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An Analysis of Optimal Operation Strategy of ESS to Minimize Electricity Charge Using Octave

Octave를 이용한 전기 요금 최소화를 위한 ESS 운전 전략 최적화 방법에 대한 분석

  • Gong, Eun Kyoung (Department of Electrical Engineering, Hoseo University) ;
  • Sohn, Jin-Man (Department of Electrical Engineering, Hoseo University)
  • 공은경 (호서대학교 전기공학과) ;
  • 손진만 (호서대학교 전기공학과)
  • Received : 2018.01.26
  • Accepted : 2018.04.06
  • Published : 2018.04.30

Abstract

Reductions of the electricity charge are achieved by demand management of the load. The demand management method of the load using ESS involves peak shifting, which shifts from a high demand time to low demand time. By shifting the load, the peak load can be lowered and the energy charge can be saved. Electricity charges consist of the energy charge and the basic charge per contracted capacity. The energy charge and peak load are minimized by Linear Programming (LP) and Quadratic Programming (QP), respectively. On the other hand, each optimization method has its advantages and disadvantages. First, the LP cannot separate the efficiency of the ESS. To solve these problems, the charge and discharge efficiency of the ESS was separated by Mixed Integer Linear Programming (MILP). Nevertheless, both methods have the disadvantages that they must assume the reduction ratio of peak load. Therefore, QP was used to solve this problem. The next step was to optimize the formula combination of QP and LP to minimize the electricity charge. On the other hand, these two methods have disadvantages in that the charge and discharge efficiency of the ESS cannot be separated. This paper proposes an optimization method according to the situation by analyzing quantitatively the advantages and disadvantages of each optimization method.

수요관리를 통해 전기요금을 절감할 수 있다. 부하의 수요 관리 방법 중 하나로 ESS를 설치해 수요가 높은 시간대의 부하를 수요가 낮은 시간대로 옮기는 peak shifting을 사용함으로써 최대 부하를 낮추고 전력량 요금을 절감할 수 있다. 전기요금은 계약 용량 당 기본요금과 전력량 요금으로 이루어져있다. 전력량 요금을 최소화하기 위한 최적화 수행시 목적함수는 선형식으로 표현할 수 있으며, 기본 요금 최소화를 위한 목적함수는 이차식으로 표현할 수 있다. 선형식으로 표현된 목적함수에서는 ESS PCS(Power Conversion System)의 충, 방전 효율이 다른 경우를 다룰 수 없기 때문에 본 논문에서 충, 방전 효율이 다른 경우의 영향을 반영하고 혼합정수계획법(MILP, Mixed Integer Linear Programming)을 이용할 수 있는 정식을 제시하였다. 혼합정수계획법을 사용한 정식에서는 사전에 정해진 최대 부하 절감율에 대해 전기요금 최소화를 수행하게 되지만 최대 부하 절감과 전기요금 절감을 동시에 고려하기 위해서는 이차 계획법을 사용하는 것이 유용하다. 본 논문에서는 각 최적화 방법에 대한 장, 단점을 도시철도 변전소에 대한 시뮬레이션 결과를 정량적으로 비교분석하여 ESS 설비계획수립에 적합한 최적화 방법을 선택할 수 있는 근거를 제시하였다.

Keywords

References

  1. S. U. Agamah and L. Ekonomou, "Peak demand shaving and load-levelling using a combination of bin packing and subset sum algorithms for electrical energy storage system scheduling," IET Science, Measurement & Technology, vol. 10, no. 5, pp. 477-484, 201. DOI: https://doi.org/10.1049/iet-smt.2015.0218
  2. I. E. Commission, "Electrical energy storage white paper," Geneva, Switzerland: International Electrotechnical Commission, 2011.
  3. I. Papic, "Simulation model for discharging a lead-acid battery energy storage system for load leveling," IEEE Trans. Energy Convers., vol. 21, no. 2, pp. 608-615, 2006. DOI: https://doi.org/10.1109/TEC.2005.853746
  4. A. Purvins, I. T. Papaioannou, and L. Debarberis, "Application of battery-based storage systems in household-demand smoothening in electricity-distribution grids," Energy conversion and management, vol. 65, pp. 272-284, 2013. DOI: https://doi.org/10.1016/j.enconman.2012.07.018
  5. Z. Zhu, J. Tang, S. Lambotharan, W. H. Chin, and Z. Fan, "An integer linear programming based optimization for home demand-side management in smart grid," in Innovative Smart Grid Technologies (ISGT), 2012 IEEE PES, pp. 1-5: 2012.
  6. M. K. Gharigh, M. S. S. Abad, J. Nokhbehzaeem, and A. Safdarian, "Optimal sizing of distributed energy storage in distribution systems," in Smart Grid Conference (SGC) IEEE., pp. 60-65, 2015. DOI: https://doi.org/10.1109/SGC.2015.7857391
  7. D. P. Kothari, "Power system optimization," in Computational Intelligence and Signal Processing (CISP), 2012 2nd National Conference on IEEE., pp. 18-21, 2012. DOI: https://doi.org/10.1109/NCCISP.2012.6189669
  8. Jae-Haeng Heo, Seungkwon Shin, Jong-young Park and Hyeongig Kim, "Study on the Optimal Operation of ESS Considering Urban Railway Load Characteristic," The Transactions of the Korean Institute of Electrical Engineers., vol. 64, no. 10, pp. 1508-1516, 2015. DOI: https://doi.org/10.5370/KIEE.2015.64.10.1508
  9. D. Maly and K. Kwan, "Optimal battery energy storage system (BESS) charge scheduling with dynamic programming," IEEE Proceedings-Science, Measurement and Technology, vol. 142, no. 6, pp. 453-458, 1995. DOI: https://doi.org/10.1049/ip-smt:19951929