• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.6
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• pp.497-505
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• 2016

Operating wind turbine generators at maximum power point requires maximum power point tracking (MPPT) control methods. However, conventional methods cannot track the appropriate maximum power point in situations involving wind turbine systems based on a series operation strategy. These systems comprise one or more local maximum power points, and conventional methods can detect only one local maximum power point closed by a current operation point. This study proposes an advanced MPPT method for the series operation strategy of a small, grid-connected wind turbine system. In determining the appropriate maximum point, operations at certain local maximum power points are analyzed. The results show one appropriate point, which is tracked by the proposed MPPT method. The effectiveness of the proposed method is verified by the experimental results.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 2007.05a
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• pp.154-157
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• 2007

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 2004.03a
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• pp.224-227
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• 2004

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2019.05a
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• pp.400-402
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• 2019

The electric point machine, which is used for the control of the turnout used to change the track of the train, is very important in the railway system. Various wired and wireless real-time monitoring systems are used to check the status of the point machine, but there is a possibility of malfunction due to sensor or network error. In this paper, a redundant monitoring system was designed that incorporates the point machine monitoring system and the CCTV camera control system to double check the operation of the point machine. In the point machine monitoring system, the operating state of the railway converter is monitored, alarmed and transmitted over the network. The CCTV camera control system, which received this information, was required to record the status of the turnout and the point machine in question and send it to the administrator. The manager of the railway line can check the conversion status of the railway through the monitoring screen for the railway line switcher first, and then confirm the switching status directly through the CCTV camera image, thereby improving the reliability of the point machine operation. It will also enable the safe and efficient operation of personnel for management. It is expected to contribute to preventing a derailment caused by a malfunction of the point machine.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.379-382
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• 2013

In conventional solar energy harvesting systems, continuous perturbation techniques of the duty cycle or switching frequency of a power converter have been used to implement MPPT(Maximum Power Point Tracking) control. In this paper, we propose a new MPPT technique to control the duty cycle of a power switch powering a power converter. The proposed circuit is designed in 0.35um CMOS process, and the designed chip area including pads is $770um{\times}800um$.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.11
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• pp.17-25
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• 2014

This paper proposes a novel maximum power point tracking (MPPT) system using a fuzzy logic control (FLC) algorithm for robust in-environment changing. The power available at the output of a photovoltaic (PV) cell continues to change with radiation and temperature because a solar cell exhibits nonlinear current-voltage characteristics. Therefore, the maximum power point (MPP) of PV cells varies with radiation and temperature. The MPPT methods are used in PV systems to make full utilization of the PV array output power, which depends on radiation and temperature. The conventional MPPT control methods such as constant voltage (CV), perturbation and observation (PO) and incremental conductance (IC) have been studied but these methods are problematic in that they fail to take into account the changing environment. The proposed FLC controller is based on the fuzzy control algorithm and facilitates robust control with the environmental changes. Also, the PV systems applied FLC controller is modeled by PSIM and the response characteristics of the FLC method according to environmental variations are analyzed through comparison with the performance of conventional methods. The validity of this controller is shown through response results.

• Journal of Periodontal and Implant Science
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• v.40 no.4
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• pp.164-171
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• 2010

Purpose: This study compared the total antioxidant status (TAS) and superoxide dismutase (SOD) activity in the saliva of periodontally compromised patients before and after scaling and root planing (SRP) to assess their diagnostic utility. Methods: Severe chronic periodontitis patient (test group) and subjects with no attachment loss, sites showing a 3 mm or more probing depth and a sulcus bleeding index < 10% (control group) were enrolled in this study. Saliva sampling and clinical examination were performed at one week, one month and 3 months after SRP. The TAS and SOD activity in each patient's saliva was measured for the comparative analysis between the groups. Results: In the test group, the TAS decreased directly after SRP. With time, it increased slightly and was relatively unchanged compared to the baseline. In the control group, the TAS also decreased immediately after SRP but increased gradually with time until 3 months. The SOD activity in the test and control subjects decreased immediately after SRP until 1 month. At 3 months, the SOD activity had increased. Both groups had a similar profile of SOD activity. However, the SOD activity of the control group was significantly higher than that of the test group at each point in time (P < 0.05). Conclusions: There was a significant difference in the total salivary antioxidant level between the periodontitis and healthy or gingivitis (control) group during the experiment period. The total antioxidant level in the saliva was higher in the patients with severe chronic periodontitis than the healthy or gingivitis control before SRP. The SOD activity of the periodontitis patients was lower than the control at each time point. These findings conclusively reveal the possible use of saliva as a diagnostic tool for periodontal health.

• Journal of Power Electronics
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• v.10 no.1
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• pp.79-84
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• 2010

This paper presents a grid connected photo-voltaic system using a quasi-Z-source inverter (QZSI) for power stage reduction. The power stage can be reduced because of an additional shoot-through stage which is a characteristic of QZSI. Therefore, by utilizing a QZSI the system's efficiency can be increased. In this paper, for applying a QZSI to a PV system, control methods such as maximum power point tracking (MPPT), point of common coupling (PCC) current control and PWM are studied and verified through simulation and experiment. In order to explain the above controllers, the characteristics of a QZSI are first analyzed. Then the MPPT control technique with a modified P&O method, the PCC current control for the regulation of the dc-link capacitor voltage and the PWM methods for the proposed system are explained. The feasibility of the proposed algorithm is verified through simulation and experiment with a 3kW system.

• Journal of Electrical Engineering and Technology
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• v.5 no.4
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• pp.606-613
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• 2010

This paper proposes a novel current-based maximum power point tracking (CMPPT) method for a single-phase photovoltaic power conditioning system (PV PCS) by using a modified incremental conductance method. The CMPPT method simplifies the entire control structure of the power conditioning system and uses an inherent current source characteristic of solar cell arrays. Therefore, it exhibits robust and fast response under a rapidly changing environmental condition. Digital phase locked loop technique using an all-pass filter is also introduced to detect the phase of grid voltage, as well as the peak voltage. Controllers of dc/dc boost converter, dc-link voltage, and dc/ac inverter are designed for coordinated operation. Furthermore, a current control using a pseudo synchronous d-q transformation is employed for grid current control with unity power factor. A 3 kW prototype PV PCS is built, and its experimental results are given to verify the effectiveness of the proposed control schemes.

• Journal of Biosystems Engineering
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• v.26 no.4
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• pp.371-378
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• 2001

This research devoted to develop an incubator that could make an optimum environment condition according to days of age for suckling pigs to decrease the mortality and improve the rate of the weight gain of the suckling pigs. Results obtained from this research summarized as follows: 1. Several experiments were carried out at the farm to find the effect of incubator developed for suckling pigs on weight gain by season. The total average gain of the weight of the treatment group was around 6∼22kg, and 6∼23kg higher than control group at the first experiment (April 19), at the second (July 30), and at the third (September 23), year of 2000 experiment, respectively. There were no significant differences ($\alpha$=5%) of the total weight gain among treatment groups. There was, however, a significant difference ($\alpha$=5%) of the total weight gain between the control and treatment groups and it was considered to be that the incubator had efficiency for weight gain of the suckling pigs. 2. The survival rate of the control group was 87% in the total sample number of 92, meanwhile, which of the experiment group was 98% in the total sample number of 50 suckling pigs. 3. Finally, economic analysis was executed for suckling pigs based on a farm size of breeding 500 sows. The results showed that a break-even point was around 9 months and the annual profit of ￦52,265,694 was expected after the break-even point.