• 전기학회논문지
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• 제66권2호
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• pp.292-299
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• 2017

In this paper, multiple ESS(Energy Storage System) control strategy for microgrids is presented. Installation of ESS becomes mandatory when microgrids are used to supply high quality power to the loads. The one of main functions of the ESS is to maintain power balance. However ESS has limitation of its capacity and instantaneous injecting power. Power allocation method based on SOC(State Of Charge) of each ESS is proposed. P-Q control is employed as the basic control strategy for the distributed ESSs. By using the proposed method, the coefficients in the conventional P-Q control method are modified. The ESSs with higher SOC inject more active power, while those with lower SOC inject less, leading to more balanced SOC levels among the ESSs. The proposed method is demonstrated by simulation using PSCAD/EMTDC.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.569-575
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• 2017

This paper proposes a method to utilize an energy storage system (ESS) based on the assessment of an area of severity (AOS) to voltage sag. The AOS is defined as a set of the fault positions that can cause voltage sags at many buses simultaneously. The assessment of AOS helps to determine an optimal location of ESS installation to minimize the expected sag frequency (ESF) at concerned buses. The ESS has the ability not only to play traditionally known roles but also to mitigate voltage sag impact on renewable energy sources (RES) in the islanded microgrid. Accordingly, using the proposed method the ESS has additional features to prevent the operation failure of RESs and improve the stability of the microgrid. In order to verify the presented method, a case study was conducted on the sample microgrid system that is modified from an IEEE 57-bus system.

• 전기학회논문지
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• 제67권2호
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• pp.158-164
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• 2018

Wind power forecast is critical for efficient power system operation. However, wind power has high forecasting errors due to uncertainty caused by the climate change. These forecasting errors can have an adverse impact on the power system operation. In order to mitigate the issues caused by the wind power forecasting error, wind power curtailment and energy storage system (ESS) can be introduced in the power system. These methods can affect the economics of wind power resources. Therefore, it is necessary to evaluate the economics of the methods for mitigating the wind power forecasting error. This paper attempts to analyze the economics of wind power curtailment and ESS operation for mitigating wind power forecasting error. Numerical simulation results are presented to show the economic impact of wind power curtailment and ESS operation.

• 한국태양에너지학회 논문집
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• 제37권6호
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• pp.59-68
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• 2017

In accordance with the policy of local government, the large scale of wind farms have been installed in Jeju power system. However, The intermittent characteristics of wind power output may cause grid voltage and frequency variation, especially in weak power system. One of the solution to solve this problem is installation of Energy storage system (ESS). In this case, the ESS will regulate the active power generated from wind farm to mitigate fluctuation. Actually, the local government of Jeju island constructed ESS connected to Hangwon wind turbine in 2016. From this point, this paper analyzes requirement capacity of ESS to mitigate wind power fluctuation based on measured data from Hangwon wind turbine and ESS. The simulation results will be carried out by Matlab program.

• 전력전자학회논문지
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• 제23권2호
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• pp.94-100
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• 2018

Generally, in a single-phase energy storage system (ESS) for households, AC ripple component with twice the fundamental frequency exists inevitably in the DC link voltage of single-phase PCS. In the grid-connected mode of a single-phase inverter, the AC ripple component in the DC link voltage causes low-order harmonics on grid-side current that deteriorates power quality on an AC grid. In this work, a control system adopting a feedforward controller is established to eliminate the AC ripple interference on the DC link side. Optimal battery nominal voltage design method is also proposed by considering the voltage loss and AC ripple voltage on DC link side in a single-phase ESS. Finally, the control system and battery nominal voltage design method are verified through simulations and experiments.

• 전기학회논문지
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• 제67권10호
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• pp.1278-1285
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• 2018

For saving electricity bill, energy storage system(ESS) is being installed in factories, public building and commercial building with a Time-of-Use(TOU) tariff which consists of demand charge(KRW/kW) and energy charge(KRW/kWh). However, both of peak reduction and ESS special tariff are not considered in an analysis of initial cost payback period(ICPP) on ESS. Since it is difficult to reflect base rate by an amount of uncertain peak demand reduction during mid-peak and on-peak periods in the future days. Therefore, the ICPP on ESS can be increased. Based on this background, this paper presents the advanced analysis method for the ICPP on ESS. In the proposed algorithm, the representative days of monthly electricity consumption pattern for the amount of peak reduction can be found by the k­means clustering algorithm. Moreover, the total expected energy costs of representative days are minimized by optimal daily ESS operation considering both peak reduction and the special tariff through a mixed-integer linear programming(MILP). And then, the amount of peak reduction becomes a value that the sum of the expected energy costs for 12 months is maximum. The annual benefit cost is decided by the amount of annual peak reduction. Two simulation cases are considered in this study, which one only considers the special tariff and another considers both of the special tariff and amount of peak reduction. The ICPP in the proposed method is shortened by 18 months compared to the conventional method.

• 전기학회논문지
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• 제63권12호
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• pp.1752-1758
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• 2014

This paper evaluates economic benefits of ESS (Energy Storage System) for peak load shaving in the substation of urban railway. For this purpose, the method to determine capacities of ESS and PCS (Power Conditioning System) for peak load shaving is proposed. Then the economic benefits of those devices are evaluated using net present value method. The proposed methods are applied to actual measurements of loads in the substation of urban railway. The results show that electric power costs can be reduced and the economic benefits of ESS for peak load shaving mainly depends on the price of battery.

• 전기학회논문지
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• 제63권6호
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• pp.860-865
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• 2014

This paper proposes the method for determination of the capacities of ESS (Energy Storage System) and PCS (Power Conditioning System) for the peak load shaving based on the load data in the substation of urban railway. In addition, this paper analyze the actual measurement of loads in the substation of urban railway. The load of a weekday in the substation of urban railway is high around rush hours in the morning and evening, which is different from that of a normal substation. The required capacities of ESS and PCS become larger as the amount of peak load shaving is higher, and are affected from the patterns of daily load in the substation.

• 전기전자학회논문지
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• 제23권2호
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• pp.350-357
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• 2019

본 연구에서는 전체 태양광발전소의 80%를 차지하고 있는 소규모 태양광발전소의 에너지저장장치 연계에 따른 시스템 효율을 분석하였다. 설치용량이 100kW인 태양광발전소의 데이터를 수집하고 각 발전소의 PCS와 배터리의 용량에 따른 ESS 효율의 상관관계를 도출하였으며 결론적으로 배터리의 방전속도에 영향을 미치는 C-Rate의 수치가 높을수록 ESS의 방전효율이 높아지는 것으로 나타난다.

• 한국전자통신학회논문지
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• 제14권2호
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• pp.351-360
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• 2019

최근 정부의 에너지 정책에 힘입어 ESS(: Energy Storage System) 설비가 증가하고 있으며 이로 인해 화재 폭발 등 다양한 사건사고가 발생하고 있다. 현재 ESS는 PMS(: Power Management System) 포함하여 모든 시스템이 현장에 설치되어있는 통합형 ESS로 구축되어 있다. 이 시스템은 사고 발생 시 산화되어 데이터의 부재 가능성이 매우 높을 뿐만 아니라 외부에 존재하는 관리자가 사고 발생 시 신속하게 대응할 방법이 없는 상황이다. 이에 본 논문에서는 별도의 WAS 및 데이터 스토리지 구축을 통해 기존 시스템에서의 주요 기능을 분리하여 외부에서 EMS(: Energy Management system) 운용이 가능함과 동시에 사고 발생 시 원인 및 신속한 대응이 가능한 독립형 PMS 개발을 제안하고자 한다.