• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.1
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• pp.27-34
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• 2014

The paper proposed a sizing method of an energy storage system(ESS) for peak shaving of high-speed railway substations based on load profile patterns of substations. A lithium based battery ESS was selected since it can produce high-power at high speed that peak shaving requires, and also takes up a relatively smaller space for installation. Adequate size of the ESS, minimum capacity which can technically meet a peak shaving target, was determined by collectively considering load patterns of a target substation, characteristics of the ESS to be installed, and optimal scheduling of the ESS. In case study, a local substation was considered to demonstrate the proposed sizing method. Also economic analysis with the determined size of ESS was performed to calculate electricity cost savings of the peak shaving ESS, and to offer pay-back period and return on investment.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.10
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• pp.1508-1516
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• 2015

This paper proposes the optimal operation of ESS (Energy Storage System) in the substation of urban railway in an economical point of view. Since the load patterns of urban railway have different characteristics with the general power demand pattern, the characteristics motivate us to develop the optimal operation algorithm for ESS under Korean electricity billing system. We also introduce two different ESS operation strategies for peak load shaving and electricity consumption charge minimization respectively, and formulate each scheme. Historical data from Namgwangju substation are used for economical comparison of the strategies. The results show that the proposed algorithm is the most cost-effective ESS operation scheme among the strategies and reduces around 5 percent of electric charges compared to the charge without ESS operation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.6
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• pp.905-910
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• 2017

As the development of BESS(Battery Energy Storage System), the application of BESS in load frequency control is considered as effective method. So, KEPCO(Korea Electric Power Corporation) have installed about 236MW ESS for GF(Govner Free) function from 2014. In this paper, we implemented Simulink Model for KEPCO GF ESS and analyzed one year historical operation data generated by Simulink model and actually measured frequency data. The operation results were divided into action for maintaining SOC and frequency. In addition, we also analyzed cycle life of GF ESS using two ESS cycle life model. We concluded the ESS cycle life models are not appropriate, because Most of the SOC swing in operation results are below 10%.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.583-584
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• 2015

Energy Storage System(ESS) can be used as several purposes such as uninterruptible power supply (UPS), frequency regulation, maximum load cut, and etc. This paper analyzes and simulates the reclosing operation in distribution system with ESS for frequency regulation and maximum load cut. To solve the effect from ESS, two sequences in reclosing process are added to conventional reclosing. The modelings and simulations of reclosing operation using EMTP/ATPDraw are performed.

• Journal of Hydrogen and New Energy
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• v.25 no.3
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• pp.311-318
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• 2014

Performance degradation of a battery in 20 kWh energy storage system (ESS) under various operating conditions was studied. And energy saving of the ESS was also monitored by connecting with 20 kW photovoltaic (PV). PV-connected ESS saved 5~7% of energy consumption in 2013 compared to that without such system in 2012. As charge-discharge cycle increased, capacity decreased and the performance degradation was glaringly obvious after 40 cycles. And as charge and discharge rate increased, the performance degradation was more serious. After 50 charge-discharge cycles, a lot of degraded product was deposited on the surface of anode and cathode electrodes, and the cathode side was more contaminated. Therefore, in order to maintain the cell performance, it was more important to protect the degradation of the cathode side.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.1
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• pp.11-18
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• 2015

This paper proposes a high-efficiency 3-kW hybrid ESS with emergency power supply. The proposed system enables efficient use of power from photovoltaic (PV) cells and energy storage system (ESS). The proposed system can operate as an uninterruptible power supply (UPS) when grid fault occurs, providing seamless transfer from grid-connected mode to stand-alone mode. The LLC converter for PV achieves ZVS turn-on of switches and ZCS turn-off of diodes, and the isolated bidirectional DC-DC converter for ESS achieves ZCS turn-off regardless of load condition, resulting in high efficiency. The efficiency and performance of the proposed hybrid ESS has been verified by a 3-kW prototype.

• Journal of Korea Society of Digital Industry and Information Management
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• v.12 no.2
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• pp.1-6
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• 2016

Several efforts to replace the use of existing fossil energy resources have already been made around the world. As a result, a new industry of renewable energy has been created, and efficient energy distribution and storage has been promoted intensively. Among the newly explored renewable energy sources, the most widely used one is solar energy generation, which has a high market potential. An energy storage system (ESS) is a system as required. In this paper, the design and implementation of an ESS for the efficient use of power in stand-alone street lights is presented. In current ESS applied to stand-alone street lights, either 12V~24V DC (from solar power) or 110V~220V AC (from commercial power) is used to recharge power in systems with lithium batteries. In this study, an ESS that can support both solar power and commercial power was designed and implemented; it can also perform emergency recharge of portable devices from solar powered street lights. This system can maximize the scalability of ESSes using lithium batteries with efficient energy conversion, with the advantage of being an eco-friendly technology. In a ripple effect, it can also be applied to smart grids, electric vehicles, and new, renewable storage markets where energy storage technology is required.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.7
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• pp.1125-1129
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• 2015

Increasing peak load is one of the major concerns about operation of urban railroad systems. Since ESSs (Energy Storage Systems) have a great potential for shaving the peak load, there has been a growing interest in the use of ESS for peak load reduction. Also, ESS can be optimally scheduled to minimize the electricity purchasing cost under a given ToU (Time-of-Use) tariff by taking advantage of electricity price difference between peak and off-peak time. This paper presents a Mixed Integer Programming (MIP)-based ESS scheduling method to minimize the electricity purchasing cost under a ToU tariff for an urban railroad system.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.473-474
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• 2013

In this paper, a power flow control of PV hybrid module system with ESS is proposed. Photovoltaic(PV) hybrid module system is consist of individual converter, central inverter, and energy storage system(ESS). Because PV power can be changed in particular hours and environment condition, the power management control for ESS is required. In this paper, the power flow control method for PV hybrid module system with ESS is proposed. The validity of proposed control method is verified by simulations and theoretical analysis.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.3
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• pp.266-275
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• 2014

This paper proposes the hybrid UPS(Uninterruptible Power Supply) with ESS(Energy Storage System) function. The proposed hybrid UPS is operating in four states, which are normal state, battery state, ESS state, and bypass state. In case of peak load time or power shortage, the system is operating in ESS state in which the stored energy of the battery is used to manage the power effectively. The validity of proposed system are verified by simulations and experiments.