• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.1
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• pp.65-76
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• 2024

With the recent activation of the offshore wind power industry, there has been a development of power plants with a scale exceeding 400MW, comparable to traditional thermal power plants. Renewable energy, characterized by intermittency depending on the energy source, is a prominent feature of modern renewable power generation facilities, which are structured based on controllable inverter technology. As the integration of renewable energy sources into the grid expands, the grid codes for power system connection are progressively becoming more defined, leading to active discussions and evaluations in this area. In this paper, we propose a method for selecting optimal reactive power compensation capacity when multiple offshore wind farms are integrated and connected through a shared interconnection facility to comply with grid codes. Based on the requirements of the grid code, we analyze the reactive power compensation and excessive stability of the 400MW wind power generation site under development in the southwest sea of Jeonbuk. This analysis involves constructing a generation site database using PSS/E (Power System Simulation for Engineering), incorporating turbine layouts and cable data. The study calculates reactive power due to charging current in internal and external network cables and determines the reactive power compensation capacity at the interconnection point. Additionally, static and dynamic stability assessments are conducted by integrating with the power system database.

• Journal of Power System Engineering
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• v.21 no.6
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• pp.31-39
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• 2017

In order to examine if met-masts wind data can exchange each other for wind resource assessment, an investigation was carried out in Kimnyeong and Haengwon regions of Jeju Island. The two regions are both simple terrain and 4.31 km away from each other. The one-year wind speed data measured by 70 m-high anemometers of each met-mast of the two regions were analysed in detail. Measure-Correlate-Predict (MCP) method was applied to the two regions using the 10-year Automatic Weather System (AWS) wind data of Gujwa region for creating 10-year Wind Statistics by running WindPRO software. The two 10-year Wind Statistics were applied to the self-met mast point for self prediction of Annual Energy Production (AEP) and Capacity Factor (CF) and the each other's met mast point for mutual prediction of them. As a result, when self-prediction values were reference, relative errors of mutual prediction values were less than 1% for AEP and CF so that met masts wind data under the same condition of this study could exchange each other for estimating accurate wind resource.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.12
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• pp.675-683
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• 2003

This paper describes the correction strategy of an overcurrent relay applied in the linked line for interconnecting wind farm with utility power networks in order to improve the capability of a fault detection. The fault current measured in a relaying point might vary according to the fault conditions. Generally, the current of the line to line fault or the line to ground fault in the linked line is much higher than the set value of protective relay due to the large fault level. However, when the high impedance fault occurs in the linked line, we can't detect it by conventional set value because its fault level may be lower than the generating capacity of wind farm. And, the protective relay with conventional set value may generate a trip signal for the insertion of wind turbine generators due to the large transient characteristics. In order to solve above problems and improve protective relaying algorithms applied in the linked line, we propose a new correction strategy of the protective relay in the linked line. The presented method can detect the high impedance fault which can't be detected by conventional relay set value and may prevent the mis-operation of protective relay caused by the insertion of wind farm.

• Journal of Power Electronics
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• v.15 no.4
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• pp.939-950
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• 2015

A single-stage AC-AC converter has been designed for a wind energy conversion system (WECS) that eliminates multistage operation and DC-link filter elements, thus resolving size, weight, and reliability issues. A simple switching strategy is used to control the switches that changes the variable-frequency AC output of an electrical generator to a constant-frequency supply to feed into a distributed electrical load/grid. In addition, a modified random sinusoidal pulse width modulation (RSPWM) technique has been developed for the designed converter to make the overall system more efficient by increasing generating power capacity and reducing the effects of inter-harmonics and sub-harmonics generated in the WECS. The technique uses carrier and reference waves of variable switching frequency to calculate the firing angles of the switches of the converter so that the three-phase output voltage of the converter is very close to a sine wave with reduced THD. A comparison of the performance of the proposed RSPWM technique with the conventional SPWM demonstrated that the power generated by a turbine in the proposed approximately increased by 5% to 10% and THD reduces by 40% both in voltage and current with respect to conventional SPWM.

• Journal of IKEEE
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• v.24 no.3
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• pp.691-698
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• 2020

The installation cost or the magnitude of the fault current varies depending on the grid connection method of the offshore wind farm. Therefore, there is a need for an efficient power grid connection method considering the capacity and location of the complex. In particular, most power cables in offshore wind farms use 3-core considering cost and efficiency. In the event of a failure such as a short circuit, the entire cable must be replaced, which can lead to significant losses in terms of cost, considering repair costs and turbine downtime. Therefore, in this paper, a radial, ring, and molding method is introduced into a 100 MW wind farm to be installed at Jeju offshore, and a three-phase short circuit failure is performed using a PSCAD/EMTDC program to perform computer analysis. I would like to propose a suitable power grid connection method.

• 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.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.1
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• pp.26-32
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• 2010

This paper proposes a new effective installed reserve rate in order to evaluate reliability of power system considering renewable generators, which include uncertainty of resource supply. It is called EIRR(effective installed reserve rate) in this paper. It is developed with considering capacity credit based on ELCC by using LOLE reliability criterion. While the conventional installed reserve rate index yields over-evaluation reliability of renewable generators, the proposed EIRR describes actual effective installed reserve rate. However, it is not the probabilistic reliability index as like as LOLE or EENS but another deterministic effective reliability index. The proposed EIRR is able to evaluate the realistic contribution to the reliability level for power system considering wind turbine generators and solar cell generators with high uncertainty in resource supply. The case study in model system as like as Jeju power system size presents a possibility that the proposed EIRR can be used practically as a new deterministic reliability index for generation expansion planning or operational planning in future.

• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1007-1015
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• 2017

This paper proposes a new control technique of energy storage system (ESS) for smoothing the active power of renewable energy sources (RES) such as photovoltaic and wind turbine generation. As the penetration of RES into grid increases, it is difficult to maintain the permissible level of power quality, that is, voltage and frequency fluctuation in power systems. To solve this problem, ESS control methods using low pass filter (LPF) have been proposed for mitigating the fluctuation of RES output. However, those have a lot of drawbacks which need to be supplemented. Hence, this paper presents the improved active power control with additional reactive power control for maintaining power quality properly. The proposed method minimizes the capacity of ESS to be required for smoothing RES output fluctuation through mitigation of phase delay problem in LPF. In addition, the voltage regulation improves by using additional reactive power control. The proposed method was verified through simulation analysis using PSCAD/EMTDC.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.9
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• pp.1174-1180
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• 2018

In December 2017, the government announced plans to increase the current proportion of renewable energy from 7% to 20% by 2030 through a plan called the Renewable Energy 3020 Implementation Plan. Therefore, the demand for installation of photovoltaic(PV), wind turbine(WT) and battery energy storage system(BESS) is expected to increase. In particular, the system combined with energy storage system(ESS) is expected to take up a large portion since PV and WT can receive high renewable energy certificates(REC) weights when combined with ESS. In this study, we calculate the optimal capacity of the power conditioning system(PCS) and the BESS by comparing the economical efficiency and maximize the efficiency of the PV-BESS system in which the PV and the BESS are connected. By analyzing the system marginal price(SMP) and REC, it maximize profits through application of REC weight 5.0 and optimal charge-discharge scheduling according to the SMP changes.

• International Journal of Advanced Culture Technology
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• v.3 no.1
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• pp.101-112
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• 2015

Renewable energy resources play an important part in the world's future. Renewable energy sources have the following components: biomass, geothermal, solar thermal, directs solar, wind, tidal and hydropower. Hydropower is still the most efficient way to generate electricity worldwide. Hydropower projects can contribute as a cheap energy source, as well to encourage the development of small industries across a wide range of new technology; furthermore hydropower systems use the energy in flowing and falling water to produce electricity or mechanical energy. Hydropower systems are classified as large, medium, small, mini and micro according to their installed power generation capacity, as do the following components: water turbines, control mechanisms and electrical transmissions. In this article a review of small hydropower systems has been done on the principles surrounding the fundamentals of hydraulic engineering, the fundamentals of hydrology, identification of sites and economic analysis.