Half-cycle Modulation Research Articles

Simulation Model of Dual Boost Inverter using Half Cycle Modulation Technique

The output voltage of conventional full bridge inverters is lower than the DC input voltage. In applications where the input DC voltage is very low, front-end step-up converters are typically needed, resulting in a two-stage conversion process. The Dual boost inverter (DBI) offers many benefits, including fewer power devices, a straightforward design, and the ability to operate in both boost and buck modes. The traditional modulation technique used in DBI has a number of disadvantages, including the fact that all the devices work at higher frequencies and must tolerate larger voltage and current stresses, which increases conduction and switching losses and lowers efficiency. This study suggests a novel modulation technique called half cycle modulation (HCM), which makes all devices work at high frequency only every half cycle, significantly reducing conduction and switching losses and boosting DBI efficiency. Additionally, an improved DBI is suggested that can bypass the inductor current with little switching stress in order to reduce the current circulation losses in DBI. In this study, a detailed comparison between the traditional DBI and the HCM modulated DBI is discussed. In the MATLAB/SIMULINK software, the suggested DBI and its modulation techniques are simulated, and the results are also shown.

Single-Loop Control for Single-Phase Dual-Boost Grid-Tied Inverter With Half Cycle Modulation and Feedforward Virtual-Vectors MPC

In this letter, a simplified single current loop control scheme for single-phase dual-boost inverter has been developed, combining half cycle modulation and virtual-vector (VV) based model predictive control (MPC). As the control reference can be slipped and allocated into two side boost, only a unified grid current reference is relied on in this proposed control method. Furthermore, with the concept of feedforward control, the global optimal solution space in MPC can be compressed, taking the duty ratio as boundary for the precompacted solution space. Thereby, the improved MPC can select the optimal VV in a smaller and closer subspace. Consequently, much finer control effect can be obtained. Experimental tests are provided to validate the proposed solution and its merits.

Robust Digital Nonlinear Control System for Dual Active Bridge (DAB) DC/DC Converters With Asymmetric Half-Cycle Modulation

This article presents a new digital control system for dual active bridge dc/dc converters. The proposed control system includes a novel compensator with asymmetric half-cycle modulation. The proposed compensator is based on a novel geometric-sequence-control algorithm, which is a model-based predictive current control. The proposed control system provides fast and seamless tracking of the reference current and ensures zero dc current in the transformer windings (prevents transformer saturation). Moreover, it offers high robustness against perturbations and uncertainties in the converter. It also allows symmetric growth of transformer current during transients, thereby eliminating potential temporary saturation issues. Analysis, simulation, and experimental results are provided to demonstrate the superior performance of the proposed control in achieving high precision output regulation, fast and seamless transient response, and high robustness.

A Non-Isolated Step-up DC-AC Converter With Reduced Leakage Current for Grid-Connected Photovoltaic Systems

In this paper, a non-isolated step-up single-phase dc-ac converter is proposed for distributed low voltage photovoltaic (PV) systems. The proposed converter has a common ground between the dc photovoltaic input and ac output voltage, which can reduce the leakage current to a very low level and thus improve the reliability and power generation efficiency. By analyzing and comparing the two modulation methods, a unified half cycle modulation is selected for the design of the proposed converter, in which only two switches are operated at high frequency in a line cycle. Therefore, the conduction and switching loss can be reduced greatly. In addition, due to the unified half cycle modulation for the active switches of the proposed inverter, the dc-link capacitor does not need to have a decoupling function. The capacitor can then be optimized to a small value for improving the reliability and power density. A theoretical analysis of the proposed converter is described, and an experimental prototype is implemented to verify the performance of the presented converter topology.

Switching and Conduction Loss Reduction of Dual-Buck Full-Bridge Inverter Through ZVT Soft-Switching Under Full-Cycle Modulation

Based on the no blanking time characteristic, voltage error does not occur in the pulsewidth modulated output stage of dual-buck full-bridge inverter (DBFBI), resulting in lower total harmonic distortion (THD) of the output current. The two main modulations applied in the topology are half-cycle modulation and full-cycle modulation. Compared with the half-cycle modulation, the full-cycle modulation does not have the zero-crossing problem, but the inverter requires a bias current to guarantee better output waveform. The circulation current loop caused by bias current has a great influence on inverter efficiency. This article proposes a novel zero voltage transition (ZVT) soft-switching topology to increase efficiency by reducing the switching losses and conduction losses resulting from low bias current. The advantages of the DBFBI are included in the proposed inverter. The soft-switching condition is achieved by the snubber cells, and the energy stored in the passive snubber capacitors can be transferred effectively. The topology deduction, operating principles, and design guidelines are presented in detail. An 800-W experimental prototype operating with a 100-kHz switching frequency is implemented to verify the theoretical result.

Electromagnetically induced transparency in sinusoidal modulated ring resonator

In the present work, we demonstrate controlling the excitation of bright mode (continuum mode) resonance and dark mode (discrete mode) resonance in a planar metasurface made of sinusoidal modulation inside a closed rectangular metallic ring placed over a dielectric substrate. Unlike asymmetrical breaking of a meta-atom (often referred to as the unit cell) to achieve the dark mode response in regular metamaterials, in the present structure, the bright or dark mode resonance is achieved using even or odd half cycle modulation. The achieved dark-mode shows a sharp resonance for a particular polarization of the incident electric field, which results in an electromagnetically induced transparency like spectrum. The electromagnetic behavior of the proposed meta-atom has been investigated in the frequency domain using commercially available software and validated through experiments in the gigahertz regime.

Improved Dual Boost Inverter With Half Cycle Modulation

The output voltage of a traditional full-bridge inverter is lower than the input dc voltage. In applications when the input voltage is low, the front-end step-up converter is usually required, presenting a two-stage power conversion. Dual boost inverter (DBI) can realize single-stage conversion, which has the advantages of a simple structure, less power devices, and buck–boost ability. The traditional modulation strategy of DBI makes all power switches operate in high frequency and sustain high voltage/current stress, which leads to heavy conduction and switching loss. This paper proposed a modulation strategy, namely, half cycle modulation (HCM), which makes power switches work in high frequency just in half cycle, and can greatly reduce the conduction and switching loss of the power devices. Furthermore, to reduce the current circulation loss in DBI, an improved DBI with two clamping switches is proposed based on HCM, which can bypass the inductor current with low stress switches; therefore, the loss caused by circulation current can be greatly reduced. A detailed analysis and comparison between the traditional and HCM strategies are given in this paper. Finally, a 500 VA DBI prototype is designed in the lab. The advantages of the proposed HCM strategy and improved DBI with two clamping switches are verified by experimental results.

Half-cycle modulation for VCSEL based 6-Gbaud 4-QAM transmission over 1 km multimode fibre link

A subcarrier multiplexing system with the subcarrier frequency at half the baud rate to improve the spectral efficiency is demonstrated. A 12 Gbit/s 4-QAM signal in 9GHz bandwidth was successfully transmitted over a 1 km OM4 MMF 850 nm VCSEL without any equalisation method. The 1.5 dB power penalty was improved compared to an OOK signal at the same data rate.

Transient absorption of attosecond pulse trains by laser-dressed helium

We investigate transient absorption of high harmonics in an attosecond pulse train by laser-dressed He atoms using both single-atom and macroscopic methods. Calculations of the absorption as a function of laser wavelength and intensity reveal that the absorption probability is tied to resonant laser-dressed atomic states. We report for the first time to our knowledge a quarter-laser-cycle modulation in the absorption (mixed with the well-known half-cycle modulation). We discuss the conditions for which this high-order coupling could be observed and the role that the reshaping of the attosecond pulses in the medium plays in the timing of absorption.