Unipolar Inverter Research Articles

Suppression of zero-crossing distortion for single-phase grid-connected photovoltaic inverters with unipolar modulation

For single-phase grid-connected photovoltaic inverters, current-control with unipolar modulation can reduce the losses of power tubes and improve the efficiency compared with using the bipolar modulation. However, it suffers inherent zero-crossing distortion which is related to the grid current and voltage. In this paper, the reason for zero-crossing distortion is analyzed and simulated, also a novel current-control approach with commutating in advance is proposed to resolve this problem. This approach obtains a leading angle of the grid current by using the feedback of proportional-integral controller of the unipolar inverter, and then set the working mode of power tubes according to this angle through commutation.

Be-Doped ZnO Thin-Film Transistors and Circuits Fabricated by Spray Pyrolysis in Air

We report the fabrication of zinc oxide (ZnO) thin-film transistors (TFTs) and simple integrated circuits by spray pyrolysis, and examine the role of beryllium (Be) as the chemical dopant. Doping is achieved through addition of Be-acetylacetonate into the parent Zn-acetate precursor solution followed by film deposition through spray pyrolysis. The microstructural properties of as-grown Be-ZnO films with different dopant concentrations are investigated using a combination of atomic force microscopy and x-ray diffraction techniques, which show the formation of polycrystalline films. Introduction of Be is found to impact the degree of crystallinity of ZnO films where a dramatic decrease in the average grain size is observed with increasing Be concentration. To assess the effects of Be-doping on the electrical properties of ZnO films we have fabricated Be-ZnO based TFTs using different doping concentrations. The average electron mobility calculated from these transistors is on the order of ~ 2 cm2·V-1·s-1 with the threshold voltage (VTH) exhibiting a strong dependence on Be concentration. The ability to control VTH through the introduction of Be has been exploited for the fabrication of unipolar inverters with symmetric trip-voltages and good noise margins.

A low voltage programmable unipolar inverter with a gold nanoparticle monolayer on plastic

A programmable low voltage unipolar inverter with saturated-load configuration has been demonstrated on a plastic substrate. A self-assembled monolayer of gold (Au) nanoparticles was inserted into the dielectric layer acting as a charge trapping layer. The inverter operated well with supply voltages of < − 5 V and the switching voltage was tuned in a wide range under low program/erase bias. The retention and endurance test at ambient conditions confirmed the reliability of the inverter. Furthermore, the programmable behavior was maintained well at various bending states, demonstrating the adequate flexibility of our devices.

Controllable threshold voltage shifts of polymer transistors and inverters by utilizing gold nanoparticles

We have demonstrated controllable threshold voltage (Vth) shifts of gold nanoparticles (Au NPs)/poly (3-hexylthiophene) (P3HT) based composite transistors that are fabricated through a low temperature facile technique. By varying the doping concentration of gold nanoparticles in P3HT matrix, Vth has been tuned from 12 V to 27 V without device degradation. Using this technique, the switching voltages of unipolar inverters have also been systematically tuned. Efficient hole conduction and a variation in P3HT crystallinity was observed due to different concentrations of Au NPs which eventually shift the threshold voltage of the devices in a controlled manner.

Tuning the threshold voltage in electrolyte-gated organic field-effect transistors

Low-voltage organic field-effect transistors (OFETs) promise for low power consumption logic circuits. To enhance the efficiency of the logic circuits, the control of the threshold voltage of the transistors are based on is crucial. We report the systematic control of the threshold voltage of electrolyte-gated OFETs by using various gate metals. The influence of the work function of the metal is investigated in metal-electrolyte-organic semiconductor diodes and electrolyte-gated OFETs. A good correlation is found between the flat-band potential and the threshold voltage. The possibility to tune the threshold voltage over half the potential range applied and to obtain depletion-like (positive threshold voltage) and enhancement (negative threshold voltage) transistors is of great interest when integrating these transistors in logic circuits. The combination of a depletion-like and enhancement transistor leads to a clear improvement of the noise margins in depleted-load unipolar inverters.

Fixed Switching Frequency Sliding Mode Control for Single-Phase Unipolar Inverters

Sliding mode control (SMC) is recognized as robust controller with a high stability in a wide range of operating conditions, although it suffers from chattering problem. In addition, it cannot be directly applied to multiswitches power converters. In this paper, a high performance and fixed switching frequency sliding mode controller is proposed for a single-phase unipolar inverter. The chattering problem of SMC is eliminated by smoothing the control law in a narrow boundary layer, and a pulsewidth modulator produces the fixed frequency switching law for the inverter. The smoothing procedure is based on limitation of pulsewidth modulator. Although the smoothed control law limits the performance of SMC, regulation and dynamic response of the inverter output voltage are in an acceptable superior range. The performance of the proposed controller is verified by both simulation and experiments on a prototype 6-kVA inverter. The experimental results show that the total harmonic distortion of the output voltage is less than 1.1% and 1.7% at maximum linear and nonlinear load, respectively. Furthermore, the output dynamic performance of the inverter strictly conforms the standard IEC62040-3. Moreover, the measured efficiency of the inverter in the worst condition is better than 95.5%.

The Output Researching of a Cascaded Multilevel Class-D Power Amplifier

A high efficiency switch-mode power amplifier based on a cascaded multicell multilevel circuit topology is introduced in the paper. A multicell topology being operated in a unipolar phase-shifted PWM control to switch-mode amplifier system is introduced. After analysising a single-phase H-bridge unipolar PWM inverter’s output, the paper emphasis on the researching of the output of a Cascaded Multilevel Class-D Power Amplifier. The paper analyzes the advanced characteristic of the cascaded multilevel technique. Then a cascaded multilevel class-D power amplifier is built in the laboratory. The result of measurement shows a good following performance and stability.

Unipolar depletion-load organic circuits on flexible substrate by self-organized polymer blending with 6, 13-bis(triisopropylsilylethynyl)pentacene using ink-jet printing

We report the threshold voltage control and its application to electronic circuits of ink-jet printed organic thin-film transistors (OTFTs) with self-organized process using 6, 13-bis(triisopropylsilyl-ethynyl)pentacene (TIPS-pentacene) and insulating polymer on plastic substrate. The threshold voltage of OTFTs can be changed by using different polymer blending. The enhancement and depletion-mode OTFTs can be achieved, respectively, by using polystyrene and poly(vinylphenol) through self-organized blending on the common substrate. A unipolar depletion-load inverter composed of enhancement-mode driver and depletion-mode load OTFTs has been demonstrated with ink-jet printed TIPS-pentacene layer on both TFT channels. An inverter on plastic shows a gain of −90.8 V/V at the driving voltage of −2 V.

Polymer–nanoparticle hybrid dielectrics for flexible transistors and inverters

We report solution processed high-k dielectric films with excellent insulating quality (leakage current densities ∼10−8 A cm−2 at 2 MV cm−1), tunable dielectric constant (4.7–6.7) and high flexibility. The effects of incorporating different concentrations of barium zirconate (BZ) nanoparticles into poly-4-vinylphenol (PVP) gate dielectrics for flexible organic thin film transistors (OTFTs) were systematically studied. The effect of dielectric composition on the mobilities (μ), threshold voltages (VT), on/off ratios and subthreshold swings (S) has been discussed. The morphologies of dielectric and semiconductor films were investigated and shown to correlate closely with device performances. Two kinds of unipolar inverters based on these transistors have been fabricated and characterized. The depleted load inverter showed large signal gain and sharp switching. The electrical properties under various compressive and tensile strains evidenced the high mechanical stability of the dielectric films, hence the transistors and inverters. These findings will be of value for printable electronic devices on flexible substrates.

An Optimized Transformerless Photovoltaic Grid-Connected Inverter

Unipolar sinusoidal pulsewidth modulation (SPWM) full-bridge inverter brings high-frequency common-mode voltage, which restricts its application in transformerless photovoltaic grid-connected inverters. In order to solve this problem, an optimized full-bridge structure with two additional switches and a capacitor divider is proposed in this paper, which guarantees that a freewheeling path is clamped to half input voltage in the freewheeling period. Sequentially, the high-frequency common-mode voltage has been avoided in the unipolar SPWM full-bridge inverter, and the output current flows through only three switches in the power processing period. In addition, a clamping branch makes the voltage stress of the added switches be equal to half input voltage. The operation and clamping modes are analyzed, and the total losses of power device of several existing topologies and proposed topology are fairly calculated. Finally, the common-mode performance of these topologies is compared by a universal prototype inverter rated at 1 kW.

Tuning the Threshold Voltage in Organic Thin‐Film Transistors by Local Channel Doping Using Photoreactive Interfacial Layers

In recent years, organic thin-film transistors (OTFTs) have attracted a great deal of attention due to their potential applications in low cost sensors,1 memory cards,2 and integrated circuits.3 Great efforts are under way to design OTFTs with high performance, high stability, high reproducibility, and low cost.4 Two of the most crucial device parameters are the charge carrier mobility and the threshold voltage (VTh). Concerning the mobility, the main goals for most applications is its maximization.5 For VTh, the situation is more complex: for example, for integrated circuits it would be desirable to tune VTh over a broad range,6 e.g., for inverter applications. In silicon technology, complementary circuits that consist of p-channel and n-channel transistors are typically used.7 There have been many attempts to adapt this technology to OTFTs and fabricate organic complementary inverters.2,8,9 They, however, suffer from poor n-type transistor performance and/or air instability of n-type semiconductor materials. An alternative approach is the adaptation of unipolar depletion-load inverters enabling simplified processing, even if they do not provide the low power consumption and the simple circuit design intrinsic to complementary logic.10,11 Depletion-load inverters consist of an enhancement-mode driver transistor and a depletion-mode load transistor and can be realized using only p-type OTFTs. So far there have been attempts to achieve this target by using a level shifter12,13 or a dual gate structure.14 The main objective is to find a reproducible method to realize driver and load transistors with equivalent device characteristics (in particular mobilities), but different VTh values.

Single-phase power factor controller topologies for permanent magnet brushless DC motor drives

This study presents various configurations, control schemes and design of single-phase power factor controller (PFC) topologies for permanent magnet brushless DC motor (PMBLDCM) drives and provides a basis for selection of a suitable PFC topology for a specific application. Several AC-DC converter (buck, boost, buck-boost, C-uk, SEPIC, Zeta, push-pull, half bridge, full bridge) based PFC topologies are designed, modelled and applied to a 1.5-kW PMBLDCM drive for comparison of performance. Some of bidirectional bridge converter and unipolar inverter topologies are also evaluated to provide a comprehensive comparison of the PFC topologies for PMBLDCM drives. The proposed PFC converter topologies show conformity to international power quality standards with improved performance of PMBLDCM drive, such as reduction of AC mains current harmonics, near unity power factor and reduction of speed and torque ripples. A classified list of more than 200 research publications on the state of art of various PFC topologies and PMBLDCM drives is also given for a quick reference.

High-performance organic integrated circuits based on solution processable polymer-small molecule blends

The prospect of realizing high-performance organic circuits via large-area fabrication is attractive for many applications of organic microelectronics. Here we report solution processed organic field-effect transistors and circuits based on polymer-small molecule blends comprising of polytriarylamine and 5,11-bis(triethylsilylethynyl) anthradithiophene. By optimizing blend composition and deposition conditions we are able to demonstrate short channel, bottom-gate, bottom-contact transistors with high mobility and excellent reproducibility. Using these transistors we have built unipolar voltage inverters and ring oscillators with a single stage delay of 712 ns. These are among the fastest organic circuits reported to date and could satisfy the performance requirements of low-end electronic applications.

Novel maximum-power-extraction algorithm for PMSG wind generation system

The paper focuses on the development of a novel maximum-power-extraction algorithm (MPEA) including a maximum-power error-driven (MPED) mechanism and a maximum-power differential-speed (MPDS) control, for a wind generation system with a permanent-magnet synchronous generator (PMSG). In the proposed MPEA scheme, the MPED mechanism, operating like a traditional hill-climbing method, drives the output power gradually increasing to its maximum value by regulating the direction of current command according to the power variation trend. The MPDS control produces an additional step of current command based on the instantaneous difference of generator speeds, so that it can prevent the wind turbine from stalling at the suddenly dropping wind speed and achieve the object of maximum power extraction instantly as a stiff wind flowing through the wind turbine. In addition, the output is connected to a utility grid for providing energy flexibility via a unipolar full-bridge inverter controlled by a digital signal processor. The grid-connected experimentations of the proposed MPEA scheme, without any mechanical sensors for a wind-power emulation system via a PMSG driven by an induction motor, are given to examine its feasibility in practical applications.

Organic Field‐Effect Transistors and Unipolar Logic Gates on Charged Electrets from Spin‐On Organosilsesquioxane Resins

AbstractControllable shifting of threshold voltage and modulation of current in organic field‐effect transistors (OFETs) is demonstrated, resulting in the formation of unipolar inverters by making use of space‐charge electrets. Prior to the deposition of the organic semiconductor (OSC), negative corona charges are injected and trapped in the bulk of the organosilsesquioxane glass resin gate dielectrics. The effective surface potential is controlled by the corona‐charging and subsequent annealing process. It is found that the shift of the transfer characteristics is governed by the electrostatic induction effects of the charged gate electrets, and this observed shift can be related to the surface potential of the layer next to the transistor channel. The process control, efficiency, and long‐term stability of charge storage in spin‐on organosilsesquioxane glass resins are sufficient to enable the construction of simple unipolar inverters and to allow for circuit tuning. New OFET unipolar inverters with an enhancement‐mode driver and a depletion‐mode load are presented, composed of only two simple OFETs with the same channel dimensions and the same p‐type OSC on charged electrets. This design allows the implementation of full‐swing organic logic circuits and illustrates a potential process simplification for organic electronics.

Organic Field-Effect Transistors, Inverters, and Logic Circuits on Gate Electrets

ABSTRACTBy incorporating dielectrics with stored electric fields and organic semiconductors, new organic electronic components such as circuits with controlling voltages “restored” for transistor tuning can be developed. We have successfully used excellent electret materials including charged and surface-treated silicon dioxide (SiO2) and silsesquioxane (SSQ) polymers as the dielectric layer in organic field-effect transistors (OFETs). Charge injection and quasipermanent charge storage induce threshold voltage shifts and current modulation, which results from the built-in electric fields in the conduction channels. Static and dynamic characteristics of organic thin-film transistors (OTFTs) such as charging conditions and voltage/current retention were evaluated. In addition, self-assembled monolayers (SAMs) of dipolar molecules have been utilized in the dielectric layer, with different mechanisms but similar effects compared to charged dielectrics. We also present new OFET unipolar inverters, comprised of only two simple OTFTs with enhancement-mode driver and depletion-mode load to implement full-swing organic logic circuits for process simplification of electronic components in organic electronics.

Robust fuzzy neural network control for linear ceramic motor drive via backstepping design technique

This study presents a robust fuzzy-neural-network (RFNN) control system for a linear ceramic motor (LCM) that is driven by an unipolar switching full-bridge voltage source inverter using LC resonant technique. The structure and operating principle of the LCM are introduced. Since the dynamic characteristics and motor parameters of the LCM are nonlinear and time varying, a RFNN control system is designed based on the hypothetical dynamic model to achieve high-precision position control via the backstepping design technique. In the RFNN control system a fuzzy neural network (FNN) controller is used to learn an ideal feedback linearization control law, and a robust controller is designed to compensate the shortcoming of the FNN controller. All adaptive learning algorithms in the RFNN control system are derived from the sense of Lyapunov stability analysis, so that system-tracking stability can be guaranteed in the closed-loop system. The effectiveness of the proposed RFNN control system is verified by experimental results in the presence of uncertainties. In addition, the advantages of the proposed control system are indicated in comparison with the traditional integral-proportional (IP) position control system.

Recurrent fuzzy neural network control for piezoelectric ceramic linear ultrasonic motor drive.

In this study, a recurrent fuzzy neural network (RFNN) controller is proposed to control a piezoelectric ceramic linear ultrasonic motor (LUSM) drive system to track periodic reference trajectories with robust control performance. First, the structure and operating principle of the LUSM are described in detail. Second, because the dynamic characteristics of the LUSM are nonlinear and the precise dynamic model is difficult to obtain, a RFNN is proposed to control the position of the moving table of the LUSM to achieve high precision position control with robustness. The back propagation algorithm is used to train the RFNN on-line. Moreover, to guarantee the convergence of tracking error for periodic commands tracking, analytical methods based on a discrete-type Lyapunov function are proposed to determine the varied learning rates of the RFNN. Then, the RFNN is implemented in a PC-based computer control system, and the LUSM is driven by a unipolar switching full bridge voltage source inverter using LC resonant technique. Finally, the effectiveness of the RFNN-controlled LUSM drive system is demonstrated by some experimental results. Accurate tracking response and superior dynamic performance can be obtained because of the powerful on-line learning capability of the RFNN controller. Furthermore, the RFNN control system is robust with regard to parameter variations and external disturbances.

Analysis of steady-state operation of a multistack variable-reluctance stepper motor using qd0 variables

An approximate method of calculating the steady-state characteristics of a multistack, variable-reluctance stepper motor operating in the continuous speed mode is developed. The mathematical model of the motor is set forth, and the unipolar inverter drive of interest is discussed. The differential equation which governs the flux linkage is then solved explicitly using numerical integration to evaluate the flux linkage waveform. As an alternative to the direct solution, the Floquet transformation is used to obtain a time-invariant differential equation. The qd0-variables are used with the reference frame fixed in the rotor. This approach provides a means of accurately accounting for the harmonic components of the current. The method is shown to be more accurate than existing approximate methods, with a marked computational advantage over exact methods. >

Discussion, with reply, of "A split-wound induction motor design to improve the reliability of PWM inverter drives" by J.C. Salmon and B.W. Williams

With regard to the above-titled paper by J.C. Salmon and B.W. Williams (see ibid., vol.26, no.1, pt.1, p.143-50, 1990), the discusser points out that inverter drives featuring split-wound motors were marketed in 1971 by William Lear Enterprises, Inc. In reply, Salmon takes this opportunity to clarify some features of the inverter drive presented in his original paper. These features result in performance improvements over the standard unipolar inverter drive and the Lear inverter drive.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>