Phase-shifted Modulation Technique Research Articles

Reduced-Order Averaged Model and Non-Linear Control of a Dual Active Bridge DC-DC Converter for Aerospace Applications

The paper presents a generalized averaged model and a reduced-order averaged model of a dual active bridge bidirectional dc-dc converter, taking into account parasitic components. On the basis of these models, a particular non-linear voltage control scheme is suggested using an integral sliding mode control approach for driving the adopted single phase shift modulation technique. The main operative conditions of the converter have been examined through extensive simulations. The numerical results confirm the effectiveness of the proposed strategy. The suggested control exhibits a strong robustness against parameters variations and disturbances and presents a very simple implementation.

Comparison of Performance of Phase-Shift and Asymmetrical Pulsewidth Modulation Techniques for the Novel Galvanically Isolated Buck–Boost DC–DC Converter for Photovoltaic Applications

This paper discusses realization possibilities of the buck mode in the novel magnetically integrated quasi-Z-source series resonant converter (qZSSRC) with secondary resonance. Our aim was to achieve higher power conversion efficiency at different power levels and dc voltage gains of the converter. The phase-shift modulation (PSM) was comprehensively compared with the asymmetrical pulsewidth modulation (PWM). Both control techniques were evaluated for the case of the discontinuous current through the resonant network, which made their realization more challenging. The operating principle of the qZSSRC in the buck mode with two compared control techniques was explained by means of steady-state analysis. To verify the theoretical assumptions, a 250-W prototype of the photovoltaic module integrated converter was assembled and tested. It was experimentally confirmed that in contrast to the PSM, the asymmetrical PWM for the buck mode control of the qZSSRC will lead to higher power conversion efficiency at different power levels and dc voltage gains of the converter, except the operating points close to the boundary with the normal mode of the converter.

A Hybrid Phase-Shift Modulation Technique for DC/DC Converters With a Wide Range of Operating Conditions

This paper presents a new hybrid phase-shift modulation technique which is able to provide soft switching for the entire operating conditions of dc/dc converters. The proposed phase-shift modulation technique does not require any extra active/passive circuitry to guarantee soft-switching. In addition, the proposed technique can be applied to the general category of power circuit topologies for dc/dc converters, which use a full-bridge inverter in their power circuit. The proposed hybrid phase-shift modulation technique includes two distinct modulation strategies based on the operating condition of the converter. Thus, it has a variable structure that can optimize the performance for various operating conditions. The main advantages of the proposed technique are the achievement of soft-switching independent of the load condition, and optimized performance. Theoretical analysis and simulation/experimental results demonstrate the superior performance of the proposed hybrid phase-shift modulation technique over the conventional one.

On Improving Phase-Shifted PWM for Flying Capacitor Multilevel Converters

This letter proposes a phase-shifted pulse-width modulation (PS-PWM) technique for the flying capacitor (FC) multilevel converter that improves the quality of the line-to-line voltages. In traditional PS-PWM, the line-to-line voltages include intervals that switch between nonadjacent voltage levels, which deteriorates the harmonic performance. The proposed PS-PWM constantly achieves line-to-line voltages with switching transitions between two adjacent levels. The proposed modulation technique is implemented using two sets of $n$ evenly phase-shifted carriers that are alternatively applied depending on the instantaneous value of the reference signal of each phase-leg. Furthermore, it can be implemented in FC multilevel converters with any number of levels while maintaining natural capacitor voltage balance. Experimental results from a four-level FC converter prototype are presented.

New Multilevel Converter Based on Cascade Connection of Double Flying Capacitor Multicell Converters and Its Improved Modulation Technique

This paper proposes a new multilevel converter based on the cascade connection of double flying capacitor multicell (DFCM) converters, as multilevel modules, to decrease the voltage diversity of the flying capacitors. Furthermore, a new switching pattern based on the phase-shifted pulse-width modulation technique is proposed to reduce the voltage ripple across the flying capacitors. Moreover, the proposed modulation technique reduces the rms value of the current flowing through flying capacitors. This results in an increase in the life time of flying capacitors and a decrease in the capacitance of the flying capacitors, to keep the same amount of the ripple, meaning a reduction in the physical size of the converter. In addition, this paper presents an analytical approach to calculate the average and rms currents of the insulated gate bipolar transistors (IGBTs)/diodes in the DFCM converter in a closed-form expression. The derived closed-form equations to calculate the average and rms currents of the IGBTs/diodes are utilized to investigate the conduction power losses in a DFCM converter and the proposed multilevel converter. Numerical results of the derived closed-form equations match the simulation results well, which validates the derived equations. Furthermore, simulation results and experimental measurements of the proposed multilevel power converter, configured by cascading two two-cell five-level DFCM converters, are presented to validate the performance of the proposed converter as well as the suggested modulation technique.

A Comparative Study of Two Buck-Type Three-Phase Single-Stage AC–DC Full-Bridge Converters

Almost all previously proposed single-stage, three-phase ac-dc converters are based on the boost converter, and the strengths and weaknesses of boost-based single-stage converters are well known. This is not the case for buck-based single-stage converters as little, if any, comparable research has been performed on these converters. The authors have previously investigated a three-phase ac-dc, single-stage buck-type converter that can simultaneously perform power factor correction and dc-dc conversion using the standard phase-shift pulse-width modulation technique for dc-dc full-bridge converters. This paper is a continuation of that work as its main focus is a comparison of the performance and characteristics of this converter with those of a modified version of the same converter. In this paper, the fundamental principles of both the converters are explained, the modes of operation of the modified converter are explained in detail and a procedure for the design of this converter is demonstrated with an example. Experimental results obtained from a prototype of the modified converter are presented and based on these results; the two converters are compared in terms of parameters such as input power factor and efficiency.

Comparison of Phase-Shift and Step Wave Modulation Technique applied to Symmetrical Cascaded Multilevel Inverter

This paper presents a comparison between the phase-shift and the step wave modulation techniques applied to symmetrical cascaded multilevel inverter. Initially, the phase-shift modulation and a simple method to determine the switching angles used to generate a step pulse waveform are presented. Performance indices as harmonic spectrum, total harmonic distortion, common mode voltage, power losses in semiconductors devices and first/second distortion factors are analyzed to demonstrate the performance of these modulation techniques. The modulation strategy that presents more advantages is implemented in FPGA and the experimental results are presented.

Elimination of DC voltage sources and reduction of power switches voltage stress in stacked multicell converters: analysis, modeling, and implementation

SUMMARY Multilevel converters have been widely used in medium-voltage high-power applications. One of the typical breeds of multicell converters is stacked multicell converter (SMC). This paper presents an improved configuration for SMCs, accompanied by its analysis, modeling, and implementation. The main advantages of the proposed converter, in comparison with the conventional one, are that the numbers of required dc voltage sources are halved in the improved topology and also the voltage rating of half of the power switches are decreased by 50% which results in reducing the cost, size, and weight of the SMCs effectively. This progress is achieved by connecting the upper stacks to the lower stacks back to back while the number of high-frequency power switches and flying capacitors (FCs), voltage ratings of FCs, as well as the number of high-frequency switchings during a full cycle are kept constant. The control methodology is based on the phase-shifted carrier sinusoidal pulse width modulation technique; therefore, the well-known natural balancing phenomenon of FC voltages, one of the critical advantages of SMCs, is maintained in the proposed converter. This paper also presents an analytic model to study and analyze the dynamic of FC voltages in the proposed SMC. Numerical analysis results of the derived analytic model, simulation results, and, moreover, measurements taken from the laboratory prototypes are presented in order to validate the effectiveness and advantages of the proposed configuration as well as its control strategy and analytic model. In addition, the comparison of the proposed converter with other types of multilevel converters is carried out to highlight the advantages of the proposed structure. Copyright © 2013 John Wiley & Sons, Ltd.

Symmetry-Breaking Bifurcation in Series-Parallel Load Resonant DC-DC Converters

This paper reports the occurrence of symmetry-breaking bifurcation in the series-parallel load-resonant dc-dc converter with L-C output filter. The constant frequency phase shift modulation technique is employed with proportional-integral controller in the output voltage regulation. The complexity of the system is contributed by the fact that a six dimensional state space is divided into twelve subsystems by six switching surfaces. It is shown that the dynamics are not only related to the resonant components but are also heavily dependent on the output filter design. The understanding of the dynamics resulting from the interaction between the resonant tank and the filter circuit helps in designing more reliable converters. We show that the first instability can be caused by Neimark-Sacker as well as symmetry-breaking bifurcations. Stable as well as unstable periodic orbits are identified, and their characteristic multipliers are computed by a newly developed algorithm based on a combination of Filippov's theory and shooting method with Newton-Raphson algorithm.

DC Voltage Controller for Asymmetric-Twin-Converter-Topology-Based High-Power STATCOM

A four-level static compensator integrating two 2-level converters, supplying/absorbing reactive power to/from the grid, is reported in our earlier paper. Reduced component count, simpler layout for switches, and smaller dc-link capacitor values are the attractive features of the proposed topology over the diode clamped and cascaded multilevel converters. This paper suggests further improvements in this topology. Suitable selection of the dc-link voltage values reduces distortion in the current fed to the grid. In addition, circuit topology is modified to avoid the split-capacitor dc links. This reduces the number of independent dc capacitor voltages to be controlled and eliminates the flow of third-harmonic current through the transformer. In order to improve the performance, a phase-shifted carrier-based pulsewidth modulation technique is used. A mathematical model of the system is derived, based on which a controller for the scheme is designed. The effectiveness of the scheme is verified through detailed simulation study. To confirm the viability of the scheme, experimental studies are carried out on a scaled-down laboratory prototype developed for the purpose.

Cross-Term Selective, Two-Pulse Correlation Measurements by Phase-Shifted Parallel Modulation for Analysis of a Multi-Photon Process

We propose a new modulation technique for phase-sensitive detection to extract a cross-term signal appearing in multi-pulse experiments and demonstrate the selective detection of cross-term signal on two-pulse correlation measurements. This modulation technique can be widely applied to the selective detection in multi-beam laser experiments such as two-pulse correlation, auto-correlation, and double-resonance experiments, because the selectivity can be realized by using a conventional single-frequency mechanical chopper and 2f phase-sensitive detection. The effectiveness of the proposed technique was confirmed by two-pulse correlation measurements of two-photon-excited fluorescence from rhodamine 6G. In addition to the selective observation of a correlation peak, the technique succeeded in observing a weak correlation background. By combining asymmetric, two-pulse correlation measurements with the proposed technique, it was clarified that the background was produced by a three-photon process and assigned to fluorescence depletion caused by an up-conversion process. The results indicate that the cross-term selective, two-pulse correlation method that is based on the phase-shifted parallel modulation technique is powerful tool to find and analyze a high-order optical event buried in a low-order optical event.

PV Power-Generation System with a Phase-Shift PWM Technique for High Step-Up Voltage Applications

A PV power-generation system with a phase-shift pulse-width modulation (PWM) technique for high step-up voltage applications is proposed. The proposed power-generation system consists of two stages. In the input stage, all power switches of the full-bridge converter with phase-shift technique can be operated with zero-current switching (ZCS) at turn-on or turn-off transition. Hence, the switching losses of the power switches can be reduced. Then, in the DC output stage, a voltage-doubler circuit is used to boost a high dc-link bus voltage. To supply a utility power, a dc/ac inverter is connected to induce a sinusoidal source. In order to draw a maximum power from PV arrays source, a microcontroller is incorporated with the perturbation and observation method to implement maximum power point tracking (MPPT) algorithm and power regulating scheme. In this study, a full load power of 300 W prototype has been built. Experimental results are presented to verify the performance and feasibility of the proposed PV power-generation system.

Modeling and Performance Analysis of the DC/DC Series–Parallel Resonant Converter Operating With Discrete Self-Sustained Phase-Shift Modulation Technique

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A dynamic study of the dc/dc series–parallel resonant converter operating with a discrete self-sustained phase-shift modulation technique is presented. The study includes the synthesis of a suitable averaged large-signal dynamic model and the design of a nonlinear feedback controller based in the input–output linearization approach. The proposed controller and modulation type provide some outstanding features: zero-voltage switching operation for the whole load range, narrowed frequency variation range, fast transient response, and robustness in relation to external parameter variations. Experimental and simulation results are reported to validate the theoretical predictions and confirm the superior performance of the nonlinear controller when it is compared with a conventional linear controller. </para>

Design and implementation of FPGA-based phase modulation control for series resonant inverters

Owing to the tremendous advances in the digital technology, and improved reliability and performance of the digital control mechanisms, this paper focuses on design and implementation of digital controller using FPGA-based circuit design approach. The digital controller proposed is designed for series resonant inverter used in DC-DC converter applications. Phase modulation technique is proposed for the realization of digital controller on FPGA. The Series Resonant Converter (SRC) is considered in this paper as a preferred converter topology for high power, high voltage power supplies. This paper studies the implementation of phase shift modulation technique using FPGA. The inverter designed, is IGBT based, and Zero Voltage Switching (ZVS) technique is implemented due to reduced stresses on devices and increased efficiency. The phase modulated series resonant inverters (PM-SRC) promotes ZVS operation when its switching frequency is greater than resonant frequency. The designed PM controller is realized using FPGA on which control algorithm and other features of a controller are developed. The series resonant inverter is built and tested for full load under open loop and closed loop conditions at a switching frequency of 20 kHz. The results are presented under varying load conditions. The simulation and the experimental results were found to match closely.

Self-sustained phase-shift modulated resonant converters: modeling, design, and performance

This paper presents an improved control technique for the full bridge series, parallel, and series-parallel resonant converters. This control technique combines a self-sustained oscillation mode with a phase shift modulation technique that can significantly reduce the range of frequency variation necessary for obtaining zero voltage switching in the resonant converters. This frequency reduction provides optimized component ratings and operating frequency. A simple and accurate low order mathematical model based on the sampled data technique that fully describes the steady-state, and dynamic performance of the resonant converters, has been developed. A refinement algorithm is developed to enhance the accuracy of the modeling technique and the converter design. The improved converter performance and the feasibility of the developed dynamic model have been investigated using the series-parallel resonant converter topology with a capacitive output filter. Finally, MATLAB numerical solutions, PSIM simulation results, and experimental results are given to highlight the merits of the proposed work.

Characterisation of differential group delay of fibre devices with high resolution and enhanced immunity to environmental perturbation

By integrating a fibre polarisation scrambler with the modified phase shift modulation technique, differential group delay characterisation is demonstrated with high wavelength and delay resolution, and enhanced measurement immunity to environmental perturbation.

A 1 kW 500 kHz front-end converter for a distributed power supply system

The analysis, design, and performance are discussed of a prototype high power-density converter suitable for use in the front-end of a distributed power supply system. The system delivers 1 kW to a regulated 40 V distribution bus from the rectified utility line. Its switching frequency is 500 kHz, and it uses a phase-shifted pulse-width modulation technique to avoid primary-side switching losses. The converter's topology is a standard power MOSFET H-bridge that drives a transformer. The output of this transformer is rectified by a full bridge of Schottky diodes. The switches of this forward converter are operated in a fixed-frequency PWM mode. The dominant parasitic elements are the transformer's leakage inductor, the MOSFETs' output capacitors, and the rectifiers' junction capacitors. Of these three groups of parasitic elements, only the leakage inductors do not result in a direct switching loss. To avoid MOSFET switching losses, the converter is controlled with a special gate-drive pattern that permits full recovery of the MOSFETs' capacitive energy. At the same time this drive scheme gives zero-voltage switching for the MOSFETs. The converter's efficiency at full load approaches 90%. >

Phase-shift modulation technique for the linerisation of analogue optical transmitters

A phase-shift modulation technique is described for the linearisation of light sources in fibre-optic transmission systems. A 25 dB reduction in the 2nd-harmonic distortion has been achieved in specially fabricated GaAlAs double-heterostructure light-emitting dioded (l.e.d.s) compared with the distortion levels typical of conventional l.e.d.s.

Support Programs for a Large-Scale Computer Production Control Project

Training for computer center operators, design engineers, and maintenance personnel; equipment testing to locate design deficiencies; acceptance personnel; equipment testing to locate design deficiencies; acceptance testing to insure equipment quality and to minimize installation time; and programmed preventive maintenance--these are programs that have been programmed preventive maintenance--these are programs that have been instituted by one major company to assure equipment reliability and data integrity in its computer production control system. Introduction In four of its five operating divisions, Exxon Company, U.S.A. (a Division of Exxon Corporation) has instituted a Computer Production Control (CPC) program, using identical computer centers and program, using identical computer centers and program systems to monitor and control oil and gas program systems to monitor and control oil and gas producing operations. The company presently uses producing operations. The company presently uses CPC to operate 26 fields with a total of 4,100 wells. The daily production of these fields is 315,000 bbl of oil and 1 Bcf of gas. CPC is being installed in eight additional fields, which will bring total CPC-operated production in 34 fields to about 375,000 B/D. production in 34 fields to about 375,000 B/D. The objectives of the CPC program are to increase the effectiveness of producing operations and to use manpower more efficiently. The system is designed to continuously monitor and feed back operating data to field personnel and to perform control functions, generate reports for regulatory purposes, and enter oil and gas volumes directly into the accounting system. The CPC system is a multicomponent operation, with equipment ranging in complexity from a two-position switch to a real-time process control computer. Maximum benefits can be derived from such a system only if (1) personnel responsible for the design, implementation, operation, and repair of the individual components are adequately trained; (2) measurement accuracy and reliability are verified before equipment is selected; (3) equipment is factory and field tested before it is accepted; and (4) programmed preventive maintenance is begun as soon programmed preventive maintenance is begun as soon as the system is implemented. Basic CPC Features In each division office there is a central process-control computer (Fig. 1), which is process-control computer (Fig. 1), which is programmed to monitor and direct field operations. programmed to monitor and direct field operations. The computer has a core memory of 48K and disc storage of more than 7,500K. The peripheral equipment in the computer center includes a high-speed line printer, two type-writers, and a card reader. A computer interface unit connects the computer with a communication network that links the computer with the CPC fields. Field equipment includes end devices located at the wells, metering sites, and central facilities (Fig. 2). These end devices generate volume information, measure tank levels, indicate alarms and status, and perform control functions. The field cabling connects perform control functions. The field cabling connects the end devices to the remote terminal unit, where volume information is accumulated, status/alarms are monitored, and analog (A/D) measurements are made. Upon request, this information is coded and transmitted from the remote terminal unit to the computer. The remote terminal unit also receives and decodes control and set-point (D/A) messages from the computer and transmits them to the appropriate end devices for execution. Phase shift modulation techniques are employed for transmission between the remote terminal unit and the computer interface unit. Data are transmitted at rates of 100 and 600 bits/sec. Communication between the computer center and field operating personnel is maintained through a man-machine input-output (I/O) system. JPT P. 31