계통 특성 기반 재생에너지 연계 기준 산정 방법론에 관한 연구 = A Study on a Methodology for Determining Renewable Energy Interconnection Requirement Levels Based on Power System Characteristics

다국어 초록 (Multilingual Abstract)

The increasing penetration of renewable energy resources and the expansion of power-electronics-based facilities are changing the frequency response characteristics of power systems. Wind and photovoltaic generation do not provide rotational inertia and governor-based primary frequency response in the same manner as conventional synchronous generators. Therefore, in high-renewable and low-inertia operating conditions, frequency stability issues such as frequency nadir deterioration, delayed frequency recovery, and insufficient ride-through capability of renewable energy resources may become critical. For this reason, renewable energy interconnection requirements need to be evaluated not only as minimum performance requirements for individual facilities, but also as technical requirements that contribute to maintaining frequency stability under actual system conditions.
This dissertation proposes a system-characteristic-based methodology for determining renewable energy interconnection requirement levels. The proposed methodology reflects that the required level of Grid Code performance may vary depending on system operating conditions and contingency conditions. To this end, domestic and international Grid Codes and frequency response requirements were reviewed, and Frequency Ride Through, post-fault active power recovery, Primary Frequency Response, and Fast Frequency Response were selected as the main evaluation items directly related to frequency stability. A procedure was then established in which the adequacy of the existing Grid Code is first evaluated as a baseline, and the minimum required performance level is determined by stepwise adjustment of active power recovery time, PFR headroom, FFR response magnitude, and response timing for cases that do not satisfy the stability criterion.
The proposed methodology was applied to the Jeju power system. The Jeju system is interconnected with the mainland system through HVDC links and has a relatively small system size and high renewable energy penetration. Therefore, it exhibits clear characteristics of a high-renewable and low-inertia system. In this study, BASECASE, vulnerable CASE, and future CFI CASE were established, and the adequacy of the existing renewable energy interconnection requirements and the required supplementary performance levels were evaluated under the same contingency condition. The frequency stability criterion was set to a post-contingency frequency nadir of 59.2 Hz, and the analysis focused on frequency nadir, time to frequency nadir, and active power recovery characteristics.
The simulation results showed that the BASECASE satisfied the frequency nadir criterion under the existing Grid Code. In the vulnerable CASE, the existing Grid Code was not sufficient to satisfy the stability criterion because of low-load operation and increased wind generation share. The results indicated that faster post-fault active power recovery and additional frequency response capability were required. In the vulnerable CASE, a wind power recovery time of 0.8 s, or a 5% level of PFR or FFR response, was identified as a condition capable of satisfying the stability criterion. In the future CFI CASE, the frequency response did not converge without a synchronous condenser. Even after applying a 100-MVA synchronous condenser, the frequency nadir criterion was not satisfied. This result confirms that renewable energy resources must provide improved active power recovery and frequency response capability together with sufficient synchronizing resources. In the future CFI CASE, the stability criterion was satisfied by a wind power recovery time of 0.5 s, a 10% level of single frequency response, or a combined response consisting of 5% PFR headroom and 10% FFR.
The results demonstrate that the adequacy of renewable energy interconnection requirements cannot be determined using a single fixed value. It depends on system operating conditions, post-contingency active power imbalance, renewable energy composition, availability of synchronizing resources, and the timing of frequency response formation. By distinguishing the conditions under which the existing Grid Code is sufficient from those requiring supplementary performance levels, this study provides a procedure for evaluating Grid Code requirements from the perspective of system frequency stability. The proposed methodology can serve as a basis for quantitatively assessing the system-support capability of renewable energy resources and for developing system-condition-based interconnection requirements for future high-renewable power systems.

목차 (Table of Contents)

• (Abstract)
• Ⅰ. 서 론 1
• 1.1 연구 배경 1
• 1.2 문제 정의 2
• 1.3 연구 필요성 3
• 1.4 연구 목적 6
• 1.5 연구 범위 7
• 1.6 논문 구성 8
• Ⅱ. 이론적 배경 및 선행연구 9
• 2.1 전력계통 주파수 안정도의 기본 개념 10
• 2.2 관성 저하와 고재생 계통의 주파수 응답 특성 12
• 2.3 고재생·저관성 계통의 안정도 이슈 13
• 2.4 Frequency Ride Through의 개념과 역할 14
• 2.5 사고 후 유효전력 회복 특성 15
• 2.6 PFR의 개념과 주요 요구요소 16
• 2.7 FFR의 개념과 주요 요구요소 19
• 2.8 국내외 기준 차이와 계통 조건 기반 평가 필요성 21
• 2.9 선행연구 검토 방향 및 본 연구의 차별성 23
• Ⅲ. 국내외 Grid Code 및 주파수 응답 요구사항 검토 24
• 3.1 국내 재생에너지 연계 기준의 주요 항목 25
• 3.1.1 국내 재생에너지 연계 기준의 개요 25
• 3.1.2 전압 및 주파수 운전범위 27
• 3.1.3 계통연계 유지 요구사항 29
• 3.1.4 사고 후 유효전력 회복 요구사항 34
• 3.1.5 무효전력 공급능력 및 제어방식 35
• 3.1.6 유효전력 제어 요구사항 37
• 3.1.7 주파수 추종운전 요구사항 38
• 3.2 IEEE 2800 기반 IBR 연계 요구사항 검토 40
• 3.2.1 Ride-Through 및 Active Power Recovery 요구사항 41
• 3.2.2 유효전력-주파수 제어 요구사항 45
• 3.2.3 PFR 요구사항 47
• 3.2.4 Fast Frequency Response 요구사항 51
• 3.2.5 IEEE 2800 검토 결과 및 시사점 53
• 3.3 호주 AEMO의 접속성능기준 및 주파수 응답 요구사항 54
• 3.3.1 접속성능기준 구조 54
• 3.3.2 AEMO 계통연계 유지 요구사항 56
• 3.3.3 AEMO PFR 요구사항 58
• 3.3.4 AEMO FFR 요구사항 60
• 3.3.5 호주 기준의 시사점 62
• 3.4 영국 NESO의 Dynamic Services 64
• 3.4.1 Dynamic Services의 운영 구조 65
• 3.4.2 Dynamic Containment 66
• 3.4.3 Dynamic Moderation 67
• 3.4.4 Dynamic Regulation 68
• 3.4.5 Dynamic Services의 주요 성능요소와 시사점 69
• 3.5 아일랜드 EirGrid/SONI의 저관성 계통 대응 73
• 3.5.1 All-island 계통의 저관성 운전 배경 74
• 3.5.2 DS3 System Services의 구성 75
• 3.5.3 FFR 및 Operating Reserve의 시간영역과 제공 요건 76
• 3.5.4 RoCoF 관리와 저관성 운전지표 80
• 3.5.5 아일랜드 사례의 시사점 82
• 3.6 해외 기준 검토 결과 및 시사점 84
• 3.7 본 연구의 검토 항목 선정 87
• Ⅳ. 재생에너지 연계 기준 요구수준 산정 방법론 90
• 4.1 방법론 기본 개념 90
• 4.2 본 연구의 현행 Grid Code 적용 조건 92
• 4.3 계통 조건 및 사고 조건의 설정 94
• 4.4 안정도 판단 기준 및 평가 지표 95
• 4.5 요구수준 산정 절차 96
• 4.6 항목별 요구수준 도출 방식 99
• 4.7 방법론의 적용 범위와 해석상 유의점 101
• Ⅴ. 제주계통 평가 CASE 및 해석 조건 102
• 5.1 분석 대상 계통 선정 103
• 5.2 검토 CASE 구성 방향 104
• 5.3 BASECASE 주요 조건 105
• 5.4 취약 CASE 주요 조건 107
• 5.5 미래 CFI CASE 주요 조건 109
• 5.6 해석 지표 및 결과 정리 방식 111
• Ⅵ. 제주계통 CASE별 해석 결과 및 요구수준 산정 112
• 6.1 분석 개요 112
• 6.2 BASECASE 현행 기준 적용 결과 113
• 6.3 취약 CASE 현행 기준 적용 결과 117
• 6.4 취약 CASE 요구수준 산정 결과 119
• 6.4.1 유효전력 회복시간 강화 효과 120
• 6.4.2 PFR Headroom 및 출력 상승시간 효과 123
• 6.4.3 FFR 적용 효과 132
• 6.4.4 PFR 및 FFR 복합적용에 따른 요구수준 검토 139
• 6.5 미래 CFI CASE 현행 기준 적용 결과 142
• 6.6 미래 CFI CASE 요구수준 산정 결과 145
• 6.6.1 유효전력 회복시간 강화 효과 146
• 6.6.2 PFR Headroom 및 출력 상승시간 효과 150
• 6.6.3 FFR 적용 효과 155
• 6.6.4 PFR 및 FFR 복합적용에 따른 요구수준 검토 157
• Ⅶ. 계통 조건별 요구수준 비교 및 일반화 160
• 7.1 CASE별 현행 기준 적용 결과 비교 160
• 7.2 CASE별 보완 요구수준 산정 결과 비교 162
• 7.3 계통 조건에 따른 요구수준 변화 요인 164
• 7.4 요구수준 산정 절차의 일반화 165
• Ⅷ. 결 론 167
• 8.1 연구결과 요약 168
• 8.2 연구의 기여 169
• 8.3 향후 연구과제 170
• 참고 문헌 171