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The phase-locked loop (PLL) has an important effect on the system stability of grid-connected converters in weak grids. In the literature, parameter tuning methods and stabilizing control strategies have been proposed to deal with this problem. However, most of them target at tuning parameters of PLL or mitigating the negative damping as well as the phase lag introduced by the PLL, while the interactions between the PLL and the current control and the cross coupling effects are still not fully explored in the design procedure of stabilizing control. To address this issue, this article extends the study of the interaction between the PLL and the current control using a multiple-input multiple-output (MIMO) model, and then proposes a design criterion of the stabilizing control using design-oriented analysis from the perspective of MIMO impedance model. A category of stabilizing control schemes that uses different types of biquad filters is proposed following the criterion, which not only improves system stability but also removes the coupling between the PLL and the current control according to the sensitivity analysis. Hardware-in-the-loop and experimental results are provided to verify the effectiveness of the proposed control schemes., QC 20240415

Microstructures dominated by acicular a' martensitic phase, such as in the case of Ti-6Al-4V fabricated by laser powder-bed fusion (PBF-LB), are known to suffer from reduced ductility and low toughness. The decomposition of such metastable microstructures into a+ß lamellar structures during PBF-LB requires either specific laser regimes that are often challenging to be attained or post-process heat treatments which might lead, instead, to undesirable coarsening of the grain structure. Here we propose a novel route for the formation of ultrafine lamellar a+ß microstructures and demonstrate the associated advantages in terms of tensile strength and ductility. Our approach is based on a suitable modification of constitution of Ti-6Al-4V with additions of Fe, a known potent ß stabiliser of high intrinsic diffusivity. After printing, this alloy presents a microstructure dominated by metastable ß phase. We investigate the details of its decomposition using a combination of in-situ high-energy synchrotron X-ray diffraction and high temperature microscopy up to the ß transus temperature. The microstructure evolution is comprised by homogeneous decomposition of the metastable ß phase via ¿-assisted nucleation of a phase, a grain growth sustained by early diffusion of Fe in the ß phase followed by a conventional partitioning of V. The understanding of this transformation pathway enables the development of ultrafine grained a+ß lamellar microstructures that exhibit outstanding tensile behaviour. The presented approach is machine-agnostic and offers a novel alloy design strategy for development of high-strength alloys in additive manufacturing., Peer Reviewed, Postprint (published version)

Background Diabetes is one of the leading causes of death and disability worldwide, and affects people regardless of country, age group, or sex. Using the most recent evidentiary and analytical framework from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD), we produced location-specific, age-specific, and sex-specific estimates of diabetes prevalence and burden from 1990 to 2021, the proportion of type 1 and type 2 diabetes in 2021, the proportion of the type 2 diabetes burden attributable to selected risk factors, and projections of diabetes prevalence through 2050. Methods Estimates of diabetes prevalence and burden were computed in 204 countries and territories, across 25 age groups, for males and females separately and combined; these estimates comprised lost years of healthy life, measured in disability-adjusted life-years (DALYs; defined as the sum of years of life lost [YLLs] and years lived with disability [YLDs]). We used the Cause of Death Ensemble model (CODEm) approach to estimate deaths due to diabetes, incorporating 25 666 location-years of data from vital registration and verbal autopsy reports in separate total (including both type 1 and type 2 diabetes) and type-specific models. Other forms of diabetes, including gestational and monogenic diabetes, were not explicitly modelled. Total and type 1 diabetes prevalence was estimated by use of a Bayesian meta-regression modelling tool, DisMod-MR 2.1, to analyse 1527 location-years of data from the scientific literature, survey microdata, and insurance claims; type 2 diabetes estimates were computed by subtracting type 1 diabetes from total estimates. Mortality and prevalence estimates, along with standard life expectancy and disability weights, were used to calculate YLLs, YLDs, and DALYs. When appropriate, we extrapolated estimates to a hypothetical population with a standardised age structure to allow comparison in populations with different age structures. We used the comparative, Peer Reviewed, Postprint (published version)

In Part I, a method for the Harmonic Power-Flow (HPF) study of three-phase power grids with Converter-Interfaced Distributed Energy Resources (CIDERs) is proposed. The method is based on generic and modular representations of the grid and the CIDERs, and explicitly accounts for coupling between harmonics. In Part II, the HPF method is validated. First, the applicability of the modeling framework is demonstrated on typical grid-forming and grid-following CIDERs. Then, the HPF method is implemented in Matlab and compared against time-domain simulations with Simulink. The accuracy of the models and the performance of the solution algorithm are assessed for individual resources and a modified version of the CIGR\'E low-voltage benchmark microgrid (i.e., with additional unbalanced components). The observed maximum errors are 6.3E-5 p.u. w.r.t. voltage magnitude, 1.3E-3 p.u. w.r.t. current magnitude, and 0.9 deg w.r.t. phase. Moreover, the scalability of the method is assessed w.r.t. the number of CIDERs and the maximum harmonic order ($\leqslant$25). For the maximum problem size, the execution time of the HPF method is 6.52 sec, which is 5 times faster than the time-domain simulation. The convergence of the method is robust w.r.t. the choice of the initial point, and multiplicity of solutions has not been observed.

Power distribution systems are experiencing a large-scale integration of Converter-Interfaced Distributed Energy Resources (CIDERs). This complicates the analysis and mitigation of harmonics, whose creation and propagation are facilitated by the interactions of converters and their controllers through the grid. In this paper, a method for the calculation of the so-called Harmonic Power-Flow (HPF) in three-phase grids with CIDERs is proposed. The distinguishing feature of this HPF method is the generic and modular representation of the system components. Notably, as opposed to most of the existing approaches, the coupling between harmonics is explicitly considered. The HPF problem is formulated by combining the hybrid nodal equations of the grid with the closed-loop transfer functions of the CIDERs, and solved using the Newton-Raphson method. The grid components are characterized by compound electrical parameters, which allow to represent both transposed or non-transposed lines. The CIDERs are represented by modular linear time-periodic systems, which allows to treat both grid-forming and grid-following control laws. The method's accuracy and computational efficiency are confirmed via time-domain simulations of the CIGR\'E low-voltage benchmark microgrid. This paper is divided in two parts, which focus on the development (Part I) and the validation (Part II) of the proposed method.

Active filters are power electronics devices used to eliminate harmonics from the distribution network. This article presents an active disturbance rejection control scheme for active filters. The controller is based on a linear disturbance observer combined with a disturbance rejection scheme. The parameter tuning is based on a combined pole placement and an optimal estimation based on Kalman-Bucy filter. Proposed scheme is validated through simulation and experimental work in an active filter., Postprint (author’s final draft)

The development of power electronics and control technology provides improved performance of the electrical appliances, making them robust to changes in the supply voltage or frequency. However, power electronic converters behave as constant power loads (CPLs), which have negative impedance characteristics, and this non-linear behavior is challenging the stability of the grid. This paper investigates the input impedance of a three-phase low-voltage grid connected ac-dc converter that operating as a CPL when interfaced to a single DC bus and a changeable load. The possibility of adopting a Smart Transformer (ST), a power electronics converter which feeds a low-voltage grid, for the CPL stabilization is also addressed. To analyze the behavior of CPLs, a strategy of impedance modelling is employed. Gain Margin Phase Margin (GMPM) Criterion is referred to judge the stability of the system and verify the stabilization operation for CPLs. Simulation results are presented to be as a support.

The development of power electronics and control technology provides improved performance of the electrical appliances, making them robust to changes in the supply voltage or frequency. However, power electronic converters behave as constant power loads (CPLs), which have negative impedance characteristics, and this non-linear behavior is challenging the stability of the grid. This paper investigates the input impedance of a three-phase low-voltage grid connected ac-dc converter that operating as a CPL when interfaced to a single DC bus and a changeable load. The possibility of adopting a Smart Transformer (ST), a power electronics converter which feeds a low-voltage grid, for the CPL stabilization is also addressed. To analyze the behavior of CPLs, a strategy of impedance modelling is employed. Gain Margin Phase Margin (GMPM) Criterion is referred to judge the stability of the system and verify the stabilization operation for CPLs. Simulation results are presented to be as a support.

The development of power electronics and control technology provides improved performance of the electrical appliances, making them robust to changes in the supply voltage or frequency. However, power electronic converters behave as constant power loads (CPLs), which have negative impedance characteristics, and this non-linear behavior is challenging the stability of the grid. This paper investigates the input impedance of a three-phase low-voltage grid connected ac-dc converter that operating as a CPL when interfaced to a single DC bus and a changeable load. The possibility of adopting a Smart Transformer (ST), a power electronics converter which feeds a low-voltage grid, for the CPL stabilization is also addressed. To analyze the behavior of CPLs, a strategy of impedance modelling is employed. Gain Margin Phase Margin (GMPM) Criterion is referred to judge the stability of the system and verify the stabilization operation for CPLs. Simulation results are presented to be as a support.

The development of power electronics and control technology provides improved performance of the electrical appliances, making them robust to changes in the supply voltage or frequency. However, power electronic converters behave as constant power loads (CPLs), which have negative impedance characteristics, and this non-linear behavior is challenging the stability of the grid. This paper investigates the input impedance of a three-phase low-voltage grid connected ac-dc converter that operating as a CPL when interfaced to a single DC bus and a changeable load. The possibility of adopting a Smart Transformer (ST), a power electronics converter which feeds a low-voltage grid, for the CPL stabilization is also addressed. To analyze the behavior of CPLs, a strategy of impedance modelling is employed. Gain Margin Phase Margin (GMPM) Criterion is referred to judge the stability of the system and verify the stabilization operation for CPLs. Simulation results are presented to be as a support.

The development of power electronics and control technology provides improved performance of the electrical appliances, making them robust to changes in the supply voltage or frequency. However, power electronic converters behave as constant power loads (CPLs), which have negative impedance characteristics, and this non-linear behavior is challenging the stability of the grid. This paper investigates the input impedance of a three-phase low-voltage grid connected ac-dc converter that operating as a CPL when interfaced to a single DC bus and a changeable load. The possibility of adopting a Smart Transformer (ST), a power electronics converter which feeds a low-voltage grid, for the CPL stabilization is also addressed. To analyze the behavior of CPLs, a strategy of impedance modelling is employed. Gain Margin Phase Margin (GMPM) Criterion is referred to judge the stability of the system and verify the stabilization operation for CPLs. Simulation results are presented to be as a support.