Switching Duty Cycle Research Articles

Fluid streaming and microparticles manipulating based on piezoelectric arrays excitation with various switching frequencies and duty cycles

Acoustic vortices can transfer angular momentum and trap particles. Here, we establish an annular arrays consisting of 64 piezoelectric ceramics to produce planar acoustic vortices and control the angular velocity and direction of streaming in fluid by excitation of piezoelectric. The particles in fluid chamber are trapped and move along lower pressure area. The angular velocities of them are theoretical analyzed by Bessel Function and experimentally observed by microscope. Also the PIV (Particle Image Velocimetry) method is adopted to evaluate the movement of particles in experiments and stable angular velocity of streaming by tools of MATLAB. The results show that vortices exist in fluid chamber with the excitation of piezoelectric arrays and the angular velocity is influenced by parameters of switching frequency and duty cycle of excitation. This research is helpful to realize the angular velocity and direction manipulation of particles which are trapped in fluid streaming and helpful to guide the design of acoustic tweezers.

An ultra-high gain boost converter with low switching stress for integrated multi-energy storage systems

In this paper, a high-gain low-switching-stress coupled-inductor with high voltage step-up voltage multiplier cells quadratic boost converter (VMC-QBC) is proposed. The turn ratio of the coupled inductors and the switch duty cycle increase the dynamic gain, and the two degrees of freedom adjustment and modularity of the voltage multiplier cells (VMC) make the structure more flexible. The use of the same drive signal for both switches makes control easier. While achieving multi-stage boosting and multiplication boosting from low to medium duty cycle, the passive clamping circuit absorbs the energy leaked by the coupled inductor, thus reducing the stress on the switching tube and alleviating the diode reverse recovery problem. A non-ideal model with parasitic parameters is developed to analyse the real voltage gain and the converter losses to give design guidelines. A 300 W prototype is designed and tested. The state space model of the converter is established and the working principle is analysed. Compared to other high-gain quadratic boost converters, the proposed converter has continuous input current, common ground characteristics, and high voltage gain at low to medium duty cycles to accommodate integrated multi-energy storage systems.

A dual-mode digital controller with a high accuracy load current estimator and Gaussian adaptive duty cycle switching for fast transient recovery in DC-DC buck converters

To improve the dynamic performance, this paper proposes a dual-mode digital controller with a high accuracy load current estimator and Gaussian adaptive duty cycle switching for DC-DC buck converters with an auxiliary power stage. The proposed digital controller has two operating modes: steady state and transient. In steady-state mode, a conventional PID control module is used to regulate the main power stage and the output voltage. In transient mode, a charge balance control module is responsible for controlling the auxiliary power stage to improve the dynamic performance. A long short-term memory (LSTM)-based load current estimator is proposed to obtain high accuracy load current. It employs a multiple-to-one structure and estimates the load current based on time series data (a sequence of data points indexed in time order). A Gaussian adaptive duty cycle switching is proposed to suppress the output voltage chattering when transitioning between the auxiliary and the main power stages. Simulation and experimental results demonstrate that the proposed controller has a superior dynamic performance when compared to controllers using linear-based load current estimator and direct duty cycle switching. The overshoot/undershoot and settling time can be reduced by over 50 % for a 1.9 A load transient in a 5 to 1.8 V buck converter operating switching at 2 MHz..

Electrochemically controlled blinking of fluorophores for quantitative STORM imaging

Stochastic optical reconstruction microscopy (STORM) allows wide-field imaging with single-molecule resolution by calculating the coordinates of individual fluorophores from the separation of fluorophore emission in both time and space. Such separation is achieved by photoswitching the fluorophores between a long-lived OFF state and an emissive ON state. Although STORM can image single molecules, molecular counting remains challenging due to undercounting errors from photobleached or overlapping dyes and overcounting artefacts from the repetitive random blinking of dyes. Here we show that fluorophores can be electrochemically switched for STORM imaging (EC-STORM), with excellent control over the switching kinetics, duty cycle and recovery yield. Using EC-STORM, we demonstrate molecular counting by using electrochemical potential to control the photophysics of dyes. The random blinking of dyes is suppressed by a negative potential but the switching-ON event can be activated by a short positive-potential pulse, such that the frequency of ON events scales linearly with the number of underlying dyes. We also demonstrate EC-STORM of tubulin in fixed cells with a spatial resolution as low as ~28 nm and counting of single Alexa 647 fluorophores on various DNA nanoruler structures. This control over fluorophore switching will enable EC-STORM to be broadly applicable in super-resolution imaging and molecular counting.

Intelligent MPPT control for SEPIC-Luo converter in grid tied photovoltaic system

Grid connected solar photovoltaic (SPV) systems are becoming more and more common due to steadily rising energy demand. The advantages of photovoltaic power generation, such as its eco-friendliness, low maintenance requirements, and lack of noise, are making it as a significant renewable energy source (RES). This framework presents the modeling and control design of PV grid tied system implemented with integrated single ended primary inductance (SEPIC) Luo converter. The main goal of this work includes investigating solar PV system behaviour and creating an effective grid connected solar power. Solar PV module tracks maximum power, with an aid of chaotic cascaded fuzzy a maximum power point tracking (MPPT) has developed. The DC voltage obtained is fed to 1Φ voltage source inverter (VSI) for conversion of AC voltage. In comparison to typical PWM control, the spectrum performance of the examined voltages is improved by adjusting the nominal duty cycle of main switch of SEPIC-Luo converter. So that PV output impedance is equivalent to DC-DC converter's input resistance. Finally, the obtained AC voltage is supplied to 1Φ grid for further applications. With less THD, an efficiency of 96% is achieved when the implementation of the suggested system is carried out using MATLAB/Simulink.

Design and Development of Electromagnet Power Supply for Burst Mode Repetitive High Power Microwave Sources

Single frequency High-power microwave sources like Backward Wave Oscillator, Relativistic Magnetron etc., require a high magnetic field of about 1T to 4T for efficient operation. Single-shot HPM systems usually consist of pulsed magnetic systems. However, for repetitive HPM generation, a continuous magnetic field is required. To obtain a continuous high magnetic field in the required volume usually three solutions are worldwide preferred i.e., permanent magnet, DC electromagnet with cooling arrangements and superconductor-based magnetic coil. All these three systems are bulky, expensive and technologically demanding. In this paper, a novel power supply has been suggested that discharges a charged capacitor through a magnetic coil keeping the discharging current constant for a small period like hundreds of milliseconds to a second. An IGBT switch is used to discharge the capacitor1. The duty cycle of the IGBT switch is controlled using a current feedback signal from the hall sensor, thus keeping the current steady at a preset reference value. An experimental setup has been developed using a 300mF capacitor. A constant current up to 500A is achieved for 200mS. This system is scalable. For a longer duration of operation, more capacitor modules need to be added. Details of design, development and experimental results are presented in this paper.

Shared External Driver for VHF Converter With a Synchronous Rectifier Based on Matching Network Parameters Optimization

In order to reduce the conduction loss of diode, synchronous rectification is usually adopted in very-high-frequency (VHF) converters, in which the rectifier diode is replaced by a MOSFET with very low on-state resistance. And to ensure normal operation of the synchronous rectifier switch, it is necessary to design a suitable driver with accurate timing. The widely used self-oscillating resonant drive circuit has a limited range of duty cycle adjustment, and the body diode of synchronous rectifier switch has long on-state time and a large conduction loss. Therefore, based on the analysis and parameters optimization of matching network, a shared external drive circuit is put forward. That is, the drive signals of the inverter switch and the synchronous rectifier switch come from the same external oscillation signal. On the premise of ensuring accurate drive timing, it can improve the drive signal's duty cycle of synchronous rectifier switch, reduce the conduction loss of body diode, and improve the efficiency of converter. Then on the basis of the proposed drive circuit, a VHF converter prototype with operating frequency of 10 MHz, 13 V input and 8 V/10 W output is designed, and the feasibility of the proposed drive circuit is verified by simulations together with experiments.

Linear–Assisted DC/DC Converters with Modified Current-Mode Control Applied to Photovoltaic Solar Systems

This article shows the proposal of a current-mode one-cycle control for linear-assisted DC/DC converters. Linear assisted DC/DC converters are structures that allow to take advantages of the two classic alternatives in the design of power supply systems: voltage linear regulators (classic NPN topology or LDO –low dropout–) and switching DC/DC converters. The current-mode one-cycle control technique is proposed in order to obtain the duty cycle of the linear-assisted converter switch. The proposed structure can provide an output with suitable load and line regulations. Thus, the paper shows the design and simulation results of the proposed current-mode one-cycle linear-assisted converter.

An Efficient Fuzzy Logic Based Maximum Power point Tracking Controller for Photovoltaic Systems

This paper represents a Fuzzy Logic (FL) based Maximum Power Point Tracking (MPPT) controller for a PV array. The proposed controller is aimed at adjusting the duty cycle of the DC-DC converter switch to track the maximum power of a PV array. MATLAB/Simulink is used to develop and design the PV array system equiped with the proposed MPPT controller. The developed model has been examined under different operating conditions. The performance of the proposed controller has been compared with conventional ones. The results show that the proposed controller is able to track the MPP in a shorter time with less fluctuations. In addition, the robustness of the proposed controller has been confirmed in the rapidly changing irradiation conditions.

Efficiency Optimization of the High-Power Isolated DC/DC Converters through THD and Losses Reduction in Isolation Transformers

This paper describes a method of improving efficiency of the high-power transformer-isolated DC/DC converters by means of proper selection of an inverter switch duty cycle. The paper revises old suggestions and recommendations for choosing the maximal duty cycle value on the basis of physical limits imposed by new solid-state devices. The resulting improved efficiency of the converter is described considering losses in separate energy conversion stages

A non‐isolated single‐switch ultra‐high step‐up DC–DC converter with coupled inductor and low‐voltage stress on switch

AbstractThis paper presents a non‐isolated single‐switch ultra‐high step‐up (UHSU) DC–DC converter with a three‐winding coupled inductor (CI) which is utilized to achieve ultra‐high voltage gain with a small amount of duty cycle leading to low conduction losses of the power switch and higher efficiency. The voltage gain of the suggested UHSU converter is adjusted by two methods: the duty cycle of the power switch and the three‐winding CI turn ratio, therefore enhancing the design flexibility of the suggested converter. Due to the utilization of the passive clamp circuit in the structure of the proposed converter, it is possible to select a power switch with low voltage rated and small ON‐state resistance, further enhancing the converter efficiency. The operation modes are discussed in detail and to clarify the salient features of the proposed converter, a comparison with other configurations is provided. Finally, to accredit the performance of the proposed converter, a 150‐W laboratory archetype with an input and output voltage of 20 and 300 V, respectively, at 50 kHz switching frequency is fabricated.

Performance Analysis of a Cascaded Bidirectional DC-DC Converter for High Current Applications

In this paper, a high-current DC-DC converter with bidirectional capability is presented. The proposed converter topology combines a series capacitor bidirectional converter and a conventional bidirectional converter in a cascaded manner, thus achieving a quadratic voltage gain. The proposed topology is compared with other contemporary high current topologies in terms of voltage gains, component count and conversion efficiency. Furthermore, the converter performance is validated using the Simscape SimPowerSystems toolbox of MATLAB Simulink. It is determined that this topology demonstrated a conversion efficiency of 96% and 98% in step-up and step-down mode respectively, for a 250 W load. Moreover, a current gain of 12.5 was observed in step down mode for a switch duty cycle of 0.4. Lastly, current sharing between inductors and low current ripples were also demonstrated.

Hybrid impedance and admittance control for optimal robot–environment interaction

AbstractCompliant interaction between robots and the environment is crucial for completing contact-rich tasks. However, obtaining and implementing optimal interaction behavior in complex unknown environments remains a challenge. This article develops a hybrid impedance and admittance control (HIAC) scheme for robots subjected to the second-order unknown environment. To obtain the second-order target impedance model that represents the optimal interaction behavior without the accurate environment dynamics and acceleration feedback, an impedance adaptation method with virtual inertia is proposed. Since impedance control and admittance control have complementary structures and result in unsatisfactory performance in a wide range of environmental stiffness due to their fixed causality, a hybrid system framework suitable for the second-order environment is proposed to generate a series of intermediate controllers which interpolate between the responses of impedance and admittance controls by using a switching controller and adjusting its switching duty cycle. In addition, the optimal intermediate controller is selected using a mapping of the optimal duty cycle to provide the optimal implementation performance for the target impedance model. The proposed HIAC scheme can achieve the desired interaction and impedance implementation performance while ensuring system stability. Simulation and experimental studies are performed to verify the effectiveness of our scheme with a 2-DOF manipulator and a 7-DOF Franka EMIKA panda robot, respectively.

Wide voltage range and low current ripple bidirectional DC/DC converter

ABSTRACT Along with the prosperous growth of battery energy storage system being applied in renewable energy system, wide voltage range regulation and low current ripple bidirectional DC/DC converters attract much attention of researchers. Based on a basic boost–buck converter and voltage multiplying unit (VMU), this article proposes a two-stage DC/DC converter. The front stage is an input parallel output serial connected boost–buck converter and the back stage contains a dual-coupled inductors VMU. The storage inductors of the front stage aremagnetically coupled with those in back stage. Employing dual coupled inductors VMU can increase voltage gain while not increasing main switch voltage stress during step-up mode, which can widen the application scenarios. During step-down mode, a fully controlled method can obtain a greater step-down voltage ratio. Due to the interleaving control mode of the main switches, the current ripple of the battery side is lower when the converter works bidirectionally. The proposed converter has the advantages of widening voltage range regulation and lowering current ripple while avoiding extreme switch duty cycle. This article discusses theoretical step-up and step-down work mode of the proposed converter. Experimental results sampled from a 12 V/115 V prototype are presented to verify the analysis of the proposed converter.

A high-efficiency primary-side regulation control strategy for half-bridge LLC resonant converter with wide input voltage range

The requirement of the half-bridge LLC resonant converter with a wide input voltage range is becoming higher in photovoltaic applications because of its simple structure and low switching loss. Conventional frequency modulation (FM) requires a wide switching frequency range and a high-quality factor circuit design, leading to reduced efficiency and large component volumes at light loads. To solve the problems, a high-efficiency control strategy using adaptive pulse-width and frequency modulation (APWFM) is proposed. APWFM adjusts the gain by changing the switching frequency and duty cycle simultaneously. When the output power is below the reference value, the switching frequency decreases linearly as the output power decreases, and the duty cycle is simultaneously modulated to achieve constant output voltage, so the switching frequency variation range is smaller than FM. This results in improved light or medium load efficiency in a limited frequency range while keeping a small volume of magnetic components. Also, the proposed control strategy is realized with primary-side regulation (PSR) to eliminate the optocoupler and simplify the control circuit. Experimental results demonstrate a significant improvement in efficiency at medium and light loads compared to FM, and the average efficiency is improved by 5% based on low cost and simple operation.

A Symmetric Bipolar Quadratic Buck–Boost Converter With Synchronous Triple Switches

A novel non-isolated bipolar DC-DC converter is described in this study. The proposed converter provides negative and positive outputs with the same voltage level and common ground. It exploits three power switches with the synchronous operation, resulting in a simple controller and driver implementation. Compared with the conventional counterpart DC-DC converters, the proposed converter offers buck-boost ability with a wide control range of the switching duty cycle. Additionally, the proposed converter draws a continuous and smooth current from the DC input source, making it an excellent choice for renewable energy sources (RES) and energy storage systems (ESS). Likewise, the proposed quadratic converter can provide a higher voltage boost ability with the same switching duty cycle compared to the existing transformerless bipolar converters. Hence, it offers lower conduction losses and higher efficiency for the same demanded output voltages. Theoretical analysis and experimental results based on a sample prototype are presented to prove the proposed converter's performance in CCM mode.

Direct-Switch Duty-Cycle Control of Grid-Connected n-Level Neutral-Point-Clamped Converter

Capacitor voltage imbalance is a well-recognized issue for neutral-point-clamped (NPC) converters. Hardware solutions increase the system cost and complexity, while existing software solutions generally involve sophisticated algorithms, making it difficult to extend them for more voltage levels and full power factor range. In this paper, a new control method, termed direct-switch duty-cycle control (DSDCC), is proposed and generalized for the grid-connected <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -level NPC ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> L-NPC) converter. This method has the advantages of balancing the capacitor voltages for the full range of power factors on the ac side. The main significance of the DSDCC is that it can achieve near-optimal performance with simple and fast control implementation for two reasons. Firstly, the DSDCC is based on the model directly concerning switches' duty cycles, which can easily generate gating signals for the converter with only one carrier. Secondly, instead of searching for an optimal control solution, near-optimal switch duty-cycles are derived such that the controller design can be greatly simplified. The extremely fast execution time of the proposed control algorithm is only about 3% of that of model predictive control for 5-level NPC converters. Experimental results are included to validate the proposed method with a 5L-NPC converter.

Cuckoo search firefly aided optimization framework for design of medium voltage micro-grid connected soft switching solid-state transformer (MS4T)

A single phase Soft Switching-Solid State Transformer (SS-SST) design is proposed with H-bridge topology as an alternative solution to fulfil the demand of low (or) medium grid power applications. A medium/low frequency transformers fed with H-bridge circuit are incorporate without DC-voltage link, and it’s provided sinusoidal output voltage into the grid. An optimization of Cuckoo Search Firefly (CSF) algorithm was proposed in this research to find optimum switching angle and duty cycle in bridge circuit unit. At present optimum grid power is achieved a maximum efficiency of medium/low power frequency with the help of proposed SS-SST (MS4T) model. For proposed design is used to electric aircraft, ship power systems, battery energy storage systems (BESS) and fast charging electric vehicles (EV). Which are appealing the networks of medium-voltage DC (MVDC). Proposed MS4T design is based on soft-switching transformer with low conduction loss, low EMI and high efficiency via H-bridge converter circuit. The capacitor voltage balancing control between cascade module and design of the component including a medium level voltage frequency transformer that is implement a 1 kV to 0.25 kV MS4T described. Therefore, the efficacy of the present investigations are established with MATLAB platform. The medium voltage Micro Grid (MG) output is estimated under different operation load conditions. A simulation result of the grid power is measured minimum harmonics level by using optimum switching angle, switching frequency and duty cycle arrangements.

Parameter optimization strategy of LLC converter soft start-up process based on a simplified numerical calculation model

High-frequency start-up strategy is usually used to limit the current overshoot in the resonant tank of LLC converter. However, the strong coupling among start-up frequency, initial duty cycle, and current limit increases the design complexity of parameters. This paper proposes a parameter optimization strategy of the LLC converter soft start-up process based on the numerical calculation method. With this strategy, the initial switching frequency and duty cycle are determined adaptively according to the given maximum current requirements during the start-up process. The current overshoot is suppressed and soft switching is achieved in the whole process. After the second switching period, 50% duty cycle operation occurs without oscillation. Furthermore, exponential frequency reduction is used in the process, and the current overshoot limiting condition in the initial period is discussed. Finally, a 240 W LLC converter prototype is built to verify the correctness of the theoretical analysis in this paper. In terms of current limiting, soft switching, and initial switching frequency, the comprehensive performance of the soft start-up control strategy proposed in this paper is better. Compared to the traditional control strategy, the current overshoot is reduced by 45.6%. The theoretical calculation, simulation, and experimental results are consistent.

A Nonisolated Common-Ground High Step-Up Soft-Switching DC–DC Converter With Single Active Switch

This paper presents a new non-isolated high gain (HG) dc-dc topology. Using a magnetically coupled inductor (MCI), the proposed topology can reach a higher voltage gain than those of other topologies with a moderate duty cycle. The voltage gain will be expanded further by enhancing duty cycle of the active power switch or the turn ratio (N). The resonance passive clamping circuits are presented to recycle the energy of leakage inductance and mitigating voltage spikes on the primary power MOSFET efficaciously. Then, the output diode&#x0027;s reverse-recovery problem is lightened by the resonance between leakage inductance and resonance capacitor. Accordingly, the efficiency of the presented HG converter can be improved. The active power switch turns ON and OFF in the zero current switching (ZCS) and zero voltage switching (ZVS) modes, respectively. The numerical investigation and MATLAB&#x002F;Simulink simulations are depicted in detail. Likewise, an experimental setup is developed using a 100 W solar panel that supplies the suggested dc-dc converter, validating the introduced analysis and simulations.