신뢰도 및 경제성 평가를 이용한 전력계통 계획 수립에 관한 연구

Abstract

전력산업의 환경은 전력산업 구조개편, 전력거래 시장의 활성화, 환경규제, 지역간 전력연계, 계통의 대규모화와 복잡화 등의 요인으로 급격하게 변화하고 있다. 이러한 전력산업 변화는 전력산업 참여자들에게 상황에 따른 전력을 달리하는 이익최대화에 몰두하게 하였다. 그 결과 전력 시스템 계획자들은 전력시스템이 비용 효율적이고, 신뢰성 있게 동작하도록 설계하길 요구받게 되었다. 따라서 전력 시스템 계획자들은 기존의 신뢰도 위주의 전력계통계획에서 경제적 관점의 효율적인 전력계통계획이 절실히 요구되고 있다. 전력계통계획은 계통을 안정적으로 운영하기 위한 신뢰도 평가와 최적 비용투자를 고려한 경제성 평가를 고려하게 되었다. 현재 전력계통계획을 위한 다양한 연구가 진행 중이며, 중․장기간의 투자비, 설비 신설에 대한 계통 신뢰성, 전력공급의 안정성 등은 계획안을 위해 고려되는 사항들이다. 특히, 전력시장이 도입되어 있는 전력계통에서의 전력계통 운영자 및 계획자들은 계통의 신뢰도와 경제적 효율성을 동시에 제고함에 따라 송전망 소유자에게 송전 설비투자를 강제할 수 있는 환경을 조성하기 위해 다양한 평가방법을 개발 및 운영하고 있다. 그러나 전력계통은 비선형성, 불확실성, 생산과 수요의 동시성 등 여러 복합적인 특성을 가지고 있으므로, 전력계통의 분석 과정에서 많은 요소들을 고려로 인해, 그 해석에 많은 문제를 노출하고 있다. 그 결과 다양한 전력계통 계획을 위한 방안들이 존재해 왔지만, 실제 전력운영자들이나 계통 계통계획자들에게 명확한 해를 제시하지 못하고, 알고리즘의 제안 수준에서 그치고 있는 실정이다. 따라서 본 논문에서는 “전력계통의 해석”, “전력계통의 분석”, “전력계통계획의 비교”, “전력계통 계획의 최적 대안선정”이라는 전력계통계획의 수립 순서에 따라, 신뢰도와 경제성을 고려한 전력계통 계획 수립 방안을 제시하고자 한다. 각 단계별로 모선을 중심으로 한 전력계통 재구성 방안으로 전력계통을 해석하며, 두 종류의 신뢰도 지수를 이용하여 전력계통을 신뢰도 평가하며, 이를 토대로 후보군을 screening 하는 기법을 소개하고, 전력설비의 신설로 인해 영향을 받는 경제성 평가 요인을 선정하여 신뢰도 기준을 충족하는 후보 간의 경제성 평가를 통해 최적 대안을 제시하는 방안을 제시한다. 본 논문에서 제시하는 각 세부적인 기법들과 최적 대안 선정방안을 IEEE RTS 24-Bus system과 제주계통의 전력계통계획을 이용하여 검증하였으며, 본 논문의 실효성을 입증하였다. |For last some years, power system needs to meet the rapid growing electric demand and future power supply while overcoming a set of economic and technical constraints. The power system planners should address the concerns such as broadening and strengthening the existing situation, which is named as the Power System Expansion Planning. However, it is very difficult to obtain the optimal alternate of expansion planning problem regarding generating units, transformers, transmission lines and other network facilities at the same time due to complexity of power system. Therefore various methods have been introduced to demonstrate the reasonable application to practical Power system expansion planning and can be classified by using the mathematical optimization models and heuristic methods. Within the framework stated above, Power system expansion planning problem determines the installation place and planning horizon of power system facilities using economic assessment method whose goal is the minimization of cost or social welfare maximization. This dissertation explains a probabilistic approach of reliability evaluation and economic assessment for solving power system expansion planning problems. Three methods are proposed for this plan, which are reorganizing the existing power system focused on the buses of interest, selecting candidates using modified system operating state method, and finally choosing the optimal alternative using cost-optimization method. The concepts of inner and outer generators are introduced and two power distribution factors are proposed for outer generators and transmission lines, in addition to power tracing method which is introduced to calculate the contributions of individual generators and loads to line flows in reference. System operating state method is modified in this paper with the corresponding state reliability indices according to the expected capacities and probabilities for the cases of normal and (N-1) contingencies, respectively, in order to make the choice of candidates among the transmission lines connected between sufficient and insufficient buses which are defined by state reliability indices. A series of these processes is provided to be substituted for existing screening method. Thereafter, economic assessment by using cost-optimization is performed for selecting the optimal alternative among the chosen candidates. The case studies are carried out with modified IEEE-24 bus system and Jeju island power system expansion plan in Korea, to verify the proposed methodology.; For last some years, power system needs to meet the rapid growing electric demand and future power supply while overcoming a set of economic and technical constraints. The power system planners should address the concerns such as broadening and strengthening the existing situation, which is named as the Power System Expansion Planning. However, it is very difficult to obtain the optimal alternate of expansion planning problem regarding generating units, transformers, transmission lines and other network facilities at the same time due to complexity of power system. Therefore various methods have been introduced to demonstrate the reasonable application to practical Power system expansion planning and can be classified by using the mathematical optimization models and heuristic methods. Within the framework stated above, Power system expansion planning problem determines the installation place and planning horizon of power system facilities using economic assessment method whose goal is the minimization of cost or social welfare maximization. This dissertation explains a probabilistic approach of reliability evaluation and economic assessment for solving power system expansion planning problems. Three methods are proposed for this plan, which are reorganizing the existing power system focused on the buses of interest, selecting candidates using modified system operating state method, and finally choosing the optimal alternative using cost-optimization method. The concepts of inner and outer generators are introduced and two power distribution factors are proposed for outer generators and transmission lines, in addition to power tracing method which is introduced to calculate the contributions of individual generators and loads to line flows in reference. System operating state method is modified in this paper with the corresponding state reliability indices according to the expected capacities and probabilities for the cases of normal and (N-1) contingencies, respectively, in order to make the choice of candidates among the transmission lines connected between sufficient and insufficient buses which are defined by state reliability indices. A series of these processes is provided to be substituted for existing screening method. Thereafter, economic assessment by using cost-optimization is performed for selecting the optimal alternative among the chosen candidates. The case studies are carried out with modified IEEE-24 bus system and Jeju island power system expansion plan in Korea, to verify the proposed methodology.