Design and analysis of wave energy converter for a buoy

Jin-Seok Oh,Jong-Do Kim,Jong-Ho Lee,Han-Il Park,Toshimitsu Komatsu 대한기계학회 2007 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.21 No.12

This paper introduces the design method for the practical use of a wave energy converter (WEC), and the associated results are application to the commercially available WEC for buoys. Peak performance of WEC occurs at resonance with driving waves. This type of resonance occurs when one of the parameters in an oscillator varies periodically. The water column in a WEC oscillates under the effect of gravity and the compression of an air chamber. The analysis of WEC is developed by assuming independence of the buoy heaving motion and the motion of the water column within the center cylinder. Results of analysis are then compared with simulation data, and applied to designing a WEC for buoys. Also, the effect of the various parameters such as cylinder length, period, mass and wave height is analyzed for the optimum design of a WEC. Finally, the research results are applied to a wave simulator with operating LabView, and some ideas are presented to the design method of WEC for buoy with simulation experiment.

진동수주형 파력발전 시스템을 탑재한 압축공기 주입식 방파제의 동적거동 해석

이광호(Lee, Kwang-Ho),김도삼(Kim, Do-Sam),육승민(Yook, Sung-Min),정영훈(Jung, Yeong-Hoon),정익한(Jung, Ik-Han) 한국해안해양공학회 2014 한국해안해양공학회 논문집 Vol.26 No.4

단독의 파력발전 변환장치(WEC)를 설치하는 경우 경제성이 떨어지는 문제점이 있으므로 기존 혹은 신설의 방파제에 WEC를 적용하여 파랑제어와 파랑에너지의 이용을 동시에 도모하는 방식이 많이 추진되고 있다. 본 연구는 방파제로 연구 개발된 압축공기 주입식 방파제에 진동수주형 파력발전시스템을 탑재한 경우 방파제로의 기능과 파력발전장치로의 기능을 병행하여 검토한다. WEC로써의 기능을 검토하기 위해서는 압축공기실에서 유출되어 WEC로 유입되는 압축공기 흐름속도가 정확히 평가될 필요가 있다. 따라서, 본 연구에서는 선형속도포텐셜이론에 기초한 경계요소법을, 압축공기 흐름해석에 Boyle법칙과 단열변화과정에 기초한 상태방정식을 각각 적용하여 수치시뮬레이션을 수행한다. 이로부터 얻어진 해의 타당성은 여러 형태의 구조물에 대한 기존의 수치해석결과 및 실험결과와의 비교로부터 검증되며, 실제의 수치해석에서는 진동수주형 파력발전시스템을 탑재한 고정식 및 부체식의 방파제에서 여러 파라미터들의 변화에 따른 파랑변형율, 구조물의 운동 및 공기흐름속도의 특성을 규명한다. 또한, 풍력발전시스템을 본 구조물에 복합적으로 적용할 수 있으므로 파력과 풍력을 동시에 구비한 복합발전시스템의 방파제로도 기대될 수 있다. As the economic matters are involved, applying the WEC, which is used for controlling waves as well as utilizing the wave energy on existing breakwater, is preferred rather than installing exclusive WEC. This study examines the OWC mounted on a pressurized air chamber floating breakwater regarding the functionality of both breakwater and wave-power generation. In order to verify the performance as a WEC, the velocity of air flow from pressurized air chamber to WEC has to be evaluated properly. Therefore, numerical simulation was implemented based on BEM from linear velocity potential theory as well as Boyle's law with the state equation to analyze pressurized air flow. The validity of the obtained values can be determined by comparing the previous results from numerical analysis and empirically obtained values of different shapes. In the actual numerical analysis, properties of wave deformation around OWC system mounted on fixed type and floating type breakwaters, motions of the structure with air flow velocities are investigated. Since, the wind power generating system can be hybridized on the structure, it is expected to be applied on complex power generation system which generates both wind and wave power energy.

점 흡수식 파력발전장치의 PTO 모델링에 따른 발전성능 특성 비교

노찬(Roh Chan),박지용(Ji-Young Park),하윤진(Yoon-Jin Ha),김경환(Kyung-Hwan Kim) 한국해양환경·에너지학회 2019 한국해양환경·에너지학회 학술대회논문집 Vol.2019 No.11

본 연구에서는 WEC-Sim를 이용하여 점 흡수식 파력발전장치에 대한 시간영역해석을 수행하였다. 또한 파력발전장치의 출력성능을 분석하기 위하여 WEC-Sim의 PTO-Sim을 이용하여 PTO를 모델링 하였다. 본 논문에서는 WEC-Sim의 선형 감쇠 계수를 이용한 PTO 시스템과 주파수 영역 해석을 통해 얻은 해석해 비교를 통한 WEC-Sim의 성능을 검증하였으며, PTO-Sim을 이용한 직접 구동 PTO 시스템 및 유압 PTO 시스템의 각 특성 및 제어 변수를 분석하고 제어 변수의 변화에 따른 발전 성능을 비교하였다. In this study, a time domain simulation was performed for a point absorber wave energy converter by using WEC-sim. In order to investigate the the output power, a PTO modeling by PTO-sim in WEC-Sim is applied on the time domain simulation. In this paper, the performance of WEC-Sim is verified through comparison between the PTO system using linear damping coefficient and the analysis obtained through frequency domain analysis. And each characteristics and control variable of direct drive PTO system and hydraulic PTO system is analyzed using PTO-Sim and compare the output power performance according to the change of control variable.

다중 공진을 이용한 이중 부이 파력발전장치의 모형실험

김정록(Jeong-Rok Kim),현종우(Jong-Wu Hyeon),고혁준(Hyeok-Jun Koh),권혁민(Hyuck-Min Kweon),조일형(Il-Hyoung Cho) 한국해양공학회 2015 韓國海洋工學會誌 Vol.29 No.2

In this study, we proposed a new type of dual-buoy wave energy converter (WEC) exploiting multi-resonance and analyzed the experimental results from a model test in a 2-D wave flume. A dual-buoy WEC using multi-resonance has two advantages: high efficiency at the resonant frequencies and the potential to extend the frequency range available to extract wave power from the WEC. The suggested WEC was composed of an outer buoy and an inner buoy sliding vertically inside the outer buoy. As the power take-off device, a linear electric generator (LEG) consisting of permanent magnets and coils fixed at each buoy was adopted. Electricity was produced by the relative heave motion between the two buoys. To search for the optimal shape of a dual-buoy WEC, we conducted experiments on the heave motion of a two-body system in regular waves without an LEG installed. Model tests with six combinations of experimental models were conducted in order to find the motion characteristics of a dual-buoy WEC. It was found that model 2, which included a ring-shaped appendage to move the resonant frequency of the outer buoy toward a high value, showed a higher relative heave response amplitude operator (RAO) curve than model 1. In addition, the double-peak shape of the heave RAO curve shown for model 2 indicated the extension of the frequency range for extracting wave power in irregular waves.

민주화변혁이후 동구권국가의 세계화 전략과 대외관계

안성호(Ahn, Sung-ho) 아시아·중동부유럽학회 2002 동유럽발칸학 Vol.4 No.2

The main theme of this paper is to discuss Foreign Relation and Global Strategy of Eastern Europe Countires(EECs) after Democratic Change. I will first review the historical relationship between Western European Countries(WECs), focusing on relation ship and cooperation with EU, NATO, OECD, and UN. Then I am going to discuss the new millennium vision and prospects of the relationship between the two areas. In fact, their formal relationship begins with the collapse of East European communism and NATO expansion policy in the late 90s. Through signs of change in EECs in the 90s, ① the Collapse of Communist block, ② the Unification of East and West Germany , ③ the vigorous capitalization of Eastern and Central Europe, ④ OECD membership of Hungary, Poland, and Czech republic(1996.3) ⑤ leading candidates for EU admission(1997), ⑥ NATO membership of Hungary, Poland, and Czech republic(1999.4), EECs were able to develop relationships in WECs. Considering these changes and focusing on the Foreign Relation and Global Strategy of EECs after Democratic Change, this paper will analyze the relationship between EECs and WECs in the 90s and new millennium. This paper suggests four folds of cooperation between EECs and WECs on the stage of international politics . The first place the two areas can cooperate is in the UN. Based on democracy and human rights, they can support and secure peace in the Balkan peninsula. The second place is EU focusing on economic cooperation. Initially, as the relationship between WECs and EECs began in the political dimension, marketization and capitalization in EU make EECs pay attention to the economic dimension. In October 2002, the EU executive committee announced that Hungary, Poland, Czech, Slovakia, Slobenia,Estonia, Latbia, and Lituania are EECs for EU admission. The third area of cooperation is military and international security. The time of hostile WTO(Warsaw Treatment Organization) and cold war based NATO competition has passed on to a new era in which NATO plays a sole important role in substituting the old international order. and Poland. In 2004, Baltic Countries, Slobenia, Slovakia, Romania, Bulgaria will be a member of NATO and a military alliance of western nations along with the Czech, Hungary, and Poland. The fourth place to cooperate is in OECD where Slovakia became its 30th member following Czech, Hungary, and Poland in 2000. Among the countries in EECs, the front-runner group is composed of Hungary, Czech, Poland, Slovakia, Baltics and Slovenia. In varying degrees the new democracies are being socialized to the West's culture of voluntary cooperation and the talking out of disputes. EECs will try to return to the west and maintain some distance from Russia and other CIS countries. EU does not finish restructuring the technical and financial limitation of economy, as we see problems of Globalization and restructuring process of EU system. And it will improve in near future, because EU has renovated EECs's outdated economic structure and made some positive achievements with increasing international trust. But some of EECs still has been increasing domestic political tension surrounding democratization and globalization. And problems of the Balkan peninsula should be solved through this peaceful democratic process. 89년 동구권민주화변혁이후 10여년간 대체로 체제변동의 흐름이 만족스러운 국가들은 헝가리, 체코, 폴란드, 슬로바키아, 슬로베니아, 발틱3국 등이라 할 수 있다. 대통령선거, 총선 등이 공정하고, 부정부패가 대체로 적으며,시장자본주의가 체계적이고, 서방의 투자가 많다. 인권문제나 민족분규, 소수민족문제 등도 평화적으로 원만하게 극복하고 있음을 볼 수 있다. 정치적 측면에서는 동구권국가의 민주화발전에서의 교훈, 세계화시대 평화를 위한 서방국가와의 동반자관계, 일부 동구권국가들의 NATO 가입과 세계평화를 위한 협력, 그리고 UN에서의 협력관계 등이 중요하다고 본다. 구사회주의체제에서 탈피하고있는 동구권국가들의 다양한 체제변동의 경험들이 다소 차이는 있으나 대체적으로 선거제도 확립, 경쟁적 정당제도입, 시장경제체제도입, 인권문제, 민족문제의 평화적․민주적 해결, 시민사회활성화, 세계화라는 측면에서 적응력을 보여주고 있다. 이를 우리는 동구권민주화 혁명이라고 부르고 있다.구사회주의권 국가들은 국내적으로는 시민사회형성, 경쟁적 정당정치제도화와 자유총선실시, 시장자본주의도입, 민족분규갈등과 인종청소, 국제적으로는 국제질서에의 적응과 세계화전략, UN, EU, NATO, OECD와의 관계, 지역내 국가간의 관계, 동구권과 러시아의 관계 등 통하여 10여 년 동안 체제변동의 이행과 공고화에서의 문제와 과제들을 표출하였다. 동구권국가들은 UN, OECD, EU, NATO, WTO 등에서의 새로운 협력과 민주화실천의 경험을 갖추고 있기 때문에 서방 선진국들이 이들 동구권 국가들에 대하여 민주주의를 잘 실천할 수 있도록 지원한다면 앞날의 전망은 매우 희망적이고 낙관적라고 볼 수 있다. 다만 발칸지역에서 경험한 바대로 민족분규와 내전은 동구권지역발전에 커다란 장애요인으로 작용하고 있다. 앞으로 동구권국가들은 시장경제도입과 발전, 물적, 기술적 경제교류증진, 동구권 EU 참여 및 경제협력관계, OECD에서의 관계 증진, NATO에서의 협력증진 등 EU국가들과의 협력할 과제들이 많이 있다. 동구권국가들의 오랜 역사, 정치, 경제, 문화적 잠재력은 상당하다고 보며 장기적으로 볼 때 대단한 잠재적 시장이라는 점에서 중요한 지역이라고 할 것이다. 시민사회 활성화, 민주주의제도화, 시장자본주의활성화, 민족문제극복, 그리고 국가전반의 투명성의 증대를 도모하고 EU와 NATO에 가입하면서 외교, 정보, 통상, 군사안보 측면에서 국익을 취함과 동시에 대외경쟁력을 더욱더 강화할때 동구권국가들은 세계화전략이 한층 더 성공적으로 추진될 것이다.

Numerical Hydrodynamic Analysis of a Wave Energy Convertor- Rotor in Irregular Waves

Sunny Kumar Poguluri(포구루리 써니 쿠마르),Dongeun Kim(김동은),Yoon Hyeok Bae(배윤혁) 한국신재생에너지학회 2021 한국신재생에너지학회 학술대회논문집 Vol.2021 No.7

In this study, performance assessment of the wave power absorption characteristics of an wave energy converter (WEC) rotor has been investigated using nonlinear – computational fluid dynamics (CFD) in irregular waves. Initially, the experimental results based on regular waves are used to validate the CFD results. Further, it has been extended to irregular waves where the primary focus is to check whether an optimum PTO loading can be achievable for the present WEC-rotor in irregular waves. The success of any WEC largely depends on the power take off (PTO) system which converts the mechanical energy into a more useful energy. For the purpose, the implementation and simulation of the damping mechanism is carried out by the coulomb damping which broadly replicate the PTO characteristics of a typical hydraulic system in irregular waves. The pitch response and rotational moment of the WEC-rotor in regular waves, shows the clockwise pitch motion is higher than the counter-clockwise pitch motion due to its unique asymmetric geometric configuration of the rotor. The major part of the study deals with the one-way PTO system that gives a torque only in one direction and compared with the two-way PTO system for the operational wave conditions.

Direct and Sensorless Grid Synchronization of DFIG—Control the Availability of WECS/HEPS for Disturbed Grid Requirements

Djoudi Abdelhak,Bacha Seddik,Iman-Eini Hossein,Rekioua Djamila 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.2

Grid integration of DFIG based-WECS/HPES has gained special attention in recent codes, especially under voltage disturbances. The main object of this requirement is to ameliorate the grid stability from the frequency point of view and increase the integration ratio of renewable energy conversion systems like WECS and HPES. The availability of such grid requirements depends heavily on the viability of the grid synchronization procedure of DFIG, which has not been thoroughly investigated under weak-grid conditions. It also depends on withstanding capacity of DFIG against over-voltages or so-called HVRT capability. In this regard, the present paper introduces a smooth and sensor-less grid synchronization strategy of DFIG under disturbed grid voltage to ensure HVRT capability. The feasibility of the proposed method is proved analytically and assessed via experimental and simulation results.

Power Quality Improvement Using Hybrid Passive Filter Configuration for Wind Energy Systems

O. Fatih Kececioglu,Hakan Acikgoz,Ceyhun Yildiz,Ahmet Gani,Mustafa Sekkeli 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.1

Wind energy conversion systems (WECS) which consist of wind turbines with permanent magnet synchronous generator (PMSG) and full-power converters have become widespread in the field of renewable power systems. Generally, conventional diode bridge rectifiers have used to obtain a constant DC bus voltage from output of PMSG based wind generator. In recent years, together advanced power electronics technology, Pulse Width Modulation (PWM) rectifiers have used in WECS. PWM rectifiers are used in many applications thanks to their characteristics such as high power factor and low harmonic distortion. In general, L, LC and LCL-type filter configurations are used in these rectifiers. These filter configurations are not exactly compensate current and voltage harmonics. This study proposes a hybrid passive filter configuration for PWM rectifiers instead of existing filters. The performance of hybrid passive filter was tested via MATLAB/Simulink environment under various operational conditions and was compared with LCL filter structure. In addition, neuro-fuzzy controller (NFC) was preferred to increase the performance of PWM rectifier in DC bus voltage control against disturbances because of its robust and nonlinear structure. The study demonstrates that the hybrid passive filter configuration proposed in this study successfully compensates current and voltage harmonics, and improves total harmonic distortion and true power factor.

Design and Experimental Validation of a Digital Predictive Controller for Variable-Speed Wind Turbine Systems

Badreddine Babes,Lazhar Rahmani,Abdelmadjid Chaoui,Noureddine Hamouda 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.1

Advanced control algorithms must be used to make wind power generation truly cost effective and reliable. In this study, we develop a new and simple control scheme that employs model predictive control (MPC), which is used in permanent magnet synchronous generators and grid-connected inverters. The proposed control law is based on two points, namely, MPC-based torque–current control loop is used for the generator-side converter to reach the maximum power point of the wind turbine, and MPC-based direct power control loop is used for the grid-side converter to satisfy the grid code and help improve system stability. Moreover, a simple prediction scheme is developed for the direct-drive wind energy conversion system (WECS) to reduce the computation burden for real-time applications. A small-scale WECS laboratory prototype is built and evaluated to verify the validity of the developed control methods. Acceptable results are obtained from the real-time implementation of the proposed MPC methods for WECS.

Design and Experimental Validation of a Digital Predictive Controller for Variable-Speed Wind Turbine Systems

Babes, Badreddine,Rahmani, Lazhar,Chaoui, Abdelmadjid,Hamouda, Noureddine The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.1

Advanced control algorithms must be used to make wind power generation truly cost effective and reliable. In this study, we develop a new and simple control scheme that employs model predictive control (MPC), which is used in permanent magnet synchronous generators and grid-connected inverters. The proposed control law is based on two points, namely, MPC-based torque-current control loop is used for the generator-side converter to reach the maximum power point of the wind turbine, and MPC-based direct power control loop is used for the grid-side converter to satisfy the grid code and help improve system stability. Moreover, a simple prediction scheme is developed for the direct-drive wind energy conversion system (WECS) to reduce the computation burden for real-time applications. A small-scale WECS laboratory prototype is built and evaluated to verify the validity of the developed control methods. Acceptable results are obtained from the real-time implementation of the proposed MPC methods for WECS.