• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.1
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• pp.78-83
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• 2014

Recently, a rapid growth of wind power system as a leading renewable energy source has compelled a number of companies to develop intelligent monitoring and diagnostic system. Such systems can detect early mechanical faults, which prevents from costly repairs. Generally, fault diagnostic system for wind turbines is based on vibration and process signal analysis. In this work, different type of mechanical faults such as mass unbalance and shaft misalignment which can always happen in wind turbine system is considered. The proposed intelligent fault diagnostic algorithm utilizes artificial neural network and Wavelet transform. In order to verify the feasibility of the proposed algorithm, mechanical fault generation experimental system manufactured by Gaon corporation is utilized.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.215-216
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• 2014

This paper proposes a control algorithm for permanent magnet synchronous generator with a back-to-back three-level neutral-point clamped voltage source converter in a medium-voltage offshore wind power system under unbalanced grid conditions. The proposed control algorithm particularly compensates for the unbalanced grid voltage at the point of common coupling in a collector bus of offshore wind power system. This control algorithm has been formulated based on the symmetrical components in positive and negative rotating synchronous reference frames under generalized unbalanced operating conditions. Instantaneous active and reactive power are described in terms of symmetrical components of measured grid input voltages and currents. Negative sequential component of ac input current is injected to the point of common coupling in the proposed control strategy. The amplitude of negative sequential component is calculated to minimize the negative sequential component of grid voltage under the limitation of current capability in a voltage source converter. The proposed control algorithm makes it possible to provide a balanced voltage at the point of common coupling resulting in the generated power of high quality from offshore wind power system under unbalanced network conditions.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.4
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• pp.707-714
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• 2010

When problems such as line fault, breakdown of a substation or a generator, etc. arise on the grid, the Microgrid is designed to be separated or isolated from the grid. Most existing DGs(Distributed Generators) in distribution system use rotating machine. However, new DGs such as micro gas turbine, fuel cell, photo voltaic, wind turbine, etc. will be interfaced with the Microgrid through an inverter. So the Microgrid may have very lower inertia than the conventional distribution system. By the way, the rate of change of frequency depends on the inertia of the power system. Moreover, frequency has a strong coupling with active power in power system. Because the frequency of the Microgrid may change rapidly and largely during transient, appropriate and fast control strategy is needed for stable operation of the Microgrid. Therefore, this paper presents a power balancing strategy in Microgrid during transient. Despite of strong power or frequency excursions, power balancing in the Microgrid can be maintained.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.1
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• pp.16-22
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• 2015

As the development of Battery Energy Storage System(BESS) and the increasing of intermittent energy sources like wind power and photovoltaic, the application of BESS in load frequency control is considered as an effective method. To evaluate the effectiveness of BESS application in frequency control, we defined a governor free model of BESS to conduct dynamic simulation. Using the BESS dynamic model, we implemented the power system dynamic model including steam, gas and hydro turbine generators. In this paper we study the control performance of BESS in primary frequency control. The effect of BESS speed regulation rate and response time on governor free operation is investigated. In addition, we compared BESS from steam turbine generator in view point of frequency regulation.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.4
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• pp.66-72
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• 2005

In this paper, a small supersonic wind tunnel is designed and built to study the flow characteristics of a supersonic impulse turbine cascade. The flow is visualized by means of a single pass Schlieren system. The supersonic cascade with 2-dimensional supersonic nozzle was tested for various blade leading edge shapes and gaps between the nozzle and cascade. Highly complicated flow patterns including shocks, nozzle-cascade interaction and shock boundary layer interactions are observed.

• Nuclear Engineering and Technology
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• v.47 no.4
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• pp.461-471
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• 2015

Recently, the estimation of the social cost of energy sources has been emphasized as various novel energy options become feasible in addition to conventional ones. In particular, the social cost of introducing measures to protect power-distribution systems from power-source instability and the cost of accident-risk response for various power sources must be investigated. To account for these risk factors, an integrated societal risk assessment framework, based on power-uncertainty analysis and accident-consequence analysis, is proposed. In this study, we applied the proposed framework to nuclear power plants, solar photovoltaic systems, and wind-turbine generators. The required capacity of gas-turbine power plants to be used as backup power facilities to compensate for fluctuations in the power output from the main power source was estimated based on the performance indicators of each power source. The average individual health risk per terawatt-hours (TWh) of electricity produced by each power source was quantitatively estimated by assessing accident frequency and the consequences of specific accident scenarios based on the probabilistic risk assessment methodology. This study is expected to provide insight into integrated societal risk analysis, and can be used to estimate the social cost of various power sources.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.433-436
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• 2010

In this paper, heat/mass transfer characteristics on a film cooled stationary rotor blade are investigated using the naphthalene sublimation method. A row-speed annular wind tunnel with a single annular turbine stage is used. Three rows of film cooling holes are machined on the leading edge of the test blade. Detailed heat/mass transfer distributions are measured with changing the blowing rate from 1.0 to 2.0. As the blowing ratio increases, overall heat/mass transfer increases and the lower peak formed on the pressure side were disappeared.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.547-553
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• 1989

Last several stages of high capacity fossil power steam turbine and most stages of nuclear power steam turbine operate on wet steam. As a consequence, the flows in those cascades are accompanied by condensation, and the latent heat caused by condensation affects an oblique shock wave being generated at the vicinity of trailing of the blade. In the case of expanding of moist air through a suction type indraft wind tunnel, the effect of condensation affection the oblique shock wave generated by placing the small wedge into the supersonic part of the nozzle was investigated experimentally. In these connections, the relationship between condensation zone and reflection point of the incident oblique shock wave, angle between wedge bottom wall and oblique shock wave, and the variations of angles of incident and reflected shock waves due to the variation of initial stagnation relative humidity are discussed. Furthermore, the relationship between initial stagnation relative humidity and load working on the nozzle wall, obtained by measuring static pressure at the nozzle centerline, is discussed.

• Journal of the Korean Geosynthetics Society
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• v.21 no.2
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• pp.49-56
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• 2022

This study conducted to obtain the lateral resistance of a wind power foundation reinforced with piles through an model experiment. In particular, the lateral resistance of the foundation was compared with the existing gravity-type wind power foundation by integrating the pile, the wind power generator foundation, and the rocky ground. In addition, changes in the lateral resistance and bending moment of the pile were analyzed by embeded depths of the pile. As a result, it was found that the lateral resistance increased with the depth of embedment of the piles. In particular, the pile's resistance increase ratio was 2.11 times greater in the case where the pile embedded up to the rock layer than the case where the pile was embedded into the riprap. It was found that the location of the maximum bending moment occurred at the interface between the wind turbine foundation and the riprap layer when the pile embeded to the rock layer. Through this, as the lateral resistance of the wind power foundation reinforced with piles is greater than that of the existing gravity-type wind power foundation, it is understood that it can be a more advantageous construction method in terms of safety.

• Wind and Structures
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• v.36 no.4
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• pp.237-247
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• 2023

The emergence of high-rise buildings has necessitated frequent structural health monitoring and maintenance for safety reasons. Wind causes damage and structural changes on tall structures; thus, safe structures should be designed. The pressure developed on tall buildings has been utilized in previous research studies to assess the impacts of wind on structures. The wind tunnel test is a primary research method commonly used to quantify the aerodynamic characteristics of high-rise buildings. Wind pressure is measured by placing pressure sensor taps at different locations on tall buildings, and the collected data are used for analysis. However, sensors may malfunction and produce erroneous data; these data losses make it difficult to analyze aerodynamic properties. Therefore, it is essential to generate missing data relative to the original data obtained from neighboring pressure sensor taps at various intervals. This study proposes a deep learning-based, deep convolutional generative adversarial network (DCGAN) to restore missing data associated with faulty pressure sensors installed on high-rise buildings. The performance of the proposed DCGAN is validated by using a standard imputation model known as the generative adversarial imputation network (GAIN). The average mean-square error (AMSE) and average R-squared (ARSE) are used as performance metrics. The calculated ARSE values by DCGAN on the building model's front, backside, left, and right sides are 0.970, 0.972, 0.984 and 0.978, respectively. The AMSE produced by DCGAN on four sides of the building model is 0.008, 0.010, 0.015 and 0.014. The average standard deviation of the actual measures of the pressure sensors on four sides of the model were 0.1738, 0.1758, 0.2234 and 0.2278. The average standard deviation of the pressure values generated by the proposed DCGAN imputation model was closer to that of the measured actual with values of 0.1736,0.1746,0.2191, and 0.2239 on four sides, respectively. In comparison, the standard deviation of the values predicted by GAIN are 0.1726,0.1735,0.2161, and 0.2209, which is far from actual values. The results demonstrate that DCGAN model fits better for data imputation than the GAIN model with improved accuracy and fewer error rates. Additionally, the DCGAN is utilized to estimate the wind pressure in regions of buildings where no pressure sensor taps are available; the model yielded greater prediction accuracy than GAIN.