Dual Phase Shift Research Articles

Multi-Objective Optimization Phase-Shift Control Strategy for Dual-Active-Bridge Isolated Bidirectional DC-DC Converter

The dual-active-bridge isolated bidirectional DC-DC converter (DAB-IBDC) is a crucial device for galvanic isolation, voltage conversion, power transfer, and buses connection in the DC power conversion systems. Phase-shift modulation is an effective method to improve DAB-IBDC performance. However, the phase-shift control strategies in the existing literatures mainly optimize the single characteristic of DAB-IBDC. In this paper, to realize a comprehensive optimization for DAB-IBDC performances, reducing high-frequency-link (HFL) reactive power, reducing current stress and improving efficiency simultaneously, a multi-objective optimization strategy based on dual-phase-shift (DPS) control is proposed. The power characterization, current stress and power loss in DAB-IBDC are investigated, and the control principle and framework of proposed multi-objective optimization DPS control strategy is described. The representative experiments in DAB-IBDC prototype are presented to verify correctness and superiority of the proposed strategy.

Design and implementation of DP-DQPSK DWDM transmission system by using direct detection

Designing a system that guarantees both the lower cost implantation, lower complexity on the receiver station side and higher data rate was an essential topic for several researchers recently, in which several methods and approaches were proposed to handle these problems individually and with the best overall outcome. In this work, these problems would be considered by designing and analyzing a novel system based on the combination of Dual Polarization Differential Quadrature Phase Shift Keying (DP-DQPSK) and Dense Wavelength Division Multiplexing (DWDM) technique and by using the Direct Detection (DD) technique. The system was designed with Optisystem software 18 and consist of 64 channels and each channel could transmit 14 Gbps of data rate. The channels 1,6,12,18,24,30,36,42,48,54,60 and 64 were selected as samples among all channels to be investigated and analyzed. Additionally, the proposed system was investigated based on different distances and different parameters of Quality Factor (QF) and Bit Error Rate (BER). The significant contribution of the proposed system is that using the DD would result in a no-required for reference wave and that will result in a less complex system and easier to implement. Results obtained indicate higher quality QF for the sampled channel and lower BER values. For instance, the average QF obtained were in the range of 6.75-8.36 dBm and 6.77-8.35 dBm for data 1 and 2 respectively, which indicates the reliability and efficiency of the proposed system by considering all results obtained from distance variation were above the minimum threshold

A type of piecewise and modular energy storage topology achieved by dual carrier cross phase shift SPWM control

This paper proposes a novel type of piecewise and modular energy storage topology. Compared to the modular multilevel converter (MMC), the proposed topology is not only different in structure but also in concept. Firstly, the capacitors within the submodules of MMC are all replaced by lithium batteries, which can avoid the voltage imbalance among capacitors and provide a deep connection between MMC and energy storage. What's more, the micro-unit concept is adopted to break the whole batteries within MMC into parts for each submodule by increasing the number of submodules to an extremely high level, which turns it into a novel microelement-based energy storage device. Due to the characteristics of the proposed topology, dual carrier cross-phase shift sinusoidal pulse width modulation (DCCPS-SPWM) is also proposed. With the help of DCCPS-SPWM, the proposed topology has the advantages of simple structure, easy to control, fewer total modules with the same output level, high fault tolerance, easy to detect and locate faults. The operating modes with four energy storage units per bridge arm are well analysed and extended to the case of N units. The double-Fourier analysis is performed on the output voltage waveform, so that the harmonics of the output voltage with DCCPS-SPWM can be clearly understood. Finally, the feasibility of the proposed topology and its control are verified by both simulation and experimental results.

DAB Based DC-DC High Frequency Link PET for Interconnecting MVDC-LVDC Grids

This paper proposes dual active bridge (DAB) based high frequency power electronic transformer (PET) for interconnecting medium voltage dc (MVDC) and low voltage dc (LVDC) grids for dc power distribution. The above proposed concept works on dual active phase shift principle and square wave HF modulation technique for bidirectional power transfer. Compared to the traditional dc transformer scheme, The proposed power electronic transformer (PET) can disconnect from LVDC distribution grid effectively as a dc breaker when a short circuit fault occurs in the distribution grid. The isolated DC-DC PET topology with a wide range of voltage conversion ratio is useful for High Voltage DC tapping. The DAB based on switched capacitor is connected to the medium voltage DC side and acts as an inverter. The proposed topology has the ability to transfer higher power, and lower circulating power, lower high frequency link voltage, and RMS current and peak values with the same transmission power in the MVDC side. This paper analyzes the topology, voltage and power characterization, control strategy in detail. Increase in the intermediate AC frequency will reduce the size of the transformer and other passive elements significantly in the circuit. The theoretical analysis is supported by MATLAB simulation.

Building Common-Mode Analytical Model for Dual Active Bridge Incorporating With Different Modulation Strategies

The modulation strategies of dual active bridge (DAB) including single phase-shift (SPS), dual phase-shift (DPS), and triple phase-shift (TPS) have been proposed to optimize the efficiency, eliminate the reactive power, and release the current stress. While the previous literature focuses on the accurate loss model in steady states or small-signal analysis for dynamic response, the common-mode (CM) model has been largely ignored. The main contribution of this article then is to propose an analytical CM model for DAB, which considers the CM parasitic capacitors including those of grounded heatsink and transformer windings. Based on such model, the CM performance is compared among different modulation strategies. The impact of two H-bridge on the input and output CM voltage has been addressed. A prototype based on SiC devices is used to verify the proposed analytical mode under SPS, DPS, and TPS. It is found that while TPS improves the light-load efficiency it introduces the worst CM noise. Influence of the ZVS current setting on the CM performance is also discussed.

A Cost-Effective Solution for Testing High-Performance Integrated Circuits

Testing of high-speed integrated circuits that enable 100-Gb Ethernet is a complex and expensive proposition. It becomes increasingly difficult to carry out measurements with probes if the test chip’s pad count is very high. A full-fledged packaging solution to test a chip requires a lot of resources and incurs a considerable cost. Other approaches, such as using flip-chip-on-board, prove to be expensive as well. On-board electrical interconnects, if appropriately designed, can be used with wire-bonded dies to perform high-speed measurements using ordinary methods. This article discusses the design and development of a platform to test a high-speed equalizer chip designed for the 100-Gb/s dual polarization-quadrature phase shift keying-based optical links. It also shows how careful optimization of the test platform addressing the aspects of signal delivery from connectors to chip pads through broadband transmission lines and bond-wire transitions and thermal management facilitates the use of low-cost methods to test high-performance chips. Detailed descriptions of the test platform and its validation using $S$ -parameter measurements and the experimental results with an optical system are also presented.

Improved hybrid current modulation for bidirectional power flow of single-stage dual active bridge AC/DC converter

In this paper, an improved hybrid current modulation (iHCM) method for bidirectional power flow operation of dual active bridge (DAB) ac/dc converter is proposed. In this method, trapezoidal (TZM) and triangular (TRM) current modulations are performed together in a grid period to obtain distortionless grid current with forming minimum RMS current in the transformer of DAB. This study put forward a detailed analysis of the mode changing instants (between TRM and TZM), RMS and peak current values of the transformer and required magnetic core sizes. Furthermore, the iHCM is compared in analysis and simulations by the variable switching frequency dual phase shift modulation (VSF DPSM) method that have small RMS current advantage in the vicinity of nominal output power. According to the analysis, the iHCM, unlike the VSF DPSM, can operate over a wide range of transformer turn ratio (or over the wide range of ac peak voltage/reflected dc voltage, λ) without increasing the size of transformer, and can provide small RMS currents at light loads as it has no nonactive (circulating) current. The theoretical analysis is validated with a downsized 250 W experimental prototype.

A T-type dual active bridge with symmetrical configuration for solid state transformer

ABSTRACT Solid-state transformer has been a major area of research in recent years because of its multifunctionality as compared to conventional low-frequency transformers. Bidirectional isolated dual-active bridge is an important component in power electronic transformer. When conventional control scheme such as single-phase shift and dual-phase shift are used, they have high current stress and thus reducing the system efficiency because of high circulating power. Furthermore, they have high across switches, with only one or two degrees of freedom. It confines its ability to regulate power flow. In this paper, a new T-type dual-active bridge with symmetrical configuration is proposed, having five degrees of freedom which not only improves its ability to regulate power flow, but also reduces across switches due to increase in voltage levels, and has lesser current stress. It reduces the circulating power which improves the efficiency of system. Detailed analysis to establish the relation between controllable variables with current and power flow is given in this paper. Performance of the proposed converter has been verified via simulation and experimental results.

Performance Evaluation of Modulation Techniques in Single-Phase Dual Active Bridge Converters

This research presents a thorough comparison of different modulation techniques employed in dual active bridge (DAB) converters. The performance of a DAB converter is essentially affected by the modulation technique and the operating point, including power level, input, and output voltages. A deep understanding of different modulations is required to achieve the highest performance in the entire operating range. Therefore, this paper focuses on comparing different modulation techniques over a DAB converter's operating span. The comparison results provide guidance to apply the correct modulation in certain working areas keeping the converter on top of its performance. Moreover, the paper proposes an optimization solution with distinct objective functions adoptable in DAB converters to reduce power loss. The proposed optimization approach outperforms the existing solutions regarding generality and simplicity. The optimization associates with the modulation techniques that include more than one degree of freedom, such as extended phase shift (EPS) and dual-phase shift (DPS). The proposed optimization and the investigated modulation techniques are evaluated in terms of the converter's efficiency, current stress, and backflow power. The evaluation is realized by the simulation study of a 10 kW 800V/500V SiC-based DAB converter in PLECS software.

Research on Marine DAB bidirectional DC converter based on DPS

This paper takes the application of bidirectional DC-DC converter in Marine hybrid power system as the background, the problems of high reflow power and current stress in dual active bridge converter under traditional phase shift control are studied in this paper. Based on the dual phase shift control strategy, the power transmission optimization algorithm model is analyzed and derived, and a control method for optimizing mode switching is proposed. The optimized control algorithm is validated by Matlab/Simulink simulation experiment. The results show that the reflow power and current stress optimization control algorithm can effectively reduce the reflow power and the current stress of the converter, so as to improve the operation performance of DAB converter in high-power ship hybrid power system.

Development of 32-GBaud DP-QPSK free space optical transceiver using homodyne detection and advanced digital signal processing for future optical networks

Free space optical (FSO) communication provides the capacity to deliver high-speed digital data links into the far off and rural factions where topography, set-up cost or groundwork safety pose acute barriers to deployment. The challenges in any FSO system are the transmission impairments and space loss which deteriorate the link performance. This article deals with the design and analysis of a single channel Gray-coded dual polarization-quadrature phase shift keying (DP-QPSK) based FSO communication system with balanced homodyne detection (BHD) and digital signal processing (DSP). We have implemented a series of high-level digital impairment compensation algorithms strategically between the BHD and signal retrieval stages to mitigate the amplitude and phase noise, and compensate for free-space loss. The proposed system exhibits a 3 dB greater receiver sensitivity using optical homodyne detection compared to heterodyne detection. The system performance has been numerically evaluated with regard to bit error rate (BER $$\le 2\times {10}^{-3},$$ i.e. FEC limit), error vector magnitude (EVM), and constellation diagram based on OptiSystem V.16 photonic software. Furthermore, we investigate the joint BER and EVM performance of the proposed system under the influence of launched optical power, laser linewidth, and beam divergence. We obtain the transmission of 32 GBaud DP-QPSK data bearing optical signal up to a link distance of 2.65 km at 128-Gb/s data rate, and an optical signal-to-noise ratio penalty lower than 2.5 dB compared to the back-to-back case. The outcomes of this research demonstrate direct practical relevance and could therefore form the basis for the implementation of next-generation optical wireless networks.

Optical Performance Monitoring in Mode Division Multiplexed Optical Networks

This article considers, for the first time, optical performance monitoring (OPM) in few mode fiber (FMF)-based optical networks. 1-D features vector, extracted by projecting a 2-D asynchronous in-phase quadrature histogram (IQH), and the 2D IQH are proposed to achieve OPM in FMF-based network. Three machine learning algorithms are employed for OPM and their performances are compared. These include support vector machine, random forest algorithm, and convolutional neural network. Extensive simulations are conducted to monitor optical to signal ratio (OSNR), chromatic dispersion (CD), and mode coupling (MC) for dual polarization-quadrature phase shift keying (DP-QPSK) at 10, 12, 16, 20, and 28 Gbaud transmission speeds. Besides, M-ary quadrature amplitude modulation (M = 8 and 16) is considered. Also, the OPM accuracy is investigated under different FMF channel conditions including phase noise and polarization mode dispersion. Simulation results show that the proposed 1D projection features vector provides better OPM results than those of the widely used asynchronous amplitude histogram (AAH) features. Furthermore, it has been found that the 2D IQH features outperform the 1D projection features but require larger number of features samples. Additionally, the effect of fiber nonlinearity on the OPM accuracy is investigated. Finally, OPM using the 2D IQH features has been verified experimentally for 10 Gbaud DP-QPSK signal. The obtained results show a good agreement between both simulation and experimental findings.

Modular Equalization System Using Dual Phase-Shift-Controlled Capacitively Isolated Dual Active Bridge Converters to Equalize Cells and Modules in Series-Connected Lithium-Ion Batteries

Conventional lithium-ion battery (LIB) packs comprising series-connected modules need cell and module equalizers separately, resulting in increased system complexity. This article proposes a modular equalization system using dual phase-shift (DPS)-controlled capacitively isolated dual active bridge (CIDAB) converters. Each module contains an intramodule CIDAB converter that performs direct cell-to-cell equalization. Meanwhile, switching legs of adjacent modules' CIDAB converters are connected through an LC tank to configure an intermodule CIDAB converter that equalizes module voltages. The switching legs of CIDAB converters are utilized for both the intra- and intermodule equalizers, achieving the simplified system. Based on the proposed DPS control, the PS angles of both the intra- and intermodule CIDAB converters are manipulated to perform cell and module equalization. The prototype of the proposed modular equalization system for two LIB modules, each consisting of 12 cells was built and tested. Cells and module voltages in the proposed system were sufficiently equalized, demonstrating the efficacy of the proposed equalization system.

Comprehensive energy efficiency analysis of series hybrid electric vehicles with dual-phase-shift-controlled DC-DC converter

By considering converter fundamental operating principles, the paper first derives a complete set of analytic expressions of the overall power losses of a conventional Dual Active Bridge (DAB) bi-directional DC-DC converter under Dual Phase Shift (DPS) control. Expressions for conduction and switching losses in the electronic devices acting as the converter switches, and copper and core losses in the isolation transformer, are derived and accounted for in the DC-DC converter model. DPS control involves many more converter operating conditions, in comparison to the more common single-phase-shift (SPS) control, which makes the analytic power loss characterization of a DPS-controlled converter an arduous task. Subsequently and by employing the derived analytic converter power loss model with exemplary parameter values, the paper analyzes the efficiency of a high-fidelity full hybrid electric vehicle (HEV) model that includes a DAB DC-DC converter, under a wide range of realistic driving conditions and converter operation, including low- to high-speed driving, and converter DPS operation. Two popular hybrid powertrain energy management schemes, the Thermostat and Power Follower control strategies, are used to simulate the vehicle model to reinforce the range of realistic vehicle operating conditions. The results show that in series HEV applications more accurate modeling of DC-DC converter models than conventional constant efficiency models is required to predict converter losses, and also the fidelity in the characterization of converter losses can have a significant impact on the vehicle fuel consumption prediction.

Comparison of DAB Converter with Simple, Dual, Extended and Triple Phase Shift for Electric vehicle Charging Applications

Comparison of DAB Converter with Simple, Dual, Extended and Triple Phase Shift for Electric vehicle Charging Applications

Study of Dual Active Bridge With Modified Modulation Techniques for Reduced Link Current Peak Stress and Harmonics Losses in Magnetics

High-frequency-link power-conversion is gaining popularity in recent days due to reduction of the size and weight of the converters for various applications. The performance of the dual active bridge heavily depends on the nature of modulation strategy used and on the loading conditions. Look-up table (LUT) based output power and output voltage dependent modulation strategies to investigate the peak current stress and harmonics in high-frequency link current is proposed in this article. The modulator is, thus, simple to implement. The peak stress, the harmonics (total demand distortion) in link current, and associated losses due to the proposed techniques are compared in four main cases, namely, first, single-phase shift, second, dual-phase shift, third, triple phase shift, and, fourth, modified phase shift (MPS)-I, -II, and -III. In MPS-I, weighted aggregate of harmonic currents minimization including fundamental component is carried out to achieve the minimum conduction losses in the magnetic elements. The same method is extended for minimizing the peak-to-peak ripple in the link current as MPS-II. In MPS-III, the desired total demand distortion in the ac-link current is enforced. The variation of voltage transfer ratio between input and output is taken into consideration using two-dimensional (2-D) LUT. Moreover, the requirement of 2-D LUTs are eliminated by using suitable curve-fitting exercise for the output load voltage variation and 1-D LUTs of coefficients. A detailed simulation study, associated mathematical analysis of the methods adopted and experimental verification are presented from 1 kW prototype.

Performance evaluation of 6.4 Tbps dual polarization quadrature phase shift keying Nyquist-WDM superchannel FSO transmission link: Impact of different weather conditions

This work reports the development of an ultra-high capacity Nyquist-wavelength division multiplexing (WDM) superchannel based free space optics (FSO) transmission link. In the proposed link, 32 independent wavelength channels are multiplexed, each carrying 200 Gbps dual polarization-quadrature phase shift keying (DP-QPSK) data with 60 GHz channel spacing yield net transmission rate of 6.4 Tbps with spectral efficiency of 3.33 bits/s/Hz. The performance of the proposed FSO link has been numerically investigated under the influence of dynamic weather conditions such as clear, haze, rain, and fog conditions. Also, we investigate the BER performance of the proposed link under the influence of beam divergence angle. Further, we compare the proposed FSO link performance with previous works reported in the literature showing the superiority of our proposed link. The simulative investigation of the proposed link was carried out using Optisystem version 14 which is a powerful tool for the development and investigation of optical networks.

Soft-switching and low conduction loss current-fed isolated bidirectional DC–DC converter with PWM plus dual phase-shift control

In battery energy storage systems, the battery and DC bus voltages vary greatly. This makes it difficult for the battery storage converter to maintain high efficiencies under all circumstances. A current-fed isolated bidirectional DC–DC converter is presented in this paper. This converter contains two series transformers, two conventional current-fed half-bridges at the battery side and two half-bridges at the DC bus side. PWM plus dual phase shift modulation with equal duty cycles and voltage-matched control is applied to ensure ZVS of all the switches and low conduction losses. The average and backflow power transmission equations and soft-switching conditions for all of the operation modes in the full operation range are analyzed comprehensively in this paper. Then six recommended modes are addressed based on the above analyses. Moreover, the control scheme and hardware design guidelines are addressed. Finally, the above theoretical analyses and control strategy are verified by experimental results.

An Improved Modulation Scheme of Active Commutated Current-Fed Bidirectional dc/dc Converter

Active commutated or naturally clamped techniques have emerged as a new solution to achieve wide range soft-switching and eliminate the necessity of active clamping circuit of current-fed bidirectional dc/dc converter. Multiple typical modulation schemes have been proposed, which include single phase-shift (SPS) modulation, dual phase-shift (DPS) modulation, and discontinuous current SPS (DCSPS) modulation. DCSPS provides the lowest circulating current compared with prior two modulations, but it suffers from the problem of resonance and high peak current at partial loads. This article proposes a DCDPS modulation based on the existing modulations. The duty cycles of the two legs on the high-voltage side are controlled to be unsymmetrical to solve the current resonance problem in DCSPS. Extra phase shift is introduced to achieve much lower circulating current at wide range load conditions. Zero current switching (ZCS) of primary switches and zero voltage switching (ZVS) of secondary switches can be achieved over wide input range and wide load range. A 250-W laboratory converter prototype has been built. Experimental results are presented to validate the analysis and design.

Securing Full-Power-Range Zero-Voltage Switching in Both Steady-State and Transient Operations for a Dual-Active-Bridge-Based Bidirectional Electric Vehicle Charger

Dual-active-bridge (DAB) circuit is an excellent candidate for a high-efficiency, high-power density, and bidirectional electric vehicle charger. Unlike resonant circuits employing auxiliary inductors and capacitors, DAB minimizes the usage of passive components. The challenge, however, lies in the difficulty of securing zero-voltage switching (ZVS), particularly at light-to-medium load when using the conventional single-phase-shift (SPS) control. This is of utmost importance not only for the sake of the efficiency, but also for minimizing the switch-bridge crosstalk caused by the hard switching-on, thereby enhancing the system reliability. Although dual-phase-shift (DPS) and triple-phase-shift (TPS) can be the answer, they do introduce side effects such as larger switching-off current. This article systematically integrates SPS, DPS, and TPS to maximize full-power ZVS range for both steady state and transient operations in EV chargers. This article plots ZVS boundaries over the full power range, categorizes all operations into nine modes, and proposes a smooth transition method among all operation modes. Dead band is also incorporated in the ZVS boundary setting. Experimental results on a SiC-based charger validate the effectiveness of this method of widening ZVS range for output voltage of 200-450 Vdc and power of 0-20 kW, achieving smooth transitions among various operation modes, and suppressing the switch crosstalk, thereby securing high charger reliability.