High Voltage Side Research Articles

Low-Cost High-Voltage Power Supply for Hydraulically Amplified Self-Healing Electrostatic Applications

HASEL (Hydraulically Amplified Self-Healing Electrostatic) actuators have gathered momentum in recent years; they are made of very-low-cost materials, making it easy for anyone to develop their own actuators, and they are “soft” and can achieve tasks that are very difficult to complete with traditional rigid actuators, e.g., grasping soft objects. Unfortunately, HASEL actuators are driven by high-voltage (HV) power supplies, which are expensive to control accurately and difficult to scale up for multichannel applications, e.g., prostheses. This paper presents a low-cost HV power supply designed for HASEL applications that generates 2–10 kV DC at 5% of the cost of the existing HV power supplies used in HASEL actuators. At the core of our design, there is a new control strategy based on controlling the charging and discharging of the actuator from the supply’s low-voltage (LV) side rather than switching the HV side with expensive HV optocouplers. Discharge is achieved via a secondary transformer and multiplier circuit, generating a negative HV output capable of discharging the HASEL effectively and safely up to 10 kV.

Analysis and Design of a Battery and Supercapacitor‐Based Propulsion System for Electric Vehicles

ABSTRACTThis work deals with the design and development of a dual source based propulsion architecture for electric vehicles. The converter utilized for the propulsion system is derived from a conventional CuK converter, which operates in a bidirectional power flow mode. The proposed propulsion system has two energy sources: a battery and a supercapacitor (SC). The proposed system has continuous input and output currents at low and high voltage sides, which improves the cycle life of hybrid energy storage (SC and battery) and the DC‐link capacitor. Further, the proposed converter has magnetic reduction compared to a conventional two‐input bidirectional CuK converter. Moreover, an effective and simpler control strategy (only one switch is pulse width modulated (PWM) operated at a time) has been developed for energy management between sources during charging (regenerative braking) and discharging (propulsion), which is effectively verified by simulation and experimental results. Further, a frequency domain (bode plot)‐based technique is used for controller design and stability analysis of the proposed system.

Influence of a new controlled voltage regulator on the current and voltage non-sinusoidality of a power supply system

This work evaluates the influence of a new controlled voltage regulator on the current and voltage non-sinusoidality in different sections of a power supply system during smooth (discrete) voltage regulation on the high-voltage side of a shop transformer. The MatLab software application was used to develop a block-modular model for a transformer substation with the proposed controlled voltage regulator and measurement modules. The developed model was used to investigate the current and voltage non-sinusoidality in different parts of a power supply system when stabilizing the voltage at the consumer end at a given level. The study was carried out using a shop transformer with a capacity of 1 MV∙A and a voltage of 6/0.4 kV under an active-inductive character of the load with the load current phase angle of φ=45 deg. The obtained results confirm that, due to the extended functional capabilities of the proposed technical solution, the voltage at consumers is maintained at a given level under high technical and economic performance. When the network voltage is reduced by 5% and the activeinductive load current is increased by 35%, the proposed device was shown to create voltage non-sinusoidality. The voltage non-sinusoidality value does not exceed the permissible domestic and international norms. In addition, the proposed device is capable of maintaining the voltage at the consumer end at a given level. The obtained integral characteristic of voltage stabilization shows that the application of the proposed technical solution instead of the existing mechanical voltage regulator of the “switching without excitation” type allows the nominal voltage at the busbar of the switchgear to be retained. Further research will investigate voltage stabilization at consumers with simultaneous compensation of reactive power for complex improvement of technical and economic indicators of power supply systems under the conditions of unstable supply voltage and load current.

Development of transmission line monitoring terminal based on optical fiber energy transmission technology

Abstract The monitoring equipment on the transmission tower mostly uses solar energy and wind energy for power supply, which is unstable with low reliability. Based on optical fiber energy transmission technology, photoelectric energy conversion technology, and induced current energy extraction technology, a transmission line monitoring terminal that can take energy from the transmission line is developed in this paper. The energy transmission optical fiber and the composite insulator had to be put together and become a new composite insulator, which can transfer light energy from the high-voltage side to the tower through. It can supply power to the micrometeorology, tower tilt monitoring device, video monitoring, and other monitoring modules installed on the tower, and transfer the above monitoring information to the Internet cloud relying on the Internet of things technology. A new power supply scheme for transmission line online monitoring device is provided, which provides a new idea for the construction of a “smart transmission line”.

Coupling effect of electric field and corona discharge on combustion and soot formation of ethylene jet flame

The coupling of electric field (E-field) and corona discharge is designed to adjust the appearance and soot formation of the ethylene jet flame. The temperature and content of soot are measured by the improved two-color pyrometry (TCP). Experiments indicate that the flame is stretched and deflected laterally under the coupling field. The maximum temperature of soot and the proportion of high temperature zone in the flame increase, and oxidation rate of soot increases. The flame is more stable under the coupling of reverse E-field and corona discharge. From the non-coupled field to the coupling field of 100 kV/m and −100 kV/m, the temperature proportion of the flame in the range of 1700 K–1800 K increases from 0 to 44.2 % and 54.8 % respectively, and the peak oxidation rates of soot also increase by 204 % and 219 % respectively. The E-field in the coupling field accounts for the main influence. The high voltage side of the flame is affected by the ionic wind generated by corona discharge, and the amount of soot generated under the high coupling field is less than that on the left side.

Thermal safety characteristics analysis of helium xenon gas cooled small reactor system under LOCA accidents

The thermal safety characteristics of the system after a small break loss of coolant accident (SB-LOCA) in a helium xenon gas-cooled small reactor will determine whether the reactor will experience a meltdown and the duration of the meltdown. At present, research on SB-LOCA both domestically and internationally is mostly focused on water-cooled reactors, lacking relevant research on helium xenon gas-cooled reactors (He-Xe GCR). Therefore, it is of great significance to research the thermal safety characteristics of He-Xe GCR after a breach loss of coolant accident. This article improves the gas turbine model based on the original SB-LOCA analysis program for pressurized water reactors. And added a calculation model for the characteristics of helium xenon mixed gas, a heat transfer model for helium xenon mixed airflow, and a compressor model. Finally, a Brayton Cycle Reactor System Analysis program (BRESA) was developed for SB-LOCA analysis of He-Xe GCR. Explore the impact of the size and location of fractures on the thermal safety characteristics of the system using BRESA. Research has found that as the size of the rupture gradually increases, the decrease in reactor core power is greater, and the reactor power is shut down earlier. Comparative analysis of the impact of different breach positions on the residual heat removal characteristics reveals that a breach accident on the high-pressure side of the system poses a greater threat to system safety. Therefore, when setting the safety threshold for the Brayton cycle system, the focus should be on the hazards of high-voltage side breaches. This research achievement assists with the safe operation strategy of He-Xe GCR in the future.

Study on the relationship between electric field perception and distance factor of direct current overhead line

Abstract The main reason for line collision accidents in offline construction is that construction personnel have an insufficient perception of distance. In the range of viewing angles, due to the lack of reference objects, people lack a correct judgment of the actual height of overhead lines. Voltage, as the most direct electrical volume, has always been a key indicator of electrical protection. In this paper, the feasibility of electrostatic induction is verified through the combination of electrostatic field simulation and experiment, and the influencing factors of electrostatic induction are studied. The results show that electrostatic induction is strongly related to the environmental angle, and the inductive voltage increases with the increase of the high voltage side, and the increased amplitude gradually increases. In addition, the induction distance and the shape of the receiving antenna have an impact on the effect of electrostatic induction. However, the induction distance has the greatest influence on the electrostatic induction effect, followed by the length and diameter of the induction conductor. The research of this paper plays a technical guiding role in the distance measurement of transmission lines based on electric fields.

Evaluation of Transformer Protection System Coordination at ULTG Jeneponto

Power transformers are essential components in electrical power systems as they transform electrical quantities. In practical terms, electrical power systems may experience disturbances such as short-circuit faults, either between phases or to ground. One type of relay used to accommodate these faults is the Over Current Relay (OCR) for phase-to-phase faults and the Ground Fault Relay (GFR) for ground faults. This research evaluates the coordination settings of transformer protection systems at PT PLN (Persero) ULTG Jeneponto by analyzing the characteristics plot of each transformer unit. The evaluation results reveal intersecting characteristics on the high voltage (HV) and medium voltage (MV) sides of Transformers #3 Tallasa and #3 Bulukumba. By implementing recommended settings for these two transformer units, anomalies can be addressed, and the protection system can coordinate effectively.

Tailoring Li2CO3 configuration and orbital structure of CoS to improve catalytic activity and stability for Li‐CO2 batteries

AbstractThe sluggish reaction kinetics has greatly hampered the development of reversible Li‐CO2 batteries. Especially during charge, high charge voltage and possible side reactions during Li2CO3 decomposition require both high activity and strong durability of catalysts. Herein, a strategy of introducing rich sulfur vacancies is proposed, which tailors the configuration of Li2CO3 and the orbital structure of CoS to realize the dual enhancement. The calculation results show that charge redistribution by sulfur vacancies on the catalyst stretches the adsorbed Li2CO3 and consequently facilitates its decomposition. Moreover, the induced vacancies lower the S 2p band center, promoting the electrochemical stability of sulfides. Therefore, Li‐CO2 batteries with sulfur vacancy‐rich CoS exhibit a low overpotential of 1.07 V after 400 h cycling, while batteries with pristine CoS have a short lifespan that the overpotential exceeds 1.75 V after cycling for 200 h. This study not only proposes a strategy to improve both catalytic activity and stability but also paves new avenues for designing advanced catalysts for Li‐CO2 batteries and beyond.image

Interleaved bidirectional DC–DC converter with single‐phase high‐frequency isolation for the wide range of industrial applications

SummaryThis paper outlines the development of an interleaved bidirectional DC–DC converter featuring single‐phase high‐frequency isolation and employing two distinct pulse width modulations (PWMs), one for each power flow direction. The analysis of converter stages, expressions for DC voltage gains, and voltage/current stresses in continuous conduction mode are presented. The proposed converter offers several advantages, including a new modulation approach, a current ripple frequency, and voltage in two ports that are four times higher than the switching frequency. Additionally, it entails a reduction in the volume and weight of passive elements and ensures balanced current distribution between the arms. Moreover, the single‐phase transformer offers galvanic isolation between the DC bus and the battery or supercapacitor. An experimental prototype has been implemented in the laboratory to validate the mathematical and theoretical analysis for both energy flow directions under the test conditions, with a converter‐rated power of 2.5 kW, a low voltage side of 180 V, and a high voltage side of 380 V.

Fully Soft Switched Bidirectional Buck–Boost Converter With Improved Voltage Conversion Ratio and Single Auxiliary Switch

In this paper, a fully soft-switched bidirectional buck/boost converter with improved voltage conversion ratio (VCR) and minimum semiconductor devices is proposed. An auxiliary circuit which employs only one active switch along with coupled inductors technique is utilized to increase VCR and provide soft switching condition for all semiconductor devices. Soft switching condition is provided at a wide power range while the leakage inductance energy of coupled inductors is absorbed in both power flow directions. The main switches are turned on at zero voltage-zero current switching and turn off at zero voltage switching, while the switches body diodes used as the converter diodes turn off at zero current switching which alleviates the diodes reverse recovery problem. Soft switching operation and low component count especially the active switches have contributed to realize a proper converter efficiency. Moreover, the converter has maintained continuous current at low voltage side, common ground between the high and low voltage sides and switches voltage stress similar to the basic bidirectional buck/boost topology. A converter prototype at 300W and 100kHz is implemented to confirm the converter theoretical operation and analysis.

Efficient Zero-Sequence Impedance Measurement in Autotransformers Using Low-Voltage Excitation

In accordance with the IEEE standard, the zero-sequence impedance test of transformers necessitates an open or short circuit test on the high-voltage side winding. Power source excitation is applied to the high-voltage test winding using a high-capacity test power supply. To circumvent the need for a large-capacity, high-voltage test power supply in field tests, this paper proposes a method for measuring zero-sequence impedance in autotransformers based on low-voltage excitation and disconnection testing. By applying a three-phase power supply to the lowest voltage side of the autotransformer and creating a disconnection condition, an unbalanced test scenario is established. Subsequently, the composite sequence network equivalent circuit for one-phase and two-phase disconnections between the high-voltage side and the low-voltage side of the transformer is formulated. Calculation formulas for the zero-sequence impedance of the autotransformer under various conditions are derived. The accuracy of the zero-sequence impedance is verified using MATLAB/Simulink simulation software 2018b, evaluating double-winding and three-winding autotransformers in breaking tests under different connection modes. The error is found to be less than 3%. The results of this study affirm the high accuracy of the proposed method.

Study of the influence of the current distortion power of the secondary winding of a transformer on the level of losses in it using the method of experiment planning

Purpose. Detection the relationship between the level of losses of a three-phase transformer and the power of distortion caused by current harmonics.. Methodology. During the research, the methods of determining power losses and additional losses in the elements of the electrical system from higher current and voltage harmonics, the visual programming method, the experiment planning method, and the orthogonal central composite plan method were used. Findings. An analysis of the indicators characterizing voltage and current distortions was carried out, and it was found that these distortions are most fully characterized by the current distortion power and voltage distortion power. These indicators are used to analyze the transmission of electric energy by a transformer of a traction substation. It is noted that the order of harmonics in the distortion power is not eliminated, and higher harmonics are taken into account by the corresponding effective current of higher harmonics. The specifics of the transformer secondary winding connections to the consumer, namely the grounding of one of the secondary winding phases, were taken into account. A number of combinations of current harmonics were used to simulate current distortions. The experiment was carried out using the planning method. The coefficients of the quadratic regression equation that relates power losses to the level of load current harmonics of the third, fifth, and seventh orders are obtaine To determine the significance of the obtained coefficients of the regression equation, the variances and the corresponding values of the Student's criterion were calculated, as a result, factors that do not affect the process and can be excluded from the regression equation were identified. The adequacy of the obtained regression equation was checked by Fisher's criterion. The analysis of the effects and their interaction showed that the standard error of the sample does not exceed 1.66%. As a result of analyzing the combinations of current harmonics that were set during the experiment, it was noted that some of them lead to the same effective phase current, while the power of current distortion is different. The greatest significance of the level of the third harmonic of the current is determined. The constant level of active power on the high voltage side of the transformer is noted, which is due to the absence of voltage distortions on it. Originality. Cases of combinations of current harmonic levels at which the current distortion power index remains unchanged, while the level of transformer power losses caused by current harmonics changes, have been identified. Practical value. This research can be used to assess and reduce the level of power losses in a transformer by filtering certain current harmonics.

Analysis of the Effect of Capacitor Placements at High and Low Voltage Transformer Sides as Voltage Profile and Total Cost in Distribution Systems

This study mentions the problem of determining optimal placements and sizes for capacitor banks by comparing different schemes that allow implemented buses at both high and low voltage side, only high voltage side or low voltage side of transformers in distribution systems. Criterions evaluated for each scheme are active and reactive power losses in whole system, voltage value at all buses, installation and operation cost and accumulative profit saving. Standard with and without transformer branches in distribution systems and Newton-Raphson method are introduced to make clear about the way to analyze power flows in whole system. Optimal placements and sizes for capacitor banks are determined by using a proposed algorithm and optimal capacitor placement tool in ETAP software. Simulation results can help to show the comparisons, evaluations and make decision about optimal capacitor placements and sizes. The contribution shows the best scheme that install capacitors at low voltage side of transformers because it has the lowest implemented capacity, highest economic factors while voltage quality is always in allowable range. Achieved results can be applied in any distribution system, help managers have overall review and decide optimal placements and sizes for capacitor banks. Keywords: Capacitor bank, OCP Tool, ETAP software, Optimal placement, Optimal size, Voltage quality, Optimal cost.

Optical Electric Current Transformer for Monitoring Its Performance in the Substation

The optical electric current transformer (OECT) is an important measuring and protection equipment in the power system. Its accuracy and reliability are vital to the power system’s safe, reliable, and economical operation. Because the energy supply of a high-voltage side data acquisition system is the biggest obstacle in developing this kind of transformer, a low-power data acquisition system of OECT is designed from cost, reliability, accuracy, and practicability. In the design process, the low-power microcontroller MSP430 produced by TI company is used for control. Its rich on-chip and off-chip function modules and ultra-low power performance meet the system’s requirements. The 16-bit low-power high-speed chip ADS8325 is used as an A/D converter to ensure the instantaneity and accuracy of data acquisition and the low-power characteristics of the system. The optical fiber digital transmission system is utilized to achieve high/low voltage electrical isolation, and the low-power optical fiber transmission drive circuit is devised. After the main hardware design is completed, the software is adjusted and used in the electric energy monitoring of the substation. The test shows that the error of three-phase current and three-phase voltage is less than 2%. After setting the voltage amplitude, current amplitude, and power factor, the error of its active and reactive power is less than 2% after electric energy monitoring. After multiple harmonic tests, the measurement errors of voltage harmonics and current harmonics are smaller than 5%, that is, the measurement results of each index achieve high measurement accuracy.

A hybrid DC-DC modular multilevel converter with capacitors parallel connectivity for arm energy balancing

The integration of renewable energy sources in Medium-/High-voltage DC grids has called up continuous research to develop DC-DC conversion systems. This paper presents a hybrid modular multilevel DC-DC converter topology which successfully overcomes the issue of capacitors voltage imbalance during DC-DC conversion. In the proposed topology, single MMC leg is employed with half-bridge submodules in the upper arm and full-bridge submodules in the lower arm along with soft-switched high-voltage valves. The proposed hybrid modular multilevel converter has inherited arm energy equalization with the help of the parallel connectivity of involved arms’ capacitors. During the equalization period, the series-connected upper arm capacitors are connected in parallel to the series-connected lower arm capacitors to transfer the energy between the involved arms which results in operating with balanced capacitors voltages. The proposed modular DC-DC converter is a bidirectional converter which allows power flow from high-voltage side to low-voltage side and vice versa, i.e., it can be operated successfully as a DC transformer. The operational concept of the proposed configuration, control strategy, and parameters design are presented. Simulation results are presented along with experimental results of a scaled-down prototype to validate the proposed approach. Simulation and experimental results show the viability of the suggested approach.

Transformerless bidirectional switched-inductor switched-capacitor converter

ABSTRACT This research presents a unique bidirectional converter based on the active switched-inductor and switched-capacitor networks of the ASL-SU2C converter. The converter’s primary advantages are its high voltage gain and reduced switch stress. This was accomplished by the converter using three inductors, two switched-capacitors, two switches, and diodes. Switches are used in place of diodes to enable bidirectional power flow in the proposed work, and synchronous rectification is used to boost efficiency by reducing conduction losses. Two inductors and two switches on the low voltage side of the converter aid in lowering the average switch current and, consequently, the current stress. The control operation is made simpler by the fact that two switches on the high voltage side (HVS) have one duty cycle and the other two switches on the low voltage side (LVS) have a different duty cycle. Consequently, two switches will always have identical duty cycles. In order to validate the theoretical findings, the performance of the transformerless bidirectional switched-inductor switched-capacitor (TBSISC) topology is examined in steady state, compared to that of other bidirectional converters, its efficiency is calculated, and experiments with a 500 W prototype are conducted.

Improving and warning the static stability limit of complex power grid tie-line based on WAMS

In order to solve the technical problems of traditional power system classic formulas that are difficult to explain the static stability limit changes of power grid interconnection lines, as well as the difficulties in improving and warning the static stability limit power of interconnection lines, this paper provides a method for improving and warning the static stability limit of power grid interconnection lines. Firstly, based on the electrical quantities measured by the wide-area measurement system (WAMS) of the power grid, the equivalent reactance of the power grid interconnection lines, and the equivalent impedance from the high voltage side and medium voltage side of the three coil transformers on both sides of the interconnection line are determined. Secondly, under pre-set operation mode and constraint conditions, the configuration quantity and capacity of the dynamic reactive power sources on the medium voltage side of the three coil transformers on both sides of the interconnection line are determined. Finally, based on the determined configuration and pre-set operation mode of the dynamic reactive power sources on the medium voltage side of the three coil transformers on both sides of the interconnection line, the historical electrical quantities measured by WAMS. The static stability limit and static stability margin of the interconnection line are calculated, and warnings are provided.

Research on Non-destructive Testing Method for Aging of Sheds of Composite Insulators

As an important part of external insulation of transmission and distribution lines and substation equipment, silicone rubber insulators are generally used because of their strong anti-pollution flashover ability, excellent hydrophobicity, and lightweight. It is one of the effective means to obtain the aging degree of sheds quickly and accurately to prevent operation accidents. From the micro and macro perspectives, firstly, this paper uses the traditional scanning electron microscopy and dielectric loss factor test to classify the aging degree of 11 high-voltage side sheds samples of silicone rubber insulators running on-site for 0~11 years. According to the different experimental principles, the aging degree of each experimental method is divided into four grades. Then, the detection method based on terahertz time-domain spectroscopy is proposed to realize a nondestructive evaluation of the aging grades of sheds of silicone rubber insulators. Finally, through comparison, it can be found that the THz absorption coefficient spectra can find the characteristic quantity of classification of aging levels of silicone rubber materials: The aging levels of the silicone rubber samples increase, and the absorption peak at 1.32 THz in the absorption spectra show a downward trend. According to the characteristic quantity, 11 samples can also be divided into four aging grades, and the results are consistent with the previous experiments.

DC Impedance Modeling of Push-Pull DC Auto-Transformer for MMC and LCC HVDC Interconnections

The push-pull DC autotransformer (PPDAT) is a potential power equipment to interconnect the MMC and LCC HVDC systems. However, the harmonic stability of the PPDAT remains an unsolved challenge. In this paper, considering the dual closed-loop control and bidirectional DC voltage operation of the PPDAT, its DC impedance models are proposed using the harmonic transfer function (HTF) method. Both the DC impedance models at the high/low voltage side considering the harmonic coupling and internal dynamics of the hybrid MMC/LCC HVDC system are deduced. The accuracy of the detailed DC impedance models is validated in PSCAD/EMTDC simulations. The impedance analysis under bidirectional DC voltage operation scenarios reveals that the DC voltage polarity affects the low frequency region. Besides, the main impact of PPDAT's parameters on the wideband impedance characteristics is disclosed. It shows that unreasonable parameter design will bring negative damping characteristics near the resonance point (RP). Moreover, stability analysis considering the interaction of PPDAT and LCC-HVDC at the high-voltage side is conducted. The results indicate that the potential resonances can be readily predicted through the Nyquist diagrams and the negative damping of the PPDAT may cause instability at RP.