• Journal of Electrical Engineering and Technology
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• v.6 no.2
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• pp.284-292
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• 2011

This paper presents a load-shedding scheme using the Talmud rule in islanded microgrid operation based on a multiagent system. Load shedding is an intentional load reduction to meet a power balance between supply and demand when supply shortages occur. The Talmud rule originating from the Talmud literature has been used in bankruptcy problems of finance, economics, and communications. This paper approaches the load-shedding problem as a bankruptcy problem. A load-shedding scheme is mathematically expressed based on the Talmud rule. For experiment of this approach, a multiagent system is constructed to operate test islanded microgrids autonomously. The suggested load-shedding scheme is tested on the test islanded microgrids based on the multiagent system. Results of the tests are discussed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.12
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• pp.84-90
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• 2010

In order to level electric power of the photovoltaic and wind-turbine system and ensure fast response of the fuel-cell and micro-turbine, the energy storage is required in the microgrid system. In this paper, a simplified simulation model of the battery energy storage for charging method with IUIa is developed using PSCAD/EMTDC. The model consists of e.m.f.(electromotive force), internal resistor and overvoltage capacitor. A method for deciding parameters of the model on a case-by-case basis is proposed. The developed model can be used in the simulation of a complicated system such as a microgrid system.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.4
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• pp.265-272
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• 2018

This paper proposes a new control method for the supercapacitor (SC) to compensate the pulsed load and to enhance the power quality of the DC microgrid. By coordinating the operating frequency, the SC is controlled to handle the surge current, while the low-frequency current component is dealt with by the remaining sources in the system. The operation mode of the SC unit is automatically changed based on the state of charge and DC bus voltage level. Meanwhile, the mismatch in the power demand is covered by the SC unit by regulating the DC bus voltage level. The effectiveness of the proposed method is verified experimentally by the prototype with two distributed generators and one SC unit.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.236-237
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• 2006

A microgrid is a new type of power system which is formed by the interconnection of small generator to distribution systems. Microgrids are able to supply electric power to their loads independently, which is called with islanding operation, even if they're separated from the power system. As a result, microgrids must be equipped with specific islanding detection schemes for the islanding operation of microgrids. This paper studies an islanding detection method considering reactive power. The proposed method is dealing with the reactive power of the cable which connects between a microgrid and a power system. To show the validity of the proposed method, many islanding operation cases are tested by varying the load conditions of microgrids.

• Journal of Power Electronics
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• v.16 no.2
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• pp.748-759
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• 2016

The microgrid concept is a promising approach for injecting clean, renewable, and reliable electricity into power systems. It can operate in both the grid-connected and the islanding mode. This paper addresses the two main challenges associated with the operation of a microgrid i.e. control and protection. A control strategy for inverter based distributed generation (DG) and an energy storage system (ESS) are proposed to control both the voltage and frequency during islanding operation. The protection scheme is proposed to protect the lines, DG and ESS. Further, the control scheme and the protection scheme are coordinated to avoid nuisance tripping of the DG, ESS and loads. The feasibility of the proposed method is verified by simulation and experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.5
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• pp.321-327
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• 2018

DC microgrid system composed of multiple converters has a tendency to make the system unstable due to the interaction of converters. To solve this problem, in this paper, the interaction between cascaded converters with LC input filter is analyzed with impedance modeling using g-parameter. The input impedance and the output impedance of the system can be obtained through this technique. The stability of the system can be determined by applying Middlebrook's stability criterion to the impedance. Virtual impedance is added to the controller to enhance stability. The validity of the analysis is verified by the result of several simulations and experiments.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.6
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• pp.727-737
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• 2014

This paper presents the design of Fuzzy PI controller that is used at BESS(Battery Energy Storage System) charging and discharging process for islanded operation in microgrid. Most of the PI controllers have fixed PI gains, but real-time updated gains are applied to PI controller using Fuzzy logic in this paper. The performances of suggested Fuzzy PI controller are simulated by PSCAD/EMTDC. As a result, output characteristics of ESS applied real-time updated gains to PI controller are faster than those of using fixed gains.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.620-630
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• 2018

In this paper, a positioning method of distributed power system is proposed to minimize the average voltage variation of a DC microgrid through voltage sensitivity analysis. The voltage sensitivity under a droop control depends on the position of the distributed power system. In order to acquire a precise voltage sensitivity under a droop control, we analyzed the power flow by introducing a droop bus with the considerations of the droop characteristics. The results of the positioning method are verified through PSCAD/EMTDC simulation.

• Proceedings of the KIPE Conference
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• 2019.11a
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• pp.180-181
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• 2019

This paper proposes a method for improving the power quality of PMSG-based wind energy conversion system based on model predictive control in DC Microgrid. The MPC has a fast dynamic response. However, a large torque ripple deteriorating power quality is generated by a large and fixed switching period. On the other hand, the proposed method improves the power quality by setting the sampling time having zero torque error. The validity of the proposed method is verified through PSIM simulation.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.04a
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• pp.461-463
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• 2016

Information security and preservation of customer's data privacy are key factors for further wide spread adoption of microgrid (MG) technology. However, strong coupling between the operation cost of multi-microgrid (MMG) system and privacy of customer data makes it more challenging. A nested energy management system (EMS) has been proposed in this paper. The surplus/shortage information from the inner level MGs is included in processing the optimal operation of outer level MGs. This type of optimization ensures a layered privacy-preservation to customer at each MG level. The proposed EMS architecture is a better trade-off architecture between the operation cost of the MMG system and customer privacy-preservation at each level of MG.