A Novel Virtual Vector Modulation-based scheme of Model Power Predictive for VIENNA Rectifier

When the finite control set model predictive(FCS-MPC) algorithm is applied to the three-level converter, there are problems such as large current harmonics, high requirements for the computing efficiency of the micro-controller, complex multi-objective optimization and limited output vector switching. In additional, the mismatch of inductance parameter may directly affect the observation accuracy of FCS-MPC. Furthermore, due to the limitation of finite set model prediction, it leads to the switching operation is not constant and the decrease of the grid-connected current quality. In this regard, an improved model predictive direct power control based on the combined virtual vector modulation (MPDPC-VM) is proposed by considering the influence of the filter inductance parameter mismatch. The finite control set and restricted vector switching of the Vienna rectifier are modeled to avoid excessive voltage jumps, and the predicted values of input power is obtained by the sliding-mode control (SMC) strategy. Then, a linear synthesis method of virtual vector modulation-based scheme is proposed, which increases the number of the available voltage vectors in a single switching period from 8 to 19. The grid-connected current ripple is improved by reducing the error between the expected voltage vector and the available voltage vector. Finally, the model reference adaptive system (MRAS) method is applied to improve the working reliability and reduce the influence of mismatching of inductance parameters. Extensive simulation and matching experimental results is given to demonstrate the validity of the proposed strategy under steady-state and transient responses conditions compared against the existing FCS-MPC

Generation of pulse trains with nonconventional temporal correlation properties

We apply time dependent spectral phase modulation to generate pulse trains that are spectrally and temporally partially coherent in an ensemble averaged sense. We consider, in particular, quadratic spectral phase modulation of Gaussian pulses, and demonstrate two particular types of nonuniformly correlated pulse trains. The controlled partial temporal coherence of the nonstationary fields is generated using a pulse compressor and experimentally verified with frequency resolved optical gating (FROG). We show that the correlation characteristics of such pulse trains can be retrieved directly from the FROG spectrograms provided one has certain a priori knowledge of the pulse train. Our results open a pathway for experimental confirmation of several correlation induced effects in the temporal domain.acceptedVersionPeer reviewe

The control of pulse profiles with tunable temporal coherence

A new class of partially coherent pulse sources with Multi-Gaussian Schell-model (MGSM) correlations is proposed. The expression for the intensity distribution for the MGSM pulses generated by such sources on propagation through the dispersive media is derived. It is demonstrated that the pulse intensity profile, in particular, the width of the flat center of pulse intensity profile and the peak intensity, can be controlled by adjusting the source temporal coherence. The obtained results have potential applications in pulse shaping for communication and media sensing or pulsed laser material processing. •The MGSM pulses with Multi-Gaussian Schell-model (MGSM) correlations are proposed.•The intensity distribution for the MGSM pulses is derived.•The pulse intensity profile can be controlled by adjusting the source temporal coherence

Position modulation with random pulses

A new class of sources generating ensemble of random pulses is introduced based on superposition of the mutual coherence functions of several Multi-Gaussian Schell-model sources that separately are capable of shaping the propagating pulse's average intensity into flat profiles with adjustable duration and edge sharpness. Under certain conditions that we discuss in detail such superposition allows for production of a pulse ensemble that after a sufficiently long propagation distance in a dispersive medium reshapes its average intensity from an arbitrary initial profile to a train whose parts have flat intensities of different levels and durations and can be either temporarily separated or adjacent

Correlation of Intensity Fluctuations for Scattering of a Partially Coherent Plane-Wave Pulse

We derived analytical expressions for the correlation of intensity fluctuations of a partially coherent Gaussian Schell-model plane-wave pulse scattered by deterministic and random media. Our results extend the study of correlation of intensity fluctuations at two space points for scattered stationary fields to that at two time points for scattered non-stationary fields

Cosine-Gaussian correlated Schell-model pulsed beams

A new class of partially coherent pulses of Schell type with cosine-Gaussian temporal degree of coherence is introduced. Such waves are termed the Cosine-Gaussian Schell-model (CGSM) pulses. The analytic expression for the temporal mutual coherence function of the CGSM pulse in dispersive media is derived and used to study the evolution of its intensity distribution and its temporal degree of coherence. Further, the numerical calculations are performed in order to show the dependence of the intensity profile and the temporal degree of coherence of the CGSM pulse on the incident pulse duration, the initial temporal coherence length, the order-parameter n and the dispersion of the medium. The most important feature of the novel pulsed wave is its ability to split into two pulses on passage in a dispersive medium at some critical propagation distance. Such critical distance and the subsequent evolution of the split pulses are shown to depend on the source parameters and on the properties of the medium in which the pulse travels

Turbulence-resistant self-focusing vortex beams

We consider recently introduced self-focusing fields that carry orbital angular momentum (OAM) [Opt. Lett. $\textbf{46}$, 2384$-$2387 (2021)] and in particular, their propagation properties through a turbulent ocean. We show that this type of field is especially robust against turbulence induced degradation, when compared to a completely coherent beam. In moderately strong oceanic turbulence, the self-focusing OAM beam features over five orders of magnitude higher peak intensities at the receiver plane, an $\sim$80 $\%$ detection probability for the signal mode, as well as an energy transmission efficiency in excess of 70 $\%$ over a link of $\sim$100 m. Counter-intuitively, the focusing properties of such fields may be enhanced with increasing turbulence, causing the mean squared waist to become smaller with greater turbulence strength. Our results demonstrate that certain types of partial coherence may be highly desirable for optical telecommunication employing OAM

Sinc Schell-model pulses

Two partially coherent pulsed sources with sinc Schell-model (SSM) correlations are introduced. The analytic formulas for the average intensities of random pulse ensembles generated by such pulse sources propagating in dispersive medium are derived, and used to investigate their evolution. It is illustrated that the first type of pulsed source can generate tunable far-field flat profiles controlled by temporal correlation parameter and dispersion coefficient. The average intensity of the pulse ensembles generated by the second type of sources can split from a single distribution into two symmetric parts

Non-stationary pulses with complex-valued temporal degree of coherence

It is shown that fine phase structuring of the temporal degree of coherence of a non-stationary pulse source leads to breaking its average arrival time symmetry on propagation in a linear dispersive medium. We employ the temporal counterpart of a recently proposed sliding function technique ((2018) Opt. Lett. 43 4727) for obtaining several models for the bona fide complex temporal degree of coherence of Schell-model non-stationary pulse trains and examine their evolution in fibers with and without a chirper. In particular we have examined linear, signum, cubic and trochoid phase models of the temporal degree of coherence. We also propose a simple method for experimental realization of the new pulsed sources and offer computer simulations confirming its viability

Evolution of Spatiotemporal Intensity of Partially Coherent Pulsed Beams with Spatial Cosine-Gaussian and Temporal Laguerre–Gaussian Correlations in Still, Pure Water

A new family of partially coherent pulsed beams with spatial cosine-Gaussian and temporal Laguerre–Gaussian correlations, named spatial cosine-Gaussian and temporal Laguerre–Gaussian correlated Schell-model (SCTLGSM) pulsed beams, is introduced. An analytic propagation formula is derived for the SCTLGSM pulsed beam through the spatiotemporal ABCD optical system characterizing a continuous dispersive medium. As an example, the evolution of spatiotemporal intensity of the SCTLGSM pulsed beam in a still, pure water column is then investigated. It is found that the SCTLGSM pulsed beams simultaneously exhibit spatiotemporal self-splitting and self-focusing phenomena, which can be attributed to the special spatial/temporal coherence structures and the presence of pulse chirper in the source plane. The physical interpretation of the obtained phenomena is given. The results obtained in this paper will be of interest in underwater optical technologies, e.g., directed energy and communications