Auxiliary Voltage Research Articles

Energy distribution of electron flux at electrodes in a low pressure capacitively coupled plasma

A one-dimensional particle-in-cell (PIC) model is used to examine the energy distribution of electron flux at electrodes [labeled ge(ε,t), where ε is energy and t is time] in a low pressure 60 MHz capacitively coupled Ar discharge. The effect of gas pressure and an auxiliary DC voltage on ge(ε,t) is also investigated. It is found that the electrons only leave the plasma for a short time period during the radio-frequency (RF) cycle when the sheath collapses at the electrode. Furthermore, majority of the exiting electrons have energies below 10 eV with a distribution ge(ε,t) that is narrow in both energy and time. At relatively high pressures (≥4.67 Pa for the conditions considered), the relationship between the time-average distribution ge(ε) and electron temperature in the plasma (Te) can be easily established. Below 4.67 Pa, kinetic effects become important, making it difficult to interpret ge(ε) in terms of Te. At low pressures, ge(ε,t) is found to broaden in both energy and time except for a narrow pressure range around 1.2 Pa where the distribution narrows temporally. These low pressure kinetic phenomena are observed when the electrons can be accelerated by expanding sheaths to speeds that allow them to traverse the inter-electrode distance quickly (<1.5 RF cycles for conditions considered) and when electrons undergo few collisions during this excursion. The mean energy of exiting electrons increases with decreasing gas pressure, especially below 1.0 Pa, due to higher Te and secondary electrons retaining a larger fraction of the energy they gained during initial sheath acceleration. For the relatively small DC voltages examined (|Vdc|/Vrf ≤ 0.15), the application of a negative DC voltage on an electrode decreases the electron flux there but has a weak impact on the ge profile.

A Primary-Side Control Scheme for High-Power-Factor LED Driver With TRIAC Dimming Capability

This paper proposes a primary-side control scheme for low-power light-emitting diode (LED) driver with Flyback topology. With average primary-side current signal and transformer auxiliary winding voltage signal, the output current can be derived and regulated precisely by the proposed control scheme without any isolated feedback circuit. Furthermore, the proposed primary-side control scheme can be implemented with power factor correction control to achieve high input power factor, which is usually required for LED drivers. Since the triode for alternating current (TRIAC) dimming is very popular in practical application, it is preferred that the LED driver can also be compatible with TRIAC dimming. With the proposed control scheme, the input characteristic of the LED driver is resistive like an incandescent bulb. No extra dummy load is needed to provide the TRIAC holding current. Both the output current signal and TRIAC dimming signal can be obtained at the primary side, the TRIAC dimming function can be easily implemented and linear dimming characteristic can be achieved. Detailed operation principles and design considerations of the proposed control scheme are presented in the paper. The experimental results from a 15-W prototype verify the theoretical analysis.

TRIAC을 이용한 커패시터 운전형 단상 유도전동기의 속도제어 특성

This paper presents speed control characteristics of capacitor-run SPIM(Single Phase Induction Motor) using TRIAC for comparing and analyzing four kinds of voltage control methods such as supply voltage control, main winding voltage control, auxiliary winding voltage control and auxiliary winding voltage control without starting capacitor. The computer simulations were performed using MATLAB Simulink to show control characteristics of four voltage control methods. And their control characteristics were conformed by experiments for capacitor-run 90W SPIM as a sample motor. The results of simulations and experiments show that supply voltage control method has fast dynamic response characteristics and main winding voltage control method has higher power efficiency and can be implemented at lower system cost.

Compensation of CVT Increased Error and Its Impacts on Distance Relays

Increased ratio error of capacitor voltage transformers (CVTs) has been recently encountered in several substations in Iran. The results of the performed diagnostic tests indicate that short-circuited capacitor elements, especially in the low-voltage capacitor, have increased the CVT error. In this paper, some simple and effective techniques are suggested to solve this problem. One of the proposed methods to compensate the increased error is utilization of an auxiliary voltage transformer (AVT), which does not require disassembling the CVT. The practical aspects of this method, its effects on the CVT transient response, and the influence of the AVT improper design on the performance of distance relay are scrutinized in this paper. Furthermore, the design requirements of the AVT to avoid distance relay malfunctions due to the AVT ferroresonance are discussed.

Method to Determine the Ratio Error of DC High-Voltage Dividers

This paper introduces a method called the “dc voltage summation method” for determining the ratio change of dc high-voltage dividers with the applied voltage. Two auxiliary voltage dividers with the same rated voltage U were used to calibrate the voltage divider with rated voltage 2U. Experimental results showed that the measurement uncertainty of the method can achieve 1 mV/kV at an applied voltage of 100 kV. The ratio change of dc high-voltage dividers caused by the parameter changes of the resistors with applied voltage can be evaluated more accurately when compared to other existing methods. In conjunction with leakage current measurement, this method can be used to provide traceability of dc voltage dividers above 500 kV.

CCVT Failure due to Improper Design of Auxiliary Voltage Transformers

In-situ tests of coupling capacitor voltage transformers (CCVTs) in some of the high-voltage substations indicate that the ratio error of a considerable number of CCVTs has increased to more than 5%. Experimental analyses reveal that the CCVTs excessive ratio error is mainly due to the short-circuited capacitor elements of CCVTs. Comprehensive tests and investigations indicate that the occurrence of ferroresonance due to saturation of the auxiliary voltage transformers (AVTs) is one of the main reasons for this problem. These small transformers are usually utilized inside the protective relays and control and measuring equipment or are connected to the secondary side of CCVTs as an interface between the CCVT and the equipment. Imposed stress on CCVT components and the voltage oscillations' effect on transmission-line distance relay are also scrutinized in this paper. Finally, appropriate specifications for AVTs are recommended to prevent undesirable CCVT overvoltages and distance relay maloperation.

Simplified multilevel space vector pulse-width modulation scheme based on two-level space vector pulse-width modulation

A novel simplified multilevel space vector pulse-width modulation (SVM) scheme is proposed based on the two-level SVM. The voltage vectors with same amplitude and phase angle are applied to the various power units of cascaded multilevel inverter (CMLI), and the refresh times of various vectors are delayed in order, thus the corresponding multilevel output voltage waveform is formatted. During every sampling period, only the on-times of main and auxiliary voltage vectors of one-stage unit are calculated based on a two-level SVM algorithm, so the computational complexity is independent on the unit-cascaded number. Then the algorithm is simplified, and the expandability is enhanced. The simulation and experimental results prove the validity and feasibility of the novel scheme.

Effect of Voltage Supply Mode on Electrolytic Machining of Polycrystalline Silicon

Wire electric discharge machining (WEDM) of polycrystalline silicon (polysilicon) involves high-temperature melting that easily produces cracks on the wafer surface. This study explored the removal of surface defects by electrolytic machining (EM) to enhance surface quality. EM of polysilicon was conducted under different voltage supply modes, namely, DC voltage (DC-V), pulse voltage (Pulse-V), and auxiliary pulse voltage (Auxiliary-P-V) to examine their effects on material removal (MR) and surface roughness (SR). Results show that poor surface quality was achieved by EM with DC-V mode due to accumulation of bubbles between electrode gaps and inefficient MR. In contrast, EM with Pulse-V supply can reduce SR by proper control of pulse voltage cycle through adjustment in pulse-on and pulse-off time to ensure good replenishment of electrolyte. Finally, adding an optimal auxiliary voltage to the pulse cycle contributes to EM stability. Hence, EM with Auxiliary-P-V supply is an effective approach to electrolytic machining of WEDMed polysilicon. Not only is high MR achieved, but good surface quality is also maintained.

Investigation on Switching Patterns of Direct Power Control Strategies for Grid-Connected DC–AC Converters Based on Power Variation Rates

This paper investigates the switching patterns of direct power control (DPC) strategies for three-phase grid-connected voltage-sourced dc–ac converters. The instantaneous variation rates of active and reactive powers by applying each converter voltage vector in 12 different sectors are deduced. In terms of hysteresis look-up-table DPC, based on the power variation rates, modified switching tables are presented to alleviate the active power pulsations, and an asymmetrical hysteresis controller is proposed for active power control to eliminate its steady-state errors. As to predictive DPC, according to the power variation rates, the cause is identified to that the values of the predicted duration times for the auxiliary active voltage vector become negative. Consequently, to solve this problem, two new alternative vector sequences are proposed and compared. A simple compensation method is further added to the basic control scheme of predictive DPC to deal with grid voltage unbalances. Experimental results on a 1.5-kVA grid-connected dc–ac converter are presented to validate the feasibility of the improved switching patterns and the unbalanced compensation method on the DPC strategies for dc–ac converters.

Liquid-based electrostatic energy harvester with high sensitivity to human physicalmotion

This paper presents a new liquid-based electrostatic energy harvester that converts themechanical energy of human-motion-induced vibrations to electrical energy. The basicdesign uses a conducting liquid to enhance sensitivity to human motion, the frequency ofwhich is typically as low as several hertz; it also uses a hydrophobic coating to provide abroad frequency bandwidth. As liquid slops in accordance with external motions, proposedenergy harvester shows large capacitance variations. The device was tested under variousconditions with periodic and nonperiodic movements. The maximum capacitance obtainedfrom the fabricated device was about 10 nF, whereas the minimum capacitance was 5 pF,resulting in an extremely high capacitance ratio of 2000. The hydrophobic treatmentenables the fabricated device to work well for periodic motions with a frequencyrange of 2–5 Hz. The power generated from a human running motion at a speed of8 km h−1 is theoreticallyestimated to be 35.3 µW with charge-constrained conversion and an auxiliary voltage of 1 V.

Zero-Voltage Switching Postregulation Scheme for Multioutput Forward Converter With Synchronous Switches

A new multioutput forward converter is proposed. It consists of four synchronous switches in the secondary side for two outputs with the same ground. The primary switches control the main output voltage, and the synchronous switches in the transformer secondary side control the auxiliary output voltage. The main advantages of the proposed converter are that the secondary regulation switch for auxiliary output can achieve the zero-voltage switching at the entire load conditions and the secondary rectified voltage is a three-level waveform, which can reduce the output filter. The operational principle, analysis, and design considerations of the proposed converter are presented in this paper. The validity of this study is confirmed by the experimental results from a dual-output (12 V-18.3 A and 5 V-6 A) prototype for personal computer power supply.

Starting scheme for load commutated inverter-fed wound field synchronous machine using an auxiliary low-power voltage source inverter

Conventional thyristor-based load commutated inverter (LCI)-fed wound field synchronous machine operates only above a minimum speed that is necessary to develop enough back emf to ensure commutation. The drive is started and brought up to a speed of around 10–15% by a complex ‘dc link current pulsing’ technique. During this process, the drive have problems such as pulsating torque, insufficient average starting torque, longer starting time, etc. In this regard a simple starting and low-speed operation scheme, by employing an auxiliary low-power voltage source inverter (VSI) between the LCI and the machine terminals, is presented in this study. The drive is started and brought up to a low speed of around 15% using the VSI alone with field oriented control. The complete control is then smoothly and dynamically transferred to the conventional LCI control. After the control transfer, the VSI is turned off and physically disconnected from the main circuit. The advantages of this scheme are smooth starting, complete control of torque and flux at starting and low speeds, less starting time, stable operation, etc. The voltage rating of the required VSI is very low of the order of 10–15%, whereas the current rating is dependent on the starting torque requirement of the load. The experimental results from a 15.8 hp LCI-fed wound field synchronous machine are given to demonstrate the scheme.

Family of zero-voltage transition pulse width modulation converters with low auxiliary switch voltage stress

A new family of zero-voltage transition (ZVT) pulse width modulation (PWM) converters is introduced. In this converter family there is no additional voltage stress on the main switch in comparison to the hard switching counterpart. Also, the voltage and current rating of the auxiliary switch is low. The proposed zero-voltage transition PWM buck converter is analysed and design considerations are discussed. A prototype converter is implemented and the experimental results are presented.

Auxiliary Supply Assisted Harmonic Suppression for 12-Pulse Phase-Controlled Rectifiers

A 12-pulse phase-controlled rectifier consists of two sets of 6-pulse rectifiers. It is found that harmonic distortion of the input current is minimized if dc currents of the two rectifiers are in a boundary between continuous and discontinuous conduction modes. In order to realize the boundary mode operation under any load conditions an auxiliary voltage supply (AVS) is introduced. The AVS is required a bi-directional power flow but its handled net power is quite small. Capacity of AVS is less than 10% of rated rectifier output. A simple AVS arrangement is proposed and the usefulness is verified by simulation and experimental results.

Effects of Auxiliary Electrode Width in AC Plasma Display Panels With Auxiliary Electrodes

We investigated the effects of changing the width of the auxiliary electrode in an ac plasma display panel including centrally located auxiliary electrodes between the sustain electrodes, based on analyses of the discharge mode. A panel with auxiliary electrodes was driven by pulse waveforms that included auxiliary pulses applied to the auxiliary electrode immediately after every sustain pulse. The discharge modes are changed consecutively from mode 1 to mode 3-2 when the sustain or auxiliary pulse voltages are increased, which can be characterized as follows: 1) only the sustain pulse discharges are generated in mode 1; 2) one of a pair of the auxiliary pulse discharges is additionally generated in mode 2; and 3) the other auxiliary pulse discharge is also generated in mode 3-1 and mode 3-2. Distribution of the discharge mode changes in accordance with the width of the auxiliary electrode (the focus is on modes 1 and 2 because these modes are effective modes); as the auxiliary electrode is narrowed, the range of mode 1 becomes wide and the range of mode 2 becomes narrow. The wide range of mode 1 is attributed to the fact that the discharge of the auxiliary pulse is suppressed due to a longer gap between the sustain and auxiliary electrodes. The narrow range of mode 2 is caused by the discharge of the auxiliary pulse less affecting the discharge of the sustain pulse. Since the auxiliary electrode provides less of a decrease in the number of wall charges on the sustain electrodes, the voltage margin is improved for the case of the narrow auxiliary electrode. The luminous efficacy is mostly improved in mode 1 for the case of the narrow auxiliary electrode due to the auxiliary pulse with a higher voltage generating a larger number of space charges, as well as in mode 2 for the case of the wide auxiliary electrode due to a short electrode gap rendering a great number of wall charges decreasing.

Novel zero voltage transition pulse width modulation flyback converter

In this article, a new zero voltage (ZV) transition flyback converter is introduced which uses a simple auxiliary circuit. In this converter, ZV switching condition is achieved for the converter switch while zero current switching condition is attained for the auxiliary switch. There is no additional voltage and current stress on the main switch. Main diode, auxiliary circuit voltage and current ratings are low. The proposed converter is analysed and design procedure is discussed. The presented experimental results of a prototype converter justify the theoretical analysis.

Achievement Of Zvt And Computation Of Its Time Of Occurrence For Power Converters

This paper provides a mathematical expression to determine the occurrence of soft-switching for a general topology of ZVT converters with auxiliary resonant voltage source. This expression is used to help the designer in choosing appropriately the values of inductance and capacitance for the auxiliary resonant branch ensuring ZVT. The main advantage of the proposed methodology is to point out suitable sets of circuit parameters without relying only on time consuming numerical simulations of the entire converter. Additionally, numerical methods to compute the time of occurrence of ZVT for these power converters are provided. The proposed methods are given by second order approximations of a nonlinear function which describes the voltage on the ZVT snubber capacitor during the zero-voltage resonant stage. The results can be seen as applications of second order Taylor series and of quadratic interpolation. However, differently of simply finding the root of a given nonlinear equation, the conditions given here provide analytical expressions to compute the time of occurrence of ZVT based on the converter parameters. Then, the proposed conditions become useful for analysis and design, allowing evaluating operation sequence, total commutation time, resistive losses and other important parameters to describe the converter performance.

Design Criterion For Zczvt Single-phase Inverters With Magnetically-coupled Auxiliary Pole

This paper presents in detail a design methodology for Zero-Current Zero-Voltage Transition inverters with magnetically-coupled auxiliary circuit. These ZCZVT inverters accomplish favorable softswitching conditions with a magnetically coupled auxiliary voltage which is derived directly from the inverter filter inductor. It ensures no resonant auxiliary circuit, reducing circulating reactive energy. The design methodology takes into account the semiconductor requirements to ensure low switching losses on the assisted IGBT modules, which is very important to ensure the best characteristics of the ZCZVT technique. The theoretical analysis is verified experimentally by means of a 1kW, 40 kHz laboratory prototype. The results prove the high efficiency of the prototype implemented according to the proposed design.

Zczvt Inverters With Magnetically Coupled Auxiliary Pole

Existing Zero-Current Transition and Zero- Current Zero-Voltage Transition inverters provides favorable switching conditions for IGBT semiconductors increasing significantly the reactive energy of the converter. This situation off-set the benefits accomplished by abovementioned soft-switching techniques. This paper presents a novel family of Zero-Current Zero-Voltage Transition inverters that overcome this problem by using no resonant tank in the auxiliary circuit. It accomplishes the favorable soft-switching conditions with a magnetically coupled auxiliary voltage source which is derived directly from the inverter filter inductor. Theoretical analysis of the inverter operation is presented and it is verified experimentally from a 1kW, 40kHz, laboratory prototype. The obtained experimental results prove the reliability of the proposed family of ZCZVT inverters.

Flyback-Based Single-Stage Power-Factor-Correction Scheme With Time-Multiplexing Control

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A flyback-based single-stage power-factor-correction scheme with time-multiplexing control (TMC) is proposed. As a portion of the input power will be transferred to the output after the first power processing to improve the conversion efficiency, the output voltage would contain substantial low-frequency ripple. An isolated auxiliary circuit based on forward topology is therefore added to the converter to serve as a buffer and a ripple suppression circuit. With TMC, all the power processes can be achieved by a single transformer to lower the size and cost of the converter. In addition, the proposed converter inherits bulk capacitor (auxiliary) voltage clamping capability. The experimental results confirmed the effectiveness of the proposed scheme with high power factor, natural bulk capacitor (auxiliary) clamping voltage, and tight output regulation. </para>