검색 상세

직접 구동형 풍력발전 시스템의 계통연계를 위한 제어 성능 개선

Improvement in Control Performances of Direct Drive Type Wind Power System for the Grid Connection

심준보 (JUN BO SIM, 포항공과대학교 풍력대학원)

원문보기

초록 moremore
These days, the world energy market has been interested in the development of new and renewable energy with the increase in the concern about atmospheric pollution and global warming by fossil fuels and the excessive demand on the energy. Among the new and renewable energies, wind power system has b...
These days, the world energy market has been interested in the development of new and renewable energy with the increase in the concern about atmospheric pollution and global warming by fossil fuels and the excessive demand on the energy. Among the new and renewable energies, wind power system has been increased in its extent as the alternative energy technology which the wind energy is converted to the electrical energy. In terms of the electrical problems, since the wind speed which is the energy resource of the wind turbine is changed irregularly according to the meteorological conditions the output of the wind turbine also changes irregularly and the fluctuation of the active power finally influences the power qualities of the connected grid such as the total harmonic distortion, frequency and power factor. The small scale wind power systems connected to the distribution line has been being changed to the large scale wind power systems connected to the transmission line along with the increased penetration of wind energy in the power system. In the case of grid connection to the AC line power transmission system, there could happen a variety of problems such as voltage stability, transient stability and the ripple effect of the faults which have not been considered in the small scale wind power systems. So, on the grid codes of the developed countries in wind power, the wind farms or the individual wind turbines connected to the grid are required to have various control strategies for the active contribution to the stable operation of the power system. The variable speed-variable pitch direct drive wind power system using full rated power converter and multi-poles permanent magnet synchronous generator is the noticeable wind power system due to its high efficiency at the low wind speed region as well as its easier maintenance and reliability. Besides, since the wind turbine and the grid are isolated by the full rated power converter the system has a good capability in the grid faults. Therefore in this thesis, the control capabilities based on the direct drive type wind power system using multi-poles PMSG are secured for the satisfaction with grid codes. Firstly, mechanical-electrical system is modeled to evaluate the power and the control performance of the wind turbine according to the wind speed and the control strategies for the cut-in through cut-out wind speed are explained. Starting from modeling the rotor effective wind speed at the hub height, non-linear aero-dynamic torque, two mass drive train, electrical system including PMSG, and pitch control system are modeled and the maximum power point tracking(MPPT) and pitch control are implemented according to the basic control strategies of the wind turbines. Secondly, controls and design of wind power system including the power converter to meet the grid codes of the advanced countries in wind power such as active-reactive power control, frequency control, an operation of the wind turbines when faults occur, and the power quality are discussed. For the active power and frequency control of wind farms, a concept of a wind farm controller is introduced and some control methods to meet the seven active power control standards and a frequency control standard. Particularly, the low voltage ride through(LVRT) regulation which is the remarkable issue is explained and the LVRT strategies for the grid connected PMSG wind turbines under the distorted-unbalanced grid conditions are introduced. Lastly, the control methods introduced in this thesis are verified by simulation and the characteristics of the wind power system using a full rated power converter are analyzed based on the simulation results. With the analyzed results, control strategies for the direct drive type wind power system using multi-poles permanent magnet synchronous generator and a full rated power converter are summarized and the direction of new researches is established.
목차 moremore
Abstract ..................................................................................................................... i
목차 ....................................................................................................................... iii
그림목차 ............................................................................................................... ⅶ
...
Abstract ..................................................................................................................... i
목차 ....................................................................................................................... iii
그림목차 ............................................................................................................... ⅶ
표 목차 ................................................................................................................... x
술어 및 약어............................................................................................................ xi
Ⅰ. 개요 ...................................................................................................................... 1
1.1 연구의 배경 ..................................................................................................... 1
1.2 연구의 목적 ..................................................................................................... 3
1.3 논문의 구성 ..................................................................................................... 5
Ⅱ. 계통연계 규정 ..................................................................................................... 6
2.1 유효전력 및 주파수 제어 ............................................................................. 7
2.1.1 유효전력 출력 제어 ................................................................................ 7
2.1.1.1 출력 증발률 제한 ............................................................................. 7
2.1.1.2 최대 출력 제한 ................................................................................. 8
2.1.1.3 출력 변화율 제한 ............................................................................. 8
2.1.1.4 수급균형 제어 ................................................................................... 9
2.1.1.5 출력 유지 제어 ................................................................................. 9
2.1.1.6 시스템 보호 ..................................................................................... 10
2.1.2 주파수 제어 ............................................................................................ 11
2.2 무효전력 제어 ............................................................................................... 12
2.3 LVRT규정 및 무효전력 공급 .................................................................... 14
2.3.1 LVRT 규정 .............................................................................................. 14
2.3.2 유∙무효전력 공급 .................................................................................. 17
2.3.3 계통의 사고 유형 .................................................................................. 19
2.4 전기 품질 ....................................................................................................... 22
2.4.1 전압 변동률 제한 .................................................................................. 23
2.4.2 플리커(Flicker) ........................................................................................ 24
2.4.3 고조파 왜곡(Harmonic Distortion) ........................................................ 25
Ⅲ. 풍력발전 시스템의 종류 ................................................................................. 27
3.1 풍력발전기의 종류 및 운전 방식 ............................................................. 27
3.1.1 발전기 회전축의 방향에 따른 분류 .................................................. 28
3.1.2 피치제어 방식에 따른 분류 ................................................................ 28
3.1.3 회전속도의 가변 유무에 따른 분류 .................................................. 29
3.2 풍력발전 시스템의 토폴로지 ..................................................................... 29
3.1.1 고정속도 운전방식 ................................................................................ 29
3.1.2 반가변속도 운전방식 ............................................................................ 31
3.1.3 가변속도 운전방식 ................................................................................ 32
Ⅳ. PMSG풍력터빈의 모델링과 제어 .................................................................. 35
4.1 바람 모델링 ................................................................................................... 35
4.2 블레이드 모델링 ........................................................................................... 36
4.3 드라이브 트레인 ........................................................................................... 38
4.4 피치 시스템과 제어기의 설계 ................................................................... 40
4.5 풍력발전기의 제어 전략과 MPPT기법 ................................................... 43
4.5.1 풍력발전기의 제어 전략 ...................................................................... 43
4.5.2 최대전력지점 추종(MPPT) ................................................................... 45
4.5.2.1 주속비(TSR) 제어 ........................................................................... 45
4.5.2.2 Hill Climbing Searching Control ....................................................... 46
4.5.2.3 출력신호 궤환 제어(PSF) ............................................................. 46
4.5.2.4 최대출력 상수를 이용하는 방법 ................................................. 47
4.6 풍력발전 단지의 유효전력 제어 ............................................................... 49
Ⅴ. 전력변환기의 설계와 제어 ............................................................................. 52
5.1 전력변환기의 파라미터 설계 ..................................................................... 52
5.1.1 LCL필터 설계 ........................................................................................ 52
5.1.1.1 승압용 인덕터의 결정 ................................................................... 54
5.1.1.2 필터 커패시턴스의 결정 ............................................................... 56
5.1.1.3 필터용 인덕턴스의 결정 ............................................................... 56
5.1.1.4 타당성 검증 ..................................................................................... 57
5.1.1.5 댐핑 저항의 결정 ........................................................................... 57
5.1.2 직류단 커패시터 설계 .......................................................................... 58
5.1.3 직류단 보호저항 설계 .......................................................................... 59
5.2 발전기측 컨버터의 제어 ............................................................................. 60
5.2.1 전류제어 .................................................................................................. 61
5.2.1.1 직류기의 전류 제어 ....................................................................... 61
5.2.1.2 영구자석 동기기의 전류제어 ....................................................... 63
5.2.2 토크제어 .................................................................................................. 64
5.3 계통측 컨버터의 제어 ................................................................................. 65
5.3.1 불평형 계통 전압의 해석 .................................................................... 66
5.3.2 PLL ........................................................................................................... 68
5.3.2.1 일반적인 PLL시스템 ..................................................................... 69
5.3.2.2 정상분 계통 전압을 이용한 PLL시스템 ................................... 72
5.3.3 전류제어 .................................................................................................. 73
5.3.4 직류단 전압제어 .................................................................................... 75
5.3.4.1 일반적인 직류단 전압제어기 ....................................................... 75
5.3.4.2 LVRT를 위한 직류단 전압제어기 .............................................. 77
5.3.5 무효전력의 제어 .................................................................................... 79
5.3.5.1 무효 전류의 제어 ........................................................................... 79
5.3.5.2 LCL-filter에 의한 역률 보상 ........................................................ 79
5.3.6 듀얼전류 제어기 .................................................................................... 81
5.3.7 고조파 전류 보상기법 .......................................................................... 82
5.4 풍력발전기의 LVRT전략 ........................................................................... 85
Ⅵ. 시뮬레이션......................................................................................................... 86
6.1 시뮬레이션 Parameter .................................................................................. 87
6.2 시뮬레이션 결과 및 분석 ........................................................................... 90
6.2.1 풍력터빈 출력파형 ................................................................................ 90
6.2.2 풍력단지의 유효전력 제어 출력 파형 .............................................. 92
6.2.2.1 출력 증발률 제한 ........................................................................... 93
6.2.2.2 최대 출력 제한 ............................................................................... 94
6.2.2.3 출력 변화율 제한 ........................................................................... 95
6.2.2.4 수급균형 제어 ................................................................................. 96
6.2.2.5 출력 유지 제어 ............................................................................... 97
6.2.2.6 시스템 보호 ..................................................................................... 98
6.2.2.7 주파수 제어 ..................................................................................... 99
6.2.3 풍력발전기의 LVRT파형 .................................................................. 100
6.2.3.1 단상 지락 사고 ............................................................................. 100
6.2.3.2 3상 지락 사고 ............................................................................... 102
6.2.3.3 불평형 계통 전압에서의 LVRT ................................................ 104
6.2.3.4 불평형-왜곡 계통전압에서의 LVRT ......................................... 106
6.2.3.5 Zero Voltage Ride Through ............................................................. 108
Ⅶ. 결론 .................................................................................................................... 61
참고문헌 ................................................................................................................... 62