DC Input Power Research Articles

Three Phase Two Leg Neutral Point Clamped Converter with output DC Voltage Regulation and Input Power Factor Correction

In this paper, a three-phase two leg neutral point clamped (NPC) converter is presented for power factor correction and dc-link voltage regulation. The adopted converter has simpler circuit configuration and less number of power switches compared to three-level PWM converter. In this circuit configuration, only eight power switches and four clamping diodes with voltage stress of half the dc bus voltage are used. A simplified space vector pulse width modulation scheme (SVPWM) is also adopted to track the line current commands. A reference voltage vector is generated on the ac terminal for drawing the sinusoidal line currents with unity power factor. This algorithm reduces the time required to calculate the switching time durations of voltage vectors. The simulation results have been presented to verify the validity and effectiveness of the proposed control strategy. DOI: http://dx.doi.org/10.11591/ijpeds.v2i2.226

Analysis of temporal jitter in a copper vapor laser system

Temporal jitter in a magnetic pulse compression based copper vapor laser (CVL) system is analyzed by considering ripple present in the input dc power supply and ripple present in the magnetic core resetting power supply. It is shown that the jitter is a function of the ratio of operating voltage to the designed voltage, percentage ripple, and the total propagation delay of the magnetic pulse compression circuit. Experimental results from a CVL system operating at a repetition rate of 9 kHz are presented.

Solar Power Conditioners Using Bidirectional Chopper Circuits Connected in Series

This paper proposes a new high-efficiency grid-connection inverter suitable for the interface with thin-film solar cells, which is composed of two bidirectional buck converters and an H-bridge PWM converter connected in series. The switching frequencies of the first bidirectional buck converters are equal to the grid frequency, while the second one is operated at the twice of the grid frequency. The combination of these two converter synthesizes an ac rectangular voltage pulse train from the dc input power. The H-bridge PWM converter is operated at 20kHz with a low dc capacitor voltage to compensate for the harmonic voltage included in the rectangular voltage pulse train. As a result, the proposed grid-connection inverter makes it possible to reduce both switching loss and common mode voltage. Experimental results obtained by a 1-kW single-phase inverter demonstrate a high efficiency of 98% without any common mode voltage.

Performance evaluation of a newly designed DC microplasma for direct organic compound detection through molecular emission spectrometry

A low-power, portable dc microplasma source has been developed for use in molecular emission spectrometry. The device employs a 450 nL plasma chamber in which an atmospheric pressure dc glow discharge is generated with argon gas. The discharge ignites spontaneously when the system is operated at dc input power of 0.95–6.5 W and gas flows of 100–2500 mL min−1. Two sample introduction modes are used to enable direct analysis of gaseous and liquid samples. The detection of volatile organic compounds was achievable via the emissions from CN at 387.15 nm, CH at 431.41 nm and C2 at 516.53 nm. Under the optimized experimental conditions, the limit of detection (LOD) down to ppb (v/v) level can be achieved. These detection limits are competitive to or better than those of other microfabricated plasma devices. More importantly, the effect of organic compound structure on emission response is systematically studied. It was found for the first time that the ratio of C2/CH emission is closely associated with the ratio of hydrogen to carbon atoms (H/C) in a molecule, which might be potentially used for direct semi-qualitative analysis of organics. The dc microplasma detector possesses the advantages of simple construction, high sensitivity, low power consumption, long lifetime, and potential for portability in mass reduction and instrumentation.

Modeling and simulation of a grid connected PV system based on the evaluation of main PV module parameters

In this work we present a new method for the modeling and simulation study of a photovoltaic grid connected system and its experimental validation. This method has been applied in the simulation of a grid connected PV system with a rated power of 3.2 Kw p, composed by a photovoltaic generator and a single phase grid connected inverter. First, a PV module, forming part of the whole PV array is modeled by a single diode lumped circuit and main parameters of the PV module are evaluated. Results obtained for the PV module characteristics have been validated experimentally by carrying out outdoor I– V characteristic measurements. To take into account the power conversion efficiency, the measured AC output power against DC input power is fitted to a second order efficiency model to derive its specific parameters. The simulation results have been performed through Matlab/Simulink environment. Results has shown good agreement with experimental data, whether for the I– V characteristics or for the whole operating system. The significant error indicators are reported in order to show the effectiveness of the simulation model to predict energy generation for such PV system.

A Flyback Rectifier With Spread Harmonic Spectrum

This paper presents a flyback switch-mode rectifier (SMR) with spread harmonic spectrum. The SMR switching control is conducted by a charge-regulated pulsewidth modulation (PWM) scheme with constant turn-on period. The inherently stable discontinuous conduction mode operation is preserved to yield good line drawn power quality. In voltage loop, a quantitatively designed PI feedback controller is augmented with a robust error cancellation control scheme. Further improved dc output voltage regulation and input power quality performances are achieved under varied operating conditions. In spread harmonic spectrum control, the harmonic spectral properties of the developed flyback SMR are first analyzed. Then, the dedicated random switching scheme is developed to let its switch current harmonic spectrum be dispersedly distributed. In the proposed random switching scheme, the PWM turn-off period is modulated using 1-b binary sequence, pseudo random binary sequence, and 4-b binary sequences. Under randomized harmonic spectrum, the SMR control performances are not sacrificed.

Coherent Terahertz Emission of Intrinsic Josephson Junction Stacks in the Hot Spot Regime

We report on THz emission measurements and low temperature scanning laser imaging of ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8}$ intrinsic Josephson junction stacks. Coherent emission is observed at large dc input power, where a hot spot and a standing wave, formed in the ``cold'' part of the stack, coexist. By changing bias current and bath temperature, the emission frequency can be varied by more than 40%; the variation matches the Josephson-frequency variation with voltage. The linewidth of radiation is much smaller than expected from a purely cavity-induced synchronization. Thus, an additional mechanism seems to play a role. Some scenarios, related to the presence of the hot spot, are discussed.

Physical modeling of millimetre wave signal reflection from forward biased PIN diodes

This paper examines the DC power requirements of PIN diodes which, with suitable applied DC bias, have the potential to reflect or to permit transmission of millimetre wave energy through them by the process of inducing a semiconductor plasma layer in the I region. The study is conducted using device level simulation of SOI and bulk PIN diodes and reflection modeling based on the Drude conduction model. We examined five diode lengths (60–140μm) and seven diode thicknesses (4–100μm). Simulation output for the diodes of varying thicknesses was subsequently used in reflection modelling to assess their performance for 100GHz operation.It is shown that substantially high DC input power is required in order to induce near total reflection in SOI PIN diodes at 100GHz. Thinner devices consume less DC power, but reflect less incident radiation for given input power. SOI diodes are shown to have improved carrier confinement compared with bulk diodes.

Cascaded Multilevel Inverter Employing Three-Phase Transformers and Single DC Input

This paper proposes an isolated cascaded multilevel inverter employing low-frequency three-phase transformers and a single DC input power source. The proposed circuit configuration can reduce a number of transformers compared with traditional three-phase multilevel inverters using single-phase transformers. It controls switching phase angles to obtain an optimal switching pattern identified with the fundamental frequency of the output voltage. Owing to this control strategy, harmonic components of the output voltage and switching losses can be diminished considerably. To verify the performance of the proposed approach, we implemented computer-aided simulations and experiments using a prototype.

Electrothermal noise analysis in frequency tuning of nanoresonators

Electrothermal tuning mechanisms for nanoelectromechanical resonators are demonstrated. Voltages induced by oscillation of Al/SiC nanoresonators around 10MHz in a moderate magnetic field are measured using a room-temperature tabletop setup in moderate vacuum. The dynamic range as well as the resonance frequency of the resonator can be reversibly controlled by electrothermal tuning using DC voltage. This paper presents experimental results that demonstrates the effect of the resonance frequency, Q factor and dynamic range during the electrothermal tuning process. As the input DC power increases, Q factor decreases due to the decrease in the resonance frequency, and SNR decreases due to the reduced amplitude and increased noise. This can be explained by thermal relaxation of the resonator structure during the tuning process, and Johnson noise and eddy current effects associated with the magnetomotive transduction.

Magnetostrictive Micro Mirrors for an Optical Switch Matrix.

We have developed a wireless-controlled compact optical switch by siliconmicromachining techniques with DC magnetron sputtering. For the optical switchingoperation, micro mirror is designed as cantilever shape size of 5mm×800μm×50μm.TbDyFe film is sputter-deposited on the upper side of the mirror with the condition as: Argas pressure below 1.2×10-9 torr, DC input power of 180W and heating temperature of up to250°C for the wireless control of each component. Mirrors are actuated by externallyapplied magnetic fields for the micro application. Applied beam path can be changedaccording to the direction and the magnitude of applied magnetic field. Reflectivity changes,M-H curves and X-ray diffractions of sputtered mirrors are measured to determine magneto-optical, magneto-elastic properties with variation in sputtered film thickness. The deflectedangle-magnetic field characteristics of the fabricated mirror are measured.

60-GHz System-on-Package Transmitter Integrating Sub-Harmonic Frequency Amplitude Shift-Keying Modulator

This paper proposes a simple low-temperature co-fired ceramic (LTCC) integrated transmitter using sub-harmonic amplitude shift-keying modulation for 60-GHz wireless communications applications. The transmitter system-on-package (SoP) has been monolithically implemented with a six-layer LTCC block embedding a resonator, modulator, and antenna and two active circuits, including a negative resistance generator and frequency doubler on the block. The transmitter SoP integrating whole millimeter-wave circuitry is as small as 26 times 18 times 0.6 mm3, which needs external interfaces only for supplying dc power and digital input signal. The fabricated transmitter SoP reveals a bit error rate of 10-11 and good eye pattern through a 2.5-m transmission of 800-Mb/s data.

Performance Improvement of a Power Conversion Module by Liquid Micro-Jet Impingement Cooling

Liquid micro-jet array impingement cooling of a power conversion module with 12 power switching devices (six insulated gate bipolar transistors and six diodes) is investigated. The 1200-V/150-A module converts dc input power to variable frequency, variable voltage three-phase ac output to drive a 50HP three-phase induction motor. The silicon devices are attached to a packaging layer [direct bonded copper (DBC)], which in turn is soldered to a metal base plate. DI water micro-jet array impinges on the base plate of the module targeted at the footprint area of the devices. Although the high heat flux cooling capability of liquid impingement is a well-established finding, the impact of its practical implementation in power systems has never been addressed. This paper presents the first one-to-one comparison of liquid micro-jet array impingement cooling (JAIC) with the traditional methods, such as air-cooling over finned heat sink or liquid flow in multi-pass cold plate. Results show that compared to the conventional cooling methods, JAIC can significantly enhance the module output power. If the output power is maintained constant, the device temperature can be reduced drastically by JAIC. Furthermore, jet impingement provides uniform cooling for multiple devices placed over a large area, thereby reducing non-uniformity of temperature among the devices. The reduction in device temperature, both its absolute value and the non-uniformity, implies multi-fold increase in module reliability. The results thus illustrate the importance of efficient thermal management technique for compact and reliable power conversion application

P-26 Estimation of Magnetostrictive Properties of Tb_<0.24>Dy_<0.76>Fe_<2-x>Ni_x Thin Films

In this study, the effects of Ni on the magnetic, mechanical characteristics of the Tb_<0.24>Dy_<0.76>Fe_2 system for wireless micro actuator with the effect of deposited film thickness of TbDyFeNi on silicon substrate were investigated. To examine the properties, Tb_<0.24>Dy_<0.76>Fe_<2-x>Ni_x, (x=0, 0.5, 1.2, 2.0) films were sputter-deposited on the silicon substrate with the condition as: Ar gas pressure of below 1.2×10^<-9> torr, DC input power of 200W and heating temperature of up to 300℃. After the sputter process, magnetization and magnetostriction of each sample were measured. X-ray diffraction studies also carried out to certificate the film structure and thickness of the sputtered film. From the investigation, unique property was used to build a novel wirelessly controlled array type micro actuator. The micro actuators with film thicknesses of 0.1, 0.5, 1, 2μm were fabricated by silicon micromachining with selective DC magnetron sputtering techniques. For the operation, the array type micro thin film actuators with each branch size of and TbDyFeNi was sputtered on the back side of the each branch for the actuation. Each branch was attracted by externally applied magnetic fields up to 0.5T and motion of the branches made transportation movement. As an application result, deflected distances of the actuators to external magnetic fields were observed.

Pulsewidth-Modulated $Z$-Source Neutral-Point-Clamped Inverter

This paper presents the careful integration of a newly proposed Z-source topological concept to the basic neutral-point-clamped (NPC) inverter topology for designing a three-level inverter with both voltage-buck and voltage-boost capabilities. The designed Z-source NPC inverter uses two unique X-shaped inductance-capacitance (LC) impedance networks that are connected between two isolated dc input power sources and its inverter circuitry for boosting its AC output voltage. Through the design of an appropriate pulsewidth-modulation (PWM) algorithm, the two impedance networks can be short-circuited sequentially (without shooting through the inverter full DC link) for implementing the ldquonearest-three-vectorrdquo modulation principle with minimized harmonic distortion and device commutations per half carrier cycle while performing voltage boosting. With only a slight modification to the inverter PWM algorithm and by short-circuiting the two impedance networks simultaneously, the designed NPC inverter, with no requirement for deadtime delay, can also be operated with a completely eliminated common-mode voltage. Implementation wise, a detailed vectorial analysis interestingly shows that the same generic set of carrier-based modulation expressions can be used for controlling the -source two-level inverter and NPC inverter with and without reduced common-mode switching. All findings presented in this paper have been confirmed in simulation and experimentally using an implemented laboratory prototype.

An Improved Power-Added Efficiency 19-dBm Hybrid Envelope Elimination and Restoration Power Amplifier for 802.11g WLAN Applications

A comparison of envelope elimination and restoration (EER) and envelope tracking (ET) is discussed and a "hybrid" wideband EER power amplifier (PA) for the WLAN 802.11g system is proposed. A 60% efficiency (the output envelope signal power/input dc power) DC-20-MHz wideband envelope amplifier is designed for wideband EER and wideband ET (WBET) applications. A design method is developed to optimize the efficiency of the envelope amplifier for a given peak-to-average ratio and average slew rate of the envelope signal. An experimental "hybrid" Class-E EER system shows an overall efficiency (modulated RF output power/envelope amplifier dc input power) of 36% and power-added efficiency (the modulated RF output power/envelope amplifier dc input power plus RF input power) of 28% for a WLAN 802.11g signal at 19-dBm (80 mW) output power at 2.4 GHz. Digital predistortion, time alignment, and memory effect mitigation are implemented. The measured 3% error vector magnitude exceeds the 802.11g specification for 5% for a 54-Mb/s modulation signal

Visualization Study on Boiling of Nitrogen During Quench for Fault Current Limiter Applications

For the development of a 13.2 kV/630 A bifilar winding type high-Tc superconducting fault current limiter (SFCL), a visualization study has been conducted to clarify boiling characteristics during the quench of the high-Tc SFCL. A series of experiments was carried out using a stainless steel strip on a G10 plate as a heating element to simulate the quench state of the high-Tc SFCL. A pulse of DC power input was applied to the strip in saturated and subcooled liquid nitrogen. The magnitude of the heat generation was varied from 10 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> to 170 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and the period of the heat impulse was fixed at approximately 100 ms. Bubble behavior was observed by a high-speed camera through view ports of a cryostat. The boiling phenomena, the temperature rising of the strip and the recovery time were compared for different power densities and liquid nitrogen operating conditions. The bubble suppression was clearly observed with respect to the degree of subcooling

유도전동기 고정자자속 기준제어의 최대효율제어

입력이 최소가 되는 자속의 값을 찾는 유도전동기 고정자자속기준제어의 최대효율제어방법을 제안한다. 제안한 방법에서, 정해진 자속의 값만큼씩 기준자속의 값을 변화시키면서 직류링크에서 측정된 입력의 값이 최소가 되는 기준자속의 값을 찾는다. 또한 철손저항을 고려한 유도전동기의 모델을 이용하여 철손저항을 고려한 토크, 슬립각속도, 비간섭 보상전류식을 사용한다. 시뮬레이션 및 실험결과를 통해서 제안한 방법의 효과를 입증한다.

Effective temperature measurements of AlGaN/GaN-based HEMT under various load lines using micro-Raman technique

We report on contact-free measurement of channel temperature of AlGaN/GaN HEMTs under different operation modes. Micro-Raman spectroscopy was successfully used to measure the temperature of operating HEMT devices with <1 μm spatial resolution. Channel temperatures at various load lines were compared. The effective operating temperatures of AlGaN/GaN HEMTs were accessed from the calibration curve of passively heated AlGaN/GaN structures. A linear increase of junction temperature was observed when DC dissipated power was increased. The temperature of the center of the channel in the HEMT was higher than that near the edge by ∼30 °C at 800 mW DC power. The temperature range of class A operation mode is higher than that of class B operation mode. The operating device reached temperatures as high as 115 °C at 800 mW DC input power.

Exact Expressions of the Orbit-Curvature and Curvature-Radius of the Toroidal/Helical Orbits

Quite recently, a number of multi-beam klystrons (MBK) have been developed experimentally, and at least three different MBK models are already commercially available. Multi-beam klystrons operate at reduced electron-gun voltage, and higher total beam-current than the single-beam designs, thus preventing occasional destructive gun- diode discharges, and increasing the power-efficiency up to ~ 75%. The power-efficiency (measured as the ratio of output microwave power to input DC power) is however still limited, even in MBK, as it is obviously impossible to extract all the microwave energy from a sharply-bunched electron-beam, without having the high space-charge-density of the slowing beam force it into uncontrollable defocusing.