Saturable Reactor Research Articles

Development and modelling of a steel slag filter effluent neutralization process with CO2-enriched air from an upstream bioprocess

The main objective of this project was to develop a steel slag filter effluent neutralization process by acidification with CO2-enriched air coming from a bioprocess. Sub-objectives were to evaluate the neutralization capacity of different configurations of neutralization units in lab-scale conditions and to propose a design model of steel slag effluent neutralization. Two lab-scale column neutralization units fed with two different types of influent were operated at hydraulic retention time of 10 h. Tested variables were mode of flow (saturated or percolating), type of media (none, gravel, Bionest and AnoxKaldnes K3), type of air (ambient or CO2-enriched) and airflow rate. One neutralization field test (saturated and no media, 2000–5000 ppm CO2, sequential feeding, hydraulic retention time of 7.8 h) was conducted for 7 days. Lab-scale and field-scale tests resulted in effluent pH of 7.5–9.5 when the aeration rate was sufficiently high. A model was implemented in the PHREEQC software and was based on the carbonate system, CO2 transfer and calcite precipitation; and was calibrated on ambient air lab tests. The model was validated with CO2-enriched air lab and field tests, providing satisfactory validation results over a wide range of CO2 concentrations. The flow mode had a major impact on CO2 transfer and hydraulic efficiency, while the type of media had little influence. The flow mode also had a major impact on the calcite surface concentration in the reactor: it was constant in saturated mode and was increasing in percolating mode. Predictions could be made for different steel slag effluent pH and different operation conditions (hydraulic retention time, CO2 concentration, media and mode of flow). The pH of the steel slag filter effluent and the CO2 concentration of the enriched air were factors that influenced most the effluent pH of the neutralization process. An increased concentration in CO2 in the enriched air reduced calcite precipitation and clogging risks. Stoichiometric calculations showed that a typical domestic septic tank effluent with 300 mg/L of biodegradable COD provides enough biological CO2 for neutralization of a steel slag effluent with pH of 10.5–11.5. A saturated neutralization reactor with no media operated at hydraulic retention time of 10 h and a concentration of 2000 ppm in CO2 enriched air is recommended for full-scale applications.

Electromagnetic vibration of controllable saturable reactor under different DC control current

Controllable saturable reactor (CSR) has been developed rapidly because of its continuous adjustable output characteristics. However, the vibration of the saturated core is serious and becomes a bottleneck problem in its application. Electromagnetic vibration analysis become an essential part in de signing and manufacturing. In this paper, the electromagnetic vibration of cores and windings of CSR under actual working conditions was numerical calculated and measured. In order to obtain the magnetic properties, magnetization curves under DC bias were got through repeated measuring with different setting and simple calculation. Magnetostriction (MS) was measured by laser interferometer under DC bias. Based on the measured properties under different DC control current, magnetic field was firstly analyzed and the magnetic forces, which include Lorentz, Maxwell and magnetostrictive force, were calculated. Then the vibration of cores and windings due to electromagnetic forces were calculated by using a weak 3D magneto-elastic model under actual working conditions. Finally, the vibration of a CSR, which is a single-phase prototype with 4.4 kVar/220 V, were tested and analyzed. The error between measurement and calculation results is in a reasonable range.

Numerical Investigation on Residual Axial Magnetic Field in Vacuum Interrupter in DC Interruption Based on Artificial Current Zero

The residual axial magnetic field (AMF) at current zero, which is caused by large $\mathrm{d}i/\mathrm{d}t$ during the forced current-zero stage of DC interruption based on the technique of artificial current zero, has a significant influence on the interruption performance of the vacuum circuit breaker. In this paper, a model of AMF contacts system is developed by finite-element-analysis software Ansys. The eddy current induced in the contacts system is also analyzed by an equivalent circuit. The influence of the frequency of countercurrent and the characteristics of saturable reactor, which results in the change of $\mathrm{d}i/\mathrm{d}t$ before current zero, are investigated. The results demonstrate that the frequency of countercurrent has a significant influence on the residual AMF at current zero. The residual AMF decays exponentially after current zero with a time constant independent of the countercurrent frequency. The residual AMF can be reduced by using a saturable reactor. The effect of a saturable reactor depends mainly on the duration of the low $\mathrm{d}i/\mathrm{d}t$ stage before current zero.

Magnetically Controlled Saturable Reactor Core Vibration Under Practical Working Conditions

In order to seek new vibration reduction method for magnetically controlled saturable reactors (MCSRs), this paper studies the stress characteristic which is the inherent reason of vibration and noise. Under the practical working condition, dc and ac excitations make iron cores work in a magnetic saturation state. Meanwhile, the stress in reactor cores always exists and influences on magnetic properties of the core material. Because the core material shows different magnetization and magnetostrictive properties under dc bias and stress, a database of magnetization and magnetostrictive curves of silicon steel under different tensile stresses with different dc bias excitations is tested. Based on the measured constitutive relations, an electromagneto-mechanical two-way coupled numerical model for MCSRs is presented. Vibrations considering magnetostrictive effect, electromagnetic force effect, and the combination of them are calculated to compare the influence of the two forces on MCSR vibration. From the computation results, it can be seen that the total vibration stress is not a simple superposition of electromagnetic stress and magnetostrictive stress. Finally, vibration stress of an MCSR prototype under working conditions is tested to prove the validity of the proposed model.

Vibration of saturable reactor core used in HVDC converter valve system

Vibration of saturable reactor core used in HVDC converter valve system

Saturated core voltage regulators: parameterization, computational models, and performance studies

Summary Despite recognition from a vast number of publications that contemplate performance studies of so called saturated reactors aimed at voltage regulation, the subject, when weighed against the benefits, such as new material based technologies and application perspectives, still presents various challenging topics. In fact, investigations made concerning the physical principles governing its constructive design, the retrieval of representative electric and magnetic parameters, the development of computational models, enabling means for evaluating the effectiveness of the processes for restoring the busbar voltage, among other aspects, are still deserving of research, development and modeling. Given this setting, the present paper considers aspects that guide the physical design concepts and parameterization of these devices, computational strategies aimed at the computational modeling and evaluation of such equipment in voltage regulation and other correlated phenomena. Theoretical results are compared to corresponding experimental performances intent on defining the established models' degree of adhesion.

Performance Analysis and Prototype Design of a D-Core-Type Single-Phase HTS Controllable Reactor

Controllable reactor is widely applied as a reactive power compensation device to improve the stability of power grid. This paper describes the principle and equivalent magnetic circuit of a new D-core-type HTS controllable reactor in detail. A D-shaped core was assembled with one straight limb, on which an alternating-current working winding was wound, with two parallel rectangular magnetic yokes and four excitation cores between the parallel yokes with direct-current HTS control windings wound around and connected in series with each other. In general, the magnetic flux of the windings for different purposes is orthogonal at the joint and parallel in the parallel yokes. Compared with traditional saturable controllable reactor, the proposed layout can weaken electromagnetic induction between working winding and control windings significantly. Meanwhile, the HTS windings were used to reduce the volume and supply a more effective excitation. In our studies, a 380-V/7.6-kVA single-phase controllable reactor was designed. The reactance, harmonic, and inductive voltage features were analyzed to demonstrate the performance of this type of reactor.

A Novel Circuit of Marine Controlled-source Electromagnetic Transmitter

The marine electromagnetic transmitter sends high-power variable-frequency electromagnetic waves to acquire seabed structure and distribution law of mineral resources. The traditional transmitter has some shortcomings, such as small power, low efficiency, and poor load adaptability. In this article, a novel transmitter circuit composed of zero voltage zero current switching (ZVZCS) controlled-source circuit is proposed, which overcomes the limitations of a zero-voltage switching one, such as high freewheeling energy, duty ratio loss, and limited zero-voltage switching load range for the lagging-leg switches. Current in primary winding during the freewheeling period is reduced to zero by using a blocking capacitor and a saturable reactor, realizing zero-current switching turn-on for leading-leg switches, as well as zero-current switching for lagging-leg switches. Finally, the proposed circuit is verified by a 200-A marine transmitter.

Valve saturable reactor iron losses of ultrahigh‐voltage direct current converter

Thyristor-based line-commutated converters (LCCs) are widely used to achieve AC/DC and DC/AC power conversions in UHVDCs (ultrahigh-voltage direct currents) transmission. Valve saturable reactors are used to protect power thyristors. To improve the efficiency of bulk electricity transmission over long distance, the operating voltage and current of UHVDCs and therefore the thermal stresses applied to the valve saturable reactors have steadily increased over the last decades. Valve saturable reactor iron losses were studied by accounting for the reverse recovery characteristics of the valve thyristors and the non-linear characteristics of the saturable reactors. The impact of UHVDC current on valve saturable reactor iron losses was quantified and verified. The valve saturable reactor iron losses of an LCC are generated not only at the turn-on and turn-off periods of the valve, but also at the off-state of the valve. The amount of the losses are affected by the AC busbar stray capacitances of the converter, the valve firing and extinction voltages, the rates of change of valve commutation current, and the reverse recovery current of the valve thyristors. The conclusion obtained will help to understand better the forming mechanism of valve saturable reactor iron losses and optimise the valve saturable reactor design.

Study on EMTP Simulation Applying Dual Reactor for Prevention of the Ferro-resonance and VT Burnout in Substation System

Abstract When the line and switchgear of the substation system are disconnected, ferro-resonance can occur. This happens even if the capacitive reactance and inductive reactance are not equal, which are not common resonance conditions. Resonance conditions vary depending on the busbar configuration environment. Although the damping resistance method applying the existing saturable reactor to cope with ferro-resonance has been su ccessfully applied on site, th ere can be loss of normal function during long-term operat ion. The reason is because the rise in the operating frequency of saturable reactors means the saturation number is increased. Therefore, it can no longer function as saturable reactor since the resistor having inadequate capacity is burned out. To address this problem, in this paper, an EMTP-based simulation test was performed by designing and applying a dual reactor method, which adds an extended divergence reactor to the 1st side of the VT. The test result confirms that when the divergence reactor is inserted, the voltage and current values obtained at the 1st side and 2nd side of the VT as well as current values of divergence reactor part were stabilized from the transient phenomena and return to normal values. When compared with existing measures, although this method is similar in adding having a reactor added to a system regarding ferro-resonance, it has the advantage of being able to prevent ferro-resonance in advance since the reactor is added before the system is s aturated. In addition, because it does not use damping resistance, it can extend the equ ipment life and stabilize its operation. Therefore, there are a lot of differences in terms of its operating characteristics and achivement of goal between the conventional method and new divergence reactor method.

Electronic Tuning of Misaligned Coils in Wireless Power Transfer Systems

The misalignment and displacement of inductively coupled coils in a wireless power transfer system (WPT) can degrade the power efficiency and limit the amount of power that can be transferred. Coil misalignment leads the primary coil driver to operate in an untuned state which causes nonoptimum switching operation and results in an increase in switching losses. This paper presents a novel method to electronically tune a Class-E inverter used as a primary coil driver in an inductive WPT system to minimize the detrimental effects of misalignment between the inductively coupled coils which may occur during operation. The tuning method uses current-controlled inductors (saturable reactors) and a variable switching frequency to achieve optimum switching conditions regardless of the misalignment. Mathematical analysis is performed on a Class-E inverter based on an improved model of a resonant inductive link. Experimental results are presented to confirm the analysis approach and the suitability of the proposed tuning method.

Simulation Study on Iron-Core Loss of Saturable Reactor at Rectifier Valve Side in HVDC Transmission Line

A PSCAD based 12-pulse converter model for HVDC power transmission, in which the thyristor model with reverse recovery characteristics and the model of nonlinear saturable reactor composed of nonlinear resistance model and controlled current source are contained, is built to research the influences of the transmitted DC current on the iron-core loss of the saturable reactor. Taking the A5000 converter valve used in the rectifier side of ±800 kV/4 750 A UHVDC transmission project from Jinping to Sunan as the example, the iron-core losses of the saturable reactor under three different operation conditions of the UHVDC transmission line are simulated, and the simulation results conform to the on-side measured data. The iron-core loss of the saturable reactor not only comes into being while the converter valve is switching on, but also during the switching off and the off-state of the converter valve. The iron-core loss of the saturable reactor increases with the rise of the DC current.

Evaluation of Three Designs for a 35-kV Class Superconducting Reactor

With the expansion of the grid, continuous reactive power compensation is vital for efficient operation of long transmission power lines or cables. Yunnan Electric Power Grid Company is planning to develop superconducting controllable reactors for 500-kV long-distance ac transmission lines. As the second stage of the development plan, a 35-kV class superconducting reactor will be designed and verified by experiments. In this paper, three design proposals, including the racetrack-core type, the three-limb-core type, and the D-core type, for the 35-kV class superconducting reactor are given. Then, their technical and economic feasibility is evaluated. This paper shows that the racetrack-core saturable reactor is a good choice from a technical and economic point of view.

A multi-valve controlled saturable reactor and its harmonic optimization

Purpose – As arc suppression coils (ASCs), magnetically controlled reactors (MCRs) are usually operated in the single-phase mode. Due to the lack of a third order harmonic compensation circuit, the current harmonics are high. The purpose of this paper is to propose a novel structure of MCR and a genetic algorithm (GA) to determine the parameters which will result in minimum total harmonics. Design/methodology/approach – This paper proposes the structure and the working principle of the multi-valve controlled saturable reactor (MCSR). There are several sorts of magnetic valves in the iron cores of the MCSR. The saturation degree of each magnetic valve is different when the same direct component of the magnetic flux is generated in the iron core, therefore current harmonics of different phases emerging, i.e. the total harmonics can be reduced. The magnetization characteristics and the mathematical model of the current harmonics of the MCSR are presented by introducing three parameters. The optimal values of the parameters that result in the smallest total harmonic distortion in the output current are calculated by a GA. Findings – The simulation and experimental results are coincident with the theoretical analyses, which prove the effectiveness of the proposed method on harmonic suppression. Practical implications – The method proposed in this paper can successfully reduce the current harmonics of the conventional MCR, including but not limited to the ASC. A prototype MCSR (540 kVA/10 kV) has been designed and constructed. Originality/value – In this paper, a MCSR is proposed. The mathematical model of the MCSR for harmonic analysis is developed. The optimal parameters that result in the smallest THD in the output current are calculated. The mathematical model can be also used for the harmonic analysis of conventional MCRs.

Study of a Small-Scale Controllable Reactor and Conceptual Design of a 35kV/5Mvar HTS Reactor

Since Ultra High Voltage (UHV) transmission lines have the high charging capacitance, continuous reactive power compensation is vital for efficient operation of long transmission power lines or cables. A continuous reactive compensation will reduce the transmission losses and increase the transmission capacity of active power. In order to achieve the continuous reactive power compensation, we choose the magnetic saturable type reactor. The principle of a magnetic saturable reactor requires a high current ampere-turn coil as its dc bias, and this coil is necessary to use a high temperature superconducting (HTS) winding. As the first stage of the study, we have constructed a 220V small-scale prototype which the dc bias is made of copper coil instead of the HTS coil. The copper coil of the dc bias in small-scale reactor has the same ampere-turn with a 220V HTS controllable reactor (HCR), so its performance keeps the same except the HTS part. Based on this, we made a conceptual design for a 35kV/5Mvar HCR. The output property and harmonic property have been studied by simulation and experiment. The results prove that it can obtain a continuous controllable reactive power output.

Tuning Class E Inverters Applied in Inductive Links Using Saturable Reactors

This paper investigates the performance of Class E inverters used in wireless power transfer applications based on resonant inductive coupling. The variations in the load and the distance between the coils cause Class E inverters to operate under nonoptimal switching conditions, which result in inefficient operation and can lead to permanent damage to its switching transistor. Therefore, a novel approach to tune Class E inverters electronically is proposed. The tuning method relies on saturable reactors to ensure that the inverter operates under optimal switching conditions regardless of variations in the load and the distance between the coils. In addition, a more accurate model of inductive links is presented in order to provide a better understanding of the major power losses in resonant inductive links. Experimental results are presented to confirm the improved accuracy of the inductive link model and the validity of the tuning method.

Demand Side Frequency Control Scheme in an Isolated Wind Power System for Industrial Aluminum Smelting Production

Reducing the fossil fuel consumption of aluminum smelting production, which consumes around 8% of electricity annually, is of great significance for China's energy sector. One possible solution is to integrate wind power as supply for aluminum smelter loads. Based on this background, this paper studies an actual industrial case-an isolated power system for aluminum production with integrated wind penetration levels as high as 30%. However, due to the integration of wind power, frequency stability issues become critical in such a system. Therefore, a demand-side frequency control scheme responding to frequency deviations of the system is proposed in this paper to control the load power of aluminum smelters. The scheme is designed based on the relationship between the DC voltage supply for aluminum smelting loads and the commutation voltage drop which can be adjusted by changing the inductance value of the saturable reactors. Finally, simulations under both N-1 and N-2 contingency scenarios demonstrate the effectiveness of the proposed control scheme considering various wind power outputs.

A Low Energy Aqueous Ammonia CO2 Capture Process

Abstract The most pressing challenges regarding the use of ammonia for CO 2 capture are the precipitation limitation and the energy penalty of solvent regeneration. Precipitation-free operation is a vital task since solids may cause the shutdown of the plant. Precipitation and slurry formation can be avoided by increasing temperature and L/G ratio but this leads to higher heat consumption, jeopardizing the economic feasibility. Here we developed, investigated, and optimized a novel CO 2 capture process design using aqueous ammonia as solvent. The proposed configuration replaces the traditional stripper for solvent based CO 2 capture with a thermal decomposition reactor. The overall energy penalty is reduced at the expense of introducing a solid handling section which consists of a saturation reactor, a crystallizer and a belt filter. The feasibility of the present approach is demonstrated by simulation. Flow-sheet calculations are performed in Aspen Plus using the extended UNIQUAC thermodynamic model for vapor-liquid-solid equilibria and for thermal properties calculation of the CO 2 -NH3-H2O system. The simulation results show that the specific regeneration duty of the novel capture alternative is comparable with existing aqueous ammonia CO 2 capture processes. Moreover, the thermal reactor can operate at 1 bar and 86 °C, therefore the NH3 regeneration temperature is reduced by approximately 50 °C. The integration of low- and mid- temperature waste heat becomes possible which can greatly improve the economics of the process. The present capture alternative is especially convenient for power plants but is also beneficial for the cement, steel and aluminum industry. Special attention is given to the ammonia slip prediction. The calculations substantiate that the slip above the absorber is 0.1 mol % after washing with the rich solution and it reduces below 100 ppm by washing with low temperature water.

Simulation Analysis of Control System in an Innovative Magnetically-Saturated Controllable Reactor

Controllable saturation reactors are widely used in reactive power compensation. The control system of controllable saturation reactor determines adaption speed, accuracy, and stability. First, an innovative type of controllable saturation reactor is introduced. After that the control system is designed, and a self-tuning algorithm in PID controller is proposed in the paper. The algorithm tunes PID parameters automatically with different error signals caused by varied loads in power system. Then the feasibility of the above algorithm is verified by Simulink module of Matlab software. The results of simulation indicate that the control system can efficiently reduce adaption time and overshoot.

Design of HTS Magnetically Controlled Saturable Reactor

There are many problems for traditional reactive power compensation devices to be applied in the grid, such as discontinuous adjustment, small capacity, complex control and harmonics. This paper aims to study a high temperature superconducting magnetically controlled saturable reactor (HTS MCSR), which has a wide range of stepless adjustment. It has a good application prospect in large scale reactive power compensation devices. Based on research of theory and core structure, a shaped-cylinder core is proposed. By means of calculation of saturable reactor and analysis of algebraic and magnetic circuit model, design of 220V HTS MCSR is finished. Results of normal conductive reactor prototype and simulations verify that the range of inductance adjustment is very wide. Furthermore, conceptual design of 35kV HTS MCSR confirms its reactive power capacity is so large, therefore, it is suitable for high voltage power system.