직류배전망의 모델링과 고장해석에 관한 연구
A Study on Modeling and Fault Analysis of Low Voltage Direct Current Grid
- 주제(키워드) AC/DC converter , DC distribution grid , DC circuit-breaker , DER , DG , ESS , Fault analysis , Gaochang Testbed , Microgrid , Modeling , New and renewable energy , LVDC , Power conversion , PSCAD , PV , Short fault
- 발행기관 강릉원주대학교 일반대학원
- 지도교수 박철원
- 발행년도 2017
- 학위수여년월 2017. 8
- 학위명 석사
- 학과 및 전공 일반대학원 전기공학과
- 세부전공 전기공학
- 실제URI http://www.dcollection.net/handler/kangnung/000000009814
- 본문언어 한국어
- 저작권 강릉원주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
Worldwide, there is a growing interest in new and renewable energy due to atmosphere environmental issues and exhaustion of fossil fuels. Accordingly, national renewable energy pilot projects and regional energy projects are being implemented with national energy policies. Distributed enegy resources(Distributed generation), and renewable energy sources generate mostly direct current. If DC-based distribution systems are deployed, utility and convenience will increase significantly. Also, DC distribution is efficient because it can be connected directly to energy storage system(ESS). Due to the recent development of power electronics technology, large-capacity and high-efficiency power conversion is possible. Nowadays, integrate microgrid, and interest and research on DC distribution that can provide high quality and high reliability are increasing. In case of constructing DC distribution, even with minimum power conversion, generated power of distributed power source can be connected with DC distribution and can constitute system with high efficiency. Therefore, in order to provide highly reliable DC distribution grid, modeling and fault analysis of DC distribution according to fault simulation should precede. Through this paper, we will be able to it as a basic and effective data of the DC circuit breaker rating setting which will be developed through transient analysis and fault analysis of low voltage direct current distribution. First, the characteristics of DC distribution and the characteristics of fault current in case of short-circuit fault and ground fault are presented. Next, in order to verify the proposed short-circuit fault characteristics, the simulation result of PSCAD and the short fault characteristic equation were compared and examined. Also, we performed modeling and simulation through PSCAD program by converter station and PV with consideration of power converter. In the modeled DC distribution, the load was varied to 10[%], 50[%] and 80[%], fault currents were analyzed when a PtoP short fault occurred in each situation. And, the characteristics of fault currents were analyzed by simulating the short fault and ground fault at DC output side of system side AC/DC converter, short fault and ground fault at PV side, while varying the distance and fault resistance. Through the simulations of various conditions, the characteristics of the initial transient current and the fault current were analyzed and the current variation rate was calculated. At the end of the paper, the analysis results were derived. In conclusion, the results of this paper can be used as the basic and effective data for setting the breaker rating of the Gaochang Testbed in construction, In the future, we plan to explore protection and coordination to minimize the faults impact of DC distribution through detail modeling and simulation of DC distribution grid considering ESS and wind power.
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목 차
영문요약 ··················································································· i
목 차 ·················································································· iv
그림목차 ················································································· vii
표 목차 ·················································································· ix
1. 서론 ····················································································· 1
1.1 연구배경 ··········································································· 1
1.2 연구동향 ··········································································· 2
1.3 연구목적 ··········································································· 3
2. 직류배전망 ············································································· 4
2.1 직류배전과 교류배전 비교 ······················································· 4
2.2 직류배전망의 장점 및 문제점 ··················································· 6
2.3 직류배전망 구성방식 ····························································· 8
2.3.1 3상 AC/DC 컨버터 ···························································· 9
2.3.1.1 PWM 제어 ································································· 10
2.3.1.2 PLL 제어 ··································································· 11
2.3.2 PV ·············································································· 13
2.3.3 선로 및 DC 부하 ····························································· 14
2.4 직류배전망의 단락고장 고장특성 ··········································· 15
2.4.1 1단계 : DC-link 커패시터 방전 단계 ····································· 15
2.4.2 2단계 : 역병렬 다이오드 도통 단계 ······································· 17
2.4.3 3단계 : 계통으로부터의 전류 급전 단계 ·································· 18
2.5 직류배전망의 지락고장 고장특성 ··········································· 19
2.5.1 1단계 : DC-link 커패시터 방전 단계 ····································· 19
2.5.2 2단계 : 계통으로부터의 전류 급전 단계 ·································· 20
2.5.3 3단계 : 정상상태 단계 ······················································· 21
3. PSCAD를 이용한 직류배전망 모델링 ············································ 22
3.1 변환소의 모델링 ································································· 23
3.1.1 3상 AC/DC 컨버터 ·························································· 23
3.2 PV 모델링 ········································································ 27
3.3 DC 부하 ·········································································· 28
3.4 선로 ··············································································· 30
4. 직류배전망 시뮬레이션 및 고장해석 ·············································· 31
4.1 계통측 AC/DC 컨버터에서의 고장 사례 ····································· 32
4.1.1 단락고장시 시뮬레이션 및 과도해석 ······································ 32
4.1.1.1 PSCAD와 수식으로 계산된 고장전류 비교 ··························· 32
4.1.1.2 부하 변동에 따른 단락전류 비교 ······································· 35
4.1.1.3 고장거리에 따른 단락전류 비교 ········································ 36
4.1.2 지락고장시 시뮬레이션 및 과도해석 ······································ 38
4.1.2.1 고장저항에 따른 고장전류 비교 ········································ 39
4.2 PV측 DC/DC 컨버터에서의 고장 사례 ······································· 41
4.2.1 단락고장시 시뮬레이션 및 과도해석 ······································ 42
4.2.1.1 고장거리에 따른 단락전류 비교 ········································ 43
4.2.2 지락고장시 시뮬레이션 및 과도해석 ······································ 44
4.2.2.1 고장저항에 따른 고장전류 비교 ········································ 45
5. 결론 ··················································································· 47
참고문헌 ················································································· 49
