• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.5
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• pp.440-448
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• 2017

This paper proposes a controller design of a distributed source inverter in stand-alone mode or grid-connected mode to compensate the current or voltage harmonics caused by local nonlinear load. The PR-based multi loop controller has been used to improve the dynamic performance of the system and to compensate the output voltage or grid current harmonics. The multi-loop controller consists of an outer current controller and an inner voltage controller for the output voltage control in stand-alone mode. In grid-connected mode, an outer current controller is added to the output voltage controller for the grid current control. The design performance of each controller is described through the Root locus and Bode plot of the transfer functions. The validity of the proposed control algorithm and design parameters has been verified through the PSiM simulation and experimental results.

• Journal of Korean Society of Forest Science
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• v.96 no.2
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• pp.138-144
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• 2007

This study was undertaken to compare the biomass of Abies koreana growing at two sites. A $10{\times}10m$ plot was established in each site of a natural stand in Mt. Jiri and a plantation in Gyeongsan nursery. Five trees of A. koreana were randomly selected in each site. The following traits were investigated from each tree : height, basal diameter, age, weight of stem, branches, and needles as above-ground traits and weight of total roots, horizontal roots, and vertical roots as below-ground traits. In Gyeongsan nursery, age of sample trees was negatively correlated with both height and weight of total stem, while height was highly correlated with weight of horizontal roots. There was high correlation between the basal diameter and weight of total stem, and between the basal diameter and weight of roots. In Mt. Jiri stand, most of the above-ground traits except age were significantly correlated with the below-ground traits. The linear regression equation between the cross section area of base (X) and the weight of total stem (Y) in Gyeongsan nursery was Y=12.66X-12.92, and correlation was significant ($R^2=0.89$). The linear regression equation between the cross section area of base(X) and the weight of total branches (Y) in Mt. Jiri stand was Y=25.51X+6.00, and correlation was highly significant ($R^2=1.0$).

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.30 no.3
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• pp.79-85
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• 2016

This paper analyzed the influence of wind power fluctuations in grid frequency of a stand-alone microgrid that is hybrid generation system with diesel generator, wind turbine, and Battery Energy Storage System (BESS). The existing island area power system consists of only diesel generators. So the grid frequency can be controllable from load change. But hybrid generation system with Renewable Energy Sources (RES) such as wind energy that has the intermittent output can bring power quality problems. BESS is one of the ways to improve the intermittent output of the RES. In this paper, we analyzed the role of BESS in a stand-alone microgrid. We designed a modelling of wind power system with squirrel-cage induction generator, diesel power system with synchronous generator, and BESS using transient analysis program PSCAD/EMTDC. And we analyzed the variation of the grid frequency according to the output of BESS.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.5
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• pp.448-457
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• 2013

This paper proposes a control method under stand-alone operating mode for distributed-module type photovoltaic power conditioners. In conventional schemes, there are some problems of a controller saturation in the DC-link (or load) voltage controller when overly-heavy load, light load, and the generated PV power reduction occurs, as well as when a transition occurs from an overly-loaded to normal conditions. To overcome these problems, the proposed controller method switches the main control target from DC-link voltage to the maximum power point, which is closer to the stable operating point when it returns to normal operating conditions. For the analysis, a state-plane trajectory was given and the circuit analysis by PSIM simulation was done. For the verification, a prototype hardware with 110[W] and 50[W] dual photovoltaic modules has been implemented. From the results, it can be seen that PV power tracking is successfully done with the proposed method even under a stand-alone operation mode.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.12
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• pp.210-216
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• 2009

Distributed Generation (DG) is predicted to play a important role in electric power system in the near future. insertion of DG system into existing distribution network has great impact on real-time system operation and planning. It is widely accepted that micro turbine generation (MTG) systems are currently attracting lot of attention to meet customers need in the distributed power generation market. In order to investigate the performance of MT generation systems, their efficient modeling is required. This paper presents the modeling and simulation of a MT generation system suitable for stand-alone operation. The system comprises of a permanent magnet synchronous generator driven by a MT. A brief description of the overall system is given, and mathematical models for the MT and permanent magnet synchronous generator are presented. Also, the use of power electronics in conditioning the power output of the generating system is demonstrated. Simulation studies with MATLAB/Simulink have been carried out in stand-alone operation mode of a DG system.

• Journal of Power Electronics
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• v.17 no.4
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• pp.1027-1036
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• 2017

The brushless doubly-fed induction generator (BDFIG) is a new type of dual stator winding induction generator. In such a generator, both the power winding (PW) and the control winding (CW) are housed in the stator. This paper presents the performance characteristics of a stand-alone BDFIG operation system. A new T-type steady-state model of a BDFIG is proposed. This model is more suitable for the performance analysis of stand-alone BDFIGs than the conventional Π-type steady-state model and the simplified inner core steady-state model. The characteristics of the power flow and CW current are analyzed by detailed mathematical derivations on the basis of the proposed T-type steady-state model. The analysis results are verified by experiments, which are carried out on a prototype BDFIG. The results of the performance analysis contribute to simplifying the control circuit, improving the control performance, and selecting an appropriate BDFIG for actual industrial applications.

• PNF and Movement
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• v.15 no.1
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• pp.85-96
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• 2017

Purpose: Peripheral neuropathy accompanied by sensory disturbance, such as limb paralysis and hemiplegia, is mainly caused by acute disseminated encephalomyelitis (ADEM). This case study aimed to determine the effect of ankle strengthening exercises that use proprioceptive neuromuscular facilitation (PNF) on the gait, balance, ankle-control ability, and sit-to-stand ability on a patient with ADEM. Methods: A 10-year-old male with quadriplegia and ankle-control impairment participated in this 4-week training intervention. The patient, diagnosed with ADEM, was treated with ankle strengthening exercises that used PNF. Results: The patient demonstrated improvements in balance, ankle-control ability, sit-to-stand ability, and gait performance. Outcome measures (manual muscle test, modified Ashworth scale, sensory assessment, coordination assessment, Berg balance scale, 5 time sit-to-stand test, and 10 m walk test) were taken before and after the training program. Conclusion: The results of this case suggest that an ankle strengthening exercise that uses PNF can improve the gait, balance, ankle-control ability, and sit-to-stand ability in patients with ADEM. In ADEM, the initial treatment is important, and the use of ankle strengthening exercises with PNF could lead to meaningful results. However, there is limited research due to an insufficient number of cases. In the future, more patients will need to be studied.

• Journal of Forest and Environmental Science
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• v.34 no.6
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• pp.451-456
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• 2018

The use of single component distribution to describe the irregular stand structure of degraded forest often lead to bias. Such biasness can be overcome by the application of finite mixture distribution. Therefore, in this study, finite mixture distribution was used to characterise the irregular stand structure of the Gmelina arborea plantation in Omo forest reserve. Thirty plots, ten each from the three stands established in 1984, 1990 and 2005 were used. The data were pooled per stand and fitted. Four finite mixture distributions including normal mixture, lognormal mixture, gamma mixture and Weibull mixture were considered. The method of maximum likelihood was used to fit the finite mixture distributions to the data. Model assessment was based on negative loglikelihood value ($-{\Lambda}{\Lambda}$), Akaike information criterion (AIC), Bayesian information criterion (BIC) and root mean square error (RMSE). The results showed that the mixture distributions provide accurate and precise characterisation of the irregular diameter distribution of the degraded Gmelina arborea stands. The $-{\Lambda}{\Lambda}$, AIC, BIC and RMSE values ranged from -715.233 to -348.375, 703.926 to 1433.588, 718.598 to 1451.334 and 3.003 to 7.492, respectively. Their performances were relatively the same. This approach can be used to describe other irregular forest stand structures, especially the multi-species forest.

• PNF and Movement
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• v.9 no.1
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• pp.31-38
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• 2011

Purpose : Sit-to-stand (STS) is one of the important activities of daily living (ADL) and each of its parameters is used frequently. This study aimed to examine the influence of different seat height on performance time and floor reaction force strength during an STS movement. Methods : Fifteen young-adult male subjects participated in this study. The subjects were divided into three groups based on lower leg length. Subjects performed an STS movement twice from chairs at height adjusted by the lower leg length of each subject. To examine the influence of the chair seat height, ground reaction forces during a STS performed with 3 chair heights adjusted to each subjects lower leg length were compared. Results : Vertical ground reaction force and time during an STS movement were measured to evaluate. Parameters regarding ground reaction force were selected for analyses. Significant differences were found in ground reaction force at G1 was greater than G2 and G3. Conclusion : The STS movement achievement strategy differed since chair seat height changes relatively by the difference in lower leg length. When conducting the ability to achieve STS movement rating test, chair seat height considering each subject's lower leg length may be needed.

• ALGAE
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• v.37 no.1
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• pp.63-74
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• 2022

Perennial stipitate kelps are globally distributed and individual species can inhabit broad latitudinal ranges, expressing notably longevous persistence. Despite the foundational role kelps provide to their communities, little is known about the variability in persistence of the stipitate kelps at local spatial scales. We studied the population persistence of Eisenia arborea, a heat- and wave force-tolerant perennial stipitate kelp with a distributional range extending from British Columbia to south of the range limit of all other northeast Pacific kelps, in Baja California Sur, Mexico. Persistence characteristics for E. arborea among sites were compared and used to test the hypothesis that stand persistence varied at local spatial scales around Isla Natividad, a Pacific island off the Baja California peninsula with documented spatiotemporal environmental heterogeneity. Collected individuals around the island were "aged" using the previously validated age estimation technique of counting annual cortical dark rings. After detecting no significant differences among sites in the covariation between estimated ages for collected individuals and stipe length, we utilized in-situ population-level stipe length measurements to more rapidly predict age structures within six stands around the island. Predicted age structures, and associated stand densities, revealed persistence characteristics and density varied at local scales and a strong positive relationship existed between stand density and stand mean and maximum ages. We speculate that stands responded differently to deterministic influences (e.g., the 2014-2016 marine heatwave and / or competition with Macrocystis) resulting in heterogenous local persistence of this foundation species.