Buffer Capacitor Research Articles

A Novel Single-Stage Boost Single-Phase Inverter and Its Composite Control Strategy to Suppress Low-Frequency Input Ripples

Low-frequency pulsating ripples exist on the input side of a single-phase inverter, which bring some adverse effects and harm to the inverter and photovoltaic power generation system. In order to suppress the low-frequency pulsating ripple and reduce the filter circuit parameters, a novel single-stage boost single-phase inverter is proposed, which can suppress low-frequency ripple. And a three-closed-loop compound control strategy that can suppress input low-frequency ripples under the limitation of an energy storage inductor current and buffer capacitor voltage is proposed. The circuit topology, control strategy, key circuit parameters design, system modeling, and simulation of the inverters are deeply analyzed and studied. Simulation and experimental results show that the inverter has a good ability to suppress input low-frequency ripples.

Continuous input current buck DC/DC converter for small-size wind energy systems featuring current sensorless MPPT control

For decentralized electrification in remote areas, small-sized wind energy systems (WESs) are considered sustainable and affordable solution when employing an efficient, small-sized component converter integrated with a less-sophisticated, cost-effective MPPT controller. Unfortunately, using a conventional buck DC/DC converter as a MPP tracker suffer from input current discontinuity. The latter results in high ripples in the tracked rectified wind power which reduces the captured power and affects system operation especially in standalone applications which are self-sufficient and independent of grid support. Furthermore, these ripples propagate to the machine side causing vibration and torque stress which impacts turbine performance and safety. To solve this issue, a large electrolytic capacitor is placed at the buck converter input to buffer these ripples, yet at the cost of larger size, losses and reduced reliability. Oppositely, the developed C1, D4 and D6 buck converters have the merit of continuous input current at small component-size. In this paper, dynamic modelling of these three converters is developed to select the one with the least input current ripples to replace the traditional buck converter in the considered WES system. Consequently, fluctuations in the tracked power are minimized and the large buffer capacitor is eliminated. This enhances system lifetime, reduces its cost and increases tracking efficiency. Moreover, mechanical power and torque fluctuations are minimized, thus maintaining machine protection. Furthermore, a sensorless MPPT algorithm, based on converter averaged state-space model, is proposed. Being dependent on variable-step P&O algorithm, the proposed approach features simple structure, ease of control and a compromise between tracking time and accuracy besides reduced cost due to the eliminated current sensor. Simulation results verified the effectiveness of the selected converter applying the proposed MPPT approach to efficiently track the wind power under wind variations with cost-effective realization.

Bioelectrochemically triggered apoferritin-based bionanoreactors: synthesis of CdSe nanoparticles and monitoring with leaky waveguides.

Herein, we describe a novel method for producing cadmium-selenide nanoparticles (CdSe NPs) with controlled size using apoferritin as a bionanoreactor triggered by local pH change at the electrode/solution interface. Apoferritin is known for its reversible self-assembly at alkaline pH. The pH change is induced electrochemically by reducing O2 through the application of sufficiently negative voltages and bioelectrochemically through O2 reduction catalyzed by laccase, co-immobilized with apoferritin on the electrode surface. Specifically, a Ti electrode is modified with (3-aminopropyl)triethoxysilane, followed by glutaraldehyde cross-linking (1.5% v/v in H2O) of apoferritin (as the bionanoreactor) and laccase (as the local pH change triggering system). This proposed platform offers a universal approach for controlling the synthesis of semiconductor NPs within a bionanoreactor solely driven by (bio)electrochemical inputs. The CdSe NPs obtained through different synthetic approaches, namely electrochemical and bioelectrochemical, were characterized spectroscopically (UV-Vis, Raman, XRD) and morphologically (TEM). Finally, we conducted online monitoring of CdSe NPs formation within the apoferritin core by integrating the electrochemical system with LWs. The quantity of CdSe NPs produced through bioelectrochemical means was determined to be 2.08 ± 0.12 mg after 90 minutes of voltage application in the presence of O2. TEM measurements revealed that the bioelectrochemically synthesized CdSe NPs have a diameter of 4 ± 1 nm, accounting for 85% of the size distribution, a result corroborated by XRD data. Further research is needed to explore the synthesis of nanoparticles using different biological nanoreactors, as the process can be challenging due to the elevated buffer capacitance of biological media.

A Novel Single-Stage AC/DC Converter with Integrated Low-Voltage-Stress Active Decoupling Circuit and Reduced Buffer Capacitance

A Novel Single-Stage AC/DC Converter with Integrated Low-Voltage-Stress Active Decoupling Circuit and Reduced Buffer Capacitance

Load-suspended power backpack for labor saving and energy harvesting from human walk

Long-distance walk with a heavy load such as hiking and field rescue, often leads to accumulative fatigue. And continuous energy support for wearable electronics is often demanded in remote areas. Here, we report a new load-suspended power backpack that can realize labor saving and energy harvesting from human walking. An innovative suspended system is designed to decouple the synchronous movement of backpack and body, which consists of two elastomer-pulley block units and two linear sliding rod units. It also utilizes a new charge pumping technology of triboelectric nanogenerator (TENG) for high-efficient energy conversion, achieved by a specially designed main TENG and two buffer capacitors (BFCs). The main TENG has one top electrode but two bottom ones to build two separated plate variable capacitors for charge storage. The new technology is characterized by using one top electrode to synchronously drive shuttling charges in four pathways between main TENG and BFCs, and generating electricity based on shuttling charges. Consequently, it can reduce the remarkable 32.6% vertical vibrations of load and 26.7% wearing force and provide a high voltage of 820 V and a current of 103.2 μA. The average power in one current pathway is calculated to 84.1 mW (336.4 mW for four ones) with an effective power density of 29.96 mW/g, high enough to light 354 small LEDs, 235 large LEDs, the electronic watch and thermos-hygrometer. The backpack can not only be applied to relieve accumulative fatigue, but also has great potential to be an energy source for continuously driving wearable electronics for various applications.

(Invited) A Novel Computational Framework for Simulations of Bio-Field Effect Transistors

In this paper, we present the simulation results of a BioFET using a novel simulation methodology implemented in a computational framework called the Biomolecule-Oxide Simulator (BOxSim). Our novel simulation methodology is based on Gouy-Chapman-Stern and the modified Site-binding models [1][2]. Moreover, our “BOxSim” framework is the computational simulation framework that works on the hierarchical inclusion of interdependent functions to operate multiple models simultaneously. BOxSim is flexible simulation environment which considers the problems of reactive sites from oxide surfaces or non-specific bindings along with the noise present in the experimental signal to calibrate and extract the required device output characteristics [3]. It can help in generating the sensor response which can be experimentally calibrated to confirm the surface density of the specific and non-specific binding as a yield of the process while filtering the noise with the help of the developed methodology. BOxSim is designed in a way [shown in the attached block diagram] that can interact with the commercial tool (e.g., Synopsys TCAD) and our inhouse-simulator called Nano-electronic Simulation Software (NESS) to simulate the main device characteristics for designing either Ion-sensitive FET (ISFET) or Chem/Bio-FET based on the application. Industry-standard compact (BSIM) models can also be used to interact with the BOxSim which takes the generated surface potential from the BOxSim simulator and transfers it into a circuit simulator to evaluate various ISFET circuit designs.To show the capabilities of our BOxSim framework, as input we have considered several oxides, amino acids (AA) and short peptides which generate distinct signatures for arch AA or peptide. We have investigated the impact of various high-k dielectric materials [4][5] as the gate oxide on important Figures of Merit (FoM) such as current in the channel of the device, surface potential (Ψ o ), sensitivity and intrinsic buffer capacitance [6]. More importantly, the variation of differential capacitance (CT ) with the second gradient of drain current (d2 I o /dpH2 ) and surface potential (d2 Ψ o /dpH2 ) are used to uniquely identify the signatures of different amino acids or peptides. Fig. 1 shows the characteristics of different oxides with respect to the pH variation. The surface potential of oxides is dependent on the affinity constants and the zero-crossover point represents the zwitterion state. Similarly, we have simulated the detection process of different AA such as Glutamic Acid (E) and Lysine (K) immobilized with carboxyl (C-Imm.) or amine (N-Imm.) terminal [Fig. 2]. The affinity constants, isoelectric point, and density of amino acids can be extracted from the d2Ψo/dpH2 variation with the bulk pH. Other than amino acids, we have shown the distinct features of short a peptide Phenylalanine-Proline (FP) immobilized with carboxyl-terminal and the addition of Glutamic Acid to the sequence [Fig. 3]. The sensor output can be observed as the variation of drain current with the pH for the immobilized peptide sequence on the sensing surface. We have also confirmed the reliability of the designed model by calibrating the simulated results with the experimental data [7] for different physical conditions [Fig. 4]. The proposed method can be helpful in defining an efficient method for label-free protein sequencing.

Analysis and Suppression of Rectifier Diode Voltage Oscillation Mechanism in IPOS High-Power PSFB Converters

Parasitic oscillations in the rectifier diode voltage of phase-shifted-full-bridge (PSFB) converters limit their application in high-voltage and high-power situations. The conventional analysis method for parasitic oscillation in rectifier diode voltage in PSFB converters treats the filter inductor as a constant current source and fails to consider the impact of changes in filter inductor current on the rectifier diode’s parasitic oscillation. Consequently, this approach does not apply when analyzing the rectifier diode voltage’s parasitic oscillations in high-power PSFB converters employing an input-parallel output-series (IPOS) configuration with interleaved drive. This research paper introduces an innovative equivalent circuit model for analyzing the parasitic oscillations of rectifier diode voltage in IPOS high-power PSFB converters. The model takes into account the mutual influence of rectifier diode voltage oscillations between submodules under interleaved control, considering the influence of changes in filter inductor current on rectifier diode parasitic oscillation. Based on the circuit model, we explain the mechanism of multiple oscillations of the rectifier diode voltage and the reason for the high peak of the first oscillation. Consequently, the interplay of rectifier diode voltage oscillations in IPOS high-power k-module PSFB converters under interleaved control is analyzed. To mitigate the adverse effects of rectifier diode voltage parasitic oscillation, a buffering strategy involving the connection of a resistor capacitor diode (RCD) circuit in parallel after the rectifier bridge is adopted, considering the structure of the IPOS high-power PSFB converter. The study provides a detailed analysis of the circuit’s operation mechanism upon incorporating the RCD buffer circuit and establishes the relationship between buffer capacitance, resistance, and spike voltage. Furthermore, a design method for buffer capacitors and discharge resistors in buffer circuits is presented. Finally, a 100 kW prototype is tested to verify the rectifier diode voltage oscillation mechanism of the IPOS high-power PSFB converter and the rationality of the buffer capacitor and discharge resistor design method under the interleaved drive approach.

Active Power-Decoupling Methods for Photovoltaic-Connected Applications: An Overview

This study compares ripple port, stacked switched capacitor, and capacitive energy storage architectures for active power decoupling, comparing the number of components, performance, energy density, DC-link capacitor reduction, efficiency, and frequency operation to highlight their main benefits and drawbacks for single-phase grid-connected applications. The overview reveals equivalent effective energy density without electrolytic capacitors, as well as enhanced simplicity, performance, and durability, thereby providing stacked switched capacitors as an attractive power-decoupling alternative for multi-stage connected applications, based on the principle that its individual buffer capacitors absorb and deliver energy without tightly constraining their individual terminal voltages, while maintaining a narrow range voltage at the buffer DC port.

(Invited) A Novel Computational Framework for Simulations of Bio-Field Effect Transistors

In this work, we presented a novel simulation tool called the Biomolecule-Oxide Simulator (BOxSim) and its application in simulating the behavior of BioFETs. The capabilities of BOxSim are shown by investigating the impact of various high-k dielectric materials on important Figures of Merits such as current in the channel of the device, surface potential, sensitivity, and intrinsic buffer capacitance. The capabilities of our BOxSim framework allow us to discover new features in the variation of differential capacitance with respect to the second gradient of drain current and surface potential. The profile of the surface potential is used to uniquely identify the signatures (fingerprints) of amphoteric molecules like acids or peptides. The proposed model prospects the possibility to develop an efficient method for protein sequencing. The reliability of the designed model is confirmed by calibrating the simulated results with experimental data for different physical conditions. The results presented in this paper demonstrate the potential of this framework for advancing the field of biosensors and bioelectronics for the biorecognition of different molecules.

A New PFC Front End With Constant DC-Link Voltage, Reduced Buffer Capacitance, and Soft Switching

Critical conduction mode (CRM) boost power factor correction (PFC) front end is one of the most popular solutions to universal ac–dc applications below 300 W for its simplicity and high efficiency. However, its power density is largely limited by the need for a relatively bulky inductor and a buffer capacitor. This article introduces a new PFC front end that enables simultaneous size reduction of both the inductor and the buffer capacitor by achieving zero-voltage-switching of all switches and active power buffering. A 100-W universal input prototype is built, measuring a 96.7% peak efficiency and 50.8-W/in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{3}$</tex-math></inline-formula> power density. Compared to a typical CRM boost PFC front end, the prototype achieves a 47% size reduction of the magnetics, a 21% size reduction of the buffer capacitor, and an almost constant dc-link voltage, while maintaining comparable efficiency performance.

Operation Characteristics of Discontinuous Current Mode for a Dual-Active-Bridge AC-DC Converter with an Active Energy Buffer

This paper discusses operation characteristics of discontinuous current mode (DCM) for an ac-dc isolated converter for on-board battery chargers of electric vehicles. The converter discussed in this paper consists of a front-end diode-bridge rectifier, an active energy buffer, and a dual-active-bridge dc-dc converter. The energy buffer circuit absorbs the power pulsation form the single-phase ac line into a small-rated capacitor, and thus, makes it possible to reduce a required capacitance of the dc-link capacitor. This paper explains details of the DCM control method including a technique of the ripple cancel of the inductor current, to realize the power factor correction of the line current and the voltage control of the buffer capacitor at the same time without complex calculations. Then, a reference value of the inductor current and an operation range of the dc-output voltage are discussed. Experimental results obtained by a 220-V, 6.6-kW experimental setup demonstrate a sinusoidal-line current and a controlled buffer capacitor voltage as well as a smoothed dc-output current.

Ultra‐Robust and High‐Performance Rotational Triboelectric Nanogenerator by Bearing Charge Pumping

As an emerging technology to convert environmental high‐entropy energy into electrical energy, triboelectric nanogenerator (TENG) has great demands for further enhancing the service lifetime and output performance in practical applications. Here, an ultra‐robust and high‐performance rotational triboelectric nanogenerator (R‐TENG) by bearing charge pumping is proposed. The R‐TENG composes of a pumping TENG (P‐TENG), an output TENG (O‐TENG), a voltage‐multiplying circuit (VMC), and a buffer capacitor. The P‐TENG is designed with freestanding mode based on a rolling ball bearing, which can also act as the rotating mechanical energy harvester. The output low charge from the P‐TENG is accumulated and pumped to the non‐contact O‐TENG, which can simultaneously realize ultralow mechanical wear and high output performance. The matched instantaneous power of R‐TENG is increased by 32 times under 300 r/min. Furthermore, the transferring charge of R‐TENG can remain 95% during 15 days (6.4 × 106 cycles) continuous operation. This work presents a realizable method to further enhance the durability of TENG, which would facilitate the practical applications of high‐performance TENG in harvesting distributed ambient micro mechanical energy.

Active Thermal Control for Buck Converter-Based Active Power Decoupling Circuit

Aluminum electrolytic capacitors (AECs) and power semiconductor devices (PSDs) are typically identified as weak links in the reliable design of power converters. To eliminate the AECs from the design, active power decoupling (APD) circuits are preferred in single-phase power converters. However, in an attempt to eliminate AECs, this approach introduces the latter weak link in the design, i.e., PSDs in the APD circuit. This article proposes an active thermal control technique to improve the reliability of PSDs in the buck APD circuit. The proposed technique reduces the swing in junction temperature of PSDs using noninvasive power loss modulation. The power loss in PSDs is changed by varying the average voltage across the buffer capacitor. Further, a control technique is suggested to synthesize the reference for average voltage across buffer capacitor. This controller accounts for nonlinearities and minimum/maximum limits of power loss modulation. Further, the additional energy loss due to power loss modulation is restricted to a predefined limit. The proposed technique is validated with the help of circuit simulations and experimental studies with a 500 W laboratory prototype. For the selected mission profile, an increase of 28.5% in the lifetime of PSDs in buck APD circuit is estimated.

A 110/230 V AC and 15–400 V DC 0.3 W Power-Supply IC With Integrated Active Zero-Crossing Buffer

This work presents an offline power supply with fully integrated power stage in 0.18 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> high-voltage (HV) CMOS silicon on insulator (SOI). It supports both ac–dc and dc–dc conversion from 15–400 V input down to 3.3–10 V output and is optimized for applications below 300 mW such as the Internet of Things (IoT), smart home, and e-mobility. An active zero-crossing buffer enables on-chip integration of the HV buffer capacitor. Below 150 V, constant ON-time control is based on voltage intervals, sensed by ten HV threshold-detection circuits. Above 150 V, the converter operates in the resonant mode. It achieves a superior power density of 458 mW/cm3 and 84% peak efficiency.

Transformerless High-Gain Three-Port Converter With Low Voltage Stress and Reduced Switches for Standalone PV Systems

This article proposes a high-gain transformerless three-port converter (TPC) for standalone photovoltaic (PV) systems. The TPC is designed and developed based on a dual-inductor high-gain two-port converter by utilizing one of the buffer capacitors to derive the third part for PV input. A hybrid pulse-frequency modulation scheme unified with a pulsewidth modulation control strategy is adopted, which realizes the maximum power point tracking control, load voltage regulation, and bidirectional energy flow at the battery port. The proposed TPC offers the unique advantages of high voltage gain, continuous battery port current, reduced power semiconductors, lower voltage stresses, common ground shared by all the ports, low-cost gate driver, and small size of the rear-end inductor. The working principle, steady-state characteristics, small-signal models, and the control method, including design conditions, are comprehensively analyzed. The correctness of the theoretical analysis is verified by developing a 300-W experimental prototype, which shows that the maximum efficiency is 97.7%.

Research on auxiliary resonant commutated pole inverter for driving brushless DC motor

The brushless DC motor is generally used in small satellite flywheel systems due to its good control performance and structure robustness. However, its driving inverter still suffers from hard-switching that leads to higher loss and larger heatsink requirement. The resulting low power density and EMI problems have been a great challenge for the space satellite applications. This paper describes a novel auxiliary resonant commutated pole inverter (ARCPI) for driving the brushless DC motor. An inserted inductor is controlled to resonant with the buffer capacitor of the inverter’s lower arm switches; a resonant capacitor is paralleled with the inductor branch as well. Zero-current switching and zero-voltage switching conditions are therefore realized for the switches of the entire circuit. The reverse recovery problem of diodes are also avoided by zero current turning-off. The working states of the proposed novel ARCPI inverter are analyzed and the mathematical model for every state is established. Furthermore, the parameter design is discussed to provide soft-switching conditions. Finally, the proposed ARCPI inverter is applied for driving a brushless DC motor. A voltage/current double closed control loop is designed for the motor controller and the system simulation setup is built. The simulation results prove that soft-switching operation is realized for all of the switches; the proposed inverter is effective for driving brushless DC motors. Besides, the motor current fluctuation decreases by 45.7%. The motor torque and the motor speed present with good control performance as well.

A Modulation Method for Capacitance Reduction in Active-Clamp Flyback-Based AC–DC Adapters

Recent developments of fast-charging power delivery protocols are driving ac–dc adapters to 100-W power ranges. Conventional solutions in this power range employing a two-stage topology and a big twice-line frequency buffer capacitor are generally costly and bulky. This article presents a patent-pending modulation method for an active-clamp flyback converter, allowing for a single-stage adapter design with reduced capacitance requirements and higher efficiency. This is achieved by exploiting the inherent energy storage capability of the clamping capacitor while turning it into an active power buffer. No hardware modifications are needed, while all salient features of active-clamp flyback converter, i.e., soft switching and leakage recycling, are retained. Operating principles and detailed controller design are discussed, and a 100-W laboratory prototype is built. The prototype achieves 94% peak efficiency and up to 92% size reduction of the buffer capacitor. The experimental evaluation shows that the new single-stage solution enabled by the proposed modulation method is superior to the conventional two-stage and single-stage solutions in terms of cost, conversion efficiency, and power density.

OPTIMIZATION OF VOLTAGE CONVERTERS OF MATRIX AND INVERTER TYPES USING SIMULATION MODELLING

The paper presents the results of simulation modeling of functional capabilities of pulse converters of alternating voltage with free circulation of energy of two types: inverter type with intermediate link of pulsating voltage and matrix type with discharge of reactive load energy into the network. With the help of a software package OrCAD, the main modes of operation of these converters are investigated: lowering and increasing the output voltage relative to the input. The simulation results of each mode are presented in the form of diagrams of the control algorithm of the converter keys and diagrams of its electrical characteristics: input and output currents, voltage on the intermediate link (buffer capacitor) and output. On the basis of visual models for lowering and raising modes of work mathematical models and substitute electric schemes of the studied converters on intervals of their invariable structure are created. Simplified formulas for the approximate calculation of electrical parameters with sufficient accuracy for practice are proposed for both modes. Simulation models of the logic unit of the control system and the circuit of the power unit are presented separately for the three-phase matrix converter with energy reset and recovery. On the basis of visual models obtained with the help of the OrCAD software package, mathematical models and alternate electrical circuits of these converters at intervals of their constant structure were created. The conducted simulation allows to determine the most expedient areas of use of such converters and to perform optimization of their power circuits and control systems.

Single phase grid interconnected high gain boost converter with soft switching capability

&lt;div align="left"&gt;&lt;span&gt;The grid interconnected application systems require high voltage levels which leads to an efficiency reduction. To overcome this, a new high gain boost converter in association with buffer capacitor, passive clamp recovery circuit to restore leakage energy in coupled inductor is presented. The magnetic field of the linked inductor stores the energy obtained from the supply. The energy is transmitted to the connected load for consumption in further operating modes. A passive clamp network recovers the energy that is stored in the leakage inductance, enhances the gain of voltage, and improves overall system efficiency. The essential feature of this converter is that, high duty ratios are not required to achieve higher voltage gain, hence the reverse recovery problem of the diode is prevented. Moreover, a passive clamp network decreases the voltage stress of the switch, thus a minimum rating switch is used, as a result, the system's total efficiency improves. This converter output is fed as input to a single-phase full-bridge inverter and also synchronized to a single-phase grid. The performance and powers injected are analyzed by connecting a resistive load. &lt;/span&gt;&lt;/div&gt;

High efficient and high gain boost converter with soft switching capability connected to grid using dq axis current control

Renewable sources like solar PV arrays are generally operated at low voltages due to safety issues. For applications such as grid connected systems, it requires boosting to high voltage which leads to reduction in efficiency. To solve this, a new high gain and efficient boost converter which is a combination of buffer capacitor, passive clamp recovery circuit to restore leakage energy in coupled inductor is presented. The magnetic field of the linked inductor stores the energy obtained from the supply. A passive clamp network recovers the energy that is stored in the leakage inductance, enhances the gain of voltage and improves overall system efficiency. High duty ratios are not essential to achieve higher voltage gain, hence the reverse recovery problem of diode is prevented. Moreover, passive clamp network decreases the voltage stress of switch, thus a minimum rating switch be used, as a result, the system's total efficiency improves. This converter output is fed as input to a single phase full bridge inverter and also synchronized to a single phase grid by using d-q axis current controller. The performance and powers injected are analyzed by connecting a resistive load.