• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.427-428
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• 2013

풍력발전과 같은 분산전원이 계통에 연계되어 운전될 경우, 계통연계 규정에 따라 운전해야 한다. 특히 계통사고에 의해 계통과 분리되었음에도 불구하고, 지속적으로 운전하는 것을 단독운전 이라 한다. 이러한 단독운전은 전기설비의 손상을 일으킬 수 있으므로 계통연계 규정에 따라 이를 빠르고 정확하게 검출하여야 한다. 본 논문에서는 이러한 단독운전을 검출하기 위해서 NDZ(Non-Detecton Zone)를 갖지 않는 고조파 주입 기법의 새로운 고조파 계산 및 검출 알고리즘 제안한다.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.288-289
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• 2010

다양한 신재생에너지의 발전원 확보를 위해서는 발전원의 출력 안정화가 필수적으로 수반되어져야 한다. 본 논문은 다양한 신재생에너지 발전원의 안정화를 위한 핵심기기 중 하나인 STATCOM의 설계 및 제작에 관한 내용이다. 개발 진행 중인 1MVA STATCOM은 제주도 행원 풍력발전의 전력품질을 개선하기 위해 설치될 예정으로 3-Level 인버터로 구성된 Stack과 LC 필터 그리고 변압기와 수배전반으로 구성되어 있다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.662-671
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• 2020

Recently, for the purposes of reducing carbon dioxide(CO₂) emissions in the island area, countermeasures to decrease the operation rate of diesel generator(DG) and to increase one of renewable energy sources(RES) is being studied. In particular, the demonstration and installation of stand-alone micro-grid(MG) system which is composed of DG, RES and energy storage system(ESS) has been implemented in some island areas such as Gapa-do, Gasa-do and Ulleung-do island. However, many power quality(PQ) problems may be occurred due to an intermittent output of RES including photovoltaic(PV) system and wind power(WP) system in a normal operating of constant voltage & constant frequency(CVCF) inverter-based MG system. Therefore, this paper presents a modeling of the 30kW scale MG system using PSCAD/EMTDC, and also implements a 30kW scale CVCF inverter-based MG system as test devices to analyze normal operating characteristics of MG system. From the simulation and test results, it is confirmed that the proposed methods are useful and practical tools to improve PQ problems such as under-voltage, over-voltage and unbalanced load in CVCF inverter-based MG system.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.473-474
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• 2016

최근 신재생에너지의 보급 정책으로 인해 태양광 또는 풍력과 같은 신재생에너지가 전체 전력 계통에서 차지하는 비율이 증가되고 있는 실정이다. 그러나 신재생에너지는 변동 적이기 때문에 계통의 안정성을 저해하는 원인이 될 수 있다. 이에 따라 각 나라에서는 계통 안정성을 위한 기능들을 요구하고 있으며, 그 요구는 점차 강화되고 있다. 이와 같이 신재생에너지 비율의 증가로 인해 계통 안정성에 대한 문제가 강조되고 있지만, 태양광 분산 발전 시스템의 경우에는 일사량에 의존하여 운전하기 때문에 일사량이 낮거나 야간에는 계통 안정성을 위한 기능을 수행하지 못하는 단점이 있다. 본 논문에서는 일사량이 낮거나 야간에도 계통 안정화를 위해 무효전력 지원이 가능한 확장된 무효전력 운전(EF-RPO: Extended feed-in Reactive Power Operation)방법의 제어 전략을 제안하며, 제안한 방식은 1MVA 계통 연계형 인버터의 제작과 실험을 통해 검증하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.4
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• pp.319-327
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• 2008

The demand of a three phase PWM inverter for the purpose of power control or grid-connecting is increasing. This inverter is connected to a grid through an L-filter or LCL-filter to reduce the harmonics caused by switching. An LCL-filter can reduce the harmonic of a low switching frequency and generate a satisfactory level of grid side current with a relatively low-inductance than an L-filter. But the additional poles caused by the LC part affects a stability problem due to induced resonance of the system. This paper presents a compensation method using a power theory to improve performance, the designed LCL-filter system and to reduce the stability problems caused by resonance. The effectiveness of the proposed algorithm is verified by simulations and experiments.

• Journal of Energy Engineering
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• v.12 no.4
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• pp.309-319
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• 2003

The main purpose of this paper is to present a simulation model for assessing the impacts of a variable speed wind turbine (VSWT) on the distribution network and perform a simulation analysis of volt-age profiles and harmonics along the wind turbine installed feeder using the presented model. The modeled wind energy conversion system consists of a fixed pitch wind turbine and a permanent-magnet synchronous generator, in which a controllable power electronics inverter performs variable speed operation and reactive power output control. Impact analysis on voltage profiles and harmonics of a VSWT-installed distribution feeder is addressed and simulated in terms of steady state and dynamic behaviors. Various capacities and different modes of variable speed wind turbines are simulated and investigated. Case studies demonstrate how feeder voltages are influenced by capacity and control modes of wind turbines and changes in wind speed under various network conditions, and show harmonic impacts on the feeder. Modeling and simulation analysis is based on PSCAD/EMTDC a software package.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.6
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• pp.579-585
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• 2014

10kW wind turbine is widely studied in the field of renewable energy for the merits of easy installation to the confined area such as hill, park and urban areas. The performance of various electrical devices such as converter and inverter in the wind turbine system should be systematically analyzed for various wind speeds. However, it is impossible to apply these devices directly to practical wind turbine system for the safety of wind turbine system. Therefore, it is required to develop torque simulator which can generate corresponding torque according to its wind speed. In this work, 10kW torque simulator which consists of three phase torque control inverter, 3 phase induction motor and PMSG(Permanent Magnet Synchronous Generator) is developed.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.1
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• pp.11-19
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• 2011

This paper describe development of a hardware simulator for the DFIG wind power system, which was designed considering wind characteristic, blade characteristic, and blade inertia compensation. The simulator consists of three major parts, such as wind turbine model using induction motor, doubly-fed induction generator, converter-inverter set. and control system. The turbine simulator generates torque and speed signals for a specific wind turbine with respect to the given wind speed which is detected by Anemometer. This torque and speed signals are scaled down to fit the input of 3.5kW DFIG. The MSC operates to track the maximum power point, and the GSC controls the active and reactive power supplied to the grid. The operational feasibility was verified through computer simulations with PSCAD/EMTDC. And the implementation feasibility was confirmed through experimental works with a hardware set-up.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.503-505
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• 2012

본 연구에서는 실증기능 구현을 위해 75KW로 설계된 리튬-폴리머배터리(Lithium Polymer Battery 이하 배터리)와 ESS(Energy Storage System) 내장형 Hybrid-PCS(이하 PCS)을 이용하여 불균일한 풍력 발전원에 대한 Smoothing 제어 및 정출력 제어 대한 연구를 진행 하였다. 잦은 전류 변동으로 인해 발생되는 출력 변동의 안정화를 위해 인버터 전류제어, 벅/부스트 전압제어 기법을 사용하였다. 최적의 Smoothing 제어를 위한 필터 계수 값을 찾기 위한 시험을 진행 하였으며 Energy shift을 위한 정출력 시험도 진행 하였다. 또한 각 제어 모드에서 ESS 중요 파라미터인 SOC(State Of Charge 이하 SOC)변화를 배터리 특성과 관련하여 분석해 보았다.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.2
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• pp.182-190
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• 2011

This paper proposes a LVRT (Low Voltage Ride Through) control strategy which should be satisfied by grid-connected wind power system when grid faults occur. The LVRT regulation indicates rules or actions which have to be executed according to the voltage dip ratio and the fault duration. Especially the wind power system has to support the grid with specified reactive current to secure the grid stability when voltage reduction ratio is over 10%. The LVRT regulation in this paper is based on the German Grid Code and full-scale variable speed wind power conversion system is considered for LVRT control strategy. The proposed LVRT control strategy satisfies not only LVRT regulation but also makes power balance between wind turbine and power system through additional DC link voltage regulation algorithms. Because it is impossible to control grid side power when the 3-phase to ground fault occurs, the DC link voltage is controlled by a generator side inverter using the DC link voltage control strategy. Through the simulation and experiment result, the proposed LVRT control strategy is evaluated and its effectiveness is verified.