High Voltage Source Research Articles

A High-Voltage Power Source for a Pulse Modulator

A High-Voltage Power Source for a Pulse Modulator

Iterative control method of voltage source converters for various high‐power applications

High-voltage and high-power voltage source converters (VSCs) are usually operated at low switching frequencies to minimise the switching losses. This study presents a new control method suitable for low switching frequencies. It consists of two stages. In the first stage, a simple proportional controller is used to suppress any overvoltage or overcurrent during the transients. Then, after the control variables have settled to steady-state values, the iterative controller is activated to finely adjust the modulation index and firing angle of the converter to fulfil the control objectives. To justify the proposed control method, various control objectives are realised in a 10 MVA VSC system, and the results are validated by PSCAD/EMTDC and hardware-in-the-loop simulation. The results show that state variables converge within a few iterative steps, and the transient response is sufficiently fast. The proposed method is shown to perform better than the conventional PI control for eliminating the power imbalance and DC second harmonics due to the imbalance at the grid voltage.

Triode Electron Gun of the LUE-200 Linear Accelerator, IREN Facility of the Laboratory of Neutron Physics, Joint Institute for Nuclear Research

The electron injector (electron gun (EG)) is a triode system (cathode–control grid–anode with a second grid “wall”) with a grounded anode and an isolated filament shielded cathode supplied with a high-voltage (up to –240 kV) pulse from the thyratron modulator through a pulse transformer. The composition of the main systems is as follows: (1) triode gun, (2) pulse modulator of the gun, (3) pulse transformer, and (4) the equipment of the stand (high-voltage pulsed charging modulator, synchronizer with startup system, DC sources, vacuum equipment, power systems of control and monitoring, and focusing system). The triode gun is an electron injector with a heated oxide-barium cathode and a controlled startup on the grid of the cathode–grid node from the GS-34 microwave tube. The modulator consists of PFN of 380 pF capacitors with a total capacity of 12 nF with inductors of 0.66 µH composing a double forming line. The PFN charging is supplied from the high voltage source of TDK Lambda. Starting the grid with an adjustable delay to adjust the pulse duration from 40 to 400 ns of the beam injected from the cathode is done from the starting pulse of the cathode node from the first channel of the synchronizer. The thyratron modulator is launched from the second channel. As a result of adjustment, a beam with a current pulse of 5 A at focusing current 3.1 A of ML1 focusing solenoid at voltage 200–220 kV with a beam with a diameter of 5 mm at a frequency of 25 Hz is obtained. To switch to a frequency of 50 Hz, the current of the focusing solenoid is reduced to 1.5 A. In this case, the beam diameter increases to 1 cm. A stable mode of operation of the electron source is recorded for several tens of shifts.

Time-resolved X-ray reciprocal space mapping of a crystal in an external electric field

A reciprocal space mapping technique with the use of triple-crystal time-resolved X-ray diffractometry has been developed and implemented using a laboratory X-ray source for the first time. This technique allows studying fast processes that occur in a sample under external influences that cause reversible deformations of its crystal lattice. It also allows distinguishing these processes in time and distinguishing different types of crystal deformations caused by these actions. The essence of the technique is to measure time dependences of the intensity for each point of the reciprocal space in the vicinity of the diffraction maximum in three-axis diffraction geometry by subjecting the sample to repeated and structurally identical action of a strong electric field, with the subsequent construction of the time evolution of the two-dimensional reciprocal space map. The time resolution is achieved with the use of a high-speed multichannel intensity analyzer synchronized with a high-voltage source. The results of measuring the reciprocal space maps with a laboratory radiation source with a time resolution of up to 10 ms are demonstrated for a piezoelectric crystal of lanthanum gallium silicate subjected to an external electric field with the field strength 3.08 kV mm−1, which is close to the sample breakdown value.

A High-Voltage Switching Power Supply for Cold Plasma Jets

The parameters of a number of high-voltage solid-state switches are studied. Based on the analysis of their work, a high-voltage pulse source with a size of 105 × 260 × 180 mm is assembled to supply cold plasma jets operating at the ac voltage of 220 V, 50 Hz.

Exploring a new ammeter traceability route for ionisation chamber measurements.

We compared the performance of a commercial ammeter and a home-made integrating electrometer in reading ionisation chamber currents less than 100 pA. The integrating electrometer charges a capacitor with the unknown current and measures the resulting rate of change of voltage, whereas the ammeter uses a high-value resistor as the feedback element to an amplifier which converts current to voltage. The noise performance of both systems was very similar for averaging times less than 1000 s. Both systems were calibrated using a reference current source with 1 part per million (ppm) accuracy, revealing an error of 460 ppm in the electrometer indicated current, of unknown origin. This error is well within the uncertainty budget for radionuclide calibrations but much larger than the individual uncertainties in the traceable calibrations of capacitance, voltage, and time. The noise in the ionisation chamber current was much larger than the noise floor of both instruments, with tests providing strong indication that the excess noise originated in the high voltage source used for energising the chamber.

Studies on Ejection of Cell Culture Medium by Electrohydrodynamic Method

Sample deposition based on micro-droplet ejection has broad application prospects in the field of biomedicine. Ejection of RPMI-1640 medium (without and with cells) is investigated experimentally using a home-build electrohydrodynamic (EHD) ejection system, consisting of a liquid supplier and a nozzle, a high voltage source, a droplet collector, and a high speed photography module. Electric voltage is applied between the nozzle and the droplet collector. The liquid surface is charged and the ejection takes place when electric force overcomes the surface tension. The ejection process is studied by using high speed photography and image processing. At low voltage, a uniform ejection state is established with ejection frequency typically less than 50Hertz. At sufficiently high voltage, another uniform ejection state is reached with ejection frequency as high as 1300Hz. Human peripheral blood mononuclear cells, after ejection, show survival rates higher than 79%, manifesting EHD ejection as a promising technique for cell printing.

Evaluation of Photoelectric Characteristics of a Volume DBD Excited by Power Density Modulation

Photoelectric characteristics are an important reference for high-voltage discharges and are closely related to the excited mode of the high-voltage source. In this paper, we built a large-scale volume dielectric barrier discharge (DBD) system, which is composed of multilayer parallel-plate DBD electrodes and is excited by a high-voltage source in the power density modulation (PDM) mode. Subsequently, we analyzed the applied energy equation and evaluated the DBD systems photoelectric characteristics. The results show that the energy values of different applied voltage cycles during a PDM period exhibit significant differences. However, the average energy in a PDM period is approximately constant. Moreover, the equivalent capacitance of the DBD cell is a function of both the applied voltage and energy density. For the DBD cell, with the increase in both the applied voltage and energy loaded on the DBD cell, the total equivalent capacitance (C) is approximately constant, the dielectric capacitance (C d ) increases exponentially and decreases linearly, while the discharge gap capacitance (C g ) decreases and increases in the same cases. In addition, the relative intensities of the discharge emission increase and the energy efficiency ratios of the relative photoquantum yield of active species decline with the increase in both the applied voltage and energy density loaded on the DBD cell. The experimental results have been analyzed by evaluating the influence of the electrical parameters, and the underlying physical principles have been discussed. This paper clearly demonstrates that the photoelectric characteristics of the DBD reactor are significantly influenced by both the applied voltage and energy density, thus providing helpful insights into the energy evaluation and application of high-voltage discharges.

Высоковольтный импульсный источник для питания холодных плазменных струй

AbstractThe parameters of a number of high-voltage solid-state switches are studied. Based on the analysis of their work, a high-voltage pulse source with a size of 105 × 260 × 180 mm is assembled to supply cold plasma jets operating at the ac voltage of 220 V, 50 Hz.

Nano-Transformations in the Surface Layer of Materials Under Combined Processing by Unbound Granules

The article considers nano-transformations of the surface layer, occurring in combined dimensional finishing with an electric field applied by a tool in the form of unbound metal granules. The object of study are geometrically-complex parts, used in aviation, rocket and space engineering, as well as in oil-and-gas industry, namely, rotors and flow parts of turbopump unit casings, screw conveyers and impellers with sections of various curvature, providing limited access of the tool to the processing zone. It is shown that the combined process involving the fusion of two-component processing media, composed from current-carrying granules, and an electrically conductive liquid medium, supplied to the processing zone at high speed, helps to achieve the required quality of the surface layer. The action of the electric field from a high-voltage source makes it possible to achieve the required peening against the strikes of solid granules in the process of dimensional finishing. This gives the possibility to increase the service life and durability of critical units of aerospace and oil-and-gas equipment, and broaden the scope of using combined processing by unbound granules, as to comprise the components with sections, inaccessible for processing by a profiled electrode.

Design of Integrated Polarizer to Evaluate Quality of Cooking Oil Based on the Fluorescence Polarization Method

An integrated polarizer was designed as an alternative test tool to evaluate quality of cooking oils. Integrated Polarizer was composed of light source with wavelength of 532 ± 10 nm, polarizer, analyser, cuvette, electrodes, and high voltage source. In this research, the tool works based on the fluorescence polarization method. Measurements were made by observing the fluorescence polarization angle changes that occur and by applying an external electric field at the samples using high voltage of 0-9 kV in the parallel plate. The results show that the expired cooking oil has a greater polarization angle than the edible cooking oil. The results also show that the change in the polarization angle will increase in proportion to the increase of the heating time. The condition of saturated fatty acids in each sample has an effect on the change of polarization angle.

Efficient base driver circuit for silicon carbide bipolar junction transistors

The silicon carbide bipolar junction transistor needs large transient currents supplied into and out of its base terminal for rapid switching. To realise this, it is normally desirable to have a base driver circuit supply rail at a high voltage. However, the device also needs a steady base current to hold it in the on-state. Supplying this current from a high-voltage source is inefficient. A circuit is presented that applies high transient base-emitter voltages, but with low driver circuit power consumption.

Development of a High-Voltage Pulsed Power Source for CR Kickers within the FAIR Project

The Collector Ring (CR) is included in the Russian proposal for the Facility for Antiproton and Ion Research (FAIR) project (Fig. 1) and is one of main devices of FAIR [1].

Pulsed High-Voltage Inflector Power Supply of NICA Booster Injection System

Separate systems and devices for the future accelerator complex are developed in the framework of the NICA project. The multivariant injection scheme with five pulsed power supply sources of the inflector plates will be applied for the Nuclotron Booster. The startup variant includes one source with the largest maximum voltage equal to 62 kV. This study presents the pulsed power-supply source of the inflector plates for the Nuclotron Booster injection system. The equipment and the high voltage source control system are described and the results of testing with equivalent load are given.

Development of the ñonverter structure that enables power supply to traction induction motors of mine electric locomotives from different levels of voltage

We have proposed an adjustable structure of the converter of energy of electric drive in the electrotechnical complex of a mine electric locomotive from power sources with different voltage levels ‒ from a contact network and a battery of traction accumulators. A characteristic feature of the converter is the presence of inverter units that can be connected either sequentially or in parallel. When powered by a low­voltage source, inverter units are connected in parallel over the entire range of change in the output voltage. When powered by a high voltage source, inverter units are connected sequentially in the range of low output voltages and in parallel in the range of high output voltages. Such an approach makes it possible to align the power voltage levels of traction asynchronous motors of a mine electric locomotive at a lower level. The expected alignment of voltage levels is carried out at a lower level compared to a standard circuit of the three­phase bridge autonomous inverter and is achieved by controlling the paired bridges in the power circuit of traction induction motors. Given this, the frequency of voltages of width­pulse modulation does not change, which is important for the process of reducing dynamic losses of power in the drive’s elements. It has been confirmed that an increase in the output voltage distortion coefficient in the IGB­transistors of the inverter with the minimal level of energy losses in the electric drive’s elements is achieved by modulating the voltage at a constant switching frequency at different voltage levels. We have proven the fact that the best indicators for the harmonic coefficient were obtained at frequencies about 30 Hz, which are the working ones, so the converter operating mode is most effective at these frequencies. The result of analysis of the classical scheme of the inverter has revealed that increasing the frequency of pulse­width modulation by three times significantly increases electrical losses in the windings of traction electric motor. In the proposed circuit of the voltage inverter of engine’s power, at leveling the voltage at low level, there is no need to increase the frequency of pulse­width modulation, which does not lead to a growth in the electrical losses in a traction motor

Electrical analysis of triboelectric nanogenerator for high voltage applications exampled by DBD microplasma

Triboelectric nanogenerator (TENG) is a natural high voltage and low frequency power source by transferring ambient motion into electrical energy. To improve the output performance of the rotary freestanding TENG (RF-TENG) with the capacitive impedance load used in high voltage field, where the dielectric barrier discharge (DBD) microplasma as an example, an efficiently and effectively electrical analysis for the whole system is explored. Firstly, a simply experimental method with 99% reliability shows the root mean square (RMS) of open-circuit voltage in our RF-TENG is around 3500-4000V and the internal capacitance is 100–130 pF with frequency from 10 Hz to 30 Hz. Then, the experiments of DBD microplasma directly driven by the RF-TENG under different conditions have been conducted and the results fit well with the simulation in discharge current and voltage. Moreover, a 10–30 folds jumping of the discharge current and real-time power have been observed. Finally, by increasing the input frequency or decreasing gas thickness, the discharge intensity and efficiency have been enhanced, meanwhile over 10 times increase on discharge power (RMS) has been achieved. This work will not only help to understand the characteristics of the microplasma at low frequency (<50 Hz) but also benefit the further researches on the directly high voltage application of the RF-TENG.

Research on novel hybrid multilevel inverter with cascaded H‐bridges at alternating current side for high‐voltage direct current transmission

A novel hybrid multilevel inverter based on a low-frequency three-level neutral-point-clamped converter and high-frequency cascaded H-bridge converters for high-voltage direct current transmission is presented. This structure can make full use of traditional silicon-based power devices and a new generation of silicon-carbide-based power devices to fabricate a high-voltage voltage source inverter. The topology can reduce the volume and number of power switches as compared with a modular multilevel converter. Finally, the modulation and control strategies are presented, which are verified by a full-scale simulation system and a small-scale experimental platform.

Effects of coaxial dielectric barrier discharge on water treatment at different sites of Kathmandu Valley, Nepal

The research work reports the results concerning the effects of ozone produced by dielectric barrier discharge (DBD) in well, river and industrial wastewater. The dielectric barrier discharge (DBD) unit was developed to produce highly oxidizing ozone molecules, hydrogen peroxide and hydroxyl radicals for the treatment of water. The discharge was produced by applying AC high voltage (up to 10 kV peak-to-peaks) source of frequency 26 kHz across annular electrodes. The well and wastewater samples were collected from 5 different places of Kathmandu district, Nepal. Various physical, chemical and micro-biological parameters such as pH, Electrical Conductivity (EC), Dissolved Oxygen (DO), Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD) and Total Coliform were analysed before and after ozonation. Our results showed that pH of water after treatment changed slightly with respect to pH of untreated water. There was slight change in conductivity of water from the different sources after treatment by ozone. DO of all samples increased significantly after ozonation. It was found that BOD and COD of all samples decreased significantly after ozonation. Concentration of ferrous ion (Fe2+) decreased after ozonation. There was significant decrease in Total Coliform after treatment.

Electrical control of electrostatic precipitation

Considering electrical control of electrostatic precipitation, this paper discusses particle collection in terms of corona ionic wind, gas flow pattern and high-voltage power sources. Experiments and simulations were conducted with lab-scale and industrial electrostatic precipitators. In general, a larger electrostatic precipitator (ESP) index value leads to better ESP performance. To maintain the voltage, simulation results show that a three-phase power source could operate at a lower ripple factor of 0.8% and a shorter recovery time of 5 ms after spark-over than single-phase or high frequency transformer rectifiers. For an industrial ESP with several electric fields, optimal voltage or electric field strength drops from its inlet to outlet fields. It is normally around 3.3 kV cm−1 with a large corona input power for the inlet field, and it drops to about 2.3 kV cm−1 with a small input power to limit ionic wind induced reentrainment for the last field. For a typical Chinese 660 MW coal-fired boiler with a four-field colder-side ESP, its outlet ash concentration and its PM10 and PM2.5 are usually around 15 mg m−3, 12 mg m−3 and 2 mg m−3, respectively. According to particle image velocimetry observation and particle collection measurements, we found that the corona wind generated vortex can result in not only enhancement of collection but also particle reentrainment and/or the so-called ‘bypass flow’. An optimum electric field inside the ESP exists to save energy and collect particles. For present ESPs, a higher electric field (>3.5 kV cm−1) generates strong electrohydrodynamic flow, which consequently undermines the collection due to turbulent flow. Advanced industrial automatic voltage controllers for three-phase transformer rectifier and double-wire ESPs have been developed according to those experimental results for both reducing emission and corona energy consumption.

Loss Optimization of MMC by Second-Order Harmonic Circulating Current Injection

For high power voltage source converter based high voltage direct current transmission systems, modular multilevel converter (MMC) is the most popular circuit topology nowadays. It is known that the existence of the second-order harmonic circulating current (SHCC) component in the arm current of MMC increases the loss of the converter. Conventionally, the SHCC component eliminating methods are usually adopted to reduce the loss. The relationship between the loss of MMC and the SHCC component is analyzed first in this paper. The analysis shows that the conventional eliminating methods are not optimal in terms of the minimum loss of MMC. A loss optimization control scheme is also proposed by injecting the optimal SHCC component into the arm current of MMC, rather than eliminating the SHCC component of the arm current. The simulation and experimental results of the ±350 kV/1000 MW MMC and the down-scaled MMC setup verify the correctness and effectiveness of the proposed loss optimization method under different operation conditions.