On-chip frequency compensation with a dual signal path operational transconductance amplifier for a voltage mode control DC/DC converter

A novel onchip frequency compensation circuit for a voltagemode control DC/DC converter is pre sented. By employing an RC network in the two signal paths of an operational transconductance amplifier （OTA）, the proposed circuit generates two zeros to realize high closedloop stability. Meanwhile, full onchip integration is also achieved due to its simple structure. Hence, the number of offchip components and the board space is greatly reduced. The structure of the dual signal path OTA is also optimized to help get a better transition response. Im plemented in a 0.5 #m CMOS process, the voltage mode control DC/DC converter with the proposed frequency compensation circuit exhibits good stability. The test results show that both load and line regulations are less than 0.3%, and the output voltage can be recovered within 15 #s for a 400 mA load step. Moreover, the compensation components area is less than 2% of the die＇s area and the board space is also reduced by 11%. The efficiency of the whole chip can be up to 95%.

Application of a Current and Voltage Mixed Control Mode for the New Fast Control Power Supply at EAST

A feedback control system is needed to restrain plasma vertical displacement in EAST （Experimental Advanced Superconducting Toknmak）. A fast control power supply excites active feedback coils, which produces a magnetic field to control the plasma＇s displacement. With the development of EAST, new demands on the new fast control power supply have led to an enhanced ability of fast response and output current, as well as a new control mode. The structure of cascaded and paralleled H-bridges can meet the demand of extended capacity, and digital control can reMize current and voltage mixed control mode. The validity of the proposed scheme is confirmed by experiments.

Three-level inverter configuration with common mode voltage elimination for induction motor drive (To continue)

The multiplicity of vector combinations for vectors of combined three-level inverters plays an important role, when deciding on the modulation scheme, to obtain minimum switching per inverter vector change, as described in the next Section. This is not possible with reduced common-mode three-level inverter structure, obtained with a five-level cascaded H-bridge configuration, as the space vectors locations do not exhibit multiplicity. Moreover, the proposed configuration requires only two power supplies, whereas the scheme with the five-level H-bridge configuration requires six isolated power supplies.

Three-level inverter configuration with common mode voltage elimination for induction motor drive

The multiplicity of vector combinations for vectors of combined three-level inverters plays an important role, when deciding on the modulation scheme, to obtain minimum switching per inverter vector change, as described in the next Section. This is not possible with reduced common-mode three-level inverter structure, obtained with a five-level cascaded H-bridge configuration, as the space vectors locations do not exhibit multiplicity. Moreover, the proposed configuration requires only two power supplies, whereas the scheme with the five-level H-bridge configuration requires six isolated power supplies.

CFOA Based Band Pass and Band Stop Ladder Filter—A New Configuration

A new technique for the conversion of ladder based filter into CFOA based filter has been proposed. The technique uses signal flow graph and converts the existing LC ladder based filter into band pass & band stop configurations. The design of band pass and band stop filter has been realized using the proposed technique. The proposed configuration is implemented using CFOA as an active device and all the capacitors are grounded. CFOA based circuits have greater linearity, high dynamic rate, high slew rate and high signal bandwidth. Simulation has been carried out using simulation software P Spice (v10.1). The simulation results have been demonstrated and discussed.

MESO-based Robustness Voltage Sliding Mode Control for AC Islanded Microgrid

A new modified extended state observer(MESO)-based robustness voltage sliding mode control(SMC)strategy is proposed for an AC islanded microgrid under system uncertainties including system parameter and load variation.First,the disturbance effect on the system is regarded as a lumped uncertainty,and a state space model of the uncertain islanded microgrid system is established.Then,a modified extended state observer is designed to estimate external disturbances and internal perturbation.Finally,considering the lumped uncertainty,a sliding mode controller with a multi-power reaching law is proposed to enable the output voltage of the system to track its reference voltage rapidly and accurately,and to enhance the robustness of the system.The simulation results confirm that the proposed robustness voltage control strategy can perform satisfactory voltage control and demonstrate a strong capability to reject parameter and load variation.

Ride through Strategy for a Three-Level Dual Z-Source Inverter Using TRIAC

A new ride through strategy is introduced in a three-level dual Z-source inverter, for isolation under semiconductor switching failure condition. Here the output will have no significant decrease in the amplitude and quality. Instead of diodes, the triacs are added to the inverter source ends, as it can perform a bidirectional power transfer also it can operate well in both low and high voltage operating conditions. The faulted part can be isolated by simply altering the firing pulses for turning on/off the triacs using the carrier based SPWM technique and resulting in a boosting output with zero common mode voltage. Consequently, it forms a common floating point or null point with a zero common mode voltage. It is experimentally verified by using MATLAB, and digital oscilloscope.

Analysis, modeling and simulation of step up converter using Matlab–Simulink and simplorer

The basic configuration of step up converter usually used in photovoltaic solar systems to increase the DC voltage generated at their outputs suffers from some drawbacks just like high ripple in the output voltage,greater losses in the system and unstable dynamic behavior.To eliminate these drawbacks,this paper introduces a two-phase connection of step up converter with uncoupled smoothing reactors.Detailed analysis,simulation and control strategy have been proposed in this paper to investigate the advantages of using such connection with uncoupled reactors.This paper is intended to prove that two-phase connection with uncoupled reactors helps increasing the output power of the converter,minimizing its output ripple and making its control easier and more efficient.It also increases the converter chopping frequency and consequently decreases the size of smoothing reactors and filters used in the system.Concerning the design of such converters,it requires a long working period of time with a significant cost and specific technical tests at nominal operating points.Therefore,simulation can essentially decrease economic and development costs.Using modulation and simulation software techniques(Simplorer,Simulink,and Matlab)throughout this paper helped simulation of very fast the converter behavior and accurate determination of its dynamic characteristics.Moreover,the paper deals with modulation of voltage control technique using Matlab and Simplorer,thus regulating the converter output current and voltage.Simulation results show that this control technique provides robust output current and voltage of step up converters and is more feasible for their chopper up conversion technique.

Coordinated Control Strategy for Operation Mode Switching of DC Distribution Networks

Due to the advantages such as low line cost,low transmission loss,and high power supply reliability,DC distribution networks have become the main development trend for future distribution networks.In this paper,a typical DC distribution network with multiple voltage levels is considered as a research object.It is proposed that the interface converters between DC buses with different voltage levels be implemented through the series-parallel combination of full-bridge LLC resonant converters.To realize the decentralized self-discipline control of DC voltage under various working conditions,different slack buses are prepared according to the voltage ranges of the DC buses,and the voltage regulation modes of the DC distribution network are divided into main voltage regulation mode,backup voltage regulation mode,and off-grid voltage droop regulation mode.By introducing a voltage coefficient related to DC voltage deviation as a basis for mode switching,the voltage fluctuations caused by slow switching between control modes in the method of traditional voltage margin control is reduced,facilitating fast and smooth switching between different voltage regulation modes.Finally,a simulation model for DC distribution networks is constructed utilizing MATLAB/Simulink.Simulation results verify the effectiveness and feasibility of the proposed voltage regulation modes and switching methods for DC distribution networks.Finally,an experimental platform is also constructed to verify the feasibility of the mode switching method proposed in this paper.

High-performance enhancement-mode thin-film transistors based on Mg-doped In2O3 nanofiber networks

Although In2O3 nanofibers （NFs） are well-known candidates as active materials for next-generation, low-cost electronics, these NF based devices still suffer from high leakage current, insufficient on-off current ratios （Ion/Ioff）, and large, negative threshold voltages （VTH）, leading to poor device performance, parasitic energy consumption, and rather complicated circuit design. Here, instead of the conventional surface modification of In2O3 NFs, we present a one-step electrospinning process （i.e., without hot-press） to obtain controllable Mg-doped In2O3 NF networks to achieve high-performance enhancement-mode thin-film transistors （TFTs）. By simply adjusting the Mg doping concentration, the device performance can be manipulated precisely. For the optimal doping concentration of 2 mol%, the devices exhibit a small VTH （3.2 V）, high saturation current （1.1 × 10^-4 A）, large on/off current ratio （〉 10^8）, and respectable peak carrier mobility （2.04 cm2/（V.s））, corresponding to one of the best device performances among all 1D metal-oxide NFs based devices reported so far. When high-K HfOx thin films are employed as the gate dielectric, their electron mobility and VTH can be further improved to 5.30 cm^2/（V.s） and 0.9 V, respectivel）, which demonstrates the promising prospect of these Mg-doped In2O3 NF networks for high- performance, large-scale, and low-power electronics.

Single-stage Five-level Common Ground Transformerless Inverter with Extendable Structure for Centralized Photovoltaics

The paper presents a five-level common ground type(5L-CGT),transformer-less inverter topology with double voltage boosting.The proposed inverter uses eight switches and two capacitors,charged at input voltage level.The inverter in its basic form acts as a string inverter for low-power PV applications.However,it can be extended to work as a scalable multi-level inverter with higher power handling capability to act as a centralized inverter.The working of the inverter with the sizing of the components is presented with mathematical analysis.The efficiency of the proposed PV inverter is found using thermal losses associated with switches using PLECS software.A prototype of 1 kW has been designed,and experimentation has been carried out.Various loads with a lagging power factor up to 0.6 have been tested with the inverter to establish the usability of the proposed inverter in a worst-case emulated homeuse scenario.The total harmonic distortion(THD)at the output has been recorded using a power quality analyzer with voltage and current THD values of 4.5%and 2.5%,respectively,which lies within the limits of IEEE 519 standards.The highest power conversion efficiency of the inverter has been recorded to be 96.20%.

A new five-level inverter with reduced leakage current for photovoltaic system applications

A general growth is being seen in the use of renewable energy resources,and photovoltaic cells are becoming increasingly popular for converting green renewable solar energy into electricity.Since the voltage produced by pho-tovoltaic cells is DC,an inverter is required to connect them to the grid with or without transformers.Transformerless inverters are often used for their low cost and low power loss,and light weight.However,these inverters suffer from leakage current in the system,a challenge that needs to be addressed.In this paper,a topology with two alternative connection models is presented to stabilize the common mode voltage and reduce the leakage current.The output voltage characteristic of the proposed inverter is five-level,which reduces the harmonic distortion in the output cur-rent compared to the two-and three-level inverters.The operation modes and output of the proposed topology are described and analyzed.The structures of the proposed inverter are simulated in MATLAB/Simulink and are compared with some well-known structures.Results show that the proposed structure with both connection models effectively reduces leakage current and improves grid current THD.