Adaptive scheme protecting renewable‐dominated micro‐grids against usual topology‐change events

: Because of the consistently expanding energy request, the introduction of a decentralized micro-grid based on energy resources will soon be the most exciting development in the power system. Micro-grids, which are mainly based on inverters, are becoming more popular as they can handle different forms of renewable energy effectively. However, one of the most challenging areas of research is their control. In the last few years, many control strategies have been developed. In this review, different control methods have been discussed that apply to the micro-grid system. Furthermore, the comparative analysis of classical and modern control strategies is also considered. This survey guides the new researchers about all available control strategies and room for improvement towards the optimal solution of the micro-grid control techniques. It also identifies several research gaps and future trends therein as well as provides a solution to manage problems in MGs. The strategies are then compared based on their applicability to different control requirements.

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A Frequency Adaptive Scheme Based on Newton Structure of PRRC for LCL-Type Inverter Connected with Weak Grid

Energies ◽

10.3390/en14144225 ◽

2021 ◽

Vol 14 (14) ◽

pp. 4225

Author(s):

Chengbi Zeng ◽

Sudan Li ◽

Hanwen Wang ◽

Hong Miao

Keyword(s):

Repetitive Control ◽

Harmonic Distortion ◽

Adaptive Scheme ◽

Computational Burden ◽

Weak Grid ◽

Control Scheme ◽

Sample Frequency ◽

Fractional Delay ◽

Pr Controller ◽

Online Tuning

Repetitive control (RC) is gradually used in inverters tied with weak grid. To achieve the zero steady-state error tracking of inverter current and compensate the harmonic distortion caused by frequency fluctuation, a frequency adaptive (FA) control scheme for LCL-type inverter connected with weak grid is proposed. This scheme adopts a proportional resonance (PR) controller in parallel with RC (PRRC) to overcome the disadvantages caused by RC inherent one-cycle time delay. A fractional delay (FD) filter based on the Newton structure is proposed to approximate the fraction item of fs/f, where fs and f are sample frequency and grid frequency, respectively. The structure of the proposed FD filter is relatively simple; moreover, coefficients of the filter maintain constant so as not to need online tuning even when grid frequency fluctuates, which decreases the computational burden considerably. The feasibility and effectiveness of the proposed FA control scheme, named as Newton-FAPRRC, are all verified by the simulation and experimental results.

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Bipolar Bidirectional DC-DC Converter for Medium and High Voltage DC Micro grids

2021 6th International Conference for Convergence in Technology (I2CT) ◽

10.1109/i2ct51068.2021.9417952 ◽

2021 ◽

Author(s):

Patil Mounica ◽

Srinivasa Rao Sandepudi

Keyword(s):

High Voltage ◽

Micro Grids

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Topology change, emergent symmetries and compact star matter

AAPPS Bulletin ◽

10.1007/s43673-021-00016-1 ◽

2021 ◽

Vol 31 (1) ◽

Author(s):

Yong-Liang Ma ◽

Mannque Rho

Keyword(s):

Nuclear Matter ◽

Compact Star ◽

Momentum Tensor ◽

Effective Field ◽

Compact Stars ◽

Strongly Correlated ◽

Topology Change ◽

Dense Nuclear Matter ◽

Skyrmion Matter ◽

Energy Constants

AbstractTopology effects have being extensively studied and confirmed in strongly correlated condensed matter physics. In the limit of large number of colors, baryons can be regarded as topological objects—skyrmions—and the baryonic matter can be regarded as a skyrmion matter. We review in this paper the generalized effective field theory for dense compact-star matter constructed with the robust inputs obtained from the skyrmion approach to dense nuclear matter, relying on possible “emergent” scale and local flavor symmetries at high density. All nuclear matter properties from the saturation density n0 up to several times n0 can be fairly well described. A uniquely novel—and unorthdox—feature of this theory is the precocious appearance of the pseudo-conformal sound velocity $v^{2}_{s}/c^{2} \approx 1/3$ v s 2 / c 2 ≈ 1 / 3 , with the non-vanishing trace of the energy momentum tensor of the system. The topology change encoded in the density scaling of low energy constants is interpreted as the quark-hadron continuity in the sense of Cheshire Cat Principle (CCP) at density $\gtrsim 2n_{0}$ ≳ 2 n 0 in accessing massive compact stars. We confront the approach with the data from GW170817 and GW190425.

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Early life predictors of positive change during the coronavirus disease pandemic

BMC Psychology ◽

10.1186/s40359-021-00586-7 ◽

2021 ◽

Vol 9 (1) ◽

Author(s):

Maria E. Bleil ◽

Bradley M. Appelhans ◽

Alexis S. Thomas ◽

Steven E. Gregorich ◽

Neal Marquez ◽

...

Keyword(s):

Youth Development ◽

Early Life ◽

Census Data ◽

Neighborhood Disadvantage ◽

Positive Change ◽

Self Report ◽

Positive Health ◽

Neighborhood Contexts ◽

Change Events ◽

Negative Impacts

Abstract Background The COVID-19 pandemic is a crisis unprecedented in its size and scope. Yet studies of resilience suggest most individuals will successfully negotiate this challenge and some may even experience growth and positive change. Some evidence suggests that the capacity to enact positive change in the face of adversity may be shaped by early life experiences. Methods In a subset of 374 participants (57% female, mean age = 29 years) in the Study of Early Child Care and Youth Development (SECCYD), a longitudinal, birth cohort, prospective models were tested to determine whether early life adversities in family and neighborhood contexts predict positive change events in response to the COVID-19 pandemic. Childhood family and neighborhood contexts were assessed using a combination of self-report questionnaires and US Census data. Adulthood positive change events (e.g., becoming more appreciative of things usually taken for granted) were assessed using the Epidemic-Pandemic Impacts Inventory (EPII). Results In regression analyses, neighborhood disadvantage in childhood, measured both by objective and subjective assessments, predicted a higher number of positive change events in response to the COVID-19 pandemic (β = .18, p = .004 and β = .15, p = .006, respectively). Examination of the positive change event subscales showed neighborhood disadvantage in childhood predicted increases in events related to ‘perspective taking and charitable giving’ (β = .20, p = .022 and β = .17, p = .002, respectively) and improved ‘social relationships’ (β = .18, p = .004 and β = .13, p = .020, respectively), but not to positive ‘health behaviors’ (ps > .05). All associations were independent of sociodemographic factors and childhood family dysfunction. Conclusions Findings suggest that neighborhood disadvantage in childhood may shape prosocial responses to stress in adulthood, potentially through early life adaptions to stress that are protective when facing adversity. There are several notable implications of the study findings. Although adversity in early life has clear negative impacts, it is possible that adversity experiences may also provide opportunities to develop adaptive strategies that foster resilience and growth when facing stress. Intervention efforts should consider leveraging such stress-adapted strengths to reduce the many negative impacts of early life adversity.

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Voltage Control of Islanded Hybrid Micro-grids Using AI Technique

2020 IEEE Electric Power and Energy Conference (EPEC) ◽

10.1109/epec48502.2020.9320049 ◽

2020 ◽

Author(s):

H.E. Keshta ◽

A.A. Ali ◽

O.P. Malik ◽

E.M. Saied ◽

F.M. Bendary

Keyword(s):

Voltage Control ◽

Micro Grids

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