Single Phase Shift Research Articles

Photonic microwave frequency down-converter with image rejection via carrier suppression single sideband modulation and photonic microwave phase shift

ABSTRACTThe combined use of carrier suppression single sideband (CS-SSB) modulation and photonic microwave phase shift is described and analyzed to realize microwave frequency down-conversion with image rejection. Based on the idea of phase cancellation, the image signals have identical amplitude and opposite phase to be suppressed, while the useful signals have identical amplitude and phase through an electrical 90 degree hybrid to be strengthened. The approach is investigated in theory and demonstrated using simulation. It is shown that the power of the useful IF signal is nearly 60 dB larger than that of the image IF signal. Besides, the zero-IF receiving capability of our approach has been also investigated when a modulated RF signal with different format input. The 2.5 Gbit/s RF modulated signals centred at 15 GHz with quadruple-, 8-, 16- phase shift keying (QPSK, 8PSK, 16PSK), and 16-quadrature amplitude modulation (16QAM) formats are successfully demodulated with good error vector magnitudes (EVMs) and constellation diagrams in wide power range of input RF carrier.

A Hybrid Modulation Strategy Providing Lower Inductor Current for the DAB Converter With the Aid of DC Blocking Capacitors

For the dual active bridge converter, the single phase shift (SPS) modulation strategy is simple and effective for controlling the transmission power. However, when the voltage varies widely, it is hard to realize soft switching and the circulating power increases dramatically, which results in the increased current stress and reduced efficiency. Thus, a hybrid modulation strategy is proposed in this article, whose main idea is to introduce a voltage offset across the dc blocking capacitors in both sides, and the converter can switch between different operating modes to lower the inductor current according to different operating conditions. Operational principle of the proposed modulation is introduced, and the normalized root-mean-square values of the inductor current in different working modes are derived mathematically, which leads to the selection criterion among different operating modes. The proposed scheme retains the simplicity of the conventional SPS strategy and improves the efficiency over wide voltage range and wide load range without complicating the topology structure. Finally, the performance of the proposed modulation is verified by the experimental results.

Instantaneous Flux and Current Control for a Three-Phase Dual-Active Bridge DC–DC Converter

The three-phase dual-active bridge converter is a promising topology for the high-power high-frequency dc–dc conversion, due to the soft-switching capability and inherent galvanic isolation. With the state-of-the-art instantaneous current control (ICC) based on the single phase-shift (SPS) operation, a bidirectional power flow can be controlled dynamically between two dc ports without inducing overshoots in the transformer currents. However, a transient dc-bias flux may still occur in the transformer, which may cause the transformer core saturation in the dynamic operation such as start-up, power- off , and abrupt load changes. To analyze and address this issue, this paper presents a set of model-based methods to avoid inducing the dc-bias flux in various transient situations. The proposed double-side SPS operation could nullify the dc-bias flux in abrupt load changes and even instant power-flow reversals. Furthermore, the soft-magnetizing and soft-demagnetizing techniques are presented to eliminate the initial and residual dc-bias flux during start-up and power- off instantly. The proposed flux control method can be integrated with the ICC. Thus, the transformer magnetizing flux and the winding currents can be controlled simultaneously and instantaneously in transient situations. Simulations and experiments on a down-scaled hardware prototype validate the effectiveness of the proposed methods.

Wireless communications with programmable metasurface: Transceiver design and experimental results

Metasurfaces have drawn significant attentions due to their superior capability in tailoring electromagnetic waves with a wide frequency range, from microwave to visible light. Recently, programmable metasurfaces have demonstrated the ability of manipulating the amplitude or phase of electromagnetic waves in a programmable manner in real time, which renders them especially appealing in the applications of wireless communications. In this paper, we present the fundamental principle of applying programmable metasurface as transmitter for wireless communications. Then, we establish a prototype system of meta-surface-based transmitter to conduct several experiments and measurements over the air, which practically demonstrate the feasibility of using programmable metasurfaces in future communication systems. By exploiting the dynamically controllable property of programmable metasurface, the design, implementation and experimental evaluation of the proposed metasurface-based wireless communication system are presented with the prototype, which realizes single carrier quadrature phase shift keying (QPSK) transmission over the air. In the developed prototype, the phase of the reflected electromagnetic wave of programmable metasurface is directly manipulated in real time according to the baseband control signal, which achieves 2.048 Mbps data transfer rate with video streaming transmission over the air. In addition, experimental result is provided to compare the performance of the proposed metasurface-based architecture against the conventional one. With the slight increase of the transmit power by 5 dB, the same bit error rate (BER) performance can be achieved as the conventional system in the absence of channel coding. Such a result is encouraging considering that the metasurface-based system has the advantages of low hardware cost and simple structure, thus leading to a promising new architecture for wireless communications.

Flux control modulation for the dual active bridge DC/DC converter

This paper introduces a modulation technique for the single-phase dual active bridge (DAB) in which the switching frequency and transformer flux linkage are modulated to achieve improved power transfer characteristics and reduced converter losses. By analysing the DAB, it is noticed that in the traditional single phase shift (SPS) modulation, the transformer flux linkage decreases with increasing power. The proposed flux control modulation (FCM) counteracts this decrease and aims to keep the transformer utilisation constant on the whole load range by a reduction in switching frequency. This has two effects: first, the reduced frequency substantially lowers switching losses and second, the power transfer characteristic of the DAB is linearised, facilitating the control of this converter. The new modulation technique is validated by simulation.

Wireless communications with programmable metasurface: Transceiver design and experimental results

Metasurfaces have drawn significant attentions due to their superior capability in tailoring electromagnetic waves with a wide frequency range, from microwave to visible light. Recently, programmable metasurfaces have demonstrated the ability of manipulating the amplitude or phase of electromagnetic waves in a programmable manner in real time, which renders them especially appealing in the applications of wireless communications. To practically demonstrate the feasibility of programmable metasurfaces in future communication systems, in this paper, we design and realize a novel metasurface-based wireless communication system. By exploiting the dynamically controllable property of programmable metasurface, we firstly introduce the fundamental principle of the metasurface-based wireless communication system design. We then present the design, implementation and experimental evaluation of the proposed metasurface-based wireless communication system with a prototype, which realizes single carrier quadrature phase shift keying (QPSK) transmission over the air. In the developed prototype, the phase of the reflected electromagnetic wave of programmable metasurface is directly manipulated in real time according to the baseband control signal, which achieves 2.048 Mbps data transfer rate with video streaming transmission over the air. Experimental result is provided to compare the performance of the proposed metasurface-based architecture against the conventional one. With the slight increase of the transmit power by 5 dB, the same bit error rate (BER) performance can be achieved as the conventional system in the absence of channel coding. Such a result is encouraging considering that the metasurface-based system has the advantages of low hardware cost and simple structure, thus leading to a promising new architecture for wireless communications.

Topologies and Control Schemes of Bidirectional DC–DC Power Converters: An Overview

Bidirectional DC-DC power converters are increasingly employed in diverse applications whereby power flow in both forward and reverse directions are required. These include but not limited to energy storage systems, uninterruptable power supplies, electric vehicles, and renewable energy systems, to name a few. This paper aims to review these converters from the point of view of topology as well as control schemes. From the point of view of topology, these converters are divided into two main categories, namely non-isolated and isolated configurations. Each category is divided into eight groups along with their respective schematics and a table of summary. Furthermore, the common control schemes and switching strategies for these converters are also reviewed. Some of the control schemes are typically applied to all DC-DC power converters such as PID, sliding mode, fuzzy, model predictive, digital control, etc. In this context, it should be noted that some switching strategies were designed specifically for isolated bidirectional DC-DC converters in order to improve their performance such as single phase shift, dual phase shift, triple phase shift, etc. The features of each topology and control scheme along with their typical applications are discussed, in order to provide a ground of comparison for realizing new configurations or finding the appropriate converter for the specific application.

A single phase shift-based isolated bidirectional DC-DC converter for bidirectional energy transfer in DC-microgrid with identification of optimum operating zone

In the modern times, the pertinence of a single power electronics conversion system used in DC microgrids for facilitating energy transfer between energy generating systems and storage elements with inherent bidirectional capability has increased significantly. A dual active bridge (DAB) converter having two DC-AC converters connected back to back through a high frequency transformer is used as a power electronics conversion system for obtaining highly efficient bidirectional power conversion. In this paper, performance of DAB converter with single phase shift (SPS) is evaluated with solar photovoltaic cell on high voltage DC-bus and battery on the low voltage DC-bus. Linear load is connected in this system at the high voltage DC-bus. A step variation in load is applied and at this instant the power flows from the batteries to supply the increased load demand. Optimal operating range of converter along-with efficiency is obtained.

Model Predictive Control With Power Self-Balancing of the Output Parallel DAB DC–DC Converters in Power Electronic Traction Transformer

This paper focuses on the output parallel dual-active-bridge (DAB) dc–dc converters in power electronic traction transformers. A model predictive control with current-stress-optimized (MPC-CSO) scheme based on dual-phase-shift (DPS) control is proposed to improve the dynamic performance, balance the transmission power, and realize the current-stress optimization. The dynamic behavior of output voltage in the next horizon is predicted accurately under the input voltage fluctuation and load disturbance conditions by developing the prediction model. In addition, the proposed MPC-CSO scheme can track the output voltage with the desired value directly with no overshoot during the start-up process. Combining the MPC and CSO scheme, the fast dynamic response and high-efficiency performance of DAB converters can be achieved simultaneously, and the transmission power of each DAB cell can be self-balanced. Finally, three control schemes consisting of traditional voltage closed-loop control with single phase shift, traditional CSO control with DPS, and MPC-CSO with DPS schemes are compared in a scale-down three DAB dc–dc converter cells experimental prototype by using TMS320F28335+FPGA_6SLX45 as core controller. Extensive experimental results have verified the excellent performance of the proposed MPC-CSO scheme and associated analysis in this paper.

A Multiple-Phase-Shift Control for a SiC-Based EV Charger to Optimize the Light-Load Efficiency, Current Stress, and Power Quality

An ac/dc + dual-active-bridge (DAB) circuit was found as one solution for the high-efficiency and high-power-density electric vehicle charger. One control option is to let ac/dc part only convert the grid voltage to a double-line-frequency folded sine wave, yielding near-zero switching loss of the ac/dc part and leaving the DAB stage to control both power factor and power delivery. Such a zero-to-peak input voltage and wide-range output voltage can obstruct the zero-voltage switching (ZVS) for the DAB stage, which is a must for high-efficiency applications even with SiC devices. While the conventional single-phase shift loses ZVS at light load, and the variable-switching-frequency dual phase shift (DPS) creates the grid-current distortion at the light load, this paper employs multiple-phase-shifts (MPS) control, which essentially is a fixed-switching-frequency triple-phase-shift (TPS) control at light-load conditions and jumping to DPS at medium- and heavy-load conditions. While the TPS control will sacrifice the system efficiency by introducing the circulating current, a multiobjective optimization is employed to optimize the current stress and efficiency simultaneously, using the database of the double-pulse-test result. Experimental results on a SiC-based charger validated the effectiveness of the proposed control algorithm, that is: 1) high efficiency(>97%) at heavy load (7.2 kW); 2) smooth sinusoidal current without bumps at zero-crossing points from the whole-load range; and 3) the smooth transition between the heavy load and light load.

3-D Polarized Modulation: System Analysis and Performance

In this paper we present a novel modulation technique for dual polarization communication systems, which reduces the error rate compared with the existent schemes. This modulation places the symbols in a 3D constellation, rather than the classic approach of 2D. Adjusting the phase of these symbols depending on the information bits, we are able to increase the bit rate. Hence, the proposed scheme conveys information by selecting both polarization state and the phase of radiated electromagnetic wave. We also analyse the performance of 3D Polarized Modulation (PMod) for different constellation sizes and we obtain a curve of rate adaptation. Finally, we compare the proposed 3D PMod with other existing schemes such as single polarization Phase Shift Keying (PSK) and double polarization Vertical Bell Laboratories Layer Space-Time (V-BLAST), both carrying the same number of information bits. The results show that 3D PMod always outperforms all other schemes, except for low order modulation. Therefore, we can conclude that 3D PMod is an excellent candidate for medium and high modulation order transmissions.

Dual-Phase-Shift Control Scheme With Current-Stress and Efficiency Optimization for Wireless Power Transfer Systems

Traditional wireless power transfer (WPT) systems usually adopt the single-phase-shift (SPS) control method to maintain a constant output current or a constant output voltage for various applications. However, the current-stress on one side is much higher than that of the other side especially under operating conditions with high voltage conversion ratio and light-load. This phenomenon actually can be proven by the established mathematical model of the current-stress of WPT systems using SPS control. This large current-stress will damage power devices and lower the efficiency of WPT systems. In addition, it will result in an increase of system total cost because of the need for the devices with the higher volt-ampere rating. A control strategy based on dual-phase-shift control is developed for WPT systems with an active rectifier to reduce the maximum value of current-stresses on both sides as well as to maintain a constant output voltage or current. Consequently, the system efficiency can be improved compared to traditional WPT systems with SPS control. A scaled-down experimental prototype is constructed to verify the effectiveness of the proposed WPT topology and the control method. Experimental results show that the proposed method can reduce the maximum current-stress significantly and improve the system efficiency compared to traditional WPT systems under SPS control.

An Improved Generalized Average Model of DC–DC Dual Active Bridge Converters

Improvements are proposed for generalized average models of dual active bridge (DAB) converters. Generalized average modeling involves a tradeoff between accuracy and tractability. To maintain an acceptable level of complexity, existing DAB models are derived using a first harmonic approximation. These models provide accurate small-signal representations, but are limited as large-signal analysis tools due to persistent steady-state error. This study proposes a modeling framework that provides accurate large and small-signal models without significant increases in the overall complexity. The framework describes DAB operation with a triple phase shift modulation, and is easily simplified for single, dual, or extended phase shift modulation schemes. The special case of a single phase shift modulation, which experiences the most significant large-signal error, is given additional consideration. The framework is applied to open and closed-loop operation, and both large- and small-signal models are discussed. Models are validated in simulation and hardware experiments using a small scale DAB prototype.

Burst-Mode Digital Signal Processing That Pre-Calculates FIR Filter Coefficients for Digital Coherent PON Upstream

This paper proposes a burst-mode digital signal processing architecture for digital coherent time-divisionmultiplexed passive optical network (PON) upstream transmission, wherein two key advances are introduced to shorten the preamble length of burst signals required to complete adaptive equalization, as performed by a constant modulus algorithm: tap coefficients of a finite impulse response (FIR) filter are pre-calculated in the optical network unit (ONU) discovery process, and the feed-forward state of polarization compensation is employed before adaptive equalization. The bit error rate performance attained by the proposal is experimentally evaluated; successful burstmode coherent detection with a high sensitivity of -44.7 dBm is demonstrated for 20 Gbit/s single polarizationquadrature phase shift keying burst signals transmitted over a 40 km single mode fiber, even with the use of a short preamble of 1.3 μs, which meets the optical power specifications required for a 512-way split system. The proposal utilizes register request signals whose preamble is longer than those used in current PON systems to optimize the tap coefficients of the FIR filter, which may disrupt smooth ONU registration in high-splitting-ratio systems. To evaluate this impact, numerical calculations based on the Monte Carlo method are conducted, and the results show that the time required to complete the registration of 512 ONUs is just 40 s or so.

Widen the zero-voltage-switching range and secure grid power quality for an ev charger using variable-switching-frequency single-dual-phase-shift control

Compared to conventional electrical-vehicle(EV) on-board chargers utilizing a front-end Power-Factor-Correction(PFC) + an isolated DC/DC converter, which limits the wall-to-battery efficiency to ~94%, a new control strategy using variable switching frequency(VSF) and variable phase shifts frees the PFC stage thereby getting rid of the DC link capacitor and further increasing the system efficiency and power density. The challenge is to secure zero-voltage-switching (ZVS) turn-on for all switches within the full-power range. In this paper a novel VSF single-dual-phase-shift(SDPS) control strategy is proposed, which consists of three control freedoms, i.e., two phase shifts and one variable switching frequency to secure ZVS and achieve PFC simultaneously. ZVS boundaries are pictured and compared among single-phase-shift(SPS), dual-phase-shift(DPS) and the proposed single-dual-phase-shift(SDPS) control. Simulation results and experimental validation through a level-2 EV on-board charger indicate that by using the proposed SDPS control, both ZVS and PFC are secured not only for the heavy load but also for the light load, without sacrificing the system efficiency.

Review and comparative analysis of dual active bridge isolated DC to DC converter with different control techniques

Bidirectional energy transfer capability is the central part of a lot of modern power conversion systems. Preferably, for reduction of size, weight and cost, these systems use a single high efficiency power electronic conversion system. A dual active bridge converter having two DC-AC converters connected back to back through an AC inductor/transformer is a common topology used for obtaining high efficiency bidirectional power conversion. Some characteristic features of the DAB converter topology are bidirectional power flow capability, inherent soft switching, high power density, high efficiency, galvanic isolation and low number of passive components. In this paper, circuit operation, design, and comparison of efficiency, switch stress, and closed-loop operation of a dual active bridge (DAB) converter for step load variations are discussed and simulated, dual active bridge converter is simulated with closed-loop controller and efficiency is obtained in simulation. Also, switch stress is calculated in simulations. Various control strategies like single phase shift, dual phase shift, extended phase shift and triple phase shift are compared and respective waveforms are shown. Dual active bridge is simulated in MATLAB in single phase shift, extended phase shift, dual phase shift and triple phase shift modes and waveforms are obtained via simulations.

Dynamic and static performance optimization of dual active bridge DC-DC converters

High efficiency and fast dynamic response are two main control objectives for dual active bridge (DAB) DC-DC converters. Traditional extended phase shift (EPS) control can significantly enhance the conversion efficiency of DAB DC-DC converters by reducing current stress; however, it cannot fulfill fast dynamic response requirements. In this paper, a novel hybrid control scheme consisting of EPS control and direct power control (DPC), named as EPS-DPC, is proposed. EPS-DPC control has salient features in both efficiency and dynamic performance. In order to verify the outstanding performance of the proposed EPS-DPC scheme, an experimental comparison was carried out on a scale-down DAB DC-DC converter among several control strategies, including single phase shift control with traditional voltage-loop (SPS-TVL), EPS control with traditional voltage-loop (EPS-VTL), and EPS-DPC. Experimental results have been high consistent with theoretical analysis, and verified these advantages of the proposed EPS-DPC scheme.

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.

Fast Reconfigurable SOA-Based Wavelength Conversion of Advanced Modulation Format Data

We theoretically analyze the phase noise transfer issue between the pump and the wavelength-converted idler for a nondegenerate four-wave mixing (FWM) scheme, as well as study the vector theory in nonlinear semiconductor optical amplifiers (SOAs), in order to design a polarization-insensitive wavelength conversion system employing dual co-polarized pumps. A tunable sampled grating distributed Bragg reflector (SG-DBR) pump laser has been utilized to enable fast wavelength conversion in the sub-microsecond timescale. By using the detailed characterization of the SGDBR laser, we discuss the phase noise performance of the SGDBR laser. Finally, we present a reconfigurable SOA-based all-optical wavelength converter using the fast switching SGDBR tunable laser as one of the pump sources and experimentally study the wavelength conversion of the single polarization quadrature phase shift keying (QPSK) and polarization multiplexed (Pol-Mux) QPSK signals at 12.5-Gbaud. A wide tuning range (>10 nm) and less than 50 ns and 160 ns reconfiguration time have been achieved for the wavelength conversion system for QPSK and PM-QPSK signals, respectively. The performance under the switching environment after the required reconfiguration time is the same as the static case when the wavelengths are fixed.

A Blended SPS-ESPS Control DAB-IBDC Converter for a Standalone Solar Power System

In sustainable energy applications, standalone solar power systems are mostly preferred for self-powered energy zones. In all standalone renewable power systems, batteries are still preferred as the common energy storage device. On the other hand, batteries are not applicable for high peak power demand applications because of their low power density. A supercapacitor is a preferable high-power density energy storage device for high peak power applications. A 2 kW, 50 kHz digital control dual active bridge isolated bi-directional dc-dc converter (DAB-IBDC) was developed for interfacing the supercapacitor bank in standalone solar power system. This paper proposes a blended SPS-ESPS digital control algorithm for a DAB-IBDC converter instead of using a traditional single-phase shift (SPS) control algorithm, which is commonly used for large input to output voltage varying applications. This proposed blended SPS-ESPS control algorithm achieved high power conversion efficiency during a large input to output voltage variation, over a traditional phase shift control algorithm by reducing the back-power flow and current stress in a circuit. This system also achieved maximum power point for solar modules and enhanced rapid charging-discharging for a supercapacitor bank. Both SPS and the blended SPS-ESPS control algorithms were verified experimentally using 2 kW DAB-IBDC topology implemented with standalone power system that combination of 2000 W input solar module and 158 Wh supercapacitor bank.