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As the vital equipment of UHVDC (ultra-high voltage direct current) 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 UDF, 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 °C and 80.5 °C, respectively. The experimental results demonstrate the validity of the calculation methods of core loss and temperature distribution.

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.

A saturable reactor is one of the important components of converter valves in high-voltage direct current transmission systems. With the ever-increasing capacities of converter valves, the heat losses generated by saturable reactors are also increasing. Thus, a thermal–fluid mechanics coupled heat dissipation model for saturable reactors is proposed. In order to study the factors affecting the thermal dissipation in the saturable reactor, the epoxy resin insulating layers with different thermal conductivity were considered in this work. The simulation results showed that the hot spots in the saturable reactor are on the iron core and close to the pipe inlet that most of the generated heat can be extracted by a cooling pipe and that the effect of heat dissipation can be improved by raising the thermal conductivity of the epoxy resin. The thermal conductivities of the epoxy resin used in the two reactors were 0.8 and 1.2 W/mK, respectively. The time dependence of the iron core temperature was in accordance with the simulation results and the maximum temperatures of the saturable reactor were also consistent with the simulation results. By increasing the thermal conductivity of the epoxy insulation layer, the temperature of the iron core could be significantly reduced.

Saturable reactor insulation is currently stressed by an exponential decay pulse voltage under normal operating conditions. The partial discharge (PD) characteristics of epoxy resin under an exponential decay pulse voltage were studied here and were compared at 25 and 110°C. In addition, this study compares these PD characteristics with those under a sinusoidal voltage to better measure the insulation design margin of the saturable reactor under an exponential decay pulse voltage. Finally, this study explains the PD mechanism based on the three-capacitor circuit model and space charge accumulation. Compared with the sinusoidal voltage, a higher amplitude, a higher inception voltage and fewer PDs are obtained under the pulse voltage. The reason may be related to the accumulation of space charge. Due to the duality of the space charge effect, the promotion effect of space charge accumulation on the PD under the pulse voltage is dominant, and an increase in temperature will weaken the promotion effect. In contrast, the inhibitory effect of space charge accumulation on the PD under the sinusoidal voltage is dominant. The experimental results can provide a basis for the optimal design of saturable reactor insulation under an exponential decay pulse voltage.

In this paper, a double-layer half-cycle generator (HCG) has been designed and built. The proposed HCG creates sinusoidal flow with 400 A peak and 5 µs pulse width which feeds RLC load with 100 kHz work frequency, within resonance mode. Previous HCGs have been designed based on saturable reactor (SR). It should be noted that SR is a nonlinear element, and it will be distanced from its desirable performance upon change of temperature and under impact; however, a double-layer HCG has been proposed with no such defects. In proposed HCG, thyristor has been used instead of SR which is controllable, and it has none of aforementioned problems. Also, when SR is eliminated, its reverse retrieval needs no minority carriers. This way, sweep-out circuit may be also eliminated. From among other advantages of proposed HCG, reduction in number of circuit layers may be referred to, comparing to previous HCG. This results in reduction in number of equipment which in turn optimizes proposed HCG, in terms of volume and manufacturing costs. Finally, proposed HCG has been simulated in Matlab, while it has been implemented practically. Comparing simulation results and laboratory sample confirms correctness of relationships, in analytical design of HCG.

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.

This paper proposes a high-efficiency and high step-down isolated DC-DC converter using a saturable inductor for point-of-load (PoL) converter applications. The saturable reactor helps in reduction of frequency range of peak current control strategy. This method offers enhancement of light load efficiency in addition to soft switching operation throughout the load range. Circuit analysis details of frequency variation of peak current control, using saturable reactor is presented. Effectiveness of the proposed solution is verified in simulation and then validated with experimental results.

Control of power flow in transmission lines allows avoiding overload situations and unbalances between them. Situations like this can be managed and avoided by the application of a saturable core reactor (SCR) to the latter, thus resulting in more reliable transmission systems. In this work, such a device, integrating a control system that monitors line current, is presented. The SCR includes a DC coil that allows saturating its core through a controlled current, which, in this case, is built of high-temperature superconducting tape, to eliminate losses. According to the maximum allowed or desired line current, the control system adjusts the inductance of the device, which is magnetically coupled to the grid. Therefore, the reactance of the line is changed, which varies the voltage drop and the power flow level in the electric transmission system. This paper presents a model of a superconducting saturable core reactor and its application to power flow control.

The saturable reactor insulation epoxy resin is subjected to exponential decay pulse voltage under normal operating conditions. It is of great importance to study the partial discharge (PD) mechanism of epoxy resin under exponential decay pulse and sinusoidal voltages for optimal insulation design. Thus, the difference in the PD behaviours under the exponential decay pulse and sinusoidal voltages is revealed in this study for the first time, and the PD characteristics of the two types of voltages are compared and analysed at 25 and 110°C. Compared to the results for sinusoidal voltage, a higher amplitude, lower repetitive PD inception voltage peak (RPDIV) and fewer PDs are obtained under an exponential decay pulse voltage. Additionally, for the same type of voltage, the RPDIV is lower, the PD magnitude is higher and the number of PDs is smaller at 110°C than those at 25°C. The experimental results can provide a new reference for the insulation redesign of a saturable reactor under an exponential decay pulse voltage.

In recent years, new energy power generation has developed rapidly, and how to absorb the fluctuation of power grid frequency caused by the fluctuation of new energy is the main direction of future development. Using the damping effect of load to simulate the response of load to frequency deviation plays an important role in system frequency response. Usually, the damping coefficient of load is considered as a constant, which can not be adjusted, and is usually measured by practice. This paper studies the effect of electrolytic aluminum with large industrial load on frequency response of power grid. Electrolytic aluminum load is a voltage-driven DC load, which has no frequency response, but has large load capacity and great adjustable potential. Based on this, this paper studies a load damping control method, which responds to the system frequency change by controlling the saturable reactor. The simulation results verify the effectiveness of the proposed control method.

Continuously Variable Series Reactor (CVSR) can regulate its reactance on the ac side using the nonlinear ferromagnetic core, shared by an ac and a dc winding for applications like power flow control, oscillation damping, load balancing and others. In order to use a CVSR in the power grid, it is essential to know its operating characteristics. The Gyrator-Capacitor approach has been applied to model the magnetic circuit coupled with the electrical circuit. In the paper, we investigate the CVSR behavior in terms of induced voltages across the dc winding, flux densities (B) through the core legs, and power exchange between the ac controlled and the dc control circuit., Comment: Kansas Power & Energy Conference 2021. arXiv admin note: text overlap with arXiv:2103.11136

For common network problems such as voltage drops, reactive power unbalances and harmonic effects, which are common power quality problems, different techniques have been developed. Harmonic filters, various compensators are used for reactive power requirement and harmonic elimination. When magnetic controlled reactors (MCR) are examined in power systems, it is seen that it is a very effective method especially on problems such as unbalance of reactive power and suppression of overvoltages. When the advantages such as fast control structure, low delay values and usage points at high voltage levels are examined, it is seen that MCR structures are very effective in providing power quality. In this study, the working structure and mathematical equations of MCR are obtained, the control characteristic are examined. More importantly, an efficient model is proposed for analysis of MCR

Current sensor plays an important role in power industries, the information obtained from the current sensor is used for controlling, motoring and protection. The paper gives comprehensive review regarding various current measurement schemes used in industries and utilities for DC current measurement. Especially, the technical issues including difficulties in hardware implementation among all current sensing schemes like Hall Effect based current transducer, typical shunt resistor method, saturable core reactor technique and fiber optic current sensor have been extensively discussed. The comparative analysis of these methodologies have been presented.

Uncertainty of the wind power output is the main influence factor for wind power utilization in the bulk power system. Because of the large capacity and the load characteristic, energy-intensive load holds great potentials to share the burden of wind power fluctuation smoothing. In this paper, a direct control scheme of the energy-intensive load power is proposed to smooth the wind power fluctuation. Based on the characteristic of the energy-intensive load production technology, the feasibility of energy-intensive load control and its influence on the production are discussed. A feedback control is designed to regulate the saturable reactor and transformer tap changer when the power support from the bulk power system is limited. Regulation capacity is analyzed quantitatively based on the energy-intensive load equivalent circuit model. A grid-connected energy-intensive enterprise driven by self-generation wind power plants and thermal power plants is studied as an example case. By the proposed energy-intensive load control scheme, power fluctuation of the wind farms can be smoothed with the minimum control cost. Besides, the regulation requirement of the bulk power system is eased correspondingly so that the utilization capacity of the power system can be improved significantly. Simulation is done on the real-time digital simulator to verify the effectiveness of the proposed control method.

Despite remarkable achievements in the field of Jiles–Atherton (JA) hysteresis theory, JA hysteresis modeling remains challenging given that most commercial software still lacks a practical dynamic JA hysteresis reactor model for electromagnetic transients. A novel voltage-driven dynamic flux linkage–current (ψ–i) JA hysteresis reactor in Electromagnetic Transients Program–Alternative Transients Program (EMTP–ATP) is developed in this study. The proposed model is based on flux linkage and current instead of magnetic flux density and magnetic field. Voltage-driven dynamic losses are incorporated into the static ψ–i JA hysteresis model by using Type-94 element in EMTP–ATP. The two proposed models in this paper are validated using current tests under 50 and 150 Hz. The performance of the proposed dynamic Model 1 matches better with experiments than the dynamic Model 2. Ferroresonance tests are carried out to validate the performance of the proposed reactor. The results show that the proposed reactor has a broad application prospect in electromagnetic transient studies.

This paper addresses the development of the hybrid fault current limiter and interrupting device (HCLID) which can be used successfully as an ultra-fast short-circuit protection means for low voltage AC or DC industrial installations. The main components of the HCLID are as follows: a solid state commutation circuit that can supply a counter current injection from a stand-by pre-charged capacitor, a saturable core reactor as limiting impedance and a fast mechanical contact switch; all are connected in parallel. Through this study, a significantly improved and simplified approach that replaces the half-controllable SCR in the commutation circuit with self-turn-off device, such as IGCT, is presented. The use of high-performance semiconductors (IGCTs) as a commutating device affords reduced recovery voltage, reduced losses, improved reliability and dynamic performance, and fast switching time (in μs). The new approach is emulated in Piecewise Linear Electrical Circuit Simulation (PLECS) and involves a fault detection using rate of current rise rather than the current magnitude and a time delay operating characteristic. The proposed control method can be simply implemented. Different fault cases have been simulated in this paper. Simulation results proved the practicability and validity of the new HCLID. Keywords: Hybrid current limiting interrupting device, Self-turnoff device, Fast mechanical contact switch, Control strategy, PLECS package application

This paper presents a demand side frequency control scheme in the isolated power system for wind power local utilization. The industrial isolated power system driven by self-owned coal-fired generators and wind farms is both economical and environmentally-friendly. However, the system frequency stability issue is critical due to the lack of power support from the bulk power system. For the isolated power system, the participation of energy-intensive loads in frequency regulation is vital for frequency stability, especially when large scale wind power is integrated in the system. The coordinated control scheme by the saturable reactor and the generator exciter is investigated to realize the energy-intensive load automatic control based on the energy-intensive load model. The coordination of the two control measures significantly enlarges the energy-intensive load regulation range. Energy-intensive load can be regulated to eliminate the power imbalance in the isolated power system together with traditional frequency regulation methods. The hardware-in-the-loop (HIL) testbed is designed to verify the control effect of the proposed coordination method. Time delay of the control method is simulated in this testbed, making the experimental result more practical in the actual power system. Simulations have been carried out in the RTDS-based HIL testbed, verifying that frequency stability of the isolated power system can be maintained by the proposed coordinated control scheme.

While preparing a modern data center for startup, the commissioning process involved primary circuit switching that resulted in two voltage transformer (VT) failures. As a result, we conducted a comprehensive investigation of the VT failures. As the investigation proceeded, VT ferroresonance on circuit opening and high-frequency switching transients on closing emerged as possible root causes of the failures. After incorporating extensive transient simulations and three rounds of field transient measurements, we designed and implemented a complete solution that included the sizing of snubbers to overcome excessive switching transients and the development of a saturable reactor to protect VTs against the effects of ferroresonance. This article describes the root causes, simulations, field measurements, recommended solutions, and solution implementation for this event. The correlation between field measurements and simulation results shows the effectiveness of modeling the implemented solutions.

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 reactors (MCSRs) are widely used in high voltage power system, but they make larger vibration and noise than transformers and other types of reactors due to the gapped iron-core structure and magnetic saturation. The main reasons of MCSR vibration are magnetostrictive effect of silicon steel sheet and electromagnetic force between core discs. This paper studies the influence of these two kinds of forces on MCSR vibration, which will be used to help seek new vibration reduction method. Firstly, because MCSRs work in DC bias conditions, multigroup magnetic and magnetostrictive characteristics of silicon steel sheet considering anisotropy under different DC bias excitation conditions are tested. Secondly, based on energy variation principle and virtual work principle, an electro-magneto-mechanical coupled numerical model for MCSRs is established. In order to compare the influence of magnetostrictive effect with electromagnetic force effect on MCSR vibration, vibration accelerations caused by magnetostrictive effect, electromagnetic force and the combination of them are calculated, respectively. From the computation results, it can be seen that the total acceleration is not simple superposition of electromagnetic acceleration with magnetostrictive acceleration. Finally, vibrations of a MCSR under different practical working conditions are tested to prove the validity of the proposed model.

Voltage regulation depending on reactive power compensation is the main feature of the AC power supply system. Magnetically controllable reactors (MCR) are becoming a growing demand for this purpose. The structure and working principles of MCR are analysed in this paper while a simulation model is established. The reactive power compensation strategy based on a single loop voltage control system (SLVCS) is presented and a double loop voltage-current control system (DLVCCS) is proposed. A comprehensive scenario is developed to mitigate reactive power compensation by using the proposed controls. Simulation results substantiate that proposed controls of MCR has a faster response in comparison to the traditional control, and it provides the least voltage variation at the line end. It also shows that the proposed control on MCR meet the desired objective of the voltage regulation and provides flexibility to ac transmission system.

In the traditional design process of magnetic apparatus, the core loss is estimated under standard sinusoidal at 50/60 Hz or square waveform excitation at high frequency. However, the air gap of the anode saturable reactor is changing due to vibration and temperature. The air gap limits the magnetic flux density by increasing the reluctance of the magnetic path and avoids core saturation. The quantitative analysis of gapped magnetic core loss and working efficiency have never been reported yet. In this paper, the theoretical calculation and electro-magnetic simulation are carried out to study the effect of shape and length of air gap on core loss and spatial magnetic field distribution so as to improve the loss calculation accuracy of the anode saturable reactor. The loss distribution and temperature rise especially near the air gap region are analyzed to optimize the design.

The threat of HEMP (high-altitude nuclear electromagnetic pulse) in power system deserves in-depth study. Saturable reactor acts as a protection device for the thyristor, and its normal operation determines the normal operation of the whole thyristor converter valve. The failure rate of saturable reactor is a key parameter for the overall reliability evaluation, whose value varies according to the electrical stress and thermal stress conditions. In this paper, a precision wideband model considering the different capacitive parasitic parameters of a saturable reactor is proposed. Then, the electrical stress, heat loss and instantaneous temperature rise of the saturable reactor in a single valve are accurately calculated. Finally, the failure mechanism of saturable reactor in HEMP environment is analyzed, which could be used in the further research on the reliability of thyristor converter valve in HEMP environment.

Under normal working conditions, the epoxy resin material in the saturable reactor of the converter valve withstand pulsed thermal stress continuously. Repetitive pulsed thermal stress is a potential threat to the durability of the insulation material. In order to study the transient temperature rise of epoxy resin in the saturation reactor under pulsed power, a simplified heat generation model is established and simulated, and the pulsed power heating and measurement platform is built to measure the temperature on the surface of the epoxy resin with different thickness under different pulsed currents. Finally, by comparing the simulation and experimental results, we find that the surface temperature of the epoxy resin with different thicknesses rises in microsecond level and shows the same trend corresponding to the pulsed current, and the peak temperature decreased linearly with the thickness of epoxy resin sample.

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.

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.

Saturable reactor used in UHVDC converter valve withstands periodic pulsed power loss, which will generate periodic pulsed electrical stress and pulsed thermal stress inside the epoxy resin insulation. The aging and life characteristics of epoxy resin insulation material under this condition are not clear yet. The operating conditions and insulation problems of saturable reactor are described in this article. Aiming at the electric and thermal aging factors, the pulsed electric aging experiment platform and the pulsed thermal effect experimental platform were designed respectively, and preliminary study on the life and aging characteristics of epoxy resin specimens were carried out. The results show that under the repeated action of the pulsed voltage, the lifetime of epoxy resin decreases with the increase of the voltage amplitude according to the inverse power law. Through magnified observation, we found that as the aging time increases, the surface roughness of the epoxy resin sample increases, and lots of pits appeared on surface. The repeated impact of pulsed heat has little effect on the surface electrical characteristics of the epoxy resin sample, but as the number of thermal shock increases, the electrical strength of the epoxy resin surface decreases.

Epoxy resin of saturable reactor for UHVDC converter valves works in high temperature condition for a long term, and it also suffers from bipolar exponential decay pulse voltage erosion. In order to study the electro-thermal aging law of epoxy resin, under the condition of 4.5 kV voltage and temperature 110 centigrade degrees, the electro-thermal aging test of 50 Hz sinusoidal voltage, rising 1.2 μs with pulse width 12 μs and falling 24 μs with pulse width 74 μs is carried out. The results show that with the increase of aging time, the dielectric constant and dielectric loss tangent value of epoxy resin increase obviously in the 10-1~103 Hz frequency range, and the aging degree of pulse voltage is lower than that of sinusoidal voltage. Therefore, the margin of the design according to the sinusoidal voltage aging is higher than that according to the bipolar pulse voltage under normal operating conditions.