Quadratic Voltage Research Articles

Bovine Serum Albumin-Based Thin-Film Capacitors for Flexible Electronic Applications

Metal–insulator–metal (MIM) thin-film capacitors having different dielectric layer thicknesses have been fabricated by forming bovine serum albumin (BSA) layers on electrically conductive and optically transparent indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrates by using spin coating technique; the metal contacts at the top surface of BSA films have been deposited via thermal evaporation of gaseous phase aluminum. The capacitance-voltage (CV) measurements reveal the fact that the CV-characteristics of the BSA-based MIM capacitors show variable non-linearity with the change in the thickness of the insulating layer (BSA-layer). The experimentally measured CV-data are fitted with 2nd degree polynomial equations and it has been found that the quadratic voltage coefficient of capacitance (VCC) changes its sign from negative to positive as the thickness of the BSA-layer reduced below 2.0 µm. Finally, successful mechanical flexibility tests, as well as curvature tests have been carried out in order to confirm the possibility of using BSA-based MIM thin-film capacitors in flexible electronic applications in near future.

Dielectric Properties Investigation of Metal-Insulator-Metal (MIM) Capacitors.

This study presents the construction and dielectric properties investigation of atomic-layer-deposition Al2O3/TiO2/HfO2 dielectric-film-based metal–insulator–metal (MIM) capacitors. The influence of the dielectric layer material and thickness on the performance of MIM capacitors are also systematically investigated. The morphology and surface roughness of dielectric films for different materials and thicknesses are analyzed via atomic force microscopy (AFM). Among them, the 25 nm Al2O3-based dielectric capacitor exhibits superior comprehensive electrical performance, including a high capacitance density of 7.89 fF·µm−2, desirable breakdown voltage and leakage current of about 12 V and 1.4 × 10−10 A·cm−2, and quadratic voltage coefficient of 303.6 ppm·V−2. Simultaneously, the fabricated capacitor indicates desirable stability in terms of frequency and bias voltage (at 1 MHz), with the corresponding slight capacitance density variation of about 0.52 fF·µm−2 and 0.25 fF·µm−2. Furthermore, the mechanism of the variation in capacitance density and leakage current might be attributed to the Poole–Frenkel emission and charge-trapping effect of the high-k materials. All these results indicate potential applications in integrated passive devices.

A quadratic voltage model with modifications for optimal power flow of meshed networks

A quadratic voltage (QV) model with modifications is proposed to formulate the meshed networks’ optimal power flow (OPF) problem. In the QV model, convex relaxations are imposed without approximated terms. The modifications aim to drive the convex relaxations to be exact so that the obtained solution will be feasible to OPF. In the modifications, the set of nonlinear equality constraints with quadratic and bi-linear terms of voltages’ variables are convexified with the convex–concave procedure (CCP). An iterative algorithm is imposed, of which the convergence and its applicability are proved with the mathematical analysis. The superiority of the QV model with modifications is tested over several systems, which indicates the practicality of the proposed model and algorithm.

Quadratic Boost Converter With Less Input Current Ripple and Rear-End Capacitor Voltage Stress for Renewable Energy Applications

This article introduces a variant of a quadratic boost converter (QBC) with low rear-end capacitor stress by preserving its inherent abilities of less ripple continuous input current, utilization of single power switch, and quadratic voltage gain. The proposed converter utilizes two inductor and capacitor ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$LC$ </tex-math></inline-formula> ) filters with three diodes and one active switch for the quadratic conversion ratio. With the advantage of reduced rear-end voltage stress, the proposed converter can be a competent candidate in high-voltage and high-gain renewable applications. Furthermore, the operating principle and the steady-state analysis of the proposed converter in the continuous conduction mode (CCM) are discussed. In addition to the CCM analysis, a detailed discontinuous conduction mode (DCM) analysis due to the inductors <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L_{a}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L_{b}$ </tex-math></inline-formula> is presented. Furthermore, a comparative analysis of the proposed converter variant along with the QBC and its other variants is discussed. The discussion includes the key aspects, such as source ripple current analysis and rear-end capacitor voltage stress of QBC. Furthermore, a 200 W laboratory scaled prototype of the proposed converter is fabricated and tested to validate the theoretical and simulation analyses in CCM.

Analysis of positive output buck-boost topology with extended conversion ratio

In this paper, a new non-isolated buck-boost converter with positive output is designed. This buck-boost converter contains two active switches which operates synchronously. Hence, the control circuit for the given converter is simple. Compared with the conventional buck-boost converter, the newly designed topology has few advantages such as positive output voltage and quadratic voltage gain. Due to the quadratic voltage gain, this converter can achieve wide voltage conversion ratios without the use of extreme (very low or high) duty ratios. The output voltage of this proposed converter is common ground with the input voltage and its polarity is positive. The continuous conduction mode operation (CCM) of the converter is deeply analyzed in steady state conditions. The necessary component design equations are also obtained along with the switching stresses. The MATLAB/Simulink software is used to design and simulate the proposed converter. The simulated results as well as the comparisons are provided to evaluate the effectiveness of the proposed buck-boost converter.

A Quadratic Voltage Model with Modifications for Optimal Power Flow of Meshed Networks

A Quadratic Voltage Model with Modifications for Optimal Power Flow of Meshed Networks

A New Coupled-Inductor-Based Buck–Boost DC–DC Converter for PV Applications

A new buck–boost converter with coupled inductors is presented in this article. The converter benefits from low ripple input current, simple control (both power switches operate synchronously), common ground sharing between input and output ports, low-voltage stress across the power switches, positive output voltage, and quadratic voltage gain. Since the proposed converter has continuous input current, it is a proper choice for fuel cell (FC) and photovoltaic applications. Operating principles, mathematical calculation for steady-state operation, and small-signal modeling analysis are described in detail. Finally, an experimental 25-20-200 V prototype has been implemented to confirm all the mathematical derivation and aforementioned features of the proposed buck–boost converter.

Optimal Allocation and Control of Magnetorheological Dampers for Enhancing Seismic Performance of the Adjacent Structures Using Whale Optimization Algorithm

The control strategy for protecting adjacent structures from earthquake excitations is gaining increasing significance. In this study, to improve the seismic performance, a semiactive control strategy using magnetorheological (MR) dampers to couple the adjacent structures is proposed. In this control strategy, to fully exploit the performance of MR dampers, the allocation (including the locations and the number) and fuzzy logic controller (FLC) system of MR dampers are simultaneously optimally designed by whale optimization algorithm (WOA) with a special encoding scheme. Simulation results verify that WOA provides competitive performance compared with the other three metaheuristic algorithms in terms of solution quality and robustness. Compared with other semiactive control methods including on-off, linear quadratic regulator-clipped voltage law, and WOA-FLC (optimal allocation is not considered) methods, by using much less MR dampers, the proposed control strategy can exhibit more excellent overall performance in terms of reducing the seismic responses and mitigating pounding.

Noncascading Quadratic Buck-Boost Converter for Photovoltaic Applications.

The development of switching converters to perform with the power processing of photovoltaic (PV) applications has been a topic receiving growing interest in recent years. This work presents a nonisolated buck-boost converter with a quadratic voltage conversion gain based on the I–IIA noncascading structure. The converter has a reduced component count and it is formed by a pair of L–C networks and two active switches, which are operated synchronously to achieve a wide conversion ratio and a quadratic dependence with the duty ratio. Additionally, the analysis using different sources and loads demonstrates the differences in the behavior of the converter, as well as the pertinence of including PV devices (current sources) into the analysis of new switching converter topologies for PV applications. In this work, the voltage conversion ratio, steady-state operating conditions and semiconductor stresses of the proposed converter are discussed in the context of PV applications. The operation of the converter in a PV scenario is verified by experimental results.

Demonstration and characterization of 500 V MIM capacitor with Al2O3 dielectric layer for power integrated circuits

In this work, the metal–insulator–metal (MIM) capacitor with Al2O3 dielectric layer above 1 μm and TiN electrodes has been fabricated by magnetron sputtering for power integrated circuits application. The characteristics of the TiN and Al2O3 films were inspected by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) technologies. According to the experimental results, the fabricated MIM capacitor exhibits a very low leakage current density of 4.2×10-5 A/cm2 at 500 V, although the capacitance density is relatively small (0.08 fF/μm2at 100 kHz) due to its high voltage withstanding capability. In addition, the quadratic and linear voltage coefficients of the capacitor are 0.08 ppm/V2and −2.39 ppm/V, respectively (at 100 kHz), indicating its excellent voltage linearity. Leakage mechanisms of the capacitor have been investigated as well. As a result, the fabricated Al2O3 MIM capacitor is a very promising candidate for power integrated circuits application.

Design and Implementation a Single-Switch Step-Up DC-DC Converter Based on Cascaded Boost and Luo Converters

We designed and implemented a single-switch step-up DC-DC converter based on cascaded boost and Luo converters. The proposed converter demonstrated a quadratic voltage gain and a high efficiency, which makes it suitable for renewable energy applications, where a high voltage gain ratio is desired without imposing a high number of bulky items or employing a high duty cycle of the active switches. This converter benefits from the continuity of the input current waveform, which equips the maximum utilisation of renewable energy sources. While a transformer-less high voltage-gain was achieved, the voltage and current stresses of the power switch and diodes were kept low in comparison with the existing quadratic DC-DC converters. We analysed the converter in both continuous and discontinuous conduction modes. A non-ideal model of components was considered for power loss and efficiency calculations and comparisons. Finally, the simulation results were extracted with PLECS and validated with experiments on a 120 W prototype.

The Electrical Performances and Leakage Current Conduction Mechanism of Al2O3/ZrO2/SiO2/ZrO2/Al2O3 MIM Capacitors

In this paper, we prepared the Al2O3/ZrO2/SiO2/ZrO2/Al2O3 (AZSZA) metal-insulator-metal (MIM) capacitors by atomic-layer-deposition technique. By increasing the thickness of SiO2 from 0 nm to 3 nm, the quadratic capacitance voltage coefficients improved significantly from 2130 ppm/V2 to −121 ppm/V2 because of the offsetting effects of ZrO2 and SiO2 dielectric. Meanwhile, for our interested SiO2=3nm sample, the capacitance density is 7.40 fF/µm2 and the leakage current density is 3.08 × 10−8 A/cm2 at 5 V. We also studied the leakage current conduction mechanism of AZSZA dielectric MIM capacitors and found that at high field the conduction mechanism was dominated by Poole Frenkel emission.

High Step-Up Converter Based on Non-Series Energy Transfer Structure for Renewable Power Applications.

In this paper, a high step-up boost converter with a non-isolated configuration is proposed. This configuration has a quadratic voltage gain, suitable for processing energy from alternative sources. It consists of two boost converters, including a transfer capacitor connected in a non-series power transfer structure between input and output. High power efficiencies are achieved with this arrangement. Additionally, the converter has a common ground and non-pulsating input current. Design conditions and power efficiency analysis are developed. Bilinear and linear models are derived for control purposes. Experimental verification with a laboratory prototype of 500 W is provided. The proposed configuration and similar quadratic configurations are compared experimentally using the same number of components to demonstrate the power efficiency improvement. The resulting power efficiency of the prototype was above 95% at nominal load.

A New High-Gain DC-DC Converter with Continuous Input Current for DC Microgrid Applications

The growth of renewable energy in the last two decades has led to the development of new power electronic converters. The DC microgrid can operate in standalone mode, or it can be grid-connected. A DC microgrid consists of various distributed generation (DG) units like solar PV arrays, fuel cells, ultracapacitors, and microturbines. The DC-DC converter plays an important role in boosting the output voltage in DC microgrids. DC-DC converters are needed to boost the output voltage so that a common voltage from different sources is available at the DC link. A conventional boost converter (CBC) suffers from the problem of limited voltage gain, and the stress across the switch is usually equal to the output voltage. The output from DG sources is low and requires high-gain boost converters to enhance the output voltage. In this paper, a new high-gain DC-DC converter with quadratic voltage gain and reduced voltage stress across switching devices was proposed. The proposed converter was an improvement over the CBC and quadratic boost converter (QBC). The converter utilized only two switched inductors, two capacitors, and two switches to achieve the gain. The converter was compared with other recently developed topologies in terms of stress, the number of passive components, and voltage stress across switching devices. The loss analysis also was done using the Piecewise Linear Electrical Circuit Simulation (PLCES). The experimental and theoretical analyses closely agreed with each other.

A quadratic voltage model for optimal power flow of a class of meshed networks

A quadratic voltage model is proposed to formulate the optimal power flow problem of the meshed networks with maximum phase angle differences between buses less than π/2. The quadratic voltage model uses the real and imaginary parts of node voltage directly so as to avoid the problem of inexact angle relaxation, which is the Achilles’ Heel in previous researches. The nonlinear equalities between quadratic terms of voltages’ variables are relaxed into convex second-order cone constraints. A penalty term is added into the objective function to guarantee the exactness of the relaxation, which is proved with the strict inequality on the upper and lower bounds of power generation nodes. For the proper value of the penalty factors, analytical representation and mathematical proof are provided. The applicability of the proposed model is tested over several systems, which shows better efficiency and less computational time.

Flexible Al-Ti-Zn-O MIM capacitors fabricated by room temperature atomic layer deposition and their electrical performances

We pioneered to employ room temperature atomic layer deposition (RTALD) to fabricate flexible Al-Ti-O based metal-insulator-metal (MIM) capacitors on three polymer substrates of polyethylene terephthalate (PET), polyimide (PI) and epoxy resin (epoxy) without any post-processing. Zn was introduced to Al-Ti-O dielectrics to tune its electrical properties through varying ALD cycle ratio and cycle number. Under the optimal processing, the flexible MIM capacitors of Al1.56Ti0.47Zn0.06O3 exhibits comprehensively better performance such as higher capacitance density of 7.4 fF/μm2, smaller leakage current density of 2 × 10−8 A/cm2 at 3 V, and reasonable quadratic voltage linearity of 422 ppm/V2. X-ray photoelectron spectroscopy analyses reveal that the incorporation of a slight amount of Zn into Al-Ti-O dielectrics significantly decreases the oxygen vacancy concentration from 6.7% to 0.8%, beneficial for the improvement of electrical performance. Furthermore, our 2 × 2 cm2 flexible MIM capacitors could bear 4000 bending cycles at bending radius of 8.2 mm, showing better electrical stability. These results indicate that RTALD-derived Al-Ti-Zn-O dielectrics are competitive MIM capacitor candidates for flexible electronics and wearable devices. RTALD technology exhibits exciting potentials in flexible electronic device fabrication.

Three-level quadratic boost DC-DC converter associated to a SRM drive for water pumping photovoltaic powered systems

This paper presents a water pumping system powered by solar photovoltaic (PV) panels employing a switched reluctance motor (SRM) drive and a three-level quadratic Boost (3LQB) DC-DC converter for a dual output. The DC-DC topology is characterized by quadratic voltage static gain, capability to ensure voltage balance in the output capacitors and reduced voltage stress across power switches and diodes. The three-level voltage of the DC-DC converter allows to connect an asymmetrical half-bridge (AHB) converter integrated into the SRM drive. The DC-DC converter also operates in continuous conduction mode (CCM) which, combined with a proposed maximum power point tracking (MPPT) algorithm, helps to optimize the power supplied by the PV panels. A laboratory prototype was also developed and installed in a workbench to verify its practical implementation considering all devices involved. The tests were performed considering different loads and solar irradiations to verify the system performance under different situations. The PV panels were simulated using a remotely controlled DC power source to impose the typical characteristic I-V curves of the PV panels according to solar irradiation and the water pump behavior was emulated in the laboratory using a controlled torque load coupled to the SRM drive. The experimental results indicate that the proposed solution allows to fully exploit the solar energy to provide as much as possible a continuous water flow in isolated pumping solutions. The operating limits of this solution should be determined by the minimum water flow rate required, necessary head (elevation) and net positive suction head (NPSH).

Analysis and Design of Quadratic Following Boost Converter

A boost converter which closely follows the quadratic converter voltage gain is proposed in this article. At tradeoff duty ratios, this converter is able to boost a lower input dc voltage to higher values at load side, higher than the traditional boost converter. This article also proposes a double-loop voltage-mode controller (DLVMC) for load voltage regulation, which exhibits better reference tracking as well as robust performance over the conventional proportional-integral-derivative (PID)-type robust controller. Also, addition of load voltage forward term suppresses the sensitivity and stability issues. An analytical and graphical approach is established to formulate the stabilizing region for the DLVMC parameter set. Parameter-space approach is the basis for the evolution of all possible controller parameter stabilizing regions. Furthermore, guaranteed combined sensitivity and guaranteed up–down glitch margin-related multiple performance constraints are simultaneously adopted in addition to absolute stability. As a result, any parameter combination corresponding to these stabilizing regions definitely ensures the proposed closed-loop converter system stability with sufficient robustness. An optimization methodology using integral time square error performance index is adopted to arrive at the optimal parameter set for DLVMC belonging to robust stabilizing regions. In order to assess the efficacy of the proposed robust controller design technique, a 75-W laboratory prototype is designed for experimentation. The DLVMC effectiveness in terms of load voltage regulation against the load and source perturbations along with reference tracking features is demonstrated experimentally. To also highlight its performance improvements, dynamic responses are compared and illustrated with the sample PID controller dynamic performance characteristics.

A New Transformerless Quadratic Boost Converter with High Voltage Gain

ABSTRACT This paper presents a new single-stage, nonisolated dc to dc boost converter with quadratic voltage gain for low and medium power applications. The attractive features of the topology are that it is having a simple structure with a single switch and its gain is twice that of a conventional quadratic boost converter (CQBC). The fact that it utilizes a single switch makes the practical implementation of the converter easy, as only one gate pulse is needed to control the switch. The other advantage of the proposed converter is that coupled inductor is not used in this topology. The coupled inductor is helpful in increasing the gain of the converters but at higher duty ratios the energy trapped in leakage inductance can increase the stress across the switch. The converter operates in continuous current mode (CCM) which makes it an attractive choice for renewable energy applications. The topology is compared with other existing topologies of quadratic gain converters. The efficiency of the proposed converter is determined by incorporating switching and conduction losses of various components through power loss data given in datasheet of MOSFET and diodes using PLECS which is a simulation software specially designed for carrying out the loss analysis of power electronics converters. A 100 W prototype of the proposed converter is developed in the lab. The experimental results closely agree with simulation and theoretical results.

VCC-α nullification and leakage reduction in Pt/Ba0.5Sr0.5TiO3/Pt thin-film capacitor by MgO barrier and PDA for energy storage application

A critical performance parameter of thin-film metal–insulator–metal capacitors when used for energy storage application is leakage current. Introduction of another insulator barrier layer at metal–insulator interface having low electron affinity enhances leakage current performance. The probability of deterioration in capacitance is higher while enhancing leakage performance by barrier layer establishment. The effects of Pt-Ba0.5Sr0.5TiO3 (BST) interface barrier layer and post deposition annealing (PDA) on voltage coefficient of capacitance and leakage current density in Pt/Ba0.5Sr0.5TiO3/Pt thin-film capacitor are reported in this paper. The capacitance measurement is done at low frequency as it meant for energy storage. It is observed that PDA of Pt/MgO/Ba0.5Sr0.5TiO3/MgO/Pt thin-film capacitor at 700 0C in O2 gas environment for 30 min nullifies quadratic voltage coefficient of capacitance (VCC-α). The VCC-α obtained for as-deposited capacitor is −34408 ppm V−2 while that of capacitor annealed at 700 0C is 4.88 ppm V−2 which is the least VCC-α ever reported. A gradual leakage current performance enhancement is observed while increasing annealing temperature and a very low leakage current density of 48 nA cm−2 is observed when annealed at 700 0C. The diffraction peaks in XRD pattern of capacitor annealed at 700 0C indicate good crystallinity achieved in Pt, Ba0.5Sr0.5TiO3 and MgO layers due to high-temperature PDA process. This substantiates the best leakage current characteristics in Pt/MgO/Ba0.5Sr0.5TiO3/MgO/Pt thin-film capacitor annealed at 700 0C than as-deposited capacitor and capacitor annealed at lower temperatures. Further we observed an energy band gap enhancement of 0.055 eV in every 100 0C rise in temperature from the UV–Vis NIR spectroscopy. This continuous energy band gap enhancement while increasing annealing temperature also justifies the reduction in leakage current density at high PDA temperature.