Duty Ratio Of Switch Research Articles

Optimising the performance of three-phase neutral-point clamped rectifier under disturbed AC mains

In this paper, a novel simplified control technique is proposed to control three-phase neutral-point clamped bidirectional rectifier using optimised switching sequences for disturbed AC mains. In space-vector modulation (SVM) technique using optimised switching sequences, duty ratio and sampling periods in each region are very important. In other words, reference vector trajectory shape and the time spent by the reference vector in each region are very important to obtain exact switching under any supply conditions. With the use of optimised switching sequences, even under ideal supply conditions, it is depicted that source-side and load-side parameters deviate from acceptable limits, and a DC-bus capacitor voltage unbalance occurs. Under the influence of disturbed AC supply, source-side and load-side parameters deviate more beyond acceptable limits which cause a very large unbalance in DC bus capacitor voltages. This non-ideal performance of the converter is responsible for the deterioration of quality of source currents and a large stress on power semiconductor devices. A new algorithm is proposed in this paper to make the converter performance ideal even under ideal and non-ideal supply conditions. According to supply conditions, the proposed technique varies the speed of the reference vector and, also at the same time, forms a required trajectory while passing through the most effective regions of SVM hexagon. The proposed technique maintains parameters within acceptable limits for source side and load side in terms of unity power factor, low input current total harmonic distortion (THD), minimum switching losses and reduced-rippled, well-regulated DC-bus voltage and also at the same time DC-bus capacitor voltage balance. The simulation results are presented to demonstrate the effectiveness of the proposed control technique.

Asymmetrical hybrid‐controlled half‐bridge LCC resonant converter with low conduction loss and wide ZVS operation range

An asymmetrical hybrid-controlled half-bridge LCC resonant converter which integrated a buck–boost converter and a half-bridge LCC resonant converter is proposed. It benefits with wide soft switching range, low conduction loss and high power density. By utilising an asymmetrical hybrid control strategy, its switching frequency and duty ratio can be adjusted simultaneously. The proposed LCC resonant converter maintains output voltage regulation and zero-voltage switching of switches in wide input voltage and load variation range. Experiment results of a 500 W prototype are provided to verify the theoretical analysis results.

Analysis and control of bridge-type fault current limiter integrated with the dynamic voltage restorer

This paper proposes a novel bridge-type solid-state fault current limiter based on dynamic voltage restorer (BFCL-DVR). The new topology uses a DC-link in the back-to-back converter of DVR. The proposed BFCL-DVR is equivalent to the conventional DVR during normal operation mode. At fault inception, the controller deactivates the series converter IGBTs in faulty phase and activates the DC-link semiconductor switches, thus establishing an equivalent bridge-type current limiter to restrict the fault current. The magnitude of the fault current is adjustable by controlling the frequency and duty ratio of the semiconductor switch that is in parallel with the discharging resistance. Moreover, the device is able to quickly recover from the current limiting mode to the normal operation mode. In this study, the operation sequence, optimal value of discharging resistance, duty cycle, and frequency of semiconductor switches are obtained. The design methodology of the proposed BFCL-DVR is fully verified using PSCAD/EMTDC software. Experimental results validate the proposed topology and theoretical analysis.

Dynamic resonant frequency control of ultrasonic transducer for stabilizing resonant state in wide frequency band

Controlling the resonant frequency of ultrasonic transducers is important to achieve the excellent performance of ultrasonic devices. The resonant frequency can be shifted by a nonlinear effect or by increasing the temperature under high-power operation. We propose a resonant frequency control method during the transducer’s operation that enables the dynamic compensation of resonant frequency shifts. To realize this, a transducer with passive piezoelectric parts was fabricated. By controlling the electric boundary condition of the passive piezoelectric parts between short and open by utilizing a metal–oxide–semiconductor field-effect transistor (MOSFET), the stiffness was changed, thus modifying the resonant frequency. In both simulation and experiment, the resonant frequency was modified successfully by controlling the switching duty ratio of the MOSFET. Additionally, a system for exciting a transducer at a resonant state with a wide frequency band was demonstrated.

Approach to the implementation of linear-assisted-based battery chargers

This article shows the proposal of a linear-assisted regulator or linear-&-switching hybrid regulator with a constant switching frequency. The control loop of the system is based on the current-mode technique. The main disadvantage of a regulator with current-mode control is the inherent instability of the loop when switch duty ratios are greater than 0.5. In order to make stable the proposed linear-assisted regulator, the article shows the technique based on a slope compensation. This kind of voltage regulators is especially devoted to battery chargers in renewable energy systems.

Design of Grid-Connected Photovoltaic System

This paper presents a grid connected photovoltaic system (PV) with a proposed high voltage conversion ratio DC-DC converter which steps up the variable low input voltages of photovoltaic module to the required DC link voltage. This voltage is applied to an H-bridge inverter which converts DC voltage into AC voltage and a low pass filter is used to filter the output. By adjusting the duty ratio of switches in DC-DC converter, the magnitude of inverter’s output voltage is controlled. The frequency and phase synchronization are ensured by a feedback signal taken from the grid. In this way, inverter is synchronized and connected with the grid to meet the energy demand. The PV system has been designed and simulated.

A Quasi-Switched-Capacitor Resonant Converter

A quasi-switched-capacitor (QSC) resonant converter is proposed for isolated dc/dc conversion in offline power supply application. Similar to the Φ2 resonant converter, the proposed converter is operated most efficiently at fixed switching frequency and duty ratio, and it features trapezoidal voltage waveforms on all switches. Full soft switching combining ZCS, ZVS on and off is achieved within a wide load range, and, therefore, the switching loss is minimized. In addition, compared to half/full-bridge converters (e.g., the LLC resonant converter and the dual-active-bridge converter), the proposed converter reduces the voltage stress on primary-side switches to 2/3 of the input voltage, and, thus, enables more choices of low-voltage devices, which are more efficient because of better figure of merit. Furthermore, the proposed converter reduces the transformer turns ratio by 2/3, and, thus, enables less number of turns of the winding, lower winding loss, and lower transformer leakage inductance, making it suitable for high-frequency operation. A 90-W 88-V/19-V 700-kHz prototype is built with 100-V eGaN FETs. The transformer design and PCB layout are presented to minimize the transformer leakage inductance and stray inductance. The prototype achieved a power density of 172 W/in3, and a flat efficiency curve with a peak value of 96%.

A New 3-Phase Buck-Boost AC Voltage Regulator

In this article, a new buck-boost converter topology based 3-phase AC voltage regulator is proposed. The proposed regulator circuit has a simple structure including only two bidirectional active switches, one inductor and one capacitor for each phase, and does not require a coupling transformer. The regulator controls each phase independently. Therefore, it can be efficiently used for 3-phase systems and independent three single-phases. Closed-loop regulator circuit operation is supported with a control law depending on the instantaneous values of the real input and the desired output voltages of the regulator in order to improve the controller efficiency. The control law provides efficient pulse width modulation switching duty ratio for the desired output voltage when the input voltage has fast fluctuations and the output load is changed. A simulation model has been implemented for the proposed 3-phase AC voltage regulator in MATLAB (The MathWorks, Natick, Massachusetts, USA)-Simulink. An experimental laboratory setup has also been built for the proposed voltage regulator. The results of both the simulation and experimental studies have demonstrated that the proposed topology is capable of and efficient for both bucking and boosting the input 3-phase AC voltage to a high-quality output voltage with a low total harmonic distortion at different input voltage and load conditions.

PI kontrolcü tabanlı yeni bir kontrol yapısının yükseltici DA-DA çevirici için tasarımı

In this paper, a new approach is proposed for control of DC-DC boost converter. In the proposed approach, open-loop control law based on the converter input voltage and the reference converter output voltage that supports the control structure based on PI controller is developed. Open loop PWM (Pulse Width Modulation) switching duty ratio is derived for the DC-DC boost converter by the control law. The control law provides to obtain the converter output voltage in a healthy and efficient manner with various system parameters through supporting the conventional PI controller. The proposed approach has been tested in MATLAB-Simulink environment as simulation. The obtained simulation results have shown that the proposed approach has provided to obtain high quality output voltage of the boost converter in different input voltage, reference output voltage and load conditions.

NLCC controller for SEPIC-based micro-wind energy conversion system

ABSTRACTThe growth of the power industry is gaining greater momentum as the usage of the non-conventional energy sources that include fuel, solar, and wind energies, increases. Wind energy conversion systems (WECSs) are gaining more popularity and are expected to be able to control the power at the output. This paper describes the current control (CC), non-linear carrier charge control (NLCCC), and fuzzy logic control (FLC) applied to the single-ended primary inductor converter (SEPIC)-based WECS. The current controller has an inherent overcurrent protection with better line noise rejection. The pulses for the switch of the SEPIC are obtained by comparing the current flowing through it with the virtual current reference. FLC is also investigated for the micro-wind energy conversion system (μWECS), since it improves the damping characteristics of WECS over a wide range of operating points. This cannot attain the unity power factor rectification. In this paper, NLCCC is proposed for high-power factor rectifier-based SEPIC in continuous conduction mode (CCM) for μWECS. The proposed converter provides an output voltage with low input current ripple due to the presence of the inductor at the input side. By comparing the signal proportional to the integral of switch current with a periodic non-linear carrier wave, the duty ratio of the converter switch is determined for the NLCC controller. By selecting the shape of the periodic non-linear carrier wave the input-line current can be made to follow the input-line voltage. This work employs a parabolic carrier waveform generator. The output voltage is regulated for changes in the wind speed. The results obtained prove the effectiveness of the NLCC controller in improving the power factor.

Inductor‐capacitor structure for getting high step‐up converter

In this Letter, a novel high step-up converter based on inductor-capacitor structure is proposed. Utilising switched capacitor to increase the voltage across inductor-capacitor structure, and by parallel charging and series discharging of inductors and capacitors, the voltage gain of the converter is improved greatly. This method can reduce duty ratio and current ripple of power switches, and hence circuit loss of the converter can be decreased. This Letter discusses topological structure and operating principle of the proposed converter. Performance comparison with other converters is presented to prove the high voltage conversion advantage of the proposed converter. Experimental results are provided to verify feasibility of the converter and correctness of the theoretical analysis.

Hybrid-mode interleaved boost converter design for fuel cell electric vehicles

For Fuel Cell Electric Vehicles, DC-DC power converters are essential to provide energy storage buffers between fuel cell stacks and the traction system because fuel cells show characteristics of low-voltage high-current output and wide output voltage variation. This paper presents a hybrid-mode two-phase interleaved boost converter for fuel cell electric vehicle application in order to improve the power density, minimize the input current ripple, and enhance the system efficiency. Two operation modes are adopted in the practical design: mode I and mode II are used with each boost converter operating in continuous conduction mode and discontinuous conduction mode. The operation, design and control of the interleaved boost converter for different operating modes are discussed with their equivalent circuits. The boundary conditions are distinguished with respect to switching duty ratio and load conditions. Transitions between continuous conduction mode and discontinuous conduction mode are illustrated for the whole duty ratio range. The expressions for inductor current ripple, input current ripple and output voltage ripple are derived and verified by simulation and experimental tests. The efficiency and power density improvements are illustrated to verify the effectiveness of the proposed design scheme.

High power factor electronic ballast using resonant converter for compact fluorescent lamp

SummaryThis paper proposes a novel single stage single switch resonant inverter with high power factor for electronic ballast. The power factor correction circuit is at the input side. It is designed to operate at discontinuous conduction mode. The lamp power is controlled by adjusting the duty ratio of the active switch of the power factor correction circuit. The circuit operation is analyzed in detail to derive the design equations. Circuit parameters are designed based on design considerations. Finally, prototype electronic ballast for a 40‐W compact fluorescent lamp is built and tested. The efficiency and the performance of the proposed converter are verified for the designed prototype. Copyright © 2016 John Wiley & Sons, Ltd.

Modulation technique for Four‐Leg Voltage Source Inverter without a Look‐Up Table

Three-dimensional space-vector modulation (3D SVM) has more popularity among the other modulation techniques of the four-leg inverter due to higher DC-link voltage utilisation. Sequencing schemes of the switching vectors in the 3D SVM are divided into Class I and II categories. Each of these classes itself has four kinds: (a) rising-edge aligned, (b) falling-edge aligned, (c) symmetrically aligned and (d) alternative sequence. In this study, implementation of the conventional 3D SVM technique in abc-coordinate for four-leg voltage source inverters is simplified, while it can be so easily adopted in all kinds of sequencing schemes. Unlike conventional techniques, the proposed technique needs no switching vector determination and duty ratio calculation as well as reduces the computational burden. In this technique, turn-on interval of the upper switches, in every switching period, is calculated without need of a look-up table and complex equations. Applying the dead time by software is very straightforward in the proposed technique. In addition, by simplification of the proposed modulation technique, it can be applied to the three-leg inverters. Simulation results in PSCAD/EMTDC environment confirm the validity and effectiveness of the proposed technique. Experimental results are also provided to confirm the validity of the new approach.

A New Synchronous Rectification for Phase Shift Modulation LLC Resonant Converter

This paper presents a new synchronous rectification (SR) for phase shift modulation (PSM) LLC resonant converters. The SR for PSM LLC resonant converter has difficulty because the secondary current is not in phase with both primary current and the voltage across the transformer. Furthermore, the open-loop SR for phase shift modulation does not perform well because the optimum pulse width is highly dependent on operating conditions such as the duty ratio of primary switches and the load current condition. The proposed SR utilizes the average load current to predict the optimum pulse width of SR so that the detection circuit for SR is not required. Effectiveness of the proposed SR is simulated and experimentally verified.

Derivation of Closed-Form Design Equations for Idealized Operation of Inverse Class-E Power Amplifiers at Any Duty Ratio

Abstract Complementary to the conventional class-E topology, inverse class-E operation has several advantages over the class-E counterpart, such as lower peak switch voltage and smaller circuit inductance, which are attractive to high power RF design and MMIC implementation. This paper derives the closed-form design equations that can be used to synthesize the idealized operation of inverse class-E power amplifiers at any switch duty ratio. Calculation of the key design parameters, such as the maximum switch voltage and circuit components values, is elaborated and compared with the case of conventional class-E operation. Further, the theoretical analysis is confirmed and verified by numerical simulations performed on a 500 mW, 2.4 GHz idealized inverse class-E power amplifier.

A single switch DC/DC converter with galvanic isolation and input current regulation for photovoltaic systems

This paper presents a novel high power single switch DC/DC converter with galvanic isolation for photovoltaic (PV) systems. The converter input current and output voltage can both be regulated independently based on the operation of a single switch. The output voltage can be controlled based on the duty ratio of the electronic switch and is no longer determined by the turn ration of the isolation transformer. With the proposed configuration and switching action, the average magnetic flux within the transformer core over one switching cycle is zero and hence a full switching cycle can be used for high power transfer. A fast current controller is also developed for the proposed converter such that maximum power point tracking (MPPT) algorithm based on PV panel output current can be developed. Moreover, MPPT based on a triangular reference input current is implemented. Experimental results are included to demonstrate the effectiveness of the proposed converter and control scheme.

Charge equalisation for series‐connected LiFePO 4 battery strings

LiFePO4 batteries are suitable for high power applications because of their advantages of large discharge current and high efficiency. Owing to the characteristics of LiFePO4 batteries, it may cause overcharge/over-discharge and reduce the cycle life of the battery when series-connected batteries are used. This study proposes a charge equaliser based on an interleaved active clamp flyback converter. The interleaved topology reduces the output ripple current. Therefore the rectifier diode conduction loss can be reduced. With a clamp capacitor and leakage inductance, the switches are turned on with zero-voltage switching while the voltage stress of switch is reduced. Furthermore, a constant switching frequency and duty ratio are designed to achieve a simple control for the proposed system. The simulations and experimental results are provided to verify the performance of the proposed charge equaliser.

Using Constant Switching Frequency Control in Linear-Assisted DC-DC Switching Converters for Photovoltaic Solar Regulators

This article shows the proposal of a linear–assisted converter or linear–&–switching hybrid converter with a constant switching frequency for photovoltaic solar DC-DC regulators. The control loop of the system is based on the current–mode technique. The main disadvantage of a converter with current–mode control is the inherent instability of the loop when switch duty ratios are greater than 0.5. In order to make stable the proposed linear–assisted converter, the article shows the technique based on a slope compensation.

1단 전력변환기를 가진 3상 절연형 커패시터리스 충전기

In this paper, we propose a three-phase isolated electrolytic capacitorless charger available for quick charger. In the proposed charger, electrolytic capacitor in DC link is eliminated by direct conversion from AC input to DC output. Conventional chargers are two stage structure including AC-DC and DC-DC converters, but the proposed charger can be simplified into single stage converter by using a matrix converter. And the waveform of input currents is improved by giving the weighting factor to the duty ratio of auxiliary switches. In order to verify the effectiveness of the proposed charger, simulations are carried out and a 1.2kW charger was constructed and experimented.