not covered. Goal. Study of electrical and energy characteristics of low-voltage single-stage SMPG devices with series and parallel conversion stages in the charging circuit. Methodology. To achieve the set goal, this work uses comprehensive approach relayed on technical tools of setting up the experiment, numerical methods for processing measurement results, as well as an analytical method for describing electromagnetic processes in single-stage SMPG circuits. Results. The closed current-voltage characteristics of the SR are obtained, according to which the numerical calculations of the integral magnetic and energy characteristics of the proposed models are carried out. The features of the longitudinal capacitance charging process in a SMPG’s circuit with a parallel conversion stage, which occurs simultaneously in two adjacent circuits, are explained. Analytical expressions to describe the dynamics of magnetic flux density in the SR’s core as a time-depended function are derived. Based on the obtained hysteresis curve of the core, the exchange processes of energy transfer between the power source and the SR are explained. Practical value. The results of the research can be applied in the development of low-voltage SMPG circuits with improved energy-dynamic parameters.

Diagnosis of Loose Core Fault in Saturable Reactor of Thyristor Valve Based on Vibration Signal Time-Frequency Analysis and CNN

The saturable reactor is one of the core components of the thyristor valve, which plays a role in suppressing current changes and balancing voltage distribution. Due to long-term operation under complex working conditions, the vibration of the reactor can cause the core to loosen. To detect faults in time, a fault diagnosis method is proposed for loose cores in saturable reactors of thyristor valves based on time-frequency analysis of vibration signals and convolutional neural networks. The two-dimensional time-frequency spectrum of the vibration signal is obtained using the short-time Fourier transform method. A convolutional neural network model structure is designed to extract time-frequency spectrum features and diagnose different levels of core looseness faults through learning and training. An experiment was carried out to collect core fault information under variable working conditions. The effectiveness of the method proposed in this paper was verified based on experimental data validation. Through comparative experiments, it was found that the proposed method is superior to existing fault diagnosis methods.

Mathematical modeling and simulation of a diolefin saturation reactor used in a naphtha hydrotreating process

Mathematical modeling and simulation of a diolefin saturation reactor used in a naphtha hydrotreating process

An Improved Zero-Voltage and Zero-Current- Switching Phase-Shift Full-Bridge PWM Converter With Low Output Current Ripple

In order to improve the performance of traditional phase-shifted full-bridge converters and reduce the output current ripple, an improved zero voltage and zero current switching phase-shifted full-bridge PWM converter is proposed in this article. By adding a simple auxiliary circuit, the leading-leg switches realize zero voltage switching and the lagging-leg switches realize zero current switching. The primary current is reset during the freewheeling period, so the efficiency of the converter is improved. What is more, the improved converter can effectively reduce the output current ripple. The added auxiliary circuit does not include any lossy components or saturable reactors. The improved phase-shifted full-bridge converter has many advantages, including simple circuit topology, easy implementation of soft switching, high efficiency, and low output current ripple. The operational principle and analysis of the proposed converter are presented in this article. An 800 W experimental prototype is built for experimental verification.

Research on Vibration Data-Driven Fault Diagnosis for Iron Core Looseness of Saturable Reactor in UHVDC Thyristor Valve Based on CVAE-GAN and Multimodal Feature Integrated CNN

The imbalance of data samples and fluctuating operating conditions are the two main challenges faced by vibration data-driven fault diagnosis for the iron core looseness of saturable reactors in UHVDC thyristor valves. This paper proposes a vibration data-driven saturable reactor iron core looseness fault diagnosis strategy named CVG-MFICNN based on CVAE-GAN and MFICNN to overcome the two challenges. This strategy uses a novel 1-D CVAE-GAN model to produce generated samples and expand the training set based on imbalanced training samples. An MFICNN model structure is designed to allow the simultaneous processing of multimodal features such as the SST time-frequency spectrum, time-domain vibration sequence, frequency-domain power spectrum sequence, and time-domain statistics. Using these multimodal features and the MFICNN model, the hidden fault information in vibration data can be effectively mined. An experiment is conducted to collect vibration data of saturable reactors with different faults. Models based on the proposed strategy and other methods are trained and tested using the collected data. The comparison results show that the performance of the proposed CVG-MFICNN approach is significantly superior to that of single-feature CNNs, traditional machine learning methods, and classical image classification CNNs in the application of UHVDC thyristor valve saturable reactor iron core looseness fault diagnosis.

Research on vibration of the reactor for HVDC thyristor protection

As the key equipment to protect the thyristor of HVDC converter valve, the vibration problem of anode saturable reactor (ASR) is very prominent. Its long-term vibration will even cause the failure of the whole converter valve system. From the perspective of multi-physical field coupling, this paper establishes the solid model of ASR, considers the influence of Maxwell electro-magnetic field and magnetostrictive effect, numerically calculates the magnetic field and vibration of iron core, analyzes the contribution of two forces to vibration, and expounds the vibration phenomenon of iron core at different positions. In order to evaluate the effectiveness of the simulation, a single iron core vibration experiment is designed and compared with the single iron core simulation. This study can predict the vibration level of ASR core and provide theoretical basis and calculation method for vibration reduction in ASR design stage.

A Self-Activated Fault Current Limiter for Distribution Network Protection

Rapid protection of modern electric networks using fault current limiters (FCLs) is often delayed and limited by the inherent controller, sensor, and power electronic unit delays. This article proposes a novel self-activated FCL (SAFCL), comprising a dc saturation winding, series ac limiter windings, and ac parallel reactor, which limits the fault current in less than 0.4 ms. Furthermore, the advantage of this SAFCL, when compared to a traditional saturated core FCL (SCFCL), is that it does not rely on any external controller, sensor, controllable solid-state switch, and battery. In the normal state, the SAFCL behaves like a saturated reactor with a very low impedance and in the fault state, cores are entered to the unsaturation region without relying on an external controller which imposes a high impedance to limit the fault, rapidly. The performance of the SAFCL is evaluated through off-line MATLAB and Maxwell ANSYS FEM simulations, and is also validated by experimental studies conducted on a scaled-down prototype.

Vibration detection method for core loosening degree of high‐voltage direct current converter valve saturable reactor based on variational mode decomposition‐symmetrized dot pattern and image matching

Saturable reactor is the key equipment in converter valves; it is important to evaluate the core condition. In this paper, a recognition model of saturable reactor core loosening based on variational mode decomposition (VMD)-symmetrized dot pattern (SDP) feature fusion images and scale-invariant feature transform (SIFT) was proposed. Firstly, the saturable reactor vibration test under high frequency pulse excitation was carried out, and the vibration signals in different core loosening degrees were collected. Secondly, the VMD algorithm was used to decompose the broadband vibration signal into multiple narrowband functions, which were used to reflect the characteristics of each frequency band. Thirdly, each function and the original signal were transformed by SDP, the generated spiral arms were fused into a new image, and the typical templates in different loosening degrees were selected. Finally, the improved SIFT algorithm was used to obtain the matching results between test sets and templates. The results show that the recognition accuracy of the proposed model for core loosening is 97.5%, which is better than traditional algorithms. It can find the core loosening defect early and avoid further failures such as water pipe break and discharge, which can provide an important basis for saturable reactor monitoring.

Silica nanofluid in low salinity seawater containing surfactant and polymer: Oil recovery efficiency, wettability alteration and adsorption studies

Production of crude oil from a matured oil reservoir is challenging due to the low recovery factor. Hybrid methods have demonstrated potential in oil recovery from the matured crude oil reservoir. In recent years, the low salinity water with chemicals (viz., surfactant, polymer) and nanoparticles have brought the attention of the researchers due to their ability in altering the interfacial properties of the rock-oil-water systems favorable for crude oil recovery. The current interest by industries in injection fluid (i.e., low salinity water injection) has prompted the invention of a hybrid oil recovery agent for matured crude oil reservoirs. In the current study, a novel silica-based hybrid nanofluids (NFs) of variable silica nanoparticles (NPs) concentration in low salinity seawater with anionic surfactant (AOT: dioctyl sodium sulfosuccinate) and polymer (PVP–K30: polyvinylpyrrolidone) (sometimes referred to as SMART LowSal) are used as an injection fluid in a sand-pack reactor. Oil recovery from oil saturated sand-pack reactor is observed to enhance due to NFs (hybrid) injection after secondary recovery. The characteristic study of relative permeability curves discloses that sand surface was initially water-wet and converted to strongly water-wet in the presence of NFs. A nuclear magnetic resonance (1H NMR) study reveals that adsorption of the chemical appeared on the sand surfaces, which could be the reason for wettability alteration, and thereby enhanced oil recovery. Similarly, the scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA) of the sand samples before and after injection disclosed desorption of hydrocarbon from the sand surfaces after NFs injection. An additional 5–10% oil recovery is achieved after chemical flooding due to the injection of NFs. Adsorption isotherm study well agreed with the monolayer adsorption of surfactant on the sand surface.

Research on Losses and Heat Dissipation of Saturable Reactor Used in Converter Valve

Based on the analysis of the principle and structure of a saturable reactor used in a converter valve of HVDC transmission, this paper analyzes its power loss composition and summarizes and derives the power loss equations. According to finite element analysis, the saturable reactor is modeled, its transient electromagnetic characteristics are simulated, and the core loss density distribution is studied. The influence of the cooling circuit and air on the heat dissipation of the saturable reactor is studied. The power loss density obtained by the electromagnetic field finite element analysis is mapped as the heat source to the finite fluid element for thermal simulation in order to obtain the spatial temperature distribution of the saturable reactor. The maximum temperature of the case is about 68.5°C, while the maximum temperature of the iron core is about 87.9°C. The converter valve operation test validates the accuracy of the heat dissipation analysis and temperature field simulation. The research results can serve as a reference for the design of saturable reactors used in converter valves.

Core Loss Calculation of Anode Saturable Reactor in Damping Oscillation State Based on J-A Theory

Anode saturable reactor (ASR) is an important part of the HVDC converter valve. Due to the surge current during the transient processes of thyristors, a sharp increase will occur in core losses and over temperature-rising of the reactor, which may cause premature failure and is difficult to estimate in the design optimization of the reactors. To investigate the single core loss of anode saturable reactor, during such operating conditions, this paper proposes an approach to calculate the core loss from the Jiles-Atherton (J-A) dynamic hysteresis model, which can be applied for various operating conditions with good accuracy. Finally, the model is incorporated into the finite element method (FEM) to investigate the core loss distribution of the iron core during the oscillation process at off-state.

Magnetic-Thermal Coupling Analysis of Saturable Reactor

As the vital equipment of ultra-high voltage direct current (UHVDC) transmission, the anodic saturable reactor is crucial to the safe operation of converter valve. Based on dynamic core loss model, the eddy current analysis and core loss calculation on saturable reactor are carried out by finite-element method (FEM) simulation software Maxwell. Through the fast-mapping interpolation method between heterogeneous meshes, the core loss is mapped from electromagnetic field to the fluid field by Fluent user-defined functions (UDFs), which makes the distribution of heat source more realistic. The distributions of temperature and velocity of the anodic saturable reactor are obtained by computational fluid dynamics (CFD) simulation software Fluent. The temperature simulation results show that the hottest spots inside the core and on the reactor inner toroidal surface are 117.4 °C and 80.5 °C, respectively. The experimental results demonstrate the validity of the calculation methods of core loss and temperature distribution.

A magnetically controlled series compensation-fault current limiter

This paper presents a magnetically controlled series compensation-fault current limiter (MCSC-FCL) which is composed of a magnetically controlled reactor (MCR) and a compensation capacitor. The device is improved from the traditional thyristor-controlled series compensation (TCSC), which has the characteristics of small output harmonics and simple control. The traditional saturated iron-core reactor is improved to increase the adjustable range of output reactance. During the fault, the MCR is connected to the grid alone to limit fault current; when the grid is normal, MCR and capacitor are used in series compensation mode. It effectively improves the utilization rate of the traditional current limiter MCR. In order to verify the effectiveness of the proposed MCSC-FCL, this paper analyzes the control characteristics of reactor models with different air gap structures by JMAG finite element analysis software, and verifies the voltage regulation characteristics and fault current limitation capabilities on MATLAB/Simulink platform.

Study for Influence of Harmonic Magnetic Fields on Vibration Properties of Core of Anode Saturable Reactor in HVDC Converter Valve System

The cores of anode saturated reactor (ASR) are the main vibration source of the HVDC converter valve system. The ASR is excited with an impulse voltage, which contains many harmonic components, and the magnetostriction of cores is usually the main reason of the ASR vibration. Therefore it is significant to study the influence of the harmonic on the vibration of core of ASR. In this paper, the magneto-mechanical coupling model is established based on the magnetostriction theory and the expression of vibration acceleration in the presence of third harmonic is derived. The vibration test platform is built to test the core's vibration acceleration. The magnetic and magnetostrictive properties of silicon steel sheet under different working conditions are measured. The three-dimensional simulation model of the core is established, and the vibration acceleration under different magnetic flux density is calculated. The comparison of the experiment and simulation results shows the rationality of the magneto-mechanical coupling model. The influence of third harmonic magnetic flux density on vibration is studied by changing the phase of the third harmonic magnetic flux density and the ratio of the third harmonic magnetic flux density to the fundamental magnetic flux density. Both the calculated and measured results show that the third harmonic magnetic flux density affects the vibration acceleration according to the double-frequency components of the third harmonic, as well the sum-frequency and difference-frequency components of the third harmonic and fundamental frequency.

Corrigendum: Partial discharge characteristics of an air gap defect in the epoxy resin of a saturable reactor under an exponential decay pulse voltage

Corrigendum: Partial discharge characteristics of an air gap defect in the epoxy resin of a saturable reactor under an exponential decay pulse voltage