학술논문
해상풍력발전단지 연계용 전압형 HVDC의 DC 전압 협조제어 전략 / Cooperative Control Strategy of DC Voltage for Voltage Source Converter HVDC Connected Offshore Wind Farm
Document Type
Dissertation/ Thesis
Author
Source
Subject
Language
Korean
Abstract
늘어나는 인구와 산업화의 발달로 신재생에너지원이 주목받고 있다. 이러한 신재생에너지원 중 풍력 발전은 대지이용률이 높고 발전단가가 낮아 관심이 고조되고 있다. 풍력발전은 초기에 육상 풍력단지 위주로 개발 되었으나 소음, 경관훼손, 환경 파괴 등의 문제로 인한 민원의 제기되었다. 또한 개발 부지의 한계로 대형 풍력발전기나 대규모 풍력단지 조성이 어려웠다. 이런 문제점을 해결하기 위해 최근 해상풍력발전단지가 건설되고 있다. 해상풍력은 육상풍력의 문제점을 해소 할 수 있을 뿐만 아니라, 바람의 질이 우수하여 높은 품질의 전기를 생산할 수 있다. 해상풍력발전단지가 계통에 연결되기 위해서는 계통의 안정성을 해치지 않는 범위 내에서 운전될 수 있도록 계통연계기준(Grid Code)이 만들어 졌고 이에 따른 안정적인 동작을 할 수 있어야 한다. 해상풍력발전단지는 전력을 계통으로 안정적으로 송전시키기 위해 직류송전 시스템을 HVDC(High Voltage Direct Current) 이용한다. 전압형 HVDC는 그리드 코드에 따라 제어가 가능하지만 계통 측에서 사고가 발생하였을 때, 통신시스템 없이는 해상풍력단지에서 사고를 감지하지 못하는 난점이 존재한다. 게다가, 그리드 코드에 따라 사고 시간 동안 HVDC와 계통의 연결을 유지하면 해상풍력발전단지에서 출력하는 유효전력이 계통 측으로 송전되지 못하고 DC 케이블에 쌓이게 되면서 HVDC의 DC 전압이 상승하는 문제점이 발생한다.본 논문에서는, 통신시스템이 무력화된 상황에서, 해상풍력단지에서 계통 사고를 감지하는 방안과 HVDC의 DC 전압 상승을 억제하기 위한 2가지 제어 전략을 제안 하였다. 계통 사고가 발생 하였을 때 순간적인 무부하 상황이 되므로 해상풍력발전단지와 HVDC 연계지점의 AC 전압이 상승하여 해상풍력발전단지에서 계통 사고를 감지 할 수 있다. AC 전압 상승값을 토대로 풍력발전기의 토크 출력을 감소시키고 DC 전압을 상승시키는 제어전략을 제안하였다. 제어 전략을 검증하기 위해 PSCAD/EMTDC 프로그램을 이용하여 풍력발전기와 전압형 HVDC를 모델링하고 제어전략을 시뮬레이션 하였다. 시뮬레이션 결과를 사례별로 분석 하였으며 사고 시 HVDC의 DC 전압 상승을 완화 시킬 수 있었다. 또한 계통 측으로 출력되는 유효전력 변동을 억제하여 계통의 안정화에도 기여하는 것을 확인 하였다.
Renewable energy sources are attracting attention as growing population and the development of industrialization. Wind power is initially focusing on the development of onshore wind farm, but was raised noise, landscape damage, caused by problems such as environmental degradation complaints. In addition, large wind turbines or wind power to limit the development of large-scale land just difficult compositions. Recent offshore wind power has been just built to solve this problem. Offshore wind farm is not only able to resolve the problem of the land wind, wind quality can produce excellent high-quality electricity. large-scale offshore wind farm is to be run within the scope of not impairing the system stability in order to be connected to a grid-connected system standards (Grid Code) has been created and should be able to stable operation accordingly. Offshore wind farms will use the HVDC(High Voltage Direct Current) transmission of power to reliably into the grid. Voltage Source Converter HVDC can be controlled in accordance with the grid code, Without communication systems, offshore wind farms are difficult to detect a grid fault. In addition, if an accident occurs, in accordance with the grid code grid side while keeping a connection with HVDC and grid, offshore wind farm has not been active power transmission to grid side, DC voltage of the HVDC DC-link occurs a problem that rises.In this paper, the communication system is disable conditions, a measure to detect grid fault in the offshore wind and two control strategy for suppressing the DC voltage rise of HVDC is proposed. Since the system is instantaneous no-load conditions under grid fault, offshore wind farms detect grid fault because the AC voltage of HVDC and offshore wind farm connection point rise. Based on the AC voltage rise, the control strategies for reducing the torque output and increasing the DC voltage are proposed. To verify the control strategies, using the PSCAD / EMTDC program, modeling and simulation of wind turbines and VSC HVDC. the simulation results are analyzed on a case-by-case basis, it was possible to alleviate the DC voltage rise of HVDC under grid fault. In addition, by suppressing the fluctuation of active power to be output toward the grid, it was found to contribute to the stabilization of power system.
Renewable energy sources are attracting attention as growing population and the development of industrialization. Wind power is initially focusing on the development of onshore wind farm, but was raised noise, landscape damage, caused by problems such as environmental degradation complaints. In addition, large wind turbines or wind power to limit the development of large-scale land just difficult compositions. Recent offshore wind power has been just built to solve this problem. Offshore wind farm is not only able to resolve the problem of the land wind, wind quality can produce excellent high-quality electricity. large-scale offshore wind farm is to be run within the scope of not impairing the system stability in order to be connected to a grid-connected system standards (Grid Code) has been created and should be able to stable operation accordingly. Offshore wind farms will use the HVDC(High Voltage Direct Current) transmission of power to reliably into the grid. Voltage Source Converter HVDC can be controlled in accordance with the grid code, Without communication systems, offshore wind farms are difficult to detect a grid fault. In addition, if an accident occurs, in accordance with the grid code grid side while keeping a connection with HVDC and grid, offshore wind farm has not been active power transmission to grid side, DC voltage of the HVDC DC-link occurs a problem that rises.In this paper, the communication system is disable conditions, a measure to detect grid fault in the offshore wind and two control strategy for suppressing the DC voltage rise of HVDC is proposed. Since the system is instantaneous no-load conditions under grid fault, offshore wind farms detect grid fault because the AC voltage of HVDC and offshore wind farm connection point rise. Based on the AC voltage rise, the control strategies for reducing the torque output and increasing the DC voltage are proposed. To verify the control strategies, using the PSCAD / EMTDC program, modeling and simulation of wind turbines and VSC HVDC. the simulation results are analyzed on a case-by-case basis, it was possible to alleviate the DC voltage rise of HVDC under grid fault. In addition, by suppressing the fluctuation of active power to be output toward the grid, it was found to contribute to the stabilization of power system.